University of Groningen The use of biodegradable fixation

University of Groningen

The use of biodegradable fixation devices in the treatment of osteochondritis dissecans andosteochondral fracturesWouters, Diederick Bernard

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The use of Biodegradable Fixation Devices in the Treatmentof Osteochondritis Dissecans and Osteochondral Fractures:

Fiction, Future, Fact

ISBN: 978-90-367-4087-6

© 2009, D.B. WoutersNo parts of this thesis may be reproduced or transmitted in any forms or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system, without permission of the author

Lay-out: Peter van der Sijde, Groningen

Printed by: Drukkerij Van Denderen, Groningen

This thesis was eff ected with the support of: ffff

De Nederlandse Vereniging voor Traumatologie, Nederlandse Orthopaedische Vereniging, De Boering Stichting, Conmed-Linvatec, Biomet Nederland, Synthes bv, Stryker Nederland, Pro-Motion Medical, Tramedico, Orthin bv

RIJKSUNIVERSITEIT GRONINGEN



Proefschrift

ter verkrijging van het doctoraat in de Medische Wetenschappen

aan de Rijksuniversiteit Groningenop gezag van de

Rector Magnificus, dr. F. Zwarts,fiin het openbaar te verdedigen op

maandag 7 december 2009om 14.45 uur

door

DIEDERICK BERNARD WOUTERS

geboren op 26 april 1948te Djakarta

Promotores Prof. dr. R.R.M. Bos Prof. dr. J.Th.M. de Hosson Prof. dr. M.J.A. van Luyn

Beoordelingscommissie Prof. dr. S.K. Bulstra Prof. dr. P. Patka Prof dr. H. Weinans

for my children, Roderick, Philippine, Constantijn, Sebastiaan;

I’m so proud of each of you!

To Petra



Paranimfen: P.C.R. Wouters J. Lebbink

Contents

Chapter 1 Introduction and aims of the study 9

Chapter 2 The use of biodegradables in the treatment of osteochondritis 21 dissecans of the knee: fiction or future?fi

Acta Orth Belgica 2003;69(2):175–181

Chapter 3 Should in the treatment of Osteochondritis Dissecans biodegradable 31 or metallic fixation devices be used?fi A comparative study in goat knees.

J Biomed Mater Res B Appl Biomater. 2008;84(1):154–164

Chapter 4 The Meniscus Arrow® or metal screw for treatment of Osteochondritis 49 Dissecans? In Vitro comparison of their effectiveness. ffff

Knee Surg Sports Traumatol Arthrosc 2004;12: 52–57

Chapter 5 Will the hold of solid biodegradable implants be infl uenced by swelling 61fl during the degradation process?

An in-vitro study with Meniscus Arrows®.Knee Surg Sports Traumatol Arthrosc 2007; 15:1204 – 1209

Chapter 6 Is the pull-out force of the Meniscus Arrow® in bone affected 73ffff by the inward curling of the barbs during biodegradation? An in vitro study.

Med Sci Monit 2009;15(4):BR.95-8

Chapter 7 Pull out tests, comparing Meniscus Arrows® and Smart Nails®, 83 followed by a prospective series of fi ve clinical cases applyingfi Meniscus Arrows® as fi xation devices of osteochondral fragments infi the human knee.

submitted

Chapter 8 General discussion 97

Chapter 9 Conclusion and future perspectives 109

Chapter 10 Summary 113

Samenvatting in Dutch 119

Dankwoord in Dutch 127

Curriculum vitae 131

9

1CHAPTER

Introduction

10

Chapter 1

INTRODUCTION

Knee joint disorders in man may always have existed. However, the first known description of thefi

removal loose bodies from the knee joint is from Ambroise Paré in 1558.1 He described the procedure

as follows: “to open for him a washy effusion, from which he suffff ered in his knee, in which I found a ffff

loose body (stone) with the size of an almond, pale white, solid and polished. He healed and is still

living at the moment”. In a footnote Paré stated that “it is the fi rst known occasion that a loose bodyfi

developed in the knee and was extracted successfully through an incision”.

In the 18th and 19th century, several papers appeared about the origin of, what we call nowadays,

osteochondritis dissecans (OCD). Barth presented an extensive survey about the appearance of loose

bodies in 1898.2 He mentioned in this study several authors in this field like Monroe (1726), Reimar fi

(1770), Haller (1776), Breschet (1812), Laënnec (1813), Broca (1854).3 Klein (1864)4, Paget (1870)5,

Gies (1882)6, Poncet (1882)7, Pouillet and Vaillard (1885)8, Kragelund (1886)9 and König (1887).10

That the surgery in those times wasn’t always as successful as Paré has described is illustrated by

the paper of Klein. He mentions the death of a 37-years old male due to sepsis, six weeks after the

removal of a loose body from his knee.

In the 20th century hundreds of papers about OCD followed. An extensive survey was published in

a thesis by Bots in 1983.11

THE ORIGIN

Several theories about the origin of the osteochondral corpusculae in the knee joint have been

suggested throughout history, like direct and repetitive trauma, spontaneous appearance,

developmental disorders, arthrosis or ossifi cation disturbances, vascular impairment and hereditary fi

causes.

Trauma theory

Barth devided the group of loose bodies into two subgroups: soft and hard particles. The soft loose

bodies were believed to originate from the synovia during an infection of the joint. He believed

that the hard corpusculae developed either by arthritis or repetitive trauma. This last causality was

previously mentioned by other authors as well, starting with Monroe (1726), followed by Reimar

(1770), Haller (1776), and Breschet (1812), all cited by Barth.2 Another contemporary author,

Kragelund9 thought that nutritional disturbences produced sequestration of the particle (1886) due

to repetitive micotrauma. He noted that twelve out of thirty free bodies, found at autopsy, exhibited

the structure of the normal joint surface at one side.

König, in 1887, was the first author who named the clinical picture, in which small fragments of fi

bone, at one side covered with cartilage, originate from the femur condyle, OCD.10 He distinguished

repetitive microtraumata leading to subchondral necrosis from substantial local trauma and local

11

1

Introduction

contusion as causes of seqestration of free bodies in the joint. He believed that acute traction at

the cruciate ligaments could develop into an avulsion fracture out of the condyle as well, but that

rarely an arthritis, due to tuberculosis or another bacterial infection could lead to sequestration

of a particle or arthrosis. However, he stated that the most important, but unexplained cause was

spontaneous osteochondral fragment sequestration.

This was opposed by Barth2 and even more by Kappis.12 They were convinced that trauma could be

the only inducement to the formation of the free bodies in the knee.

The trauma theory was experimentally tested several times. A cartilage fragment was found to

resorb in most cases. Sometimes it accreted to the synovium,6,13 as did a cartilage-bone fragment

in the original defect as well as at the synovium.2,14,15,16,17 After an unstable accretion in its original

bed, a histological and radiological picture developed, surprisingly alike the appearance of a clinical

OCD.18,19,20 Experimental recurrent microtraumata could also produce subchondral fractures in a

later stage,17,21,22,23 sometimes developing into an OCD-like defect.24,25

According to Kennedy,26 a direct trauma (exogenous) and a rotary compression force (endogenous)

could produce osteochondral fractures like an OCD-like fragment as well. He created osteochondral

fragments applying a direct rotary compression force at cadaver knees. However, he could produce

only a few lesions and the osteochondral fracture pattern was widely variable.

Aichroth (20) stated, that, in case of an osteochondral fracture, instability could lead to a disturbed

fracture healing and an OCD-like lesion could develop.

Trillat27, however, pointed out, that a “fresh” osteochondral fracture with a bleeding surface is a

completely diff erent entity compared to an OCD with fiffff brous tissue between the bony surfaces.fi

Several theories of an indirect trauma as an inducement appeared throughout time. The medial spine

of the intercondylar eminence has been seen as the impacting pole into the medial condyle.28,28,30,31

Smillie32 noted a significant difffi erence between a higher medial spine of the intercondylar emineceffff

and the incidence of an OCD fragment of the medial femur condyle. However, this is contradicted by

ot her authors.33,34,35,36 The patella is also mentioned as a cause for the origin of an OCD fragment,12,37

this, however, could not be confi rmed by experiments.fi 37 Baumgartl suggested that the medial ridge

on a patella (type IV) could be responsible for the development of an OCD lesion.38 Finally, a torn

meniscus could, according to several authors,39 40,41,42 be seen as a cause of OCD develpopment. As

often in literature, contradicted by others.43,44 Exner witnessed the healing of an OCD fragment (a

“fresh” osteochondral fracture, probably a total diff erently behaving entity, DBW) after removal of affff

torn, discoid meniscus fragment, jammed between the fragment and its bed.45

Spontaneous origin

Broca (according to Barth2), observed three cases of loose bodies, post mortem in the knee. He

found them by chance,without signs of infection. Laënnec (1813) and Courtot (1879), also cited by

Barth,2 believed that cartilage fragments arose from the para-synovial tissue and questioned the

trauma theory.

12

Chapter 1

Paget5 stated in 1870, that the free corpusculae arose from a spontaneous ideopathic proces. König,

in 1887,10 was searching for an explanation but had none.

Arthrosis or arthritis

In France, Poncet7 and Pouillet and Vaillard8 supported the theory of arthrosis deformans as the

inducing factor leading to these loose bodies. This was also mentioned by Barth and König, as was

tuberculous osteomyelitis and arthritis, in their view both a cause of sequester formation.

Vascular impairment

In the following, 20th century, several other causes of sequestration of cartilage-bone fragments

in the knee appeared in the literature, like vascular impairment caused by small bacterial emboli

tuberculosis and emboli of clotted erythrocytes, as was stated by Axhausen13 and Watson Jones,46 or

avascular bone necrosis leading to a pseudarthrosis-like fragment as Bots47 and others48,49 described.

Developmental disorders

The disturbance of ossification of the distal femur as another potential source of OCD was elaboratedfi

in the last six decades of the 20th century. During childhood, different ossififfff cation patterns of thefi

distal femur are discernable, from almost round to oval with a smooth surface from 0 to 5 years to

square-pointed with irregularities starting at the age of fi ve years. These irregularities are found in fi

boys mostly until the 7th year, sometimes lasting until the 14th year. In girls, the occurrence is less

frequent and mostly between the 4th and the 7th year.50,51,52 The irregularities are more often medial

at the medial side and lateral in the lateral compartment of the knee. Accessorial bone nuclei are

also found between 3 – 13 years of age with varying expression of this phenomenon. In boys, they

are most frequently encountered between the 3rd and the 6th year, fi nally disappearing around the fi

age of 10 years. In girls they can be observed mostly until the 9th year. Only exceptionally these bone

nuclei are seen after this age.50,51,52,53,54,55,56

However, a relation with the occurrence of OCD is not convincingly proven up untill now.

Hereditary, constitutional causes or abnormalities in the endocrine status

Several authors described families in which multiple patients with OCD were found. However,

heredity as a potential factor for the development of OCD is not proven.32,42,57,58,59

In analogy, constitution was suggested to play a role in the development of OCD, though the

literature throughout time reveals contradictions. Rahm postulated in 1934 that pycnicity could be a

factor.60 In 1941 Howald mentioned dystrophia adipositas genitalis or dwarfismfi 61 and Smillie stated

in 1960, that patients with an OCD lesion were smaller or taller than the average person of their

age.32 Aichroth, in contrast, suggested in 1971 that an athletical posture could contribute to the

origin of osteochondritis dissecans.20

Endrocrinic disorders were either excluded nor proven as a causality. Hypothreoidy was described in

13

1

Introduction

relation with OCD62,63 and an experiment is described in dogs, in which OCD-like defects developed

during overloading their legs under treatment with a somatotropic and thyreoid hormone.64

Intra-articular injection of corticosteroids could induce the formation of an OCD fragment as well,

as Milgram stated.65

A lipid metabolism disturbance was found by Zsernaviczky in five patients with an OCD lesion.fi 66

Reviewing the above mentioned causes, none of them is convincingly proven. Up until now, the

only conclusion that can be made, is that the origin of OCD, almost for shure, is multifactorial.

Osteochondrosis or osteochondritis dissecans

The term osteochondrosis dissecans has been used instead of Osteochondritis Dissecans in several

papers and mostly in the German language, probably to differentiate between an infectious and affff

spontaneous origin but, after all, meaning the same disease.3,11,14,17,19,20,21,22,23

THERAPY

OCD should be regarded at as a pseudarthrosis,20,32,67,68,69,70,71 requiring optimal circumstances, like

stable fixation under compression and revascularisation measures to promote healing.fi

However, for centuries, the first therapy was only removal of the fragment, leaving the defect in fi

the condyle untreated. Though favourable results were reported,72,73 opposing papers, however,

showed progressive deterioration of the clinical status of the knee of the patients.74–79

Evolution of the surgical procedures opened the way for more invasive, reconstructing, surgery.

Nowadays, reposition and fixation is generally accepted as being the therapy of choice, if the fi

particle is viable and not fragmented.20,32,69,80–98

Metallic devices, like pins81 and Kirschner wires82,83 have been used for this purpose.

Pins, regardless the material they are made of, do not apply compression between the fragment and

the recipient bone.

Staples give compression, but can gradually protrude or break, requiring removal after all.84 Screws

produce compression as well.85,86,87,88,89,90 However, due to their larger minimal diameter, screws

induce more damage to the fragment than pins or staples. Moreover, at least two screws have to be

used to achieve rotational stability.

For several reasons most of the metallic devices have to be removed during second surgery after

consolidation of the fragment. If left in place, erosion of the opposite cartilage surface occurs sooner

or later.84,85,86,87,88 Although deeply imbedded, the implants can still gradually protrude through the

cartilage surface and have to be removed after all.84,91 They can also interfere with future imaging

like Computer Tomography (CT) or Magnetic Resonance Imaging (MRI) and radiation therapy.92,93

Some metals, such as chromium, nickel, gold, platinum and cobalt could, theoratically, evoke allergic

reactions like eczema or, if implanted in large amounts, anaphylactic reactions. Finally, chromium,

14

Chapter 1

nickel and cobalt are also potent carcinogens in animals.94

Biological or biodegrable devices lack most of the aforementioned disadvantages.

Sticks or pins, made out of bone, harvested from the patient have been successfully applied.95,96

This procedure, however, increases the operation time and morbidity without additional advantage

above biodegradable pins, and both osseous and biodegradable pins cannot produce the required

compression.

Osteochondral plugs are employed as fi xation devices as well, However, donor site morbidity, the fi

absence of producing substantial compression and failure of the re-integration process at the

interface of donor and recipient cartilage make this procedure less than optimal.97,98

In the last four decades, three biodegradable polyesters of the alpha-hydroxy carboxylic acid group,

polydioxanon, polyglycolic acid and polylactic acid have been applied in humans.

The mechanical properties of the diff erent biodegradable polymers diffffff er widely, from a sheerffff

strength of 179 – 250 MPa for self-reinforced polyglycolide (PGA) rods, to 92 MPa for polydioxanone

pins.99 This is one of the reasons that devices, made of polydioxanone and larger than pins or

sutures, have only been applied experimentally.100,101

Homo- and co-polymer polymers of polylactic and polyglycolic acid and their blends were

developed to achieve optimal characteristics in terms of mechanical properties and biodegradation.

Nevertheless, tissue reactions like cavity formation or reactive synovitis have been described after

the use of pins, screws or plates composed of several of these materials.102,103,104,105

The combination of one metallic screw (head diameter 3.5mm, cross-section suface 9.76mm2,

core diameter 2.7mm, cross-section surface 5.73mm2) and two smaller biodegradable pins with a

diameter of 1.5mm, cross-section suface 1.77mm2) results in a compressive (the screw) and rotational

stable (two pins) fixation, producing less damage than two screws and without the necessity of a fi

second, device removal, intervention.

In view of this concept, during a clinical study in OCD disease, the fragment was successfully fixed fi

in patients with a centrally placed metallic screw, producing compression and biodegradable pins,

providing rotatory stability. However, the screw had to be removed before loading the operated

knee.

There is no ideal treatment of OCD yet.

The Aims of this thesis were

1. To analyse the present treatment possibilities of osteochondritis dissecans (OCD), using

biodegradable fixation devices, making a second, implant removal, intervention unnecessaryfi

(chapter 2).

2. To study the biological behaviour and the eff ectiveness of a compressive and rotary stableffff

fixation of a standardized osteochondral fragment with one screw and two pins (chapter 3).fi

3. To evaluate the applicability of Meniscus Arrows® originally designed to mend ruptured

15

1

Introduction

menisci, Smart Nails® as fi xation device in the perspective of the application as fifi xation devicesfi

in the treatment of osteochondritis dissecans and osteochondral fractures (chapter 4).

4. To evaluate the clinical application of the Meniscus Arrows® as biodegradable devices for an

osteochondral fragment fixation in two patients with OCD of their femur condyle and in threefi

patients with an osteochondral fracture after comparative pull-out tests with Smart Nails®

(chapter 7).

bulging OCD

Examples of OCD or Osteochondral fractures:

partly detached OCD

Osteochondral fracture, the origin and the fragment elsewhere in the knee joint(see for color image: page 137)

16

Chapter 1

Literature:

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4. Klein H . Zur Geschichte der Entstehung der Gelenkmäuse. Virchov’s Arch 1864;29:190

5. Paget J. On the production of some of the loose bodies in the joints. St. Bartholom Hosp Reports. 1870;6:

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17

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18

Chapter 1

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70. Bots RAA. De operatieve behandeling van de osteochondrosis dissecans van de distale femurepifyse. Thesis. University of Nijmegen, the Netherlands 1983; p39–40

71. Wagner H. Operatieve Behandlung der Osteochondrosis dissecans des Kniegelengkes. Z orthop 1964;98: 333–355

72. Aglietti P, Ciardullo A, Giron F, Ponteggia F. Results of arthroscopic excision of the fragment in the treatmentof osteochondritis dissecans of the knee. Arthroscopy 2001;17(7):741–746

73. Uematsu K, Habata T, Hasegawa Y, Hattori K, Kasanami R, Takakura Y, Fujisawa Y. Osteochondritis dissecansof the knee: long-term results of excision of the osteochondral fragment. Knee 2005;12(3):205–208

74. Outerbridge RE. Osteochondritis of the posterior femoral condyle. Clin Orthop Relat Res 1983;175:121–129

75. Twyman RS, Desai K, Aichroth PM. Osteochondritis of the knee. A long term study. J Bone Joint Surg1991;73(3): 461–464

76. Murray JR, Chitnavis J, Dixon P, Hogan NA, Parker G, Parish EN, Cross MJ. Osteochondritis dissecans of theknee; long-term clinical outcome following arthroscopic debridement. Knee 2007;14(2):94–98

77. Anderson AF, Pagnani MJ. Osteochondritis of the femoral condyles. Long-term results of excision of thefragment. Am J Sports Med 1997;25(6):830–834

78. Wright RW, McLean M, Matava MJ, Shively RA. Osteochondritis dissecans of the knee: long-term results of excision of the fragment. Clin Orth Relat Res 2004;424:239–243

79. Gudas R, Kunigiskis G, Kalesinskas RJ. Long-term follow-up of osteochondritis dissecans. Medicina (Kaunas) 2002:38(3):284–288

80. Bandi W, Allgöwer M. Zur Therapie der Osteochondritis Dissecans. Helv Chir Acta 1959;26: 552–558

81. Smillie IS. Treatment of osteochondritis dissecans. J Bone Joint Surg 1957;39(B):248–260

82. Anderson A, Lipscomb AB, Coulam C. Antegrade curettement, bone grafting and pinning of osteochondritisdissecans in the skeletally mature knee. Am J Sports Med 1990;18(3): 254–261

83. Guhl JF. Arthroscopic treatment of Osteochondritis Dissecans. Clin Orth 1982;167: 65–74

19

1

Introduction

84. Kivistö R, Pasanen L, Leppilahti J, Jalovaara P. Arthroscopic repair of osteochondritis dissecans of the femoral condyles with metal staple fixation: a report of 28 cases. Knee Surg Sports traumatol Arthroscfi2002;10:305–309

85. Cugat R, Garcia M, Cusco X, Monllau JC, Vilaro J, Juan X, Ruiz-Cotorro A. Osteochondritis Dissecans: Ahistorical Review and its Treatment with cannulated screws. Arthroscopy 1993;9(6):675–684

86. Wagner H. Die Kliniek der Knorpeltransplantation bei der Osteochondrosis dissecans. Hefte zur Unfallheilkunde 1976;127:118–125

87. Gschwend N, Munzinger U, Löhr J. Unsere extraarticuläre Dissecatverschraubung bei Osteochondrosis dissecans des Kniegelenkes. Orthopäde 1981;10:83–86

88. Johnson LL, Uitvlugt G, Austin MD, Detrisac DA, Johnson CJ. Osteochondritis Dissecans of the Knee: Arthroscopic Compression Screw Fixation. Arthroscopy 1990;6(3):179–189

89. Mackie IG, Pemberton DJ, Maheson M. Arthroscopic use of the Herbert screw in osteochondritis dissecans. J Bone Joint Surg 1990;72B:1076

90. Rey Zuniga JJ, Sagastibelza J, Lopez Blasco JJ, Martinez Grande M. Arthroscopic use of the Herbert screw in osteochondritis dissecans of the knee. Arthroscopy 1993; 9(6),668–670

91. Bobic V. Cover photograph, Arthroscopy 2001;17(5)

92. Scher N, Poe D, Kuchmir F, Reft C, Weichselbaum R, Panje WR. Radiotherapy of the resected mandible following stainless steel plate fi xation. Laryngoscope 1988;98:561–563fi

93. Castillo MH, Button TM, Homs MI, Pruett CW, Doerr R. Effects of radiation therapy on mandibular ffffreconstruction plates. In: Trans 41st Ann Cancer Symp. The Society of Surgical Oncology, New Orleans,Louisiana, U.S.A.. 1988; p144

94. Black J. Orthopedic Biomaterials in Research and Practice. Churchill Livingstone New York, Edinburgh London, Melbourne. 1988;p292–302

95. Johnson, EW and Mc Leod TL. Osteochondral Fragments of the Distal End of the Femur Fixed with Bone Pegs. J Bone Joint Surg 1997;59A: 677–679

96. Bots RAA. De operatieve behandeling van de osteochondrosis dissecans van de distale femurepifyse. Thesis. University of Nijmegen, the Netherlands 1983;p70–72

97. Miura K, Ishibashi Y, Tsuda E, Sato H, Toh S. Results of arthoscopic fixation of Osteochondritis dissecans filesion of the knee with cylindrical autogenous osteochondral plugs. Am J Sports Med 2007;35(2):216–222

98. Kobayashi T, Fujikawa K, Oohashi M. Surgical fixation of MA’ssive osteochondritis Dissecans lesion usingficylindrical osteochondral plugs. Arthroscopy 2004;20(9):981–986

99. Hirvensalo E. Absorbable synthetic self-reinforced polymer rods in the fixation of fractures and osteotomies. fi1990 Thesis University of Helsinki Finland. p10–11

100. Iizuka T, Mikkonen P, Paukku P, Lindqvist C. Reconstruction of orbital fl oor with polydioxanone plate. Int JflOral Maxillofac Surg 1991;20:83–87

101. Ewers R, Förster H. Resorbierbare Osteosynthesematerialien. Eine tierexperimentelle Studie. Dtsch Z Mund Kiefer Gesichts Chir 1985;9:196–201

102. Bergsma EJ, de Bruijn WC, Rozema FR, Bos RRM, Boering G. Late degradation tissue response to poly(L-lactide) bone plates and screws. Biomaterials. 1995;16(1):25–32

103. Böstman O, Hirvensalo E, Mäkinen J, Rokkanen P. Foreign-body Reactions to Fracture Fixation Implants of Biodegradable Synthetic Polymers. J Bone Joint Surg 1990;72B:592–596

104. Friden Th, Rydholm U. Severe aseptic synovitis of the knee after biodegradable internal fixation. ActafiOrtho Scand 1992;63(1):94 – 97, 105. Barford G, Svensen RN. Synovitis of the knee after intraarticularfracture fi xation with Biofifi x. Acta Orthop Scand 1992;63(6):680–681fi

20

21

2CHAPTER

The use of Biodegradables in the Treatment of Osteochondritis Dissecans of the Knee:

Fiction or Future?

D.B. Wouters1,3

J.R. van Horn2

R.R.M. Bos3

1 Department of General and Arthroscopic Surgery and Traumatology, TweeSteden Hospital, Tilburg, The Netherlands,2 Department of Orthopaedic Surgery, University Hospital, Groningen, the Netherlands,3 Department of Oral and Maxillofacial Surgery, University Medical Centre Groningen, The Netherlands.

Acta Orthop Belg 2003; 69 (2):175-81

22

Chapter 2

The use of biodegradable fixation devices in the ope rative treatment of osteochondritis dissecans of fi

the knee could avoid a second operation for removal of the hardware, but what are the disadvantages?

Seven osteochondritis dissecans lesions, non-dis placed in four adult knees and in one adolescent

knee and displaced in two knees of adolescents, were tre ated by drilling and stabilization with

biodegradable pins, resulting in primary consolidation in the five non-displaced lesions and failure fi

in the two detached lesions. However, two detached fragments in adults, primarily fixed with onefi

metallic compression screw and three biodegradable pins both consolidated. In another adult

patient, the fi xation with two compres sion screws failed. A study of the available literature and thefi

results of our limited experience seem to indicate that the primary operative treatment of choice

of a non-detached osteochondritis dissecans lesion is drilling and fixation with biodegradablefi

pins. However, if this regimen fails or in patients with a detached lesion, one metallic screw and

a few addi tional biodegradable pins appear to constitute the best method of fixation. The use of fi

biodegradable screws is still hazardous, because of the long degra dation time and subsequent risk

of erosion of the opposite cartilage and tissue reaction. Other resurfacing options are available for

failures or fragmented or non-vital lesions.

INTRODUCTION

Fixation of the detached fragment, if it is vital and intact, is the best option in the treatment of

osteochondritis dissecans (OCD) of the knee, espe cially in adults.4, 6, 19, 27, 34, 47 Removal of the fragment

increases the risk of early osteoarthritis.2, 4, 27, 33, 47 Metallic fi xation devices such as pins or K-wires,fi 4, 27,

34, 47 hooks,38, 46, 49 stap les31 and screws are being used,6, 19, 26, 30, 35, 38, 44 all, however, with implant-related

disadvanta ges. Most of them have to be removed during a second operation. If they are left in place,

they may erode the opposite cartilage of the tibial plateau or they may break31 and they may also

disturb sub sequent diagnostic procedures such as computed tomography or magnetic resonance

imaging. Some metals like chromium, nickel, gold, platinum and cobalt may evoke allergic reactions

varying from eczema to anaphylactic shock. Finally, chromium, nickel and cobalt are also potent

carcinogens in animals.12 These disadvantages stimulated the application of biodegradable devices,

such as pins18, 37, 42 bone pegs5,6 glue,20,40 bone cylin ders,11 tags36 or screws.23 Unfortunately, pegs,

bone cylinders, tags, pins, and glue have poor mechanical properties and have a poor ability to

provide suffi cient compression between the fragments and stability. Screws, on the other hand, mayffi

erode the opposite cartilage surface due to their long degradation time and their dimensions.23, 32

The aim of this paper is to present the results of the use of biodegradable (bd.) pins in a series of

patients and to evaluate the presently available biodegradable devices for fragment fixation in the fi

treatment of OCD of the knee.

23

2

The use of Biodegradables in the Treatment of Osteochondritis Dissecans of the Knee: Fiction or Future?

PATIENTS AND METHODS

From 1989 till 1998, 10 knees in nine patients (six adults, two females and seven males) were

operated on for a symptomatic OCD lesion (Table I). The average age at operation was 24 years,

with a range from 14 to 33 years. The right knee was involved in six patients, the left knee in four

patients. A1l lesions except one were located on the medial femoral condyle. The lesion was still

attached in five cases (Figure I), it was partially deta ched and connected to the condyle by a bridgefi

of carti lage in four cases (Figure 2). In one patient (# 3) the frag ment was completely detached.

