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UMEÅ UNIVERSITY MEDICAL DISSERTATIONS
__________________ New series 373 - ISSN 0346-6612__________________
From the Department of Orthopaedics, University of Umeå, Umeå, Sweden
KNEE JOINT LAXITY AND KINEMATICS
AFTER ANTERIOR CRUCIATE LIGAMENT
RUPTURE
Roentgen stereophotogrammetric and clinical evaluation
before and after treatment
Håkan Jonsson
L
Umeå 1993
UMEÅ UNIVERSITY MEDICAL DISSERTATIONS
_______________ New series 373 - ISSN 0346-6612_______________
From the Department of Orthopaedics, University of Umeå, Umeå, Sweden
KNEE JOINT LAXITY AND KINEMATICS AFTER ANTERIOR CRUCIATE
LIGAMENT RUPTURE
Roentgen stereophotogrammetric and clinical evaluation before and after treatment
AKADEMISK AVHANDLING
Som med vederbörligt tillstånd av Rektorsämbetet vid Umeå Universitet för avläggande av
medicine doktorsexamen kommer att offentligen försvaras i sal B , byggnad 1 D
(Tandläkarhögskolan) fredagen den 28 maj 1993
kl 9.00
av
Håkan Jonsson
Umeå 1993
UMEÅ UNIVERSITY MEDICAL DISSERTATIONS
New scries 373 - ISSN 0346-6612
KNEE JOINT LAXITY AND KINEMATICS AFTER ANTERIOR CRUCIATE
LIGAMENT RUPTURE
Roentgen stereophotogrammetric and clinical evaluation before and after treatment
Håkan Jonsson
From the Department of Orthopaedics, University Hospital in Northern Sweden, S-901 85
Umeå, Sweden
Abstract
Rupture of the anterior cruciate ligament (ACL) increases anterior-posterior (AP) laxity. The
treatment aims to reduce or teach the patient to control this instability. Altered kinematics due to
absent ligament function may result in knee arthrosis. This study evaluated the clinical and
functional results of reconstructive surgery. Roentgen stereophotogrammetry (RSA) was used to
analyse the stabilising effect of knee braces, reconstructive surgery and the kinematics of the
knee with and without weight-bearing.
The stability of the knees were assessed in 86 patients with ACL injuries before and/or after
reconstructive surgery with the RSA technique and with the KT-1000 arthrometer The KT1000 (89 N) recorded smaller side to side differences than the RSA set-up without any
correlation between the methods.
The effect of three different braces on the AP and rotatory laxity was studied on patients with
ACL injuries. The ECKO and the modified Lenox Hill reduced the instability with about one
third. The SKB had no significant effect. None of the braces decreased the internal rotatory
laxity but the Lenox Hill reduced the external rotatory laxity.
Thirty-two patients with old ACL tears were treated with surgical reconstruction using the
over the top technique (OTT) with or without augmentation. A small reduction in AP laxity was
observed at the 6 month follow-up, The AP laxity was almost the same two years after as before
surgery. No correlation was observed between the stability and knee function.
Fifty-four patients with old unilateral anterior cruciate ligament injuries were randomised
either to the over the top (OTT) or the isometric femoral tunnel position (ISO) at ACL
reconstructive surgery. Seven of 24 (ISO) and 9 of 25 (OTT) had "normal" laxity two years after
surgery. The patients operated with the ISO technique did not have better subjective knee
function, muscle strength, functional performance or knee stability than patients operated with
the OTT technique.
The knee kinematics in patients with chronic unilateral ACL ruptures were examined during
active extension in the supine position (13 patients) and during extension and weight-bearing
(13 patients). The tibia displaced at an average 1.9 mm more anteriorly and 0.8 mm distally in
the injured than in the intact knees during active extension. During extension and weight­
bearing the tibia was about 2 mm more posteriorly positioned than in the intact knee. The ACL
rupture did not affect tibial rotations.
Conclusions: The RSA recorded larger side to side differences in ACL injured and reconstructed
patients than the KT-1000 arthrometer. Some knee braces are able to reduce AP laxity in ACL
injured knees. No correlation was observed after surgery between knee laxity and functional
scoring or tests. ACL reconstructions with isometric graft position on the femoral side did not
offer any advantages compared to the over the top placement. Altered knee kinematics in the
ACL injured knees were observed during knee extension with and without weight-bearing.
Key words: Anterior cruciate ligament, Kinematics, Anterior-posterior laxity, Surgery,
Roentgen stereophotogrammetric analysis, Muscle strength, Functional tests
UMEÅ UNIVERSITY MEDICAL DISSERTATIONS
_______________ New series 373 - ISSN 0346-6612_______________
From the Department of Orthopaedics, University of Umeå, Umeå, Sweden
KNEE JOINT LAXITY AND KINEMATICS
AFTER ANTERIOR CRUCIATE LIGAMENT
RUPTURE
Roentgen stereophotogrammetric and clinical evaluation
before and after treatment
Håkan Jonsson
UMEÅ 1993
Copyright © 1993 by Håkan Jonsson
ISBN 91-7174-783-4
Printed in Sweden by Solfjädern Offset AB, Umeå
lïla/m, XmAÅ, Mcun/na oeil jJu m
4
KNEE JOINT LAXITY AND KINEMATICS AFTER ANTERIOR CRUCIATE
LIGAMENT RUPTURE
Roentgen stereophotogrammetric and clinical evaluation before and after treatment
Håkan Jonsson
From the Department of Orthopaedics, University Hospital in Northern Sweden, S-901 85
Umeå, Sweden
Abstract
Rupture of the anterior cruciate ligament (ACL) increases anterior-posterior (AP) laxity. The
treatment aims to reduce or teach the patient to control this instability. Altered kinematics due to
absent ligament function may result in knee arthrosis. This study evaluated the clinical and
functional results of reconstructive surgery. Roentgen stereophotogrammetry (RSA) was used to
analyse the stabilising effect of knee braces, reconstructive surgery and the kinematics of the
knee with and without weight-bearing.
The stability of the knees were assessed in 86 patients with ACL injuries before and/or after
reconstructive surgery with the RSA technique and with the KT-1000 arthrometer The KT1000 (89 N) recorded smaller side to side differences than the RSA set-up without any
correlation between the methods.
The effect of three different braces on the AP and rotatory laxity was studied on patients with
ACL injuries. The ECKO and the modified Lenox Hill reduced the instability with about one
third. The SKB had no significant effect. None of the braces decreased the internal rotatory
laxity but the Lenox Hill reduced the external rotatory laxity.
Thirty-two patients with old ACL tears were treated with surgical reconstruction using the
over the top technique (OTT) with or without augmentation. A small reduction in AP laxity was
observed at the 6 month follow-up, The AP laxity was almost the same two years after as before
surgery. No correlation was observed between the stability and knee function.
Fifty-four patients with old unilateral anterior cruciate ligament injuries were randomised
either to the over the top (OTT) or the isometric femoral tunnel position (ISO) at ACL
reconstructive surgery. Seven of 24 (ISO) and 9 of 25 (OTT) had "normal" laxity two years after
surgery. The patients operated with the ISO technique did not have better subjective knee
function, muscle strength, functional performance or knee stability than patients operated with
the OTT technique.
The knee kinematics in patients with chronic unilateral ACL ruptures were examined during
active extension in the supine position (13 patients) and during extension and weight-bearing
(13 patients). The tibia displaced at an average 1.9 mm more anteriorly and 0.8 mm distally in
the injured than in the intact knees during active extension. During extension and weight­
bearing the tibia was about 2 mm more posteriorly positioned than in the intact knee. The ACL
rupture did not affect tibial rotations.
Conclusions: The RSA recorded larger side to side differences in ACL injured and reconstructed
patients than the KT-1000 arthrometer. Some knee braces are able to reduce AP laxity in ACL
injured knees. No correlation was observed after surgery between knee laxity and functional
scoring or tests. ACL reconstructions with isometric graft position on the femoral side did not
offer any advantages compared to the over the top placement. Altered knee kinematics in the
ACL injured knees were observed during knee extension with and without weight-bearing.
Key words: Anterior cruciate ligament, Kinematics, Anterior-posterior laxity, Surgery,
Roentgen stereophotogrammetric analysis, Muscle strength, Functional tests
5
CONTENTS
Abstract
4
Original papers
6
Definitions and abbreviations
7
Introduction
9
Aims of the study
19
Patients and Methods
20
Results
38
Discussion
57
Conclusions
67
Acknowledgements
69
References
70
Appendix
84
Papers I- VI
90
6
This thesis is based upon the following papers, referred in the text by their
Roman numerals:
I. Jonsson H, Kärrholm J, Elmqvist L-G. Knee laxity after cruciate ligament
ipjury. The KT-1000 arthrometer versus Roentgen stereophotogrammetry
in 86 patients. In press. Acta Orthop Scand
II. Jonsson H, Kärrholm J. Brace effects on the unstable knee in 21 cases. A
roentgen stereophotogrammetric comparison of three designs. Acta Orthop
Scand 1990;(61): 313-318.
III. Jonsson H, Elmqvist L-G, Kärrholm J, Fugl-Meyer A. Lengthening of
anterior cruciate ligament graft. Roentgen stereophotogrammetry of 32
cases 2 years after repair. Acta Orthop Scand 1992; 587-592.
IV.
Jonsson H, Elmqvist, L-G, Kärrholm, J, Tegner, Yelverton. Over the top vs.
tunnel technique reconstruction of the anterior cruciate ligament. A
randomised study. Submitted.
V. Jonsson H, Kärrholm J, Elmqvist L-G. Kinematics of active knee extension
after tear of the anterior cruciate ligament. Am J Sports Med 1989;(17): 796802.
VI.
Jonsson, H, Kärrholm J. Three dimensional knee joint movements during
weight-bearing. Evaluation after anterior cruciate ligament rupture.
submitted.
Some complementary data not accounted for in I-VI are included in the results and
discussion.
7
DEFINITIONS AND ABBREVIATIONS
A: Augmented. Anterior cruciate ligament repair augmented with a Kennedy LAD
braid.
ACL: The anterior cruciate ligament
AP laxity: The play in the knee between the anterior and posterior endpoints
achieved by separate anterior and posterior traction.
Functional stability: Knee stability during activities accomplished by passive
restraints (see static stability) and active restraints (muscle activity and joint
load).
Condition number. Mathematical formula used in RSA to objectively express the
scattering of bone markers within a rigid body.
Coordinate system: A Cartesian coordinate system with the three axes in right
angles to each other.
Give way: Episodes of knee instability described by the patients.
Helical axis (screw axis): Axis used to describe three-dimensional movements in
terms of rotations. Movements are defined by the position and direction of this
axis and the size of the rotations. Translations may occur along axis.
Mean error of rigid body fitting. Mathematical formula used to evaluate the
stability of bone markers between two RSA examination.
N: Newton
NA: Non augmented. ACL surgery without synthetic augmentation.
Nm: Newton meter
n.s. Not significant
OTT: Over the top. ACL surgery with the graft placed over the top on the femoral
side.
8
ISO: Isometric. ACL reconstruction using the Stryker drill guide to position the
ACL graft.
Rigid body: A body with three-dimensional extension not deforming during
motion. A rigid body can be defined by a number of landmarks ,e.g., tantalum
markers. These landmarks have a constant distance to each other during the
motion
RSA: Roentgen stereophotogrammetric analysis
SD: Standard deviation. In the text proceeded by ± and in tables within brackets.
Side to side difference: Difference of the anterior-posterior knee joint laxity
between the injured and the normal knees in one patient.
Static stability: The stability in the knee provided by passive restraints such as
ligaments, capsules and other soft tissues.
9
INTRODUCTION
Injuries to the anterior cruciate ligament were first recognised in the middle of the
19:th century (Stark 1850). Braces remained the treatment of choice for many
decades (Hey Groves 1917). In 1919 Harding suggested a supervised increase in
activity after knee sprains. Physiotherapy is still one of the corner stones in the care
of ACL injured patients (Tegner et al. 1986). Surgical procedures were introduced
early this century ( Robson 1903, Hey Groves 1917, Smith 1918). Later, Palmer
(1938) held that early repair of the ligament was the treatment of choice.
O'Donoghue (1950) set the goal of full recovery and believed it could be fulfilled
with surgery. During the following decades reconstructive ACL surgery expanded
resulting in the use of many methods (Burnett and Fowler 1985).
The aim of the therapy is to eliminate or teach the patient to control instability.
The increasing number surgical procedures and treatment modalities have called for
objective evaluation of the results. Clinical examination of knee stability has been
regarded inaccurate (Sylvin 1975, Hooper 1986, Feagin and Blake 1983, Markolf
and Amstutz 1987, Daniel 1991), focusing on the need for objective measurements
of knee stability.
Absence of functioning anterior cruciate ligament leads to changed knee
kinematics (Marans et al. 1989, Berchuk et al. 1990 ) and has been postulated to be
responsible for abnormal joint wear (Palmer 1938, Noyes 1980, Fetto and Marshall
1980 ). In the long term it may lead to osteoarthrosis of the knee (Balkfors 1982,
Kannus and Järvinen 1987, Sherman et al. 1988, McDaniel and Dameron 1983).
