Argos SpineNews 1

April 2000

News from the world of Spinal surgery and biomechanics

Focus on :

Birth of Argos’ website

Spineview software

History of spinal surgery

When biomechanicsinterfaces with statistics

Fourth Argos meeting

The Montreal Imaging

and Orthopedics

research Laboratory

The Montreal Imaging

and Orthopedics

research Laboratory

A N O R T H O L I N K P U B L I C A T I O N

Fourth Argos meeting

Another step forward in communication between surgeons ! . . . . . . . . . . . . . . . .7

Argos

A new dimension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Organization chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

Members list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

3 partners, 3 orientations, 1 goal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

International training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

Birth of Argos’ Website . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

Web Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

History of spine surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

News . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

Functional testing of spinal implants . . . . . . . . . . . . . . . . . . . . . .18

SpineView - a tool designed to improve quality of care . . . . . . . . . . . . . . .19

Mechanical characteristics of rod . . . . . . . . . . . . . . . . . . . . . . . . .29

When biomechanics interfaces with statistics . . . . . . . . . .34

Numerical simulation of scoliosis surgical treatment .35

The Montreal Imaging and Orthopedicsresearch Laboratory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

Clinical case - Instrumentation in spinal fusion . . . . . . . . . . . . . . . . . . . . .43

S U M M A R Y

Evaluation

Communication

For more information,

bibliography, French

version, please log on to

Argos website.

www.argos-europe.com

News from the world of Spinal surgery and biomechanics

April 2000

Training

April 2000 - N° 1 ARGOS SpineNews 6

by Alexandre TEMPLIERARGOS General Manager - Editor in Chief

EDITORIAL STAF

Editor in chiefAlexandre Templier

Production/Art directorKarim BoukarabilaBoard of editors

the Argos committeeWriter/TranslatorAlexandre TemplierPatrick BertranouPhilippe Strauss

Assistant publisherCarl Stéphane Parent

Cédric Caloin

ARGOS COMITTEES

Communication Committee :

Patrick Bertranou, MDPhilippe Bedat, MD

Henri Costa, MDPierre Kehr, MD

Charles-Marc LaagerPierre Soete, MD

Training Committee :

Jean-Paul Steib, MDJean-Paul Forthomme, MD

Franck Gosset, MDFrançois Lavaste, PhDRichard Terracher, MDJean-Marc Vital, MD

Evaluation Committee :

Wafa Skalli, PhDJacques De Guise, PhD

Michel Dutoit, MDAlain Graftiaux, MD

Henry Judet, MDChristian Mazel, MD

Tony Martin, MD

EDITORIAL HEADQUARTERS :

ORTHOLINK (US)546 Hillgreen Drive, Beverly Hills CA

90212 USAPhone (310) 557-2000

Fax (310) 843 9500

ORTHOLINK (CE)33, rue Vivienne

75002 Paris FRANCEPhone (33) 6 08 43 82 81

Fax (33) 1 45 08 46 67

ARGOSSpineNews

VOLUME 1, NUMBER 1Editorial

Dear Members and readers,

First and foremost, on the occasion of the release of the first

issue of our journal “ARGOS SPINE NEWS”, we would like to

express our most heartfelt thanks for the tremendous response

on our previous journal. Your remarks and encouragement in

“The Connector” proved invaluable to us.

You have fully grasped the importance of communication in our

association and definitely contributed to helping us address

Argos’ members needs for information.

As you read through this issue, you will notice that ARGOS has

steadily expanded; the recent launch of our Internet site is ano-

ther mile stone toward better and larger communication with

the “Spine world”.

The consolidation of our three activities: Communication,

Training and Evaluation led us to expand our committees’ staff

who will undoubtedly make full use of our upgraded tools.

While preserving its spirit of creativity, rigor and friendship,

the introduction of additional training tools such as the Spine

Simulator, Argos Clinical Database and Spine View will boost

not only the efficiency of each one of us but and mostly enhance

the prestige and influence of Argos in the world.

With all of our best wishes for the new millenium !

Fourth Argos meeting… Another step forward incommunication between surgeons

Communication

The day was given over to lumbo-sacral Arthrodesis and to the painthat it can engender and dividedinto three parts tackling threemajor themes.

Post-operative pain:- premature- medium term- long term

These three cases are very differentand through analyses, actual casesand discussions we shall get toknow their specifics.

7 ARGOS SpineNews N° 1-April 2000

Premature post-operative pain

Professor Kehr and Doctor Gossetwere privileged to open thiscongress. They explained imme-diate post-operative pain. The mostpainful moment remains waking upand with it the fear of feeling dis-comfort. One can be confronted bya premature radicular pain causedby the bad positioning of screws.Remaining vigilant is therefore amust, especially if the patientshows signs of deficiency. A scanwould show a possible error in theline of the disc or screw diameter.The appearance of a haematoma ora possible unknown herniated discappears could also be detected.

The two authors finished theirexposé by concluding that the dia-meter of a well-chosen screwavoids haematomas and preventsother complications, it is nonethe-less necessary to be careful of pre-vious screw holes and that a curet-tage remains useful.

Presentation of immediate post-operative imagery was given byProfessor Dosch, who demonstra-ted the various useful criteria in thedomain of scanographyRadiography, scanning and IMRwere all touched upon.

Radiography is an very exact exa-mination to check for the correctpositioning of material. However acentred radiography, with detailedsection will allow for a good assess-ment, contrary to a standard radio-graphy which is far less effective.Scanners remain very viable withregard to imagery, especially in thecase of titanium screws, a satisfac-tion rate of 87% whereas screwsmade from chrome cobalt onlyregister a satisfaction rate of 68%.

As for IMR, it can analyse a rootperfectly if the material is in tita-nium, with any other material theresults would be nil or almost non-existent.He finished with the figure of falseroutes which is situated between 10& 40%, a figure which would seemto be associated with old statistics,and would be reduced to 0% werethere navigation.

Doctor Caux illustrated brilliantlythe explanation of treatment proto-col in post-operative pain. Severalpharmaceutical means were evokedupon.

First, AINS which is non-mor-phine solution and the most impor-tant treatment. It cancels the painchain, however with patients of 75

April 2000 - N° 1 ARGOS SPINE NEWS 8

and over one should remain vigi-lant.

Then there is paracetamol whichhas a central action but whichcreates allergies, morphine-basedanalgesic or codeine, dextropo-poxyphene and tramadol are grou-ped together, were all mentioned.Their effects are varied dependingupon the person treated.The use of morphine can be carriedout intravenously or with a PCApump. (90% Satisfaction). But eva-luation of the pain is very impor-tant. Drowsiness may ensue and itis an effect which should not beignored. In effect, adaptation foreach particular patient is necessary(Age and condition).

In conclusion, a strict and regularsupervision is indispensable.

The three orators went on to dis-cuss the origins of pain. If it provo-ked by a radicular compression,there is a risk of motor deficiency, aparaesthesia or a radicular inflam-mation.

However, care is necessary withregards to the nerve root which canbecome inflamed in which case thepain will be radicular or rachidian.

Doctor Mazel presented his interactive clinical cases.

Best poster reward : Doctor Viego-Fuertes

Doctor Kumano from Japan

9 ARGOS SpineNews April 2000 - N° 1

In all events, putting a drain inplace remains a possibility, but cer-tain surgeons who have carried outthis practice have noticed the out-break of infection.

The first medical case that DoctorMazel analysed was that of womanwho had been suffering over thelast six months from pain when wal-king. The surgeon who took her inhand did X-rays, but nothing wasdetected. She therefore underwentan IMR where a misalignment ofL4-L5 was seen. A “floating”arthrodesis was done and the resultwas satisfactory for despite inter-mittent pain, she was back walkingvery quickly. Meanwhile, this inter-mittent pain became more regularand the patient came back with adeficiency on the left-hand side.

The discovery of a weak disk wasmade in addition to which she suf-fered from temperature and urinaryinfections. She was admitted into are-education centre when severalweeks later the infection went intoremission.

The diagnosis of a post-operativespondylosis was made, she wasthen treated with anti-biotherapy,but there is a remaining doubt as towhat became of the damaged disc.

Medium termpost operatory pain

The second part of the congresscentred around medium term pain.Doctor Kunogi began by explai-ning the clinical analysis of lum-

bago after lumbar arthrodesiswhere he groups two categories :

- Twinflex- Rigid

The Twinflex category seems to suf-fer less ruptures than Rigid, (33 %

1 - M.Viejo-Fuertes was rewar-ded for his presentation duembryological development andthe importance of ligamentum fla-vum. Morphogenetic, anatomicand histological studies have beencarried out to demonstrate pro-prioceptive role of this yellowligament. The yellow ligament isderived from a mesenchymateuxtissue and develops with the ver-tebral structures, and this willmake the difference with theother ligaments.

2 - M. Claude Argenson made apresentation on an anterior endo-scopic graft in fractures.Two phases were exposed : - Mini-approach- Videoscopy

A lumbar fracture which is fixedby screws and median hooks ismuch more aesthetic.

3 - The last poster was that of M.Dutoit which shows the impor-tance of zygapophysis synovialcysts. It is a relatively rare lesionwhich causes troubles resemblinga paralysing hernia. It is the pos-ter which most held the public'sattention.

Posters selected for presentation.Three of the posters selected were retained by the participants.

This article will be

soon available in french at


Communication

Vote for poster presentations. As a conclusion, Professor Kehr gave us a synthesis of the whole day.


of ruptures). These ruptures aredue to screw problems. Generally,it is possible to notice that theybecome detached from the upperpart, which causes pain in the leg orin the lower back, pain which willdisappear once the nerve root hasbeen secured. Fractures of the pel-vic ring following a sacral-lumbarfusion increase by 5 % in women ofover 50.

These are the mechanicalconstraints which seem difficult toput up with.

The problems of pseudo-arthrosisin the context of an instrumentedarthrodesis were evoked upon byProfessor Vital. Re-operations forpseudo-arthrosis are due to variouscauses such as : smokers, discs pla-ced too high, the inadequacies ofgrafts.

When an IMR is carried out on apatient who has an instrumentedrachis, a persistent modic revealitself to be a suspicion for a pseudo-arthrosis. It is nonetheless neces-sary to wait for surgery before pro-nouncing a diagnosis. A patientwho can properly explain the painshe is suffering and who can placehimself correctly are an importantsource of prevention.

Then followed a presentation byProfessor Logroscino on the role ofanterior support in the preventionof post-operative pain. The PLIF(Posterior Interbody Fusion) singlelevel anterior support for an arthro-desis, was one of the points deve-loped for it is a system which allowsfor a renewal, a reduction and avery satisfactory alignment. Itsadvantage being that it allows a cir-cumferential arthrodesis, moreoverit is a less traumatic and cheapermethod.

The use of large surface cagesgives a far better result than smal-ler cages.

Finally, a good fusion is a guaranteeof the ridding of pain.

Pseudo-arthrosis and lumbago afterlumbar arthrodesis is a very impor-tant theory in the view of DoctorKumano. For him, the factors allo-wing alleviation of the pain :

- screws- cages

In fact, poly-axial screws seem farbetter for avoiding complicationsand consequently pain. Titaniumcylindrical cages are more accep-table, a multi-axial connection bet-ween the screws and rods (a verydemanding technique) provides anexcellent anterior fusion and avoidscomplications and lumbago pro-blems.