The size of the frag ments ranged from 0.8 to 3.6cm2. All patients complai ned of pain, effusion and ff

sometimes of locking, cracking or the sensation of a loose body. The onset of the symp toms varied

from three weeks to eight years before the operation, starting intermittently and getting worse and

more frequent over time. One patient (# 3) had an acute event, twisting his knee, after three weeks

of vague pain (Table 1). Two diff erent treatment strategies were applied, depending on the statusffff

Figure 1. Bulging cartilage of a non-detached OCD lesion in the medial compartment of a right knee. A test probe is seen at the bottom

Nr Sex Age at op. Med/Lat Side State Size (mm) Complaints Since1.1 f 15 yr lat. left detached 15 x 12 pain, eff usion, locking 4 yearsff1.2 19 yr med. right attached 15 x 15 pain 6 weeks2 m 16 yr med. right attached 15 x 15 pain, eff usion 3 yearsff3 m 14 jr med. right detached 20 x 15 pain, effusion 3 weeksff4 m 28 yr med. left attached 18 x 15 (night) pain, locking 6 years5 m 26 yr med. right detached 20 x 15 pain, eff usion, locking 8 yearsff6 m 25 yr med. right attached 20 x 15 effusion, cracking 3 weeksff7 f 24 yr med. right detached 20 x 12 pain, eff usion, locking 1 yearff8 m 23 yr med. left attached 20 x 12 (rotatory) pain, effusion 3 weeksff9 m 33 yr med. left detached 20 x 15 pain, eff usion, locking 10 yearsff

Table 1.

24

Chapter 2

of the fragment. The fi rst strate gy was arthroscopic drilling for revascularization and fifi xation withfi

biodegradable pins (Figure 3), with a diameter of 1.5mm (Orthosorb®, DePuy, Johnson & Johnson,

Warsaw, Ind., U.S.A.). The indication for the first regi men, applied seven times, was adolescent age or fi

incom plete detachment of the fragment. In one patient from the first group, a two screw-fifi xation andfi

minced autolo gous cancellous bone transplantation was used seconda rily, after fixation with pinsfi

had failed (patient # 3). The second strategy, used in three cases, was abrasion, minced autologous

cance1lousbone transplantation and meta1lic compression screw fixation. The indication was fi

skeletal maturity or detachment of the fragment. In two patients (#5 and # 9) in this second group,

one centrally placed metallic screw, providing compression, was combined with biodegradable

pins, providing rota tional stability (Figure 4). First, arthroscopic debridement was performed using

a saline solution as irrigation fluid. Subsequently the joint was temporarily fifl lled with COfi 2 gas during

Figure 3. An OCD lesion, fixed with (blue) biodegradable pins, some blood is fioozing out of thedrill holes. (see for color image: page 137)

Figure 2. A partly detached OCD lesion, pushed away by a probe.

25

2


Figure 4. One screw and 2 biodegradable (blue) pins, 6 weeks after implan-tation. A thin layer of newly grown cartilage is covering a substan-tial part of the head of the screw. (see for color image: page 137)

the arthroscopic insertion of cancellous bone. This prevented the minced bone to be fl ushed away. fl

In one patient in this second group (patient # 7), two screws were used primarily for fixation of fi

the fragment, owing to its large size (Figure 5). Postoperatively all knees were immobilized for two

weeks in a pIaster splint, followed by a hinged brace for three weeks. Continuous passive motion was

applied during this period. Patients from group 1 started weight bearing about six weeks postope-

ratively, after radiological confirmation of the healing process. Patients treated with screws startedfi

progressive loading immediately after screw removal, 8 to 12 weeks after insertion. The follow-up

time was between fi ve and 12 years with an average of nine years (Table 2).fi

Nr Sex Age Implant Complications Secondary treatment Result FU

1 f 15 4 pins (A) no consolidation perichondrium transplantation (O) healing 12 yr19 4 pins (A) no healing 8 yr

2 m 16 5 pins (A) consolidation, eff usion, painff

2 x drilling, shaving (A)healing 11 yr

3 m 14 4 pins (A) non union in6 weeks

cancellous bone transplantation2 compression screws (O) healing 11 yr

4 m 28 6 pins (A) no healing 10 yr5 m 26 1 screw

3 pins (A)cartilage fraying adhesion

shaving at screw removal (A)repeat shaving (A) healing 8 yr

6 m 25 5 pins (A) no healing 8 yr7 f 24 2 screws (A) no consolidation perichondrium transplantation (O) healing 7 yr8 m 23 5 pins (A) no healing 6 yr9 m 33 1 screw

3 pins (A)no

healing 5 yr

A: arthroscopic procedureO: open procedure

Table 2. Treatment and result

26

Chapter 2

RESULTS

Primary healing occurred in all five knees with non-displaced fragments, drilled and fifi xed with pins fi

only (Table II). In one of the knees with a par tially detached lesion, re-fracture or insufficient healingffi

led to dislocation of the fragment during a squatting movement (patient # 1, first knee), threefi

months after the first operation. After fragment remofi val and drilling of the bottom of the defect

during a second procedure, pain and joint effusion persisted for six months. In a third procedure, ff

perichondrium transplantation was performed and the symptoms disappeared. In the adolescent

patient # 3, the totally disloca ted fragment was replaced and fi xed with four bio degradable pins. No fi

healing was seen on the radio graphs after eight weeks. During control arthrosco py the fragment

was found to be mobile. To create optimal conditions for healing, the fragment was lifted, the

fibrous bed was abraded and cancellous bone transplantafi tion was performed, which was followed

by fixation of the fragment with two compres sion screws. Healing occurred in six weeks. In a third fi

patient (# 2) in the pin fixation group, the knee showed a persisting slight efffi usion and vague pain, ff

although the fragment healed radiologically. After two additiona1 arthroscopic debridements with

drilling of the irregular margins of the frag ment, the complaints vanished.

Primary healing occurred in both patients (# 5 and #9) in which one screw and three biodegradable

pins were used. In one patient (# 7), initia1fi xa tion with two screws failed. Subsequently the fragment fi

was removed and the crater was drilled. Pain and a slight effusion persisted. After perichondri umff

transplantation she became free of complaints as well.

Figure 5. Two screws, arthroscopically inserted, to fix an OCD lesion. fi(see for color image: page 138)

27

2


DISCUSSION

As early as 1558, more than 500 years ago, Paré described the removal of loose bodies from a knee

joint, probably the first paper about the treatment of an OCD patient.fi 39 However, more than four

cen turies later the origin of OCD of the knee is still unexplained and the treatment still not uniform.

The behavior of OCD closely resemb1es pseu darthrosis,6,47 but no consensus exists about the

treatment of choice.

In adolescents spontaneous healing was believed for a long time to be the natural course of OCD21,

25,33,43 and treatment was conservative. However, failures of this regime became evidentI,3,17,24,33 and

allthough spontaneous healing did sometimes occur, the outcome was unpredictable. More recently

operative treatment, such as drilling, has been advocated in the literature.I,3,17,24,47 In the adult, simple

removal of the fragment proved to be as unpredictable as in the growing individuals, with even

worse results. Repositioning of the original fragment, if intact, is more and more con sidered to be

the treatment of choice.4,6,19,27,47 To optimize the conditions for healing, curettage or abrasion of the

bed, cancellous bone transplanta tion and fixation with compression is advocated.fi 4,19,26,27,34,38 Most

of the metallic fi xation devi ces have to be removed during a second opera tion.fi 2,4,19,26,27,30,34,38,46,47,49

Staples, if left in place, tend to break (9 out of 28 patients) and consolidation only occurred in 15 out

of 28 of the patients in one series.29 Obviously staples do not provide a stable, compressive fixationfi

like a screw. Herbert screws and Smillie pins could be left in place as well, but can still cause erosion

by shed ding on the long run.14,47 Furthermore, they can disturb subsequent MRI and CT imaging

and, fin ally, they carry the risk of allergic reactions and have a carcinogenic potential.fi 12

The use of biodegradable devices could possibly solve these problems. However, screws, with their

large cross-section compared with pins, produce considerable holes in the often tiny fragments and

may cause erosion of the opposing cartilage.23,32 In contrast, the more delicate biodegradable pins

cannot achieve absolute stability and compression. In the adolescent, with a more favorable prog-

nosis due to a higher natural tendency to healing, only drilling is advocated in the literature, if the

fragment is not fully dislocated. Stabilization with small biodegradable pins can provide additional

stability in this situation, as was successfully done in patient #2 with a bulging, not detached lesion.

If the fragment is partially or totally detached, some fi xation is mandatory. In our series, simplefi

pinning failed in the patient with the totally dislocated frag ment (#3) and in the patient (# 1, 1) with

subtotal detachment of the fragment. This situation in ado lescents seems to be an indication for

primary compressive fixation as well, as was done in thefi second operation in patient #3 and in the

adult patients.

In the adult with the detached lesion, the current treatment of choice of OCD of the knee is stable

fixation with compression after debridement of the bed and cancellous bone transplantation.fi

One metal compression screw fi xes the fragment under compression. Surrounding the screw by afi

few biodegradable pins instead of inserting another screw improves rotational stability. With one

2.7mm screw and three Orthosorb® pins with a diameter of 1.5mm, the damage caused to the often

28

Chapter 2

tiny fragment is more diff use and less than with two more bulky screws. The arthroscopic insertion ff

of a metallic screw and its removal, after healing of the fragment, is likely to be less harmful than the

use of a biodegradable screw, because the latter may cause erosion of the opposite cartilage surface

due to the long degradation time, as it is not imbedded.23,32 Whereas polymerized poly (L-lactide)

takes more than six years to be absorbed9, semi crystalline poly (96L/4D) lactide (PLA96) and the,

initially, amorphous poly (50L/50D)lactide (PLA50/50) take considerably shorter, ranging from more

than 101 weeks (80 mg PLA96) to 32 weeks (80 mg material, PLA50/50).10 Small polyglycolic acid rods

were found to dissolve within 12 weeks in rab bit femurs. Subsequently, this material was applied

to fracture fixation in humans, leading to tissue reactions as well.fi 15 Rods made of blends such as

polyglycolic -polylactic acid (PGAPLA) were also used in humans.45 Thus, in spite of all the research

carried out up until now, all the above mentioned materials may still cause serious tissue reactions,

when implanted subcutaneously, intra-articularily or in bone,7,9,10,15,16,22,45 depending on the place

and the type and amount of the material.48 In addition, the resorption still takes such a long time

that the implants, larger than small pins, may cause undesi red wear of the opposite cartilage. Unless

other materials are developed, they should not be used. If the refi xation procedure eventually fails, fi

several resurfacing procedures can be performed, such as perichondrium transplantation,29 mosaic

p la sty,28 an Osteochondral Auto Transplantation System procedure13 or cultured chondrocyte

implantation.8,41 However, these procedures have their own disadvantages such as calcifications infi

the transplant or swelling and failure because of loosening and necrosis of the implants and should

be regarded as a last resort. They are only indicated if the original fragment is too fragmented or

not viable.

CONCLUSION

The study of the available literature and the results in our small series do not allow for a statistical

analysis of the results of the different treatments of OCD, ffff but do suggest that the optimal treatment

of the non-detached juvenile OCD lesion (i.e. before closure of the physes) consists of arthroscopic

dril ling and fixation with a few biodegradable pins in order to add supplemental stability. Whenfi

the frag ment is dislocated, the situation equals to the dis placed adult OCD lesion and replacement

of the fragment and fi xation under compression, after thorough debridement of the bed and fi

transplanta tion of cancellous bone, currently seems to be the treatment of choice. Insertion

of one metallic screw and a few biodegradable pins with a small diameter achieve compression

and rotational stability, and causes less damage to the fragment than two screws. The screw has

to be removed before loa ding the joint, in order to prevent erosions of the opposite cartilage

surface. Biodegradable screws should rather not be used, because of the current implant-related

disadvantages. Performing the procedure arthroscopically diminishes the additional trauma to the

knee. If radiological healing occurs, but complaints persist, re-arthroscopy should be performed to

debride residual cartilage irregulari ties, responsible for the symptoms.

29

2


1. Aglietti P, Buzzi R, Bassi PB, Fioriti M. Arthroscopic drilling in juvenile osteochondritis dissecans of themedial femoral condyle. Arthroscopy 1994;10:286-291

2. Aichroth P. Osteochondritis dissecans of the knee. A cli nical study. J Bone Joint Surg 1971; 53-B:440-447

3. Anderson AF, Richards DB, Pagnani MJ, Hovis WD. Antegrade drilling for osteochondritis dissecans of theknee. Arthroscopy 1977;13:319-324

4. Anderson A, Lipscomb AB, Coulam C. Antegrade curet tement, bone grafting and pinning of osteochondritisdis secans in the skeletally mature knee. Am J Sports Med 1990;18:254-261

5. Arq M. Behandlung der Osteochondrosis Dissecans durch Knochenspanbolzung. Arch Orthop Unfall-Chir 1974;79:297-312

6. Bandi W, AlIgöwer M. Zur Therapie der Osteochondritis Dissecans. Helv Chir Acta 1959;5:552-558

7. Barford G, Svensen RN. Synovitis of the knee after intra articular fracture fixation with Biofifi x. Acta Orthop fiScand 1992;63:680-681

8. Behrens P, Ehlers EM, Köchermann KU, Rohwedel J, Russlies M, Plötz W. Neues Therapieverfahren für lokali-sierte Knorpeldefekte. Fortschr der Med 1999;141:49-51

9. Bergsma JE, Rozerna FR, Bos RRM, de Bruijn WC. Foreign body reactions to resorbable poly(L-lactide) boneplates and screws used for the fi xation of unstable zygo matic fractures. J Oral Maxillofac Surg 1993;51:666fi670

10. Bergsma JE, Rozerna FR, Bos RRM, Joziasse CAP, Boering G. In vivo degradation study of poly (50L/50D-lactide) and poly (96L/4D-lactide). A pilot study. Thesis. University of Groningen, the Netherlands 1995,pp 127 -136

11. Berlet GC, MA’scia A, Miniaci A. Treatment of unstable osteochondritis dissecans lesions of the knee using autoge nous osteochondral grafts (mosaic plasty). Arthroscopy 1999;15(3):312-316

12. Black J. Orthopedic Biomaterials in Research and Practi ce. Churchill Livingstone New York, 1988; pp 292-302

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14. Bobic V. Cover photograph, Arthroscopy 2001;17

15. Böstman 0, Hirvensalo E, Vainionpää S, Vihtonen K, Törmälä P, Rokkanen P. Degradable polyglycolic rods for the internal fi xation of displaced bimalleolar fractures. Int Orthop (SICOT) 1990;14:1-8fi

16. Böstman O, Päivärinta U, Manninen M, Rokkanen P. Polymeric debris from absorbable polyglycolide screws and pins. Acta Orthop Scand 1992;63:555-559

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19. Cugat R, Garcia M, Cusco X et al. Osteochondritis dis secans: a historical review and its treatment withcannula ted screws. Arthroscopy 1993;9:675-684

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22. Friden T, Rydholm U. Severe aseptic synovitis of the knee after biodegradable internal fixation. Acta OrthopfiScand 1992;63:94-97

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Chapter 2

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37. Matsusue Y, Nakamura T, Suzuki S, Iwasaki R. Biodegradable pin fi xation of osteochondral fragments of thefiknee. Clin Orthop 1996;322:166-173

38. Müller W. Osteochondrosis dissecans (Diagnose und Therapie). Hefte ZurUnfallheilkllnde 1976;127:93-102

39. Paré A. Œuvres Complètes. 1841; Tome III, p 32, J.B. Baillière, Paris

40. Passl R, Plenk H. Ueber die Einheilung replantierter chondraler Fragmente. Unfallchirurgie 1986;12:194 199

41. Peterson L, Brittberg M, Kiviranta I, Lundgren Åker lund E, Lindahl A. Autologous chondrocyte transplanta-tion; biomechanics and long-term durability. Am J Sports Med 2002; 30:2-12

42. Plaga BR, Royster RM, Donigian AM, Wright GB, Caskey PM. Fixation of osteochondral fractures in rabbitknees. J Bone Joint Surg 1992;74-B:292-296

43. Rehbein F. Die Entstehung der Osteochondritis Dissecans. Langebecks Arch Klin Chir 1950;265:69-114

44. Rey Zuniga JJ, Sagastibelza J, Lopez Blasco JJ, Martinez Grande M. Arthroscopic use of the Herbert screw in osteochondritis dissecans of the knee. Arthros copy 1993;9:668-670

45. Rokkanen P, Vainionpää S, Törmälä P et al. Bio degradable implants in fracture fi xation: early results of fitreatment of fractures of the ankle. Lancet 1985;6:1422 -1424

46. Scott DJ, Stevenson CA. Osteochondritis dissecans of the knee in adults. Clin Orthop 1971;76:82-86

47. Smillie IS. Treatment of osteochondritis dissecans. J Bone Joint Surg 1957;39-B:248-260

48. Sevastjanova NA, Mansurova LA, Dombrovskova LE, Slutskii LI. Biochemical characterisation of connective tissue reaction to synthetic polymer implants. Biomaterials 1987;8:242-247

49. Wagner H. Die Kliniek der Knorpeltransplantation bei der Osteochondrosis dissecans. Hefte Unfallheilk 1976;127:118-125

31

3CHAPTER

Should in the treatment of Osteochondritis Dissecansbiodegradable or metallic fixation devices be used?fi

A comparative study in goat knees.

D.B. Wouters1,3

J.Th.M. De Hosson2

R.R.M. Bos3

1 Department of General and Arthroscopic Surgery and Traumatology, TweeSteden Hospital, Tilburg, The Netherlands,2 Department of Applied Physics, University of Groningen, The Netherlands,3 Department of Oral and Maxillofacial Surgery, University Medical Centre Groningen, The Netherlands.

J Biomed Mater Res B Appl Biomater. 2008;84(1):154 – 164

32

Chapter 3

ABSTRACT

Most of the metallic devices have to be removed, treating osteochondritis dissecans lesions.This

animal study describes the biological and mechanical behaviour of screws and pins, made of

commercially available PGA/PLA and PLA96 and metallic screws and pins, used for fragment fixation.fi

A sham operation served as control. A tissue reaction with cavity formation was observed around

every PGA/PLA screw, beginning at 12 weeks following insertion, in contrast to once around a PLA96

screw (p < 0.001), once around one of the 16 PGA/PLA pins and never around those, made of PLA

96 (no significance). Disintegration of the PGA/PLA devices started 6 weeks following implantation fi

against 34 weeks for the PLA96 implants. The gap between the fragment and the recipient cartilage

disappeared only in the sham group. Many fragments of PGA/PLA material were found in the

synovia, in contrast with just a few fragments in the PLA96 group, causing a mild cellular reaction. No

polymer particles were found in the draining lymph nodes at any interval. In conclusion, the tested

biodegradable screws should not be used for fragment fixation in the treatment of Osteochondritisfi

Dissecans. Either an undesirable tissue reaction can be expected (PGAPLA), or, due to the slow

degradation (PLLA), a screw might damage the opposite cartilage during weight bearing. Two

biodegradable pins provide a safe rotational stability and should be combined with one metallic

screw, providing compression. This screw has to be removed before loading the limb to prevent

cartilage wear of the opposite tibia plateau.

33

3

Biodegradable or metallic fi xation devices? A comparative study in goat knees

INTRODUCTION AND OBJECTIVE

The Osteochondritis Dissecans disease should be considered as a pseudarthrosis between the

dissecat and its bed and, consequently, the preferred treatment is reposition of the viable and intact

fragment and fi xation with rotational stability and compression.fi 1-10 Several metallic devices, such as

Kirschner (K.) wires,2,3 pins1 or staples11 have been used. They are easy to insert, small in diameter, but

do not apply the required compression between the fragment and the recipient bone. Obviously,

screws are the devices of choice to produce this compression.4,5,7-9 However, due to their larger

minimal diameter screws cause more damage to the fragment than pins or staples. Moreover, at

least two screws have to be used to achieve rotational stability. The combination of one screw and

two small pins results in less damage than two screws and yet a rotationally stable fixation with fi

substantial compression.

For several reasons most of the metallic devices have to be removed during a second operation

after consolidation of the fragment. When left in place, erosion of the opposite cartilage surface

can occur.4-7,11 Although deeply imbedded, the implants can still gradually protrude through the

cartilage surface and have to be removed after all.11,12 They can also interfere with future imaging

like Computer Tomography (CT) or Magnetic Resonance Imaging (MRI) and radiation therapy.13,14

Finally, some metals, such as chromium, nickel, gold, platinum, cobalt can evoke allergic reactions

like eczema or, if implanted in large amounts, an anaphylactic reaction. Chromium, nickel and cobalt

are also potent carcinogens in animals.15

Three biodegradable polyesters of the alpha-hydroxy carboxylic acid group, polydioxanon,

polyglycolic acid and polylactic acid have been used in humans for the last four decades. Blends

and homo- and co-polymer polymers of polylactic and polyglycolic acid were developed to achieve

optimal characteristics in terms of mechanical properties and biodegradation. However, tissue

reactions like cavity formation or reactive synovitis has been described after the use of pins, screws

or plates composed of several of these materials.16-19

Application of one biodegradable screw and two biodegradable pins could provide a rotationally

stable and compressive fixation in the treatment of the osteochondritis dissecans disease, requiring fi

only one operation, with a minimum of damage to the fragment and avoidance of the above

mentioned disadvantages of the metallic devices. But, the implants should last long enough to

allow consolidation of the fragments and an undesired local tissue reactions or mechanical damage

should not occur.

The aim of this study in goat knees is to evaluate the clinical reliability, the tissue reactions and

cartilage wear of the opposite tibia plateau of a fixation with a combination of one resorbable screw fi

and two resorbable pins, made of two different polymers of an artififfff cially created osteochondral fi

fragment, mimicking an osteochondritis dissecans complex. The outcome is compared with the

results of a conventional metallic fi xation as well as with a sham operation without implantation of fi

devices.

34

Chapter 3

MATERIALS AND METHODS

Animal group and study design

Thirty-two knees were operated of 16, apparently, healthy, Saanen goats, with an age between two

and three years old. The study was approved by the Ethical Committee for Animal Experiments of

the University of Groningen, the Netherlands (nr. 0894-0594/0195).

The procedure was performed under general anaesthesia with 5 mg/kg Nesdonal® (intraveneous),

0.6 mg Temgesic® (intramuscular), and 4 ml ampicilline (intramuscular) as pre-anaesthesia, followed

by an O2/N2O mixture in a ratio of 1:2, combined with Forene® 2% in adequate levels.

Both knees of each goat were operated with an interval of six weeks between the two operations.

The goats were divided into four groups of eight knees each. In the fi rst three groups, the fragment fi

was loosened with a chisel and re-fi xed with the centrally placed screw and two pins, made of fi

respectively two different polymers and surgical steel. In the forth, the sham group, only drill holes ffff

were made and the outlines of the fragment were cut with the trepan (Table 1).

At the end of the experiment, the goats were sacrifi ced using 10 ml of intravenous T 61 (Hoechstfi ®)

and x-photographs were taken of the knees.

The Fisher exact test was used for statistical evaluation of the results.

The devices, inserted in the knees of the goats in the fi rst group were derived from Biomet-USSC fi

(Warsaw, U.S.A.). They were made of a random copolymer composed of 82% poly-L-lactic acid

(PLLA) and 18% poly-glycolic acid (PGA) with a glass transition temperature range between 55-60°C

and an inherent viscosity between 1.15-1.70 dL/g. (Data obtained from the manufacturer).

DSM-Research (Geleen, The Netherlands) produced the as-polymerized poly(96L4D-lactide) (PLA96)

of which the devices used in the second group were made. Polymerisation of the L- and D-lactide

(mole ratio 96/4) was performed in bulk under vacuum for 68 hours at 120°C. As a catalyst stannous

octoate 0.02 w% was used.

The weight-average molecular weight of the PLA96 was 1.5 x 106 g/mol relative to polystyrene

standards, with a residual monomer concentration of 1.8%. The melting temperature was 156.5° C,

the heat of fusion was 27.4 J/g.

The devices were sterilized with a special ethylene oxide (EO) gas sterilisation procedure, i.e. 3 h

exposure to EO gas with a concentration of 715 mg/l at 40°C under a pressure of 510 mbar.

Residual EtO concentration was less than 1 ppm after an aeration time of 3 weeks.

Operation technique

Through a medial parapatellar arthrotomy (Figure 1a), a hole with 2.0mm in diameter (Ø) and 20mm

deep was drilled in the centre of the condyle of all knees, perpendicular to the cartage surface. The

outlines of a standardised fragment of 15mm Ø and 5mm deep were created with a trepan (Figure

1b), the drill hole as centre. Subsequently, two holes of 1.0mm Ø were drilled at the lateral and

medial side of the central hole, halfway the border of the fragment (Figure 1c). In the central hole,

35

3


Figuur 1a: the arthrotomy b: the trepanc: drilling of the holesd: tapping of the screw-thread

Figuur 2a: loosening the fragment with a chisel b: one PGA/PLA screw and 2 pins.

The hexagonal inserting aid breaks off afterff suffi cient torque force applied on the screwffi

c: one PLA 96 screw and 2 pinsd: one screw and 2 pins, made of surgical

steel(see for color image: page 138)

36

Chapter 3

a screw-thread was tapped with a 2.7mm tap (Figure 1d). Subsequently, the fragment, with a bony

part of 5mm thick, was loosened with chisel in 3 of the 4 groups (Figure 2a).

In the first group of eight knees, screws made of PGA/PLA with a thread of 2.7mm Ø, a core of 2mmfi

Ø and 15mm in length and pins with 1.5mm Ø and a length of 15mm were inserted (Figure 2b).

In the second group of eight knees, the screws and pins with the same sizes, were composed of the

PLA96 (Figure 2c).

In the third group, metallic screws and Kirschner wires of corresponding sizes (Synthes, Switzerland)

were used, sterilized in the standard way for metal implants (Figure 2d).

Finally, in the fourth group, the three holes were drilled in the femoral condyle, the thread in the

central hole was cut and the outlines of the fragment were created with the trepan. The fragment

however, was not loosened nor were devices implanted.

All the operations were completed by closure of the wound in layers with Vicryl® 3.0 (Johnson &

Johnson, Warsaw, USA).

Postoperatively, the goats were allowed to load their knees and were observed daily.

Six, 12, 18 and 46-52 weeks following the second operation, four goats, representing two knees of

each diff erent group, were sacrififfff ced (Table 1).fi

Table I. Operation schedule

goat nrfirst operation:fit = 0 implantsleft knee

second operation:t + 6 wks implants rightknee

Survival time afterfi rst operationfi

total insertion time biodegradables

1 metal PLA96 12 weeks 6 weeks

2 PLA96 PLA96 12 weeks 6 weeks + 12 weeks

3 PLA96 sham 12 weeks 12 weeks

4 PLA96 metal 18 weeks 18 weeks

5 PLA96 metal 18 weeks 18 weeks

6 sham PLA96 40 weeks 34 weeks*

7 sham PLA96 52 weeks 46 weeks

8 PLA96 sham 18 weeks 18 weeks

9 PGAPLA metal 12 weeks 12 weeks

10 metal PGAPLA 12 weeks 6 weeks

11 PGAPLA sham 12 weeks 12 weeks

12 PGAPLA metal 18 weeks 18 weeks

13 sham PGAPLA 12 weeks 6 weeks

14 PGAPLA sham 18 weeks 18 weeks

15 metal PGAPLA 52 weeks 46 weeks

16 sham PGAPLA 52 weeks 46 weeks

* Died premature due to goat paratuberculosis or CAE. The knees were uneffectedffff

37

3


Evaluation

Clinical follow up, radiological examination of the knees and histological evaluation of the knees,

the synovia and regional lymph nodes were performed.