One of the major goals with ACL surgery is to restore kinematics (Noyes et al.
1980, Gillquist 1993) and thereby avoid this deteoriation..
Physiotherapy after surgical reconstruction of the ACL is a prerequisite for
successful results (Howe et al. 1991).The postoperative rehabilitation includes
contradictory ambitions. It has to protect the graft and at the same time avoid
secondary adverse effects of immobilisation, obtain preinjury strength, aerobic
fitness, coordination and patient confidence (Curl et al. 1982). Knowledge about the
in vivo kinematics is necessary to be able to understand the long term effects of an
ACL rupture and to create postoperative rehabilitation programs (Shelbourne et al.
1990, Curl et al. 1982).
The roentgen stereophotogrammetric technique used in this thesis enables
detailed three-dimensional determination of skeletal motions in vivo. The method
10
has a potential to increase our knowledge about the effects of anterior cruciate
ligament rupture and its treatment. This thesis was initiated to evaluate kinematics
in the ACL injured knees and the effects of surgical reconstruction and brace
therapy. A comparison was made with the most frequently used knee arthrometer .
Measurement of knee laxity
Loss of function of the anterior cruciate ligament implies mainly increased anterior
- posterior (AP) instability of the knee. Different methods have been developed to
measure the femoro-tibial play in the sagittal plane. Factors related to the
examination technique such as the degree of knee flexion, size and application of
loads, choice of reference position, measurement techniques, choice of coordinate
systems will all influence the results. Variability is also caused by factors related to
the patient.
Degree o f knee flexion. The classic way to assess the integrity of the ACL is to
perform an anterior drawer test with the knee in 90 degrees of flexion. Examination
of the knee close to full extension was described early this century (Jones 1906,
Paessler and Michel 1992), but has not been in general use until Torg et al. (1976)
reintroduced this technique as the Lachman test. Cadaver studies have later
confirmed that the optimum position to reveal sagittal instability due to ACL tear is
at 20-30° of knee flexion (Markolf et al. 1976, Nielsen and Helmig 1985,
Fukubayashi et al. 1982, Sullivan et al. 1984).
Size o f forces applied. The ligaments of the knee are elastic indicating that there is a
non-linear relationship between the forces applied and the recorded displacements.
The stiffness of the knee ligaments increases at larger loads (Markolf et al. 1976,
Edixhoven et al. 1989). Recordings at high loads are preferable to obtain
reproducible data. On the other hand the forces applied should not be
uncomfortable to the patient or harm any reconstructed graft. In the early
postoperative phase the fixation site of the graft provides the least resistance. Some
graft fixations fail with loads of 100 N or less (Robertson et al. 1986, Kurosaka et
al. 1987). In clinical settings external forces between 67 (Daniel et al. 1985A) and
300 N (Jacobsen et al. 1976) have been used.,
The way to apply external loads also has to be considered. Anterior laxity
recordings will change when the same loads are applied at different distances from
11
the knee joint because of changes of the lever arm (Andersson et al. 1990). The
loading time may also have an influence due to time dependent deformation of the
soft tissues.
Choice o f reference position. A reference position or landmark is required to
measure the effects of externally applied forces. Before the anterior traction is
applied, this position can be obtained by repeated posterior pushing until a
reproducible relaxed position is achieved (Daniel et al. 1985A, Sherman et al.
1987). Shino et al. (1987) and Jonsson et al. (1990) repeated the anterior tractions
until the same displacements were recorded. To eliminate uncertainty in the
determination of an unloaded reference position anterior and posterior forces can be
applied and the play between the endpoints measured (Boniface et al. 1989, Wroble
et al. 1990).
The flexed and unloaded position of the knee has been used as the reference in
several radiographic techniques (Kennedy et al. 1971, Jacobsen et al. 1976, Torzilli
et al. 1981, Hooper 1986). One or several distances between anatomic landmarks on
the femur and the tibia are measured on radiographs exposed with the knee in the
unloaded reference position and after the application of anterior forces. The knee
play is then calculated as the increase in distance(s) between these landmarks.
Levén (1977) and McPhee and Frazer (1980) applied anterior and posterior forces
and measured the displacement between the endpoints. Franklin et al 1990, Moyen
et al. 1990 and Stäubli et al 1992 exposed only one radiograph during anterior
traction of the knee. They measured the distance between the posterior margin of
the tibia and the femur on the lateral radiographs.
Technique to record the displacement. The measuring techniques in clinical use
have either been based on externally applied devices or on radiographic techniques.
The external devices have pads, velcro straps or plates applied to the patella or
distal femur and to the tibia. Changes in distance between the appliances at the
patella/femur and the tibia are recorded when installing displacing forces (Sylvin L
E. 1975, Markolf et al. 1978, Johnson et al. 1984, Daniel et al. 1985A, Shino 1987,
Jonsson et al. 1990, Boniface et al. 1989, Edixhoven et al. 1989). Externally applied
computer based systems with four (Riederman et al. 1991) or six degree of freedom
electrogoniometric linkages (Oliver and Coughlin 1987) measure multiplanar
displacements. Radiographic technique using the lateral projection has been used in
numerous studies (Kennedy et al. 1971, Jacobsen et al. 1976, Levén 1977, Torzilli
12
et al.l981, McAfee et al. 1980, Hooper 1986, Moyen et al. 1990, Franklin et al.
1991, Stäubli et al. 1992). More recently three-dimensional assessment of knee
stability with roentgen stereophotogrammetric technique (Selvik 1974) has been
introduced (Kärrholm 1988B, Fridén et al. 1992A).
Choice o f coordinate system and points of measurement. When performing an
anterior or posterior drawer test multiplanar tibial displacements occur. Complete
description of these motions requires measurements with six degrees of freedom
(Grood and Suntay 1983, Kärrholm et al. 1988B). These six components are
rotations about and translation along the three axes of a coordinate system. A
cartesian coordinate system fixed to the tibia is commonly used (Daniel and Biden
1987). Because of the simultaneous rotations around all axes, points in the tibia
display different patterns of motion. Thus, a specific point on the tibia has to be
defined to describe translations in a standardised way.
Externally applied arthrometers such as the KT-1000, the Stryker and devices
described by Sylvin, Shino and Edixhoven record one dimensional displacements
of the tibia. They measure along an axis fixed to the device. The firmness of the
device fixation to the tibia determines the possibilities for tibial rotations relative to
the device during the test. These rotations determine how accurate the
measurements will correspond to anterior-posterior translations according to a
tibial coordinate system. The position of the tibial measuring pad determines the
tibial measuring point.
Conventional radiographic techniques measure displacement on the lateral
projection and the film plane defines the axis of measurements. In most methods,
the lateral and medial femoral and tibial compartments are identified and the
displacements of each compartment are calculated. This procedure gives some
information about tibial external/internal rotation. Levén (1977) reconstructed a
central femoral point based on the contours of the condyles and used the
intercondylar eminence as the tibial reference point.
RSA enables three-dimensional motion analysis in a laboratory coordinate
system. Translations and rotations are related to tibial axes. Accurate alignment of
the tibia in relation to the laboratory coordinate system (Kärrholm et al. 1988,
Fridén et al. 1992) during one of the examinations is important if the true anteriorposterior translations are to be measured. The midpoint between the two tips of the
13
tibial intercondylar eminence has been chosen to represent tibial translations
(Kärrholm et al. 1988, Fridén et al. 1992).
Patient related factors. The weight of the lower leg, the degree of relaxation, the
soft tissue mass and elasticity affect the recordings. The importance of muscle
relaxation was demonstrated by Dahlstedt and Dalén (1989), who found larger
displacements under anaesthesia in both ACL injured and intact knees.
Knee stability and function
The static stability is provided by passive restraints such as ligaments, capsule and
other soft tissues and can be measured by arthrometric techniques. Functional
stability, i.e., during standing or physical activity (Noyes et al. 1980) is also
influenced by active restraints such as muscle activity (Tegner et al. 1986A),
proprioception (Barrett 1991) and joint load (Hsieh and Walker 1976).
Arthrometric tests cannot be expected to fully predict functional stability (Noyes et
al. 1980). A more comprehensive evaluation can be accomplished by rating the
knee disability with subjective scores (Lysholm and Gillquist 1982 ). Subjective
knee function depends on the activity level and has to be considered when
evaluating the outcome based on different scores (Noyes et al. 1984). In 1985
Tegner and Lysholm modified their original score by excluding objective
parameters and described a complimentary scale, the Tegner activity scale. Other
systems evaluate the subjective function and activity level in the same score (Noyes
et al. 1984). Recent desribed scoring systems also include the results of the clinical
examination of the knee (Orthopaedische Arbeitsgruppe Knie form; Müller et al.
1988, International Knee Documentation Committee, IKDC form; Kipnis et al.
1993, Engström 1993).
Treatment of the anterior cruciate ligament injured knee
Braces. Braces can be used according to three principles, prophylactic,
rehabilitative and functional bracing (Millet and Drez 1987). Prophylactic braces
are used in high risk activities to protect the uninjured knee, but its efficacy has
been questioned (Teitz et al. 1987). The rehabilitative braces aim to keep the knee
within a safe range of motion after surgery. Functional braces are designed to
counteract the instability and enable increased level of activity. Numerous studies
14
have evaluated the effect of braces on knee laxity (Cawley et al. 1991). Externally
applied arthrometers have been used in vivo(Beck et al. 1986, Colville et al. 1986,
Mishra et al. 1987, Cook et al. 1989) to measure AP laxity, whereas the rotatory
stability has been difficult to assess. These examinations have been done manually
(Bassett et al. 1983, Colville et al.l986) making the results dependent on the
examiner (Noyes et al. 1991).
Surgery. The surgical options for ACL reconstruction are influenced by the time
between injury and treatment. In the acute situation repair, repair and augmentation
or intraarticular reconstruction can be done. Old ACL ruptures have been operated
with extraarticular compensating or intraarticular reconstructive procedures.
Patients with ACL injuries often suffer from knee instability or a feeling of
"giving way". These problems occur mostly in activities where sudden changes of
the direction of motion is common as in sports, but may also play a role in activities
of daily living. Anterior subluxation of the tibia and especially the lateral tibial
plateau at extension is probably the pathomechanism for the giving way episodes.
This instability can be demonstrated by the pivot shift examination (Galway and
Macintosh, 1980). Extraarticular surgery of the lateral ligaments of the knee aim to
counteract this subluxation. Most procedures described consist of iliotibial band
transfers or tenodesis (Carson Jr 1987). Slocum and Larson ( 1968) used a pes
anserine transfer on the medial side to correct anterio-medial instability. The
extraarticular techniques have been used singly, as combined medial and lateral
procedures (Dahlstedt et al. 1988) or in combination with intraarticular surgery
(Clancy et al. 1982, Bertoia et al. 1985, Zarins and Rowe 1986, Noyes et al.1991).
The extraarticular procedures may not offer the patient sufficient stability
(Dahlstedt et al. 1988) or any additional benefits when combined with intraarticular
surgery (Roth et al. 1987, O'Brien et al. 1991)
Subjective good or excellent results have been reported in more than 80% of
the patients after intraarticular reconstructive surgery (Clancy et al. 1982, Bertoia et
al. 1985, Dahlstedt et al. 1990, Elmqvist et al. 1988, Howe et al. 1991, Squaglione
et al. 1992). The same frequency of normal or close to normal AP laxity has been
recorded in several studies (Yasuda et al. 1992, Shelbourne et al. 1990, Howe et al.
1991). Less satisfactory results on knee stability have also been reported with
failure rates exceeding 20% (O'Brien et al. 1991, Squaglione et al. 1992, Aglietti et
15
al. 1992, Good 1993). Squaglione et al. (1992) obtained better results according to
subjective ratings than objective stability tests.
Graft material. The objective with the intraarticular surgery is to replace the ACL
with a graft. Autografts, tendons and ligaments close to the injured knee are
common substitutes. Allografts, xenografts and synthetic ACL prostheses have also
been utilised.
The autografts do not have any vascular supply when inserted, and they
undergo necrosis, revascularisation and remodelling. During this time they are
weak and at risk for elongation or rupture (Aim et al. 1974, Kennedy et al. 1980,
Arnoczky et al. 1982, McPherson et al. 1985.) In 1980 Kennedy et al. summarised
the experience with autografts as disappointing due to insufficient strength. He
introduced a synthetic braid (Kennedy LAD) to be used as an augmentation
(Kennedy et al. 1980). The rationale for this polypropylene braid was to stressshield the autograft during the period of reduced strength. Initially the LAD was
used with a patellar tendon-quadriceps tendon graft and placed over the top on the
femur (Marshall et al. 1979, Kennedy et al. 1980, Roth et al. 1985). It was wrapped
into and covered by the biological graft. Later on the Kennedy LAD device has
been combined with the semitendinosus tendon (Squaglione et al. 1992), bonepatellar tendon-bone autografts (Field and Barrett 1993) or allografts (Noyes et al.
