LAXITY AND THE TIBIAL NEUTRAL POSITION IN CRUCIATE DEFICIENT KNEES

by

Wagner Calio Batista

A Thesis Subrnitted to the Faculty of Graduate Studies and Researçh in Partial ~llfillrnent of the Requirements for

the Degree of Master of Arts (Education)

Departrnent of Physical Education

Division of Graduate Studies and Research Faculty of Education

McGill university Montreal, Quebec.

(c) Wagner Calio Batista, March 1992

ABSTRACT

The present st.udy attempted to characte.cize laxity in

cruciate deficient knees using the Genucom System compariI~

the neutral to the resting position of the tibia. A

quadriceps active technique was compared to a passive protocol

at four knee flexi.on angles: 60, 70, 80 and 90 degrees. Eight

ACL and eight PCL injured subjects perforrned active and

passive anterior-posterior knee drawer tests. These tests

were perforrned during two sessions to verify their

reliability. Posterior and anterior laxity werc recorded for

the peL and the ACL injured subjects, respectively. Ldxity

was measured at forces of 60, 90 and 130 Newtons. A feedback

unit (Biostim 6010) was used to monitor Inuscular contraction

during application of protocols. Results revealed a

significant anterior tibial shift (p<.05) in the PCL injured

patients when cornparing active to passive tests. No

significant anterior tibial shlft occurred in the ACL injured

patients when performing the same comparison. The Genucom

produced rel iable resul ts across two sessions for both PCL and

ACL groups. Posterior laxity of PCL injured subjects was

similar for knee flexion angles between 60 and 90 degrees.

ACL injured subjects had statistically sirnilar anterior laxity

dt knee flexion angles between 60 and 90 degrees.

i

ABSTRAIT

L'étude presente a tenté de caracterizer le déplacement

du tibia des genoux avec les blessures des ligaments croissés

par l'usage du Systeme Genucom pour comparélnt III posltion

neutre i la position de repos du tibia. Une technique nctif

des muscles quadriceps était compar~ ~ un protocole passif en

flexion du genoux par quatre angles: 60, 70, 80 et 90 degrés.

Huit sujets, -rec les blessures du ligament croissé postérieur

(Lep) et huit sujets avec les blessures du Ijq~ment croiss6

antérieur (LeA) accomplirent des tests antéricur-postérieur

actif et passif du genoux. Ces tests ont été rél i t durdnt doux

sessions pour verifier leur ,... ,.

surete. Les doplaccmonts

postérieur et antérip"~ sont enreg Istré respect bernent pour

les sujets avec les blessures du LCP et du LCA. Les

déplacements sont ~

mesure en contrainte de GO, 90 ct ]]0

Newtons. Une unité de feedback (Biostim 6010) Gtllit util isé

pour contr81er de contraction musculaire durant l'nppl1catlon

des protocoles. Les résultats révélèrent une dév iat ion

antérieur significative du tibia (p<. 05) dans les patj ents

.. . avec les blessures du LCP apres comparaIson entre les tests

actifs et passifs. Aucune déviation antérieur ùu tibia

n'apparaissait dans les sujets avec les b]e~jSllrO;; du LCA

lorsque la même comparaison a été accomp 1 i r. J J(' Genucom

produisait des résultats sûr aux travers deux seSSlons pour

les patients avec les blessures du LCP et du LCA. Le

ii

déplacement postérieur du sujets avec les blessures du LCP

était similaire pour le genoux plié aux angles entre 60 et 90

degrés. T,'" ~ suj ets avec les blessures du LCA avait

déplacement antérieur statistiquement similaire aux genoux

plié entre 60 et 90 degrés.

iii

• ACKNOWLEDGEMENTS

This thesis was made possible w i th the dSS i st'::l I1L'e o!

individuals and organizations. 1 dm deeply thi1nktu1 to:

My parents, Wi Ison and Margaridd who supportcd ml' doc i~, Ion

to pursue graduate school and bolsteréd my reso l vc to comp 1 ct 0

the task with love, encouragement and undcrstanJing.

Dr. victor Matsudo from the CELAFISCS orqùn i Zélt i on \Vho

ignited and fed the "s cientific flame" in my pcn~un.llitl',

CNPq, a researchcouncil in Brélzil that providod filli1nt-i.l1

help to this project.

Dr. Thomas Blaine Hoshizaki who gavE' the initictl input fo/-

this thesis and allowed the use of the Laborcltory 01

Biomec..hanics in the Department of Phys iCd l Educa t i orl dt Mc 'C i 1 1

University for data collection.

Mr. Tony Fiorentino, t'rom Medlcu~; "Jho rrovid .. d tlll'

feedback unit Biostim GOlO and referred subjccts ta tlle I,!I).

Dr. Eric Lenczner for his clinical input (lnd con!:.;t,lnt

referral of subjects to the labo

The subjects of this study for their cooperation.

Dr. Dan Marisi, ". .. Dr. Helene Perraul t, Mrs. Sonya l1d t tho',;:;,

Mr. Vassilis Vardaxis, Mrs. Lorri:dnc Coi fin, flJr. ~~t_éph,lIi('

Perrault, Mlle. Danny V~zina (lnd professors and staff in th0

Department of Physical Education whosc comments

contribution to a stimulating atmosphere helped in thp

developrnent of this project.

iv

1 Dr. Greg Reid,

Education who acted

chairman in the Department of Physical

as co-s'lpervisor of this thes is and

provided valuable input.

Ron Turchyniak and Torn Gilmour for their constant

ass istance and commi tment to friendship that enabled me to

survive through difficult tirnes.

Finally, l wish ta extend the greatest appreciation ta Dr.

David L. Montgomery and his wife, Carol Montgomery who

somctimcs acted as a family to me. His patience, enthusiastic

gujdance and encouragement provided me with the attit'.des

necesnary to complete this e~deavour.

Ta aIl of you, "Muito obrigado !"

v

TABLE OF CONTENTS

l\HJf'

LIST OF TABLES.. • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 >:

LIST OF FIGURES .•.................................

CHAPTER l - Introduction

1.1 Nature and Scope of the Problcm ................. .

1.2 Rationale for the Study......... . . . . . . . . . . . . . . . . . .1

1.3 statement of the Problem......... . . . . . . . . . . . . . . . . 'l

1.4 Dependent Var iablc's. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . l)

1.5 Independent Var iablE's. . . . . . . . . . . . . . . . . . . . . . . . . . . . (,

1.6 Research Hypothe;ws.............................. (,

1.7 Limitations ..................................... .

1.8 Delimitations ................................... .

1.9 Abbreviations and Operational Definitions ....... .

CHAPTER II - Review of the Literature

2.1 Introduct i on .................... . ..................

'(

" "

1 1

2.2 Anatomy of the Cruciate Ligaments. . .. . . . . . . . . . . .. 1 1

2.3 Kl.nematics of the Cruciate Ligamcnt~, ............ .

2.4 Biomechanies of the ACL Def iciency. . . . . . . . . . . . . .. 1 f,

2.5 Biornechan ies of the PCL Def ieicncy.. .. . .. .. . . .... l')

2.6 The Tibial Neutral Position in the

Sagittal Plane •.................................. ?IJ

2.7 lnstrumented Assessment of Kncc Motion ........... ~4

2.8 The Genueom System ............................. " ;n:

vi

CHAPTER III - Methods and Procedures

3.1 Introduction...................................... 34

3.2 Subject Selection and Treatment .................. 34

3.3 Testing Instruments and Protocols ................ 35

3.3.1 The Genucom System ..........•............. 35

3.3.2 rfhe Biost.im 6010 .......................... 40

3.4 rrreatment of Data ................................ 42

3.~ statistical Analysis ............................. 42

CHAPTER IV - Results

4.1 Introduction..................................... 44

4.2 Characteristics of the Subjects .................. 44

4.3 Descriptive Data and ANOVA Results ............... 47

ClfAPTER V - Discussion of the Results

5. ] Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 64

~.2 Type of Test and Laxity

in Cruciate Deficient Knees ...................... 65

5.2. l PCL Injured Patients ...................... 66

5.2.2 ACL Injured Patients ...................... 68

5.3 Flexion Angle and Laxity

in Crl.lciate Deficient Knees ...................... 69

5.3.1 PCL Injured Subjects .........•............ 69

5.3.2 ACL Injured Subjects ...•.•..••......•..... 70

5.4 Reproducibility of Sessions on the Genucom ....... 72

5.5 Levels of Force and Tibial Displacement .......... 74

vii

CHAPTER VI - Summary, Conclusions and Recommendations

6. 1 Surnmary ............................. ., . .,., . ., fi ., • ., ., .,., ~J 1

6.2 Conclusions ...................................... no

6. 3 Recommenda t ions. • • • . . • • . • . • . • . . . . . • . . . . . . . . . . . . .. n.)

BIBLIOGRAPHY. • • • • • • • . • . . • • . . . . • . . . • . . . . . . . . . . . . . . . . . . . . .. il \

APPENDIX 1 - Informed Consent Form........ . . . . . . . . . . . . . .. q 1

APPENDIX 2 - Subject Information Form .•...••............. '1.'

viii

LIST OF TABLES

Table Page

1 Experimental Des-,ign ................................ 43

2 Physica1 Character istics of the PCL Subj ects •.••••• 45

3 Physical Character istics of the ACL Subjects •••.••• 45

4 Medical Information for the peL Subj ects ..••.•••••• 46

,-:J Ned ical Information for the ACL Subj ects ...•....••. 46

G Mean PLAX at 60 Newtons for the PCL Suhjeets ••..••. 50

'1 AtlOVA Resul ts at 60 Newtons for the PCL Subj eets ••. 51

8 MOLIn PLAX at 90 Newtons for the PCL Subjeets ....••• 52

9 ANOVA Resul ts at 90 Newtons for the PCL Subj ects ••• 53

10 Mean PLAX at 130 Newtons for the PCL Subj eets ...••• 54

11 ANOVA Results at 130 Newtons for the PCL Subj ects •• 55

12 Mean l\.LAX at 60 Newtons for the ACL Subjeets •.•.••• 56

13 ANOVA Resul ts at 60 Newtons for the ACL Subj eets ••• 57

]4 l-1ean ALAX at 90 Newtons for the ACL Subjeets •..•••• 58

15 ANùVA Resul ts at 90 Newtons for the ACL Subj eets ••• 59

16 Mean ALAX at 130 Newtons for the ACL Subjeets .••••• 60

17 ANOVA Results at 130 Newtons for the ACL Subj eets •• 61

ix

=

LI ST OF FIGURES

Figure l'.lqO

1 Knee Flexion and ALAX for the ACL Subj ccts. . . • . . . .. (,,)

2 Knee Flexion and PLAX [or the PCL Subj ccb-:,. . . . . . . .. h l

x

J CHAPTER l

Introduction

1

The physical examination of the knee joint can be

described as a combination of art and science (Feagin, 1988).

Although manual clinical examination is considered subjective,

health specialists still rely on it to assess knee joint

integrit}.

The major limitation of classifying knee instabilities due

to soft tissue injury is the lack of an instrumented

evaluation system which validates clinical observations

(Daniel and stone, 1988). This discordance is many times

attributed to different results between instrumented and

proprioceptive assessments of knee motjon. Many factors must

be considered when comparing results on knee laxity: joi t

starting position, applied force (amount of load, rate, point

and direction of application), constraints to motion (imposed

by limb supports, force applicators, and motion sensors), soft

tissue restraints and deformation, bone contours and muscle

activity.

No investigations have used the Genucom system to examine

tibial displacement relative to the starting position of the

tibia in the sagittal plane during anterior-posterior

élssessment of the knee. This experiment examines these

aspects during a muscular active test of the knee using the

Genucom in subjects with cruciate ligament disruptions.

2

1.1 Nature and Scope of the Problem

Recently, Anderson and Lipscomb (1989) statcd that mdnlldl

qualitative examination performed by an experienced examiner

is the most accurate way to identify ligamentolls integrity.

However, they also pointed out that inslrumented kncc

examination can help develop a diagnosis and lmprove thE'

physician' s confidence by providing obj ecti ve measu rCl11ent.s

regarding joint instability.

During the past twenty years, the search [or objoctivity

has lead to the description of severa 1 protocols to i1sses~, t:l1('

displacement of the knee joint. Y.ennedy and Fow]er (197l)

first described a clinical evaluation apparatus [or in vivo

assessment of anterior and varus-valgus laxity of the knoc.

since then, a number of methods have cmcrged: anter i or­

posterior laxity testing instruments with mechanical sensing

systems (Markolf et al., 1978: Shino et al., 1984; Daniel ct

al., 1985), radiogrùphic stress techniques (Jacobsen, 1')7(;;

Torzilli et al., 1981) and dynamic three-dimcnsionnl motion

analysis (Shiavi et al., 1987: Marans ct al., 1989). Four

commercial devices have also been designed ta a~~se~;~; ]':neC'

joint stabili ty: the Genucom Knee Analysis System (0] i ver and

Raab, 1984), the MEDmetric Arthrometer models KT-lOOO and KT-

2000 (Daniel et al., 1985), the Stryker Knee Laxity Tester

(Steiner et al., 1986), and the Acufex Knee Signature System

(Riederman and Wroble, 1991).

The validity and reliability ot these :.nee cvaluation

3

devices have been demonstrated. In 1986, Brien et al.

compared five knee laxity testing procedures for cruciate

ligament insufficiency: clinical evaluation, x-ray, Genucom,

KT-1000 and Stryker. No differences were observed when normal

and anterior cruciate deficient populations were compared

using five measurement procedures. Significant differences

were not obtained between mean scores calculated from two

subsequent days using the Genucom, KT-1000 and Stryker. In

1991, Riederman and Wroble found that the error of anterior­

posterior translation measured at +/- 20 pounds for the Knee

signature System was si gnificantly greater than the error

found for the KT-lOOO, but less than the one encountered for

the Genucom.

In spite of high repeatability and validity, knee joint

evaluation systems are basically used for research purposes.

To increase their use in clinical settings, it is imperative

to obtain similar information to a proprioceptive assessment.

It is also crucial to improve the reliability of the equipment

by controlling spurious variation observed during instrumented

examination. During anterior-posterior assessment of the

knee, this variation may result from: (1) the test starting

position of the tibia in the sagittal plane, (2) quadriceps

muscle contraction (presence or absence) and (3) angle of

flexion of the knee joint.