The samples of the knees, synovia and lymph nodes were fixed at 4º C in 2fi v/v % glutaraldehyde in

0.1M phosphate-buffer of pH 7.4 (University Medical Centre, Groningen, the Netherlands) for oneffff

week. Two millimetre-thick slices were cut by means of a microtome (Jung 1140/autocut). In the

bony samples, the direction was as much as possible through the screw and the two pins, parallel to

the long axis of the implants. In the soft tissues, the direction of the cuts was perpendicular through

the long axis of the excised tissue. Dehydration followed in graded series of ethanol. The explants

were embedded in 2-hydroxyethyl-methacrylate (“GMA”; Technovit 7100, Heraus-Kulzer, Wehrheim,

Germany). Sections (2 μm) were cut by the same microtome and stained with toluidine blue or

toluidine bleu-basic fuchsine. Light microscopical identification, localisation and evaluation of the fi

polymeric material were carried out with polarised light, induced by crossed Nicol prisms.

RESULTS

Overall

The postoperative course was uneventful in every goat. No limping was observed in the follow up

period.

In the fourth group, intended to be sacrificed after 52 weeks, one goat died prematurely 34 weeks fi

following implantation of PLA96 screws and pins in one knee and 40 weeks following a sham

operation of the other knee. The cause of death was pulmonary goat paratuberculosis; the knee

joints, however, were unaff ected. The retrieval of the specimens took place instantly after death andffff

this goat was included in the series, accepting the slightly shortened implantation time (Table 1).

Cavities around all the screws, composed of PGA/PLA were found after an implantation time of

more than 12 weeks. Only once a similar cavity was found around a screw, made of PLA96.

This diff erence is signififfff cant (p < 0.001).fi

Only once a cavity was found around a pin, composed of PGA/PLA. No cavities were observed

around the 15 other pins of this group and neither around all the 16 pins, made of PLA96. This is not

significant (p > 0.995).fi

Table 2 shows an overview of the microscopical evaluation, which refl ects the foreign body response fl

to the polymers. Details are given below in time.

Macroscopy at 6 weeks. No fracture line was seen anymore on the x-rays and the fragments were

all clinically consolidated at autopsy. No synovitis was found macroscopically in any of the groups.

All goats started walking within a few days following surgery and could bear full weight within a

few weeks.

38

Chapter 3

Microscopy at 6 weeks. At six weeks no area of osteolysis or any infl ammatory reaction wasfl

observed around the screws and pins of both biodegradable polymers (Figure 3a,3b) and the

synovia had a normal morphology. In some cases, the fibrous membrane with fifi broblasts and fi

macrophages around the PGA/PLA and to a lesser extent around the PLA96 material was thickened

and some giant cells were found in these regions (3c,d). To some extent, polymeric debris was

present between the PGA/PLA screws and the original bone. Free erythrocytes were seen in all

groups, but most predominantly in those with PGA/PLA and the metal implants, especially in the

region of the screw-head. A slight increase of the vascularisation in the surrounding bone, mostly

sub-chondral and adjacent to the implant, was found. The PGA/PLA material was already cracking ff

and disintegrating and many fragments appeared in the surrounding tissue (Figure 4a).

In contrast, the PLA96 screws and pins seemed to be still intact. Infrequently, small polymer

fragments were found adjacent to the polymer devices (Figure 4b).

In the synovia of the knees with PGA/PLA devices several small fragments of degraded material were

found. The particles were surrounded or phagocytosed by giant cells (Figure 4c). In the surrounding

Table 2. Tissue response to the (biodegradable) material a

Synoviaimplantationtime material

disintegration

fibrofiblasts

macrophages

giant cells

osteoblasts

vascularisation Material a FBR b

6 weeks PGAPLA ++ + ± + +++ ± - + +++ ++ PLA 96 + + - ++ + + - ± ++ + - ++ 0 - ± 0

metal 0 + 0 0 - ± ++ ++ 0 0sham 0 0 - ± 0 0 +++ ± 0 0

12 weeks PGAPLA +++ + - ++ + - ++ ± - + ++ - +++ ++ ++ ++PLA 96 + + ± ± - + +++ ++ - +++ + - ++ ± - +metal 0 + 0 0 + - ++ + 0 0sham 0 ± 0 0 ++ ± 0 0

18 weeks PGAPLA +++ ± ± ± ++ - +++ ++ - +++ 0 0PLA 96 ± ± ± ± - + + - ++ ± 0 - + 0

metal 0 ± 0 0 + + 0 0sham 0 ± 0 0 + - ++ + - ++ 0 0

46 weeks PGAPLA ++ - +++ 0 ± + ++ - +++ + 0 034 weeks PLA 96 + ± + 0 ++ ++ 0 046 weeks PLA 96 NRc ± + + ++ + 0 052 weeks metal 0 0 0 0 + + 0 052 weeks sham 0 0 0 0 0 + 0 0

a Amount of material present: 0 = absent, ± = sporadically present, + = present, ++ = amplepresent, +++ = abundantly presentb FBR: foreign body reaction: 0 = absent, ± = minimal, + = mild, ++ moderate,c NR: non retrieved

39

Figuur 4: disintegration of the materials at 6 weeks: (see for color image: page 139) a: extensive of the PGA/PLA material surrounded by many particles (p) b: minimal of the PLA 96 material with scarcely a particle (p) found c: PGAPLA particles (p) in the synovia (birefringent). d: the one fragment of PLA 96 material (p), found in the synovia

Figuur 3: aspect at 6 weeks following implantation (see for color image: page139) a: the PGA/PLA devices b: the PLA 96 devices, with some PLA 96 particles (p) c: PGA/PLA material with adjacent fibrous capsule and giant cells (g) and fifi brous tissue (fb)fi d: giant cells (g) surrounding the fragments of PGA/PLA (p)

3


40

Chapter 3

tissue, capillaries as a result of an increase of angiogenesis were observed.

Only once in the reviewed synovia samples in the PLA96 group, a particle of degraded material,

surrounded by giant cells, was observed (Figure 4d).

No sign of polymer particles or an infl ammatory reaction was found in the regional inguinal lymph fl

nodes in any case and at any later interval.

Around the metal devices fibroblasts, premature bone formation and an increased vascularisation,fi

but no infl ammatory cells were observed.fl

In the sham operation group many osteoblasts and young bone formation with some increase of

vascularisation had fi lled the drill holes. The cleft between the cartilage of the fragment and thefi

condyle persisted in all groups except in this sham group.

Macroscopy at 12 weeks. A mild chondropathy of the femoral condyles was seen at autopsy in

some animals with metal implants (Figure 2d). The synovia had a normal aspect in all groups.

Microscopy at 12 weeks. The PGA/PLA material showed progressive fragmentation and a decrease

of birefringency in the centre of the material (Figure 5a). A zone of a sack-like osteolysis with

polymeric debris around the screws of PGA/PLA adjoined a fibrous capsule (Figure 5b). fi

Small particles of PGA/PLA material were dispersed in the neighbouring bone, surrounded by

phagocytic cells (Figure 6a). Some vascularisation adjacent to the screw-head and some osteoblast

activity was noted. Compact fibrous tissue gradually shaded into in newly-formed bone with fifi elds fi

of cartilage-like material. The PLA96 screws and pins, as contrasted with the PGA/PLA devices,

seemed to be still intact and fully birefringent at this stage. A thin fibrous capsule separated them fi

from the contiguous surrounding bone. This bone contained only a few polymer fragments (Figure

6b).

Figuur 5a: loss of birefringence in the PGA/PLA material at 12 weeks after implantation. (see for color image: page 140)

41

3


In the synovia samples of the PGA/PLA group, many polymer particles were observed, encapsulated

by giant cells and surrounded by a macrophage infiltrate (Figure 6c).fi

In the PLA96 group, several fragments were found in the synovia as well, surrounded by only a few

giant cells and macrophages (Figure 6d).

Around the metallic devices, osteolysis was absent. Only a thin fibrous capsule, with many dispersedfi

erythrocytes was formed at the outermost edge of the screw thread. Active new bone formation

separated this layer from the original bone.

In the sham knees the aspect was similar to that at 6 weeks. The drill holes were fi lled up with bone fi

with a few fi broblasts and some blood vessel formation. The clefts in the cartilage, demarcating the fi

fragment, had disappeared. In contrast, they were still visible in both polymer groups and in the

metal group.

Figuur 6: At 12 weeks (see for color image: page 140) a: small particles of PGA/PLA material (p) are spread over the neighbouring bone with inflammatory fl cells and increased vascularity(v) b: the PLA96 devices are still intact. A very thin fibrous capsule (arrow) separates them from the fi contiguous, surrounding bone, containing only a few polymer fragments (p) and immature bone (b) c: In the synovia many polymer particles of PGA/PLA are seen, surrounded by inflammatory cells andfl giant cells (g) d: In the PLA96 group, several fragments are present in the synovia, surrounded by a few giant cells(g)

42

Chapter 3

Macroscopy at 18 weeks. The mild chondropathy of the condyles was found in the group with the

metallic implants, as was seen at 6 weeks. This was also noted in the PGA/PLA and the PLA96 group.

In the sham group, the condyles had a normal aspect. No apparent synovitis was encountered.

Microscopy at 18 weeks. The PGA/PLA material was extensively fragmented. Under crossed Nicol

prisms, the centre of the devices showed still decreased birefringency. Around the screws, a sack-

like defect, comparable with the 12-week specimens, was filled with a fifi ne network of septae (Figure fi

7a). This cavity was surrounded by newly-formed bone.

The PLA96 devices showed some central cracking, but were still fully birefringent. Immature

bone with slightly increased vascularization enclosed the devices. The interface showed a few

macrophages, giant cells, and osteoblasts. In one knee, however, the screw lay in a sack-like hole

similar to the cavity around the PGA/PLA screws at both 12 and 18 weeks with a small amount of

erythrocytes at the inter face with the bone (Figure 7b).

Figuur 7a: at 18 weeks, the sack-like defect (d) around the devices of PGA/PLA (p), filled with a fifi ne network of fiseptae (s)

b: at 18 weeks, in 1 specimen, the PLA 96 device is lying in a sack-like defect (d), similar to the cavity around the PGA/PLA devices at 12 weeks and 18 weeks

c: at 46 weeks, the PGA/PLA implant (p) can clearly be identified, envelopped by a thin capsule (ca), fidirectly adjacent to trabeculae of mature bone. The surrounding space is filled with fifi ne septae (s)fi

d: in all the specimens of the longest surviving group, except in the sham operation group, the inter-fragmentary cleft (arrow) is, with some reaction of the cartilage at acceptor side, still visible. Speci-men after removal of the metal implant

(see for color image: page 141)

43

3


In the metallic implant group newly-formed bone enclosed the implant cavity. Many erythrocytes

filled the space around the screw-head.fi

In the sham group, the operation sites showed a slight increase in vascularisation and number of

osteoblasts. The drill-holes were fi lled with bone formation. fi

Macroscopy at 46 (34) and 52 weeks. The chondropathy of the condyles was slightly more

pronounced, the aspect of the synovia was the same as at 18 weeks.

Microscopy at 46 (34) and 52 weeks. At 46 weeks following insertion, the PGA/PLA implant site

had the same aspect as at 12 weeks and 18 weeks.

The PLA96 devices showed now progressively disintegration. The PLA96 screw, 34-weeks following

implantation in knee of the goat, that prematurely died, had the same aspect as the PGA/PLA

material at 12 weeks and it was surrounded by young bone with a thin fibrous capsule and some fi

macrophages (7c).

The implant cavity in the knee, 46-weeks post implantation of PLA 96 screw and pins, showed a

lining of immature bone and a fibrous capsule. Some polymer debris, with macrophages and giant fi

cells, was noticed.

No birefringent particles were found anymore in the synovia at the 34-week and 46-week interval

of all groups.

In the metallic implants group, the subchondral bone structure in the knees had healed. Locally, still

a small number of erythrocytes surrounded the devices. The gap between the transplant and the

recipient cartilage is still visible (7d).

In the sham operation group only an irregularity in the bone structure, indicating the place of the

drill holes, was seen at the tide mark region with still some enhanced vascularity.

DISCUSSION

The removal operation for metallic fi xation devices can be avoided using biodegradable devices.fi

However, the optimal device and its composition is still not found.

The mechanical properties of the diff erent biodegradable polymers diffffff er widely, from a sheerffff

strength of 179 – 250 MPa for self-reinforced polyglycolide (PGA) rods, to 92 MPa for polydioxanone

pins.20 This is one of the reasons that devices, made of polydioxanone and larger than pins or sutures,

have only been applied experimentally.21, 22

Because of superior mechanical properties of as-polymerised poly (L-lactide) (PLLA), plates and

screws of this material were used to fi x unstable zygomatic fractures in 10 patients by Bos et al.fi 23,24

However, three years after implantation, a swelling at the implantation site was observed,

corresponding with the presence of cavities. In these sack-like defects, densely packed needle-

like PLLA remnants with high crystallinity were found.24 To fi nd material with less residue, thefi

44

Chapter 3

application of other polylactic copolymers like poly (96L/4D-lactide, PLA96), was explored. Disks of

PLA96 and disks of PLLA, subcutaneously implanted in rats, degraded into comparable debris, both

evoking a granulomatous infl ammatory reaction as wellfl 25 and semi-crystalline PLA96 disks were,

even after 101 weeks, still not fully resorbed. The PLLA induced a clinically detectable swelling of the

overlaying soft tissue after 16 weeks and the PLA96 after 101 weeks. In contrast, fully amorphous

poly (50L/50D-lactide) (PLA50) disks of 80 mg, subcutaneously implanted in rats, seemed to be

totally resorbed after 32 weeks.26 But, they induced a considerable tissue reaction as well.

However, intramedullary implanted rods of PLLA and PLA96 in tibiae of rabbits caused no osteolytic

changes to the bone and only a mild histological reaction, as Bergsma showed.27

The PGA/PLA has the theoretical advantage of a faster resorption, leading to less damage to the

opposite cartilage of the tibia plateau, if used for the indication as in our study.

Miller et al. found, that the half life of the 50/50 PGA/PLA copolymer was one week, of the 25/75 PGA/

PLA copolymer about 3 weeks, rapidly increasing to 5 months for 100% pure PGA and 6.1 months

for 100% pure PLLA.28 Theoretically, the 18/82 PGA/PLA copolymer would keep long enough its

mechanical strength to provide consolidation of the fragment, but degrades fast enough to limit

the damage to the opposite cartilage.

The above mentioned considerations led to the choice of the materials in our study.

The diff erence in degradation time between devices of 18/82 PGA/PLA and those made of PLA96, wasffff

also confi rmed in our experiment. But, as found in the literature as well,fi 29,30 a remarkable higher soft

tissue reaction at six weeks and 12 weeks was found the in the synovia samples of the knees with the

PGA/PLA material, compared to those with the PLA96 material (Table 2). A plausible explanation for

this phenomenon is that the amount of degraded material, released during the faster degradation

process, is more than the tissue can absorb and digest. So, during the decomposition of the implant,

as long as the particles are still too large to be ingested by phagocytic cells, they will be found in the

surrounding tissues as was shown in the experiments of Bos et al.24 and Bergsma et al16 [ see also

Ref. 25 pp 95 – 111, 113 – 135]. The slower degradation of PLA96 loads the surrounding tissues less

and evokes less reaction.

The aspect of the PGA/PLA at 6 weeks following implantation suggests that the mechanical strength

is far less than PLA96, which seems still to be intact at that moment. This is confirmed by laboratory fi

studies.16,20,23,25,28 Consequently, the first onset of consolidation of the fifi xed fragments should havefi

taken place considerably earlier than 6 weeks, if PGA/PLA devices are used. The partial loss of

birefringence at 12 weeks, not mentioned in the literature before, as far as we know, suggests also a

local decomposition of the material.

The persistence of the gap between the transplanted fragment and the host cartilage in all the

knees, except in those of the sham operation group is probably caused by a minimum of instability in

the first weeks following operation, not enough to hamper bony consolidation, but interfering with fi

early cartilage healing in those three groups of animals in our study. In the sham group the fragment

remains stable postoperatively. The phenomenon of failure of integration of the transplanted

45

3


cartilage to the recipient surrounding is also described after osteochondral transplantations.29-31

and during the natural cartilage repair process. 32,33 The influence of the stability of the graft is fl

plausible, but not yet proven. Local collagenase VII treatment could improve the integration of the

cartilage edges.34

Though reported in one study,35 no polymer particles were found, in our experiment in the excised

lymph nodes at all time intervals during light microscopically examination under crossed Nicol

prisms.

Sack-like cavities in the bone were found around all the screws in the PGA/PLA group starting at

12 weeks and only once around a pin of the same material. In the PLA96 group, these cavities were

found only once around a screw, 18 weeks following implantation and not around the pins. During

the disintegrative hydrolysis process, the intra-osseous pressure increases due to the uptake of

water by the polymer. If the orifi ces of the drill holes become blocked, the only way the debris canfi

be expelled is into the surrounding spongeous bone, leading to the formation of cavities.22,32,33,36

This is in contrast to intramedullary placed rods, of which the degradation products can be more

easily abducted by the osseous vascular and lymphe drainage system. In their study, Böstman et al.

found these sack-like cavities in fi ve out of 20 animals in a biodegradable screw fifi xation experiment fi

and in one out of four rabbits with a biodegradable pin as implanted device. Bergsma et al. found

a well-defined swelling and identical sack-like cavities at the implantation site in every one of thefi

nine patients in this group.

Our experiment shows, that even when small fragment screws of PGA/PLA are inserted, sack-like

cavities developed in all six cases after 12 weeks of implantation time. Far less, only once out of

six specimens and later following implantation, this occurred around a similar screw of PLA96. In

contrast, only once a cavity was found around one out of the 16, smaller, pins of PGA/PLA and never

around the 16 pins, made of PLA96). This indicates that the amount of biodegradable material of very

small implants, like the used pins, is mostly below the local tissue tolerance level, as described by

Sevastjanova et al.37 Using the larger screws, this level can be exceeded, as found in our experiment

and in the literature as well, leading to sack-like defects in the bone.22,25,27,32,33,36

Recently, also the second disadvantage has been demonstrated in the literature as well. Due to the

relatively long degradation time of PLLA screws, the cartilage in patients, opposite to the screw, was

damaged when the limb in question was loaded before total degradation of the screw.38,39

Several means are applied to sterilize devices, made of PLLA or its co-polymers, i.e. plasma and

ethylene oxide (EtO), gamma radiation and electron beams. Potentially, they can influence fl

the mechanical properties by accelerate the degradation and increase the cristalinity. The

biodegradable material used in this study was sterilized with EtO and several authors demonstrate,

that this sterilisation method did not alter markedly the properties during in vitro degradation.42,43

Moreover, during the sterilisation according to the method, developed by Griffith Microscience in ffi

cooperation with the department of Polymer Science and Maxillofacial Surgery of the University of

Groningen, the temperature of the gas is 40° Celsius. Analysis of the as-polymerized PLA96 revealed

46

Chapter 3

no signifi cant (p>0.05) changes in the initial material properties (Table III).fi 42

In contrast, steam sterilisation or annealing at 120º C at 4 hours prior to sterilisation by ethylene

oxide can infl uence the properties substantially.fl 43,44

Therefore, according to these biodegradation characteristics, the application of thin pins as

biodegradable fi xation devices, sterilized with ethylene oxide, seems to be more safe than the use fi

of the, more bulky, biodegradable screws. At the other hand, the use of a faster resorbing material

like PLA50 or 75/25 PGA/PLA as raw material will compromise the mechanical demands.

Metal implants induce, biologically seen, far less tissue reaction. Screws are easy to remove in the

same way as they are inserted, i.e in open as well as in arthroscopic procedures. In contrast, small

metallic pins are much more diffi cult to remove, due to the lack of hold, when grasping these ffi

headless tiny implants. Unsuccessful as well as successful attempts will both lead to considerable

local cartilage damage.

The combination of a metal small fragment screw and two biodegradable pins is in our opinion

the way of fixation of choice in the treatment of osteochondritis dissecans at this moment.fi 45

CONCLUSIONS

Reviewing the results of this study and the available literature, the best way to fix the fragments in fi

the treatment of Osteochondritis Dissecans is, in our opinion, the insertion of one, easy to remove,

centrally placed, metallic small fragment screw, in combination with two biodegradable pins made

of one of the tested materials. This combination provides compression as well as rotational stability

during the process of consolidation. If a pin, made of PGA/PLA, is used, the risk of damage to the

opposite cartilage of the tibia plateau is less, due to the faster degradation, compared to a pin, made

of PLA96.

The metallic screw should be removed after full consolidation of the fragment and before loading

the limb.

The use of a biodegradable screw of PGA/PLA results in a significant risk for an undesirable tissue fi

reaction. A PLLA screw will lead to damage of the opposite cartilage surface due to a too slow

degradation of the polymeric material.

Acknowledgements

We would like to express our gratitude to Mr. H.E. Moorlag, from the Department of Medical Biology,

and Mrs. M.B.M. van Leeuwen, from the department of Biomaterials, both of the University Medical

Centre Groningen for their work and assistance with the preparation and evaluation of the slides.

Mr. J.G.M. Burgerhof of the Department of Epidemiology, University Medical Centre Groningen, the

Netherlands, was of a great help during the statistical analysis of the data.

47

3


References

1. Smillie IS. Treatment of osteochondritis dissecans. J Bone Joint Surg (B) 1957;39: 248–260

2. Anderson A, Lipscomb AB, Coulam C. Antegrade curettement, bone grafting and pinning of osteochondritisdissecans in the skeletally mature knee. Am J Sports Med 1990;18(3): 254–261

3. Guhl JF. Arthroscopic treatment of Osteochondritis Dissecans. Clin Orth 1982;167:65–74


5. Wagner H. Die Kliniek der Knorpeltransplantation bei der Osteochondrosis dissecans. Hefte zurUnfallheilkunde 1976;127:118–125

6. Gschwend N, Munzinger U, Löhr J. Unsere extraarticuläre Dissecatverschraubung bei Osteochondrosisdissecans des Kniegelenkes. Orthopäde 1981;10:83–86

7. Johnson LL, Uitvlugt G, Austin MD, Detrisac DA, Johnson CJ. Osteochondritis Dissecans of the Knee: Arthroscopic Compression Screw Fixation. Arthroscopy 1990;6(3):179–189



10. Garret JC, Kress KJ, Mudano M. Osteochondritis dissecans of the lateral femoral condyle in the adult.Arthroscopy 1992; 8(4): 474–481

11. Kivistö R, Pasanen L, Leppilahti J, Jalovaara P. Arthroscopic repair of osteochondritis dissecans of the femoral condyles with metal staple fixation: a report of 28 cases. Knee Surg Sports traumatol Arthroscfi2002;10:305–309

12. Bobic V. Cover photograph, Arthroscopy 2001;17(5)

13. Scher N, Poe D, Kuchmir F, Reft C, Weichselbaum R, Panje WR. Radiotherapy of the resected mandible following stainless steel plate fi xation. Laryngoscope 1988;98: 561–563fi

14. Castillo MH, Button TM, Homs MI, Pruett CW, Doerr R. Effects of radiation therapy on mandibular ffffreconstruction plates. In: Trans 41st Ann Cancer Symp. The Society of Surgical Oncology, New Orleans,Louisiana, U.S.A.. 1988; p144

15. Black J. Orthopedic Biomaterials in Research and Practice. Churchill Livingstone New York, Edinburgh London, Melbourne. 1988. p 292–302



18. Friden Th, Rydholm U. Severe aseptic synovitis of the knee after biodegradable internal fixation. ActafiOrtho Scand 1992;63(1):94–97

19 Barford G, Svensen RN. Synovitis of the knee after intraarticular fracture fixation with Biofifi x. Acta Orthop fiScand 1992;63(6):680 – 681 [20. Hirvensalo E. Absorbable synthetic self-reinforced polymer rods in thefixation of fractures and osteotomies. 1990 Thesis University of Helsinki Finland. p 10–11fi

21. Iizuka T, Mikkonen P, Paukku P, Lindqvist C. Reconstruction of orbital fl oor with polydioxanone plate. Int JflOral Maxillofac Surg 1991;20:83–87

22. Ewers R, Förster H. Resorbierbare Osteosynthesematerialien. Eine tierexperimentelle Studie. Dtsch Z Mund Kiefer Gesichts Chir 1985;9:196–201

23. Leenslag JW, Pennings AJ, Bos RRM, Rozema FR, Boering G. Resorbable materials of polyL-lactide).VI. Plates and screws for internal fracture fixation. Biomaterials. 1987;8:70–73fi

24. Bos RRM, Rozema FR, Boering G, Nijenhuis AJ, Pennings AJ, Verwey AB. Resorbable poly(L-lactide) plates

48

Chapter 3

and screws for the fi xation of unstable zygomatic fractures. J Oral Maxillofac Surg 1987;45:751–753 fi

25. Bergsma JE. Late complications using poly(lactide) osteosyntheses, in vivo and in vitro tests. Thesis. University of Groningen, the Netherlands 1995. p 95–111

26. Miller RS, Brady JM, Cutright DE. Degradation rates of oral resorbable implants (polylactates andpolyglycolates); rate modifi cation with changes in PLA\PGA copolymer ratios. J Biomed Mater Resfi1977;11(5):711–719

27. Böstman OM, Päivärinta U, Manninen M, Rokkanen P. Polymeric debris from absorbable polyglycolidescrews and pins. Acta Orthop Scand 1992;63(5):555–559

28. Bergsma JE, Rozema FR, Bos RRM, de Bruin WC. Foreign-body reactions to resorbable poly(l-lactide)bone plates and screws used for the fixation of unstable zygomatic fractures. J Oral Maxillofac Surgfi1993;51(6):666–670

29. Hangody L, Kish G, Karpati Z, Eberhart R. Osteochondral plugs: Autogenous Osteochondral mosaicplastyfor the treatment of focal chondral and osteochondral articular defects. Operative techn in orthopaedics1997;7(4):312–322

30. Bobic V. Arthroscopic osteochondral autogenous graft transplantation in anterior cruciate ligamentreconstruction: a preliminary report. Knee Surg Sports Traumatol Arthrosc 1996;3:262–264

31. Tew SR, Kwan APL, Hann A, Thomson BM, Archer CW. The reactions of articular cartilage to experimental wounding: role of apoptosis. Arthritis Rheum 2000;43 :215–225

32. Shapiro F, Koide S, Glimcher MJ. Cell origin and differentiation in the repair of full-thickness defects of ffffarticular cartilage. J Bone Surg Am 1993;75:532–553

33. Verwoerd-Verhoef HL, ten Koppel PG, van Osch GJ, Meeuwis CA, Verwoerd CD. Wound healing of cartilagestructures in the head and neck region. Int J Pediatr Otorhinolaryngol 1998;43:241–251

34. Bos PK, DeGroot J, Budde M, Verhaar JAN, van Osch GJVM. Specifi c enzymatic treatment of bovine andfihuman articular cartilage: implications for integrative cartilage repair.Arthritis Rheum 2002;46(4):976–985

35. Verheyen K. Resorbable materials with bone bonding ability. Thesis. University of Leiden, the Netherlands 1993. p 152–156

36. Böstman OM. Osteolytic changes accompanying degredation of absorbable fracture implants. J BoneJoint Surg 1991(B);73(4):679–682

37. Sevastjanova NA, Mansurova LA, Dombrovskova LE, Slutskii LI. Biochemical characterisation of connective tissue reaction to synthetic polymer implants. Biomaterials 1987;8:242–247

38. Friederichs MG, Greis PE, Burks RT. Pitfalls associated with fixation of Osteochondritis Dissecans fragments fiusing bioabsorbable screws. Arthroscopy 2001;17(5):542–546

39. Kumar A, Malhan K and Roberts SNJ Chondral Injury from Bioabsorbable Screws after Meniscal Repair. Arthroscopy 2001;17(8):34

40. Claes LE, Ignatius AA, Rehm KE, Scholz C. New bioresorbable pin for the reduction of small bony fragments: design, mechanical properties and in vitro degradation. Biomaterials 1996;17(16):1621-6

41. Nuutinen JP, Clerc C, Virta T, Tormala P. Eff ect of gamma, ethylene oxide, electron beam, and plasmaffffsterilization on the behaviour of SR-PLLA fi bres in vitro. J Biomater Sci Polym 2002;13(12):1325-36 fi

42. Cordewener FW, Rozema FR, Bos RRM, Grijpma DW, Boering G, Pennings AJ. Material properties and tissueWWreaction during degradation of poly(96L/4D-lactide). J Mat Science Mat Med 1995;6:211–217

43. Gogolewski S, Mainil-Varlet P. Eff ect of thermal treatment on sterility, molecular and mechanical propertiesffffof various polylactides. 2. Poly(L/D-lactide) and poly(L/DL-lactide). Biomaterials 1997;18(3):251-5

44. Weir NA, Buchanan FJ, Orr JF, Farrar DF, Boyd A. Processing, annealing and sterilisation of poly-L-lactide.Biomaterials 2004;25(18):3939-49

45. Wouters DB, van Horn JR, Bos RRM. The use of biodegradables in the treatment of osteochondritis dissecans of the knee: fiction of future? Acta Orthop Belgica 2003;69(2):175–181fi

49

4CHAPTER

The Meniscus Arrow® or metal screw for treatment of Osteochondritis dissecans?