1992). It has also been used to reinforce acute ACL repairs (Engebretsen et al.
1990).
Intraarticular graft positioning. Correct placement of the graft attachments was
considered important for the outcome of surgery by Palmer (1944) and later
surgeons (Lam 1968, Hewson 1982) have tried to achieve isometric attachment
sites for the graft. Isometry denotes two points, one femoral and one tibial, being
positioned at the same distance from each other throughout the range of motion.
The rationale for isometric positioning is to obtain constant graft tension during
motion.
There are two basic ways to position the graft in the femur, through a tunnel
(Hey Groves 1917) or a route over the proximal/posterior aspect of the lateral
femoral condyle - over the top (OTT, Macintosh 1974). On the tibial side Jones
(1963) placed the graft over the tibial edge, but this technique has been abandoned
in favour of a tunnel position.
16
To obtain the same tension in the graft throughout the range of motion Clancy
et al. (1982) recommended the femoral drill hole to be placed posterio-superiorly
and the tibial one anterio-medially to the original ACL insertions. The margins of
the holes should coincide with the centres of the ACL insertions. In 1982 Hewson
claimed that the femoral insertion of the graft was the single most important factor
influencing the success of surgery. In a cadaver study Hoogland and Hillen (1984)
found the optimum femoral attachment to be situated in the superior/ posterior
aspect of the original insertion and that the placement of the tibial insertion was less
critical. They as well as Penner et al. 1988 and Good (1993) favoured a slightly
anteriorly positioned tibial tunnel. Odensten and Gillquist (1985) observed that the
centres of the original ACL insertions were isometric and that any divergence from
the tibial insertion site had a significant influence on the isometry. Raunest (1991)
and Schützer et al. (1989) confirmed the importance of an anatomic placement of
the attachment sites. Several groups (Hefzy et al. 1989, Sapega et al. 1990, Schützer
et al. 1989,) failed to identify any absolute isometric positions. Arbitrarily Hefzy et
al. (1989) accepted deviations of 2 mm from isometry and found that a narrow area
on the medial side of the lateral condyle was the optimum. The tibial position was
less important than the femoral one. Sapega et al. (1990) observed that the anteriomedial bundle was the most isometric part of the intact ACL and accepted
deviations from isometry up to 3 mm at surgery. Thus, most of these in vitro studies
support either an anatomical placement or a slightly anterior/medial and
superior/posterior placement of the tibial and femur tunnels, respectively.
Although the femoral OTT placement is not isometric and has been
disapproved for anterior cruciate ligament surgery (Hoogland and Hillen 1984,
Odensten and Gillquist 1985, Raunest 1991, Schützer et al. 1989) there are some
arguments for its use. The OTT placement is more forgiving than the isometric one
by avoiding the risk for a disastrous anterior tunnel position (Grood et al. 1986). It
offers a smoother force transmission between graft and bone at the femoral
insertion reducing the risk for graft abrasion (Montgomery et al. 1988). Fleming et
al. (1992) observed less variability of the AP laxity after surgery using the OTT
than the isometric tunnel technique. By making a groove over the top with a depth
of 3-11 mm the isometric position can be approached (Penner et al. 1988, O'Meara
et al. 1992).
As indicated above many authors have recommended a tibial position anterior
to the original insertion site. Recent studies have stressed the risk for notch
17
impingement with a too anterior positioned tibial tunnel (Penner et al. 1988,
Yamamoto et al.l992, Howell et al. 1991,1992, Yaru et al. 1992, Good 1993). To
avoid this impingement Howell et al. (1992) suggested a tunnel placement in the
posterior part of the original ACL insertion.
Knee kinematics
Most information on knee kinematics has been accomplished by in vitro studies
(Blacharski et al. 1975, van Dijk 1983, Grood et al. 1984, Nielsen et al. 1984,
Kurosawa et al. 1985, Nielsen and Helmig 1985, Reubens et al. 1989, More et al.
1993) or two- dimensional in vivo studies (Frankel et al. 1971). Some authors have
examined three-dimensional kinematics with electrogoniometers applied on the
skin (Shiavi et al. 1987, Marans et al. 1989). These devices are subject to errors due
to soft tissues motions (Granberry et al. 1991). Direct skeletal motions during gait
have been studied by inserting pins into the skeleton but to my knowledge not in
ACL injured subjects (Levens et al. 1948, Lafortune and Cannavagh 1984).
To study the knee kinematics the concept of instant center of zero velocity has
been used. It is the intersection of a flexion axis, describing the motion between two
observations, with a parasagittal plane (O'Connor et al. 1990). The instant center
can be calculated according Reulaux (1875, Van Dijk, 1983). Frankel et al. (1971)
observed changes in the pattern of the instant centre during knee motion due to
meniscus pathology. The hypothesised influence of the cruciate ligaments on knee
motion has been explained with a mechanical model, "the four bar linkage"
(Strasser 1917, Kapandji 1970, Huson 1974, Menschik 1974, O'Connor et al.
1990). In this model the instant centre of zero velocity has been located at the
crossing of the cruciate ligaments. During flexion/extension with fixed femur the
intersection of the axis with a central sagittal plane moves along a path called the
femoral centrode. With the knee flexed the axis starts at the femoral insertion of the
anterior cruciate ligament and moves distally, anteriorly and finally proximally
during the extension ending at the insertion of the posterior cruciate ligament at full
extension (Menschik 1974, O'Connor et al. 1990). The disadvantage with the
instant center technique and the four bar linkage model is that they simplify the
kinematics of the knee to motions in one plane. Blacharski et al. (1975) applied the
method of Reulaux in vitro to study the influence of the cruciates on knee motion.
To overcome the restrictions of planar motion the instant center was calculated on
both the medial and lateral side of the knee. They concluded that joint geometry
18
was the major factor determining knee kinematics and the cruciates were of minor
importance.
In another in vitro study Reuben et al. (1989) examined motions of a Steinman
pin drilled through the centre of the two femoral condyles during extension
performed by traction in the quadriceps muscle. Sectioning the ACL resulted in an
anterior displacement of the tibia. Using a six degree of freedom goniometer
Marans et al. (1989) and Shiavi et al.(1987) observed changes in kinematics during
gait and pivoting. In the first study the results were analysed according to a
cartesian coordinate system. In the later one the helical axes were calculated. Both
authors concluded that the absence of the ACL changed the knee kinematics.
Kinematics and physiotherapy after surgery. During the remodelling phase the
biological grafts has to be protected. Immobilisation leads to decreased ligamentous
strength (Noyes et al. 1973), periarticular and intraarticular changes with
arthrofibrosis and degeneration of the cartilage (Akeson et al. 1973, Evans et al.
1960, Finsterbush and Friedman 1975).
In vitro and in vivo studies have shown increased strains in the ACL during
knee extension, isometric quadriceps contractions and squatting ( Arms et al. 1984,
Renström et al. 1986, Beynnon et al. 1992,1993). In vitro measurements (More et
al. 1993) and indirect calculations of shear forces suggest that squatting and
simultaneous isometric quadriceps and hamstring contractions may be safe (Yasuda
and Sasaki 1987A, Ohkoshi et al. 1991). Even maximum isometric quadriceps
contraction might cause less anterior tibial displacement than the Lachman test
(Howell 1990). Despite that the issue of safe rehabilitation is not solved there is a
development towards more aggressive training programs. These protocols
emphasise immediate passive full extension, walking without weight-bearing
restrictions, squatting and stair climbing (Shelbourne and Nitz 1990, Willis et al.
1992).
19
AIMS OF THE STUDY
Measurement of knee laxity
• To compare the RSA set-up with the KT-1000 arthrometer. (I)
• To establish a cut off value for the RSA set-up discriminating injured from
normal patients. (I)
• To investigate the reproducibility for the KT-1000. (I)
Knee stability and function
• To compare achieved knee stability after surgery with subjective and objective
knee function (III, IV)
Treatment of the anterior cruciate ligament injured knee
• To delineate the influence of three different brace designs on AP and rotatory
laxity in ACL injured patients. (II)
• To evaluate changes in AP laxity after over the top ACL surgery during the first
two years after surgery (III)
• To compare over the top and drill guide aided isometric positioning of the
femoral attachment at reconstructive surgery. (IV)
Knee kinematics
• To assess the three-dimensional kinematics of the knee during active extension
in the supine position. (V)
• To assess the three-dimensional kinematics of the knee during extension and
weight-bearing.(VI)
• To reconstruct the helical axes during extension and weight-bearing in the
normal and ACL injured knees using anatomical landmarks including the
femoral insertion point of the ACL (VI)
20
PATIENTS AND METHODS
Patients
142 patients (44 women/ 98 men) with a mean age of 26 years (15-46 ) were
studied. One hundred twenty seven patients were examined with roentgen
stereophotogrammetry. All had their injuries verified at arthroscopy. Ninety-four
patients in the material were operated between 1984 and 1990 with an anterior
cruciate ligament reconstruction and 86 of them were followed during the two
postoperative years (III,VI). Further 16 patients (9 men, 7 women, mean age 22.5
years) with arthroscopically verified unilateral anterior cruciate ligament tears were
included in the reproducibility tests of the KT-1000 arthrometer.
Table 1 The 127 patients in the RSA studies. Most of the patients participated in more than one
study. Ia denotes the patients examined with KT-1000 and RSA. Ib denotes 100 unilateral ACL
injured patients examined with RSA. Study in/TV denotes patients in whom the AP laxity also
was examined the day after surgery. The number of patients, sex (M= male, F=female) and the
mean age are reported. For additional information see the appendix
Study
Patients
n
Sex
M/F
Age
years
Ia
Ib
H
HI
IV
III/IV
V
VI
86
100
20
32
54
8
13
13
57/29
68/32
15/5
29/3
35/19
7/1
11/2
10/3
26
26
26
26
25
23
24
25
Specimens
A cadaver study was performed to enable a reconstruction of the femoral insertion
of the anterior cruciate ligament on the stereoradiographs. Ten specimens (7 men
21
and 3 women) with a mean age of 76 (54-88) years and without degenerative joint
disease were examined.
Surgical technique (I,III,IV)
Ninety-one patients were reconstructed with a graft made of the central strip of
the quadriceps and patellar tendons connected by the prepatellar tissue according to
Marshall et al. (1979). Sixty-six patients had an over the top placement of the graft.
In 20 no augmentation was used (I, III); in 46 a Kennedy LAD braid (Kennedy et
al. 1980, Roth et al. 1985) was inserted (I, III, IV). Twenty-five patients had the
augmented graft placed "isometrically" in bone tunnels (I,IV). Eight operated
patients did not enter study III or IV (see appendix). One did not want to
participate, three did not fulfil the inclusion criterias in study IV, and one was
operated by a surgeon not included in the study at that time. Three patients had
their anterior cruciate ligament reconstructed with a Goretex ® graft (I).
Incision. Surgery was performed with open technique through a lateral or central
skin incision. A notchplasty was made routinely. In the over the top procedure the
tractus iliotibialis was incised proximal to the knee joint. The septum
intramuscularis was detached from the bone to gain access to the posterior joint
capsule.
Grafi preparation. A graft with a length of about 17 cm from the tibial insertion
was prepared. The outer half of the central third of the quadriceps tendon with a
width of 1 cm was harvested. The graft was widened over the patella and ended
with the middle third of the patellar tendon. The insertion at the tibial tuberosity
was left intact.
The patients operated without the LAD augmentation (III) had their grafts
reinforced with two none absorbable (either Ethibond® or Goretex ®) Bunell
sutures. The Kennedy LAD braid used as augmentation was 8 mm wide and 14-16
cm long . The braid was sutured to and wrapped into the biologic graft.
Placement o f fixation points. The tibial tunnel was free hand drilled when the
OTT technique (I,III,IV) was used, aiming at the old anterior cruciate ligament
insertion. A groove was prepared for the graft in the superior part of the lateral
femoral condyle (over the top).
22
To obtain an isometric position of the two tunnels in the ISO group (TV) a drill
guide was used (Figure 1, Stryker, Kalamazoo, MI, USA, Odensten and Gillquist
1986). The guide was introduced with the knee at 90° of flexion. With the aid of
fluoroscopy the tip of the guide was placed at the proximal end of Blumensaats
line. A 2.5 mm guide pin was drilled through the tibia and femur giving the graft a
straight line at 90° of flexion and an intraarticular graft length of about 31 mm at an
angle of 28° in relation to the femoral longitudinal axis (Odensten and Gillquist
1986). The guide pin was overdrilled with a cannulated 8 mm drill. A test
ligament was inserted and changes in distance between the chosen graft fixation
points in both the OTT and ISO group was roughly tested without any isometer.
Changes in distance estimated to be more than 2 mm resulted in redrilling (ISO) or
deepening of the femoral groove (OTT). The bony tunnels were bevelled.
The graft was inserted and manually tensioned. A number of
flexion/extensions were performed before the graft was fixed to the femur at about
30° of flexion. One or two barbed staples were used for the femoral fixation in the
OTT operated patients. Thirty-eight of them had their graft fixated using staples in
belt buckle fashion. Fifteen of the ISO patients had their graft fastened with a screw
and washer. Two barbed staples (belt buckle fashion) were used in nine patients.