It is important to establ ish the test starting position of

the joint if an accurate evaluation is desired. For instance,

when the posterior cruciate ligament is injured, the tibi~

subluxates posteriorly. If an anterior-posterior test l' co ~,

performed starting from the posterior subl uXùt0d ro~~t i nq

posi tion, increased anter ior and decreased poste t" i or knoo

laxity will be observed (Daniel et al., 1988). 1 t i s wC' l L

known that the posterior cruciate ligament i5 positjoned to

remain isome~rically under tension throughout the whole rango

of knee movement, thereby preventing posterior subluxùtion 01

the tibia in relation to the femur (Welsh, 1980). Allothc l'

example can be found wi th the knee joint pos i t i once! in 30

degrees of flexion. At this position, the patelJar LIgament

is oriented anteriorly as it passes from the tibial tubercle

to the patella. A slight contraction of the quadriceps C,lUf':;C':;

anterior subluxation of the tibia. TherC'fore, an antorior

laxity measurement done from an anted or1 y sublln:atC'ù st,'lt·t i nq

position will decrease anterior laxi ty. Il thore L' •• d an

anterior cruciate ligament in jury , this may not be rcvetlled.

1.2 Rationale for the Study

There were two reasons for this inve~tigation:

1. To establish the feasibility of using the Genucorn

System to determine knee laxity with the tibia in the neutral

position (sagittal plane). This was examined using a modifÎed

quadriceps contraction technique based on recommendations by

Daniel et al. (1988).

1

r

.5

2. To quantify diagnostic criteria when using the Genucom

to assess anterior-posterior motion of the knee j oint in

patients with cruciate ligament deficiencies.

1.3 statement of the Problem

This study investigated tibial displacement values in

patients sustaining cruciate ligament injured knees with the

tibia in two test starting positions in the sagittal plane:

(1) a neutral and (2) a resting position. These positions

were accomplished with the quadriceps action (active type of

test - neutral position) and without the presence of the

quadriceps muscles (passive type of test - resting position) •

Tests were performed at 60, 70, 80 and 90 degrees of knee

flexion and subjects were submitted to two separate testing

sessions.

1.4 Dependent Varjables

The following dependent variables were measured:

1. Anterior laxity values with force application of 60,

90, and 130 Newtons during anterior knee drawer tests on ACL

injured subjects.

2. posterior laxity values with force application of 60,

90, and 130 Newtons ~uring posterior knee drawer tests on PCL

injured subjects.

1.5 Independent Variables

The independent variables of this study were:

1. Types of anterior-posterior knee tests with the presence

or absence of quadriceps contraction. Two leveis waro

identified: active (with quadriceps contraction) and p~ssive

(without quadriceps contraction).

2. Testing sessions when subjects were tested: l nnd 2.

3. Knee flexion angles: 60, 70, 80, and <)0 de><]roo:;.

1.6 Research Hypotheses

The research hypotheses forrnulated for this expcriment

were:

1. posterior knee laxi ty of PCL inj ured subj eets w i Il I;e>

similar during active and passive tests at 60, 90 and ] '30

Newtons.

2. Anterior knee laxi ty of ACL inj ured subj eets w il] hl'

similar during active and passive tests at GO, ~o dnd J JO

Newtons.

3. The posterior knee laxity of PCL injured subjcets will b0

similar during sessions 1 and 2 at 60, 90 and 130 Newtons.

l 7

4. Anterior knee laxity of ACL injured subjects will be

similar during sessions 1 and 2 at 60, 90 and 130 Newtons.

5. Posterior knee laxity of PCL injured subjects will be

similar for knee flexion angles of 60, 70, 80 and 90 degrees

at 60, 90 and 130 Newtons.

6. Anterior knee laxity of ACL injured subjects will be

similar for knee flexion angles of 60, 70, 80 and 90 degrees

at 60, 90 and 130 Newtons.

1.7 Limitations

The limitations of this study were:

1. The first limitation of this study was the possibility

that the subjects might have suffered knee injuries other than

cruciate ligament disruptions.

2. The rate of force application was not controlled, since

the Genucom did not provide this information and the forces

were applied manually. This could have affected energy

absorption by ligaments and other secondary restraints.

3. Skin electrode!::, attached to a feedback unit, the

Biostim 6010 (Mazet Electronique, Inc., France), were utilized

to assess muscular activity during the Genucom evaluation.

1.8 Delimitations

This study was conducted under the f0110\,,1ng

delimitations:

1. This study ineluded subj eets wi th crue iatc l i (Jdll1C'nt

injuries.

2. Ligament injuries oecured at least thrce wccks and cl

maximum of twenty four 1l10nths prior to assessmcnt. fn ilcuto

injuries (less than three weeks), excessive swclling tlnd pdin

may cause muscular defense, making assessmcnt morc ù il l i cul t.

Excessively chronic injuries (after twcnty ! our montl1~;)

increase the probability of stretching sccondary rcstrilints.

3. To reduce age variance, subjeets were between 10 ilnù JI

years of age.

1.9 Abbreviations and operational DefinitjoQ~

The following abbreviations and opcrational dpf in i t ion!;

were adopted in this study:

1. AP: anterior-posterior.

2. ALAX: Anterior laxity.

3. PLAX: posterior Laxity.

1 9

4. PCL (posterior cruciate ligament): It is a continuum

of fibbers, more vertically oriented, thicker and stronger

than the ACL. It functions as a primary restraint to

posterior tibial displacement (Grood et al., 1988)

5. PCL deficien~:

for the invol ved leg

A difference in tibial displacement

compared to the intact leg of 2.5

millimetrcs or greater when assessed on the Genucom system at

90 degrees of knee flexion measured with a force of 90 Newtons

(Anderson and Lipscomb, 1989). Subjects had been examined by

experienced orthopaedic surgeons before testing.

6. ACL (anterior cruciate ligament): anatomically formed

by two bands, anteromedial (AMB) and posterolateral (PLB),

named according to their insertion in the tibia. The ACL has

multiple fibbers and is oriented in an helicoid manner. Its

main function is to limit anterior glide of the tibia on the

femur (King et al., 1986).

7. ACL deficiency: A difference in tibial displacement

for the invol ved leg compared to the intact leg of three

millimetres or greater when assessed on the Genucom system at

60 degrees of knee flexion measured with a force of 90 Newtons

(Anderson and Lipscomb, 1989). Subjects had been examined by

experienced orthopaedic surgeons before testing.

1 (l

8. Neutral position: The neutral position \\''-t~~ ('!:;tdblit;hl'd

when the tibia was nei ther forward nor backwd I"d in re 1,1 t ion t 0

the fernur (Daniel et al., 1988). It WilS achicved throllCJh ,1

quadriceps contraction during application of ilctive tests.

9 . Passive test: type of eval uation i Il \",11 i ch the> pdt i '-'nt

was instructed te cornpletely relax the musculature heJpe~ l)y

the evaluator' s instructions and the feedback un i t. The t i b i"

was rnoved from its resting position under the action 01 m,1l111d 1

forces applied by the examiner.

10. Active test: type of evaluatlon J n 1:/h j ch the pdt i ('nt

is instructed to perform a musc] c contr,lct ion. 1 J1 t Il 1 !;

investigation, a quadriceps contracti on tcchn iqllC~ (Dan i c> J nt

al.; 1988) was ernployed. Anter ior-poster ior manutll i orTe>~;

were appl ied to the tibia a fter the patient pl accù the ] f'CJ il t

a specifie angle of flexion.

Il. Laxity: The amount of tibial displaccmcnt uron th0

application of a force. In this study, the levcls of force

were 60, 90, and 130 Newtons. Laxity was calculated as the

difference in tibial displacernent between the involved dnd the

intact leg.

1

11

CHAPTER II

Review of the Literature

2.1 Introduction

It is recogni2.ed that the knee is the largest and most

intricate of human joints, presenting an extremely complex

biomechanical system with many peculiarities of design (Dye,

1988). Consictering that this study concentrated on the test

starting position of the tibia in the saqittal plane and its

influences on knee laxity of cruciate injured subjects, this

chapter reviews t.he relevant concepts regarding the joint

functian and the cruciate ligaments (ACL and PCL).

" .~

2.2 Anatomy of the Cruciate Ligaments

Embryologically, the cruciate ligaments are cornpletely

forrned by 20 weeks of development. From this point, there i5

marked change in their growth wi th li ttle change in shape

(Gardner and O'Rahilly, 1968). They are bands of dense

connective tissu.e, l inking the fernur and the tibia 1 and

located intraarticularly and extrasinovialy. The PCL is

longer (Girgis et al., 1975) and significantly stronger than

the ACL (Kennedy et al., 1976).

On the femuT, the ACL attaches ta the posterior aspect of

the lateral condyle and the PCL to the posterior aspect of the

medial condylf~. On the tibia, the ACL is attached to the

intercondylar erninence. This tibial attachment is wider and

1 .)

stranger than its femaral attachment (Arnoczky, 1983). The

peL attaches ta the tibia paR~eriorly to the tibial articular

surface (Clancy et al., 1983). The ACL and the PCL cross c,1ch

other, considerinq their trajectory from tllC fcmur ta the

tibia (Tortora, 1989).

'l'he ACL has an helicoidal shape. It attilches ta the felllur

and the tibia as two different functional fase icl e~,: the

anteromedial band (AMB) and the posteralateral b,1nd (PI.l\) . '1'111'

AMB originates at the feTOur and inserts dt thc ë1nterom(.~d l ,11

part of the tibial attachment.

posterolateral sect ion af the tibia l a ttdchment ( l 'u 1111,111 c'l

al., 1976). The PCL is also divided into an élntcrlor dnd d

posterior segment (Girgis et al., 197~).

Flexion and extension of the knee change the l enqth ,1llCl

tautness of the cruciate ligaments (G irg i s et al. (] () 7'). 'j'hr>

authors explain that, regarding the ACL, therc i fj 1 onqt 111'11 j nq

of the AMB and shortening of the PLB of the 1 1 \jrll11C' nt in Ln p (,

flexion. Regarding the PCL, most of the l igélmcnt i~; Llllt 1 Il

flexion, while a small posterior band of f ibbcr:..:; 1)(" 'OInO!,

100se. This happens because in this pos i t ion thprc.' J ,' .,

lenqthening of the bulk of the ligament and shorten i nf] 0 f i t!~

small section.

The cruciate ligaments are made up of multiple f<t~;C'lC'J('!"

the basic unit of which is collagen (Danylchulk et al., 1(Jï8).

The ligaments attach to the fernur and tibia vi~ the

interdigitation of their rollagen fibers with those of the

1 adjacent bone (Cooper and Misol, 1970).

13

The sudden change

from flexible ligamentous tissue ta rigid bone is mediated by

a transitional zone of fibrocartilage and mineralized

f ibrocartilage (Akeson et al., 1984). This al teration in

microstructure from 1 igament to bone a llows for graduated

changes in stiffness and prevents stress concentration at the

attachment site (Noyes et al., 1974). Arnoczky and Warren

(1988) pointed out that this transitional zone may impose a

barrier to endosteal vessels entering the ligaments at their

attachment sites.

Regarding their vascular anatomy, the cruciate ligaments

are covered by a synov ial fold that originates from the

intercondylar notch. This fold extends to the anterior tibial

insertion of the ligament, where it joins the synovial tissue

of the joint capsule distal to the infrapatellar fat pad.

This synovial membrane forms an envelope about the ligament

and presents many vessels that originate from the ligamentous

branches of the middle genicular artery. Few smaller terminal

branches of the lateral and medial inferior genicular arteries

contd bute to thi s synovial circulation (Marshall et al.,

1979; and Arnoczky, 1983).

The cruciate ligaments receive nerve fibbers from branches

of the posterior articular branch of the posterior tibial

nerve (Kennedy et al., 1982). Golgi-like tension receptors

have been identified near the origins of the ligaments as weIl

as at their surfaces beneath the synovial membrane. Schultz

1

et al.

1 .1

(1984) suggested that these mechanoroceptors m~y

provide sorne type of proprioceptive functlon and an ~tt0rcnt

arc for postural changes of the knee through de forlllilti0n!3

within the ligament.

2.3 Kinematics of the Cruciate Ligameo.b;

The cruciate ligaments are the two major intxa-drticI11,t1·

ligaments of the knee (Fisher and Ferkel, 1988). 'l'he ACL h,,~;

been reported to be approximately 38 mm in length and Il mm in

width (Girgis et al., 1975). Its averùge str0ngth h,lS bepn

determined to be 1730 N in young indivlduùls (Butler- C't ,11.,

1980). The average length and width ot the PCL h,1V0 !K'l'n

measured as approximately 38 mm and 13 mm, rcspcr:tivcly

(Girgis et al., 1975).

The importance of the cruciate ligaments for C'ontt'o11 inf)

tibio-femoral motion is essential. Mu] ] er (1981) oxp 1,1 i n"

that the basic mechanism of movement bctw0cn the t i b i ,1 dnd

femur is a combination of rolling and glidinq.

movernents are necessary since the di stance bctvJ(~on ser i dl

contact points between the tibia and the femur i5 grcater on

the femur than on the tibia. As initial and tormin~l

rotations are superimposed on the flexion and extension

movements, it becemes difficult te discern the mix of roI Jjng

and gliding in the individual phases of rnovcmcnt. Tho ;wthclr

proposes ta reduce the problem to the sùg i tta l pldnrJ ta

understand how the femoral condyle raIls ùnd glidcs on the

,-

, "

15

tibia. He points out that the ratio of rolling to gliding

does not remain constant through aIl degrees of flexion

(approximately 1:2 in early flexion and 1:4 by the end of the

movement) .

Muller (1983) also represents the principles of motion of

the knee joint by the crossed four-bar linkage. This

principle can be demonstrated by constructing an apparatus

consisting of a sheet of drawing paper on which two rods Rre

hinged at one end which intersect the longitudinal axis at a

40 degrees angle through one of the points. One of the

crossed rods is longer than the other. Their length ratio is

equal to that of the normal anterior and posterior cruciate

ligaments. The free ends of the lods are linked by a movable

rectangular plastic bar which represents the tibial plateau.