The discussion following lenttowards the necessity of the use ofcages. Several doctors participatedin this debate, M.Argenson toge-ther with several other colleaguesbelieved that are cages of interestbut in the event of further need forsurgery, it is necessary to increasein width, which is very tedious. ForDoctor Kumano, anterior fusion isnecessary especially if restoringthe height of the foramen, butothers, such as Professor Vital,

thought that height restoration isnot always necessary.

Finally, Doctor Kunogi pointed outthat isolated cages bring aboutcomplications and are more uns-table.

Doctor Mazel presented anothermedical case, concerning a 54-yearold woman suffering from a “repe-titive” discopathy, several proposi-tions of treatment were made fromthe assembly : Dr Vital would carryout a biopsy, Dr Logroscino a dyna-mic scintigraphy. In fact a arthro-desis was done and no post-opera-tive problem was detected.

After a year, however, the patientsuffered from lumbago pains. A dis-cography was carried out, post-ope-rative MRI shows complete reco-very. Long term problems In hisexposé on problems linked to lum-bago, Doctor Antonnetti spoke ofthe necessity to carry out previoustests. Patients must be listened toand observed. Signs of non-organi-city can be detected and it is thesesigns which indicate that the per-son is not a good candidate for sur-gery.

Spinal X-ray scanning and numerical analysis demonstrations.

11 ARGOS SpineNews N° 1 - April 2000

Functional surgery for non-functio-nal pathology is the key to success.Observing particular gestures ofthe patients such as : arrival (correctwalking, limping ), facial expression(grimace, smile), ease of undres-sing, muscular force and reflexes,allow an opinion to be forged on thenecessity to operate or not. Onesolitary sign of non-organicitymay not be sufficient to refuse tocarry out the operation.

After an initial general visualisationof the patient, Doctor Rohmer stu-died his psyche. For him, all lumbarpain has a psychological conse-quence, very often, patients do notwant to upset their daily livesbecause of their illness. Careshould be taken with hyperactivepatients for very frequently, it isthey who are incapable of freeingthemselves from work to find thetime necessary for their operation.Pain is no longer a physical sensa-tion, it is an intolerable phenome-non for society.

It must be remembered that “lum-bago is to the workplace whatmigraine is to conjugal duty”.

Professor Dosch showed keeninterest in long term imagery, heaffirmed that late complications

due to material are in the order of 1to 4%. Those linked to grafts are 3to 9%. The results engendered fol-lowing a standard radiography are68%, concerning an IMR afterablation of material, the results aresatisfactory but indirect, for thegraft must be sufficiently solid justas the pseudo-arthrosis. The scan-ner remains the surest examinationafter an ablation of material.However, it is indispensable totake detailed sections and interpretthe results with flexibility .

It is necessary to remain vigilant visà vis mechanical problems whichcan be based on two elements :

- recurrences- hypertonia

In a general manner, long term ima-gery provides results but it is neces-sary to wait for more precise ans-wers.

Criteria of non-organicity and theevaluation of the psyche were thebasis of the discussion that follo-wed. The radiologist and the psy-chiatrist do not have, according tothem, the power to decide, theycannot submit their opinions norremarks, the decision remains thatof the surgeon. It is certain that

patient's remarks such as “whateveryou do, it will not change a thing !”,are to be taken into account for asentence such as this is a criterionof non-organicity. The use of thecorset was mentioned at severalpoints as well as infiltration or dis-cography, tests which can be neces-sary.

Doctor Lazennec showed us how toadjust the position of an lumbo-sacral arthrodesis. To begin with itis necessary to evaluate the infil-tration, give attention to the sagittalbalance and try to localise the painwhich can come from the ligamentor the disk. The position pelvic canalso be at fault.

With regard to sagittal balance, it isnecessary to measure the sacrumswing (Sacral Tilting) which shouldbe equal to 41°, pelvic versionwhich should be at 12° and the inci-dence angle which on average mustnear to 53°.

The ideal solution would be toincrease the swing of the sacrumand to reduce the pelvic version.

Vertebral osteotomy for the flatback was presented by ProfessorArgenson. It is a safe interventionin several cases, it is necessary to

Communication


These informations,the bibliography orFrench version will be soonavailable onthe Website…



Those informations,the bibliography orFrench version will be soonavailable onthe Website…

localise the pain, correct the cypho-sis and carry out a posterior osteo-tomy. Results are not immediate,but the use of the median hookstechnique is very efficient. Ineffect, it gives a minimum conges-tion in the canal and avoids screwsbeing wrenched out, a large exten-sion is recommended in order toreduce compression.

It was Professor Guigui who thenexplained the outcome of the levelsabove and below. He showed twogroups, one being the patientsdecompresses with and the otherwithout arthrodesis, from whichthree worsening factors :

- arthrodesis- the importance of the time factor- use of instrumentation.

It should be noted that there is noclinical difference between the twogroups. It is certain that the indi-cation of arthrodesis must be reflec-ted upon.

The last debate of this congress ten-ded to wards the source of pain.The reminder of the rachis balancein relation to the hips was made.Doctor Lazennec reiterated hisidea that pain due to mis-positio-ning of the sacrum is lateral andthat they is almost certainly due tothe sacroiliac ligament as well asthe thoraco-lumber junction. Thepain for the arthrodesis in L5/S2 isbetter tolerated than that in L4/S2.Finally, Professor Argenson under-lined the fact that it is necessary toremain prudent in the large lumbo-sacral fixations for scoliosis.

Doctor Mazel also stated a medicalcase. It could be called 'a tale of suf-fering' The patient a 40 year oldman was a physical instructor. Heunderwent a hexatriolone injectionin L4/L5, then a chemical arthro-desis. (something which no longertakes place. Three years later, hecomplains of pain and an laminec-tomy is done.

He improves, but two years later,

the appearance of lumbago is evi-dent. He undergoes new X-rays,but nothing is detected.

The question now is: What to donow for this patient who is nowincapable of covering a distance of100 metres ? ■ PS.

73 rd Annual Meeting of the Japanese OrthopaedicAssociation6-9 April, 2000 - Kobe JAPAN - Information : +81 78 382 5985E-mail: [email protected]

Paediatric Orthopaedic Society of North America1-4 May, 2000 - Vancouver CANADA - Information : 847/384-4246E-mail: [email protected]

27th European Symposium on Calcified Tissues6-10 May, 2000 - Tampere FINLANDE-mail: [email protected]

7th Congress of AOLF10-13 May 2000 - Beyrouth LIBAN - Information +961 1 613 619(fax)

55 th Annual Meeting of the CanadianOrthopaedic Association3-7 June, 2000 - Alberta CANADA

Spine Across the Sea III(Joint Meeting with the Japanese Spine Research Society) 23-27 July 2000 - Kamuela HAWAI - Information +1 847 698 1630

First Interdisciplinary World Congresson Spinal Surgery 27 August to 1 September 2000 - Berlin GERMANYInformation +49 30 857 903 0

12th conference of the European Societyof Biomechanics27-30 August, 2000 - Dublin IRELAND - Information : 353 1 667 1713.E-mail: [email protected]

ISO Congress11-15th September 2000 - Stockholm SWEDEN

Eurospine 2000 10-14 October 2000 - Antwerp BELGIUMInformation +32 3 240 20 40 (fax)

16 th Meeting of the North American Spine Society31 October-3 November 2001, Seattle WASHINGTONInformation +1 847 698 1630

Agenda

ArgosA new structure,for a new dimension

Communication

Some four years ago, when itwas created, ARGOS setitself the task of promoting

information, training and evalua-tion in the treatment of spinalpathologies. An authority givingpride of place to clarity and dia-logue, it has kept clear all along ofany dogmatism and striven to allowthe scientific debate to range overthe widest possible field. It is earlydays yet to appreciate how such acomplex part translates to publichealth. Yet ARGOS has managed tocarve out a one-of-a-kind place foritself and now stands alone in itsown right in today’s context of ever-increasing deontological require-ments. It convenes on a yearlybasis, makes for easier face-to-facemeetings between clinicians (morethan 30 clinicians from differentcountries have been welcomed in1999 into Argos training centers),and promutes research schemes(Spineview, clinical follow-up) andtraining programs (in situ contou-ring for the correction of deforma-tions, dynamic fixation of the lum-bosacral spine). It also makes itspresence felt in the field of evalua-tion. It is firmly geared to collectand survey clinical data, and hasmoved further into the productionof annual morbidity reports. As apointer to ARGOS’ global visionand commitments, the associa-tion has spread across nationalboundaries and enjoys fast glo-bal expansion. It branched out inBelgium last year, and Japan hostedlast March the first non-European-based annual event focusing ondynamic instrumentation.

Argentina saw in last september thefirst edition of an annual eventdedicated to dynamic fixation of thelumbosacral spine and the correc-tion of deformations by the in situcontouring technique.

Three advisory committees

Intense technological changes, andnotably the advent of the Internet(see the article on ARGOS Website), are set to step up diffusion,both geographically and in scope.Such a context of fast expansiononly fueled the rationale for revam-ping the European mother entity. Amajor overhauling of the organiza-tional framework simply had to beundertaken to adapt to new requi-rements, as a very real and practicalway of supplementing the effecti-veness of the association. ARGOSannounced three multiprofessio-nal teams involving surgeons, bio-mechanical engineers and peoplefrom managerial spheres. They areexpected to lay down guidelinesand manage the association’s keymissions. They will be centered ona structure organized into threeadvisory committees that willinclude the Communication sec-tion, the Training section , and theEvaluation section . The commit-tees will convene twice a year andare meant to be most effective ins-truments in maximizing the efficacyof the actions undertaken by theassociation. For example, theEvaluation comitee will be expec-ted to audit evaluation centers andissue “methodological labels” that

will be the guarantee that everyevaluation approach reaches thehighest requirements of reliabilityand quality. The Training comitee,for one, will be expected to audittraining centers and deliver agree-ments.

A viable and productivegrowth

ARGOS’ members sitting on theboard, and who may or may not siton the various committees, willnaturally add to global cohesion.Intercommittee informatory circu-lars and Argos’ Web site will alsomake for an easier two-way flow ofinformation. Transcommittee coun-cils may also be contemplated at alater stage. ARGOS, a scientificsociety with a global vision, hasnow reached maturity and comeinto its own with unique resourcesto allow clinicians and researchersto take an active part in the globalsharing of views on the issues ofspine surgery. It is time the asso-ciation shifted towards an organi-zational framework better suited toand consistent with thespecificity of its goals. Only thenwill it derive full benefit from thescope of it members’ expertise andenjoy a viable and productivegrowth. ■ AT.