Figure 1 The drill guide with the drill inserted
23
Postoperative rehabilitation
The patients operated with the Marshall technique with and without Kennedy LAD in study III had different protocols according to Table 1. All patients in study
IV passed the same postoperative protocol according to table 2.
Table 2 Rehabilitation programs used in study III. Restrictions in range of motion within
brackets.
Time (Postop)
None Augmented
Augmented
Plaster
Brace
(30-60°)
Week >6
Removable splint
(30°-full flexion)
(30°-full flexion)
Week >9
Brace
(30°-full flexion)
Week >13
(15°-full flexion)
Week >14
Full weight bearing
Week >17
(15°-full flexion)
Week >26
Full range of motion
Week >33
Full range of motion.
Week > 52
Full activity allowed
Full activity allowed
24
Table 3 Postoperative rehabilitation protocol used in study IV
Time
Immobilisation
Day : 0-2
Brace fixed at
30° of flexion
Day: 3-7
Brace
30°-full flexion
No weight-bearing
Isometric quadriceps (quad)
and hamstring (ham)
Dynamic quad and ham
Week: 4
Week: 8-9
Muscle training
Brace: 15°-Fuil flexion
Start weight-bearing.
Isokinetic quad/ham
Eccentric hams
water training
Week: 10
biking
Week: 12
Eccentric quad, jumping
Week: 14
Brace: Full Range of motion
Week: 22
Full activity allowed
Increased functional training
Braces
Two custom made (SKB, a modified Lenox Hill) and one ready made brace
(ECKO) were investigated (II) (Figure 2). The SKB was designed for prophylactic
use. The ECKO represents rehabilitative and the modified Lenox Hill functional
bracing.
The SKB brace (LIC, Sweden ) is built up by metal frames, hinged laterally
and medially, and elastic straps proximally. Immobile moulded pads are attached
medially at the knee joint, laterally on the thigh, and anteriorly and laterally on the
calf. Elastic straps around the waist prevent the brace to slip down.
The ECKO (Extension Control Knee Orthosis) brace (Orthomedics USA), is
available in three different sizes, and consists of a thermoplastic hinged frame with
two transverse anterior bars over the thigh and calf. The brace is stabilised to the
knee with proximal and distal straps and popliteal bands.
25
The Lenox Hill brace (Lenox Hill brace shop Inc. USA, Nicholas 1983) has
metal frames hinged medially and laterally, fixed lateral supports proximally and
distally and a mobile medial support. Above and below patella there are adjustable
pads. Strips and an oblique elastic strap provide further stability. The modified
Lenox Hill brace reaches more proximally on the thigh, more distally on the calf
and the contact surfaces against the extremity are larger compared with the original
version (Karlsson and Eghamn 1981).
Figure 2 The braces in the study. From the left the SKB, ECKO and modified Lenox Hill
Roentgen stereophotogrammetric analysis (RSA)
Roentgen stereophotogrammetry is the science of obtaining reliable threedimensional measurements from radiographs. The system that was developed by
Selvik is called roentgen stereophotogrammetric analysis and includes evaluation of
rigid body kinematics (Selvik 1974,1989). The method has been used especially to
record skeletal movements (Van Dijk 1983, Ryd 1986, Snorrason 1990,
26
Ragnarsson 1991, Nilsson 1992). The RSA technique has been modified by
Nyström (1990) and Söderqvist (1990, Kärrholm 1989). Recently examination set­
ups and methodology for the evaluation of knee joint laxity and kinematics has
been developed ( Kärrholm et al. 1988 A, 1988B, 1989, Jonsson et al. 1989, 1993,
Fridén et al. 1992).
The RSA technique includes of 4 steps;
1: Implantation of the tantalum markers
The patients included in this thesis had symptoms of knee instability and uni- or
bilateral chronic anterior cruciate ligament injuries. Surgical reconstructions were
planned in all of them. Before this operation a diagnostic arthroscopy was made
and 4 to 5 tantalum markers (diameter: 0.8 mm) were implanted in the distal
femur and proximal tibia in both knees. The markers were inserted in a cannula
made of stainless steel. The cannulas were drilled percutaneously and by hand into
the bone. The markers were pushed out of the cannula into the bone by a troacar.
Marker positions were controlled with fluoroscopy. The markers were spread out
as much as possible to facilitate identification and optimise accuracy.
2: Radiographic examinations
AP laxity (I,II,III,IV). The stereoradiographic examination was done three weeks
or later after the insertion of the markers. The knee was placed in a Plexiglas cage
(Figure 3, page 29) attached to a frame supplied with cassette holders. Two x-ray
tubes, perpendicular to each other and positioned 1 meter from the film plane, were
used to get simultaneous exposures.
The AP laxity test consisted of four exposures; extended reference position,
flexed reference position at 30° of flexion, anterior and posterior traction.
Extended reference position. All recorded motions were directly or indirectly
related to the extended position of the knee (0° of flexion, supine). To achieve a
standardised orientation of the patient coordinate system the knees were placed
according to the axes defined by the cage. The y - axis of the cage was aligned
with the longitudinal axis of the tibia. On the simultaneously exposed lateral view
the posterior cortex of the tibial condyles projected over each other close to the
central xray beam corresponding to parallellity with the x-axis of the cage. The zaxis being perpendicular to the x and y - axes ran in the anterior-posterior
27
direction. At the following examinations standardised positioning was not a must,
because absolute motions between the double exposures were corrected at the
subsequent evaluation.
Flexed reference position. A tourniquet was applied around the thigh. The
knee was flexed to about 30° The thigh with the tourniquetwas then fixed to a
frame. To minimise the femoral motions the tourniquet was insufflated to 80 mm
Hg at this and the subsequent three exposures. This position defined the starting
position for the anterior and posterior displacement.
Anterior and posterior traction. A sling was placed 7-8 cm distal to the knee
joint and a load of 150 N was used for the anterior traction. This sling was removed
and a second sling, with two cords hanging down on both sides of the radiographic
table, was put around the proximal calf. A weight of 80 N was fastened to each of
the cords, resulting in a posterior force of 80 N (Kärrholm et al 1988B).
Eight patients (III, IV) were examined the day after surgery. Surgery was
performed under epidural anaesthesia. The epidural catheter was left in place for
postoperative pain relief. Half an hour before the examination local anaestheticum
was injected in the catheter. The postoperative brace was removed at the
examination
Rotatory laxity (II). All motions were related to the extended relaxed position of
the knee (0 °).
Internal-external rotation with and without traction. The knee was flexed to
about 20°. The foot was placed in a shoe mounted to an adjustable circular disc
with a central groove at the circumference of the disc. The disc was fastened to a
platform. Two thin cords were fastened to the edge of the disc enabling internal or
external rotation. The foot could be rotated internally or externally by applying
tractions to the cords. The generated torque was calculated at 8 Nm. This
examination was also performed with anterior traction of 150 N.
Active knee extension in the supine position. (Figure 5, page 29) Two film
exchangers were used providing an AP and a lateral view. A reference plate with
tantalum markers was attached to each film exchanger. Prior to the patient
examination the reference plates were radiographed with the reference cage. The
cage was removed and the same position of the film exchangers and roentgen tubes
were maintained throughout the examination. At the subsequent mathematical
28
evaluation data from this examination enabled calculation of the position of the
xray foci and transformation of the cage coordinate system to the patient
examinations. The knee movements were calculated in relation to the extended
reference position (see above).
The patients were examined in the supine position . Before the serial
radiographs were exposed they performed trial extensions. Depending on the most
comfortable speed of extension chosen by the patients the film exchanger rate was
set at either 2 or 4 frames/second. The patients flexed the knee examined as much
as the space between the examination table and the film exchanger allowed and
they were asked to relax . A pair of radiographs were exposed to document this
position. Then the active extension started. Both knees were studied.
Knee extension in the standing position. The patients ascended a platform about
40 cm high which was fastened to a metal frame (Figure 6). Two cassette holders
moveable in the proximal-distal direction and perpendicular to each other were
attached to the frame. The center of the cassette holders were adjusted to the level
of the joint line. Reference plates were fastened to the holders. The film-focus
distance was about one meter. Before the patient examination the calibration cage
was radiographed together with the reference plates.
The patients placed the foot on the platform at about 100 degrees of knee
flexion and were asked to push the foot against the platform corresponding to the
first simultaneous exposures of the two xray tubes. At the subsequent exposures the
patients were examined at increasing amount of extension weight-bearing only on
the leg examined. The patients stopped the motion at each exposure. The
examinations ended at maximum active extension. Five to six pairs of films were
exposed for the injured and the intact knees.
29
Figure 3 (left) The examination set-up for measurements of AP laxity.
Figure 4 (right) The examination set-up for measurements of rotatory instability.
Figure 5 The examination set-up to study active extension in the supine position (left)
Figure 6 The examination set-up to study extension during weight-bearing (right)
30
3: Measurements of stereoradiographs
The images of the patient, reference cage or plate markers were numbered in a
standardised way. On the reference examination the two tips of the tibial
intercondylar eminence were plotted on the two views. These fictive points and the
images of the tantalum markers were digitised on a measuring table originally
designed for aerial photography (Wild Autograph A7 Z, Heerbrugg, Switzerland).
The two-dimensional coordinates were stored in a microcomputer.
4: Mathematical calculations
Between 1984 and 1990 the software was adopted for microcomputers. This
software has been improved by optimising the mathematical calculations and by
adding more functions. In 1990 a comprehensive software package (UMRSA,
UNIKUM, University of Umeå) was completed that has been subjected to further
updatings. In this thesis the following programs in UMRSA were used.
Xiray. This program transforms the film coordinates to the laboratory coordinate
system defined by the cage. The true cage coordinates are stored in the computer.
The three-dimensional coordinates of the patient markers are computed.
Segment motion. This program calculates the absolute movements of each rigid
body (here: distal femoral and proximal tibial markers) relative to a reference
position ( here: the extended reference position or the flexed reference position) .
The movements of one rigid body relative to another can be calculated. The choice
of fixed and moving body segment can be set arbitrarily. In most evaluations the
distal femoral markers were used as fixed segment and the proximal tibial markers
as the moving one. The calculation of rotations is performed in the following order
flexion/extension, internal/external rotation and adduction/abduction.
Point transfer. Transforms fictive points to subsequent examinations provided that
they are placed in a bone segment identified by at least three non-linear markers. In
this thesis the positions corresponding to the two tips of the intercondylar eminence
were transformed to the same location in proceeding examinations by using the
known positions of the tibial bone markers.
Rotate. This program supports defined rotations of the laboratory coordinate
system.
31
Point motion. This program calculates three-dimensional translations of real or
transformed fictive points
Parallel transformation. The origo of the coordinate system can be transform to a
chosen point with known three-dimensional coordinates. This program was used to
transform the origo of the laboratory coordinate system to the calculated position of
the femoral ACL insertion point (VI).
Kinerr, Number correction. An interactive program that detects incorrect marking
on focus 1 (usually the AP view). The maximum tolerated marker instability (mean
error of rigid body fitting, Selvik 1974,1989 ) can be predetermined which means
that poorly defined or loose markers are excluded from the calculations.
Kinerr, Pairing. Corrects erroneous identification of tantalum markers on the two
images of one examination.
Evaluation o f AP laxity (I-IV). Calculation of the AP-laxity included three steps.
The absolute tibial rotation between the extended and flexed unloaded positions
were recorded. These rotations were used to align the laboratory coordinate system
with the tibia in the flexed position (see Rotate above). The second step was to
transform the fictive point corresponding to the two tips of the tibial intercondylar
eminence to the subsequent examinations (point transfer). Finally the mean threedimensional displacements of these points were calculated at anterior and posterior
traction using the flexed and unloaded examination of the knee as starting position.
This thesis only accounts for displacements along the sagittal axis of the tibia
corresponding to the true anterior-posterior translations.
Evaluation o f knee kinematics (V, VI). Translations and rotations were calculated
in relation to the extended reference examination. The tibial rotations
(internal/external, adduction/abduction) and translations (medial/lateral,
proximal/distal, anterior/posterior displacements) were plotted in relation to the
degree of knee extension providing a total amount of 5 diagrams for each knee
examined. In the study of extension during weight-bearing (VI) the tibial markers
were used as moving segment at five of the evaluations. In further one these
markers were fixed at the mathematical computations to record anterior-posterior
translation of a central femoral point. The rotations and translations were
interpolated at intervals of 5° (V) or 20° (VI) of knee extension from the diagrams.
32
Evaluation o f helical axes (VI). The three dimensional positions of the helical axes
(Selvik 1974,1989) were reconstructed between subsequent positions of extension.
The axes were sorted into one of six intervals of knee extension (>80, 80-60, 6040,40-20, 20-0 and <0 degrees) comprising the major part of its range of motion.