In Vitro comparison of their effectiveness.ffff

D.B. Wouters1,4

R.R.M. Bos2

L.J. Mouton3

J.R. van Horn4

1 Department of General Surgery, Traumatology and Arthroscopic Surgery TweeSteden Hospital, Tilburg, 2 Department of Oro-Maxillo and Facial Surgery,University Hospital, Groningen, the Netherlands,3 Center for Human Movement Sciences, University of Groningen, The Netherlands,4 Department of Orthopaedic Surgery, University Hospital, Groningen, the Netherlands.

Knee Surg Sports Traumatol Arthrosc. 2004 Jan;12(1):52-7

50

Chapter 4

ABSTRACT

Three draw bench tests in axial direction were conducted to examine the pull out forces in predrilled

human condylar bone of one single Meniscus Arrow, one single metal screw and three Meniscus

Arrows in one bone block, the Arrows being inserted using the standard hand instruments. Bone

blocks with three Meniscus Arrows were tested additionally in tangential direction, imitating shear

forces. All observed values were within the range of 1 standard error (SE) or higher and exceeded

the values in meniscal tissue, as reported in the literature. These are much higher than the shear

force during a single movement in the human knee. Most metallic devices, used for fixation of the fi

fragments in the treatment of osteochondritis dissecans must be removed in a second operation.

Left in place, as with Herbert screws, they can disturb future imaging and damage the opposite

cartilage of the tibia plateau. Staples, left in place, can break. Finally, some metals evoke allergic

reactions and, at least in animals, are potent carcinogens. Although fusion of osteochondritis

dissecans fragments in their original locations, fixed with non compressive biodegradable pins, has fi

been reported, these tests show the hold of compressive meniscus Arrows in bone to contribute to

a better result than non-compressive pins. Other biodegradable devices are also available for this

application. However, one advantage is that using meniscus Arrows, already available in the hospital

for mending ruptured menisci, saves the costs of investing in other sets of instruments and devices.

Another advantage is the smaller diameter of the meniscus Arrows than that of other biodegradable

devices, resulting in less damage to the fragments.

51

4


INTRODUCTION

Several diff erent non metallic devices have been used over the last 5 decades for fragment fiffff xationfi

in the treatment of Osteochondritis Dissecans, like bone pegs or cartilage - bone cylinders5,18 or

metallic devices like pins,17,25 staples 20 or screws2,11,19 in all sort of designs. For several reasons, most

metallic devices have to be removed by means of a second operation. Left in place, they cause

damage to the opposite cartilage surface of the tibia.11,13,17,19,20 Left in place, but imbedded under

the cartilage surface,25 they can disturb future imaging like CT or MRI or, gradually protruding,

they cause cartilage damage after all.7 Chromium, nickel and cobalt are also potent carcinogens in

animals.6 This stimulated the research for biodegradable devices that, once inserted, do not have

to be removed after consolidation of the fragment. Three biodegradable polymers; polydioxanon,

polyglycolic acid and polylactic acid and their co-polymers, combinations or blends, are used for

this purpose. However, both synovitis and sterile inflammatory sinus formation are reported whenfl

using polyglycolic acid and polylactic acid devices.3,4,9,15

Although good results with only biodegradable pins as fixation devices have been reportedfi 10,22,

stable fi xation with compression screws contributes to a better healing of the reinserted fragment,fi

especially in adults,2,11,13,19 probably because it neutralizes both shear and disrupting forces. The

disadvantage of pins is that no substantial compressive hold can be applied.

Meniscus Arrows® (M.A.’s, Bionix Implants Ltd Tampere, Finland), have been in use for several years ago

and are to mend ruptures in the vascularised part of the meniscus. They consist of a biodegradable

polylactic acid copolymer, have a smaller diameter (1.1 mm) than the smallest biodegradable screws

(2.0 mm) or nails (1.5 mm; Smart Nail®, Bionix Implants Ltd Tampere, Finland) and can be inserted

arthroscopically. Since they are already available in the hospital, their use obviates the purchase of

further sets of instruments. For these reasons, they could become the preferable fixation devices forfi

treatment of osteochondritis dissecans if they could provide sufficient stable hold in bone. The aim ffi

of this study, with a view to the application as fixation devices for the treatment of osteochondritis fi

dissecans, was to test the hold in bone of the Arrows and compare this to the hold of screws with a

diameter of 2 mm (Figure 1).

Figure 1: The 2 devices tested:on top the A.O. screw with a diameter of 2 mm and a length of 15 mmbelow the Meniscus Arrow® with a length of 16 mm(see for color image: page 141)

52

Chapter 4

MATERIALS AND METHODS

Fresh frozen and thawed human condyles were clamped in an Instron 1195 draw bench materials

testing device. The load cell measured 1000N maximum, with a scale set at 0 – 200N for the Arrows

and at 0 – 500 for the screws, with a time scale of 0 – 600 sec. The extraction speed was 5 mm / min.

A drill with a diameter of 1.0 mm was used to create the holes, using a template measuring 20 x

20mm (Figure 2). The Arrows were carefully inserted with a small hammer using the standard hand

instruments.

Figure 2: Standardizing the drill holes, using a template

Three times a single Arrow with a length of 16 mm was pulled out of the bone in an axial direction

(Figures 3,4).

Twice a single Arrow after extraction as described above was re-inserted in the original holes, to test

the pull out force of the damaged Arrow.

Three bone blocks were prepared. The blocks were 3 mm thick. Each bone block was fixed with 3fi

new Arrows on its original location and pulled out of the bone in an axial direction (Figure 5). Three

times this was performed with new blocks and Arrows in a direction parallel to the joint surface,

thus applying a shear force on the devices (Figures 6,7). As an additional test, in one case the bone

block, with still macroscopically intact Arrows, was refi xed and subsequently pulled offfi again in theff

same direction (Ars 11).

Finally, 3 metal screws (Synthes, Switzerland) with a diameter of 2 mm and a length of 15 mm were,

successively, pulled out of the bone in the same way as the single Arrow.

4


53

Figure 3: One Meniscus Arrow®, put through a hole in a metal loop, inserted in the condyle, tobe pulled out

Figure 4

54

Chapter 4

Figure 5: One bone block, fi xed with 3 Meniscus Arrows®, with 3 metal loops between block fiand condylar bone, to be pulled off

Figure 6: The shear force testing.One bone block, fixed with 3fiMeniscus Arrows®, with 3 metalloops between block and condylarbone, to be pulled off

55

4


RESULTS

The results are presented in Table 1; the Standard Error formula was used to evaluate the results.

The extraction force of a single Arrow ranged between 59N and 78N, with an average of 68N.

The average extraction force of the bone block, fi xed with 3 Arrows ranged for the axial direction fi

between 108N and 148N, with an average of 122N.

In tangential direction the respective values were 115N and 128N, with an average of 121N. The axial

extraction of the single screws resulted in values between 162N and 334N, with an average of 232N.

Axial extraction of 2 of the 3 bone blocks after reinsertion in the previous holes of the 3 Arrows,

apparently minimally damaged, produced values between 44N and 55N. After the same procedure

with one bone block in tangential direction 102N was noted.

The intermittent tensioning and retensioning of the system causes the sawtooth like pattern in

Figures 4 and 7. When the Arrow shifts upwards the system unloads itself again. This repeats several

times (Figures. 4,7)

DISCUSSION

No findings have yet been published regarding the application of the Arrow in bone. During its 8 fi

years of extensive clinical use only occasional synovitis has been reported after insertion of Arrows

for meniscal repair.23,26 Several reports have been published regarding the pull-out force of Arrows

out of menisci. The mean value of 68N in our tests, exceeds the value reported in literature (53N,

44N and 57N).1,8,28 The values in our series are within the range of ±1 standard error or even higher

(table 1). Although the pull-out force, as would be expected, was lower after reinsertion due to

Figure 7

56

Chapter 4

deformation of the barbs, the Arrows still showed a considerable hold in the bone (mean value 50N).

The contact surfaces of the motionless joint normally keep a replaced fragment in place by the

compressive force arising in the joint due to the ligaments – and muscle action and body weight

– as long as it stays in contact with both joint surfaces. If the load is varying during movements or

unloading the limb, dislocating micro movements can inhibit the fusion of the fragment when non-

compressing pins are used. This could explain the variability in the results when pins are used as

fixation devicesfi 10,13,22 and indicates that fi xation with compression or stable hold is preferable.fi 2,11,13,19

Biodegradable screws or nails produce larger holes in the fragment having a considerably larger

diameter than 1.1mm. They will dissolve slowly4, due to their larger volume and the characteristics

of the biodegradable material, which can lead to erosion on the opposite cartilage of the tibia

plateau.16,21 Furthermore, the quantity of the implanted material in relation to the degradation

characteristics of the material may be a factor influencing the clinical manifestation of the foreign fl

body reaction.4,27 Shear forces are extremely low in a knee joint; friction coefficients range fromffi

0,005 to 0,023.12,14 During walking the maximum load on the knee is four times the bodyweight.24 An

estimate of the shear force acting on the fragment during walking can therefore be made as follows.

The shear force is equal to the product of the friction coeffi cient and the maximum compressiveffi

load arising in the joint, (= 4 x body weight). Thus for an individual with a body weight of 80 kg the

shear force is between 16 and 74 N.12,14,24

The shear force of over 100N, measured in our tests of the bone blocks, fixed with three Arrows is fi

much higher than required to dislocate the fragment in one cycle of movement of the human knee

in the loaded situation. However, weight bearing, moving and walking impose repetitive strains

on the fragment. These strains are not tested here, but should be taken into account in clinical

application.

The fragile heads of the Arrows are positioned suffi ciently far below the cartilage surface to reduce ffi

the risk of damaging the opposite joint surface while moving the joint after consolidation but before

degradation of the Arrows (Figure 8). The barbs are the structures of the Arrows mainly responsible

for the grip in the tissue. The free space of the shaft between the head of the Arrow and the first barb fi

(figure 1) measures 6mm. This implicates that the thickness of the bony part of the fragment shouldfi

Table 1

Measurements Mean ±SE Range

1 2 3

Single Arrow 59 68 78 68±10 58.8 - 77.8

Bone block (3 Arrows), after reinsertion 55 44 - 50±8 41.7 - 57.3

Bone block (3 Arrows) 110 148 108 122±23 99.5 - 144.5

single screw 162 200 334 232±90 141.6 - 322.4

shear force tests 115 120 128 121±7 114.4 - 127.6

shear force tests after reinsertion 102 - - - 102.0 - 102.0

57

4


not exceed 5mm to ensure that all the barbs are at least 1 mm in the recipient bone tunnel. Clinical

use of the procedure described above began after completing this biomechanical study.

CONCLUSION

The meniscus Arrows have suffi cient initial hold in bone to be used as fiffi xation devices in the treatmentfi

of osteochondritis dissecans disease. In the clinical setting prompt reinsertion in the femur condyle

can be considered, if meniscus Arrows, already advanced through the fragment in the recipient

bony bed, are mistakenly extracted from the condyle during the operation procedure. Because

of the repetitive strain on the fi xation devices in the clinical situation, temporary immobilisationfi

should be considered to induce the fi rst impulse to consolidationfi

Acknowledgements

We are grateful for the advise of Mr. Paul M. Bronsveld and Mr. Ronald L.W. Popma and for the

assistance of Mr. Uko B. Nieborch of the Department for Applied Physics of the University of

Groningen during the mechanical tests. We also thank Dr. B.B. Seedhom of the Department for

Rheumatology of the University of Leeds (U.K.) for his linguistic reviewing of this manuscript.

Figure 8: Already pulled-off bone blocks. The aspect of the Meniscus Arrow® headsff

58

Chapter 4

References

1. Albrecht-Olsen P, Lind T, Kristensen G, Falkenberg B (1994) Pull –out test after reinsertion of meniscusbucket – handle lesions with suture versus Biofix tacks- an experimental study. Acta Orthop Scand 65 fi(Suppl 260):17

2. Bandi W, Allgöwer M (1959) Zur Therapie der Osteochondritis Dissecans. Helv Chir Acta 26: 552–5583. Barfod G, Svendsen RN (1992) Synovitis of the Knee after intraarticular Fracture fixation with Biofifi x®. Actafi

Orthop Scand 63 (6): 680–6814. Bergsma EJ (1995) Late complications using poly (lactide) osteosyntheses in vivo and in vitro tests. Thesis.

University of Groningen, the Netherlands, pp 9–355. Berlet GC, MA’scia A., Miniaci A (1999) Treatment of Unstable Osteochondritis Dissecans lesions of the Knee

using Autogenous Osteochondral Grafts (Mosaic Plasty). Arthroscopy 15 (3): 312–3166. Black J. Orthopedic Biomaterials in Research and Practice. Churchill Livingstone New York, Edinburgh

London, Melbourne. 1988; pp 292–302 7. Bobic V. Cover photograph, Arthroscopy 2001; 7(5)8. Boenisch U, Faber K, Ciarelli M, Arnoczky S (1998) Pull out strength and stiffness of meniscus repair usingff

absorbable arrows versus ti-cron vertical and horizontal loop sutures. Proc 8th congr of the Europ SocSports Traumatol, Knee Surgery and Arthrosc p 81

9. Böstman O, Hirvensalo E, Mäkinen J, Rokkanen P (1990) Foreign-body Reactions to Fracture Fixation Implants of Biodegradable Synthetic Polymers. J Bone Joint Surg 72 B: 592–596

10. Claes L, Burri C, Kiefer M, Mutschler W (1986) Resorbierbare Implantate zur Refi xierung von osteochondralenfiFragmenten in Gelenkflachen. Aktuell Traumatollfl 16:74–77

11. Cugat R, Garcia M, Cisco X, Manllau JC, Juan X, Ruiz-Cotorro A (1993) Osteochondritis Dissecans: A historical review and its treatment with cannulated screws. Arthroscopy 9(6):190–197

12. De Keizer G (1976) On synovial fluid, joint lubrication and osteoarthritis. Thesisfl . University of Utrecht, the Netherlands, p 93 and pp 114-115

13. Federico DJ, Lynch JK, Jokl P (1990) Osteochondritis Dissecans of the Knee: A Historical review of Etiology and Treatment. Arthroscopy 6(3):190–197

14. Freeman MAR (1979) Adult Articular Cartilage. Second edition. Pitman Medical Publishers U.K., pp 418-41915. Friden Th, Rydholm U (1992) Severe aseptic synovitis of the knee after biodegradable internal fixation. Actafi

Ortho Scand 63(1):94–9716. Friederichs MG, Greis PE, Burks RT (2001) Pitfalls associated with fixation of Osteochondritis Dissecans fi

fragments using bioabsorbable screws. Arthroscopy 17(5):542–546 17. Guhl JF (1982) Arthroscopic Treatment Of Osteochondritis Dissecans. Clin Orthop 167: 65–7418. Johnson, EW and Mc Leod TL (1997) Osteochondral Fragments of the Distal End of the Femur Fixed with

Bone Pegs. J Bone Joint Surg 59A:677–67919. Johnson LL, Uitvlugt G, Austin MD, Detrisac DA, Johnson C (1990) Osteochondritis of the knee: Arthroscopic

compression Screw Fixation. Arthroscopy 6(3):179–18920. Kivistö R, Pasanen L, Leppilahti J, Jalovaara P. Arthroscopic repair of osteochondritis dissecans of the

femoral condyles with metal staple fixation: a report of 28 cases. Knee Surg Sports Traumatol Arthroscfi2002; 10: 305–309

21. Kumar A, Malhan K and Roberts SNJ (2001) Chondral Injury from Bioabsorbable Screws after MeniscalRepair. Arthroscopy 17(8): E 000–000

22. Matsusue Y, Nakamena T, Suzuki S, Iwasaki R (1966) Biodegradable Pin fixation of osteochondral Fragmentsfiof the knee. Clin Orthop 322:166–173

23. Menche DS, Phillips GI, Pitman MI, Steiner GC (1999) Inflammatory Foreign Body Reaction to an ArthroscopicflBioresorbable Meniscal Arrow Repair. Arthroscopy 15(7):770–773

24. Morrison JB (1968) Bioengineering analysis of force actions transmitted by the knee joint. Biomed Eng4:164–170

25. Smillie IS (1957) Treatment of Osteochondritis Dissecans. J Bone Surg 39B:248–26026. Song EK, Lee KB, Yoon TR (2001) Aseptic synovitis after meniscal repair using the biodegradable meniscus

59

4


arrow. Arthroscopy 17(1):77–8027. Sevastjanova N.A., Mansurova L.A., DombrovskovaL.E., Slutskii L.I. Biochemical characterisation of

connective tissue reaction to synthetic polymer implants. Biomaterials 1987;8:242–247 28. Törmälä P, Karhi O, Koho P, Tamminmäki M (2000) A novel inserter instrument (Crossbow) for installation of

self-reinforced bio absorbable arrows into meniscus tissue. Knee Surg Sports Traumatol Arthrosc 8:370–372

60

61

5CHAPTER

Will the hold of solid biodegradable implants be influencedflby swelling during the degradation process?

An in-vitro study with Meniscus Arrows®.

D.B. Wouters1,2

R. R.M. Bos2

J. Th. M. De Hosson3

1 Department of General and Arthroscopic Surgery and Traumatology, TweeSteden Hospital, Tilburg, The Netherlands,2 Department of Oral and Maxillofacial Surgery, University Medical Centre Groningen, The Netherlands,3 Department of Applied Physics, University of Groningen,The Netherlands.

Knee Surg Sports Traumatol Arthrosc 2007; 15:1204–1209

62

Chapter 5

ABSTRACT

Water uptake after implantation of biodegradable devices induces swelling, as mentioned in the

literature.

The hold in bone of solid devices will increase, if the swelling is substantial enough.

The results of weighing 6 Meniscus Arrows® (M.A.’s) before and after immersion in a sterile phosphate

buff ered saline solution during diffffff erent time intervals were compared with the outcome of ffff

measurements under a field-emission scanning electron microscope of 6 other M.A.’s, stored underfi

comparable conditions. The data were statistically evaluated with the Wilcoxon’s signed rank test.

The weight increased statistically significant in the fifi rst 2 hours following immersion with 2.1mg or fi

9.16%, remaining stable afterwards at an avarage weight gain of 1.7mg or 7.18%.

The core diameter of the M.A.’s increased in time with 0.01mm or 1.01%. Although this is statistically

significant, it is not expected to have consequences for the hold.fi

However, a remarkable and statistically significant decrease of the outer inter-barb diameter was fi

noted in time of 0.15mm or 8.6%.

Mechanical testing should reveal the clinical relevance of the results of this study.

63

5

Swelling of solid biodegradable implants during degradation

INTRODUCTION

Three biodegradable polymers, i.e. polydioxanon, polyglycolic acid and polylactic acid and their co-

polymers, combinations or blends, are currently used for the production of biodegradable devices

to fix fracture fragments in humans. In the optimal situation their mechanical properties allowfi

consolidation of the bony fragments that they fix and their resorption passes offfi without negativeff

side eff ects.ffff 1

Degradation occurs mainly by the uptake of water during the hydrolisation process and in

a lesser extent by enzymatic influence.fl 2,3,4 Several factors affect this degradation. One is theffff

increase of specifi c surface and the other is hydrophilia, both promoting the uptake of water.fi

Further, amorphous regions are more susceptible for the hydrolytic attack of the chemical bonds,

than crystalline regions. In this way the long polymeric chains are cut into shorter chains by the

water molecules that act as molecular scissors. These short chains slip easier passing each other,

leading to a decrease in polymer strength and to fragmentation of the material. This enhances the

susceptibility for further degradation.5,6 The small fragments are phagocytized by macrophages

during the physiological infl ammatory response.fl 6,7,8 The circumstances at the implantation site

eff ect the resorption process as well.ffff 9,10

The uptake of water during this degradation process induces a swelling or distention of the polymeric

material.4,7,8 If this is substantial the initial fixation of the devices in bone could be enhanced. Thusfi

this phenomenon could infl uence the mechanical properties in view of the clinical application.fl

In general, this swelling or distention, due to the uptake of water, has been related to an increase

of weight of the material.11–15 In fact, only a few authors measure the increase of the dimensions in

some way and term this swelling.4,16,17

In this study the change of the weight of six Meniscus Arrows® made of 96L-4D PLA (PLA96) in time

is compared to the change of size of the devices by means of measuring their dimensions under a

field emission scanning electron microscope. fi

METHODS

Six Meniscus Arrows® (M.A.’s, Bionix Implants Ltd Tampere, Finland), were weighed by means of a

balance (Satorius) with an accuracy of 0.1 milligram. Subsequently, they were submerged in a sterile

phosphate buff ered saline solution (PBS, Pharmacy of the University Medical Centre, Groningen, ffff

The Netherlands) at 37º Celsius. Reweighing was performed after drying the M.A.’s with tissue-paper

at 2, 4, 6, 8, 24, 28, 32, 48, 60 hours and 7, 10, 14, 18, 28 days later.

Parallel to this series the core diameter and the distance between the tips of the barbs of a second

series of 6 M.A.’s were measured (Figures 2,5) in a field-emission scanning electron microscope (type fi

Philips FEG XL-30), also starting at t=0 (t1) and at 2, 4, 6, 24 hours and 3, 4, 5, 7, 11 and 18 days

afterwards. The data are rounded off at an accuracy of 10 micrometer (Figures 2, 5). In between ff

64

Chapter 5

these measurements the M.A.’s were kept submerged in the PBS solution at 37º Celsius as well. This

experiment was fi nished after 18 days, achieving, statistically, suffifi cient results.ffi

All the results were statistically evaluated with the Wilcoxon’s signed rank test.

Results of the weigh experiment (Table 1, Figure 1)

Table 1: Change of weight of 6 Meniscus Arrows® during 28 days of immersion

Arrow nr Thrs = 0: t1 Thrs = 2: t2 Thrs = 4: t3 Thrs = 6: t4 Thrs = 8: t5

1 0.0228 0.0254 0.0244 0.0240 0.02412 0.0226 0.0246 0.0247 0.0245 0.02413 0.0226 0.0248 0.0244 0.0244 0.02454 0.0226 0.0246 0.0245 0.0243 0.02465 0.0228 0.0245 0.0241 0.0246 0.02446 0.0230 0.0250 0.0243 0.0250 0.0246Weight increase* 9.16% 7.34% 7.62% 7.26%

Arrow nr Thrs = 24: t6 Thrs = 28: t7 Thrs = 32: t8 Thrs = 48: t9 Thrs = 60: t10

1 0.0250 0.0251 0.0242 0.0242 0.02402 0.0260 0.0240 0.0243 0.0241 0.02433 0.0246 0.0244 0.0243 0.0244 0.02494 0.0241 0.0242 0.0243 0.0252 0.02455 0.0244 0.0244 0.0247 0.0253 0.02566 0.0246 0.0249 0.0245 0.0250 0.0245Weight increase* 9.03% 7.77% 7.26% 8.65% 8.36%

Arrow nr Td = 3: t11 Td = 4: t12 Td= 8: t13 Td = 10: t14 Td = 14: t15

1 0.0248 0.0238 0.0249 0.0246 0.02432 0.0251 0.0247 0.0248 0.0242 0.02413 0.0247 0,0246 0.0249 0.0243 0.02484 0.0242 0,0248 0.0246 0.0245 0.02505 0.0248 0.0254 0.0256 0.0249 0.02546 0.0242 0.0250 0.0244 0.0243 0.0244Weight increase* 8.37% 8.28% 9.39% 7.63% 8.51%

Arrow nr Td = 18: t16 Td = 28: t17

1 0.0244 0.02442 0.0246 0.02403 0.0245 0.02424 0.0241 0.02415 0.0242 0.02486 0.0241 0.0247Weight increase* 6.97% 7.18%

Thrs = time in hours after t= 0, Td = time in days after t= 0* average increase of the weight compared to the weight at t=0

65

5


Figure 1. The change of weight of 6 Meniscus Arrows® during 28 days of immersion

The weight of the M.A.’s increased during the first 2 hours from an average of 0.0227gram (SD =fi

0.000163) to an average of 0.0248 gram (SD = 0.000337) or 9.16%. This is significant (p = 0,027). Afterfi

2 hours the weight remained stable at an average weight gain of 0.0017 grams or 7,18 % after 28

days (t = 17). The average weight varied in this period from 0.024 gram to 0.025 gram. This variation

is not significant.fi

Results of the swelling experiment (Figures 2 – 5, Table 2)

Figure 2. Example of the shape and measurement of Arrow 1 at t2 or 2 hours after the startof the experiment and being submerged for 2 hours.

66

Chapter 5

A subtle increase of the core diameter of the arrows in time was noted. The average diameter

increased with 0.01mm, or 1.01%, from 1.22mm (standard deviation (SD) = 0.0089) at t1=0, to

1.23mm at t13 (t1+18 days) (SD = 0.0098). This is significant (p = 0.031). (Table 2). fi

The barb-barb diameter decreased signifi cantly (p = 0.031) in time with 0.15mm, or 8.6%, from anfi

average of 1.74mm at t1, (SD = 0.0274) to 1.59mm (SD = 0.01897) at t13 (Table 2).

Figure 3. The change of the core diameter of 6 Meniscus Arrows® during 18 days of immersion

Figure 4. The change of the barb – barb diameter of 6 Meniscus Arrows® during 18 days of immersion

67

5


DISCUSSION

The application of biodegradable osteofi xation devices could have several advantages over metallic fi

implants.

Mechanical factors like erosion of the opposite cartilage, if inserted in a joint surface and stress

shielding18–22 as well as scatter in computed tomography and magnetic resonance imaging,23,24 and

the possibility of evoking allergic and carcinogenic reactions25 induced the need of a subsequent

removal operation of the metallic devices in most circumstances. This second operation could be

avoided, using biodegradable rods, pins, plates or screws.1,8,18-22,26

Distension could be another advantage of intra-osseous placed biodegradable osteofixationfi

implants, leading, theoretically, like the mechanism of expanding bolts in a solid material, to an

increased fi xation in bone. fi

M.A.’s, designed for repairing meniscus tears, could potentially be used to fix the cartilage-bonefi

fragments in the treatment of the Osteochondritis Dissecans disease26 or other small bony fragments

in fracture surgery. If they distend substantially, the pull-out force and fixation in the bone would fi

considerably increase.

In literature swelling of biodegradable polymers is mostly related to an increase of weight. On the

Figure 5. Example of the change of shape and measurement at t13: Arrow 1, 18 days after the startof the experiment.