Organization chart

ChristianMazel, MD

President

Jean-PaulForthomme, MD

Vice President

AlexandreTemplier, Msc, PhD

General manager

PierreKehr, MD

Executive secretary

AlainGraftiaux, MD

Treasurer

Communication committee

Training committee

Evaluation committee

WafaSkalli, PhD

President of thecommittee

JacquesDe Guise, PhD

MichelDutoit, MD

AlainGraftiaux, MD

ChristianMazel, MD

Juan AntonioMartin, MD

HenryJudet, MD

PhilippeBedat, MD

PierreKehr, MD

Charles-MarcLaager


HenriCosta, MD

Jean-PaulSteib, MD

President of thecommittee


FranckGosset, MD

FrançoisLavaste, PhD

RichardTerracher, MD

Jean-MarcVital, MD


Thank you for your contribution !we will see you next year…


ARGENTINADr. Yvan R. AYERZADr. Juan Pablo BERNASCONIDr. Boan OSVALDO FERNANDEZ Dr. Frederic J. GELOSIDr. Felipe Zubiaur LANARIDr. Carlos Aroldo LEGARRETTA Dr. Luis A. PATALANODr. Pablo PLATERDr. Victor G. RAMANZINDr. Gustavo RAMIREZDr. Gabriel ROSITTODr. Victor ROSITTODr. Tomas RÜDTDr. Eduardo SEMBER Dr. Carlos A. SOLA Dr. Gustavo Roberto ZISUELA

BELGIUMDr Henri COSTA* Dr. Guido DELEFORTRIEDr. Damien DESMETTE*Dr. Sabri EL BANNA*Dr. Jean-Paul FORTHOMME* Dr. Jean LEGAYEDr. Frédéric MATHEI Dr. Yves RYSSELINCKDr. Pierre SOETE*

BRAZILDr. André Rafael HÜBNER

CANADAPr. Jacques DE GUISE

CHINAPr. John LEONG

FRANCEDr Joseph ABIKHALILDr. Michael ALBERTPr. Claude ARGENSONDr. Xavier ARTIERESDr. Mohamed Kamel BENCHENOUF Dr. Robert BOUVETDr. Ilhem CHERRAK Pr. Denis CORDONNIER* Pr. Alain DEBURGEDr. Jean-François DESROUSSEAUX*Pr. Jean-Claude DOSCHDr. Brice EDOUARDDr. Gilles GAGNADr. Franck GOSSET*Dr. Alain GRAFTIAUX*Pr. Pierre GUIGUIDr. Michel GUILLAUMATDr. Pierre HEISSLERDr. Henri JUDET*Pr. Pierre KEHR*Pr. François LAVASTE*Dr. LEONARDPr. René LOUISDr. Jean-Luc MARMORATDr. Christian MAZEL* Pr. Serge NAZARIAN

Pr. Michel ONIMUSDr. François PODDEVINDr. Olivier RICART Pr. Gérard SAILLANT Pr. Jacques SENEGASDr. Wafa SKALLI* Dr. Joël SORBIER*Pr. Jean-Paul STEIB* Dr. Alexandre TEMPLIER* Dr. Richard TERRACHER*Pr. Jean-Marc VITAL*

GERMANYDr. Ferdinand KRAPPELPr. Andreas WEIDNER

GREECEPr. Demetre KORRES*

HUNGARYDr. Tamas ILLES*

ISRAELDr. CASPI

ITALYDr. Flavio BADODr. Paolo BONACINADr. Luigi CATANIDr. Vincenzo DENAROMr. Charles-Marc LAAGER*Dr. Tonino MASCITTIPr. Giovanni PERETTI*Dr. Carlo PIERGENTILIDr. Dario RODIODr. Michele Attilio ROSA

JAPANDr. Kiyoshi KUMANODr. Jun-Ichi KUNOGI

LUXEMBOURGDr. Adrien WIJNE*

THE NETHERLANDSDr. Willem F. LUITJES

PORTUGALDr. Luis DE ALMEIDADr. Joao CANNAS

ROMANIADr. Mihai JIANU

SENEGALDr. Seydina Issa Laye SEYE

SOUTH AFRICADr. Johan WASSERMAN Honeydew

SPAINDr. Fernando ALVAREZ RUIZ Dr. Diego BRAGADO NAVARRO Dr. Sergio CABRERA MEDINADr. Alfonso CAMPUZANODr. J.M. CASAMITJANA FERRANDIZ Dr. J. Ignacio CIMARA DIAZDr. Jose Maria CORBOCHO GIRONESDr. Alvaro DE BLAS ORLANDODr Jose Antonio DE MIGUEL VIELBADr. Angel Jorge ECHEVERRI BARREIRO* Dr. Manuel FERNANDEZ GONZALES Dr. Fernando FERNANDEZ MANCILLADr. Luis Antonio GARCIA Dr. Antonio GIMENEZDr. Francisco GONZALESDr. Ernesto GONZALES RODRIGUEZDr. Angel GONZALEZ SAMANIEGODr. Cesar HERNANDEZ GARCIA Dr. Carlos HERNANDO ARRIBASDr. Juan HUERTADr. Alberto ISLA GUERRERODr. Manuel LAGUIADr. Rafael LLOMBART AISDr. Juan Antonio LOZANO-REQUENADr. Carlos LUNADr. Antonio MARTIN BENLLOCH*Dr. Jose Ignacio MARUENDADr. Cesar PEREZ JIMENEZDr. Enrique RODA FRADEDr. Manuel SANCHEZ VERADr. Hugo SANTOS BENITEZ Dr. Jose Luis SOPESEN MARINDr. Agustin VELLOSO LANUZA Dr. Javier VICENTE THOMAS Dr. Julio Alfonso VILLAR PEREZ

SWITZERLANDDr. Philippe BEDAT* Pr. Michel DUTOIT* Dr. Bernard JEANNERET Dr. Denis KAECH Pr. Thierry SELZ

SYRIADr. Taha ALOMAR

TUNISIADr. Mohamed Habib KAMOUNDr. Mondher M'BAREKDr. Mongi MILADI*

UKDr. Constantin SCHIZAS

USA Dr. Fabian BITAN*Pr. Jean-Pierre FARCY* Dr. Eric JONESDr. David LANGE Pr. Joseph MARGULIES Dr. William RODGERSPr. S.M. REZAIAN

Argos’ members list

* full members being entitled to sponsor


The LBM-ENSAM (Biome-chanicsLaboratory of the Ecole

Nationale Supérieure d’Arts &Métiers in Paris), directed byProfessor LAVASTE who began hisfirst in vitro experiments withProfessor ROY-CAMILLE in 1972,is today one of the most importantbiomechanics research centers inthe world. Its works on in vitroexperiments, numerical modelingand morphological & functional invivo measurements, are applied tothe study of Spine, Knee, Hip,Shoulder, and generally to thewhole skeleton including musclesand ligaments. The LBM, affiliatedmember of the CNRS (FrenchNational Center for ScientificResearch), got the EuropeanCOFRAC certification concerningIn Vitro testing of spinal implants.

Five years of research (1995-2000),achieved in collaboration with fiveof the main French Spinal surgerydepartments, allowed the LBM-ENSAM for a comprehensive ana-lysis of methods & parameters forspinal implants evaluation. Theactive and sustained involvement ofthis laboratory in the InternationalStandard Organization conventions

of the Technical Committee 150(Osteosynthesis, chairman : JohnKirkpatrick - USA, secretary : MarkMelkerson - USA) as official repre-sentative of the AFNOR, allowed it

for bringing its contribution toworks led by the ASTM(American Society Testing for &

Materials). (Including theCorpectomy test method describedby “Cunningham”, see figure 1).

The LBM is today responsible, ondecision of the countries represen-ted in the ISO TC 150, for the wri-ting of a complementary standardon functional testing of spinalimplants.

After this preliminary period, vali-dation, synthesis and writing of thisstandard has still to be done. To doso, the LBM-ENSAM is currentlypreparing a project involving indus-trial partners interested by contri-buting to this work, with the help ofthe French ministry of Economy,Finances and Industry.

Eurosurgical, Scient’x, Medtronic,Euros, Stryker, Sulzer, Kisco, LNE,CRITT Champagne-Ardennes, CEAand AFNOR have already applied tobe involved in this project.

The LBM-ENSAM invites the pos-sible sponsors and private partnersinterested by this project to takecontact with the LBM at:(33) 1 44 24 63 64 (tel),(33) 1 44 24 63 66 (fax).

The next meeting of the ISOTC150 will take place toStockholm (Sweden)from September 11th to 25th 2000

Evaluation

Figure 1

Functional testing of

spinal implants :An ISO TC150 New Work Item

Professor François Lavaste

table, a radiographic film proces-sing software has been recentlydeveloped by Claude Kauffmann,Benoît Godbont and Adib Benm’Barek (Laboratoire de rechercheen Imagerie et Orthopédie – LIO –of Montréal), as suggested byJacques De Guise, Director of theLIO. This software, calledSpineview, offers the same preci-sion of measurement and the samereliability as the manual protocol(for example, precision of ± 1.5° forintervertebral rotations).

For the user, the first step consistsof digitizing x-rays with a scanner.Digital images can then be integra-ted into the patient's file, or storedindependently on a database suchas ARGOS Clinical Follow-upDatabase. Two possibilities areavailable at this stage: either directon site data processing using a com-puter, or transfer of data by E-mailto our processing laboratory, whichwill return the results after analysis.Centres not equipped with digitalimage acquisition systems can alsosend x-rays by mail: they will bereturned to the hospital departmentwith the results of computerizedprocessing.

was possible to define a standardprotocol allowing the acquisition of15 dynamic and postural parame-ters under uniform and reprodu-cible conditions: a long axis lateralfilm, including C2 and the femoralheads, to quantify pelvic and spinalparameters (sacral angle, pelvictilt, total inclination of the spine,etc.); two lateral lumbar dynamicfilms (flexion-extension) to measurethe amplitude of intervertebralsagittal rotation and to locate themean centres of rotation. This pre-cise measuring technique was pre-sented by Alexandre Templier atthe last SOFCOT meeting in Paris(preliminary multicentric studydesigned to validate the principle ofthis protocol and to evaluate itspotential).

Initially performed on a digitizing

Every surgeon must criticallyexamine the sound basis ofthe treatments proposed to

patients. But is he really equippedto analyse the technical perfor-mance, security and benefits rela-ted to the use of a given techniquein comparison with the availablealternatives? Using lumbar verte-bral instrumentation as an example,regarding to the diversity ofimplants and associated surgicaltechniques, the credibility of thisapproach must be based on a rigo-rous and explicit method designedto objectively assess and comparethe efficacy of the various strategiesproposed.

Be easily integrated into rou-tine clinical practice

Although some authors have pro-posed useful quantitative anatomi-cal parameters, a simple and com-plete protocol allowing quantitativeanalysis of anatomical, postural andkinematics parameters in patientsundergoing lumbar fusion has notbeen available to date. With anextensive experience in modellingand statistical analysis, the ENSAMbiomechanics laboratory of Paris(LBM), in close collaboration withfive major French spinal surgeons(Pr. Dubousset, Dr. Mazel, Pr.Passuti, Pr. Saillant, Pr. Vital), hasinvested in the development of aclinical and radiological protocolwhich can be easily integrated intoroutine clinical practice, throughthe PhD Thesis of AlexandreTemplier, directed by Dr. WafaSkalli, co-director of the LBM.With a few minor adjustments ofthe procedures generally used ineach of the participating centres, it

Spine view : a tool designed to improvediagnosis & follow-up

Evaluation

Postural analysisDynamic analysis

Rough delineation of vertebral body contour

Automatic vertebral body contour

Automatic registration between the flexionand extension vertebral body contours

Numerical calculation of dynamicand postural parameters


Complete dynamic and postu-ral analysis takes only 10 to15 minutes.