This bar forms the coupler as it is moved through several

positions to generate tangents which delineate a curve. This

curve resembles the contour of a sagittal section through the

posterior half of the femoral condyle (Muller, 1988). The

crossed four-bar linkage model can demonstrate the obligatory

shift of the tibio-femoral contact points during articular

motion. It is valid for motions in a single plane without

allowancc for rotation. With the tibial plateau fixed

horizontally, the intrinsic backward shift of the contact

point on the coupler becomes more cov~~us.

The concept of prjmary and secondary restraints is very

important for the study of the kinematics of the cruciate

1

T

ligaments.

16

According ta Daniel and stone (1988), for 11

speci fic motion, the structure tha t prov ides the 9 rc,ltC'st

limitation is eonsidered the primary restraint. \\lhon ,1

primary restraint is disrupted, motion in that plnno i s

limi ted by the remaining structures, the sec.ondary restril i nts.

The authors also add that dJsruption of a seeondary restr~int

will not result in pathologie motion if the primary rC'strl1int

is intact. On the other hand, sectioning a sC'condl1ry

restraint when the primary restraint is ruptured will enhl1ncc

pathologie motion.

2.4 Biomeehanics of the ACL Deficieney

The ACL i5 the primary anterior stabilizer in the knC'c,

eontributing 86 percent or the resistance to anterior

displaeement forces (Butler et al., 1980). The remaining 14

percent is provided by the secondary restraints. These

restraints are the MCL, the retinaeulum and the postE' l-"jr

capsule (Rovere and Adair, 1983). In addition ta that, the

ACL contributes ta stabilization against varus/va 19m;

displaeement and against anterolateral tibia 1 rota t i on

(Gollehon et al., 1987).

The ACL is the most frequently torn ligdffient within thn

knee. Although isolated ACL injuries do occur, they arc

frequently associated wi th meniscal tears (Kennedy ct ,11. 1

1974). Tortora (1989) explained that the ACL is stretch cd or

torn in 70 percent of aIl serious knee inj ur j cs. The

17

mechanisms of injury to the ACL can be classified into three

major categories: 1) forced hyperextensioni 2) forced flexion

and internaI rotation of the tibia on the femur: and 3)

forced hyperflexion of the knee (King et al., 1986).

According ta Sherman et al. (1987), the anteri or laxi ty of

an uninjured knee in 30 degrees of flexion is approximately 5

mm. A difference equal ta 2 mm or less between the twa sides

was found in 95 percent of individuals without knee injuries

in their study. On the other hand, wi th isolated ACL

deficiency, mean anterior instabili ty was 10 mm wi th an

injured versus normal knee difference averaging 5 mm.

The first step for diagnosing an ACL tear involves the

history of in jury. Important elements include the mechanism

of jnjury, measurable swelling, and a haemarthrosis within

twelve hours after in jury (Feagin, 1988). 'rhe second step to

diagnose ACL disruptions is the use of clinical tests. One

traditional test to assess ACL integrity is the anterior

drawer at 90 degrees. However 1 in this position of knee

flexion, the postero-Iateral band (PLB) is not taut and

therefore is not tested, as it was pointed out by King et al.

(1986) when explaining that the PLB can be better assessed

with the knee in extension.

Torg et al. (1976) pointed out sorne factors that may cause

a false negati ve anterior dravler test. Joint effus ion poses

di fficul ties to a proper test because of increased tension

inside the knee, protective hamstring spasm, and possible

18

impingement of the medial fernoral condyle on the posterior

aspect of the medial meniscus. In addition, if the mcniscus

is injured, forward tibial transldtion might be blockcd.

Another test to measure the anterior tibial displaccment

is the Lachman test, with the knee at 30 degrees of flexion.

At this angle, the ACL provides almost 90 percent of the tot.al

restraining force (Butler et al., 1980). 'rhe test i5 accurato

in both acute and chronic ACL tears and th is <lccuracy .:i mrrove~;

significantly with ùnaesthesia (Torg et al., 1976).

Rosenberg and Rasmussen (1984) compared the lachmnn test

and the classical anterior drawer t~st at 90 dcgrccs j n

exarnining 20 subjects with intact knees. While pcrforminq

arthroscopy wi th a special probe, they measurcd tcns j on j n the>

ACL during the two tests. 'l'he Lachman te8: W<lS a better

indicator of ACL integrity, as maximal tension did not develop

in the ACL during the anterior drawer assessment at 90

degrees. Tensions were significantly higher duri nq the

Lachman test. The authors explained that at 90 dcgrccs, the

contact between the acutely convex posterior fcmor,11 condyle

acts as a roller and the tibial articular surfaces 'vI i th j ntact

menisci act as a trough. Therefore, any forward mov0mcnt thclt

occurs will involve vertical deflection of the tibia.

However, at 30 degrees, forward tibial displacement oceurs

with le~s vertical deflection due ta more anteriorly locatcd

contact points between the tibia and the femur and the

relatively fIat distal femoral condyles.

19

Iversen and coworkers (1989) explained that the act of

performing an anterior test at 30 degrees decreases the

counteraction of the hamstrings to a forward shift due ta

muscle biomechanics. At 90 degrees, the flexors of the knee

counteract an applied anterior force. At this position, there

is a contact force perpendicular to the tibial plateau due ta

the force applied by the knee extensors, and a component that

opposes a forward applied force (due to the pull of the

hamstrings) . At 30 degrees, the knee flexors and the

hamstrings act paraI leI to the axis of the tibia producing

onl y one ma in resul tant, a tibio-femoral contact force. Since

the friction coefficient in human joints is considered to be

negligible, the opposing effect to any forward displacement

during application of an anterior force is minimal at 30

degrees of knee flexion (Lachman test).

2.5 8iomechanics of the peL Deficlency

The PCL contributes 95 percent of the knee's stability to

posterior tibial translation when flexed to 90 degrees (Butler

et al., 1980). It also contributes to knee stability against

varus-valgus rotation and posterolateral tibial translation

(Gollehon et al., 1981), but only as a secondary restrainer,

because isolated removal of the PCL causes no change in the

limi ts of tibial or varus-valgus rotation (Grood et al.,

1988) .

Reported injury rates range from 3.4 to 20 percent of aIl

• 1

l

20

ligament injuries in two series described by o'Donoghue (1959)

and Clendenin (1980) respectively. rrhere ha"e bcen threC"

major mechanisms of injury described for PCL disruption~.3: l)

hyperextension of the knee: 2) hyper flcx 1 on of the knec: ,llld

3} posterior tibial displacernent with the knee in flex! on (Van

Dommelen and Fowler, 1989).

In a study by Girgis et al. (1975), a PCL dj sruption

resul ted in a signi ficant posterior drawer in fle>.: i on (<J. r.

mm) . In 1988, Grood and associates studied the e r f cct 0 f

cutting the peL and posterolateral structures of the kn0ü.

The highest value for posterior tibial translation was Il.4 mm

at 90 degrees (twice as large as at 30 degrccs) showing th,lt

the posterior drawer should be more sensitive when done nt 90

degrees. The authors explained that this WilS the ro~ult al

the slackening of the posterior port ion of the capsul C', mec! LII

and lateral extraarticular structures that act as second~ry

restraints to block posterior translation of the tibia.

2.6 The Tibial Neutral Position in the Sa~ittal PlqDQ

The neutral position of the knee joint, especially in the

sagittal plane, has been a main cancern of severc11

researchers. Butler and associates (1980) det ined the noutra J

point along displacement-force graphs v/hen doser Ipt ive

parameters of energy absorbed by th,< knee were at thel r

minimum values.

In eruciate ligament injuries, the test starting point and

1 21

whether the joint cornes back to its previous position between

each test is not weIl defined. Muller (1988) explained that

in combined instabili ties, detection of the neutral point

between anter ior and posterior displacements is extremely

difficul t. He suggested that a possible solution to overcome

this problem is offered by stress radiographie techniques.

This had already been attempted by Torzilli et al. (1981).

using X-ray procedures, the authors found no differences in

anterior-posterior motions for uninjured knees in patient.s

with ACL tears and normal control subjects. Symmetry between

the amount of anterior and posterior translation was measured

from the neutral position. This position was defined as the

point from which the tibia was neither located backward nor

forward in relation to the femur (the "unloaded" position).

The authors demonstrated that a posterior sag was unlikely ta

occur in intact knees. Their findings implied that

comparisons between contralateral knees and absolute

comparisons among injured and normal subjects are perfectly

possible.

Staubli and Jakob (1990) explained that posterior tibial

subluxation tests and posterior tibial position on

stressradiography help ta differentiate PCL from ACL injuries.

They determined the diagnostic value of clinical tests

designed te rneasure posterior tibial subluxation in patients

with acute PCL disruptions. 20 patients with intact ACLs were

aIse evaluated. After evaluatjng the intact knee of the PCL

') ') L (

patients, the gravi ty test near extension ùnd active reduct ion

of posterior tibial subluxation were performed wi thout

anaesthesia. Under peridural anaesthesia, the p~tiants wcro

submitted te the following tests: posterior tibidl

subluxation, reduction of posterior '.::.ibial subluxi1t ion,

external rotation recurvatum, and reverse pivot shift. Ail 70

peL injured knees revealed a positive gravit y sign, ln

presented positive active reduction, and aU of thom h,ld

posterior subluxation under ùnaesthesia. Poster j or' f;t r'C':;:;

radiographie rneasurernents showed rncùn centr:ll poster i or t i b i ,lI

displacernent of 10.4 mm in the peL invol ved group compll rad ta

3.7 mm in the peL intact group.

Grood and coworkers (1988) defined the anterior-poster ior

neutral position wi th the tibj a hung vertically under i ts m-m

weight when no forces were applied and the U gaments \tiC' 1'0

intact. Ta control the angle of flexion as the i ndepcndcnt

variable, the authors manipulated the thigh, insteùd of mov i nq

the shank. Muller (1983) described the neutrai posi tian of

the knee considering the tibia and the femur ta be al igned

neutrally in an anatomical standing position.

The importance in determining the sag i ttal

position of the knee is more effecti vely seen v/hen test inq pel.

disruptions. In these types of injuries the tibia startf; the

test from a more backwards position (posterior sag). Markcd

subluxation may be observed by viewing the profile of the knec

(Muller, 1983; Insall and Hood, 1982). 'l'herefore, j f an

1

.,-

23

anterior force is applied, ~ significant unexpected anterior

displacement will be recorded, revealing a false ACL tear.

Daniel et al. (1982; 1988) and Anderson and Lipscomb

(1989) suggested the use of the quadriceps active test to

mcasure the true posterior 1axity of the knee and ta diagnose

PCL injuries. This test is done at the quadriceps neutral

angle, which is the degree of knee flexion in which

contraction of the quadriceps does not resul t in either

anterior or posterior tibial shift. The authors explained

that the pull of the quadriceps tendon can be divided into a

normal and a shear component. The former is perpendicular and

the later is parallel to the tibial plateau. There is no

shear component at the quadriceps neutral angle. This angle

would occur between 60 and 90 degrees of y-nee flexion (with a

mean of 71 degrees), varying from persan to person. At this

angle, upon quadriceps contraction, the position of the tibia

is independent Jf ligamentous integrity, because the patellar

ligament force is perpendicular ta the tibial plateau. If the

PCL is ruptured, the tibia subluxates posteriorly and the

patellar tendon is directed anteriorly. Contraction of the

quadriceps at this neutral angle results in an anterior shift

of two mill imetres or more. Using this procedure, Daniel and

associates (1988) observed that the contraction of the

quadriceps at its neutral angle resulted in anterior

translation of the tibia in 41 of 42 knees that had a peL

disruption. This anterior translation did not occur: (1) in

24

the contralateral nor':!lal knee of the same subjects: (2) in

knees of 25 uninjured subjectsi and (3) in 25 knees that hùd

an unilateral ACL disruption.

2.7 Instrumented Assessment of Knee Mgtion

Kennedy and Fowler (1971) initially described a clinicnl

testing machine for in vivo testing of tibio-femori.l1

displacement. The authors measured anterior laxity ~lt gO

degrees of flexion and varus-valgus 1axi ty wi th the knce j n

slight flexion by using a radiographie techn irlue as the mot i on

sensor. It was found that normal anterior mobility wùs 5 mm

(with an unspecified stress). Similar measurcments in

patients with injured ACLs showed inereased mobility from G ta

20 mm. Jacobsen (1976) refined the technique of Kennedy and

Fowler (1971). He determined a difference in ilnterior drê\wcl­

between the right and 1eft knees of more than 3. l mm ta br>

abnormal. Torzilli et al. (1981) have aisa reportcd d

radiographie technique to differentiate rotat ion from

translation when measuring anterior-posterior laxity.

Staubli and Jakob (1990) measured ùnterior knec

displacement during manually applied stress with the KT-l000

and simultaneously documented tibial laxity (unstressed and

stressed) with lateral x-rays. The study group consisted of

16 patients each with a documented unilateral chronie l\CL­

injured knee. There were nine women and seven men, with an

age range of 16-35 years (mean of 28.4 and standard deviation

-- -------~~~~~~~~--

25

of 10 years). Patients were measured under peridural

anaesthesia. Measurements were obtained on both knees, flexed

to 20 degrees, with an applied anterior force of 89 Newtons.

The KT-1000 measured a mean difference (involved minus intact

knees) of 5.7 mm (8D=3.1 mm) while for the stress-X-rays this

difference was 6.3 mm (SO=3. 8 mm). A diagnostic level of 3 mm

was adopted. Both methods revealed a significant increase

(p<.Ol) in anterior displacement in the ACL-deficient knee.

8cattergrams representing paired values of simultaneous KT-

1000 measurements and stressradiographic displacements showed

slight correlation in ACL-deficient knees (r=0.58 for a

probability level of 0.02) but no correlation in intact knees

(r=0.58 for a probability level of 0.98).

Markolf et al. (1978), Shino et al. (1984), and Daniel et

al. (1985) have developed evaluation instruments with

mechanical testing systems to measure anterior-posterior

laxity. Each of them presented their own protocol wi th

different degrees of freedom limited by constraints to tibial

motion, amount of force and displacement sensors, which makes

it difficult to compare their results.