68

Chapter 5

contrary, the mechanical distension has been scarcely measured.5,12–15 In two papers the increase

of volume and the macroscopic measurement of the dimension along a ruler was defined asfi

swelling11,16, one without giving the exact data of the distention.11 In another paper the dimensional

change in vitro was measured and determined as was the weight.17 These last three papers

described hydrogels. Finally, Hasirci measured in his study the change of size of rods of reinforced

poly (lactide-co-glycolide) during the in vitro part of the experiment.4 However, the experimental

procedure itself is not fully transparent to us.

In the present study the change of weight of the 6 M.A.’s has been pursued during 28 days (Table 1,

Figure 1). This period is the expected initial consolidation time for fractures with small fragments in

humans.

In the first 2 hours the weight increased rapidly and signififi cantly with 9.16%, remaining stablefi

afterwards at 7.18% weight gain.

The core diameter, however, increased gradually and slightly (0.01mm, or 1.01%), but significantly,fi

during the whole period. This reveals an evident discrepancy in this experiment between the

increase of the weight and the dimensions.

In contrast, in literature much higher swelling (or weight gain) ratios are mentioned of differentffff

polymers, e.g. more than 30% of a cross-linked poly (propylene fumarate) PLA/PGA 70/30 complex at

28 days4, 260% at 12 hours of a phosphate containing poly-ethylene glycol methacrylate polymer16

and 310% at 12 weeks for oligo(poly(ethylene glycol) fumarate).17 The origin of this discrepancy

between our results and the data from literature is not clear. Is it only related to this specific DLPLAfi

complex, to the measure method as well or other influences?fl

We assume, however, that the 0.01 millimeter or 1.01% increase of the core diameter in 18 days will

not have any impact on the mechanical performance in 28 days, because the increase is minimal

and very gradual (Figure 3). Furthermore, taking the trend of the data into account, it is not to be

expected that this pattern will alter in 10 more days and in vivo the progressive consolidation of the

fixed fragments will decrease the demands on the mechanical performance of the fifi xation.fi

In contrast the inter-barb diameter decreased steadily in 18 days 0.15 millimeter, or 8.6%, caused by

a curling of the barbs (Figures 2,4,5).

Hypothetically, this can be explained by a tendency of the material to return to its original rod like

shape during degradation, i.e. a state before the barbs were created.

These barbs are fabricated by cutting a rod of PLLA during the plastic deformable phase of the raw

material, followed by bending the cut material externally (Figure 2).

Theoretically this decrease in outer diameter and shape would imply that the hold of biodegradable

devices like M.A.’s will not increase like expanding bolts as a function of time, but on the contrary

decrease. Nevertheless, it is limited to less than 10% in 18 days and since the consolidation process

of the fragments in the clinical situation will continue in time the mechanical demands on the

fixation of the fragments will decrease. These efffi ects can neutralize each other and therefore the ffff

clinical impact is not obvious.

69

5


CONCLUSION

Swelling of solid biodegradable polymers as often mentioned in literature is, judging from the

results of our study, more related to an increase of weight by the uptake of water than to a swelling

or distention of the devices.

Therefore, the hold in bone of these biodegradable polymers will not increase like the increased

fixation of an expanding bolt in a solid material. Theoretically the tendency of the material tofi

retract into its original shape, as found in our experiment, could influence the fifl xation capacities in fi

a negative sense. However, the clinical importance of this phenomenon is not clear as the fragment

will gain progressively stability due to the ongoing consolidation process. Besides, the absolute

values found in our tests are relatively small.

Acknowledgements

The help from Mr. G. ten Brink of the Department of Applied Physics of the University of Groningen,

the Netherlands, who prepared the electron micrographs and from Mrs. M.B.M. van Leeuwen of the

Department of Biomaterials of the University Medical Centre Groningen, the Netherlands, for her

contribution in the weight measurements are gratefully acknowledged.

Mr. J.G.M. Burgerhof from the Department of Epidemiology, University Medical Centre Groningen,

the Netherlands, was of crucial help during the statistical analysis of the data.

70

Chapter 5

References

1. Bos RRM. (1989) Poly(L-Lactide) osteosynthesis. Development of bioresorbable bone plates and screws.Thesis University of Groningen, pp 7–9

2. Williams DF, Mort E. (1977) Enzyme-accellerated hydrolysis of polyglycolic acid. J Bioeng 1: 231–238

3. Williams DF. (1979) Some observations on the role of cellular enzymes in the in-vivo degradation of polymers. Spec Tech Publ 684: 61–75

4. Hasirci V, Lewandrowski K, Gresser JD, Wise DL, Trantolo DJ. (2001) Versatility of biodegradable biopolymers:degradability and an in vivo application. J Biotechnol 30;86(2):135-50

5. Yoon JJ, Park TG. (2001) Degradation behaviors of biodegradable macroporous scaffolds prepared by gasfffffoaming of effervescent salts. J Biomed Mater Res 55(3):401–408ffff

6. Pietrzak WS, Sarver DR, Verstynen ML. (1997) Bioabsorbable polymer science for the practicing surgeon. JCraniofac Surg 8(2): 87–91

7. Pego AP, Van Luyn MJ, Brouwer LA, van Wachem PB, Poot AA, Grijpma DW, Feijen J. (2003) In vivo behaviorof poly(1,3-trimethylene carbonate) and copolymers of 1,3-trimethylene carbonate with D,L-lactide or epsilon-caprolactone: Degradation and tissue response. J Biomed Mater Res 67A(3):1044–1054

8. Bergsma EJ, de Bruijn WC, Rozema FR, Bos RRM, Boering G. (1995) Late degradation tissue response to poly(L-lactide) bone plates and screws. Biomaterials 16(1):25–32

9. Tschakaloff A, Losken HW, von Oepen R. (1994) Degradation kinetics of biodegradable DL-polylactid acid ffbiodegradable implants depending on the site of implantation. Int J Oral Maxillofac Surg 23:443–445

10. Sevastjanova NA, Mansurova LA, Dombrovskova LE, Slutskii LI. (1987) Biochemical characterisation of connective tissue reaction to synthetic polymer implants. Biomaterials 8:242–247

11. Wang Y, Kim YM, Langer R. (2003) In vivo degradation characteristics of poly(glycerol sebacate). J Biomed Mater Res 66A(1):192–197

12. Dijkhuizen-Radersma van R, Roosma JR, Kaim P, Métairie S, Péters FLAMA, Wijn de J, Zijlstra PG, Grootde K, Bezemer JM. (2003) Biodegradable poly(ether-esther) multiblock copolymers for controlled releaseapplications. J Biomed Mater Res 67A:1294–1304

13. Yang Z, Zhang Y, Markland P, Yang VC. (2002) Poly(glutamic acid) poly(ethylene glycol) hydrogels preparedby photoinduced polymerization: Synthesis, characterization, and preliminary release studies of protein drugs. J Biomed Mater Res 62(1):14-21

14. Bezemer JM, Oude Weme P, Grijpma DW, Dijkstra PJ, van Blitterswijk CA, Feijen J. (2000) Amphiphilicpoly(ether ester amide) multiblock copolymers as biodegradable matrices for the controlled release of proteins. J Biomed Mater Res 52(1):8-17.

15. Tanahashi K, Jo S, Mikos AG. (2002) Synthesis and characterization of biodegradable cationic poly(propylenefumarate-co-ethylene glycol) copolymer hydrogels modified with agmatine for enhanced cell adhesion.fiBiomacromolecules 3(5):1030-1037

16. Wang DA, Williams CG, Li Q, Sharma B, Elisseeff JH. (2003) Synthesis and characterization of a novelffdegradable phosphate-containing hydrogel. Biomaterials 24(22):3969–3980

17. Shin H, Quinten Ruhe P, Mikos AG, Jansen JA. (2003) In vivo bone and soft tissue response to injectable, biodegradable oligo(poly(ethylene glycol) fumarate hydrogels. Biomaterials 24(19):3201–3211

18. Cugat R, Garcia M, Cusco X, Monllau JC, Vilaro J, Juan X, Ruiz-Cotorro A. (1993) Osteochondritis Dissecans: A historical Review and its Treatment with cannulated screws. Arthroscopy 9(6):675–684

19. Wagner H. (1976) Die Kliniek der Knorpeltransplantation bei der Osteochondrosis dissecans. Hefte zur Unfallheilkunde 127:118–125

20. Gschwend N, Munzinger U, Löhr J. (1981) Unsere extraarticuläre Dissecatverschraubung beiOsteochondrosis dissecans des Kniegelenkes. Orthopäde 10:83–86

71

5


21. Johnson LL, Uitvlugt G, Austin MD, Detrisac DA, Johnson CJ. (1990) Osteochondritis Dissecans of the Knee:Arthroscopic Compression Screw Fixation. Arthroscopy 6(3):179–189

22. Kivistö R, Pasanen L, Leppilahti J, Jalovaara P. (2002) Arthroscopic repair of osteochondritis dissecans of the femoral condyles with metal staple fixation: a report of 28 cases. Knee Surg Sports traumatol Arthrosc fi10:305–309

23. Scher N, Poe D, Kuchmir F, Reft C, Weichselbaum R, Panje WR. (1988) Radiotherapy of the resected mandible following stainless steel plate fi xation. Laryngoscope 98: 561–563fi

24. Castillo MH, Button TM, Homs MI, Pruett CW, Doerr R. (1988) Effects of radiation therapy on mandibular ffffreconstruction plates. In: Trans 41st Ann Cancer Symp. The Society of Surgical Oncology, New Orleans,Louisiana, U.S.A., p144

25. Black J. (1988) Orthopedic Biomaterials in Research and Practice. Churchill Livingstone New York, Edinburgh London, Melbourne pp 292–302

26. Wouters DB, Bos RRM, Mouton LJ, van Horn JR. (2004) The Meniscus Arrow® or metal screw for treatmentof Osteochondritis dissecans? In Vitro comparison of their effectiveness. Knee Surg Sports TraumatolffffArthrosc 12: 52–57

72

73

6CHAPTER

Is the pull-out force of the Meniscus Arrow® in bone aff ected by the inward curling of the barbs during ff

biodegradation? An in vitro study.

D.B. Wouters1,3

J.G.M. Burgerhof2ffR.R.M. Bos3

J.Th.M. de Hosson4

1 Department of General-, Arthroscopic Surgery and Traumatology, TweeSteden Hospital, Tilburg, The Netherlands,2 Department of epidemiology, University Medical Centre Groningen, Groningen, The Netherlands,3 Department of Oral and Maxillofacial Surgery, University Medical Centre Groningen, Groningen, The Netherlands,4 Department of Applied Physics, University of Groningen, The Netherlands.

Med Sci Monit. 2009 Apr;15(4)

74

Chapter 6

ABSTRACT

Background: Inward curling of the barbs of Meniscus Arrows during degradation was observed in aprevious study, in which swelling, distention, and water uptake by Meniscus Arrows was evaluated. This change of confi guration could have consequences with respect to anchorage capacity in bone.fi

Material/Methods: Eight non-degraded Meniscus Arrows in the original confi guration were pulled fiout of thawed, fresh-frozen human femoral condyle, and pull-out force was measured and compared with that of 6 Meniscus Arrows after 31 days of degradation under controlled conditions.

Results: No significant difffi erence was found between the 2 groups with respect to the required pull-ffffout force (t test), the distribution of the data, or the interaction between degradation and location,as evaluated by Mann-Whitney test, and no significant difffi erence was found between the 2 groups ffffwith respect to the degradation state or position in the condyles, as evaluated by 2-way analysis ofvariance.

Conclusions: Our results indicate that the decrease in barb-barb diameter during the first month of fidegradation of the Meniscus Arrows has no significant efffi ect on the tensile pull-out force requiredfffffor removal from human femur condyle. Further research should be undertaken to examine whetherthe same is true for other biodegradable devices with barbs.

75

6

Is the pull-out force of the Meniscus Arrow® in bone aff ected by the inward curling of the barbs?

BACKGROUND

Metallic fi xation devices such as screws,fi 1,2 pins3–5 and staples6 are generally used to fi x small bony fi

fragments in fracture treatment. Most require a second procedure for removal. When inserted into

joints, removal is, in most circumstances, obligatory to prevent damage of the opposing cartilage.

Even when embedded under the cartilage surface, protrusion can occur.7,8 Removal prevents

scattering during computed tomography or magnetic resonance imaging and also prevents

localized tissue reaction9–11

The use of biodegradable devices obviates the need for removal and researchers have spend the

last three decades in the development of appropriate materials and devices.

At present, diff erent biodegradable polymers, such as polydioxanone, polyglycolic acid, andffff

polylactic acid and their co-polymers, combinations or blends are available. Biodegradable screws

or pins are applied for small fragment fixation in fracture treatmenfi t or treatment of osteochondritis

dissecans. Screws and pins have specifi c advantages and disadvantages. Biodegradable screws fi

produce the required compression, but their current minimal head diameter of 3 mm is considerable

for the often fragile fragments. In addition, at least 2 devices are necessary to achieve rotational

stability. Furthermore, during the degradation process, wear of the opposing cartilage and local

tissue reactions can occur.12,13 Biodegradable pins do not share these disadvantages, but do not

provide compression.14,15

The Meniscus Arrows (MA; (ConMed Linvatec Ltd, Tampere, Finland) is a biodegradable nail-

like device composed of L-DL(80/20) self-reinforced lactide copolymer with a very small core

diameter (1.0mm), barbs and a small, fl at head (Figure 1). Originally designed to mend ruptured fl

menisci, the anchorage of MA’s in bone was examined in previous in vitro study to evaluate the

potential application in fi xing small cartilage-bone fragments in the treatment of osteochondritisfi

dissecans and small fragment fracture surgery16 Theoretically, biodegradable polymers swell during

degradation, which could prove an additional advantage for the use of biodegradable implants in

fracture fi xation. Their hold in bone would increase like an expanding bolt. For gels this distentionfi

Figure 1: the Meniscus Arrow®

76

Chapter 6

is variable17–21 and we found that the swelling of MA’s is negligible with respect to this mechanical

aspect.22 In the same study we observed consistent inward curling of the barbs of all MA’s during

the degradation process (Figure 2).22 This phenomenon could result in a decreased hold in bone.

Therefore, the aim of the present study was to evaluate the potential influence of this inward curlingfl

of the barbs on the required pull-out force from the bone.

Figure 2: a: a non degraded Meniscus Arrow® b: after 31 days of immersion in a sterile saline solution

77

6


MATERIAL AND METHODS

Group 1 (non- degraded MA’s) consisted of eight MA’s, retrieved directly from the packing. In group

2 (degraded MA’s), six MA’s were submerged over a period of 31 days in a sterile phosphate bufferedffff

saline (Pharmacy of the University Medical Centre, Groningen, The Netherlands) at 37º C. The

solution was changed twice a week under sterile conditions. A degradation period of 31 days was

selected because this period is the expected initial consolidation time for small fragment fractures

in humans.

Figure 3: sequence of pulling out from the femur condyles. (see for color image: page 142)

Figure 4: a: start of the extraction of the fi rst Meniscus Arrow® from hole 1fib: start of the extraction of the second Meniscus Arrow® from hole 2


78

Chapter 6

For the experiment, 18 holes of 1.0mm in diameter were drilled into both condyles of a thawed,

previously fresh frozen human cadaver femur, to exclude the influence of potential difffl erences of ffff

local bone density (Figure 3). Alternating non-degraded and degraded MA’s, were then via a hole in

an extracting device and gently hammered into each drill hole (Figure 4a). Standard hand-insertion

instruments were used. The MA’s were subsequently pulled out, using an Instron 1195 draw bench

(Instron, 825 University Ave. Norwood, MA 02062-2643, USA). The load cell measured 1000newtons

(N) maximum, with a scale set at 0N – 200N. The extraction speed applied to the device was 5mm

/ min.

Statistical analysis

The results were statistically analyzed by t-test, Mann-Whitney test and 2-way analysis of variance.

RESULTS

In group 1, the peak required pull-out force of the eight non-degraded MA’s ranged from 12.82N

to 41.19 N with an average ±standard deviation of 28.61N±11.17 (table 1). In group 2, the required

pull-out force for degraded MA’s ranged of 12.80N to 34.22N, with an average of 21.83N±7.63N.

The average extraction force of the new, non-degraded MA’s and the degraded MA’s did not differffff

significantly (t-test: fi P= .23, 95% confidence interval for the difffi erence in means: [ - 4.8 ; 18.4]). Inffff

addition, the spread of the results did not differ signififfff cantly (Leven\’s testfi P=.16). Results of 2-way

analysis of variance showed no significant difffi erence between degradation and location (ffff P= .7),

between degraded or non-degraded MA’s (P= .15) or between location on the lateral- in the lateral

or medial condyle (P=.14).

DISCUSSION

The use of biodegradable devices is advantageous if the fi xation lasts long enough to allow for fi

consolidation with minimal damage to the fi xed bony fragments and if the degradation occurs fi

without adverse eff ects.ffff

The Meniscus Arrow is one such potential fixation device,fi 14,15,22 but the inward curling of the barbs,

encountered in our previous study22 could lead to decreased anchorage in the bone over time. We

found no other reports describing this curling or its potential effect on the hold of MA’s or other ffff

biodegradable devices. This provided the impetus for the present study.

Although the inward curling of the barbs after a degradation period of 31 days suggests that this

could lead to a decrease of the anchorage to a solid material such as bone, this is not confirmed in fi

the present study. Therefore, this phenomenon does not appear to interfere with the application of

MA’s in fixing small bony fragments in fracture surgery or in osteochondritis dissecans.fi

79

6


CONCLUSIONS

The inward curling of the barbs of MA’s during degradation did not affect the anchorage in bone in ffff

our tests.

Whether other biodegradable devices with barb-like restraints deform spontaneously during

degradation as will require additional research.

80

Chapter 6

References



3. Smillie IS. Treatment of osteochondritis dissecans. J Bone Joint Surg (B) 1957;39: 248–2604. Anderson A, Lipscomb AB, Coulam C. Antegrade curettement, bone grafting and pinning of osteochondritis

dissecans in the skeletally mature knee. Am J Sports Med 1990;18(3):254–2615. Guhl JF. Arthroscopic treatment of Osteochondritis Dissecans. Clin Orth 1982;167:65–746. Kivistö R, Pasanen L, Leppilahti J, Jalovaara P. Arthroscopic repair of osteochondritis dissecans of the

femoral condyles with metal staple fixation: a report of 28 cases. Knee Surg Sports Traumatol Arthrosc fi2002;10:305 – 309

7. Bobic V. Cover photograph, Arthroscopy 2001;17(5)8. Kivistö R, Pasanen L, Leppilahti J, Jalovaara P. Arthroscopic repair of osteochondritis dissecans of the

femoral condyles with metal staple fixation: a report of 28 cases. Knee Surg Sports Traumatol Arthrosc fi2002;10:305 – 309

9. Scher N, Poe D, Kuchmir F, Reft C, Weichselbaum R, Panje WR. Radiotherapy of the resected mandible

following stainless steel plate fi xation. Laryngoscope 1988;98:61–563fi10. Castillo MH, Button TM, Homs MI, Pruett CW, Doerr R. Effects of radiation therapy on mandibular ffff

reconstruction plates. In: Trans 41st Ann Cancer Symp. The Society of Surgical Oncology, New Orleans,Louisiana, U.S.A. 1988; 144

11. Black J. Orthopedic Biomaterials in Research and Practice. Churchill Livingstone New York, Edinburgh London, Melbourne 1988; p 292–302

12. Kumar A, Malhan K and Roberts SNJ. Chondral Injury from Bioabsorbable Screws after Meniscal Repair. Arthroscopy 2001;17(8):34


14. Weckström M, Parviainen M, Kiuru MJ, Mattila VM, Pihlajamäki HK. Comparison of BioabsorbablePins and

Nails in the Fixation of Adult Osteochondritis Dissecans fragments of the Knee: an Outcome of 30 Knees.Am J Sports Med 2007;35(9):1467-1477

15. Wouters DB, Bos RRM, van Luyn MJA. “Should in the treatment of Osteochondritis Dissecans biodegradableor metallic fi xation devices be used? A comparative study in goat knees.” J Biomed Mater Res B ApplfiBiomater. 2008 Jan;84(1):154–164

16. Wouters DB, Bos RRM, Mouton LJ, van Horn JR. The Meniscus Arrow® or metal screw for treatment of Osteochondritis dissecans? In Vitro comparison of their effectiveness. Knee Surg Sports Traumatol Arthrosc ffff2004;12:52–57

17. Hasirci V, Lewandrowski K, Gresser JD, Wise DL, Trantolo DJ. Versatility of biodegradable biopolymers: degradability and an in vivo application. J Biotechnol 2001 30;86(2):135-50

18. Pego AP, Van Luyn MJ, Brouwer LA, van Wachem PB, Poot AA, Grijpma DW, Feijen J. In vivo behavior of poly(1,3-trimethylene carbonate) and copolymers of 1,3-trimethylene carbonate with D,L-lactide or epsilon-caprolactone: Degradation and tissue response. J Biomed Mater Res. 2003 Dec 1;67A(3):1044–1054


20. Wang DA, Williams CG, Li Q, Sharma B, Elisseeff JH. Synthesis and characterization of a novel degradable ffphosphate-containing hydrogel. Biomaterials 2003;24(22):3969–3980

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21. Shin H, Quinten Ruhe P, Mikos AG, Jansen JA. In vivo bone and soft tissue response to injectable, biodegradable oligo(poly(ethylene glycol) fumarate hydrogels. Biomaterials 2003;24(19):3201–3211

22. Wouters DB, Bos RRM, De Hosson JTh.. Swelling of solid biodegradable implants during degradation. An in-vitro study with Meniscus Arrows®. Knee Surg Sports Traumatol Arthrosc 2007;15:1204–1209

82

83

7CHAPTER

Pull-out tests, comparing Meniscus Arrows® and SmartNails®, followed by a prospective series of five clinicalfi

cases applying Meniscus Arrows® as fi xation devices of fiosteochondral fragments in the human knee.

D.B. Wouters1,4

J.G.M. Burgerhof2ffJ.Th.M. de Hosson3

R.R.M. Bos4

1 Department of General-, Arthroscopic Surgery and Traumatology, TweeSteden Hospital, Tilburg, the Netherlands,2 Department of epidemiology, University Medical Centre Groningen, Groningen, the Netherlands,3 Department of Applied Physics, University of Groningen, Groningen, the Netherlands,4 Department of Oral and Maxillofacial Surgery, University Medical Centre Groningen, Groningen, the Netherlands.

84

Chapter 7

ABSTRACT

The aim of this study was to compare the hold in bone of Meniscus Arrows® and Smart Nails®. After

in vitro tests the clinical application of the selected device was performed. Straight pull-out tests

were per formed to analyse the hold in bone of single Meniscus Arrows® and Smart Nails® and,

tangentially, to assess the fi xation capacity of three devices of each kind in bone blocks. The results fi

were statistically analyzed using the Student T- and the Mann-Whitney test, the Anova two-way

test and the Levene test. Because no significant difffi erence was noted between the hold of both ffff

nails, we choose the thinner Meniscus Arrow® as fi xation device in a prospective, consecutive patientfi

series of two patients with a symptomatic osteochondritis dissecans fragment and three patients

with an osteochondral fracture of a femur condyle, fixed twice with two Meniscus Arrowsfi ®, one

time with three and twice with fi ve, according to the size of the fragment. All procedures started fi

arthroscopically, four times conversion followed into an arthrotomy, due to the size of the fragment.

The cartilage margins were glued with Tissuecoll®.

Results: all fi ve fragments consolidated and at an average follow-up period of fifi ve years (ranging fi

from two to nine years) no pain, effusion, locking, restricted range of motion or signs of arthrosis ff

were reported.

We conclude, that based on the results from in vitro pull-out tests and available clinical studies,

Meniscus Arrows® and Smart Nails® are likely to perform adequately in the treatment of Ostechondritis

Dissecans disease and osteochondral fractures in the knee. They both provide the advantage of

one stage surger y. However, the smaller diameter of the Meniscus Arrows® suggests it should be

preferred for this indication. In this study, MA’s allowed undisturbed healing of osteochondral

lesions of the knee in fi ve patients without complications.fi

Key Words: biodegradable – fixation devices – Meniscus Arrowsfi ® - osteochondral fragments –

osteochondritis dissecans

85

7

Pull out tests, comparing Meniscus Arrows® and Smart Nails®, followed by a clinical series

INTRODUCTION

Compressive metallic fixation devices such as screwsfi 1,2, non compressive pins or Kirschner wires,3,4,5

or staples6 are used to fix the fragments in the treatment of Osteochondritis Dissecans (OCD). fi

However, in most cases, they have to be removed during a second procedure to prevent damage to

the opposite cartilage.

Devices have been developed to be inserted and embedded under the cartilage surface in an effort ffff

to prevent cartilage damage, but they can cause damage as well, if protrusion occurs after all7. An

additional long term disadvantage of the permanent implantation of metallic devices is scattering

during CT or MRI scanning and some metals, such as chromium, nickel, gold, platinum, and

cobalt can evoke local allergic reactions like eczema. Chromium, nickel and cobalt are also potent

carcinogens in animals.8,9,10

Several groups have explored the use of autologeous cartilage bone plugs as fixation devices.fi

However, donor site morbidity, the absence of producing substantial compression and failure of

the re-integration process at the interface of donor and recipient cartilage make this procedure less

than optimal.11,12

Use of a biodegradable fixation device would prevent radiological scattering, lacking the other, fi

previously mentioned disadvantages and renders a removal operation unnecessary.

During the last four decades, intensive research has been conducted to develop an appropriate

material and device. Biodegradable pins and screws of polydioxanon, polyglycolic acid and

polylactic acid, their copolymers, combinations or blends are now in use for small fragment fixationfi

in fracture or OCD treatment.

Each of these materials and devices, while useful, has significant shortcomings. Biodegradable fi

screws produce the required compression, but their current minimal head diameter (Ø) of 3mm, in

combination with the necessity to insert at least two devices to obtain rotational stability cause a

considerable damage of the fragile fragments. Furthermore, during the degradation process, wear of

the opposite cartilage still occurs.13–17 In an attempt to address this problem, more rapidly degrading

materials were created. Unfortunately, though, sinus formation is observed when screws of these

materials are used.17 Biodegradable pins share this disadvantage to a smaller extent, but cannot give

adequate compression. This compression is generally considered as a necessity for healing.1–6,14–21

Biodegradable barbed nails such as Smart Nails® (SN’s, ConMed Linvatec Ltd Tampere, Finland),

1.5mm in Ø, have currently been used for fragment fixation in patients with OCD fragments and, fi

according to these papers, perform better than pins.19,21

The composition of Meniscus Arrows® (MA’s, ConMed Linvatec Ltd Tampere, Finland) and SN’s

is equivalent; both are manufactured from the same self reinforced poly-L-DL (80-20) lactide

copolymer.

MA’s with their tiny head and an even smaller core Ø of 1.1mm combined with a length of 16mm

could potentially act as small fragment fixation devices as well. The hold in bone was evaluated fi

86

Chapter 7

during in-vitro research, showing a considerable force, more than 60Newton (N), which was required

to pull the MA’s out of a human femoral condyle.20

The smaller diameter of the MA’s, compared to the SN’s would cause less damage to the fragments,

or would permit the use of more devices with equivalent or less damage.

The purpose of this study was to perform in vitro pull out tests comparing the hold in bone of single

MA’s and SN’s and of bone blocks, fixed with three devices of each kind.fi

Second, to conduct a clinical prospective study on patients with intact osteochondritis dissecans

fragments and osteochondral fractures of femoral condyles, using these devices, showed to be the

most adequate for this indication, according to the results of these tests.

SUBJECTS AND METHODS

To compare the hold in bone of MA’s and SN’s, the experiment was divided in two parts.