Postural analysis simply consists ofdigitizing the usual anatomicallandmarks (to ensure greater preci-sion and to facilitate these measu-rements, geometrical elementshave been introduced into thisdigitization step). Dynamic analysisconsists of clicking on severalapproximate spots around each ver-tebral body, on flexion and exten-sion films. A processing algorithm(outlining and superimpositiontechnique designed at the LIO inMontréal) then automatically andprecisely determines the exactcontour of the vertebral bodies, anddeduces the dynamic parameters.At each step of the process, the useris able to qualitatively control auto-mated processing of digital data andthe plane of visualization of the x-rays. For example, the film super-imposition function allows manualcorrection of an unsatisfactory auto-mated result. Complete dynamicand postural analysis takes only 10to 15 minutes.Preoperative parameters determi-ned in this way can provide a realaid to diagnosis. Analysis of post-operative assessments in the light ofthis quantitative information couldalso be very useful for patient fol-low-up, particularly for the analysisof any complications. Other poten-tial applications would be analysisof the influence of the type of ins-trumentation on the residual mobi-lity of fused segments, evaluation ofthe mobility of segments adjacentto the fusion, and diagnosis of non-union or hardware failure.Assessment of correlation betweenposture and intervertebral mobilitywould be another possible line ofinvestigation. With this tool, theconcept of the mean centre ofintervertebral rotation, a theoreticalparameter proposed by Pearcy inthe 80’s only accessible, up untilnow, to researchers, would acquirea greater field of clinical applica-tion. Now that this parameter is

more readily accessible, it wouldnot be unrealistic to imagine thatthis concept could soon become anindex of disc “instability” even-tough the concept of spinal “insta-bility” has still to be clarified.To further develop integrated com-puter management, Spineview hasbeen linked with the ARGOSClinical Follow-up software. Forthe purposes of comparison, inte-gration of parameters related to dia-gnosis, surgical procedure andpostoperative course, as well asquantitative postural and dynamicdata, should greatly improve thelevel of scientific evidence for theconclusions formulated in studies.

a valuable tool for retrospec-tive and medicolegal assess-ment

Although there is still room forimprovement, this method consti-tutes a real progress in the search

for better assessment of thepatient's condition and the proce-dure performed, and represents asource of information with an enor-mous potential. This tool alsomakes a considerable contributionto medical device vigilance sys-tems, as it meets precision and rele-vance criteria which should make ita valuable tool for retrospective andmedicolegal assessment. If a largenumber of scientists and hospitalsurgeons adopt this common refe-rence, our speciality will have a realchance of conducting studies inwhich the clarity of the objectives,the rigorous methodology and thepractical value of the results willhelp to further our knowledge ofspinal fusion. ■ PS.





5TH InternationaArgos meFRIDAY JANUARY 26TH 2001, PARIS - MAISON DES ARTS

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A spine

leetingS & MÉTIERS - 9BIS AV. D’IENA PARIS XVI

odyssey

For any association who wantsto achieve global reach, theInternet is the only way to go.

ARGOS SPINE NEWS, the officialjournal of the ARGOS association,is proud to announce the launch ofits electronic counterpart: theARGOS Web site.

It is now available at www.argos-europe.com, and reflects ARGOS’commitment to active and efficientcommunication.

Easy point-and-click access

This site is in English and is desi-gned to supply information to ourmembers and to introduce ourassociation. It is fast and convenientto use, and lets the user accessinformation on our services andproducts.

There is also a presentation onARGOS’ mission and the composi-tion of its committees.The user can also search througha database for events in orthope-dics, and browse through the list ofthe articles in ARGOS’ scientific

library. The site also featureseasy point-and-click access to thebest sites with extensive spinalsurgery focus. Soon to be added,which will make it a truly interac-tive site, will be the discussionforum.

Even though separated by vastgeographic distances, users willcommunicate and exchange infor-mation freely and expediently,which is one of the foundations ofArgos’ existence.

An ever-improving medium.

The ARGOS site is intent onremaining an ever-improvingmedium. Your opinions and sug-gestions to improve our efficiencyare welcome and desired. Pleasesend them to the following address:[email protected]

PS.

The Launch

of Argos’ Web site :http://www.argos-europe.com

Communication





Spine-health gives very detailedinformation on spinal pathologiesand related subject, such as dia-gnosis, surgical techniques andmanual therapy. Articles includethumbnails you can click on to getfull screen pictures.

www.srs.org

The SRS site is an institutional siteand presents research on scoliosis.It includes a great deal of informa-tion on varied pathologies : you mayfind detailed glossaries as well assearch browser on medical articles.

www.espine.com

The Medical Doctors as individualsalso offer high quality home pages ofquality as this site demonstrates bybeing devoted to practitioners andpatients. Comprehensive informationabout spinal surgery is presented in avery simple way. The interface iswell-spaced, clear, and pleasant. ■

deph definition. You will also findthe agenda of congresses and havepossibility to subscribe to the mai-ling lists of differents specialities.the home page is clearly composedwith an English/French interface.

www.orthogate.org

A must-see site as far as classifica-tion and referrencing are concer-ned; you will also have access to afabulous list of links. From institu-tional sites to internationnal newsgroups, every category is listed.The interface is multilingual, thepresentation is user-friendly andthe loading is fairly fast.

www.spine-health.com

www.orthopedie.com

As complete as possible, this siteprovides you with a series of detai-led clinical cases that you can dis-cuss on the forum. You can also buybooks and videos or find severaluseful services. the screen displayis fast although we regret a certainausterity in the interface.

www.maitrise-orthop.com

The site is composed of variousinterviews, case studies and medi-cal glossaries, the mass of informa-tion is presented in an encyclopae-dic manner : outstandinglyillustrated, numerous medicalexplanations, glossaries and in-


Web ReviewThe orthopedic surgery is presented on the internet in various

forms. From academics institutions to enthusiastic medicalpractitioners, but also through commercial sites, you will

have access 24 hours a day, to data, services and products. Tosave time, here is a selection of links taking into account thecontent, presentation, and downloading time.


Spine surgery and, conse-quently, its history wouldhave been very different if

Man had not evolved to a standingposition and subsequently imposedmany different deformations to hisspine. As a consequence of theinterest these deformations andpathologies always aroused, here isan opportunity to draw links bet-ween more or less famous charac-ters who contributed to the deve-lopment of orthopedics in general,and to the study of the spine, in par-ticular.

Edwin Smith’s Papyrus is known asthe oldest surgery treatise. ThisEgyptian papyrus was written in2645 B.C. by Imhotep, a well-known architect who designed thestep pyramid in Saqqara. He des-cribed in it 48 different bone

lesions. Tutankhamen(1361 -1343 B.C.)

personally contri-

buted in a way to our subject. TheX-ray of his mummy taken by JE Harris in 1944, revealedthe first cervical laminec-tomy performed in his-tory, but the therapeuticreasons for this opera-tion are yet unknown.This pathology maybe associated to themurderous inten-tions of a rival to thethrone as one of theassumptions maderegarding the causeof his death.

The Greeks asAlcmaeon (approxima-tely 500 A.D.), a physicianat the academy of Crotonand disciple of Pythagorasand who detected canals actingas links between the organs and thebrain of Man, were intrigued bythose facts. However, the best

known of them all undoubtedlyremains Hippocrates (460-

377 B.C.). The author ofthe Corpus Hippo-

cratum associatedthe prognosis ofsome spinal gib-bosities with the

lungs. To correct afew deforma-tions, he sugges-ted a dual trac-tion on theshoulders andthe legs associa-

ted to a tension that was sometimesexercised as the practitioner sat onthe hump. The patient was lyingdown on a Scammon equippedwith hoists and pulleys. It was avery early ancestor of our modernframes. In Rome of the SecondCentury after Christ, Galen (131-201 A.D.) updated the location ofthe 4th cervical vertebra at the levelof the medullary core of the dia-phragm. The fact that he was thephysician in charge of arenas andgladiators must have facilitated hisinvestigations.

Evaluation

History of

spine surgery

From an article by R. Roy-Camille




The work of the 'elders' influencedmedieval scholars. The oldest sur-gery treatise known in WesternEurope, the Rogerine, dates backto the 12th century and includesRoger of Parma comment aboutTraumatology and gave a descrip-tion of nascent anaesthesiology.

In Bologna and later on, in Verona,William of Salicet (1210-1277) des-cribed in a surgical technique trea-tise the portals of entry to the limbsand the different types of post-trau-matic paraplegia. Let us not forgetthe essential role Arab medicineplayed in those times however thesole mention made to vertebral sur-gery is found in At-Tasrif (Practices)published by Abulcasis who livedand worked in the heart of the cos-mopolitan Cordoba.

Later on, surgeons began to leaveItaly in the wake of the Guelf-Ghibelline wars and many immi-grated to France. Guido Lanfranchipublished his Chirurgia MagnaPractica in Lyon in 1296 and des-cribed neurotomy for recurringpain.

Many who rediscoveredHippocrates during theRenaissance followed his exampleand devised instruments intendedto correct vertebral deviations.Ambroise Paré (1509-1590), themost remarkable of them all, contri-buted extensively to spine surgery.In his complete works published in1575, the author surprised us all ina chapter entitled On fractures ofvertebrae or spine wheels and theirapophyses or projections. He defi-ned traumatic paraplegia and sug-gested an operative procedure butno record of its application exists.His influence may explainGarrison's remark: “until (…) thesecond half of the 18th century, sur-gery was completely in the hands ofthe French in Paris”. Thus, theword 'orthopaedics' was coined byNicolas André in his Orthopaedicsor the art of preventing body defor-mation in children published in1741. On a lighter note,

Dupuytren's bimalleolar fracture isknown in English-speaking coun-tries as Percival Pott (1714-1788)fracture. Although Pott describedthis fracture accurately, his contem-poraries mainly remembered thathe suffered from it. It was not untilJacques Mathieu Delpech publi-shed his results in Montpellier in1816 that Pott's disease was in fact,established as vertebral tuberculo-sis.

Hippocrates had already describedthe association existing betweensimple deviations of the spine andtuberculosis, but the modestadvances made in the 18th centurycannot be ignored. Bloodless sur-gery with soft and progressive ver-tebral reduction techniques wasrecommended. The work of theLevacher brothers (1732-1816 and1738-1790 respectively) and AndréVenel (1740-1791) illustrates thisevolution which the nursing homesof that period benefited success-fully from.

The enthusiasm raised by Sciencesand Technologies from the 19thcentury onwards intensified therate of discoveries. It was a revivalfor spine surgery. Although R. Roy-Camille's paper mainly deals withcontemporary history, let us quicklymention Boehler and his role in theorthopaedic treatment of spinetrauma, Harrington whose rodrevolutionized the treatment ofscoliosis in 1961 etc.

This retrospective is a sketch of thehistory of spine surgery that under-lines the importance of individualas a guide. An intellect whose ini-tiatives are promulgated to advanceand circulate his ideas amongst dis-ciples who are sometimes wonover by his charisma. In that thephysician is different from the engi-neer who often works under secret.Still, no matter how rich his ideasare, he must confirm his intuitionswith evident facts to establish thelevel of confidence that is the hall-mark of fruitful exchanges.. ■

Introduction

Current surgical treatments of spinal disorders aremade with various anterior and/or posterior instru-mentation combined with different surgical tech-niques. The majority of existing segmental instrumen-tation is represented by multi hook-wire-screw androd systems (1), in order to reach the two main goalsof the spinal surgery: the surgical correction and thesurgical stabilization. The combination of theseimplants enable to realize constructs for which mecha-nical properties are essentially defined by the dimen-sions of the rod and the chosen material (specified bythe ASTM and ISO standards (8)). This is the reasonwhy this article will focus on the rod characteristics.