01 iver and Raab (1985) reported a computerized measurement

Q~vice, the Genucom Knee Analysis System (FAR Orthopaedics,

Inc.), which was designed to assess joint flexion-extension,

va~us-valgus, anterior-posterior translation, and internal-

external rotation. The Genucom (Oliver and Coughlin, 1987;

Baxter, 1988; Emery et al., 1989), the ueLA Clinical Testing

Apparatus (Markolf et al., 1978), the HEDmetric Arthr-omctt'!'

models KT-IOOO and KT-2000 (Daniel et al., 198~), the> stry],.C't­

knee-Iaxity tester (Boniface et al., 1986) ':lI1d the 1\11('(>

signature System (Riederman et al., 1991) <1re the devices lh.lt

have been most widely used or reported.

Markolf et al. (1976) reported il stlldy lIsing the> ue!.!\

Apparatus testing 49 uninjured subjects. It wùs documentc'cl

that maximum anterior-posterior laxity occurod at 7.0 doqrcet,

of flexion. Average anterior-posterior lùxity undcr i1 IOilll of

200 Newtons was 5.5 mm at 20 degrees and 4.8 mm ù t 90 docJ rCt'!;

of knee flexion. They also found a 25 to '::'0 pcn~cnt dc'cr'C'd!,('

in laxity when the patient tensed the muscles cros:-Jinq tlH'

knee. With this device, it has been shown thé1t ,1l1tcriol"

laxity in ACL-deficient knees is best meùsured at 20 deqrc(lf,

of flexion (Markolf et al., 1984). The mean anterior l~xity

at this angle for ACL patients was 10 mm, with i1 mC,ln

involved-intact difference of 5 mm.

Daniel et al. (1985) have reported the results of testinq

338 uninjured and 89 ACL-def icient subj ects us ing the K'r-] 000.

with the knee at 20 degrees of flexion, the mean anterior

displacement at 89 Newtons for the uninjured subject~ was ~.]

mm. Persons with ACL disruptions had a meùn displaccment of

13 mm. Right-to-left variation in anterior laxi ty vldS l(>~_~~;

than 2 mm for 92 per cent of the normal jndividuals, and more

than 2 mm for 96 per cent of those with ACL disruptions.

The Stryker Knee Laxity Tester was used by Boniface et al.

27

(1986) to assess 30 ACL-deficient and 123 normal subjects.

The authors reported an involved-intact knee difference of 2

mm (anterior displacement) to be significant for an ACL injury

with an accuracy of 88 per cent.

Comparisons arr.ong measurements made on different devices

and betwcen their ~esults and clinical evaluation sometimes

leads to different conclusions. For example, values recorded

as normal by Daniel et al. (1985) were in the same range as

those reported by Gurtler et al. (1987) for ACL injured

patients. Aiso sex differences were found by Oliver and

Coughlin (1987) in aIl knee floxion angles, by Markolf et al.

(1978) in sorne of them, but not by Torzilli et al. (1981) in

any of them. This can be explained since tibial motion may

occur in six dcgrees of freedom: three translations and three

rotations. As a result of the lack of symmetry between the

femora] condyles and the tibial plateaus many of the motions

are linked or coupled. This explains the "screw-home"

mcchanism, when there is combination of extension and

automatic external rotation (Muller, 1983). Looking at

different instrumented systems, if the testing device imparts

constraints on one motion, it will diminish the displacement

in the linked motion(s) (Daniel and stone, 1988). For

example, if the ACL is injured, a small anterior tibial

displacement is measured when the knee is tested in a device

with one degree of freedom compared ta tests in an apparatus

with four degrees of freedom. For instance, the ueLA

') l' • <'

Instrumented Cl inical Testing Apparatus showed less antct" i ot-

laxity than the KT-lOOO in the sarne group of p~1tients. 'l'ho

DCLA device stabilizes the femur and the ankle riCJ id t Y

(Markolf et aL, 1978) while the K'l'-lOOO arthrometer of fon;

less constraints to the leg (Sherman et al., 1987).

Another factor that affects laxi ty rneasurements i8 mw-;c 1 ('

contraction during assessment. First, it atfects tho Joint

starting position (Daniel et al., 1988). [t is cl Iso cdp,\b 1 c'

of having a significant effect on the overall tibio-fomor~l

motion. Markolf et al. (1978) documcnted that in tcst.ing fOI"

anterior-posterior tibial displacement, IPuscle acti vi ty 1" '" ">

able to bring the knee joint laxity eown to 50 percent.

2.8 The Genucom System

The Genucom (FARO Medical Technologies, Inc., Montre;} l ,

Quebec, Canada) is an apparatus that consists of a reclinjnq

chair mounted on an electrogoniometer with six degrce~; 01

freedom coupled wi th amuI tidirectlonal torce transducC' r

platform and data reduction software. The dev lce was producc>d

ta address the problem of dlfferentiating in vivo ligamenlous

force and displacement measures from other soft tiSr,U0

movements at the knee joint.

The Genucom ofters a procedure named soft U sr:;uc

compensation, a step in the patient installation protocol.

This procedure constitutes the essential innovation of the

system (Emeryet al., 1989). According to the Genucom Manual

'.

,~

29

(FARO, 1984), the procedure is accomplished through the

application of passive external forces applied by the examiner

on the soft tissue in each plane of motion about the fernur.

These applied forces and the subsequent displac~ments between

the tibia and +.:he femur are recorded by the system. The

resultant motion of the soft tissue is later used to correct

forcejdisplacement readings ~or each of the six degrees of

freedom. The procedure is performed each time the limb is

tested, taking into account that each subject's limb has its

own anthropometric characteristi~s. The forces are applied

twice in the six directions relative to the femur: medial,

lateral, superior, inferior, anterior and posterior. The

forces are applied twice to allow the machine to establish a

lJrrelation between the two correspondent forcejdisplacement

curves obta ined. The manufacturer recommends a correlation of

at least 85 percent as an effective soft tissue compensation.

Later, when the clinical tests are applied the machine

subtracts the soft tissue motion from the total displacement

and therefore only pure movement of the tibia irl relation ta

the femur i8 measured. An accuracy of 1 mm (+j-) on

translation or sliding displacements, 1 degree (+j-) on

rotation displaceffients~ and 1 Newton (+/-) on applied forces

is claimed for the device (FARO, 1984) .

Extensive research has been produced using the Genucom

since it was initially designed. Askew and associates (1987)

assessed the kinematic variables of normal, ACL deficient and

------_ ..... _- ... _---------.

30

thirteen knees of fresh human cadavers that had their menisci

removed. The authors found a significant increase (p,-. 005) in

anterior laxity after sectioning of the ACL. This increas0

was larger at 30 degrees than at 90 degrees.

Baxter and Wiley (1988) showed that partially and

completely displaced fractures of the tibial spi ne in chi Idron

can lead to a measurable residual anterior laxity and 105s of

extension. The authors studied paediatr ie kncc ligament

laxi ty in a normal population examining 464 knees 0 f 2 J 2

children aged between 7 and 14 years. There were no sex or

bilateral differences 1 but the ch ildren 's percenti] e [or

height and weight influenced their lmee laxi ty 1 wi th the

smallest children showing highest values for lRxity. Also,

there was clear evidence that as the age of the chi Id

increased, the absolute values for laxity decreased, showjng

that the ligaments appeared to be more resilient.

In 1989, Anderson and Lipscomb compared knee lLlxi ty val ues

recorded using the Genucom, KT-IOOO and stryker ta dctormino

if their respective measurements were helpful in diù~~0sjn~

isolated cruciate and combined ligament injuries bal ore

surgery. There were sorne difficulties when comparinq t.he

results obtained with the three devices. Different skills and

techniques are necessary to operate them, diffcrent test

protocols are recommended by the manufacturers 1 such as

different angles of flexion, constraining of motion by the

Genucom (as the machine gives a warning to the examiner when

1

31

there is more th an five degrees of tibial rotation), and

different tools to rneasure knee angles. Even with these

differences, the authors pointed out that involved minus

intact values of 3 mm or more at 30 degrees of flexion could

be considered diagnostic of an ACL tear for each device. The

Genucom was quite versatile, more accurate in measuring

collateral and rotatory instabil i ties, and the best for

diagnosing PCL tears. Its accuracy in assessing ACL

disruptions was the lowest at 30 degrees. However, the system

permits the application of other tests (pivot shift and genu

recurvatum) to assess ACL integrity which improves its

accuracy.

McQuade and co-workers (1989) measured the tibial rotation

in anterior cruciate deficient knees in four cadaver knee

joints. They found that, between 20 and 90 degrees of

flexion, before and after isolated ACL lesions, tibial

rotation is not constrained by the ACL. AIso, it was

suggested that tests combining tibial rotation and anterior

drawer might help to identify collateral ligament tears.

The objective practicality and rellability of the Genucom

!las also been assessed in past experiments. Highenboten

(] 986) compared males and females. Zero-order correlations

showed values between 0.70 and 0.90. T-tests for correlated

means revealed no significant differences between two trials

for several clinical tests.

Oliver and Coughlin (1987) demonstrated a high ccr.relation

32

between the system and clinical evaluations of 38 patients.

The authors employed a two-grade system (less than 5 mm or

greater than 5 mm involved difference in laxi ty) to dcfine ,1

measurable clinical criterion to be used wi th tlle system.

Concordance of the machine and cl inical di agnosi.5 was observed

in many cases.

Emery and associates (1989) tested thirty fe1l1ales and

twenty males with no injuries during two sessions. No

significant differences were found within testers and bctweon

sexes (when weight and height wcre usod as corrcctin~

factors). Significant bilateral differences between right àncl

left sides were also not encountered.

Highgenboten, Jackson and Meskes (1990) concluded thàt

reproducible results could be obtained with the Genucom. This

was supported by the fact that on 16 of the possible 20 test

values of their study, correlation values greater thQn 0.80

were found. On the other four values, correlation

coefficients were greater than 0.70. The authors aIse noted

no significant differences cornparing each individual's right

to left leg. Their results were consistent with the findinqs

of Daniel et al. (1985) and Sherman et al. (1987) vlho sho",(~d

no test differences for age and gender. The mean rcsults 01

their research across both legs were an anterior displacement

of 5.6 mm with a standard deviation of 3.1 mm and a posterior

displacement of 2.5 mm with a standard deviation of 2.3 mm.

It was established that the difference between involved and

l 33

non-involved legs in the ACL normal patient was 2 mm, compared

to 12-13 mm in the ACL deficient patient. Sorne ACL injured

knees had less posterior laxity than the non-involved

contralateral ones which was attributed to a r -e-test

posterior "sag" in ACL deficient knees. On the other hand,

Daniel et al. (1988) found no significant previous subluxation

in ACL patients.

Wroble and associa tes (1990 ) investigated the

reproducibility of anterior-posterior and varus-valgus stress

tests in 10 control subjects and three unilateral chronic ACL

injured patients using the Genucom. 'rhe researchers also

studied the effect of errors in the digitization procedure (a

part of the patient installation protocol) on anterior­

posterior translation measures. The resul ts revealed

significant day-to-day differences in individual subjects, but

no intraexaminer test-to-test effect. Translation measures

were significantly affected by changing the location of the

tjbial joint line digitization points in the anterior­

posterior or proximal-distal directions at 30 degrees of knee

flexion and when both the lateral and medial points were

moved. The authors advised care in interpreting the meaning

of a single measurement or of repeated tests made within a

single seating. They recommended meticulous guidelines in the

digitization routine, diligence in assuring patient

relaxation, and attention to detail throughout the procedures.

3.1 Introduction

CHAPTER III

Methods and Procedures

34

The main purpose of this investigation was to establish

methods to characterize cruciate ligament disruptions of the

knee using the Genucom Knee Analysis system. Th LS Wll!:;

attempted with the tibia in the resting and the nC'utr,ll

positions. A quadriceps contraction technique (Danie] et al.,

1988) was employed at 60, 70, 80 and 90 degress of knce

flexion. Values of laxity were obtained at 60, 90 and lJO

Newtons.

sessions.

Subjects were submi tted to two ...-;eparLltc tcsti ne]

3.2 Subject Selection and Treatment

Twenty three subjects were selected from lists of pati ents

obtained from orthopaedic surgeons and physiotherapy clinies.

After being contacted by phone and explained the methods anJ

objectives of the study, 20 individuals agrecd to participùto

as volunteers.

Detailed explanations of the researeh project were givcn

when the subj eets came to the laboratory. Subj ects read,

understood and signed an informed consent form (Appendix 1)

before their first testing session. rrhis form had boen

previously approved by the ethics eommittec of th0 F~cu]ty of

Education at McGi11 University. Subjects werc also requircd

1 35

to fill out a subject information form (Appendix 2) in order

to provide detailed medical information. Of the 20 subjects,

10 sustained unilateral chronic anterior cruciate ligament

injuries and 10 had unilateral chronic posterior cruciate

tears. The opposite knee had no abnormalities.

To establish ACL and PCL deficiencies, aIl subjects were

tested on the Genucom system with a force application of 90

Newtons. For ACL patients, the parameter of inclusion was

anterior tibial displacement equal or greater than 3 mm for

the involved leg compared to the intact leg when assessed at

60 degrees of flexion. For PCL patients, the parameter of

inclusion was posterior tibial displacement equal or greater

than 2.5 mm for t~e involved leg compared to the intact leg

when assessed at 90 degrees of flexiun. This operational

definition excluded two ACL and two PCL injured individuals

from the experiment. The sample size was thus reduced to 0

subjects.

The 16 subjects in this investigation ranged in age from

16 to 37 years. There were five males and three females in

the PCL group and three males and five females in the ACL

group.

3.3 ~esting Instruments and Protocols

3.3.1 The Genucom System

The Genucom Knee Analysis System (FAR orthopaedics, Inc.)

is a device that includes a reclining chair mounted on a six

36

degree of freedom electrogoniometer linkage. This goniometer

is attached ta the distal third of the tibia, where it records

the knee position (joint angle) and displacement (tibial

laxity) based on previously digitized coordinates.

within the seat there is also a six compone nt forco

dynamometer to measure external forces and moments placed on

the knee joint. The system is linked ta a computer for dat~

acquisition and processing.

The Genucom is controlled by software placed into one al

the two disk drives located in the inferior portion of the

chair. The Genucom program formats diskettes, where each

subject's data is stored.

The Genucom examination started with the subject seating

on the chair. The trunk was restrained with a velcro boIt at

the waist. Three thigh pads compressed and restralneù the

distal third of the femur in the medial, lateral and posterior

directions. First, the lateral pad was tightened. Forces

equal to 90 and 130 Newtons were then applied to the superior

and medial pad respecti vely, and tightened. 'J'wo latera 1 pact:;

were also applied on the greater trochanter arOd. l Il th j~;

manner the trunk, hip and fernur were stabil ized.