To assure correct positioning in relation to anatomical landmarks the origo of the
laboratory coordinate system was adjusted by parallel transformation to the femoral
insertion of the anterior cruciate ligament. The reconstruction of this location was
obtained from a cadaver study (see below). The three dimensional coordinates for
the helical axis intersection with each cardinal plane (frontal, horizontal and
sagittal) were calculated. The angle between the helical and the transverse (x-axis)
axes in the frontal and horizontal planes were computed. Within each interval of
extension the mean values of all paired observations were presented. The mean
position of the axis intersection with a sagittal plane through the femoral insertion
of the anterior cruciate ligament was also calculated at each of the six chosen
intervals of extension.
Accuracy of the RSA examinations
The stability and the scattering of the bone markers were quantified by the
calculation of the mean error of rigid body fitting (Selvik 1974,1989 , Nyström
1990, Söderkvist 1990) and the configuration number of the markers in each bone
segment (Söderkvist 1990, Nyström et al. 1992). The size of the mean error of rigid
body fitting and configuration number in this thesis were in most instances less
than 0.25 mm and 90 .
The reproducibility of the AP (anterior-posterior translation, I-IV) and the
rotatory (rotations about the longitudinal axis, II) laxity has previously been
calculated at 0.8 mm (Kärrholm et al. 1988) and 1.7° (one standard deviation,
Kärrholm et al. 1989).
Three patients had their examination repeated on the intact side during active
extension (V) resulting in 10 paired observations for each rotation and translation.
The standard deviations for internal/external rotation and adduction/abduction
were 1,9° and 0.3° respectively . For the medial/lateral, proximal/distal and
anterior/posterior translations corresponding values were 0.2 ,0.2,0.3 mm.
During extension and weight bearing (VI) a corresponding test of three
patients (injured side, 15 paired observations) revealed standard deviations of 1.1°
33
and 0.3° ( internal/ external rotation, adduction/abduction) and 0.3, 0.8 1.2 mm
(medial/lateral, proximal/distal and anterior/posterior translations).
The direction and position of the helical axis is more sensitive to landmark
measurement errors than the corresponding evaluation of translations along and
rotations about the axes in a coordinate system. To evaluate the reproducibility of
the helical axes a computer simulation was performed (Nilsson 1992) based on the
condition number and the mean error of rigid body fitting. Landmark positions
were sampled from a uniform distribution in the range 0-45 mm resulting in a
mean condition number of 59.5. Landmarks perturbations were sampled with an
unbiased normal distribution causing a mean error of rigid body fitting of 0.09. The
corresponding mean values for mean error and configuration number in study VI
was 0.06 and 84.
The error in helical axis direction decreases with increasing size of the moving
rigid body. For the marker distribution usually available in the knee joint the
direction error is less important than the position error (De Lange et al. 1990). The
position error is determined by the size of the helical axis rotations and translations.
The influence of these two factors were evaluated in two steps with a fixed screw
axis translation of 5 mm at the first computation and a fixed helical axis rotation of
5° in the second one.
The mean positioning error for a screw axis rotations of 5° was calculated at
2 mm (Figure 7). Based on these calculations examinations representing rotations
less than 5° were excluded. A translation along the helical axis of 5 mm revealed a
mean error of 2.5 mm. The maximum translation observed in any of the patients
was 4.3 mm (Figure 8)
34
mean values
max values
40
mean values
max values
35
30
15
25
20
15
10
2
3
6
4
5
rotation angle
8
9
(degrees)
3
6
7
4
5
translation(mm)
8
9
10
Figure 7 (left) Error of helical axis positioning in relation to rotation angle. Helical axis
translation was set at 5 mm. Each point represents 100 computed movements based on mean
error and marker configuration of 0.09 and 60.
Figure 8 (right) Error of helical axis positioning (mm) in relation to helical axis translation
(mm) with a fixed screw axis rotation at 5°. See also legend to figure 7.
Cadaver study (VI)
The relative femoral ACL insertion was determined in 10 specimen. The knee joint
was approached trough a medial arthrotomy. The anterior cruciate ligament was
removed. Tantalum markers were placed centrally and at the anterior and posterior
edges of the femoral insertion of the ligament. The wound was sutured. The knee
was placed inside the calibration cage and a pair of radiographs was exposed with
the knee in 0 degrees of extension. The knee was aligned to the cage coordinate
system in the same way as the reference position in the patient study.
The joint line was marked on the AP radiographs (A) (Figure 9). Further one
line parallel to the first one was drawn at the level of the medial epicondyle (B). A
box was created by two more lines (C, D) perpendicular to lines A and B and
tangential to the medial and lateral borders of the condyles. The projections of the
center of the femoral ligamentous insertion (a) on lines B and C were identified to
calculate the quotients E/B and F/C. On the lateral radiographs a transverse line (G)
35
joining the most distant points on the anterior and posterior contours of the femoral
condyles and one line along the Blumensaats line (H) were drawn. The projections
of the center of the ligamentous insertion were identified enabling the calculation of
the ratios J/H and I/G.
D
Figure 9: The quotients measured in the cadaver study to reconstruct the femoral insertion of
the anterior cruciate ligament (a). * denotes the reconstructed center of the femoral condyles .
Radiographic measurements of tunnel positions
The tunnel positions were measured on the frontal and lateral radiographs of the
extended knee two years after surgery (IV). The two year observation was chosen
because the sclerotic margins of the tunnels could be most easily observed at that
time. Achievement of full knee extension also enabled a standardised radiographic
examination in that position. A digitising table (Ortho-Graphics Inc.TM)
connected to a personal computer was used for these measurements and
corresponded to conventional radiographic measurements.
36
In patients operated with isometric graft positioning (IV) the femoral tunnel
entrance was measured on the lateral radiographs as the midpoint between its
sclerotic margins intersecting the Blumensaats line. In the OTT group (IV) these
measurements could not be done because of absent bony definition. The relative
tibial tunnel position was calculated in both groups (Figure 1). The locations of the
tibial and femoral tunnel midpoints were compared with the normal insertions of
the anterior cruciate ligament as evaluated on radiographs of cadavers (VI).
KT 1000 (I)
Both knees were placed on a thigh support and a footrest providing an estimated
knee flexion of 30± 5° The arthrometer was fixed to the tibia with two velcro
straps. Firm pressure was placed on the patellar pad by one hand. Anterior traction
with 89 N was applied. The reference position was achieved by repeated posterior
loads of 89 N until a reproducible unloaded position was obtained (within 0.5 mm
on the dial). Repeated anterior tractions were performed until a constant reading on
the dial was recorded. All tests were performed by the same examiner.
To evaluate the reproducibility of the KT-1000 measurements sixteen patients
were tested twice in a random order. The examination table was divided by a screen
and the examiner could only see the lower legs.
Functional tests(HI,IV)
Isokinetic muscle strength. The peak isokinetic muscle strength performance of
(S)
the quadriceps was measured with a Cybex II dynamometer (Lumex, Inc New
York) with the angular velocities set at 30° and 180°/ second. The dynamometers
were calibrated by applying known loads to the lever arms, and differences between
measurements never exceeded 2 Nm. In Umeå the patients were examined in the
supine position with the hips flexed about 20°. The examination started with the
normal leg at the highest velocity. The patient performed repeated extensions until
no further increase in strength was noted. The peak values were selected and the
injured/normal ratios calculated. In Boden the patients sat and performed three
extensions with an interval of 10 seconds. The peak value was recorded.
Figure o f 8 run. The patients ran in a figure of 8 track ( Tegner et al. 1986B). They
ran the track 3 times and rested one minute. This procedure was repeated three
37
times. The running times for the 2:nd to 5:th curves were added and the mean
values calculated. The absolute running times were compared to a normal material
(Elmqvist et al.1988 ) previously examined in the same track (III). Patients operated
in Boden and Umeå ran on different tracks(TV). The absolute values for the turn
times were not comparable. Therefore the relative improvement in running time
was calculated [Preop running time- 2 years postop running time/ preop running
time].
One leg hop. The patients started to jump with the normal leg and jumped three
times with each leg. The hands were placed on the back. The mean (III) or peak
(TV) values were used to calculate the injured/intact ratio. (Tegner et al. 1986B)
Functional and activity scoring. Lysholm score and Tegner activity scales were
used to estimate the subjective function and activity level before and after surgery .
The first 11 patients in study III were preoperatively evaluated according to the
original Lysholm score (Lysholm and Gillquist 1982) whereas all other evaluations
were done according to the modified score (Tegner and Lysholm 1985).
Preoperatively the patients were evaluated by the surgeons. In study III the two year
examinations made by myself were used at the statistical calculations. In study IV
all patients operated in Umeå were evaluated by me and those operated in Boden by
the surgeon (YT).
STATISTICS
The statistical methods used are accounted for separately for each study in the
results. For continuous variables the mean values and standard deviations are
given. For the Lysholm and Tegner scores the median values and ranges are given.
P-values less than 0.05 were regarded as significant.
38
SUMMARY OF PAPERS I-VI AND RESULTS
I.
Knee laxity after cruciate ligament injury. The KT-1000 arthrometer
versus roentgen stereophotogrammetry in 86 patients.
Patients and methods
Thirty-nine patients with unilateral chronic anterior cruciate ligament tears and 55
patients that had been surgically reconstructed were studied. Eight of these patients
were assessed both before and after surgery. The examinations were performed on
the same day except for the RSA measurements of the intact knees in the operated
patients. They were radiographed once prior to surgery. In addition, the AP laxity
was investigated in 100 consecutive patients with an unilateral ACL tear to
determine the side to side difference injured-intact knees. The reproducibility of the
KT-1000 was tested in 16 patients with unilateral old tear of the ACL.
Student's paired T-test, Chi2 test and Pearsons correlation coefficients were used
at the statistical evaluation.
Results
In normal knees, the KT-1000 recorded about the same mean displacement as the
RSA (5.9 and 5.5 mm respectively, r2= 0.3, pcO.OOl). In the injured knees the KT1000 measured smaller laxity values than the RSA (10.5 and 12.8 mm respectively)
without any correlation. Smaller displacements were also recorded with the KT1000 in the ligament reconstructed knees ( 7.5 and 9.5 mm respectively, r2=0.2
,p<0.01). The side to side difference before and after surgery revealed 2.8 and 2.4
mm smaller values when evaluated with the arthrometer. No correlation between the
methods was observed (Figure 10 and 11).
The 100 unilateral ACL injured patients had an AP laxity of 5.3±2.1 mm in the
normal knees and 12.8±3.8 mm in the injured knees with the RSA set-up. Cut off
values of 2, 2.5 or 3 mm for the side to side difference corresponded to a sensitivity
of 98%, 97% and 93% respectively in diagnosing ACL injuries..
A side to side difference of 3 mm for the KT-1000 and 2.5 mm for the RSA
set-up was used to discriminate injured from normal knees. Fewer patients were
39
classified as ACL injured with the KT-1000 (28 patients, 72% ) than with the RSA
set-up (38 patients, 97%, KT-1000 vs. RSA p<0.01). More patients had their
sagittal laxity reduced to "normal" according to the KT-1000 (35 patients, 64%;
cut-off value of 2.5 mm: 33 patients 60%) than with the RSA set-up (16 patients,
29%, KT-1000 vs. RSA p<0.01).
The mean differences ( first and second examination) and standard deviations in
the reproducibility test of the KT-1000 were,-0.2 ± 1.1, -0.7±1.6 and 0.5± 1.5 mm
for normal knees, injured knees and the side to side difference.
KT-1000 mm
.15 r
KT-1000 mm
15 r
•
•
12
12
9
9
•
• •
6-
•• •
»
••
• • •
•
•
•
6
.
•
•
3 -------------- r -------- ;----------- *“
o -
•
•
3
-
0
•
-3
-3
-3
0
3
6
RSA mm
9
12
15
-3
0
3
6
RSA mm
9
12
15
Figure 10,11 KT-1000 vs. RSA side to side knee difference in the ACL injured (left) and in the
ACL reconstructed patients (right)
Conclusions
The KT-1000 measured smaller translations than RSA in injured and operated but
not in normal knees resulting in smaller side to side differences. This arthrometer
overrates the stabilising effect of reconstructive surgery using 89 N anterior traction
compared to the RSA (150/ 80N force). A threshold value for the side to side
difference with the RSA set-up separating about 95% of the ACL injured from
normal patients would be about 2.5 mm. The reproducibility for the KT-1000
40
corresponded to values previously reported in the literature.
ü.
Brace effects on the unstable knee in 21 cases. A roentgen stereophotogrammetric comparison of three designs.
Patients and methods
Each of the three brace designs ( SKB, ECKO and the modified Lenox-Hill)
examined, were tested on seven ACL injured knees. Nineteen patients with unilateral
and one with bilateral chronic ACL injuries were included in the study. The
contralateral intact knees were also examined (SKB: n=7, Lenox Hill and ECKO
n=6 for each). The AP displacement, rotatory laxity with and without anterior
traction was examined. Both the intact and injured knees were evaluated.
Student's t-test was used.