Surgical considerations

Rod characteristics are especially important in spinaldeformation surgical treatments. During this type of sur-gery, there are two main stages: contouring of the rodand correction of the spine. Different techniques areavailable, using the rod as inductor of correction:rotation technique, translation technique and in situcontouring technique (3, 4, 5, 6).

For rotation and translation technique (first group), therod is contoured to the profile desired for the correction.On the opposite, the in situ contouring group needs mul-tiple contourings of the rod, firstly for insertion,secondly for correction. Considering these features, thecharacteristics of the rod for the two groups can be dif-ferent. For example the malleability of the rod needs tobe rather low for the first group. For in situ contouringgroup, malleability needs to be higher.

If these specifications are not respected, some troublesmay appear : for the first group, if the malleability is toohigh, the rod can be unintentionally deformed duringcorrection. For the in situ contouring group, if the mal-leability is too low, large bending actions may thereforefollow the contouring of the rod and as a consequence beresponsible for an overstress on the spine.

So, the choice of the material for the rod is very impor-tant regarding the technique used for the spinal defor-mation surgery. As there are differences in tensilestrength, elasticity and plasticity among the differentavailable rods on the market, it is important that themechanical properties of the rod be understood andtaken into account prior to their use.

Biomechanical considerations

An important distinction must be made between severalterms which are often confused : Elasticity, Plasticity,Rigidity, Stiffness, Malleability, Strength, etc... Beforegoing into details of the previous terms, it is necessaryto understand that the bending effort F on a rod and theangular displacement α obtained follow a well-establi-shed curve tense length (fig 1). On this curve, we willfind several zones and points to which a specific voca-bulary is applied.

When the rod is working in its Elastic zone (F<ElasticLimit Point Fe on Fig 2), the deformation appears to belinear and is reversible. The material will revert to its ori-ginal shape when the force is no longer applied. Thecreated deformation is not permanent and the rodreturns to its previous shape.

When the rod is working in its Plastic zone (F>ElasticLimit Point Fe on Fig 3), the deformation appears to benon linear. When the force is applied, the material willfirst go through an elastic stage until the Elastic LimitPoint Fe is reached. Beyond this point, the material willnot return to its initial shape but goes to a new one whenthe force is no longer applied.

The concept of Rigidity (or Stiffness) and Elasticity isspecific to the slope of the linear deformation. The stee-per the slope, the higher the rigidity : you need a grea-ter force to obtain a (non permanent) deformation. Thelower the slope, the higher the elasticity.

The Malleability of the rod is characterized according tothe importance of the plastic zone (fig 4). The larger thePlastic zone is, the more malleable the rod is.


Mechanical characteristics

of the rod in spinal surgeryImportance of the proper rodmaterial choice

Evaluation

Emeric Gallard Msc Eng*,Jean Paul Steib MD**,

Patrick Bertranou MD***,Raphael Dumas Msc Eng*,

Alexandre Templier PhD*

30

The uses of a malleable rod does not affect rigidity of theconstruct (on fig 4, the slope of the linear deformation isthe same for the two kinds of rods). A construct made withmalleable rod offers identical or superior stress resistancethan a construct made with standard rod and integrity ofthe rigidity of the construct is preserved.

Caution : it is important to remember that reducing thediameter of a rod is not the good solution to contour easierthe rod. Indeed, even if the forces applied to obtain a per-manent deformation are lower (Fe’<Fe on fig 5), the elas-tic return of the rod is higher (α’>α on fig 5). Moreover,diameter reduction will lower the rigidity of the rod (theslope of the linear deformation is lower).

What about surgery ?

Many surgeons use the in situ contouring technique inassociation with other methods for spinal correction (2).It is well documented (7) that when a rod with inadequatemechanical characteristics is used for in situ contouringmanoeuvers, it has, due to the elastic return of the metaldeformation, to be bent well over the desired contour tobe achieved. Using such an inappropriate rod, themaneuver creates an increased tension of the anterior lon-gitudinal ligament (7).

The rods described and tested in the Bridwell (1) and Voor(7) articles did not have the intrinsic characteristics neces-sary to make them usable in the in situ contouring tech-nique. These rods are either too strong (Isola system) orvery elastic with little or poor malleability (Moss-Miamisystem / CD-horizon system). The author notes also thatin situ contouring technique should be performed withmalleable rods.

If the surgeon use a “standard rod”, the forces applied toobtain a deformation will be stronger and the displacementwill have to be exaggerated to achieve the desired contour(fig 6a), because a force superior to the Elastic Limit PointFe is required. If the surgeon use a malleable rod, the forcesand deformations required to achieve the same deformationwill be lower (fig 6b), because it is easy to go over the ElasticLimit Point fe. The detrimental over-bending effect αover isminimized and soft tissues are preserved.

F [N]El

astic

zone

α [°]

Plastic zone =

permanent deformation zone

Bre

akag

e zo

ne

Elastic limit point

Breakage limit point = strength

α final = 0

F [N]

Fe

α [°]

▲ Figure 1

▲ Figure 2

α final ≠ 0

F [N]

Fe

α [°]

▲ Figure 3

F [N]

Elas

tic zo

ne

α [°]

Plastic zone =

permanent deformation zone

Bre

akag

e zo

ne

Elastic limit point

Breakage limit point = strength

F [N]

Fe

α [°]

Fe’

α’α’

Ø reduction only (same material)

▲ Figure 5

▲ Figure 4


Conclusion and perspectives

When performing the in situ contouring manoeuver witha “standard rod”, an over bending movement will be nee-ded to obtain the final correction. Doing so, it is impos-sible to avoid strain and/or lesions to any soft tissues (e.a.:neural structures, disks, ligaments) or bony structures (e.a.:pedicle, lamina).

It could be dangerous to use a standard rod when in situcontouring technique or a combination of techniques areused by the surgeon to correct spine deformities. Our ana-lysis concurs with the Bridwell and Voor conclusions, andproposes to complete and document the use of the in situcontouring technique by duplicating the tests with anappropriate choice of materials adapted to the in situcontouring technique.

Mechanical contouring tests are in progress on severalrods in order to quantify bending forces and angles, andespecially to quantify the over bending phenomenon andits detrimental effects.

For in situ contouring technique (4, 5, 6), the proper rodmaterial choice and the diameter of the rod are essential. ■

Evaluation

References

(1) Bridwell KH :Surgical treatment of idiopathic adolescent scoliosis. Spine

1999 Vol.24 (24) pp 2607-2616.

(2) Gennari JM, Tallet JM, Hornung H, Bergoin M :The treatment of idiopathic scoliosis in adolescents : rota-

tion or in situ bending ? European Journal of Pediatric

Surgery 1997 Vol.7 pp 353-360.

(3) Jackson RP :Intrasacral fixation and in situ contoured spinal correc-

tions. Spine State Art Rev 1996, 10, 561-86.

(4) Steib JP, Averous C, Lang G : Traitement chirurgical des scolioses par deux techniques de

correction différentes. Presented at the Groupe d’étude de la

scoliose 26th Annual Meeting, March 1995, Dijon France.

(5) Steib JP : Les “nouveaux” systèmes d’instrumentation rachidienne

postérieure : l’instrumentation SCS. Cahiers d’enseignement

de la SOFCOT : instrumentation rachidienne 1995, 53, 229-

235

(6) Steib JP : Spine Contouring System in lombosacral arthrodesis. In :

Margulies JY et al, Lomboscral and spinopelvic fixation.

Lippincott-Raven Publishers ed, Piladelphia, 1996, 421-430

(7) Voor MJ, Roberts CS, Rose SM, Glassmann SD :Biomechanics of in situ rod contouring of short segment

pedicle screw instrumentation in the thoracolumbar spine.

Journal of Spinal Disorders Vol.10 (2) pp 106-116.

(8) ASTM F67 and F136/ISO 32-2 and 5832-3 forTitanium. ASTM F138/ISO 5832-1 for Stainless Steel.

▲ Figure 6a

▲ Figure 6b

F [N]

fe

α [°]αoverα final

F [N]

Fe

α [°]αoverα final

LOW ELASTIC RETURNRespect of soft tissue

Less stress on implants

Intermediate deformation neededwith a malleable rod

HIGH ELASTIC RETURNRisk of high stress on screw

combined to injury on soft tissue

Intermediate deformation neededwith a standard rod


News

Communication

A first special session devoted to dynamic spinal fixation, a mini-congress organized intoconferences, workshops, and experience-sharing meetings, was organised in Tokyo last March byDr. Kunogi and his colleagues. This first meeting was a great success. Another meeting was also orga-

nised in Buenos Aires (Argentina) at the end of September 1999 by Pr. Ayerza,Dr. Ramirez and Dr. SOLA. It focused on the dynamic spinal osteosynthesisand the in situ contouring technique in the treatment of scoliosis througha tribute to Pr. Roy Camille, with Dr. Mazel and Pr. Steib as guest speakers.

Other sessions are planned for 2000, again in Tokyo, and potentially inSpain, which would foster ARGOS’

cross-border expansion.

Dr. Kunogi Pr. Ayerza Dr. RamirezWorldwide expansion

Argos training programs

From our web site at www.argos-europe.com surgeons will be able tochoose from the various officialtraining centers and obtain indivi-dually adapted programs. Such trai-ning will focus on: medical exami-nations, analysis of case reports, realsurgical procedures, simulations ofsurgery on synthetic models, theo-retical training and personalizedassessments on CD-ROM (surgicaltechniques, biomechanics, methodsand tools for diagnosis and clinicalfollow-up). Surgeons will then begiven comprehensive training inspinal surgery.

PGT (Post-Graduate Training)

A meeting intended for GeneralPractitioners entitled “Lumbosacralpathologies and their surgical treat-ment” was held on the initiative ofDr. PETCHOT in Cergy Pontoise(France) on May 5th, 1999. Somefifteen practitioners followed thetraining program divided into threesuccessive lectures, from 8:30 to10:30 p.m. A similar meeting was

organized by Dr. HECKEL inSaint Avold (France) on October15th 1999. These Post-GraduateTraining sessions have proved to bevery efficient in informing GeneralPractitioners about the latestadvances in spinal surgery.

Argos Spine News

The next issue of our journal isscheduled for release onSeptember 30th. Any articleconcerning our association or focu-sed on research in spinal Surgery orBiomechanics would be most wel-come. ARGOS SPINE NEWS isfirst and foremost a communicationtool allowing ARGOS members toshare their views straightforwardlyon issues that they feel stronglyabout. The journal has a worldwidecirculation of over 7,000 copies,which contributes to both impro-ving internal communication andbroadening the association’s reach.

Eurospine 1999

ARGOS has a global vision and

takes an active role in various inter-national scientific events.