Seven anatomical landmarks of the lower extremity were

digitized to establish a coordinate system on the knee, ta

which aIl movements were referenced. The digitizcd landmarks

included: (1) tibial crest 13-16 cm below the tibial tubcrclc,

(2) tibial crest 5-7 cm below the tibial tubcrc]c, (1) tibidl

37

tll~·.rcle, (4) medial edge of the tibial plateau, (5) medial

femoral condyle at half-width, (6) lateral femoral condyle at

half-width and (7) lateral edge of tibial plateau.

The innovation of the Genucom examination includes a soft

tissue compensation procedure performed for both active and

passive types of tests. This procedure accounted for the

amount of soft tissue compress ibil i ty so that only true tibial

and femoral motions could be measured separately. Through a

compensation, soft tissue deformation was accounted for in

medial, lateral, superior, inferior, anterior and posterior

directions (relative to the femur). This was achieved by

applying manual forces in different directions. Each

procedure was always performed two times according to the

following:

(1) A force of 130 Newtons force was applied with the palm of

the hand to the medial and then to the lateral femoral

condyle.

(2) A force of 130 Newtons was appIied ta the top of the

fernoraI condyles downwards.

flexion.

The knee was at 90 degrees of

(3) A force of 130 Newtons was applied onto the heel of the

foot in the superior direction moving the distal end of the

fernur anteriorly. 'l'his was performed wi th the knee at 90

degrees.

(4) A force of 130 Newtons was applied to the patella in the

direction of the fernoral axis.

1 38

Each force was applied repeatedly due to the fa ct that the

Genucom software correlated the two soft tissue meilsurcs.

High correlations (90 % or more) betwcen two trials \vere

accepted. Soft tissue compensat ion [or ùcti ve tests WclS

similar, except for the fact that, during force application,

subjects were asked to flex their legs at a 60 degree angle.

This angle was chosen with the assumption that it wou1d be the

angle used in the protocol when quadriceps activity would be

the highest. Therefore, more soft tissue mOVCJl1ent woul d

occur. To maintain the knee at this flexion anrjle (i0

degrees), a goniometer was attached to the patient' s log. 'J'he

reference l ines of the goniometer were aU gned wi th the

patients greater trochanter and latera1 ma11eo]us.

Once the compensation was completed, the e lectrogon iometel­

was attached to the distal end of the leg. 'l'he eXi1m i no 1-

started performing the anterior-posterior examination. Be>loro

test application, the Genucom sampling frequency was set at JO

Hertz.

Before the protocol was initiated, subjects were a1lowed

a 10 minute practice session, with special emphasis on the

application of active tests. They vJGre instructccl hOvl ilnd

when to keep their legs at a flexion an~lc by contrélct i n(.)

mainly their quadriceps muscles. This was done with the help

of the biofeedback unit and the evaluator's instructions.

The Genucom protocol started with three trials at GO, 70,

80 and 90 degrees of knee flexion on the intact s ide vii th the

1 39

subject relaxed (passive tests). The intact side was tested

first in order to develop the subject' s confidence in the

protocol and to prevent muscular defence. At each angle and

trial, three anterior-posterior drawer tests were recorded.

Subjects relaxed with the help of the feedback unit and

evaluator's instructions and judgement.

Following the passive tests, subjects were administered

the active tests with contraction of the quadriceps muscles.

Subjects were tested on the same leg at flexion angles of 60,

70, 80 and 90 degrees. The Genucom system allowed constant

monitoring of the joint angle as its electrogoniometer was

attached to the subject's leg at aIl times. The instrument

indicated a numerical output containing the flexion angle,

force, rotation and moment of the leg. During application of

active tests, the leg was placed at a specifie flexion angle.

The subject was asked to keep that position while the

eva1uator verified that the hamstrings were re1axed by

listening to the auditive output, by observing visual readings

of the feedback unit, and by palpating the posterior aspect of

the subject's thigh. The left switch of the Genucom pedal

control 1er was then pressed. Testing parameters on the

Genucom monitor (force, displacement, rotation, and moment)

were set to zero. Upon activation of the Genucow, by pressing

the right switch on the pedal controller, anterior-posterior

forces were applied.

The involved side was assessed using the same sequence.

40

At each test (anterior or posterior), a manual force \vé1S

orthogonally applied to the proximal tibia. Tibial laxity was

determined at 60, 90, and 130 Newtons for both active and

passive tests.

steiner and co-workers (1990) using the Genucom dcterm ineù

that test variability as a percentage of the measurcmcnt was

greater for stiffness and compliance compared to measuremcnts

of anterior and posterior displacement. They sugqestcd that

the hiqher stability found for laxity scores recommcnd its use

as a dependent variable ta aS5ess knee -joint i ntcqrl ty. 'l'hey

also found that diagnostic sensitivity and corrcctncss won'

less for stiffness and compliance than for those of simple

anterior displacement.

3.3.2 The Biostim 6010

The Biostim 6010 (Mazet Electronique, Inc.), is a [eedb~ck

uni t that gives a numerical analog output of the muscull\r

activity translated into millivolts. The device provjdcs an

auditive sign which varies according to the intcnsi ty of

muscular contraction. Numerical and auditive outputs vICr0

calibrated to their most sensitive mode before ca ch tcstinq

session according to the manufacturer' s rccommenda t l ons (Ma ",cot

Electronique, Biostim 6010 user's manual).

After skin preparation, surface electrodes were attachcd

as close as possible to the motor point of the subject'~)

hamstring muscles according to the manufacturer's

l 41

recornmendations. The ground electrode was placed at the head

of the first metatarsal of the limb to be evaluated so that

the electrode would not interfere with the application of the

test protocol. To minimize rnovement of the electrodes, they

were fixed ta the subject's thigh with tape. The skin surface

was cleaned with alcohol to minimize electrical interferences.

A gel was used to improve electrical conductance.

The Biostim was set to i ts most sensi t ive mode. Each

electrode channel was regulated at 5 millivolts, representing

a true sensitivity of 1.6 millivolts according to the

manufacturer's manual.

After the sensitivity was set, the machi~e's auditive and

visual output were regulated. SUbjects were asked to perform

a maximum contraction of the hamstrings (knee flexion against

a resistance). The potentiometers that regulate auditive

output were calibrated to the 100 percent level during the

maximum contraction.

During test application, sorne movement of the electrodes

was observed. This produced sorne output that co'lld be

confounded with muscular activity. To solve the problem, two

criteria were employed to disregard tests. First, tests were

stored if there was no auditive output. Second, if there was

a sou~d, numerical outputs equal or greater than 5 millivolts

were used as a criteria for exclusion of tests.

It is important to note that no true measurernents of

1 electromiography were employed. The use of the Biostim 6010

· l was an atternpt ta: (1) select tests withaut undesirùblc

external muscular guarding and (2) help subjects to cantrQct

mainly their quadriceps when the active protocol Wé1S employcLl.

3.4 Treatment of Data

Each patient had three anterior and threc posterior tesL;

per leg (invalved and intact), per type of test (~ctivc Hnd

passive), and per session (1 and 2). Each test WQS performcd

at four angles of flexion (60, 70, 80, and 90 degreos). Uninq

the raw data, a pragram was designed to read the laxity scores

at ~orces of approximate1y 60, 90, and ]30 Newtons.

Three trials were performed for cach type of test, sossion

and angle of flexion. A mean of the three trials w~s

calculated. A computer program calculated the differenco in

tibial displacement for the involved 1eg compared ta the

intact leg for each subject.

3,5 Statistical Analysis

Means and standard deviations were calculQted for iHJ",

weight and height of the peL and ACL subjects. stat h,t i ca J

analyses were performed using SPSSX (statistjcal Package for

Social Sciences - version X) on the McGi11 university System

Interactive Computing (MUSIC).

A three-factor ANOVA was performed for dnterj or <.lOd

posterjor 1axity scores. The factors were: (1) type of test

(active and passive), (2) session (1 and 2), and angle of kncc

l 43

flexion (60, 70,80 and 90 degrees). A .05 probability level

was chosen for statistical comparisons. 'l'he exper imental

design is presented in Table 1.

Table 1: Experimental Design.

Test

Ses. Sess ion 1

Flex. 60 70 80 90

Subjects

1 2 3

8

Active

Session 2

60 70 80 90

Passive

Session 1 Session 2

60 70 80 90 60 70 80 90

Dependent variable: tibial laxity for involved - intact leg

To test the six hypotheses outlined in chapter l, this

experimental design was repeated for six analysis. These

analyses were:

1. PLAX for PCL patients at 60 Newtons.

2 . PLAX for PCL patients at 90 Newtons.

3. PLAX for PCL patients at 130 Newtons.

4 • ALAX for ACL patients at 60 Newtons.

5. ALAX for ACL patients at 90 Newtons.

6. ALAX for ACL patients at 13 0 Newtons.

4.1 Introduction

CHAPTER IV

Resui ts

44

The obj ectives of th is study were to test crucj ote>

deficient knees under two test starting positions of the

tibia: resting and neutral. Using the Genucom System,

anterior-posterior knee drawer tests (active and passive» wer0

administered to 8 PCL and 8 ACL injured individuals. 'J'Ile

subjects were tested during two sessions with the knec <lt fou/­

angles of fI ex.:... on (60, 70, 80, and 90 degrees). 'l'he dependcnt

variables were posterior tibial laxity (mm) for the PCIJ

subjects and anterior tibidl laxity (mm) for the ACL subjccts.

For the PCL inj ured subj ects, i t was hypothes i :~(~d thilt

posterior knee laxity at GO, 90 and 130 Newtons wou] d be

similar during active and passive tests, dur ing sess ions 1 and

2, and for the four knee flexion angles. For the ACL inj ure 1

subjects, it was hypothesized that anterior knee Jaxity at (J!),

90 and 130 Newtons would be similar during active and pc1SS i Vt>

tests, during sessions 1 and 2, and for the four knec flexion

angles.

4.2 Characteristics of the Subject~

This study included 8 PCL and 8 ACL injured subjccts who

were referred by orthopaedic surgeons. Physical

characteristics of the PCL and the ACL subjects arc incJudcd

45

in Tables 2 and 3, respectively.

Table 2: Physical Characteristics of the PCL Subjects.

Subject

1 2 3 4 5 6 7 8

Mean S. D.

Gender

F F F M M M M M

Age (yrs)

30 28 27 37 26 23 25 36

29.0 5.1

Height (cm)

167.2 177.8 154.9 172.7 177.4 198.1 185.4 182.9

177.0 12.8

Weight (kg)

58.8 67.9 45.3 77.0 65.7 97.5 74.9 90.1

72.1 16.7

Table 3: Physical Characteristics of the ACL Subjects.

Subject

1 2 3 4 5 6 7 8

Meiln S. D.

Gender

M M M F F F F F

Age (yrs)

29 21 16 21 23 26 28 24

23.5 4.2

Height (cm)

177.8 185.4 170.2 154.9 167.6 170.2 154.9 165.1

168.3 10.4

Weight (kg)

77.6 86.2 68.0 49.1 59.0 61. 2 52.2 58.1

63.9 12.7

Medical information was collected on each patient. This

information is shown in Table 4 for the peL subjects and in

'l'able 5 for the ACL subjects. The criteria outlined by Daniel

et al. (1985) and Anderson and Lipscomb (1989) were used for

selection of subjects. AlI PCL patients performed passive

posterior tests at 90 degrees of flexion at a force of 90

Newtons on the Genucom. Ta be included in this study, the

subjects had ta present a posterior knee laxity of at least

·1 G

2.5 mm averaged across six trials. AU ACL patients perfonned

passive ante ri or tests at 60 degrees of flexion at il force of

90 Newtons on the Genucom. To be included in this study, the>

sUbjects had to present an anterior knee laxity of at lcast

3.0 mm averaged across six trials.

Table 4: Medical Information for the peL Subjccts.

SUbject Date of Date of oiagnosis PLAX Injury Arthroscopy (mm)

------------------------------------------------------------1 Feb 1991 Jul.,1991 peL, MM 7 • J ~ 2 Jan 1991 May ,1991 peL 2.60 3 Apr 1989 Aug.,1989 peL, MeL, LM 7 .80 4 Jan 1991 Sep.,1991 peL 2.60 5 Jan 1991 Jun.,1991 peL 2.90 6 Jun 1989 Dec.,1989 peL, MM 3 • Il 0 7 Mar 1989 Aug.,1989 PCL, MCL 2. 70 8 Sep 1990 Feb.,1991 PCL, LCL 2 • (,0

------------------------------------------------------------

Table 5: Medical Information of the ACL Subjects.

Subject Date of Date of oiagnosis ALI\X Injury Arthroscopy ( mm)

------------------------------------------------------------1 Jan. 1990 Apr.,1990 ACL 3. ')') 2 Feb. 1990 May ,1991 ACL rj • '10

3 Feb. 1991 Mar.,1991 ACL, MCL '3 • 'J 1)

4 May 1990 Sep.,1990 ICL Il • Il () 5 Mar. 1990 May 1990 ACL -J • () ()

6 Jul. 1990 Oct. 1990 ACL, MCL, MH 8 • 2 (J 7 Jan. 1991 Jun. 1991 ACL 4 .40 8 Feb. 1990 Nov. 1990 ACL, MCL 5.9';

Legend for tables 4 and 5:

- ACL: Anterior Cruciate Ligament - MM: Medial Mcni~cuH

- peL: posterior Cruciate Ligament - LM: Lateral rlcnlc;éu~-~

- LCL: Lateral Collateral Ligament

- MeL: Medial Collateral Ligament

1 47

4.3 Descriptive Data and ANOVA Results

Results from the Genucom testing are summarized in

relation ta the three independent variables: (1) type of test,

(2) angle of flexion, and (3) session number. Data are

displayed in separate tables for force applications of 60, 90,

and 130 Newtons and for PCL and ACL subjects. Descriptive

data are shown in tables 6, 8 and 10 for PCL subjects and

tables 12, 14 and 16 for ACL subjects. ANOVA results are

presented in tables 7, 9 and Il for PCL subjects and tables

13, 15 and 17 for ACL subjects.