First, three MA’s with a length of 16mm and three SN’s with a length of 20mm were successively

pulled out of a thawed, fresh frozen human condyle, clamped in an Instron 1195 draw bench. The

scale was set at 0 –200N, the time 0 – 300 sec. The extraction speed was 5mm / min. The standard

hand instruments were used to create the holes and to insert the devices (Figure 1a,b). Subsequently

they were pulled out (Figure 1c).

Second, three bone blocks, each with three MA’s or SN’s were fi xed at the condyle and were pulled fi

out as well (Figure 1d), mimicking the situation in vivo. The results are depicted in table 1.

The Student T-test and the Mann-Whitney test were used for the single MA’s and SN’s. For both

groups the Anova two way tests after the logarithmic transformation and the Levene test of equality

Meniscus Arrow Smart nail

no. result* no result*1 59 1 532 68 2 663 78 3 64Average: 68 Average: 61st. dev.: 9.5 st. dev.: 7

bone block + 3 Arrows bone block + 3 nails

no result* no result*1 110 1 952 148 2 1153 108 3 55Average: 122 Average: 88st. dev.: 22,5 st. dev.: 30,6

*data in Newtons

Table 1: results

87

7


of error variances was applied.

Based on the outcome of these tests, we chose to utilize the smaller MA’s (Figure 6) for the clinical

study.

In the OCD group, two women, 20 years (patient #1, right knee) and 38 years old (patient #2, left

knee) with a symptomatic intact OCD fragment of the medial condyle were operated between 1999

and 2001, with a follow-up period of 9 and 7 years. The size of the fragment varied from 20x25mm

in diameter in patient #1 to 30x30mm in patient #2 (table 2). Surgery was initiated arthroscopically

in both cases. For patient #1, a fully arthroscopic procedure was performed. A central drill hole

was made in the still attached fragment with intact covering cartilage (Figure 2a). Pressure on the

Figure 1: a: Meniscus Arrow® handsetb: Smart Nail® handset

c: extraction of the fi rst Meniscus Arrow®, note the drill hole indicating wires for the fi next extractionsd: the bone block with 3 MA’s fi xed before being pulled offfi , mimicking shear forcesffff

88

Chapter 7

Figure 2: patiënt #1: a: central drilling; b: after fi xation with 3 Meniscus Arrows® and release of the ourniquet, fi

note the bleeding from a drill hole;patient #2: c: insertion of a Meniscus Arrow® from the lateral portal in the fragment after debridement and a spongeous bone transplantation; d: the final situationfi

Table 2: the patiënt group

patient nr. diagnosis age side, condyle

number of M.A.’s f.u. (years) fragment size*

1 OCD 20 right, medial 3 9 20 x 25

2 OCD 38 right, medial 5 8 30 x 30

3 osteochondral # 11 right, lateral 2 2 20 x 30

4 osteochondral # 15 right, lateral 2 2 25 x 30

5 osteochondral # 20 left, lateral 5 2 25 x 30

average 20,8 3 5 24 x 29

* size in mm.

fragment did not reveal debris, indicating the presence of underlying necrosis, emanating from the

drill hole. It was therefore concluded, that no signifi cant necrosis was present in the sub-fragmental fi

space. A compressive fi xation with three MA’s, 16mm in length, was performed after three additional fi

drill holes were made to allow introduction of locally bone marrow cells to promote healing. After

releasing the tourniquet, bleeding was observed from the drill holes (Figure 2b).

In patient # 2, the arthroscopy was converted into a small arthrotomy, due to fragment size, the


89

7


presence of infra-fragmental necrosis (the fragment was already partially loose at first sight and fi

necrosis and fibrosis was observed in the dissecat bed) and the necessity for spongeous bone fi

transplantation in this case. Also proper reduction and the orientation, required to insert the devices

(Figure 2c) necessitated the conversion. After debridement of the bottom of the crater, spongeous

bone was harvested with a punch from the ileac crest, and placed between the fragment and

the recipient bone. The fragment was reduced and temporarily fixed with two K-wires, 1mm in Ø, fi

inserted from diff erent angulations, perpendicular to the cartilage surface.ffff

They were subsequently exchanged by two MA’s with a length of 16mm, followed by the drilling

and

insertion of an additional three MA’s, to provide a spread adequate compression (Figure 2d).

The second group of patients (# 3,4,5) consisted of two children of 11 and 15 years old and one adult

of 20 years old with a traumatic osteochondral fracture, one time sized 20x30mm and twice 25mm

x 30mm in Ø (table 2). The operation was performed within two weeks after the trauma. Tissuecoll®

(Baxter–Immuno, Vienna, Austria) was applied in the defect to glue the cartilage borders. The bony

fixation was performed using two MA’s (Figures 3 a-e, 4a - d) in patients # 3 and # 4 and fifi ve MA’s infi

patient # 5 (Figure 5a - e). Both the arthrotomy as the arthroscopy portals were closed in layers in

all patients.

Postoperatively a plaster splint was applied for two weeks, followed by a hinged brace for four

weeks. A second look arthroscopy was carried out in this group six weeks postoperatively to assess

the reliability of the fixation.fi

Gradual progressive weight bearing was allowed in the next four weeks.

Figure 3: patient # 3: a: arthroscopical view of the fragment, b: aspect of the defect in the lateral femur condyle, c: the fragment, d: fixation with the fifi rst Meniscus Arrow®, fi e: the final situationfi

43)(see for color image: page 14

90

Chapter 7

RESULTS (table 1)

The in vitro tests The pull-out tests showed values of the single MA’s varying between 59 Newton

(N) and 78N with an average of 68 N. The single SN’s required a value between 53N and 66N, the

average was 61N. The required forces in the bone blocks group to distract the blocks with the MA’s

from the condyle varied from 108N to 148N with an average of 122N, the blocks with SN’s fixationfi

needed 55N to 115N, with an average of 88N.

All information was combined into one statistical analysis. A two-way ANOVA was performed with

the type of nail (SN vs. MA) and condition (single nail or bone block) as fixed factors. A logarithmic fi

transformation of the required force was used to equalize variances. Levene’s test showed no

significant difffi erence in the variances of the transformed variable (P = 0.454). As expected, theffff

bone blocks, fixed with 3 devices, required signififi cantly more force to be distracted than the singlefi

devices (P = 0.007), but no significant difffi erence is found between the MA’s and the SN’s (P = 0.108).ffff

The clinical application After the initial healing period of three months, no effusions, locking, or painff

occurred in the two OCD patients during a follow-up period of seven and nine years respectively. The

patients did not experience restrictions in daily life or sports activities, although they spontaneously

avoided high impact sports as a precaution.

All three osteochondral fractures healed without sequelae. Within three months both children

returned to their previous activities. The adult patient (# 5) returned to previous activities in six

Figure 4: patient # 3: a,b,c: removal of the heads of the Meniscus Arrows® at 6 weeks after insertion. Note the smooth cartilage of the tibia plateau (a). d: patient # 4, 6 weeks after insertion

(see for color image: page 144)(see for color image: page 144)

91

7


months. During a second look arthroscopy at six weeks postoperatively, consolidation of the

fragment was found in all cases, with anatomical alignment of the cartilage. In patient # 3 (Figure

4a), the heads of the MA’s were visible and came incidentally loose at the junction between the head

and the first barb, after some traction was applied with an arthroscopic forceps, while evaluating the fi

devices. The heads were removed from the joint (Figure 4b-c).

In patient # 4 the heads of the MA’s were still embedded under the cartilage surface and were stable

(Figure 4d).

No MA heads were seen in patient # 5 at arthroscopy (Figure 5e).

No wear or damage was observed in the cartilage of the opposite tibia plateau of any of these three

patients (Figures 4,5).

Figure 5: Patient # 5: a: the loose fragment b: the defect c: measuring 25mm x 35mm d: fi xation with Tissuecoll® and fifi ve Meniscus Arrows®fi e: the result at six weeks postoperative

(see for color image: page 144)(see for color image: page 144)

92

Chapter 7

DISCUSSION

In the last five decades, reduction of OCD fragments and fi osteochondral fractures, if remaining intact,

followed by rotation stable fixation with compression, has been generally accepted as optimalfi

treatment. A spongeous bone transplantation and debridement of the dissecat bed, if necrosis is

found, should also be considered in case of osteochondritis dissecans.1–6,13–20

Use of biodegradable devices provides the possibility to repair these conditions with a single

procedure, avoiding the need of a removal operation. On the other hand, the application of

biodegradable screws has potential disadvantages such as damage to the opposite cartilage from

exposed screw heads and, if rapidly degrading material has been used, sinus formation.13–17

Small barbed pins such as MA’s or SN’s have been shown to fi x compressive as well as, and performfi

better than smooth pins to fi x the bony part of the fragment without causing sinus formation.fi 19,20,21

In this study no statistical difference between the required pull out forces of either the single MA’s ffff

and SN’s, or the bone blocks fi xed with three of each type of device, was demonstrated. Though fi

there may be a trend in favour of the MA’s, this is not significant (p = 0.108 at α = 0.05), according tofi

the corrected Anova test.

Given their equal mechanical behaviour, combined with reduced tissue damage and increased

options for number and arrangement of MA’s, permitted by their smaller diameter, we choose for

the MA’s for clinical application (Figure 6).

Figure 6: a: a Smart Nail® b,c: two Meniscus Arrows® in different directions to show the ffff head and barbs

93

7


During the second look arthroscopy no signs of chondral damage was noted, either at control

arthroscopy or during the follow-up period. This is consisted with the findings of Weckström et alfi 19

and Dines et al.21

They did not mention chondral damage in their series with SN’s as fixation devices as well. Thefi

number of reports of chondral damage while using MA’s in meniscal surgery is limited to only a

few case reports, despite their frequent and worldwide numerous application in these orthopaedic

procedures.22,23 Case reports of chondral damage are also found in relation to other devices, so this

phenomenon is not restricted to MA’s.24,25

The MA heads were incidentally removed in patient # 3 during the second look arthroscopy, while

testing their stability with a forceps. In patient # 4, the heads were stable. In patient # 5 no heads

were found at all.

We have no explanation for these different fiffff ndings, performed at the same postoperative interval fi

at six weeks. The clinical course, however, was equivalent for all three patients.

The chondral part of the fragment in our three patients with osteochondral fractures was fixed withfi

Tissuecoll®, according to recommendations in the literature26,27 to promote cartilage healing. Good

and stable congruency was found during second look arthroscopy.

The OCD disease is a rare condition. Lindèn28 found an average incidence of one out of 10,000

patients under the age of 50 years in Malmö during a follow-up period of 10 years, with a maximum

incidence between the ages of 10 years and 20 years. Widuchowski et al29 reported a prevalence of

two percent in a sample of 25124 arthroscopies. Given the low prevalence of OCD in the population,

our series of patients is small as well.

However, the clinical outcome in our series with MA’s combined with the results in the clinical series

using the larger SN’s19,21 supports the application of both type of device.

The diameter of the MA’s is 26% smaller, compared to the SN’s (1.1mm versus 1.5mm, Figure 6).

The surface of the defect in the fragment for each MA is 0.79mm, compared to 1.77mm for each SN.

For three devices, a potential average for fi xation, the total damage to the fragment is 2.4mm vs. fi

5.3mm.

This combined with their frequent availability in hospitals for already established indications and

their excellent hold in bone, at least equal to that of the SN’s as demonstrated during our pull out

tests, makes the MA’s arguably the more advantageous device for the fixation of OCD fragments andfi

osteochondral fractures.

CONCLUSION

Based on the results from in vitro pull-out tests and available clinical studies, Meniscus Arrows® and

Smart Nails® are likely to perform adequately in the treatment of Ostechondritis Dissecans disease

and osteochondral fractures in the knee. They both provide the advantage of one stage surgery.

The smaller diameter of the Meniscus Arrows® suggests it should be preferred for this indication. In

94

Chapter 7

this study, MA’s allowed undisturbed healing of osteochondral lesions of the knee in five patients fi

without complications. For the benefit of the one stage operation, applying MA’s for this indication,fi

second look arthroscopy should only be performed if indicated.

95

7


References


2. Mackie IG, Pemberton DJ, Maheson M. Arthroscopic use of the Herbert screw in osteochondritis dissecans.J Bone Joint Surg 1990;72B:1076

3. Smillie IS. Treatment of osteochondritis dissecans. J Bone Joint Surg (B) 1957;39: 248–2604. Anderson A, Lipscomb AB, Coulam C. Antegrade curettement, bone grafting and pinning of osteochondritis

dissecans in the skeletally mature knee. Am J Sports Med 1990;18(3):254–2615. Guhl JF. Arthroscopic treatment of Osteochondritis Dissecans. Clin Orth 1982;167:65 – 746. Kivistö R, Pasanen L, Leppilahti J, Jalovaara P. Arthroscopic repair of osteochondritis dissecans of the

femoral condyles with metal staple fixation: a report of 28 cases. Knee Surg Sports Traumatol Arthrosc fi2002;10:305–309

7. Bobic V. Cover photograph, Arthroscopy 2001;17(5)8. Scher N, Poe D, Kuchmir F, Reft C, Weichselbaum R, Panje WR. Radiotherapy of the resected mandible

following stainless steel plate fi xation. Laryngoscope 1988;98:61–563fi9. Castillo MH, Button TM, Homs MI, Pruett CW, Doerr R. Effects of radiation therapy on mandibular ffff

reconstruction plates. In: Trans 41st Ann Cancer Symp. The Society of Surgical Oncology, New Orleans,Louisiana, U.S.A. 1988; p144

10. Black J. Orthopedic Biomaterials in Research and Practice. Churchill Livingstone New York, Edinburgh London, Melbourne 1988; p 292–302

11. Miura K, Ishibashi Y, Tsuda E, Sato H, Toh S. Results of arthoscopic fixation of osteochondritis dissecansfilesion of the knee with cylindrical autogenous osteochondral plugs. Am J Sports Med 2007;35(2):216–222

12. Kobayashi T, Fujikawa K, Oohashi M. Surgical fixation of MA’ssive osteochondritis dissecans lesion using ficylindrical osteochondral plugs. Arhtroscopy 2004;20(9):981–986

13. Kumar A, Malhan K and Roberts SNJ. Chondral Injury from Bioabsorbable Screws after Meniscal Repair. Arthroscopy 2001;17(8):34.


15. Scioscia TN, Giffi n JR, Allan CR, Harner CD. Potential complication of bioabsorbable screw fiffi xation for fiosteochondritis dissecans of the knee. Arthroscopy 2001 Feb;17(2):E7

16. Larsen MW, Pietrzak WS, DeLee JC. Fixation of osteochondritis dissecans lesions using poly(l-lactic acid)/poly(glycolic acid) copolymer bioabsorbable screws. Am J Sports Med 2005;33:68–76

17. Wouters DB, Bos RRM, van Luyn MJA. “Should in the treatment of Osteochondritis Dissecans biodegradableor metallic fi xation devices be used? A comparative study in goat knees.” J Biomed Mat Res (B) fi2008;84(1):154-64

18. Wouters DB, van Horn JR, Bos RRM. The use of biodegradables in the treatment of osteochondritis dissecans of the knee: fiction of future? Acta Orthop Belgica 2003; 69(2):175–181fi

19. Weckström M, Parviainen M, Kiuru MJ, Mattila VM, Pihlajamäki HK. Comparison of Bioabsorbable Pins and Nails in the Fixation of Adult Osteochondritis Dissecans fragments of the Knee: an Outcome of 30 Knees.Am J Sports Med 2007;35(9):1467-1477

20. Wouters DB, Bos RRM, Mouton LJ, van Horn JR. The Meniscus Arrow® or metal screw for treatment of Osteochondritis dissecans? In Vitro comparison of their effectiveness. Knee Surg Sports Traumatol Arthrosc ffff2004;12: 52–57

21. Dines JS, Fealy S, Potter HG, Warren RF. Outcomes of osteochondral lesions of the knee repaired with abioabsorbable device, Arthroscopy 2008;24(1):62–68

22. Seil R, Rupp S, Dienstm, Mueller B, Bonkhoff H, Kohn DM. Chondral lesions after arthroscopic meniscusffrepair using meniscus arrows. Arthroscopy 2000;16(7):E17

23. Ross G, Grabill J, Mc Devitt E. Chondral injury after meniscal repair with bioabsorbable arrows. Arthroscopy 2000; 16(7):754–756

24. Cohen SB, Anderson MW. Miller MD. Chondral injury after arthroscopic meniscal repair using bioabsorbable

96

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Mitek Rapidloc meniscal fi xation. Arthroscopy 2003;19(7):E24–26 fi25. Gliatis J, Kouzelis A, Panagopoulos A, Lambiris E. Chondral injury due to migration of a Mitek RapidLoc

meniscal repair implant after successful meniscal repair: a case report. Knee Surg Sports TraumatolArthrosc 2005 May;13(4):280-2

26. Dahmen G. Möglichkeiten der Fixation des Knorpeltransplantats – Naht oder Kleber. Z Orthop 1972;110: 719–726

27. Passl R, Plenk H. Ueber die Einheilung replantierter chondraler Fragmente. Unfallchirurgie 1986;12:194–199

28. Lindèn B. The incidence of Osteochondritis dissecans in the condyles of the femur. Acta orthop Scand1976;47:664-667

29. Widuchowski W, Widuchowski J, Trzaska T. Articular cartilage defects: study of 25,124 knee arthroscopies. Knee 2007 Jun;14(3):177-82

97

8CHAPTER

General Discussion

98

Chapter 8

Although short-term follow-up after resection of the fragment and debridement of the defect in

the treatment of osteochondritis dissecans (OCD) shows reasonable results,1,2 in the long run the

outcome deteriorates frequently, fi nally ending in arthrosis.fi 3,4,5,6,7,8

In general, OCD should be considered as a pseudarthrosis.9,10 Without measures to promote

healing, the disease mostly proceeds with gradual and progressive demarcation of the dissecat in

the adolescent and young adult. If in the adolescent conservative measures fail, or in the adult,

the therapy should be according to the general principles of the treatment of a pseudarthrosis, i.e.

debridement of the fracture ends, removal of the fi brous scar tissue, revascularisation measuresfi

like drilling and/or curettage, autologeous cancellous bone transplantation and stable, compressive

fixation of the fracture parts.fi

Stable, compressive, fixation can only be accomplished using implants like screws, staples or nail-fi

like devices with barbs. Fixation with smooth pins or wires does not give compression.

Cyclic but inconstant, compressive- and shear forces occur in the knee, due to muscle contractions,

fluctuations in weight bearing and moving of the joint. Compressive peak forces of three to fourfl

times body weight act on the knee joint.11,12

The contact surfaces of the motionless knee joint keep a reduced but not compressively fixed fi

fragment in place by the compressive force arising in the joint due to the ligaments- and muscle

action and body weight, as long as contact between both joint surfaces persists. If the load is

varying during movements or unloading of the limb, dislocating micro movements can inhibit the

consolidation of the fragment, leading to progression of the demarcation. This phenomenon plays

also a role when non-compressing pins are applied as fixation devices, which is an explanation of fi

the variability of the results in the literature.13–16 So, fi xation with compressive and stable implantsfi

should be preferred.9,10,17-25

Shear forces are extremely low in a knee joint; friction coefficients range from 0,005 to 0,023.ffi 25,26

For an individual with a body weight of 80kg the maximum compressive load can be estimated as

4 x 80=320 kg and the maximum shear force during the ground contact phase while walking 16 – 74

Newton.12,26,27 When unloaded, the forces are almost negligible.

Discrimination in the treatment should be made between adolescents and adults and, whether the

fragment is attached or partially detached, or found in the knee as a loose body.28–36

Bots37 distinguished fi ve stages, implementing not only the stability of the fragment, but also the fi

state of the cartilage. This state showed to be of high importance for the final outcome of the fi

treatment in his series and was not always in accordance with the stability of the fragment.37

(Table 1)

99

8

General discussion

Table 1 State of the osteochondral fragment (according to Bots [37])

stage fragment stability cartilage

1a stable intact cartilage

1b stable fi ssure at the margins of the fragmentfi

2a mobile, but attached fraying at the edges and mild degenerative changes

2b loose body still vital with minimal degenerative changes

3 loose body or fragmented seriously damaged

Adolescents with an attached, but symptomatic lesion (stage 1a, 1b).

In adolescents the healing is less compromised, compared to the adult form of OCD. During a long

time spontaneous healing was believed to be the natural course of the disease and the treatment

was conservative in case of an attached, but symptomatic lesion. This treatment evolved from

immobilisation in a plaster of Paris for several months and reduction of weight bearing to only

limitation of activities for a restricted time period of three to six months.28–31 However, failures of

this regimen became evident in time with failure rates from 10% to 50% and, although spontaneous

healing did occur, the outcome is unpredictable.30,32–35

Arthroscopic drilling was recommended if the symptoms did not disappear within this period of

unloading or restriction of activities. Several papers report favourable results of this procedure in

adolescents, but not in adults, with success rates between 80% and 100%.10,32–36

However, regarding the OCD as a pseudarthrosis, drilling is only one of the revascularisation

measures of the treatment. Drilling and additionally temporary fixation of the fragment withfi

biodegradable rods is a next step in the concept of optimal treatment.13,15,16 Using compressive

biodegradable devices, at most neutralizing the disrupting forces, would be a supplemental adjunct

in the healing process, without the harm of a second hardware-removal intervention. If the devices

are inserted during an arthroscopic procedure, the harm to the patient is further more minimized.

Adolescents with a partly or fully detached lesion and adults

In this group of patients, the disease has reached a next stadium, i.e. stage 2a or 2b, 3.

I f the dissecat is fragmented or the cartilage surface is seriously damaged (stage 3), reinsertion

procedures are useless. After fragment removal, cartilage resurfacing surgery should be performed.

Shaving and debridement or drilling alone can lead to early arthrosis1–8 and research is being

conducted to develop procedures to restore the defect with hyaline cartilage containing collagen

type 2.

In sequence of development, perichondrium transplantations,38 autologeous osteochondral

cylindral transplantations (mosaic plasty),39,40 micro fracture chondroplasty,41 Autologeous

Chondrocyte Implantations under a periost flap (ACI)fl 42 and Matrix Induced Autologeous

Chondroc yte Implantations (MACI),43–45 have been introduced as cartilage re-surfacing surgery.

100

Chapter 8

Several of the previously mentioned procedures have already been abandoned. The short term

results of the micro fracture procedure and MACI procedures seem to be the most promising with

a comparable outcome during a follow-up period of 2 years, but a tendency is emerging, that the

MACI performs better over time.43–46

If the sequester is intact and viable (stage 2a - 2b), reinsertion should be performed after debridement

of the dissecat bed. An autologeous spongeous bone transplantation is optional in adolescents but

obligatory in adults.10,17,20–25

Bone pegs or cartilage-bone cylinders47,48 have been used as non metallic fixation devices over the fi

last fi ve decades. Metallic devices like pins or K-wires,fi 10,19,20,49 staples50 or screws9,14,17,18,21–25 in all kind

of designs, have been applied as well. For several reasons, most metallic devices have to be removed

by means of a second procedure. Left in place, they cause damage to the opposite cartilage surface

of the tibia17,18,21,22 or break.50 Even when initially imbedded under the cartilage surface they can

gradually protrude, causing cartilage damage after all.50,51 Another potential disadvantage is the

development of allergic reactions evoked by chromium, nickel and cobalt containing components,

being also potent carcinogens in animals.52

This stimulated the research for biodegradable devices that, once inserted, do not have to be

removed after consolidation of the fragment.

Three biodegradable polymers; polydioxanon, polyglycolic acid and polylactic acid and their co-

polymers, combinations or blends, are used for this purpose. However, both synovitis and sterile

inflammatory sinus formation is reported when using devices, made of polyglycolic acid and fl

polylactic acid.53-55,56

Although favourable results with only biodegradable pins as fixation devices in the stage 2a – 2bfi

have been reported13,15,16 and also in combination with tissue glue,57 stable fi xation with compressionfi

screws contributes to better consolidation of the reinserted fragment, especially in adults, because

it neutralizes both shear forces and disrupting forces. This is in contrast with smooth pins, which do

not have the capacity to produce compression.9,10,17-25

However, the diameter of smallest metallic cannulated screw is 2.4mm at the moment, each screw

causing a defect in the fragment of 4.5mm2. At least two screws are necessary to obtain also rotational

stability. Two screws would cause a bone loss of the fragment of almost 10mm2. A compromise is

one centrally placed metallic screw, which has to be removed arthroscopically before loading the

leg. This applies compression. The combination with some biodegradable pins, 1.5mm in diameter,

(surface = 1.77mm2) provides rotational stability.

The removal of metallic pins, used instead of biodegradable ones as part of the procedure, is only

possible at the cost of considerable cartilage damage.

The diff erent treatment modalities are in the patient series, described inffff chapter 2.58

In seven knees of six patients, the fragment was fixed with pins. Five times (71%) an undisturbed fi

101

8

General discussion

consolidation occurred (all type 1b). One time (patient #1, fi rst knee, type 2a) redislocation was fi

followed by perichondrium transplantation, resulting in twelve complaints-free years. The other

patient (#3, type 2b) showed no consolidation on the radiographs at eight weeks postoperatively.

During second surgery debridement of the dissecat bed, autologeous cancellous bone

transplantation and a compressive fi xation with two screws was performed. Consolidation of the fi

fragment followed.

The fragment, type 2a, of patient #7, was primarily fixed with two screws. Because of a persistentfi

non union, successful perichondrium transplantation, after fragment removal, was performed. The

fragments in patients #5 and #9 (both type 2a) were fixed with one screw and three biodegradable fi

pins after debridement and spongeous bone transplantation. The screw was successively removed

during an arthroscopic procedure in day surgery after radiological verified consolidation of thefi

fragment and stability at arthroscopy, eight weeks after the first surgery. The patients recoveredfi

uneventfully.

Regarding these results and supported by the data from the available literature, the conclusion

was made, that at least the type 2a and 2b and, preferably, type 1a and type 1b, should be fixed fi

under compression. An in vivo experiment was started to eliminate the necessity of the second,

implant removal operation, using not only biodegradable pins but screws as well. A standardized

fragment was created and fi xed in goat knees with one screw (diameter, Ø, 2.7mm) and two pins (Ø fi

1.5mm) of respectively two commercially available biodegradable polymers, 18PGA/82PLLA (PGA/

PLA) and 4D/96LPLA(PLA96) and compared to the fi xation with screws and pins of surgical steel. Afi

sham operation served as a control. The results, described in chapter 3,59 show, that all fragments

consolidated, but that the screws of PGA/PLA, starting at 12 weeks post operatively, caused a

significant number of osteolytic defects in the condyles, in contrast to those of PLA96. However, thefi

screws of PLA96 induced considerable damage to the opposite cartilage surface, due to their slow

degradation. This is also confi rmed by observations, published in several articles.fi 60,61,62,63 No foreign

body reaction however, was found around the PLA96 pins and screws during a follow-up period of

fifty-two weeks.fi

Meniscus Arrows® (MAs, ConMed Linvatec Ltd Tampere, Finland), were designed several years ago

and are already in clinical use for mending ruptures in the vascularised part of the meniscus. They

consist of 20DL/80LPLA and have a considerable smaller Ø (1.1mm) than the any commercially

available biodegradable screw or nail.

This diff erence in Ø plays a more dominant role, when increasing numbers of devices are inserted ffff

and the fragments are small. The hole in the fragment caused by one MA measures 0.95mm2; one

Smart Nail® (SN), (ConMed Linvatec Ltd Tampere, Finland) 1.77mm2. Biodegradable screws, which

are nowadays available should not be used (chapter 3). One 2.4mm metallic cannulated screw, the

smallest available at this moment, creates a hole of 4.52mm2. The more devices are used, necessary

102

Chapter 8

for stable and compressive fixation of the fragment, the more bone loss, caused by the implants, willfi

occur in the fragment,.

The MAs showed to have a considerable anchorage capacity in bone during pull-out tests, described

in chapter 4.64 During the pull-out tests and shear force tests average values of 122- and 121Newton

were noted. This exceeds by far the shear forces in the human knee during one step with full weight

bearing. The repetitive character of the forces during walking is not included in this study. However,

the measured values outnumbers the values of the shear forces even more during unloaded

movements.