One of these was the EUROS-PINE congress that took place inMunich (7th-11th September1999), where ARGOS presentedsome of its Communication,Training, and Assessment activities(Internet site, Journal, Spine sur-gery, Synthetic models, Clinicaldatabase), and the outcomes of ourpartnerships (Spine View, currentresearch studies). This meetingwas another opportunity forARGOS to be present at interna-tional level and to increase itsinfluence with a large audience.

Website

ARGOS has moved onto theInternet and now is available onhttp://www.argos-europe.com.Please send any comments or sug-gestions to:

[email protected]


ABiostatistics department wasrecently founded byARGOS. The move called

for the recruitment of a PhD inBiomedical computer engineering.Mrs Ilhem Cherrak is expected toset up and develop Biostatisticsskills of ARGOS research projects.

Beside this, she will also coordi-nate and manage ARGOS’ clinicaldata collecting network. In chargeof developing the use of compute-rized evaluation tools (databases,software programs for quantitativeanalyses, developed in collabora-tion with our research partners),she will routinely synthetize thebody of clinical data available viamorbidity reports on the varioussurgical techniques covered by thecollecting network. She maymoreover be involved in variousresearch projects initiated by theBiomechanics Laboratory thatentail collecting and doing a surveyof the available clinical data.

Responsible for the integrity andconsistency of the data managed bythe association, she will also beexpected to insure that the out-comes of the research work trans-late as long as possible to the ope-rational evaluation tools ARGOS’network makes everyday use of.

With the creation of this depart-ment, ARGOS has knitted togetherthe total skills and expertise requi-red for a top-level partnership withthe clinical disciplines. As an inter-disciplinary approach, Biostatisticsshould be an exciting prospectfuture research work in SpineBiomechanics. ■ AT.

When biomechanicsinterfaces with statistics

Evaluation



The purpose of this study(which began in 1995, withthe Ph.D. Thesis of Pol

Leborgne, directed by Mrs. Skalli,and Mr. Lavaste in conjunctionwith the Saint Vincent de PaulHospital – Paris – (Pr. Duboussetand Dr. Zeller), performed in theBiomechanics Laboratory (LBM) ofthe ENSAM* Paris, in collabora-tion with the Ecole de TechnologieSupérieure de Montréal (JacquesDe Guise), the Ecole Polytechniquede Montréal (J.Dansereau, C.EAubin, Y Petit), and the Hospital

Sainte Justine de Montréal (H.Labelle, J. Joncas), was to stimulatesurgical correction of scoliosis byrod de-rotation using a personali-zed Finite Elements Model for agiven scoliotic patient in order tohelp surgeons who look forwardoptimized method (distraction andcompression, translation towards afixed rod or rotation of the rod,etc…) to optimize their operativestrategies. This workwas co-sponsored by the Frenchministry of Education & Research(MENESR), Sofamor-Danek, The“Franco-Quebecoise” Association,and The Claude BernardAssociation.

Personalized geometry was obtai-ned with a pair of Stereo X-raysusing a specific technique: 3Dreconstruction of corresponding ornon-corresponding points (anato-mic landmarks viewed only on oneof the two X-rays). Geometrical datawas used to build a 3D FiniteElements model, including rib cageand pelvis. Mechanical characte-ristics were fitted for a givenpatient using bending tests: cadaverexperimental characteristics of soft

issues were altered locally or regio-nally until the model renders thefunctional unit’s behavior. De-rota-tion surgery was simulated in4 steps: 1- Simulation of patientprone on the table with traction.2- Modeling of the rod - rigid linkswere considered between hooks orscrews and vertebrae simulatingpedicular or laminar connectionwhile taking into account slidingbetween connecting elements androd. 3- Rod insertion on the screwsor hooks. 4- Rod de-rotation arounda moving axis.

For compliance evaluation of theFE Model, the 3D per-operativelymeasured displacement of T1 ver-tebra was imposed as a boundarycondition (step 1). The 3D geome-try of the implant was measuredduring surgery (step 2). In the sameway, rod displacement was measu-red during per-operative rod “rota-tion” (step 4). Finally, vertebralbodyline and vertebral angulationwere calculated at each step andcompared to per-operative measu-rements obtained with an opto-electronic device. For mechanicalpersonalization, differences bet-

Finite elements

simulation of scoliosis

surgical treatment

3D modeling using CAT scan :

1 - acquisition of numerous slices2 - digital imaging processing3 - 3D geometry reconstruction using the

SLICE-O-MATIC software (courtesy ofLIO Montréal)

3D reconstitutionusing stereoradiography

Evaluation


1 2

3

3D reconstruction of a scoliotic spine using the SLICE-O-MATIC software

(by Champlain Landry PhD, LIO Montréal).

Stereoradiographies

Geometricalmodels

<- Pre & post-op. ->

Peroperativeboundaryconditions

Simulationresults

Peroperativemeasurements

EVALUATION

COMPARAISON

Personalized ->finite-element

model

Global

approach

COMPARISON

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OFA

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R/L

BM

ween the personalized and non-altered model reached 20 degreesfor Intervertebral mobility in axialrotation. Differences between ste-reo X-rays reconstructed vertebralbodyline and the simulated one,were less than 10 mm when mecha-nical characteristics were altered.Surgery simulation feasibility wasthen assessed. At each step, diffe-rences between per-operativemeasurements and simulation werealways less than 10 mm forvertebral bodyline (figure 2) andless than 3 degrees for vertebralorientations.

Scoliotic specific behavior canbe predicted using personali-zed mechanical characteris-tics in a Finite Elements Model.

The first validated results concer-ning surgery simulation can makeus confident about perspectives.The Finite Element analysis canhelp surgeons to determine correc-tion strategy and designers to opti-mize implants. This approach iscurrently being applied to the studyof the In Situ Contouring tech-nique, through the Ph.D. thesis ofRaphaël Dumas at the LBM-Paris,in collaboration with Pr. Jean-PaulSteib (Strasbourg – France). We canexpect that this kind of comparisontool will lead to better surgicalindications in the treatment ofscoliosis. ■ PL.

EJOST(European Journal ofOrthopadic Surgery &Traumatology)

The EJOST journal designedand managed by Pr. KEHR,ARGOS’ General Secretary ispublished by Springer Verlag. Itis the ARGOS’ official scientificcommunications tool. Initiallydelivered to a limited number ofsubscribers, EJOST now hasworldwide circulation of severalthousands. Springer Verlag alsoprovides that articles will soonbe available on databases suchas Medline.

ÉCOLE SUPÉRIEURE D’ARTS & MÉTIERS

Biomechanics laboratory151, Bd de l’hôpital 75013 Paris

Phone 33 1 44 24 63 64 - Fax 33 1 44 24 63 66

In brief


Together with his team of researchers, Pr. Jacques A.De GUISE, who is running the LIO, has got involvedin the Research and Development activities of theBBRG (Biomechanics and Biomaterials ResearchGroup) of the École Polytechnique de Montréal, theLIS3D** of the Hôpital Ste Justine, and the LIVIA***of the École de Technologie Supérieure de Montréalembarked on some years ago. The prime purpose of theresearch work carried out has consistently been todesign applications clinical professionals can takeadvantage of. But this outwardly complex networkmerely reflects how close the collaboration cliniciansand engineers are working in actually is. Teams ofresearch engineers in hospitals typify the North-American way of integrating technological and bio-mechanical research into hospital facilities and logis-tical support, a strategy that has unfortunately notgained much ground in Europe.

The creation of the LIO is set in this genuinely globalapproach. Engineering students in hospitals andmedical students getting to work in a technologicalcontext close to their own environments is the gua-rantee that both the training given to students and theresearch work conducted in the laboratory reach thehighest requirements of quality and relevance. Aboutten researchers and clinicians plus twenty universitystudents or so are currently working at the LIO.

The Montreal

Orthopedics

Introduction

The LIO was officially created in June 1997 as an extension of theResearch Center of the Montreal University Hospital Center (CR-CHUM*)

* : CR – CHUM : Centre de Recherche du Centre Hospitalier del’Université de Montréal / Research Center of the Montréal Univ. Hospital.

** : LIS3D : Laboratoire d’informatique de la scoliose en trois dimen-sions / 3D scoliosis Computing Laboratory

*** : LIVIA : Laboratoire d’Imagerie, de Vision et d’IntelligenceArtificielle / Laboratory of imaging, vision and artificial intelligence.

The LIO and ARGOS

As part of ARGOS’commitment to go global andpromote research in spinalorthopaedics, the associationis to forge links with theleading internationallaboratories in the field. Theprivileged relations betweenthe LBM and the LIO have setthe stage for a firstpartnership with ARGOS. Theydecided to go it together withthe design of a software calledSPINEVIEW for computerizedquantitative analysis of spinaldynamic and staticradiographs. Resulting fromthe confrontation of two setsof complementary skills and ofthe relentless activities ofthese two teams, theSPINEVIEW software wasgiven the thumbs-up whenfirst presented at the lastARGOS meeting.

We wish both these teamsall the glory they arerightfully bound for !

(Laboratoire de recherche enImagerie et en Orthopédie : LIO)

SPECIAL FILE :

Focus on


Professor Jacques De Guise

Activities

The LIO activities are about three thematics that fullycomplement and build on each other, namely biome-chanics/biomaterials, clinical research, and medicalimaging, run by Pr. L’Hocine YAHIA, Dr. NicolasDUVAL, an orthopaedic surgeon at the CHUM, andPr. Jacques De GUISE respectively. Such activitiesextend beyond the scope of clinical research work tocontrive to be both clinically- (degenerative jointdisease, spine and knee surgery, arthroplasty of the hip)and technically–oriented (2D and 3D processing ofmedical images, artificial vision, 3D kinematic analy-sis of the locomotive apparatus, surgical navigation, andso on…). The LIO activities are also shaped by tech-nological transfers and the pooling of skills and exper-tise in such cutting-edge fields as the analysis of carti-lage degeneration, knee ligament plasty, and functionalassessment of foot orthoses.Besides, the partnership entered into by the Québecresearch network and the French LBM run by Pr.

François LAVASTE and Wafa SKALLI (BiomechanicsLaboratory of the Paris-based ENSAM-CER) wasmainly centered on the spine, and notably the scolio-sis. Quite a number of several-month exchanges bet-ween students and researchers have already beenarranged every year for over 7 years now. Pr. JacquesDe GUISE has recently spent over 12 months conduc-ting some research work at the LBM as guest profes-sor (from June 1997 to July 1998). ■ AT.

Outlook

The LIO is expected to contribute to integrating andconsolidating the activities of researchers from a varietyof backgrounds (engineering, computer science, andmedicine) working in the field of orthopaedics. Thebody of knowledge acquired over the last few years hasopened the way for a shift of research and developmentfocus to other issues raised by joint diseases: • Automated analysis of dynamic and static radiographs• Application of non-rigid registration by 3D elasticdeformation for modeling of the joint• Biokinematic modeling of the knee using multibodydynamic simulation• Assessment of progression of degenerative jointdiseases and the effect of chondroprotective drugs by3D MR imaging• Assessment of osteoporosis and bone substitutes bybiplanar imaging• Functional evaluation of ligament surgery• Functional evaluation of hip surgery• Computer-assisted design and evaluation of pros-theses and orthoses• Computer-assisted surgical maneuver• Application of digital imaging analysis to telemedi-cine. ■

Imaging and

research Laboratory

Training

Functional evaluation of ligament surgery


Communication

To promote applied researchin orthopaedic surgery.