For the "test" variable, there were significant

differences between the active and passive protoco]s at 90

Newtons (Table 9) and 130 Newtons (Table Il) for the PCL

subjccts. The ANOVA results were: F (1,112)=4.58, p<.05 for

PLAX at 90 Newtons and F (1,112)=5.88, p<.05 for PLAX at 130

Newtons. At 90 Newtons, posterior knee laxity averaged 3.53

mm whcn the active protocol was employed compared ta 2.77 mm

during the passive protocol. When force increased ta 130

Newto~s, the posterior knee laxity averaged 4.12 mm with the

active protocol and 3.11 mm with the passive protocol. At

forces of 60 Newtons, the posterior knee laxity aveLùged 2.89

mm with the active protocol and 2.31 mm with the passive

protocol. At 60 Newtons, the F value was 3.56 wi th a

probability level of .06, which exceeded the leve] of

significance adopted for this study (.05).

For the "flexion" variable, there were no signi ficant

1

Î 48

differences in posterior knee laxity at 60, 70, 80 and 90

degrees for forces of 60 Newtons (Table 7), 90 Newtons (Table

9) and 130 Newtons (Table Il).

There were no significant differences in posterior knec

laxity between sessions 1 and 2 for forces of GO Ne\Vton~-;

(Table 7), 90 Newtons (Table 9) and 130 Newtons (T~ble ]1).

The two-factor and three-factor interactions fvr the test,

session and flexion variables were non-signi f icant for the PCL

subjects.

For the "test" var iable, there vIere no si gn i 1 j C.1 nt

differences between the active and passi vc protoco ls at (l()

Newtons (Table 13), 90 Newtons (Table 15) and 130 tJcwton!~

(Table 17) for the ACL subjects. At 60 Newtons, antcrior blCC'

laxity averaged 2.72 mm during active tests compared to J.lR

mm for passive tests.

averaged 4.54 mm when

At 90 Newtons, anterior knee lax i ty

the act ive protocol wùs empJ oyed

compared to 4.12 mm during the passive protocol. Whcn forC0

increased ta 130 Newtons, the anterior knee laxity avcril(j0u

6.76 mm with the active protocol and 6.09 mm with thc passlv0

protocol.

For the "flexion ll variable, étlthough thcre wcrc no

significant differences in anterior knee laxity at GO, 70, BO

and 90 degrees for forces of 60 Newtons (Table 13), 90 nelr/tom,

(Table 15) and 130 Newtons (Table 17), a trend can be observod

in the data (Figure 1). At the three levels of force,

anterior laxity decreased when knee flexion angle increased.

1

-1 49

A larger sarnple size with less variability might have elicited

significant differences in the "flexion" variable for the ACL

injured subjects. The same trend can not be noted for the PCL

subjects (Figure 2).

There were no significant differences in anterior knee

laxity of the ACL subjects between sessions 1 and 2 for forces

of 60 Newtons (Table 13), 90 Newtons (Table 15) and 130

Newtons (Table 17) •

The two and three-factor interactions for the test,

session and flexion variables were not significant for the ACL

subjects.

J

Table 6: Mean PLAX at 60 Newtons for the PCL Subjects.

Test Flexion Session Mean S.D.

Active 60 1 3.26 1 • 7 ~~ 2 3.44 1.84

70 1 2.95 1. G2 2 2.89 1. 50

80 1 2.45 ] • J 0

2 2.65 0.8J

90 1 2.82 1. 65 2 2.69 1. 71

Passive 60 1 1.85 1.77 2 1.92 l. ·19

70 1 2.02 1 • <) r)

2 2 . 17 1 ,(. ~

80 1 2 . ] '/ 7. () l 2 2.21 1. ,) /

90 1 2.99 ?. ï 7 2 2.76 ?. 1 0

collapsed cells Mean S.D.

Test Active 2.89 1 • 'j 1

Passive 2 • 11 1. B ~

Flexion 60 2.G2

70 2.56 ] . (, '-,

80 2.42 1 • il 'J

90 2.8? ;J • () l

------------------------------------------------------------SI;!ssion 1 2.59 1 • H 1

2 2.62 ------------------------------------------------------------

51

Table 7: ANOVA resul ts at 60 Newtons for the peL Subj ects.

Source df ss MS F p

'rest (T) 1 10.75 10.75 3.56 .06

Session (S) 1 0.02 0.02 0.01 .93

Knee Flexion (F) 3 2.57 0.86 0.28 .84

T x S 1 0.01 0.01 0.01 .96

T x F 3 11.13 3.71 1.23 .30

S x F 3 0.53 0.18 0.06 .98

T x S x F 3 0.63 0.21 0.07 .90

Error 112 338.37 3.02 ------------------------------------------------------------

-...

Table 8: Mean PLAX at 90 Newtons for the PCL subjûcts.

Test Flexion Session Mean S.D.

Active 60 1 3.99 2.22 2 4.35 2.39

70 1 3.26 1 .6·1 2 3.74 1 .98

80 1 /..85 1 • ·1 1 2 3.21 () • H,'

90 1 J. ,1} 1.hS 2 3.41 1 • 1·1

Passive 60 1 1.90 1 • 4 () 2 2.41 ;;> • :~8

70 1 2.12 ] • ') t)

2 3.01 ~) . l 'J

80 l 2.79 ~l • 2 ()

2 2.94 1 • f) l

90 l 3.40 .? • () 1

2 J.55 ?BO

Collapsed cells Mean [j • f).

Test Active 3.51

Passive ;;>. TI

Flexion 60 J.lf)

70 ].01 1 • (Jo1

80 2.95 ] • (.4

90 3.44 2. Fi

Session 1 2.97 1 • 0~

2 3.33 ;? .04

------------------------------------------------------------

1

53

Table 9: ANOVA Results at 90 Newtons for the peL Subjects. ------------------------------------------------------------Source df SS MS F p ------------------------------------------------------------Test (T) 1 18.60 18.60 4.58 .03(*)

Session (S) 1 4.20 4.20 1.03 .31

Knee Flexion (F) 3 4.51 1.50 0.37 .77

T x S 1 0.12 0.12 0.03 .86

T x F 3 20.99 6.99 1.72 .17

S x F 3 1. 61 0.54 0.13 .94

T x S x F 3 0.40 0.13 0.03 .99

Error 112 455.17 4.06 ------------------------------------------------------------(*) p < .05

Table 10: Mean PLAX at 130 Newtons for the peL Subjccts.

Test Flexion Session Mel1n s. [).

Active 60 1 4.72 :: •• ~ 0 2 4.95 :'.32

70 1 4.05 2.23 2 4.44 2.2G

80 1 3.27 1.BG 2 3.64 0.99

90 1 3.90 ;~ • 31 2 4.00 ) .)C)

Passive 60 1 2.00 l. ~d 2 2.67 1.60

70 1 2.22 /. 1 r)

2 3.55 ) ~- 1 ..... :.J J

80 1 2.94 1 • ~30 2 3.47 :J. (,l

90 1 3.72 3 • () n 2 4.29 L ·1tl

Collapsed cells Mean ~; . /).

Test Active 4.12 2.0tl

Passive 3. Il

Flexion 60 3.59 /.4'j

70 3.57 ;~ . ~ 'J

80 3.33 l.,n

90 3.98 /.. (J'J

Session 1 3.35 2.24

2 3.88 2.42

1 55

Table 11: ANOVA Results at 130 Newtons for the peL Subjects. ------------------------------------------------------------Source df SS MS F P ------------------------------------------------------------'l'est ('l' ) 1 32.00 32. 00 5.88 .02 ( *)

Session (S) 1 9.14 9.14 1.68 .20

Knee Flexion ( F) 3 6.96 2.32 0.43 .74

'}' x S 1 1.85 1. 85 0.34 .56

'l' x F 3 31. 26 10.42 1.91 .13

S x F 3 1. 22 0.41 0.08 .97

rr x S x F 3 0.64 0.21 0.04 .99

Error 112 610.30 5.45 ------------------------------------------------------------(*) p < .05

Table 12: Mean ALAX at 60 Newtons for the ACL Subjccts.

Test Flexion Sessi on Mean S • Ll.

Active 60 1 2.90 1 .·10 2 3.42 1. 4 3

70 1 2.60 0.79 2 4.19 .: • 2'1

80 1 2.69 O. B()

2 2.84 1. () 1

90 1 1.97 (). t)C)

2 2.75 1 • j ()

Passive 60 1 1. G·1 1 .·1 (, 2 3.96 1 • :Hl

70 1 3.29 I.n 2 3.51 ;> .Ot)

80 1 2.95 l • (l 1 2 3.09 1 .72

90 1 /..60 1. 0 1 2 2.44 1. In

Collapsed cells Mean s . [).

Test Active 2.92

Passive 3.18

Flexion 60 3.48

70 1.40 l . 'Il

80

90 ::? 4 4 J • 1 /

------------------------------------------------------------[3ession 1 2.83 1 • ? 1

2 3.27 1 • "/8

------------------------------------------------------------

57

Table 13: ANOVA Results at 60 Newtons for the ACL Subjects.

Source df 88 MS F P ------------------------------------------------------------Test (T) 1 2.23 2.23 .97 .33

Session (S) 1 6.35 6.35 2.75 .10

Knee Flexion (F) 3 22.45 7.50 3.25 .08

T x 8 1 3.16 3.16 1. 37 .25

T x F 3 1. 74 0.58 0.25 .86

S x F 3 2.59 0.86 0.37 .77

'1' x S x F J 2.40 0.80 0.35 .79

Error 112 258.63 2.31 ------------------------------------------------------------

.... ~------------------------------------------------------

Table 14: Mean ALAX at 90 New~ùlls for the ACL Subj ccts.

Test Flexion Session Nean S. D. ------------------------------------------------------------Active 60 1 4.45 1 • q (,

2 4.96 ') 3 1 ,- .

70 1 4.27 1 • '/ (1

2 S.70 \. I,l

80 l 4.19 1 • ,1 C)

2 4.56 3 • ~) 1

90 1 3.67 l . (~ï

2 4.52 ;) • 1) (,

------------------------------------------------------------Passive 60 l 4.41 1 • :~ (,

2 5. ~~2 :> . ~ ~ ·1

70 1 Il. ,17 1 • 1 (, 2 4.57 " . '/ .)

80 1 3.81 1 • () 1

2 4.00 ;, . () '/

90 1 ].01 l • l 3

2 J.JG 1. UI,

------------------------------------------------------------Collapsed CE'lls :;. Il.

'l'est Active ) 1 rI , • 1 Il

Passive ,1. 12 1 • ') l

--------------------------------------------------~--- ------Flexion 60 4 . "G ;, . ()')

70 4.76 ;) • ,1 f)

80 4.10 2 ') '1 ~ . ... (.

90 J • C ,1 1 • ï 'J ------------------------------------------------------------Session 1 tl.04

2 4 • G? ;; • (, 1

------------------------------------------------------------

1

l 59

Table 15: ANOVA Results at 90 Newtons for the ACL Subjects.

Source df SS MS F p

Test (T) 1 5.78 5.78 1.19 .28

Session (S) 1 10.93 10.93 2.25 .14

Kncc Flexion (F') 3 27.84 9.28 1. 91 .13

'[' x S 1 1. 36 1. 36 0.28 .60

'l' x F 3 4.23 1. 41 0.29 .83

C' .J x F 3 0.90 0.30 0.06 .98

'1' >: S x F' 3 2.86 0.95 0.20 .90

Error 112 544. 18 4.86 ------------------------------------------------------------

Table 16: Mean ALAX at 130 Newtons for the ACL Sub j C''-~u ••

Test Flexion Session HCùl1 S.D.

Active 60 1 7.10 <1. 1 Cl 2 7. Il 3.8'1

70 1 6.67 J • ~) 3 2 7.37 .\ . / /

80 1 6.::>1 J. lB 2 6.62 ,). JO

90 1 ~.90 2.69 2 6. Il 3. q 1

Passive 60 1 7.71 ·1 • ·1 ·1 2 6.99 ·1. ; ,)

70 l -J • 1 :: \ . ()~; 2 (, . 31! ·1. 1 -1

80 1 t 1.- .... ) ). )a .' •• )(1

2 ,) • () 1 ? JO

90 1 <1.5-; / . il (,

2 '1. "J 1 1 • 1 /

Collapsed cells Mean

Test Active 6.76

Passive G.O,) 1 • ,1 ()

Flexion 60 7.2-3 ,1 • 1 1

70 G.88

80 6.17

90 5.42 ,) . il J

Session 1 6.40

2

61

Table 17: ANOVA Results at 130 N for the ACL Subjects. ------------------------------------------------------------Source df SS MS F P ------------------------------------------------------------Test (T) 1 14.72 14.72 1. 04 .31

Session (S) 1 0.06 0.06 0.01 .95

Knee Flexion ( F) 3 61. 31 20.43 1. 44 .23

'1' x C' .) 1 3.71 3.71 0.26 .61

'l' x F 3 17.78 5.93 0.42 .74

'-' • .:> x F 3 2.41 0.81 0.06 .98

'l' x S x F 3 3.61 1. 20 0.09 .97

Error 112 1587.01 14.17 ------------------------------------------------------------

Figure 1: Knee Flexion and ALAX for the ACL Subjccts

,-_._------------------- ----- -- - -

• 0 Cf) (j) C

0

~ Q)

Z 0 Ct) ,-

,-(j)

0 'l> 0) (1)

~

0) CI) (1)

""'0 C "'-"" 0 C ~ 0 (}) X Z (1)

...) li. (i)

0 (1)

i (1) t'- c + ~

Cf)

C 0

~ (})

Z 0

0 (!) (!)

i • l

1

- -1 -,-----r-------r-- --- - - -1" ,

ex> t- <D L!) ~ (Y) C\J ,- a

(ww) X\flV

Figure 2: Knee Flexion and PLAX for the peL Subjects

-- ------- -----------,------

, ,

co ~I --~I ~---II---.I----II----~I----~

~ W ~ ~ M N ~ o (ww) X\fld

a 0)

u;­a Q) <X) Q) -C>

Q) 'U -c o x Q)

U­a Q)

~ ~ ~

a w

63

en C o ~ Q)

Z o ('f') T"'"'

en c o j Q)

Z o 0)

t en c: o

~ Z o (0

5.1 Introduction

CHAPTER v

Discussion of the Results

It has been weIl documcntcd that posterio!" Cl"\ll'illtO

ligament disruptions cause an incn:~ase in poster i or k!lC'P

laxity scores (King et al., 1986) and can be best ::.hown whcn

the knee is examined at 90 degrees of flexion (Grood ct ~l.,

1988). On the other hand, anterior cruciatc Ugament injuL"ic~~

cause an increase in anterior knee laxity scores (M~rkolt 0t

al., 1978; 1984). This can be most clearly (~l icitocl \..;I1(>n tlw

knee is flexed from 20 to 30 degrees during application 01 tho

so called Lachrnan test (Gurtler et al., 1987).