Water uptake during the hydrolisation process is the most important factor, and in a lesser

extent enzymatic influence, leading to degradation.fl 65,66,67 This water uptake induces swelling or

expansion of the polymers67,68,69 and increase of weight. This weight increase is mostly equated with

swelling.70,71,72,73,74 In fact, only a few authors really did measure the increase of the dimensions in

some way and term this swelling.67,75,76

If this swelling or expansion is substantial, the initial fixation of solid devices, composed of fi

biodegradable polymers, in bone could be enhanced. This would increase the holding properties.

During an in vitro experiment, described in chapter 5, the increase of the weight of six MAs after

twenty-eight days of immersion in a sterile isotonic saline solution was compared with the change in

dimensions, measured under a fi eld-emission scanning electron microscope. Although the weight fi

increased significantly with more than 9% (within the fifi rst two hours, remaining stable afterwards),fi

the core diameter of the devices increased gradually with only 1%.

This will have no consequences for the holding properties and, secondly, this experiment shows,

that the increase of weight is not equivalent with swelling or distension.

During this experiment we encountered an unexpected decrease of the barb-barb diameter of

more than 8% due to inward curling.77 This decrease in barb-barb distance in time could have

consequences for the anchorage capacities.

A following experiment showed (chapter 6), however, that the average pull-out force, required

to extract six new MAs out of a thawed, previously fresh frozen human femur condyle, did not

diff er signififfff cantly if the MAs were previously degraded during thirty-one days in a sterile, isotonic, fi

buff ered saline solution at 37º Celsius.ffff 78 Therefore, it was concluded, that the phenomenon of

inward curling of the barbs would not interfere with the holding properties of the MAs.

In chapter 7 the clinical application of MAs is reported in fi ve patients.fi 79

In two skeletally mature patients with an OCD, once a type 1b, the other with a type 2a, the fragments

were fixed with respectively three and fifi ve MAs.fi

In three other patients with osteochondral fractures of their femoral condyle the type 2b fragments

were fi xed within two weeks after the trauma with respectively two times 2 MA’s and one time withfi

103

8

General discussion

five MAs. The choice of the number of MAs depended on the size of the fragment.fi

Postoperatively, a plaster of Paris splint was applied for two weeks, followed by a hinged brace for ff

three weeks. During this period no weight bearing was allowed.

All fragments consolidated and the clinical course was uneventful, with a follow-up period ranging

between two and nine years with an average of fi ve years.fi

Trillat stated that the causality of an OCD fragment, that is covered with fibrous tissue, compared fi

with osteochondral fractures with bleeding surfaces at the bony side of the fragment, is different.ffff 80

The initial therapy of an OCD, as stated earlier, should more extensive than the therapy of an

osteochondral fracture, i.e. only reposition and fi xation. However, the way of fifi xation of an OCDfi

fragment as well as osteochondral fractures can be the same.79, 81

In the series, described by Weckström et al.82 consolidation was noted in 53% of the patients, when

pins were used as fixation devices and in 73% of the patients with a SN as fifi xation device. Thisfi

diff erence was signififfff cant. All patients were skeletally mature men.fi

In another recent paper by Dines81 consolidation occurred in 7 out of 9 (78%) patients (eight OCD’s

and one osteochondral fracture) treated with SNs as fi xation devices. The average number of SNs fi

was four, ranging between two and ten nails.

In the series presented in chapter 7, all fi ve fragments consolidated and the maximum number of fi

implants was five, corresponding with 3.95mmfi 2 in a fragment of 750mm2 which is negligible.

Five SNs would have caused a loss of bone of more than twice this surface (8.85mm2). The smaller

the size of the fragment, the more important these differences will be.ffff

The composition of MAs and SNs is the same; both are manufactured from the same self reinforced

DL- polylactide copolymer. MAs are more frequent available in hospitals than SNs for already

established indications, which is an additional advantage.

In all four patients with detached fragments in the series described in chapter 7, fibrin glue wasfi

applied prior to reduction and fixation of the fragment. In analogy with the reports of several authors, fi

the beneficial use of glue in case of interruption of the cartilage surface was demonstrated.fi 57,83–85

During the fi rst two weeks postoperatively, the process of re-integration was protected by applyingfi

a plaster of Paris splint, followed by a hinged brace and no weight bearing for three weeks, to

facilitate the consolidation of the fragment and to allow the healing of the cartilage.

The margins of the fragments in the knees of the three patients at second look arthroscopy were

smoothly and in congruency with the surrounding cartilage, as showed in chapter 7.

104

Chapter 8

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108

109

9CHAPTER

Conclusions and future perspectives

110

Chapter 9

Conclusions and future perspectives

1. The smaller diameter of the Meniscus Arrows® (MAs), compared to the Smart Nails® (SNs),

combined with their frequent availability in hospitals for already established indications,

their excellent hold in bone, at least equal to that of the SNs as demonstrated in chapters 4, 5,

6, the fact, that they are manufactured from the same self reinforced polylactide copolymer,

and the results, depicted in chapter 7, makes the MAs arguably the more advantageous

device for the fixation of OCD fragments and ostfi eochondral fractures in the knee.

2.* Adolescents and adults with a non-displaced fragment and intact cartilage (stage 1a – 1b)

should be treated by transchondral drilling, if pressure on the fragment does not reveal

debris emanating from the drill hole. Fixation with MAs, as many as needed to produce a

steady pressure on the fragment, should follow.

3.* Adolescents with a partly detached fragment (type 2a) should be treated with debridement

and drilling of the bottom of the dissecat bed, followed by compressive fixation of the fi

fragment with MAs, a spongeous bone transplant is optional. In the case of an adult patient,

this is obligatory.

4.* In case of a fully displaced fragment, but with intact cartilage, both in adolescents and adults

maximal treatment should follow i.e. nettoyage of the bottom of the crater, spongeous

bone transplantation and compressive fi xation of the fragment with an adequate numberfi

of MAs.

5. Before reduction and fi xation of the fragments, fifi brin glue should be applied on the margins, fi

to enhance the incorporation of the fragment covering cartilage into the surrounding,

recipient cartilage.

6.* A fully displaced dissecat with seriously damaged cartilage and/or fragmentation should be

removed and cartilage restoring surgery must be undertaken to restore the congruency of

the cartilage surface.

7. The shear force during one walking cycle in the knee is far less than the average force,

required to dislocate a bone block, fixed with 3 MAs in its bed. However, regarding the fi

repetitive character of the forces, distributed on the knee surface during walking and full

weight bearing, only unloaded movements of the knee joint should be permitted in a

hinged brace, after an initial period of two weeks of immobilisation in a plaster splint, until

consolidation of the fragment is confirmed.fi

111

9

Conclusion and future perspectives

8. Before weight bearing, consolidation of the fragment should be assessed by means of,

preferably, non-invasive means, such as MRI, or CT scanning.

9. If persistent postoperative hydrops, pain, locking is observed, arthroscopy should be

per formed to correct the, most of the time existing and corrigible, chondropathy of the

margins of the fragment.

10. The aforementioned properties indicate, that biodegradable devices like MAs could also

serve as fi xing devices for several other indications, where the use of small, but good in fi

bone anchoring biodegradable devices is advantageous, especially, if they can be inserted

arthroscopically.

Some examples:

· displaced tibial spine fractures in children and adolescents

· displaced radial head fractures

· Mallet fractures of the distal hand phalanges

· avulsion fractures at the base of the fi rst phalanx of the thumb, the so-called skier’s orfi

gamekeeper thumb

· humeral epicondyle fractures in childhood

Further research should be conducted to explore the potential benefi t of these applications.fi

*: proposed treatment algorithm for the OCD:

proposed OCD treatment algorithm

Stage 1a 1b 2a 2b 32a 2badolescent drilling, MA

fixationfidrilling, MA fixation, fi

shavingspongeosa

transplant optionalspongeosa

transplant requiredcartilage resurfacing

surgery

adult drilling, MA fixation,fi

drilling, MA fixation, fishaving

cartilage resurfacing spongeosa transplant requiredsurgery

if debris, clean dissecat bed, addspongeousa transplant

112

113

Summary

10CHAPTE

R

114114

Summary

Knee joint disorders in man may always have existed. The first known description of the removal of fi

loose bodies from the knee joint was made by Ambroise Paré in 1558.

In the following centuries, the origin of osteochondritis dissecans (OCD) is still not elucidated. The

treatment evolved from only removing the fragment to removing and abrasion of the dissecat bed

and, finally, to fifi xation of the fragment after consolidation promoting procedures, like debriding and fi

drilling of the bottom of the crater and cancellous bone transplantation. In the treatment algorithm,

a diff erentiation should be made between adolescents and adults. ffff

In adolescents, the course of the disease is milder and, if the fragment is still in place, only drilling

and fi xation is suffifi cient to lead to consolidation of the fragment in the majority of the cases, if ffi

conservative treatment fails. If the fragment is partly or totally detached, but still intact, fixationfi

should follow after debridement of the dissecat bed. Cancellous bone transplantation is then

optional.

In adults, however, the OCD should be considered as a fully developed pseudarthrosis and the

treatment should be like the appropriate established pathways for pseudarthrosis therapy, i.e.

debridement, cancellous bone transplantation and a compressive, stable fixation. If the dissecat isfi

fragmented or the cartilage is heavily damaged, cartilage restoring procedures, instead of fragment

replacement should follow, like Matrix induced Autologeous Cartilage Introduction (MACI) or, in first fi

instance, micro fracture chondroplasty. Research is continuing to evaluate which one of those two

procedures will be to be preferred in future.

Pins and K-wires are used as fi xation devices. However, regarding at OCD as a pseudarthrosis,fi

compressive fi xation devices such as screws or staples should be applied to fifi x the fragments. fi

Metallic devices have to be removed in most cases during a second procedure before loading the

limb to prevent damage to the opposite cartilage. Even embedded under the surface in an effort ffff

to prevent this cartilage damage, protrusion can occur. An additional long term disadvantage

of the permanent implantation of metallic devices is scattering during CT or MRI scanning and

some metals, such as chromium, nickel and cobalt can evoke local allergic reactions like eczema.

Chromium, nickel and cobalt are also potent carcinogens in animals.

Several research groups have explored the use of autologeous cartilage bone plugs as fixationfi

devices. However, donor site morbidity, the absence of producing substantial compression and

failure of the re-integration process at the interface of donor and recipient cartilage make this

procedure less than optimal.

The use of biodegradable fi xation devices would prevent radiological scattering, lacking the other,fi

previously mentioned, disadvantages and renders a removal operation unnecessary.

In chapter 2, the consolidation is described of five intact and still attached fragments after trans-fi

fragmental drilling and fi xation with biodegradable pins. Two patients with detached lesions werefi

successfully treated by fixation with one, centrally placed, metallic screw, providing compression,fi

combined with three biodegradable pins of polydioxanon to obtain rotational stability, whereas

115115

Summary

10

two detached fragments, fi xed with only biodegradable pins, failed to consolidate.fi

However, the screw still had to be removed before loading the leg during a second surgical

procedure, to prevent damage of the opposite cartilage.

This was the motive for the in vivo research project in goat knees, described in chapter 3. A

standardized created cartilage bone fragment was fixed with one centrally placed biodegradable fi

screw, 20mm in length and 2.7mm in diameter (Ø), and two pins, 20mm long and 1.5mm in Ø,

composed of the same material. As biodegradable polymers, commercially available materials

were used: a random copolymer composed of 82% poly-L-lactic acid (PLLA) and 18% poly-glycolic

acid (PGA) copolymer (PGA/PLA) and the as-polymerized poly(96L-D-lactide) (PLA96) polymer. The

results were compared to those when devices of surgical steel were inserted. A sham operation

served as a control.

Around all eight screws in the PGA/PLA group, starting at twelve weeks post operatively, osteolytic

defects were found, which is in contrast to only once at eighteen weeks after implantation around a

screw of PLA96. This is a significant difffi erence (p < 0.001). The screws of PLA96 were found to showffff

degenerative changes at forty-six weeks, comparable with the PGA/PLA screws at twelve weeks,

and some damage of the opposite cartilage was observed. One time a cavity was seen around a

pin of PGA/PLA. This was never found around the other fi fteen pins of this polymer and also never fi

around the sixteen pins of PLA96. This is not significant and the conclusion was made that pins of fi

the selected two polymers can safely be used, regarding the tissue reaction, but not the screws.

Either, it is likely that cavities develop, or that the degradation is so slow, that undesirable damage

of the opposite cartilage is caused. This phenomenon is found in the literature as well.

Meniscus Arrows® (MAs) were designed and introduced several years ago (1994) and are already in

current use for arthroscopic mending of ruptures in the vascularised part of menisci. They consist

also of poly-LDL lactide and have a smaller Ø (1.1mm) than the smallest biodegradable screws

(2.0mm), barbed nails (Smart Nails® (SNs) 1.5mm) or cannulated metallic screws (2.4mm).

In chapter 4 is the outcome of pull-out tests in axial direction described , comparing the hold in

bone of three times a single Arrow versus a single 2.0mm in Ø metallic screw. Bone blocks, fixed withfi

three MAs were pulled-off in axial- and tangential direction, the last mentioned in order to mimicff

shear forces. Average forces of more than 60Newton (N) were noted for the single Arrows and of

more than 120N for the bone blocks in both directions.

The screws performed higher, but the results of the Arrows were appreciated to be enough for

clinical application.

The impetus for the tests, described in chapter 5 was that swelling or distension, due to the uptake

of water, has been equated in literature with an increase of weight of the material. In fact, only a

few authors measure the increase of the dimensions in some way and term this swelling. However,

116116

Summary

a substantial swelling, or distension, could increase the hold of the MAs in solid materials like bone

like expanding bolts.

During the tests, six MAs, directly retrieved from the package, were weighed. Reweighing was

repeated after 2, 4, 6, 8, 24, 28, 32, 48, 60 hours and 7, 10, 14, 18, 28 days during submersion in a sterile,

phosphate buffered saline solution at 36ºC, refreshed twice a week under sterile circumstances. This ffff

period of 28 days is the time after which the first consolidation of the fragments can be expected. fi

Parallel to this series the core diameter and the distance between the tips of the barbs of a second

series of six new MAs were measured in a fi eld-emission scanning electron microscope, also startingfi

at t=0 (t1) and at 2, 4, 6, 24 hours and 3, 4, 5, 7, 11 and 18 days afterwards, being submerged as well.

This experiment was fi nished after 18 days, achieving, statistically, suffifi cient results.ffi

The weight of the MAs increased during the fi rst two hours from an average of 0.0227gram to an fi

average of 0.0248gram or 9.16%. This is signifi cant (p = 0.027). However, after two hours the weightfi

remained more or less stable at an average total weight gain after 28 days of 0.0017gram or 7.18 %.

The average weight variation was not significant.fi

During the swelling or distension experiment a subtle increase of the average core diameter of the

arrows with 0.01mm, or 1.01%, from 1.22mm to 1.23mm was noted. This is significant (p = 0.031).fi

The barb-barb diameter decreased, unexpected and significantly (p = 0.031) in time with 0.15mm,fi

or 8.6%, from an average of 1.74mm to 1.59mm.

In conclusion, the maximum change of weight occurred in the fi rst two hours, staying stablefi

afterwards and no correlation was found with a theoretical swelling or distension of the devices.

Indeed, only the core diameter increased negligible, regarding the mechanical properties. In

contrast, the significant decrease of the barb-barb diameter could have consequences for the fi

anchoring capacity in bone.

The effect of decrease of the barb-barb diameter of the MA’s during the degradation on the hold in ffff

bone was evaluated during an experiment, described in chapter 6. Eight new MAs were pulled out

of a thawed fresh frozen human femoral condyle, in comparison with six MAs, after being submerged

during thirty-one days in a sterile phosphate buffered saline solution at 37º Celsius. The average ffff

extraction force of the new, non-degraded MAs and the degraded MAs did not differ signififfff cantlyfi

(t-test: p = 0.23). Also the spreading of the results did not differ signififfff cantly according to the Mann-fi

Whitney test (p= 0.28). In the two-way ANOVA test no significant interaction between degradationfi

and location on the condyle (p= 0.7), no difference between degraded or non-degraded MAs (p= ffff

0.15) or location on the lateral- or medial condyle (p=0.14) was noted.

The conclusion can be made, that, although the inward curling of the barbs after a degradation

period of thirty-one days suggests that this could lead to a decrease of the hold in a solid material

like bone, this is not confirmed in our study and that this phenomenon does not interfere with thefi

successful application of MAs to fi x small bony fragments in fracture surgery and in OCD disease.fi

117117

Summary

10

Finally, after evaluating the previously mentioned data, pull-out tests were performed with MAs and

SNs to choose between both devices for the application of fi xing the fragments in the treatment fi

of Osteochondritis Dissecans and Osteochondral fractures in patients (chapter 7). In two recent

papers the successful clinical application of SNs as fixation devices in the treatment of OCD is fi

described in, respectively, 30 and 11 patients without negative side effects. However, the smallerffff

diameter of the MAs, compared to the SNs, respectively 1.1mm and 1.5mm, would cause less

damage to the fragments and would permit the use of more devices, spreading the compression,

with equivalent or less damage, which could be advantageous. The composition of current MAs and

SNs is equivalent; both are manufactured from the same self reinforced poly-L-DL (80-20) Lactide

copolymer. So, in view of the successful use of the SNs for this indication, no negative side effects areffff

to be expected from the smaller MAs as well.

First, three MAs and three SNs were, successively, pulled out of a thawed, fresh frozen, human

condyle. Second, three bone blocks, each with either three MAs or three SNs were fixed at thefi

condyle and pulled off as well, in axial and tangential direction, the latter mimicking one cycle of ff

shear forces. The pull out tests showed for the single MA’s an average value of 68 N. The single SNs

required an average pull-out force of 61N. The required forces in the bone blocks group to distract

the blocks with the three MA’s from the condyle showed an average force of 122N, and shear force

testing showed an average force of 121N. The blocks with three SNs as fixation devices needed fi

an average force of 88N to be pulled off . The Levene’s test showed no signififfff cant difffi erence in theffff

variances of the transformed variable (P = 0.454). Based on the outcome of these tests, we chose to

employ the smaller MAs for the clinical application.

In two patients, group 1, an OCD dissecat, once attached and once detached, was fixed with,fi

respectively, three and fi ve MAs. During surgery on the fifi rst patient, arthroscopic drilling wasfi

followed by fi xation with three MAs. In the second patient the procedure started arthroscopically fi

but was converted due to the size of the fragment and the necessity to drill and insert the MAs

from diverse angles. In this patient, after debridement, drilling of the bottom of the defect and

cancellous bone transplantation, the dissecat was fixed with fifi ve MAs and Tissuecoll® was applied fi

on the cartilage margins of the dissecat.

In group 2, an osteochondral fracture in three patients was fixed within two weeks after the initial fi

trauma with, respectively, twice two MAs and one time with five MAs. All procedures started fi

arthroscopically and were continued through a small arthrotomy, due to the size of the fragment.

Tissecoll® was put on the cartilage edges of the fragment before fixation. A second look arthroscopy, fi

six weeks after the first surgery, showed a congruent interface between the fragmental andfi

recipient cartilage and a stable fragment. After an average follow-up period of fiff ve years, varyingfi

between two and nine years, all patients were free of complaints, although the patients in group 1

spontaneously avoided peak force inducing sports as a precaution.

118118

Summary

Conclusion 1: based on the results from in vitro pull-out tests and available clinical studies,

biodegradable devices like Meniscus Arrows® and Smart Nails® are likely to perform adequately

as fixation devices for small fragments in the treatment of Ostechondritis Dissecans disease andfi

osteochondral fractures in the knee. They both provide the advantage of one stage surgery without

the need for subsequent surgery to remove the implants.

The smaller diameter of the Meniscus Arrows® suggests that this device should be preferred for this

indication. In this study, MAs allowed undisturbed healing of osteochondral lesions of the knee in

five patients after reduction and fifi xation without complications.fi

According to the state of the fragment the proposed OCD treatment algorithm is as follows:

state of the osteochondral fragment (according to Bots, 1983)

stage fragment stability cartilage

1a stable intact cartilage

1b stable fi ssure at the margins of the fragmentfi

2a mobile, but attached fraying at the edges and mild degenerative changes

2b loose body still vital with minimal degenerative changes

3 loose body or fragmented seriously damaged

proposed OCD treatment algorithm

Stage 1a 1b 2a 2b 3adolescent drilling, MA

fixationfidrilling, MA fixation, fi

shavingspongeosa

transplant optionalspongeosa

transplant requiredcartilage resurfacing

surgery

drilling, MA adultfixation,fi

drilling, MA fixation, fishaving

cartilage resurfacing spongeosa transplant requiredsurgery

if debris, clean dissecat bed, add spongeousa transplant

Conclusion 2: The aforementioned properties of the MAs indicate, that biodegradable devices like

MAs could also serve as fixation devices for several other indications, where the use of small and fi

good in bone anchoring biodegradable devices is advantageous, especially, if they can be inserted

arthroscopically.

Some examples:

· displaced tibial spine fractures in children and adolescents

· displaced radial head fractures

· Mallet fractures of the distal phalanges of the hand

· avulsion fractures at the base of the fi rst phalanx of the thumb (the so-called ski thumb)fi

· humeral epicondyle fractures in children

Further research should be performed to explore the potential benefi t of these applications.fi

119

Samenvatting

120120

Samenvatting

Knieklachten zijn waarschijnlijk zo oud als de mensheid. De eerste beschrijving betreffende hetffff

verwijderen van losse fragmenten uit het kniegewricht is, voor zover bekend, uit 1558 van Ambroise

Paré.

Het ontstaan van Osteochondritis Dissecans (OCD), een van de oorzaken van deze losse fragmenten,

is in de daaropvolgende eeuwen nog steeds niet verklaard.

De behandeling ontwikkelde zich van alleen het verwijderen van het fragment, via verwijderen en

afschaven van de bodem van het defect tot uiteindelijk het weer vastzetten van het fragment na

procedures om het vastgroeien van het fragment te bevorderen, zoals ontdoen van de bodem van

het defect van bindweefsel, opboren en aanbrengen van een spongieus bottransplantaat.

In de behandelingsstrategie moet een verschil gemaakt worden tussen de aandoening bij

adolescenten en volwassenen. Bij adolescenten verloopt de aandoening over het algemeen

milder dan bij de volwassenen en is opboren en eventueel fixatie voldoende als conservatieve fi

behandeling, bestaande uit immobilisatie en beperken van de belasting van de knie, faalt.

Als het fragment gedeeltelijk of volledig los is, maar wel intact, dient het na reiniging van de bodem

van het defect teruggeplaatst te worden en stabiel en onder compressie gefixeerd te worden. In ditfi

geval kan een spongieus bottransplantaat overwogen worden.

Bij volwassenen dient een OCD gezien te worden als een pseudarthrose en de behandeling dient

als zodanig te zijn en wel reiniging en revitalisering van de fractuuroppervlakken, spongieuze bot-

transplantatie en comprimerende, stabiele fi xatie. Als het fragment en/of het kraakbeen te zeer fi

beschadigd is, moet het verwijderd worden en dienen kraakbeen defect herstellende maatregelen

genomen te worden, zoals Matrix induced Autologeous Cartilage Introduction (MACI) of analoge

operaties, of, in eerste instantie, Microfracture Chondroplastiek. Op dit ogenblik zijn meerdere

studies gaande om uit te maken welke procedure de beste blijkt te zijn.

Als fixatie middelen worden pennetjes van autoloog fi bot, van metaal en Kirshner draden gebruikt.

Echter, OCD als een pseudarthrose beschouwende, dienen comprimerende fixatiemiddelen zoals fi

schroeven of krammen gebruikt te worden.

Indien dezen van metaal zijn, moeten ze meestal gedurende een tweede operatie verwijderd

worden voordat het ledemaat belast mag worden, om zo beschadiging van het ertegenover

liggende kraakbeen te voorkomen. Zelfs als ze in eerste instantie onder het kraakbeenoppervlak

begraven zijn kunnen ze gaan uitzakken en moeten ze alsnog verwijderd worden. Verder is een

ander nadeel het verstoren van Computer Tomografi e (CT)- en Magnetic Resonance Imaging (MRI)fi

beelden. Tenslotte kunnen sommige metalen, zoals chroom, nikkel en kobalt, allergische reacties

oproepen en zijn het krachtige carcinogenen in dieren.

Autologe kraakbeen-bot pluggen zijn door verschillende onderzoeksgroepen toegepast als fixatie- fi

middelen. Donorplaats problemen, gebrek aan compressie en integratieverstoring van de overgang

tussen het getransplanteerde en het plaatselijke kraakbeen maken deze procedure niet in eerste

instantie te verkiezen.

Aan het toepassen van bio-afbreekbare fi xatie middelen kleven de eerder genoemde nadelen niet fi

121121

Samenvatting

en zij hoeven ook niet in een tweede operatie verwijderd te worden.

In hoofdstuk 2 wordt het vastgroeien beschreven van 5 intacte en nog gedeeltelijk vastzittende

fragmenten na opboren en fixatie met behulp van bio-afbreekbare pennetjes van polydioxanon.fi

Twee andere patiënten met een volledig losliggend fragment in hun knie werden met succes

behandeld met een centrale metalen mini schroef, die compressie gaf, geflankeerd door 3 van de fl

eerder genoemde pennetjes, die voor de rotatiestabiliteit zorgden. Echter, de schroef moest wel

tijdens een tweede ingreep verwijderd worden om kraakbeenschade aan het ertegenover liggende

kraakbeen te voorkomen.

Bij twee andere patiënten, bij wie het fragment met alleen pennetjes werd vastgezet, kwam het niet

tot vastgroeien.

Dit was de aanzet voor het in vivo-onderzoek in geitenknieën, zoals dat beschreven wordt in

hoofdstuk 3. Een op gestandaardiseerde manier gemaakt bot-kraakbeen fragment werd steeds in

een groep van 8 knieën vastgezet met 1 centraal geplaatste schroef, 20mm lang en met een diameter

(Ø) van 2.7mm en 2 pennetjes, ook 20mm lang en een Ø van 1.5mm, gemaakt van respectievelijk

het bio-afbreekbaar polymeer at random gepolymeriseerd 82% poly-L-Lactic Acid (PLLA) met

18% poly-Glycolic Acid (PGA) co-polymeer (PGA/PLA), het as-gepolymeriseerd poly(96L-4D) Lactic

Acid) (PLA96) en van chirurgisch staal. Een operatie in 8 knieën waarbij alleen het fragment en de

boorgaten werden gemaakt diende als controle groep.

Rond alle schroeven, gemaakt van PGA/PLA, werd vanaf 12 weken een osteolytisch defect gevonden,

in tegenstelling tot slechts éénmaal rond een schroef van PLA96 op het tijdstip van 18 weken. Dit

verschil is signifi cant (p < 0.001). De degradatie fase tfi en tijde van 46 weken na implantatie van

de PLA96 schroeven bleek vergelijkbaar aan die op 12 weken na implantatie van de PGA/PLA

schroeven. Enige kraakbeenschade aan het tegenover liggende kraakbeen was zichtbaar. Eenmaal

werd een holte gevonden rond een pennetje, gemaakt van PGA/PLA. Rond de overige 15 PGA/PLA

pennetjes, en rond de 16 pennetjes gemaakt van PLA96 lag het omliggende bot op alle tijdstippen

aan.

Dit verschil is niet signifi cant en geconcludeerd mag worden, dat bioafbreekbare pennetjes, fi

gemaakt van de beide toegepaste polymeren, veilig toegepast kunnen worden wat betreft de

weefsel reacties. Echter niet de schroeven aangezien dezen enerzijds ongewenste holtevorming

veroorzaken en anderzijds schade aan het ertegenover liggende kraakbeen. Ook in de literatuur is

hier al melding van gemaakt.