This is the mission of ARGOS’three partners (surgeons, biomedi-cal researchers and industrialists).The three orientations of the asso-ciation, namely Communication,Training and Evaluation, make for atop-level synergy between all threepartners. This approach, which canalready be associated with a varietyof informational benefits, inclu-ding various major events andresearch projects, is now entering a

new phase with the creation offoreign national ARGOS groups.Officially set up in 1999, theBelgium group now convenes on aregular basis. The first ArgentineanArgos national congress, which washeld in September 1999 in BuenosAires was a real success, regardingquality of scientific exchanges thatoccured around a tribute toRaymond Roy-Camille. Our japa-nese collegues, who organized thefirst Argos meeting in March 1999,were also most successful in their

way to join together top-level scien-tific contents with open-mindedand convivial ambiance. Spain, theUnited States, South Africa andGermany have all been conclusi-vely approached, which bids fair tolead, in due course, to the officialcreation of a number of nationalgroups.

Why to create ARGOS nationalgroups ?

First and foremost, a national groupis a connecting link, the interfacebetween the ARGOS Internationalnetwork and home orthopaedicsurgeons. National groups areexpected to contrive to both broa-den the reach of the Association inthe home country along the threebasic orientations aforementionedand bind ARGOS and home officialauthorities (Department of Healthand Human Services, Departmentof In-service Training and so on)together. The groups have authorityto ask surgeons to more or less for-mal seminars devised as trueforums for experiences (actualnational meetings are sometimesheld, as in Tokyo in March 1999and Buenos Aires in September1999). They are also expected tofoster the development of ARGOS’projects (Internet site, journal, cli-nical database, research, and soon…) on the national level, in fullcollaboration with the relevantcommittees.

Just like virtual communities pop-ping up everywhere on theInternet, the ARGOS Internationalnetwork is firmly geared to inte-grate its partners into a cohesivewhole along a global set of opera-ting rules that bolster information

exchanges. ARGOS is first andforemost about interconnectingpeople, with a reaffirmed commit-ment to contacts and conviviality.

How to create and operate anational group ?

The initiative and the procedurefollowed for the creation of a natio-nal group are left to the country. Inrelation with and in agreementwith ARGOS International, natio-nal groups gradually crystallizearound a few key members andARGOS’ basic commitments, lea-ding within a few months to thecreation of a national group laun-ched officially in full compliancewith national regulations, or justlaunched regarding to the Argosinternational network, which is themost important. The official laun-ching implies the defining of anorganizational structure topped bya Board of Directors, a Chairman, aGeneral Secretary, a Treasurer anda correspondent with ARGOSInternational, and a registrationfee. The unformal launching onlyneeds one or several correspon-dents with ARGOS international.Of course, in both cases, membersof the national groups have first tobe registered as members ofARGOS International.

ARGOS committees :coordinating organs of thenational groups.

Committees are meant to coordi-nate and lay down guidelines forARGOS International throughnational groups. The three com-mittees (Communication, Training,

International growth3 partners, 3 orientations, 1 goal


and Assessment) composed of pro-fessionals convene twice a year, andnotably at the InternationalMeeting in Paris. Committee mem-bers, coming from the variousnational groups, are to endorsetargets and monitor their progress.They therefore are the true drivingforce of the ARGOS network.Electronic mail makes real-timeaccess to information available tomembers sitting on the committees.An elected Chairman chairs eachcommittee. The tenure is for twoyears.

The Communication committee ismeant to increase the efficiencyand encourage the long-term deve-lopment of ARGOS’ communica-

tions structure (Internet site, jour-nal). It is also involved in organizingthe Annual International Meeting,setting up and managing nationalscientific committees that are tocompile and assess published mate-rial for national seminars.The Training committee spots, putsforward and approves of ARGOS’official training staff. It aims toupgrade training background mate-rial (synthetic models, CD-ROM,and so on…) and national seminars.In collaboration with training ser-vices, it is also meant to have trai-ning methods and sessions reco-gnized by the national authoritiesfor professional training.The Evaluation committee detects,proposes and approves ARGOS’

Recognized as a training organi-zation by the French authoritiesunder registration number31670119662, the ARGOSAssociation has been organizingtraining sessions since 1997.

Professional trainingin orthopaedic surgeryThe ARGOS Association moved todraft annual training reports twoyears ago. The reports compile thevarious training background mate-rial developed and used over theyear involved, including thearticles, the lectures produced andapproved of by ARGOS’ members,the reports of the congresses orga-nized within the framework ofARGOS together with the assess-ments of the training sessions pro-vided by ARGOS’ training centers.

Such reports fully account for themajor and efficient part played byARGOS in professional training inorthopaedic surgery.

A personalized trainingprogramARGOS international network’straining centers are now availableto anyone with access to the Net.The Web site’s database filled withuseful information, including adetailed presentation of the regis-tered training staff, their degreecourses, the registered specialistqualifications and all the variouselements connected with the placewhere they are in practice, can nowbe searched through, allowingInternauts to apply for a personali-zed training program while on line.The training programs have been

defined as several successive daysto be spent in the various centers ofthe network. They are then retur-ned by ARGOS’ Secretariat with achoice of dates along with accom-modation detailed information,once the availability of the trainingstaff has been checked. Trainingsessions get off to an early start withoperating programs, staff meetingsand consultations. Trainee surgeonsalso attend theoretical courses inthe various surgical techniques andall of their biomechanical aspects,as well as in the assessment tech-niques implemented by the center.Let us hope that this approach, lar-gely derived from the Tour deFrance carried out by journeymencompleting their apprenticeships,will come up to our expectationsand, ultimately, meet our members’needs for training ! ■ PS.

official evaluation tools. It coordi-nates the operating and the deve-lopment of the assessment tools ofARGOS’ international network (cli-nical databases, medical softwarefor the quantitative analysis ofmedical imaging, and so on…), anddevises research projects likely toimprove them. The assessmentcommittee works in close collabo-ration with the Biostatistics depart-ment (see article page 15). In colla-boration with the national groups, itis also meant to develop the use ofARGOS’ evaluation tools and ser-vices in their country. ■ AT.

Argos:International

training





For more information, see next page and get in touch with your local distributor.

Circ

le 8

on

Rea

ding

Ser

vice

Car

d

Centre Hospitalier de l’Université deMontréal

1560 Sherbrooke Est Str.Montreal (Qc)

CANADA H2L 4M1Phone (514) 281-6000 #8720

Laboratoire d’imagerie, de visionet d’intelligence artificielle (LIVIA)

École de technologie supérieure1100 Notre-dame West Str

Montreal (Qc)CANADA H3C 1K3

Phone (514) 396-8800 #7675

Biomechanics - biomaterialsresearch group

École PolytechniqueCP 6079 Succ. Centre-ville

Montreal (Quebec)CANADA H3C 3A7

Phone (514) 3940-4711 #4198

Industrial collaborations :GERMANY : Telos

CANADA : Arthrolab, BiOp,Orthomedic, Zimmer

FRANCE : Argos, Eurosurgical, CeraverUSA : Sofamor Danek,Proctor and Gamble

Funding :NSERC, FCAR, FREOM, FCI, FRSQ

University collaborations :Biomechanics laboratory

of ENSAM (Paris FRANCE)LIS3D & Hôpital St-Justine (CANADA),

University of Bochum (GERMANY)

5) 1) Arthrosis,study on total hip replacement, 2) Ligament reconstruction, 3D knee modeling, 3) Kinematic analysis, dynamic stability of the knee, functional knee evaluation,computer aided design and evaluation of prostheses and arthroses, 4) 3D cartilage evaluation, 3D spine modeling, computer assisted surgery, MRI of artificial ligaments

Medicalimaging

2D/3Ddigitalimaging

processing,3D modelisationand reconstruction,

low radiationmultiplanar imagery

Clinical studiesDiagnostics,

evaluation ofprosthesesandorthoses

Medicalimaging

2D/3Ddigitalimaging

processing,3D modelisationand reconstruction,

low radiationmultiplanar imagery

Clinical studiesDiagnostics,

evaluation ofprosthesesandorthoses

BiomechanicsStudy and modeling of

joint function, pathology,prosthetic replacement

BiomechanicsStudy and modeling of

joint function, pathology,prosthetic replacement

The Montreal Imagingand Orthopaedics

research Laboratory

Research center of CHUM Montreal Canada


Doctor Antonio Martin Benllochhas become familiar with manykinds of spinal instrumentationsduring his surgical practice(Harrington, Luque, Steffeeplates, CD, Isola, TSRH,Twinflex, SCS). His initial trai-ning with Professor ManuelLaguia (Department ofOrthopaedic Surgery HospitalClinico of Valencia - Spain) aswell with Dr. J. Luis Bas(Department of OrthopaedicSurgery Hospital La Fe ofValencia - Spain), have allowedhim to form a good idea of how aspinal fixation system should beused and what its capacities are.

You’ve been using CLARISinstrumentation for over twoyears now. What clinical indi-cations do you use it for ?

Antonio Martin Benlloch : We star-ted using CLARIS instrumentationin 1996. At the time we had beenlooking for a fixation system thatwas simple, easy to insert, stable,and which would allow patients toachieve functional recuperation asquickly as possible with the mini-mum of postoperative bracing.CLARIS instrumentation seems tobe especially adapted to degenera-tive lumbar disorders and it is thesystem that we use the most oftenfor lumbar surgeries. We have usedit for 120 operations at this leveland the constructs have been com-

pletely satisfactory. When the lum-bar curvature of a patient with sco-liosis is degenerative, we make useof one of CLARIS instrumentation’sbiggest advantages : the possibilityof combining it with SCS instru-mentation and its in situ contouringtechnique.

The biomechanical tests car-ried out at ENSAM’sBiomechanics Laboratory,indicate that in a screw-rodconstruct, the intermediarypedicle screws undergo forless stress than those at eachend. Do these observationsseem logical to you and doesyour personal clinical expe-rience support them ?

AMB : These observations aretotally in line with my own clinicalobservations. I have never seen ascrew fail at the intermediarylevels, but screws have failed at theconstructs’ extremities.

In a series of 125 cases of lumbarsurgery examined where approxi-mately 98% were carried out usingCLARIS instrumentation, we had 2cases with screws broken at S1level and I am convinced theseincidents were caused by the sur-gical technique used (only onescrew was placed at the level of thesacrum) rather than by the screwitself.

Does the adaptability providedby the plastic deformation ofthe intermediate connectorsseem to you like a definiteadvance in simplifying thesurgical maneuver ?

ENSAM’s Laboratory of Biomechanics in Paris

constructed a three-dimensional model using

finite elements in order to understand the biome-

chanical behaviour of the spine when instrumen-

ted with multiple level transpedicular fixation.

Their analysis hightlights significant differences

in the loading conditions experienced by each

vertebra.

For example, the above figure shows the maxi-

mun bending moments of transpedicular screws

in a flexion-extension load of up to 10 Nm.