Results
The injured knees displayed an increase in AP laxity. The ECKO and the Lenox Hill
braces reduced the AP instability in the injured knees with about one third but not to
normal levels (Figure 12, Table 4). External or internal rotatory laxity did not differ
between ACL injured and normal knees. None of the braces influenced the internal
rotatory laxity (Table A -l, appendix). Only the Lenox Hill brace reduced the
external rotation (Table A-2, appendix). At simultaneous anterior traction less
external rotation (1.4°) was observed in the injured than in the normal knees (10.3°),
(Table A-4, appendix). When analysing all three brace designs together they
increased the external rotation (4.1°) but not to normal levels. Separately, none of the
designs affected external rotatory laxity at simultaneous anterior traction. The
internal rotatory laxity during concomitant anterior traction was about the same in
the injured, normal and braced knees (Table A-3, appendix).
Conclusion
The modified Lenox Hill and the ECKO designs reduced AP laxity but not to normal
levels. The braces had no or minimum effect on tibial rotations.
41
Table 4 AP Laxity in normal, injured
and braced knees
AP Laxity Difference
mm(SD)
All cases
N-I
-8.9
Normal (N)
5.4 (2.1)
4.8
I-IB
14.6 (3.9)
Injured (I)
N-IB -4.2
Braced (B)
9.8 (3.1)
SKB
N-I
-10.6
Normal (N)
4.2 (1.4)
Injured (I)
14.8 (4.3)
I-IB
N-IB -5.9
Injured-braced (IB) 10.1 (4.6)
ECKO
-5.9
Normal (N)
5.8 (2.6)
N-I
3.8
I-IB
Injured (I)
12.3 (3.9)
Injured-braced (IB) 8.5 (2.3)
N-IB -2.3
Lenox Hill
Normal (N)
6.4 (1.6)
-9.9
N-I
16.7 (2.2)
I-IB
6
Injured (I)
Injured-braced (IB) 10.7 (1.8)
N-IB -4.3
p-value
<0.005
<0.005
<0.005
<0.005
<0.02
<0.005
<0.01
<0.03
<0.005
<0.005
<0.02
Laxity without orthosis
mm
Difference
25
20
5
10
20 mm
15
Laxity with orthosis
Figure 12 Plotting of the AP laxity with (x-axis) and without brace (y-axis). Diagonal lines
represents the difference with and without brace. O =SKB, □ = ECKO, A =Lenox Hill
42
m . Lengthening of anterior cruciate ligament graft. Roentgen stereophotogrammetry of 32 cases 2 years after repair
Patients and methods
Thirty-two consecutive patients with old ACL tears were operated on using the over
the top technique. The first 19 patients had no augmentation (the NA group, Marshall
et al. 1979). The following 13 patients had their grafts augmented with a
polypropylene braid The AP laxity was measured preoperatively, at 6, 12 and 24
months after surgery with RSA. The first 7 patients in the non augmented group were
examined only with anterior traction at the preoperative examination. At the two• year follow-up subjective knee function and activity levels were recorded. The
muscle strength and functional performance were also examined.
Quantitative continuous variables in the total material were analysed with
Student's t-test and Pearsons coefficient of correlation. For sub-materials and
qualitative variables the sign test and Spearmanns rank correlation coefficient were
used.
Results
AP laxity. Six months after surgery the AP displacements were reduced with 5.4 mm
(p<0.05) in the NA group (Figure 13), but it was still 2,4 mm larger than on the
intact side. Eight of the 12 patients had their laxity returned within normal levels (
side to side difference< 2.5 mm). During the following 18 months the AP laxity
increased and at two years only two patients had a side difference of less than 2.5
mm.
Six months after surgery the A group (Figure 14) had less AP laxity (1.9 mm,
p<0.01).Only one patient had a laxity within normal limits. At two years the AP
laxity had returned to the preoperative level without any patients having normal side
difference.
Functional scores and tests. The Lysholm score and Tegner activity level improved
in both the non augmented and augmented groups. According to Lysholm 28 of the
32 had reached a level regarded as good or excellent (a 84). The injured knees had
0.82 to 0.89 of the intact knee muscle strength depending on the angular velocity at
the examination. Using a ratio of 0.9 (Tegner et al. 1986A) or more as the goal for
43
the rehabilitation 16/32 reached that level at the fastest and 7/32 at the slowest
angular speed. Patients with high activity levels (a6) had greater muscle strength
(1807s, injured/intact : 0.94) than patients with lower activity levels (<6: 1807s,
injured/intact 0.81, p<0.05).
Both groups had longer turn times compared with a normal reference group
(Elmqvist et al. 1988). Fifteen of the 32 patients had a turn time within +2 standard
deviations of the reference population. The mean value of one leg hop quotient was
0.92. Twenty-five of the patients had a quotient being within 2 standard deviations
of the reference group. There were no correlation between the translations recorded
at the laxity tests (difference injured-normal) and function score, activity level,
performance, or muscle strength.
Anterior-posterior
Laxity
Anterior-Posterior
Laxity
15
15
10
v
■
\
iii
ii
i
0p
10
E
R
6
Preop
12
Postop
24 Months
6
Preop
12
Postop
24 Months
Figure 13,14 AP laxity in the Non augmented group (NA) (left) and the Augmented group
(A) (right). Triangles in the lower left comers of the diagrams denote the intact contralateral knees
44
Difference in laxity
(o p erated -n o rm al knee)
mm
poor
fair
g o o d /e x c e lle n t
A
Difference in laxity
(o p erated-norm al knee)
mm
A
0
A0
AA
c
A Uà
o o
A A
 A
A
0
o
0
0
50
-
65
0
84
100
Lysholm
Score
Figure 14, 15, 16 Scattergram of the
Figure of 8 running
Turn time
Difference in laxity
(o p erated-norm al knee)
mm
side to side difference, injured-intact
knees and the Lysholm score (left
above), turn time (right above) and
isokinetic muscle strength
O = NA group, A= A group.
X
(right).
and +2sd denote the mean value and
2 standard deviations for a normal
population (Elmqvist et al. 1988).
A
A
c
A
A
a
o o
* * * o.
1.00
Isokinetic muscle strength
(operated-norm al)
45
Conclusions
Two thirds of the patients with non-augmented and one patient with augmented
repair had AP laxity within normal limits 6 months after surgery. An increasing AP
laxity was noted six to twenty-four months postoperatively, suggesting
inappropriate graft strength after the early remodelling and rehabilitation phase. Two
years after surgery no correlation was observed between the laxity (side difference)
and subjective or objective functional evaluations. Other factors than static stability
may influence the subjectively evaluated knee function and functional performance.
IV. Over the top vs. tunnel technique reconstruction of the anterior cruciate
ligament. A prospective randomised study.
Patients and methods
Fifty-four patients with chronic ACL rupture were operated on with patellarquadriceps tendon graft augmented with a polypropylene braid (Kennedy-LAD).
The femoral placement of the graft was randomised to either a modified over the top
(OTT) or a tunnel position obtained by an isometric drill guide (ISO). Four patients
could not participate in a the standardised postoperative rehabilitation program
because of additional surgical procedures leaving 24 in the ISO and 26 in the OTT
group to be evaluated. The AP laxity was measured with RSA preoperatively and
after 6, 12, and 24 months. Subjective evaluation of knee function, activity level,
muscle strength tests and functional tests were done preoperatively and at the 2-year
follow-up. The relative tibial (both groups) and femoral (ISO group) tunnel
positions were measured on the RSA radiographs.
To decrease the number of statistical tests the Hotellings T2 test was used to
evaluate continuos variables preoperatively and at 2 years (AP laxity, muscle
strength, one leg jump, turn time ratio, age, duration, tunnel position). Complete
follow up data was necessary to be included in this test. If a significance was
observed separate analysis of the variables included in the test was performed with a
univariate F- test. Pearson's coefficient of correlation was also used. The non
continuos quantitative (subjective) and qualitative variables were evaluated with the
Wilcoxon rank sum and the chi^ test. Changes within the groups (preoperative - 2
years) were evaluated with the paired Student's t test or Wilcoxon signed rank test.
46
Results
No difference was observed between the ISO or OTT group regarding AP-laxity,
muscle strength, one leg hop, improvement in turn time or activity level two years
after surgery. The OTT group had a higher Lysholm score than the ISO group
(p<0.04, Table 5). The AP laxity was reduced in both groups at 6 months. No
increase in laxity was observed in either of the groups during the following 18
months.(Figure 17).
Tunnel position. The tibial tunnel position in anterior-posterior direction slightly
influenced ( R~=0.11, p<0.05 ) the improvement in laxity, i.e., an anterior position
revealed less improvement. In the ISO group the femoral and tibial tunnel positions
on the lateral view were anterior to the anatomical insertion center of the ACL in
relation to data from a cadaver study. No correlation was observed between the
femoral position and the improvement in laxity.
20
AP laxity ( mm )
15
Ck
10
5
o
I
Ï
OTT
normal
preop
6
12
24
Months
Figure 17 Changes of mean AP laxity for the ISO (triangle) and OTT (square) during follow-up.
The AP laxity of the contralateral intact knees to the lower left.
47
Table 5 Pivot shift and subjective scores and functional tests. 30°/s, 1807s indicate isokinetic
muscle strength. a: Ratio injured/intact knee ^ Improvement in turn time: (Preop time-Postop
time/ preop time). Median (range) and mean (SD) values are reported.
Pivot shift -/+
Lysholm
Tegner
307s
1807s
One leg Hop0
Fig 8 run b
OTT
2-years
n=25
ISO
2-years
n=22
16/9
90 (56-100)
7 (0-9)
0.87 (0.2)
0.91 (0.1)
0.94 (0.1)
0.06 (0.1)
17/5
81.5 (34-100)
6 (0-10)
0.83 (0.1)
0.86 (0.1)
0.86 (0.1)
0.07 (0.2)
Function and stability. No correlation was observed between functional scores, tests,
muscle strength and the side to side difference at two years except for the Tegner
score ( R2=0.1). Separating the patients into stable and unstable showed that the
stability affected knee function. (Table 6)
Table 6 Stability and function.a indicate the p-value for the Hotellings T2 test for the continuos
variables (muscle strength and one leg jump). Median (range) and mean (SD) are given.
Lysbolm
Tegner
307s
1807s
One leg hop
AP laxity
Difference operated-intact
<2.5 mm
ä2.5 mm
P
n=16
n=31
0.08“
Negative
n=33
Positive
n=14
0.03e1
85
7
92
93
0.9
90
7
89
91
0.9
81
6
76
83
0.8
n.s
n.s
0.009
0.05
0.02
(56-100)
(4-10)
(18)
(12)
(0.1)
86
6
82
86
0.9
(34-100)
(0-9)
(12)
(12)
(0.1)
n.s
0.04
0.05
0.02
n.s
Pivot Shift
(58-100)
(3-10)
(14)
(10)
(0.1)
(34-100)
(0-8)
(13)
(14)
(0.1)
P
Conclusions
Both the OTT and the ISO group displayed decreased AP laxity 6 months after
surgery without any difference. No increase in laxity was observed during the
48
following 18 months. Less than one third of the patients displayed values within
normal limits two years after surgery. Despite the isometric drill guide the femoral
and tibial tunnels were positioned too far anterior. The theoretical advantages of
using the drill guide aiming for an isometric graft placement could not be verified.
Patients with AP laxity within normal limits displayed better functional outcome.
m+IV. Postoperative examination of AP laxity
Patients and Methods
The AP laxity was measured the day after surgical reconstruction, after 3, 6, 12 and
24 months in eight patients. Seven patients were operated with the OTT and one with
the ISO technique. Patients operated under epidural anaesthesia and the catheter left
in place for the postoperative analgesia were asked to participate. Two patients from
study III and six patients from study IV agreed. The postoperative brace was
removed during the examination.
Results
The day after surgery the mean side difference (operated-intact knee) was close to
normal (1.7±3.6 mm). An increase in laxity was observed during the first three
months but not thereafter. Individual analysis displayed an improvement for all
patients. Two patients seemed to be too tight (side difference <-2.5 mm), two had
AP laxity within normal limits and four had the side difference reduced without
reaching normal limits (Figure 18,19)
Conclusions
Surgery reduced AP laxity in all patients but were within "normal" in only two of
them. The laxity increased during the first three months of the rehabilitation period.
49
15
Differnce in AP laxity
(operated-normal knee)
12.5
25
Difference in AP Laxity (operated-normal knee)
20
10
15
7.5
10
2.5
5
0
-2.5
Preop postop
3
Months
12
24
■5
PREOP POSTOP
3
Months
6
12
24
Figure 18,19 The eight patients examined the day after surgery. To the left the mean values and
standard deviations. To the right the individual values. Seven patients were operated with the OTT
and one (open square) with the ISO technique.
V.
Kinematics of active knee extension after tear of the anterior cruciate
ligament.
Thirteen patients with unilateral ACL injuries were examined during active extension
of the knee with a load of 30 N at the ankle.
At the statistical calculations Student's t-test were used. Only paired observations
were evaluated. To compensate for unequal number of measurements from different
patients the mean differences (intact-injured) were computed throughout the range
of extension in each patient and thereafter in the total material. Thus each patient
constituted one observation. When a difference was found further calculations were
performed to evaluate if these variations were unevenly distributed between the
50
separate intervals of 5° of extension.