However, él distinction bet\.,een ACL and PCL J iqùmont

injuries requires the establishment of a tibial neutra 1 po i nt,

from which tibial displacements can be referenced. F'rdrü: 1 in

et al. (1991) and Torzilli et al. (1981; 1984) omploYt>d !;trer~~;

radiographie techniques to compare norm.:ll anù cruci Lltc in) url·ri

knees. Using the KT-lOGO {MEDmetric, San Diego, CdJ ifornin),

Daniel et al. (1982; 1988) demonstrated that the Quadricoph

Active Test can oe used to diagnose poster ior crue i dt<..'

ligament disruptions and to measurc posterior laxity at the>

knee. Cannon and Lamoreux, in a persona l commun j Cd t i on

referenced by Anderson and Lipscomb (198 'J), suggcsted thù t

true posterior tibi al displacement could be determined by

placing the knee at 90 degrees of flexion and zero i ng the

65

stryker with the quadriceps contracted. This would enable the

examiner to determine if an instability could be secondary to

an anterior or posterior cruciate ligament in jury.

'l'he present investigat ion examined tibial displacement

values relative to the initial testing position of the tibia

in the sagittal plane during anterior-posterior assessment of

cruciate ligament injured knees on the Genucom Knee Analysis

Systen. Patients were submitted to active and passive

i1nterior-posterior knec drawer tests at 60, 70, 80 and 90

degrees ot flexion during two evaluation sessions. Laxity

scores wcre estimated at forces of 60, 90 and 130 Newtons.

5.2 Type of Test and Laxity in Cruciate Deficient Knees

Orthopaedic surgeons have usually assessed the integrity

of knee ligaments by measuring the arnount and direction of

tibial motion that results from manually applied forces

(Markolf et al., 1978). These are passive tests since the

displacing force is applied by the examiner. Another method

of assessing ligamentous and capsular integrity is to measure

the change in joint position which results from active

contraction of the patient's muscles. These are active tests

Binee the patient's muscles provide the joint displacement

force (Daniel et al., 1988).

At full extension, the patellar tendon lies anterior to an

imaginary reference line that is perpendicular to the surface

of the tibial plateau and passes through the tibial tubercle

1

(Muller, 1988). As the knee approaches flexion, the lemul"

rolls posteriorly on the tibia, guided by the (TUC L.ltt">

ligaments. The orientation of the patellar tendon c11Lll1qcs

continuously from anterior to posterior with respoct to the

reference line (Goodfellow et al., 1978). 'l'he resul ttlnt !:~l1e,ll'

force produced by the pull of the patellllr tendon on tll0

tibial tubercle changes from anterior to poster iOI' \-J i tl!

increasing flexion angle. In the normal knee, the crOG~~ovel'

from anterior to posterior shear occurs between GO ~nd 90

degrees. At this position, called 1:he quadd ceps I1[>Ut I"dl

angle, the tibia does not shi ft anterior l y or poster j or 1 y \-Jl!ell

the quadriceps muscles are contractcd (Dùn je l et él J ., 1 ') ~:rn .

In the ACL-def ic ient pi1t ient, i1nter ior sub] UXélt i on n j ttH'

tibia can be demonstrated during applicl)tion of the qu,Hlr i ccp:;

active test at 20 to JO degrees of knee flexion. 'l'his w,,:;

first demonstrated by Daniel et al. (1988) on the KT-l0()() ,lnr!

later achieved by Frankl in et al. (1991) who eJT1p] oyerJ d

quadriceps contraction technique to assess ACL j nsLüJ il j t i 0:;

through x-rays. This subI uxation occurs bccausc a qUùdr 1 cop:;

contraction beyond its neutral angle causes anterior tibial

displacement (Anderson and Lipscomb, 1989).

5.2.1 PCL Injured Patients

In 1988, Daniel ct al. reported on the uco of th0

quadriceps active test to determine posterior knee lnxity ~nd

PCL disruptions. Part of the sample included 24 patients with

67

unilateral chronic peL injuries. The testing instrument was

the KT-1 000. Tests were performed at 89 Newtons of force.

Their knees were tested at 30 degrees of flexion and at the

posi tian that had been determined ta be the quadriceps neutral

angle in the intact side. with the lower 1imb re1axed and the

knce in 90 dcgrees of flexion, the tibia shifted anteriorly on

contraction of the quadriceps in aIl but one of the 24 knees

thùt had a chronic rupture of the posterior cruciate ligament.

The subjccts had mcan posterior differences (involved minus

intact knecs) equal ta 2.1 mm during passive tests and 7.3 mm

during active tests, which were significantly different at the

.001 lcvel. The present experiment showed similar significant

diffcrenccs (p<.05) between active and passive tests at 90 and

1JO Newtons of force. Mean posterior differences (involved

minus intact knees) were 2.89 mm for active tests and 2.31 mm

for passive tests at 60 Newtons, 3.53 mm for active tests and

2.77 mm for passive tests at 90 Newtons and 4.12 mm for active

tests and J.11 mm for passive tests at 130 Newtons. A larger

sample might have provided enough statistical power to

dcmonstrate significant differences at 60 Newtons of force.

The values recorded for laxity in the present study may have

becn smaller since tibial rotation was lirnited when compared

to tests performed on the K'l'-1000. The resul ts of bath

experiments confirmed that a quadriceps contraction was able

to cause a signifj cant anterior shift of the tibia in peL

injured patients who had a previous posterior tibial sag prior

to the posterior knee drawer test.

5.2.2 ACL Injured Patients

The present experiment tested ACL patients betwecn 60 and

90 degrees of flexion. The ANOVA results revealed no

significant differences (p>. 05) between active and pilS~:::;i Vt>

tests at 60, 90 and 130 Newtons of applicd force. 'l'his (\grco~~

with results presented by Daniel et al. (1988). In theit' AC/,

injured patients, there was no more than one millimctrc 01

anterior translation after contraction of the quadr l Cepfj w i lh

the knee at 90 degrees of flexion with a force application 01

89 Newtons. This translation was not significant whon

comparing active and passive tests. Althouqh siqni 1 lL'ant

differences were not found in the present invcsUgation, it

can be observed that for the ACL subjects evaluated at 90 and

130 Newtons, there is more anterior tibial laxity for nctivc

tests. This supports arguments by Anderson and Li pscomb

(1989) that a quadriceps contraction with the kncc floy.c'rj

beyond the quadriceps neutral position, as mny have o('currerj

with some flexion angles employed in the> protoco] 01 thi:.

research (80 and 90 degrees), resul ts in po~~t('r j or

displacement of the tibia. This occurs due to the oricntiltion

of the pull by the patellar tendon. For the ACL sub-jccts, th'.'

tibia was shifted posteriorly after contraction 01 the

quadriceps muscles at angles of flexion beyond tt1C' quarJriccp',

neutral angle. 'fherefore, when an anteriorly di rectc'rj J Qild

69

was applied, more anterior laxity was recorded during active

tests, but not enough to elicit significant differences as

compùred to passive tests.

5.3 Flexion Angle and Laxity in Cruciate Deficient Knees

5.3.1 peL Injured Patients

In 1988, Grood et al. demonstrated that the amount of

posterior translation after the PCL was injured increased as

the knee was flexed, being greatest at 90 degrees. The same

observation was made in the present research. Posterior

tibial laxity showed the highest scores at 90 degrees of

flexion under GO Newtons (2.01 mm), 90 Newtons (2.15 mm) and

130 Newtons of force (2.69 mm). The results for the other

angles of flexion confirm the observations by Daniel et al.

(1988) with greater values for posterior tibial laxity at 60

as compared to 70 and 80 degrees of flexion. It is important

to note that an accurate determination of the quadriceps

neutral angle on the Genucom, as described for the KT-IOOO

(Daniel et al., 1988), was very difficult as the Genucom

goniometer is very sensitive to any slight modification in

knee angle or tibial position.

The fact that no significant differences were found among

knec flexion angles for the PCL subjects is illustrated in

Figure 2 (Chapter 4). This fa ct is also supported by the non-

significant ANOVA results (p=.84 for 60 Newtons, p=.77 for 90

Newtons, and p=.74 for 130 Newtons) and can be explained by

l two arguments.

70

First, the angles employed in the protocol

were not different enough to alter anterior-posterior tibial

displacement as theorized by Anderson and Lipscomb (1 9B9) •

The second argument stems from a l'PC re important observtl t ion by

Gollehon et al. (1987) and Grood et al. (1988). The tluthors

stated th3t both the posterior cruciate ligament tlnd other

secondary restraints are required to maintain rl normnl

anterior-posterior motion of the tibia, particu]arly nt knoo

flexion angles less than 45 degrees. This points out thnt the

secondary restraints play a more important role in stnbilizinq

tibial posterior laxity at angles that are ClOSE to extension

of the knee. These secondary restraints to posterior

translation are less effective when the knee ls evaIuéltod

between 60 to 90 degrees of flexion. Therefore, once the

posterior cruciate ligament is injured, tcsting postorior

laxity of the knee between 60 and 90 degrees of flexion ShC>llld

reveal similar values since slackness increases in the

secondary restraints which limit posterior tibial trélns]rltion.

According te Butler et al. (1980), these structure~~ art! the

posterior part of the lateral area of the capsule, the mollidl

area of the capsule, the collateral 1 igaments ~1l1d the meu i dl

area of the capsule.

5.3.2 ACL Injured Patients

Results from previous studies have shawn that as th0 kncc

flexion angle approaches extension, there is an incrcose jn

71

rccorded anterior laxity of ACL deficient patients (Butler et

al., 1980: Hosenberg and Rasmussen, 1984). This is in

agreement with the findings of the present investigation when

comparing ALAX across 60, 70, 80 and 90 degrees. It is

import<:mt to mention that the increase in ALAX is best

demonstrated at 20 to 30 degrees of knee flexion (Gurtler et

al., 1987). lIowever, these angles were not employed as part

of the protocol of this experiment.

A cJear trend in ALAX scores was observed in the present

reseal~h, as illustrated in Figure 1 (Chapter 4). As knee

f J c·/.! on angle increased, anterior knee laxi ty va J. ùes

clecreased, which agrees with previous tindings. HO\vE'ver, this

trend and the ANOVA results (p=0.08 at 60 Newtons, p=.13 for

90 Newtons, a:1d p=.23 for 130 Newtons) suggest that there

might have been a significant main effect for the variable

flexion angle if a larger nurrl'er of ACL deficient subjects

wore tested. Three arguments support the non-significant

finctings among flexion angles for the ACL subjects. First, at

f 1 ex ion angles less than the quadriceps neutral angle, a

quadriceps contraction previous to the anterior drawer brings

the tibia anteriorly through the pull of the patellar tendon

([)anip 1 et al., 1988; Anderson and Lipscomb, 1989) .

'l'herefore, decreased ALAX scores might have been recorded at

angles of flexion of 60 and 70 degrees. Second, the opposite

occurs when the quadriceps is contracted at 80 and 90 degrees

when the patellar tendon pulls the tibia posteriorly before an

"

"1 ;l

anterior force is app' 'ed. Therefore, an incrcascd anterlor

, axi ty might have beel -ecorded a t knce flex i on all91 c~, 0 1 ~~ 0

and 90 degrees during the active protocol. 'l'hird, ,\t the'

angles of f] exion employed in the protocol (w i th tl10 knpc

close ta flexion), the secondary rcstra i nts to [onv,) rd ti b i <11

displacernent were taut (Gollehon et al., 1987). 'l'his may hi1ve

decreased the magnitude and the variance recordcd [or scorc~;

of ALAX. According to Rovere and Adai r (l9BJ), tll('!;,

secondary restraints are the medjal col1atcr(1l 1jtJdrn0nt, tlw

retinacul um and the poster ior port ion 0 r tlw c;\ p~;\ll (' .

5.4 Reprod1'cib i li ty of Sess i ons on the GcntJ.t;PJTI

In 1985, Emery et al. found no significant dl t t ('/'('/W0';

between first and second testing sessions 01 dl [forent tc':;tcn;

for any anterior/posterior tests complcted on the G('I1IICO/TI.

Subjects had no injuries ta their knees. fIo jnlorrndti()l1 \·/d',

avail able regarding specifie resu l ts 0 f tria ls or' 1 C!ve 1:> 0 f

force that were used to calculate knee laxi ty. 'rests 'vIC rc

performed at 30 and 90 degrees of flexion.

Highgenboten an~ associates (1990) reported on results of

reproducibility testing of the GenUCOll. ':In 20 subjccb~ ',li th

intact knees. They found means and standard errar:: j or

anterior laxlty at 90 degrees of 7.92 mm and 0.51 mm in trial

1 and 8.01 mm and 0.47 mm in trial 2. A t-test for correlntcd

rneans indicated no significant differences (p<. 05) betvlcen any

of the pairs of the independent trials.

73 F

l Wroble et al. (1990) tested five males and five females

with no history of knee problems on the Genucom. Day-to-day

vüriabil i ty was not statistically signi ficant. Anterior-

postcdor drav/Cr tests were performed at 90 and 30 degrees of

flex jan w i th forces of 90 Newtons. In the same study, three

uni lateral ACL deficient subj ects were tested. The mean

diffcrence (involved minus intact knees) for anterior laxity

\-1i1S only O.G mm with a standard deviation of 4.0 mm. In the

present experiment, at 90 degrees of knee flexion with a force

of 90 Newtons 1 the T'lean difference was 3.64 mm wi th a standard

deviat ion of 1. 75 mm when combininq active and passive

protocols and sessions 1 and 2. These discrepancies in mean

differences may be explained by the larger sample size in the

present experiment.

The findings of the three previous experiments are in

agreement with those of this study. The day-to-day

I"oproducibility of the active and passive protocols on the

Genucom was statistically confirmed by non-significant ANOVA

rcsul ts for the session variable and no interaction of this

variable wi th the type of test or the flexion variables.