Bending momentin screws

Clinical caseThe Claris instrumentation in spinal fusion :a specialist’s point of view

Dr. Antonio Martin Benlloch

Hospital “Clinico Universitario”

46010 Valencia - Spain

Training


AMB : I think that these specialconnectors do in fact improve theadaptability and the compensationfor differences in the screws’ posi-tions (fig. 1, 2, 3). Using theseconnectors means that even if thepedicles are not aligned althoughaccording to the X-rays the screwsare correctly inserted, there is noneed for concern not even at thethoracolumbar level, whether thereare fractures, tumors or degenera-tive scoliosis.

If you simply tighten the lockingconnector, the intermediateconnectors adapt efficiently to dif-ferences in angulation and depth ofthe pedicle screws. It’s this veryphenomena that distinguishesCLARIS from the other instru-mentation currently available onthe market.

What specific difficulties couldbe encountered and possibleerrors made, the first time asurgeon uses CLARIS instru-mentation ?

AMB : You must take special carethat the rod’s profile corresponds tothe shape of the sacrum. When therod is bent, there is usually no morethan 4 or 5 mm between theconnector and the bone, and thiscould make the insertion of thesecond oblique screw difficult.

You must, in addition, prevent thehardware from touching the over-lying joint so that it is not damaged.

At the end of the intervention, youshould make sure that all the loc-king nuts and the locking connec-tors are correctly tightened. Thischeck ensures excellent fixation,particularly when complementarymaneuvers of reduction andcontouring have been carried out toadjust the profile. It is important,especially in short constructs, tostop rotation using rod-holding for-ceps.

To prevent malpositioning andthe perforation of the anteriorwall of the vertebral bodyduring insertion, CLARISpedicle screws are not self-tapping. Do you think that thisprecaution providesadditional secu-rity in screwplacement ?

AMB : I preferscrews not to beself-tapping sinceit is important forme to feel the pathof the screw. I also pre-fer to make the hole in the pedicleby hand rather than with the powerdrill and I favour visual and tactileinspection over direct video-assis-tance. I rely on anatomical land-

The intermediate connector AL01

This intermediate connector pre-

sents the distinctive feature of

being adaptable to any screw posi-

tionning, while enabling firm fixa-

tion with no degradation of the

anchoring of the bone.

1

2

3

Training


marks (radiographic appearanceand the patient’s position) wheninserting the screws. It is unwise touse self-tapping screws in osteopo-rotic bone since it is very easy topenetrate the cortical layer. If youuse a screw that is not self-tapping,even if it is too long, it is impossibleto penetrate the anterior cortex, ascrew that is too long can be with-drawn and replaced by a shorterone.

In an in vitro study on screwpull out strength, ProfessorLavaste (ENSAMBiomechanics Laboratory)observed that the resistancedepends mostly on the qualityof the bone ; the influence ofthe kind of thread and thelength of the threaded portionis limited. What do you thinkabout this ?

AMB : Some authors have shownthat a depth of insertion equal to50% of the anteroposterior lengthof the vertebral body is sufficientfor optimal hold into the vertebra.

Other authors recommend the useof bicortical screws even in theintermediary part of the spine. Inmy opinion, surgeons should have agood technique for inserting thescrews and use the least dangerousmethods and instrumentation.

ENSAM recently developed afinite elements model of thespine to evaluate the stressdistribution in the CLARISpedicle screws under simpleand combined loading modali-ties of flexion-extension, tor-sion and lateral bending. Theresulting pullout stresses werelow and remained inferior tothe endurance limit determi-ned in vitro by ProfessorLavaste, except at the sacrallevel. In your clinical expe-rience, have you observedpostoperative problems rela-ted to screw pull out ?

AMB : In the series of 120 CLARIScases we didn’t observe any screwpull out. I believe that in too stiffspines excessive pull out forces canbe caused by correction. You needto take special care in the correc-tion in the sagittal plane (restora-tion of the lordosis).

At the level of the sacrum,where the bone quality is notalways excellent, fixationusing two divergent screws isrecommended to counter thehigher stresses which arecharacteristic of longconstructs. What is your pointof view on this subject ?

AMB : Screw pull out at the level ofthe sacrum is a problem whichmainly concerns elderly patientssince their bone quality ismediocre.

In my opinion, when fixation of thesacrum can only be controlledusing complicated constructs toreinforce it, it means that the pro-blem was not correctly dealt with inthe beginning.

It seems to me that by following theindications for improving thescrew’s hold at the sacrum level(inserting the screw into the sacrumnear the vertebral end-place, usingbicortical screws or two divergentscrews) would solve most problemsof sacral fixation.Blocking screws and the specialCLARIS connector appear to me tobe well suited to S2 fixation.

The Jackson technique, of insertinga rod into the sacrum, also producesvery good fixation, but the proce-dure is difficult to carry out.

CLARIS pedicle screws arecylindrical and not conical soas to avoid screw loosening



Experimental model for screw pull out

▼

Col

labo

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within the pedicle when thedepth of insertion is adjusted,and to limit pedicle breakage.Do you think that this precau-tion is appropriate ?

AMB : I have never used conicalscrews, but I would think that theycould cause two problems : thefracture of the pedicle and the lossof the screw’s hold into the pedicle.It seems preferable to me to use acylindrical screw and to opt for alarger diameter (fig. 4).

The comparison of the beha-viour in flexion of smooth-col-lared screws and screwswithout a smooth collar showsthat for the same loading pat-tern applied, the maximumstress that the smooth-colla-red screws undergo is 20 %lower than that of screws(fig. 5a & 5b) without asmooth collar ; this shouldreduce the risk of fatigue fai-lure. Does your clinical expe-rience corroborate this state-ment ?

AMB : As I have already said, sincewe have been using the CLARISsystem, we have observed very fewcases of screw breakage. It is alto-gether possible that the screw’ssmooth collar has played a role inthis. Whatever the case, one shouldremember that CD screws are alsosmooth-collared, and to my know-ledge it is for the same reasons.The in vivo loads acting on pediclescrews pertain more to bendingmoments than pull-out loads.What’s more, the triangulation pro-vided by the use of a transverse linkat the end of the construct gives thescrews better resistance to pull outthan does extending the threadedportion the entire length of thescrew.

The CLARIS connector’sadaptability means that it issandwiched between the baseof the screw and the lockingnut (fig. 6) thereby preventingthe so called instantaneousloosening that is sometimesobserved with other types ofhardware. Does your expe-rience confirm the efficiencyof this screw-connectorassembly ?

AMB : We have never observed thedisassembly of a construct causedby the loosening of the nut. This isno doubt due to the efficiency ofthe screw-connector assembly.When other instrumentation is

used, it becomes necessary to insertwedges to compensate for the dif-ference in the screw and theconnector’s angulation. This is notan easy maneuver and can some-times lead to construct disassembly.

One of the advantages of CLARISinstrumentation is that it simplifiesthe operating procedure. By simplytightening the locking nut, the cor-rect screw-connector assembly isautomatically obtained, without theaddition of complementary hard-ware.

CLARIS proposes reductionscrews (fig. 7) for the treat-ment of spondylolisthesis.What is your experience withthis kind of indication ?

AMB : When using the CLARISinstrumentation in, for examplethe case of spondylolisthesis at L5,I fix the sacrum securely (twodivergent screws), and then pro-ceed bilaterally with the progres-sive reduction, continuously chec-king the state of the L5 roots.

In all cases of spondylolisthesis, it isvital to know when to stop thereduction (a 100 % reduction is notnecessarily the best solution).When the reduction seems suffi-cient, it is important that there beno space between the connectorand the locking nut. The connec-tors are then 2 or 3 mm away fromthe pedicle screw support rim. It istherefore necessary to bend therods to bring them near to eachsupport rim and then tighten thelocking nuts to obtain an optimalscrew-connector assembly. The

5b

6

7

Training

4

Loosening of the screw

Damaging of the pedicule

5a


excess threaded section is theneasily removed by breaking thethreaded rod.

The advantage of the CLARISrod is that, like the SCS rod, itcan be contoured. Have youalready had the opportunity touse the in situ contouringtechnique with CLARIS ?

AMB : In most cases lumbar spinaldeformities are moderate, and thecorrection that can be achievedusing CLARIS instrumentation isadequate for regulating the lordosisand rectifying part of the deformity.In the case of fractures, as long asthe patient is well positioned in lor-dosis, the lordosis can be regulatedeasily by in situ contouring usingCLARIS instrumentation withgood results. If the deformity issevere, while you can use the CLA-RIS screws on the controlateralside, as I said previously, it ishowever preferable to use SCSscrews for the reduction. In severedeformities they are better adaptedto in situ contouring that the CLA-RIS instrumentation.

If you had to sum up theadvantages of this instrumen-tation, what points would youhighlight ?

AMB : After using it for over twoyears and for the treatment of 120patients, I feel that the main advan-tages of the CLARIS instrumenta-tion lie in its ease of use, since theconstructs only consist of screws,connectors and rods.

The intermediary connectors,which can adapt to the disparitiesin alignment, angulation and depthof insertion of pedicle screws, helpreduce operating time.

And finally, because the screws aremade of titanium, they are verycompatible with MRI scans.

Could you tell us about theARGOS association of whichyou are one of the foundingmembers ?

AMB : ARGOS is a European asso-ciation created in 1996 under theidea of Ch. Mazel, P. Kehr, JP.Forthomme. Its primary objectivesare training, information and eva-luation in the field of spinal patho-logies. In order to do this the asso-ciation has a structure suited toexchanges and meetings betweensurgeons, as well as the necessaryorganisation and means of commu-nication and evaluation for this spe-cialised domain.

ARGOS brings together around200 surgeons for each annualcongress on a theme which reflectscurrent issues in spinal surgery. Inparticular, the convivial atmospherepromotes the transfer of know-ledge between experienced sur-geons and those who are less expe-rienced. There are, in addition,several evaluation groups wheresurgeons can discuss and assessspecific surgical techniques.

ARGOS also organizes visits toother surgeons’ operating rooms,and encourages some scientific andclinical research projects.

In your opinion, how couldsuch a structure contribute tomastering the technicalaspects of the new CLARISinstrumentation ?

AMB : Twenty years ago the area oforthopaedics that was evolvingrapidly was hip surgery. Ten or fif-

teen years ago it was knee surgery.Today spinal surgery is a relativelynew area but one with enormouspotential ; it is on its way to beco-ming a speciality in its own right.The increasing number of surgeonsinterested in the advances coursesin spinal surgery sponsored byARGOS is the best proof of this.

Many problems arise because somesurgeons try to use a surgical tech-nique before they have totally mas-tered it. While certain skills canonly be learnt by doing somethingyourself, others can only be learntfrom another surgeon.

The advances courses offered byARGOS are, in my opinion, a goodalternative to the training visits thatsurgeons sometimes do and whichcan sometimes require severalweeks or months of absence. TheARGOS courses are particularlygood because they voluntarily limitthe number of participants and thismeans that a small group can bene-fit from higher level exchanges andhave easier access to training toolssuch as the surgery simulator.

I think that the ARGOS associationfulfils a need that spinal surgeonshave, whether they are experiencedor not, for a suitable structureenabling the exchange and compa-rison of experiences, which is opento the evolution of techniques andwhich promotes training such a sur-gery. ■

- Spine Muscles BiomechanicalModeling- The CHARPAK X-ray System- Interview : F. Lavaste- Biomechanics of In SituContouring- New trends in ComputerAssisted Orthopaedic Surgery- Focus on : The biomechanicsLaboratory (LBM) of ENSAMParis

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