Results
Rotations: (Figure 20, 21). In the starting position at about 30° of flexion the tibia
had an internally rotated and an adducted position. Extension was associated with
external rotation and abduction without any significant difference between the two
sides.
NUM BER OF
M IRED
OBSERVATIONS
6
I
II
\l
9
I
3
I
15*-
- INTACT KNEES
- - - - - - - - - - - - - INJURED KNEES
,i
INTACT KNEES
INJUREO KNEES
Figure 20 (left) Tibial rotations about the longitudinal axis (intemal-extemal rotation) during
active extension. Numbers of paired observations for each 5° interval of extension at the top.
Figure 21 (right) Tibial rotations about the sagittal axis (adduction-abduction).
Translations. (Figure 22, 23, 24) During extension the tibial intercondylar eminence
displaced laterally, distally and anteriorly. The amount of lateral translation was
51
about the same on the two sides. The distal translation was more pronounced in the
injured knees (0.8 mm, pcO.OOl). Separate analysis at each 5° interval of extension
revealed an average increase of 1.9 mm at the beginning of the extension. The
difference decreased with proceeding extension and disappeared at 5°. Increased
anterior translation (mean 1.9 mm, p<0.05) was recorded on the injured side.
Separate analyses revealed significant differences(p<0.01) only at 10° and 15° of
knee flexion.
Conclusions
Absence of the anterior cruciate ligament was associated with increased anterior and
distal displacements of the tibial intercondylar eminence. Close to full extension the
tibial movements normalised.
4
- M t t î KNEES
4
-
- - - - - - - - - - - - - INJMEO KNEES
-
m\K C I KNEES
- - - - - - - - - - - - - - INJUNEO KNEES
Figure 22 (left ) Translations of the tibial intercondylar eminence along the transverse axis
(medialiy-iaterally)
Figure 23 ( right ) Translations of the tibial intercondylar eminence along the longitudinal axis
(proximally-distally).
52
POSTERIOR
• EXTENSION
-IN T A C T K N E E S - - - - - - - - - - - - - - - INJURED KNEES
Figure 24 Translations of the tibial intercondylar eminence along the sagittal axis (anteriorposterior) during active knee extension.
VI.
Three dimensional knee joint movements during weight-bearing
The kinematics of the knee was studied in thirteen patients with chronic unilateral
anterior cruciate ligament injuries during weight-bearing.
For the statistical analysis a three factor ANOVA was applied. The patient was
considered as random factor, the condition of the knee (healthy vs. injured) and the
degree of flexion as fixed factors. Only paired observations were analysed.
Results
Rotations. From an internally rotated position the tibia rotated externally (screw
home mechanism) without any difference between injured and the intact knees
(Figure 25). There were almost no rotations about the sagittal axis (Figure 26).
53
Translations. From a medial (Figure 27) and proximal position (Figure 28) the tibial
intercondylar eminence translated laterally and distally during the extension (injured
vs. intact, n.s.). The tibial intercondylar eminence in the injured knee was up to 2.1
mm (mean value at 60° of flexion) more posterior displaced during the extension
(p<0.05; Figure 29).
Helical axes. At the beginning of the extension the helical axes were positioned
within or close to the femoral insertion of the anterior cruciate on both sides (Figure
30, 31). The mean axis was positioned distal to (all intervals) and in front of the
center of the ligamentous insertion (past 80 degrees of extension). During the
progress of the extension the inclination of the axis increased in the frontal plane
from 1.2° to 20-26.6° close to full extension corresponding to distal displacement of
the axis in the lateral condyle and proximal displacement in the medial one.
In the horizontal plane the mean axes on the intact side were almost parallel to the
transverse axis of the coordinate system at 80 and 60 degrees of knee flexion.
Between 60 and 0 degrees the inclination increased on the intact side corresponding
to anterior displacement of the axis inside the medial condyle. On the injured side a
corresponding obliquity was observed from the beginning of the extension. Both
sides displayed a more transverse course at hyperextension.
Conclusions
In knees with absent anterior cruciate ligament the intercondylar eminence had a
more posterior position during the extension. This may indicate compensatory
muscular mechanisms. At the beginning of the extension the helical axes were close
to the femoral insertion of the ACL and parallel to the joint line indicating some
influence of the ligament for the tracking of knee motion or that the circular center of
the posterior femoral condyle coincides with the insertion site. From this position the
axes moved anteriorly and distally on the lateral side suggesting more translatory
movements in the medial compartment. The changes in the three dimensional
positions of the helical axes imply that limited conclusions can be drawn about knee
kinematics based on two dimensional evaluations.
54
Internal Rotation
(degrees)
Norm al
Extension (degrees)
100
Num ber paired observations
10
13
13
13
12
6
Figure 25 Tibial rotation about the longitudinal axis (internal-external rotation) in the noimal
and injured knees. Number of paired observations for each degree of flexion at the bottom.
Adduction
^degrees)
Injured
Normal
Extension (degrees)
Figure 26 Rotation about the sagittal axis (adduction-abduction).
55
Proximal translation
(mm)
Medial translation
(mm)
Injured
Injure<
Normal
Normal
ion
100
Extension (degrees)
Extension (degrees)
Anterior translation
(mm)
Figure 27 (left above) Translation of
the two tips of the tibial intercondylar
eminentia along the transverse axis
(medial-lateral).
Figure
28
(right
above)
Tibial
translation along the longitudinal axis
-10
-15
(proximal-distal).
Normal
-20
-25
Injured
Figure 29 (right) Translation along the
sagittal axis (anterior-posterior).
-30
100
Extension (degrees)
56
n o r m a l
in ju r e d
mm
■I
L
•0
■>bo: i
2- 80- 603 60- 40“
j
0"
L
Figure 30 Mean positions of helical axes and angles relative the transverse axis in the frontal and
horizontal planes. The origo is the reconstructed position of femoral insertion of the anterior
cruciate ligament based on ratios obtained from the cadaver study. The numbers (1-6) indicate
each interval of flexion from 100 - 80° (1) to hyperextension > 0° (6). The knee contours were
reconstructed from one of the patients in the study.
NORMAL
INJURED
1 0 0 mm
1:
2:
3:
4:
5:
6:
> 80 °
80 - 60 °
60 - 40 °
40 - 20 °
20 - 0 °
<
0°
Figure 31 Intersections of the helical axes with a sagittal plane through the femoral insertion of
the anterior cruciate ligament.
57
DISCUSSION
Measurement of knee laxity
Instruments measuring knee laxity have been developed to avoid the uncertainty of
manual tests (Daniel et al. 1991). Numerous studies have reported good or
acceptable reproducibility of commercially available arthrometers (Malcolm et al.
1985, Hanten and Pace 1987, Highgenboten et al. 1989, Bach et al. 1990, Steiner et
al. 1990, Wroble et al. 1990, Anderson et al. 1992). In an autopsy study Daniel et
al. (1985A) reported high correlations between the KT-1000 readings and
measurements of skeletal displacements. Later, several authors have questioned
these devices. In inexperienced hands it is difficult to separate ACL injured from
normal knees (Stryker/OSI laxity tester, King and Kumar 1989). Even in skilled
hands the clinical examination has been reported to be a better tool to diagnose
ACL ruptures than arthrometers ( Anderson et al. 1989, Graham et al. 1991).
Forster et al. (1989) observed unexpected variability in the laxity measurements
during the follow-ups after ACL surgery. After assessing the intra- and interexaminer variability they were reluctant to use the KT-1000 as an unbiased
arbiter of ACL surgery.
The measurements with the externally applied devices are distorted by the
patello-femoral alignment and the soft tissues (Edixhoven 1987, Granberry et al.
1990, Shino et al. 1987, Fridén et al. 1992B). These sources of error are completely
avoided using radiography. Some correlation between the KT-1000 and uniplanar
radiographic techniques has been observed although the numerical values differed.
The correlation coefficients has varied between 0.6-0.7 (Moyen et al. 1990, Stäubli
and Jakob 1991). Almost the same correlation was recorded in our study (r=0.6),
but only in the intact knees. Fridén et al. (1992B) compared their RSA set-up with
the Stryker/OSI laxity testers in eleven injured or operated knees. They recorded a
correlation of 0.8.
The relative femuro tibial position before the loads are applied may vary
depending on several factors (Kärrholm et al. 1988, Jonsson and Kärrholm 1990). It
is difficult to reproduce the same reference position for different arthrometers
(Moyen et al. 1990, Stäubli and Jakob 1991) or for the same arthrometer in
longitudinal studies. The anterior play varies depending on the knee flexion,
whereas the AP laxity is less sensitive for the flexion angle (Andersson and
Gillquist 1990). Thus, recordings of the laxity between anterior and posterior
58
endpoints seem to be superior in terms of reproducibility (Wroble et al. 1990).
Further, measurements of the anterior play (e. g. stressradiography, KT-1000) or
between anterior and posterior endpoints ( e.g. RSA set-ups, the Stryker/OSI
arthrometer) may be one important reason for absent or poor correlations between
these techniques.
Normal side to side difference has been determined to establish the threshold
value discriminating the ACL injured from the normal knee. This value is device
specific and reflects the reproducibility of the arthrometer (Steiner et al. 1990). The
RSA, being an invasive method has not been evaluated by bilateral measurements
of healthy knees. Therefore, the side to side difference indicating rupture of the
anterior cruciate ligament has been estimated indirectly. The chosen limit of 2.5
mm was more than two standard deviations of the reproducibility for two different
RSA set-ups (Kärrholm et al. 1988, Fridén et al. 1992A). This limit could also
correctly diagnose about 95% of the ACL injured patients.
The amount of displacement is influenced by the size of load applied (Bach et
al. 1990, Steiner et al. 1990, Fridén et al. 1992A, B, Edixhoven et al. 1989, Shino et
al. 1987). The rationale for using different loads in study I was that we were
interested in the clinical implications the choice of method had. In the RSA set-up
we used 150 N anterior traction and 80 N posterior tractions which were the largest
loads that could be applied without discomfort to the patients. The KT-1000 was
introduced with 89 N anterior traction, which is still the standard force in use. More
patients had their ACL injury diagnosed and fewer patients had returned to normal
stability after surgery according to the RSA set-up than the KT-1000 (I). Similar
result was reported by Moyen et al. (1992). They examined ACL reconstructed
patients two years or more after surgery with stressradiography and the KT-1000.
The mean side to side differences measured with the arthrometer were within
normal limits (<3mm) irrespective of the force applied. With the stressradiography
(90 N, Moyen et al. 1990) the mean displacement of the medial and lateral tibial
compartment exceeded 4 mm which is consistent with our findings.
In normal knees the higher force used with the RSA did not increase the
displacement significantly, probably because of a rapid increment in stiffness in
normal knees. In the injured knees the KT-1000 recorded smaller displacements,
probably because of smaller loads and a more gradual increase in stiffness (Markolf
et al. 1976, Edixhoven et al. 1989). Based on unequal reproducibility of the two
methods and recommendations in the literature (Daniel et al. 1985B) we used
59
different threshold values to diagnose pathological laxity. When the same threshold
value was used for the KT-1000 (2.5 mm, Steiner et al. 1990) the results were
about the same.
Greater applied forces (maximum manual drawer, MMD, about 134-178 N,
Daniel et al. 1985B) have been reported to improve the diagnostic accuracy of the
KT-1000 (Anderson et al. 1992), but this observation has not been confirmed in
other investigations (Bach et al. 1990, Steiner et al. 1990). Paper I was not designed
to evaluate the reason for the diverging results of the two methods, but based on
previous studies it is reasonable to presume that not only the size of the applied
forces was important. Factors related to the technique of measurement and
application of forces had most certainly an influence on the results.
Treatment of the anterior cruciate ligament iqjured knee
Braces. Braces are widely used to protect the ACL reconstructed knee and to
restore stability after ACL rupture. Subjectively, they seem to improve performance
(Colville et al.1986, Cook et al. 1989, Mishra et al. 1989). Two of the braces in the
present study (ECKO, modified Lenox Hill) reduced the AP laxity but not to
normal levels. Forces acting on the ACL during daily activities peak up to 450 N
(Morrison 1970, Grood et al. 1976, Noyes et al. 1984). The examinations in paper
n were made with smaller loads (150N anterior/ 80 N posterior forces ) than would
be expected during daily activities. This suggest that the mechanical effect of the
braces was not underestimated .
Forced internal tibial rotation is a primary mechanism for ACL injury.
Beynnon et al. (1992) noted that some braces reduced the strain in the ACL at an
internal torque of 5 Nm, but this protecting effect disappeared with increasing
torques. In paper II anterior traction (150 N) was added to the torque to mimic
forces resulting in giving way episodes. The braces did not affect internal rotation
with or without anterior traction. Thus, the tested braces did not appear to have any
capability to protect the knee against dangerous internal rotations.