Meniscus Arrows® (MA’s) zijn oorspronkelijk jaren geleden (1994) ontwikkeld voor het arthroscopisch

hechten van meniscusscheuren. Zij zijn gemaakt van poly-LDL lactide en hebben een kleinere Ø

(1.1mm) dan de kleinste bio-degradeerbare schroeven (Ø 2.0mm), spijkers met weerhaken (Smart

Nails®, SNs, Ø1.5mm) of gecannuleerde metalen schroeven (2.4mm). In hoofdstuk 4 worden de

122122

Samenvatting

resultaten beschreven van trekproeven met 3 maal een enkele MA en vergeleken met die van

3 maal een metalen schroef met een diameten van 2mm. Tevens werden gestandaardiseerd

gemaakte botblokjes met 3 MAs gefixeerd en zowel tangentieel, afschuifkrachten imiterend, als in fi

axiale richting vanuit hun oorspronkelijke plaats getrokken. Gemiddelde krachten van meer dan

60Newton (N) voor de enkele MA’s en meer dan 120N voor de botblokjes in beide richtingen werden

gevonden. De schroeven presteerden nog beter, maar de resultaten, gevonden in de Meniscus

Arrow groepen werden voldoende geacht voor klinische toepassing.

De aanleiding voor het onderzoek dat in hoofdstuk 5 beschreven wordt was dat, indien het

opzwellen van bio-afbreekbare polymeren substantieel is, dit het houvast in bot volgens het principe

van de keilbout in steen zou doen toenemen. Echter, het opzwellen wordt meestal gelijkgesteld aan

gewichtstoename door het opnemen van water. Slechts enkele auteurs hebben werkelijk, en dan

nog in beperkte mate, de omvang van het materiaal gemeten en noemen dat zwelling.

Gedurende het onderzoek werden 6 nieuwe MA’s eerst gewogen. Vervolgens volgde opnieuw

wegen na 2, 4, 6, 8, 24, 28, 32, 48, 60 uur en 7, 10, 14, 18, 28 dagen, Tussendoor werden ze in een

steriele, fosfaat gebuff erde fysiologische zout oplossing met een temperatuur van 37ºC gedompeld, ffff

die tweemaal per week onder steriele omstandigheden werd ververst. Parallel hieraan werd de

centrale diameter en weerhaak-weerhaakpunt diameter van een tweede serie van 6 nieuwe MA’s

gemeten in een veld-emissie elektronenmicroscoop, ook beginnend bij t=0 (t1) en vervolgens na 2,

4, 6, 24 uren en 3, 4, 5, 7, 11 en 18 dagen onderdompeling in een overeenkomstige vloeistof. Na 18

dagen waren al voldoende gegevens verkregen en kon dit experiment gestopt worden.

Het gewicht van de MA’s nam gedurende de eerste 2 uren toe van een gemiddelde van 0.0227

gram naar een gemiddelde van 0.0248 gram ofwel 9.16 %. Dit is significant (Wilcoxons signed rank fi

toets: p = 0.027). Echter, na 2 uren bleef het gewicht min of meer constant bij een gemiddelde totale

gewichtstoename na 28 dagen van 0.0017gram of 7.18 %. De gemiddelde variatie in gewicht was

niet significant.fi

Gedurende het zwelexperiment werd een subtiele toename van de centrale diameter van de MA’s

gemeten van 0.01 mm, 1.01%, ofwel van 1.22 mm tot 1.23 mm. Dit is significant (t-test: p = 0.031).fi

Volledig onverwacht nam de weerhaak-weerhaakpunt afstand met 0.15mm, of 8.6 %, af, van een

gemiddelde van 1.74 mm naar 1.59 mm.

Concluderend was de maximale gewichtstoename al bereikt na 2 uur zonder dat er een overeenkomst

werd gevonden met het opzwellen van de MA’s. Sterker nog, alleen de centrale diameter nam, met

het oog op eventuele mechanische consequenties verwaarloosbaar toe. Daarentegen werd een

aanzienlijke en significante vermindering van de weerhaak-weerhaakpunt afstand gevonden.fi

Dit zou wel gevolgen kunnen hebben voor de fixatiecapaciteit in bot.fi

Het onderzoek naar dit mogelijke mechanische effect van de verminderde weerhaak-weerhaakpuntffff

afstand wordt beschreven in hoofdstuk 6. Acht nieuwe MA’s en 6 MA’s, na onderdompeling

123123

Samenvatting

gedurende 31 dagen in de oplossing zoals in hoofdstuk 5 wordt beschreven, werden uit een

ontdooide, tevoren diep gevroren menselijk femur condyl getrokken. De gemiddelde kracht om

de nieuwe, niet gedegradeerde MA’s uit te trekken verschilde niet significant (t-toets: p = 0.23)fi

van die van de gedegradeerde MA’s. Ook de spreiding van de resultaten verschilde niet significant fi

(Mann-Whitney toets: p = 0.28). Met de tweezijdige ANOVA toets werd geen significante interactie fi

gevonden tussen degradatie en locatie op de condyl (p = 0.7), gedegradeerd of niet gedegradeerd

(p = 0.15) of locatie op de mediale, dan wel laterale condyl (p = 0.14).

Geconcludeerd kan worden dat het in het vorige experiment gevonden verschijnsel van het

naar binnen krullen van de weerhaken van de MA’s gedurende 31 dagen onderdompeling in een

fysiologische zoutoplossing, de implantatie in werkelijkheid benaderende, geen mechanische

consequenties lijkt te hebben met betrekking tot de klinische toepassing bij het fixeren van kleine fi

bot-kraakbeen fragmenten.

Tenslotte, nadat de gegevens van de vorige proeven waren geanalyseerd, werden trekproeven

verricht met MA’s en SN’s om te kiezen tussen die twee voor de uiteindelijke klinische toepassing

(hoofdstuk 7). In twee recente artikelen is de succesvolle toepassing van de SN’s beschreven bij

de behandeling van OCD in respectievelijk 30 en 11 patiënten zonder negatieve bijverschijnselen.

Echter, de MA’s zijn bijna 30% dunner ten opzichte van de SN’s, namelijk 1.1mm versus 1.5mm.

Hierdoor wordt per Arrow minder schade toegebracht aan het fragment. Derhalve kunnen er meer

pennetjes gebruikt worden, wat de fi xatie ten goede komt en waardoor de druk gelijkmatigerfi

verdeeld wordt of, bij toepassen van minder pennetjes wordt evenredig minder botfragmentletsel

veroorzaakt. De MA’s en SN’s zijn gemaakt van het hetzelfde, in zichzelf versterkt poly-L-DL(80-20)

Lactide copolymeer. Gezien de succesvolle klinische toepassing van de dikkere SN’s zonder

schadelijke bijverschijnselen, zou dit van de dunnere MA’s ook verwacht mogen worden.

Eerst werden achtereenvolgens drie MA’s en drie SN’s uit een ontdooide, vers ingevroren menselijke

femur condyl getrokken. Er werden gemiddelde uittrekkrachten voor de MA’s van 68 N en voor de

SN’s van 61 N gevonden. Vervolgens werden drie botblokjes met gestandaardiseerde afmetingen

gefixeerd met of drie MA’s dan wel met drie SN’s in axiale richting losgetrokken van de condyl. fi

Hierna volgde een zelfde serie, maar nu was de trekrichting tangentieel ten opzichte van de condyl,

zo afschuifkrachten imiterende. Hierbij werden als waarden bij de MA’s respectievelijk 122 N en 121

N gevonden. De waarden voor de botblokjes met SNs gefixeerd bedroegen in axiale richting 88 N.fi

Afschuifkrachtproeven met SN’s werden gezien de tot dan al gevonden waarden niet meer verricht.

De getransformeerde Levene’s test voor een eventuele variatie tussen deze groepen toonde geen

significantie (P=0.454). Gezien de voordelen van het dunner zijn bij minimaal dezelfde mechanische fi

eigenschappen kozen wij voor de MA’s boven de SN’s voor klinische toepassing.

Bij twee volwassen patiënten, groep één met een nog vastzittend en één met een losliggend OCD

fragment, werd het fragment bij de eerste patiënt vastgezet met 3 MAs na maken van multipele

transfragmentaire boorgaten gedurende een arthroscopische procedure. Bij de tweede patiënt

124124

Samenvatting

werd de, aanvankelijk arthroscopische ingreep, geconverteerd naar een arthrotomie in verband

met de omvang en de plaats van het fragment en de noodzaak van het in meerdere richtingen

inbrengen van de MA’s. Alvorens het fragment met vijf MA’s te fixeren werd de bodem van hetfi

defect genettoyeerd, opgeboord en bedekt met een laagje autoloog spongieus botweefsel en werd

op de kraakbeenranden Tissucol® aangebracht.

Groep 2 bestond uit drie patiënten. bij wie een osteochondraal fragment binnen 2 weken na

het letsel werd gefi xeerd. Bij twee patiënten met 2 MA’s gefifi xeerd en bij één patient met vijf, ditfi

afhankelijk van de grootte en vorm van het fragment. Alle operaties begonnen als arthroscopie en

werden in verband met gebrek aan overzicht, plaats en omvang van het fragment, geconverteerd

naar een kleine arthrotomie. In overleg met de patiënten en hun ouders werd in deze groep 6

weken postoperatief een contrôle arthroscopie verricht voordat het been werd belast. Hierbij werd

een stabiel fragment met fraai aanliggende en vastzittende kraakbeenranden gevonden. In de

gemiddelde vervolgperiode van vijf jaar, variërende van 2 tot 9 jaar, zijn de patiënten klachtenvrij.

Opvallend is dat de patiënten in groep 1 uit eigen beweging sporten, die piekbelasting op de knieën

veroorzaken zoals hardlopen, hebben vermeden.

Conclusie 1: Afgaande op de laboratoriumtesten en resultaten van klinische toepassingen is het

aannemelijk dat bio-afbreekbare fixatiemiddelen zoals Meniscus Arrows® en Smart Nails® met succesfi

toegepast kunnen worden bij de fixatie van de bot-kraakbeen frfi agmenten zoals die voorkomen bij

Ostechondritis Dissecans en osteochondrale fracturen in de knie. Beiden bieden het voordeel van

een eenmalige operatie, waarbij de kleinere diameter van de Meniscus Arrows® met behoud van de

goede mechanische eigenschappen aanleiding is om voor dezen te kiezen.

Bij de vijf patiënten in de beschreven serie volgde ongestoorde consolidatie van de fragmenten met

genezing van het kraakbeen zonder negatieve bijwerkingen bij de gevolgde procedure.

125125

Samenvatting

Toestand van het fragment

Stage Fragment stabiliteit Kraakbeen

1a Stabiel Intact

1b Stabiel Kloven aan de rand van het fragment

2aBeweegbaar maar noggefixeerdfi

Rafels aan de randen en beperkte degeneratieve veranderingen

2b Volledig losliggendWel levensvatbaar en met minimale degeneratieveveranderingen

3Losliggend en gefragmenteerd

Ernstig beschadigd

Voorgesteld algoritme bij de behandeling van OCD

Stage 1a 1b 2a 2b 3adolescent Opboren, MA

fixatiefiOpboren, MA fixatie, fi

shavingEventueeel

spongieus bot transplantatie

Spongieus bot transplantatie

vereist

Kraakbeen hersteloperaties

Opboren, MA volwassenefixatiefi

Opboren, MA fixatie, fishaving

Kraakbeen herstelSpongieus bot transplantatie vereistoperaties

Indien debris bij boren vrijkomt:dissecaat bed nettoyage en een

spongieus bot transplantatie

Conclusie 2: Gezien de tevoren genoemde eigenschappen van de MA’s zouden dergelijke

fi xatiemiddelen ook gebruikt kunnen worden bij het fifi xeren van andere kleine kraakbeen/bot fi

fragmenten, waarbij hun kleine omvang, gecombineerd met goede verankerende eigenschappen

in bot, een voordeel is. Een extra voordeel is ook nog de mogelijkheid van arthroscopische insertie.

Te denken valt aan:

* Eminentia intercondylaris fracturen bij kinderen

* Gedisloceerde radius kop fracturen

* Ossale Mallet fracturen (aan de eind phalanx) van de vingers

* Gedisloceerde avulsie fracturen aan de basis phalanx van de duim ( de skiërs duim)

* Epicondyl fracturen van de bovenarm bij kinderen

Verder onderzoek zal moeten uitwijzen of deze andere indicaties klinisch toepasbaar zijn met goed

resultaat.

Afhankelijk van de toestand van het fragment is de voorgestelde stagering bij de behandeling van

OCD het volgende: (ontleend aan Bots, 1983)

126

127

Dankwoord

128

Dankwoord

De basis van dit proefschrift is voor mij een verhaal van serendipiteit.

Het eerste toeval is dat de eerste OCD patiënte, een 16 jarige meisje, zich bij mij op het spreekuur

meldde.

Wat moest ik doen aan een OCD? Aangezien er bij navragen geen bevredigend antwoord kwam en

ik net gelezen had over bio-afbreekbare staafjes en al besmet was met het arthroscopie virus wasfj

de volgende stap, na overleg met de ouders duidelijk. Arthroscopische fixatie. Dat het fragmentfi

uiteindelijk na 3 maanden losliet tijdens een hurkbeweging was een tegenslag. Hierna met

aanpassing van de methode en nabehandeling wél consolidatie bij de volgende twee patiënten.

Tijdens een posterpresentatie, in 1991 in Toronto, op het congres van de toenmalige International

Arthroscopy Association (voorloper van de ISAKOS) volgde overleg met Allan Anderson, die in

1990 een artikel had gepubliceerd over antegrade opboring en K-draadfi xatie bij een grote groep fi

patiënten. De K-draden moesten overigens in een tweede ingreep weer worden verwijderd.

Anderson sprak toen de, voor mij althans, historische woorden: “pins are nice, but what we need in

the treatment is compression”.

Het tweede toeval was de hernieuwde ontmoeting met Ruud Bos, die, evenals ik en in ongeveer

dezelfde ti jd, was opgeleid in het Academisch Ziekenhuis Groningen, hij als kaakchirurg. Ik zag hem

op het feestje ter gelegenheid van het als tandarts afstuderen van de echtgenote van een van de

radiologen van mijn toenmalige ziekenhuis. Ruud was kort tevoren gepromoveerd op het gebruik

van polymelkzuur schroeven en platen in de kaakchirurgie en toen ik dat hoorde was mijn vraag

natuurlijk: mag ik wat van die schroefjes, want “what we need is compression”. De intra-articulairefj

toepassing van bioafbreekbare schroeven in gewrichten was in 1992 nog volledig onbekend en

dus kreeg ik de schroeven niet want het was onduidelijk wat de eventuele gevolgen van deze

toepassing waren. “Je zult toch eerst onderzoek moeten doen”, was het antwoord. Dit was dus het

begin. Toen bij de geitenproeven bleek, dat de toepassing van schroeven onaanvaardbare gevolgen

had, was de volgende stap lang onduidelijk en lag het “proefschrift proces” stil; ik kon niet verder.

Het derde toeval: na al enige jaren vele malen Meniscus Arrows® te hebben gebruikt voor het

herstel van gescheurde menisci, kwam de ingeving: als die Arrows nu eens in bot voldoende

houvast zouden hebben? Een serie trekproeven volgde en het uiteindelijke resultaat ligt er.

Hooggeleerde heer, prof. dr. R.R.M. Bos, beste Ruud.

Had je op die feestavond in Morra kunnen bevroeden, dat het zo zou lopen? Heel veel dank voor

je bezielende en onuitputtelijke inzet en het faciliteren tot het laatste toe. Ondanks de tijd die

verstreek bleef je in het project en mij geloven, waarschijnlijk toch tegen de kansberekening in, dat

ik het ooit zou afmaken. Ik ben enorm blij, dat ik mijn, niet uitgesproken, belofte van destijds heb

kunnen waarmaken.

Hooggeleerde heer prof. dr. J.R. van Horn, beste Jim.

Je hebt aan de wieg van dit “boekje” gestaan en hebt gezorgd, dat ik de basis kon leggen voor de

vorm van nu. Heel veel dank hiervoor.

129

Dankwoord

Hooggeleerde vrouwe, prof. dr. L.J.M. van Luyn, beste Marja.

Ik denk met plezier terug aan de uren lange microscoopsessies, waarin je langskwam, adviezen of

een opdracht gaf; op naar het volgende deel van het project. Heel veel dank voor jouw hulp en die

van de medewerkers van jouw afdeling bij het analyseren van de coupes van de geitenknieën, het

begeleiden van de proeven en het toewerken naar een conclusie.

Hooggeleerde heer, prof. dr. J.T.M. de Hosson, beste Jeff.ffff

Daar kwam dus een of andere chirurg uit Dokkum met de vraag of er wat trekproeven gedaan

konden worden. En daarna nog meer, en nog meer. Je moest maar geloven, dat dit allemaal niet

voor niets zou zijn! Heel veel dank voor jouw vertrouwen in mij en het geven van ruimte in tijd en

faciliteiten om aan mijn verzoeken te voldoen. De steun via jou, van de medewerkers van je afdeling,

is onontbeerlijk gebleken voor het bereiken van de resultaten, uiteindelijk leidend tot het tot stand

komen van dit proefschrift. Uko Nieborch en Paul Bronsveld, moeten in het bijzonder genoemd

worden. Dank voor jullie inzet, adviezen en daadwerkelijke inspanning bij het voorbereiden,

verrichten en analyseren van de trekproeven.

Chirurgenmaatschap Tilburg, beste maten.

Bij mijn acceptatie als maat, vanuit Dokkum komende, was een van de voorwaarden om binnen een

paar jaar te promoveren om zo het aantal gepromoveerden binnen de maatschap op het peil te

brengen dat vereist was voor het opnieuw verkrijgen van de opleiding heelkunde. Toen bleek, dat

mijn promotie hier niet meer noodzakelijk voor was ging, moet ik eerlijk zeggen, de druk wat van

de promotieketel af.

Ik ben blij en opgelucht, dat ik die belofte, weliswaar wat later, toch heb waargemaakt.

Drs. J.G.M. Burgerhof, beste Hans.

Weer zo’n dokter, die achteraf iets statistisch moet bewijzen. Ja.ja, het is onderzoek van een aantal

jaar geleden, maar toch. Echter, in die tijd was E.B.M. nog een onbekende term en de statistieken

niet zo prominent in de artikelen aanwezig. Je was van meet af aan bereid mee te werken en praatte

ons bij over de achtergronden van de gekozen statistische weg. Heel veel dank hiervoor.

Eduard Mooyaart heeft met veel inzet en enthousiasme de mogelijkheden geschapen om, tussen

het patiëntenonderzoek door, röntgen foto’s en MRI opnames van de geitenknieën te maken en

te beoordelen Dat ontlokte hem, bij het zien van het oedeem en caviteiten rond de schroeven,

de opmerking ”dat spul zou ik niet in mijn knie willen hebben”. Toen de histologie bekend werd,

bleek dat hij gelijk had. Helaas is hij al enige tijd geleden door ziekte overleden. Hiermee is een

vriend, wetenschapper en een goed en sociaal mens veel te vroeg heengegaan. Ik ben hem veel

dank verschuldigd.

Hooggeleerde heer, prof. dr. M. Kon. Helemaal in de beginfase van dit proefschrift maakte

ik kennis met U en kreeg ik van U 3 ordners met literatuur over kraakbeen, perichondrium en

kraakbeentransplantatie en het boekje “The Early History of Surgery”, dit laatste te leen. Ze zijn mij

tot groot nut geweest, waarvoor veel dank.

130

Dankwoord

Zeergeleerde vrouwe, dr.L J. Mouton, beste Noor. Dankzij jou kon ik aan humane femur condylen

komen voor mijn trekproeven. Heel hartelijk dank hiervoor.

Zeergeleerde heer, dr. R.A.A. Bots, beste Robbert. Vijf ordners vol literatuur die jij voor jouw

proefschrift verzamelde mocht ik voor een symbolische “wijngift” overnemen! Dit heeft absoluut

bijgedragen aan dit proefschrift en wat heeft mij dat veel tijd en werk bespaard. Ook de inhoud van

jouw proefschrift heeft me ondersteund en meerdere referentie’s naar delen van dit proefschrift,

dan wel uitspraken hieruit, mogen hiervan getuigen. Laat een eenvoudige, doch voedzame maaltijd

achteraf mijn dank nog verder onderstrepen.

Mevrouw M.B.M. van Leeuwen, beste Babs.

Zonder jouw zorg voor de reageerbuisjes met zwellende, dan wel degraderende Arrows was het

logistiek lastig geweest om alle proeven te doen. Bovendien heb je mij ook nog met raad en daad

bijgestaan. Heel veel dank.

Dick Huizinga en Peter van der Sijde, De heren van de medische fotodienst. Al vóór jullie

verhuizing naar de huidige afdeling in het faculteitsgebouw was ik bijna kind aan huis met vragen

over de dia’s, foto’s en zelfs “on the spot” fotografie. We fifi losofeerden wel eens over “het boekje” maarfi

dat leek zo ver verwijderd en onbereikbaar. Tot nu toe. Hier ligt het dan met een aantal van jullie

foto’s. Heel veel dank voor al jullie inspanning.

Mijn zoon Roderick en dochter k Philippine. De eerste een geweldige steun bij meerdere proeven,

de tweede bij de taalkundige correctie van mijn (hier en daar toch zeker niet correcte) Engels.

Als jij Roderick, toch was doorgegaan met de studie rechten en jij, Philippine, bij voorbeeld Russisch

als taal voor je studie had gekozen, had ik deze steun moeten missen en was de weg naar de

voltooiing langer en lastiger geweest. Ik er ben trots op wat jullie al bereikt hebben en kijk uit naar

wat jullie nog zullen bereiken.

Last but absolutely not least, lieve Petra. Je nimmer afl atende steun is een hoeksteen geweest bij fl

de bouw van dit werk. Ik heb gekozen voor een weg van gedeelde tijdsinvestering tijdens vakanties

en vri je weekenden, dus een deel familie en sociale contacten en een deel werken aan dit boekje,

in plaats van in ieder vrij ogenblik zitten schrijven in eenzame afzondering. Daarom waren de

weekeinden en vakanties vaak gebroken en heeft het langer geduurd voor dit proefschrift af was.

We gaan nú weer echt ónverdeeld genieten!

131

Curriculum Vitae

132

Diederick Bernard WoutersBorn: April 26, 1948

1967-1974: medical study, Free University, Amsterdam, The Netherlands.

06-09-1974: MD degree.

1974-1975: resident children surgery Sofia Children Hospital, Rotterdam.fi

1975-1976: medical offi cer Royal Dutch Navy.ffi

1977-1983: surgical resident, University Hospital Groningen, (prof.dr.P.J.Kuiijer).

1983-2002: general surgeon Hospital “Talma-Sionsberg”, Dokkum, fields of fi

interest: traumatology and arthroscopic surgery.

2002- present: surgeon TweeSteden Hospital, Tilburg; fields of interest traumatology andfi

arthroscopic surgery. Research topics: The application of Meniscus Arrows®

as fi xation devices in the treatment of intercondylar spine fractures infi

children, radial head fractures and a RCT on the treatment of Mallet fractures.

Evaluation of more indications.

Thesis related presentations:

1989: “The arthroscopic fi xation of osteochondral fractures with Orthosorb, using a new

device”, the University Hospital, Groningen; and the University Hospital of

the Free University, Amsterdam, The Netherlands.

1990: ”The Arthroscopic Fixation of Osteochondritis Dissecans Fragments, using

Biodegradable Pins” Congress on Biomaterials, München, Germany

1991: ”The arthroscopic drilling and fi xation with biodegradable osteosynthesis

material of osteochondral fractures and osteochondritis dissecans fragments, a

preliminary report.” International Association for Arthroscopy, Toronto, Canada.”

1992: ”Arthroscopic fi xation of osteochondral fragments using biodegradable material”.

Eurosurgery congres, Bruxelles, Belgium;

1993: ”Treatment of O.C.D., and the use of biodegradables?” Belgian Arthroscopy”

Association, Bruxelles Belgium.

1995: “The treatment of Osteochondritis Dissecans, using biodegradable pins

and screws, a comparative study in goat knees”; International Society for”

Arthroscopy, Kneesurgery and Orthopedic Sportsmedicine (ISAKOS): Hong

Kong, China.

1996: “The treatment of Osteochondritis Dissecans, using biodegradable pins and

screws, a comparative study in goat knees”Société International de Chirurgie, ””

Orthopédique et de Traumatologie (SICOT) congress, Amsterdam; the

Netherlands.

133

1996 – 2002: member of the board of the Dutch Arthroscopy Association, chairman of the

scientifi c –Eikelaar award committee.fi

1997: “The treatment of Osteochondritis Dissecans using biodegradables, fi ction or

future?”; annual congress of the Dutch Arthroscopy Association Ede, the ”

Netherlands.

2000: “The Riddle called cartilage”; 19de Bruco Sports congress, on invitation, Brugge; ”

Belgium.

2001: “The use of the Meniscus Arrow® for a new indication, mechanical tests”; ”

annual congress of the Dutch Arthroscopy Association: Ermelo, the

Netherlands.

2001: “The use of theMeniscus Arrow® for a new indication; mechanical tests”.

ISAKOS congress, Montreux, Switzerland.

Thesis related publications:

* Wouters DB. Is there a place for chondroprotective drugs (glucosamine en chondroitine

sulphate) in the treatment of arthrosis/arthritis or posttraumatic cartilage damage?

Vademecum permanent education General Practitioners 2000;18 (19):1 (in Dutch)

* Wouters DB. Is the use of cartilage protective drugs like glucosamine and chondroïtine benifi cial

in the treatment of arthrosis? Vademecum permanent education General Practitioners 2003; ?

21(10): 2–5 (in Dutch)

* Nelis R, Wouters DB. Is the Use of Biodegradable Devices in the Operative Treatment of

Avulsion Fractures of Fingers, the So-Called Mallet Finger Advantageous? A Feasibility ?

Study with Meniscus Arrows®. The Open Orth J 2008;2(4):pp.151-154

* Wouters DB, de Graaf, JS, Hemmer PH, Kramer WLM. The arthroscopic treatment of displaced

tibial spine fractures in children and adolescents using Meniscus Arrows® as fi xation devices.

Submitted.

134

135

136

137

Osteochondral fracture, the origin and the fragment elsewhere in the knee joint (Chapter 1, page 15)

Figure 3. An OCD lesion, fixed with (blue) biodegradable pins, some blood is oozing out of the drill holes. fi(Chapter 2, page24)

Figure 4. One screw and 2 biodegradable (blue) pins, 6 weeks after implantation. A thin layer of newly grown cartilage is covering a substantial part of the head of the screw. (Chapter 2, page25)

138

Figure 5. Two screws, arthroscopically inserted, to fix anfiOCD lesion. (Chapter 2, page26)

Figure 1 and 2(Chapter3, page 35)

139

Figure 3 (Chapter3, page 39)

Figure 4 (Chapter3, page 39)

140

Figuur 5a: loss of birefrin-gence in the PGA/PLA material at 12 weeks after implantation(Chapter 3; page 40)

Figuur 6 (Chapter3; page 41)

141

Figuur 7 (Chapter3; page 42)

Figure 1: The 2 devices tested: on top the A.O. screw with a diameter of 2 mmand a length of 15 mm below the Meniscus Arrow® with a length of 16 mm(Chapter 4; page 51)

142

Figure 3: the sequence of pulling out of the femur condyles (Chapter 6; page 77)

Figure 4: a: start of the extraction of the first Meniscus Arrow® from hole 1fi b: start of the extraction of the second Meniscus Arrow® from hole 2 (Chapter 6; page 77)

143

Figure 2: (Chapter 7;page 88)


144


Figure 5: (Chapter 7; page 91)

Documents

University of Groningen The use of biodegradable fixation