Howevcr, for bath samples of ACL and the peL injured

patients evaluated at 60, 90 and 130 Newtons 1 the resul ts for

scss ion 2 were always higher than session 1. Edixhoven et al.

(1987) in measuring test-to-test reproducibility observed a

cycle effect. The authors observed that the first test in a

sCnting was signif icantly smaller than subsequent tests after

! ,1

subj ects were instructed how to control the ir muscular st,1tus.

Wroble et al. (1990), testing on the Genucom, <lnd Riedcnn,ll1 et

al. (1991), testing on the Knee Signature System, ,\1 ~~0

identi fied a "learning effect". In the present expC' t' 1 I11pnt ,

the use of the Biostim 6010 holpcd sub:i cets to re l,lX tilt' i t"

hamstrings and to contract their quadr iceps musc l es. At t C' l'

the initial seating, sub j ects may have loa rned how to con t 1'01

thei"'::' muscular status which may have ùccounteù t 0 t" thl.'

increased laxity scores durlng the second session.

5.5 Levels of Force and Tibia l Dl êQli:tçc'n1çJ1t

Al though not a maj or focus of the present rese,) rch, t hr>

relationship between force application (60, 90 dnd 130

Newtons) and tibial laxity of the pel. and J\CL pdti('nL~

deserves sorne comment. It is important ta note that thes0

findings are limited by the facts that hJO different s,1mple~;

of ACL and peL subj ects were tested and these observat i om:, l'dl1

be applied only to the Genucom system.

Sherman et al. (1987) compared the ueLA device to the K'l'-

1000. In examining 48 normal and 19 ACL-deficient patients,

the ueLA device gave consistently lm-1er absolute disp1 ace-ment

readings than the KT-lOOO at the same displacement force (B~

Newtons). However, when the recommended displacement forcc of

200 Newtons was used for the ueLA apparatus, similôr

displacements were observed. These discrepancies wcrc

attributed to differences in device design. It is important

75

thilt standard procedures be fc·llowed when testing for knee

l ax i ty. In ùddi tian, the levels of force used ta measure

lûxjty should ùlways be reported.

Fukubayashi et al. (1982) observed that at high levels of

force (."ore than 90 Newtons), a greater standard deviation in

the displacements was found in ACL injured patients compared

ta PCL injured patients. This was a Iso observed in the

present experiment and was probably due to a greater

variabi li ty of secondary restraints that control for anterior

tibial displacement. It suggests that when PCL injured

p()ticnts perform active and passive tests, secondary

restrtlints come into play at low levels of force, \:hich does

Ilot occur in ACL inj ured subj ects. In the present study, this

is aIso supported by the fact that posterior laxity of the peL

p()ticnts at 60, 70, 80 and 90 degrees had smaller variability

than anterior laxity of the ACL patients when looking at the

three levels of force. This is illustrated in Figures 1 and

2 (Chapter4).

steiner et al. (1990) tested the anterior-posterior

displacement of the knee of 13 normal and 15 ACL injured

patients on the Genucom. The authors found that the

reproducibility of their measures and their diagnostic

correctness were similar at bath 89 and 133 Newtons of force.

The test variability was smaller at the higher force. This

does not agree with the results of the present study and with

those of Sherman et al. (1987). Forces higher than 89 Newtons

appear to be more appropriate for identi ficùtion of knoc'~-; th,\t

have a rupture of the anterior cruciate J leJLlI1lCnt.

other hand, low levels of force oppear to be s\lrricicnt tew

testing posterior laxity of peL injured subjects.

1

77

.\ CHAPTER VI

Summary, Conclusions and Recommendations

G.l Summary

'rhis cxperimcnt attempted to characterize cruciate knee

deficiencies using the Genucom system with two test starting

positions of the tibia: (1) neutral and (2) resting. A

qUùdr leeps active technique was compared to a passive protocol

ùt four angles of flexion of the knee: 60, 70, 80 and 90

degrees.

Eight ACL and eight PCL injured individuals with ages

rùnging from 16 to 37 years participated as volunteers in this

rcsea rch. For ACL patients, the cri terion for inclusion j n

this study was anterior tibial displacement equal or greater

than ] mm for the involved leg compared to the intact leg when

assessed at 60 degrees of flexion. For PCL patients, the

criterion for inclusion in this study was posterior tibial

displacement equal or greater than 2.5 mm for the involved leg

compared to the intact leg when assessed at 90 degrees of

flexion.

Subjects performed active and passiv~ anterior-posterior

knee drawer tests wi th both the invol ved and intact legs.

These tests were performed during two sessions to verify the

reliability of the procedures. posterior tibial displacement

values (laxity in mm) were measured at knee flexion angles of

60, 70, 80 and 90 degrees for PCL subjects. Anterior tibial

lH

displacement values (laxity in mm) wcrc measured at kncc

flexion angles of 6 0, 70, 80 and 90 degn~ûs for ACT. sub j cd:;.

Laxity .cores were estimated at force values of 60, 90 ~nd 130

Newtons tor both peL and ACL subjects.

A feedback un i t (Biostim 6010) was used to mon i tor

muscular contraction during application of the i1ct ive <1nd

passive protocols. Surface elcctrodes werc ,1ttilched to tlw

hamstr ing muscl es. The feedback un i t tlSS i ~> tell ttH' l'V.! 1 ucll (Il

to select tests \.Jithout contractions of cxtc>rndl mll~~CLlI ,thll ('.

The quadriceps muscles were contracted ùurinrJ tilt' <let iv('

protoeol and relaxed during the passive protoco1 .

Three trj aIs were performed for céleh type oL test, ~:,C':;';i()n

and angle of flexion. Mean di fferenees bet\'/0cn the i nvo 1 vl'd

and intact l eg were used for statist iC2l1 (1 na1 yscs. Ath 1 ("'('

factor ANOVA was performed ta test the hypothescs. '('he·

factors were: (1) type of test (active and passive), (?)

session (1 and 2), and (3) knee flexion angle (60, 70, 80 <1nd

90 degrees).

The first hypothesis stated that posterior knee 1 in: 1 ty

values for peL subjects would be similar [or actl vc dnd

passive tests at 60, 90 and 130 Nevltons. The ANOVA resu]t!;

showed F-ratios of 4.58 for 90 Newtons and 5.88 for 1 JO

Newtons, which were significant at the .03 and .02 lev!? l~;,

respectively. At these levels of force, postcrior laxity wns

significantly greater for active tests as compared ta passive

tests (p<. 05). At 60 Newtons, the ANOVA ShOvlCd an F-rat io of

3.56 (p=.06).

79

The use of a larger sample might also have

elicited significant difference between active and passive

tests at this level of force.

ln the second hypothesis, it was predicted that anterior

knee laxlty val ues for ACL subjects would be similar for

active and passive tests at 60, 90 and 130 Newtons. This was

confirmed by the ANOVA results, which revealed F-ratios of

0.97 (p=.33) for 60 Newtons, 1.19 (p=.28) for 90 Newtons and

].04 (p""'.31) for 130 Newtons.

The third and fourth hypothesis predicted that the values

[or posterior knee laxity of PCL subjects and anterior knee

laxity of ACL subjects would be similar for the two sessions

at 60, 90 and 130 Newtons. For PCL subj eets, the ANOVA

calculated F-ratios of 0.01 (p=.93) for 60 Newtons, 1.03

(p:...-.31) for 90 Newtons and 1.68 (p=.20) for 130 Newtons. For

ACL subjects, the ANOVA calculated F-ratios of 2.75 (p=.10)

[or 60 Newtons, 2.25 (p=.14) for 90 Newtons and 0.01 (p=.95)

for 130 Newtons. Therefore, the active and passive protocols

produced reliable results across two sessions.

The fifth hypothesis stated that the posterior knee laxity

val ues for PCL subjects would be similar for 60, 70, 80 and 90

degrees of knee flexion at 60, 90 and 130 Newtons. This

hypothesis was accepted at the .05 level as the ANOVA results

revealed F-ratios of 0.28 (p=.84) for 60 Newtons, 0.37 (p=.77)

for 90 Newtons and 0.43 (p=.74) for 130 Newtons. For the PCL

subjects, a trend in the data was not observed as illustrated

80

in Figure 2 (Chapter 4).

The sixth hypothesis predicted that antcrior kncC' l<1x i ty

values for ACL subjects would be similar for GO, 70, 80 dlHI ')l)

degrees of knee flexion at 60, 90 and 1 J 0 Newtons. '1'11(' F­

ratios from the ANOVA were 3.25 (p=.08) for 60 Ncwtom" l.')}

(p=.lJ) for 90 Newtons and 1.44 (p=.23) for 130 Nc'wton:-'.

Al though the ANOVA resul ts did not show s ign if LCllnt

differences (p>. 05), a trend in the da té1 ex i stod dnd "-,d',

illustrated in Figure] (Chapter 4). A lùt"gcr Gl1mplf' ::1.'('

might have decreased the variability in antC'rior kncc I<1X i ty

and might have demonstrated significant differenccs LimOn,) the

four levels of knee flexion.

6.2 Conclusions

Considering the limitations and deI imi ttltj ons, th i s ~;hldy

justifies the following conclusions:

1. There was a significant anterior tibia l sh i ft in peL

injured patients when comparing active to passjvc tcstr;

performed from 60 to 90 degrees of knee flexion at forcc~;

ranging from 60 to 130 Newtons on the Genucom Knee Analysi~

System.

, 81

2. Therc was no significant anterior tibial shift in ACL

injured patients when comparing active to passive tests

pcrformed from 60 to 90 degrees of knee flexion at forces

ranging from GO to 130 Newtons on the Genucom Knee Analysis

System.

3. The Genucom Knee Analysis System produced rel iable

rcsults for two sessions when ACL and peL subjects performed

dctlve and pJssive tests at flexion angles of 60, 70, 80 and

00 dcgrees with forces of 60, 90 and 130 Newtons.

4. Posterior knee laxity of PCL injured subjects was

similar for knee flexion angles between 60 and 90 degrees at

levcls of force ranging from 60 to 130 Newtons.

5. Statistically, the resul ts showed that ACL inj ured

subjects had similar anterior knee laxity at flexion angles

between 60 and 90 degrees. However, a trend in the data

suggested that with a larger sample size this hypothesis might

have been rejected.

6.3 Recornrnendations

\' , L'.

The following recommendations can bc proposC'd 10r futul"l'

studies:

]. The effects of a quadriceps contraction on rotùUol1Lll

stability of the knee (cornbined rotation and ùnter iOl'-

posterior drawer) and on other joint flexion angles should b0

investigated.

2. It is suggested that the digi ti zat ion rout i no on t Il,.

Genucom be employed with active and passive protoco ls ta t('~.t-

its sensitivity and specificity to rneasure possible tibictl

shifts during the active protocol.

83

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APPENDIX 1 Informed Consent Form

<)1

PROJECT TITLE: Laxity and the Tibial Neutral position in Cruclate DcficiC'nt KnC'C'~;.

PRII',CIPAL INVESTIGATOR: \vagn~r Cdlio Batista, M.P. Department of Phys 1 cal EcluL',\ t ion MCGlll UniversIty

The above mentioned study is designed to ev,l1ucltt' tW(l protocols, the anterior drawer test with and without- the influence of the quadriceps muscles using the Genucorn system.

Your invol vernent in the study requ ires pa rt ie i pa t j on i 11

two separate but identical testing sess ions w.i th the pr 1 ne i pd 1 investigator. One session will last about :3 0 to ,l'i ml IlU te:;. During the sessions, the investigator will conduct rndnudl nI)!)

invasive clinical tests on your knees usinq the Gf>Illll'O!11 1:11('('

Analysis System. First, nine points, l11cl r}.cd It/ i th ,1 p(·n, VIII 1 be digitized on your skin usinq i1n C'1(·ctroqonl{)Jl1r'tc.!. Electrodes from a bio-feedback un i t w il 1 be dt t,wh('<1 t () t Il!' thigh to monitor the contraction act l vi ty 01 th" mu';, -II",. IJn electrical current or radiation wi Il be employed. {nu 'vI i ] 1 !JI' required to sit on the system's chair ùnd rcLJx yOlll ] ()vJ01

limb muscles while the tests are being donc. II'h('Il, the investigc. tor wi Il ask you to hold your 16g at a spPC l 1 1 (' d nq l '-' for a short period while the tests are applicd and th., I)oint', are digitizcd. You \vill be allowcd to rcst bctlt/(lon :;r",:;I()I)'.

and tests as the achievement of fùt igue l s not i ntî>n<!('r!. '1'1)

restrain thigh movE'luents, thrl"'c c] amps wi Il bl"' lI::,od tl) ':r'f lIr-('

a fixed position. Every effort will be made tu conduct tl1P t,.':.t:: III ',1/1'11 .t

way to minimize an)' di scomfort. A report of the knce cVùluùtion::; vd 11 b(> rH-ovldc,rj t () jOli

and your physic ian. The data coll ccted W l 11 be ~:('pt 111 Oll t­lab without indication of the subject' s namc. You m':ly dl;-;u discontinue your participation in the stucly ilt ùny t 1 me <lnrJ ask to have your resul ts destroyed.

If you understood this consent form clnd c\cccptod tn participate in the proj ect, pleasc s ign below. Jf you hd \l(' any questions about the study you can reach me at ('.;111) ;r,')-3244.

Signature ______________________________ _

Date ______________________________________________ _

witness --------------------------------------------

J

APPENDIX 2

McGill University Department of Physical Education

Biornechanics Laboratory subj ect Information Form

92

Da te ____________________________ Gen de r _______________ _

Name ____________________________________ D.O.B.:rn. ____ ~/d. ____ ~/y

Addres3: ______________________________ ~Height ________________ _

____________ . ________________________ Weight

_____________________________________ Phone:(h) ____________ _

Physician: ____________________________ __ (w) _____ _

Type of Inj ury: LEFT (ACL PCL MCL LCL MM LM other)

RIGHT (ACL PCL MCL LCL MM LM other)

Prey ious Surgeries (describe) : _____________________ _

Mechanism of Injury: ___________________________________ ___

Date of Injury: _________________________________ __

Subsequent Injuries (if yes, describe): __________________ __

----------------------------------------------------------other Comments: ----------------------------------------