With simultaneous anterior traction and external torque the injured knees
displayed decreased external rotatory laxity compared to the intact knee. Kärrholm
et al. (1989) observed this phenomenon in a study including some patients in study
II and believed that it was an effect of impingement of the posterior edge of the
lateral tibial plateau on the lateral femoral condyle. A similar phenomenon may
occur when the subluxated lateral tibial plateau is reduced after a giving way
60
episode (Galway and Macintosh 1980). The braces in our study did not protect the
knee against this impingement although some of them reduced the anterior tibial
translation. Even if a brace has to resist small forces (Shino et al. 1993) to restore
normal kinematics during the swing phase (Marans et al. 1989) the inability of the
braces to completely reduce the pathological laxity (modified Lenox Hill, ECKO)
with small forces make us reluctant to recommend them from a biomechanical
standpoint.
Surgery - AP laxity. In some patients (III) the same or almost the same
displacements were recorded before and six months after surgery, indicating
insufficient stability at surgery, early graft elongation or rupture. Recent laboratory
studies showed that neither the OTT nor isometric graft positioning can normalise
the AP laxity (Brower et al. 1992). In the eight patients (III,IV) examined the day
after surgery the mean side to side difference was 1.7 mm suggesting that normal or
close to normal AP laxity could be obtained (Figure 18). It was noticed when
analysing these patients separately that the early stabilising effect of surgery was
variable (Figure 19). Other studies examining patients within a few days or
immediately after surgery indicate that the operated knees tend to become tighter
than the contralateral knees at surgery ( Malcom et al. 1985, Moyen et al. 1992,
Good 1993).
During the proceeding three months the AP-laxity increased to a level that
remained almost the same throughout the observation period. Moyen et al. (1992)
observed an increase in anterior laxity within the first two to three months in knees
operated with the OTT technique with and without the Kennedy LAD
augmentation. Almost no change in the side difference was observed during the
following three years. Contrary to our observations the mean side to side
differences were within normal limits (89 N, KT-1000 ). The time for the
elongation coincides with the remodelling phase for the biological grafts, when
their strength is reduced (Aim et al. 1974, Kennedy et al. 1980, Clancy et al. 1981).
Increasing AP laxity during the postoperative months and the presence of abnormal
laxity in most of the operated knees in papers III and IV support that the surgical
procedure and the early rehabilitation period are major determinants for the long
term outcome.
A progressive increase in AP laxity could be observed during the proceeding
18 months of observations in the non augmented group (NA, III) ending with none
of the patients having AP laxity within normal limits. This graft has been found to
61
be one of the weakest structures used for ACL reconstructions (Noyes et al.
1984A). Animal studies (McPherson et al. 1985) have demonstrated that this
weakness persists for a long time. Perhaps they never get a tensile strength
exceeding 50% of the normal ACL. Good (1993) observed a corresponding
increase in AP laxity during the two postoperative years with bone-patellar-bone,
the strongest autograft available (Noyes et al. 1984A). This development calls for
other explanations than ultimate graft strength at the time of surgery. In their study
grafts that had been tightened at the flexion angle providing the shortest distance
between the insertion sites were predisposed to failure.
The surgical treatments used in this thesis yielded small differences in the AP
laxity at the follow-up examinations. The augmented group in study III displayed a
small improvement in AP laxity six months after surgery. One year or later this
improvement had disappeared indicating that the augmentation did not protect the
graft from failure. The knees in study IV had almost the same AP laxity six months
after surgery as the augmented group in study III, but during the following period
no further lengthening occurred maybe reflecting improved surgical technique. The
NA group (III) were about 1 mm tighter six months after surgery than any of the
other groups. These variabilities in patterns of postoperative elongation might
have been an effect of the graft used, but may also reflect different rehabilitation
protocols.
In our study no difference in AP laxity was observed at two years between the
groups. Inability to achieve a correct anatomical position despite the use of the drill
guide might be one explanation. Good et al. (1987) evaluated the precision of the
Stryker drill guide by measuring the femoral and tibial tunnel placement on lateral
radiographs calculating ratios in a similar manner as in this study. They obtained a
femoral position ratio coinciding with the anatomical ligament insertions observed
in a cadaver study. According to their observations the average position of the
femoral tunnel in our study was correct whereas the tibial tunnel was slightly more
anterior than the ideal one. Our own specimen data (Jonsson and Kärrholm 1992)
suggested a location of both tunnels which were anterior to the anatomical
positions, indicating that isometry was not obtained. Aglietti et al.(1992) and Good
et al. (1993) demonstrated that a too anteriorly positioned femoral ACL attachment
predisposed for graft to fail. In study IV the femoral tunnel position did not
correlate to the AP laxity at two years. Differences in the assessment of the tunnel
position or the graft used (Agletti et al. 1992, Good 1993) might explain this
62
discrepancy. Weaker grafts (Noyes et al. 1984A) and early elongation (IV) might
also have reduced the influence of a too anterior femoral attachment.
A source of graft failure is impingement at the notch because of a too anterior
and lateral tibial tunnel placement (Yamamoto et al. 1992). Notchplasty can to
some extent compensate for this malpositioning (Yarn et al. 1992, Howell et al.
1991). In our study the influence of the tibial tunnel position on the anteriorposterior stability was small. This could partly be due to the routinely performed
notch plasty. Some degree of graft impingement can even exist without
jeopardising stability (Howell et al. 1992). Increased laxity and slackening of the
graft may have reduced the negative effects of subsequent impingement.
Knee stability and function
Lysholm and Gillquist (1982), Johnson et al. (1984) and Odensten et al.(1985)
observed that knee laxity correlated to the patients evaluation of knee function.
Noyes et al. (1984) emphasised that the subjective evaluation of knee function
should be combined with activity level evaluation. They developed a scoring
system with this purpose in mind (Cincinatti rating system). Harter et al. (1988)
modified this rating scale but failed to find any relationship with objective laxity
measurements (KT-1000).
In papers III-IV there were no or almost no correlation between injured-intact
AP laxity difference and the subjective functional scoring, activity scaling, muscle
strength, functional performance. Classification of the knees into stable and
unstable knees according to RSA measurements or pivot shift (IV) indicated that
instability was of importance, but should be decreased to normal or almost normal
to have a significant effect on the results.
Many scores and tests have been used for the evaluation of ligament surgery.
Some authors suggest a comprehensive evaluation including knee function, activity
level, laxity examination and functional tests (Kdolsky et al. 1992, Müller et al.
1988, the IKDC form). Others favour separate evaluation of the different
parameters (Tegner and Lysholm 1985). Clinical examinations of knee stability
only evaluate passive knee restraints, whereas functional stability is a more
compound entity (Noyes et al. 1980) also including factors such as muscle strength
(Tegner et al. 1986A) and proprioception (Barrett 1991).
According to the Lysholm score most patients in study III and IV would be
regarded as having good or excellent results whereas few had postoperative AP
63
laxity within normal limits. The Lysholm score classifies more patients as good or
excellent compared to other combined evaluation forms (Howe et al. 1991,
Engström 1993). This is not surprising in the light of the inconsistency between the
Lysholm score and AP laxity found in our studies (III, IV).
Knee Kinematics
Skeletal motions and clinical tests of joint stability occur in three dimensions even
if a specific component of the motion or stability usually is in focus. The anterior
drawer and Lachman tests start with the tibia in a reference position (Lachman
about 20 0 of knee flexion) and rotations and translations are defined according to a
coordinate system (Daniel and Biden 1987) fixed to the tibia. Continuos joint
motion is more complicated to assess or describe. The coordinate systems used,
their positions in relation to skeletal landmarks and the precision of landmark
identification (radiographs or external digitization) vary making comparisons
between kinematic studies difficult (Penncock and Clark 1990, Kurosawa et al.
1985, Grood and Suntay 1983, Lafortune and Cannavgh 1984, Huiskes et al. 1985).
Further, three-dimensional movements with six degrees of freedom may be
difficult to transform into anatomical terms. The motion can also be calculated as
rotation and translation in relation to one helical axis. This method is less dependent
on the coordinate system used ( Huiskes et al. 1985).
Changes in the pattern of motion has been proposed to be responsible for knee
deterioration (Berchuk et al. 1990, Marans et al. 1989). RSA examinations of
controlled weight-bearing (VI) or active flexion and extension (V) without ground
reacting forces do not mirror the complexity of the gait restricting the conclusions
to be drawn. The multidirectional instability observed at active flexion (Kärrholm et
al. 1988) was reduced at extension with (VI) and without (V) weight bearing or
during gait (Marans et al. 1989).
Palmer (1938) and Van Dijk (1983) suggested that the screw home movement
at the end of the extension was controlled by the ACL, muscle activity and joint
geometry. Hallen and Lindahl (1966) questioned its existence and Marans et al.
(1989) did not observe it during gait. During active knee extension (V) or extension
and weight-bearing (VI) we observed a screw home motion. Contrary to the
situation during active knee flexion (Kärrholm et al. 1988) there was no difference
between the intact and injured knees, suggesting variable function of the ACL
64
depending on the direction and presence of the muscular and ground reacting
forces.
Kinematics and physiotherapy after surgery. In the immediate postoperative period
the graft fixation (Kurosaka et al. 1987) and later the biological graft (Aim et al.
1974, Arnoczky et al. 1982, Kennedy et al. 1980, McPherson et al. 1985) restricts
the rehabilitation protocol. Active knee extension with weights at the ankle is
commonly used for knee rehabilitation. Indirect calculation during isometric or
dynamic quadriceps contraction has revealed anteriorly directed shear forces in the
knee at a flexion angle less than 30-45 0 peaking up to 600 N (Yasuda and Sasaki
1987 B, Nisell 1985). Recently Shino et al. (1993) assessed much lower loads
(23N) in the reconstructed ACL grafts during active extension or straight leg raise
in vivo. Beynnon et al (1992,1993) have documented increased strain the anterior
cruciate ligament close to full extension. Grood et al. (1984) registered an increased
mean anterior tibial displacement of 3.8 mm at 15° during extension after cutting
the ACL in five cadavers knees. Under similar loading conditions we found mean
distal and anterior displacements of about 2 mm in the injured knees that were
reduced close to full extension. The difference between the cadaver study and ours
may be due to synergistic activity by the hamstring muscles (Solomonow et al.
1987).
Simultaneous quadriceps and hamstring contractions reduce the anteriorly
directed shear forces (Yasuda and Sasaki 1987A). Axial load stabilise the knee
further (Markolf et al. 1981, Hsieh and Walker 1976). Quadriceps contractions in
the standing position up to 15° of knee flexion has been suggested in the early
rehabilitation because this activity does not produce anteriorly directed shear forces
especially with the hips slightly flexed (Ohkoshi et al. 1991). Shino (1993)
recorded peak values of 84 N in the ACL graft during gait and Beynnon et al.(1993)
found a 4% increase in the strain during squatting. Contrary to an in vitro study by
Reuben et al. (1989) we found that the tibia was more posteriorly displaced on the
injured side than on the intact side during extension and weight bearing (VI).
Changed pattern of motion reducing quadriceps activity has been observed
during gait (quadriceps avoiding gait, Berchuk et al. 1989). Altered movements and
muscle activation patterns have been found to reduce anteriorly directed shear
forces during one leg hop in well rehabilitated chronic ACL injured patients
(Gauffin and Tropp 1992). Increased hamstring activity seems to be an important
65
part in this functional adaptation (Solomonow et al. 1987, Branch et al. 1989) and
could also be responsible for our results (VI).
Helical axes. In the study of simultaneous weight-bearing and extension (VI) the
helical axes intersected the lateral femoral condyle closer to the joint line on the
lateral than on the medial side during the major part of the extension. This
implicates more rolling on the lateral side and more gliding on the medial one. At
about 90°of flexion the helical axes were approximately parallel to the joint line
suggesting an even distribution of these motions. Blankevoort et al.(1988) found
that passive knee motion was restricted by soft tissue stiffness enveloping a certain
range of internal/external rotation and adduction/abduction. Inside this envelope
axial loads were the main constrain to the motion. Therefore, it would be difficult to
find any reproducible axes within the limits of normal rotational laxity. Van Dijk
(1983) examined cadaver knees during flexion and found a similar pattern for the
helical axes as in our study (VI). Flexion of the internally or externally rotated tibia
resulted in changed positions of the helical axes and especially during external
rotation. The variability of the axes positions in our study increased close to full
extension. This might be due to that joint geometry enabled the patients to choose
alternative patterns of motion close to full extension whereas the circular shape of
the posterior femoral condyles (Kurosawa et al. 1985) restricted the motion to a
defined path at 100 to 80 degrees of flexion. Probably this variability would have
been less if continuous active motion had been recorded.
In study VI the mean helical axis was positioned close to the femoral insertion
of the anterior cruciate ligament at about 90° of flexion moving anteriorly during
extension in agreement with the femoral centrode and previous cadaver studies by
van Dijk (1983). The pattern for the displacement of the helical axis in study VI
displayed a more complex pattern that would be expected according to the four bar
linkage model. This discrepancy can be explained by simultaneous rotations about
the longitudinal axis. These rotations make a plane perpendicular to the femoral
centrode not parallel to any sagittal plane. Further, the four bar linkage model
requires two non elastic bars whereas the tension in the cruciates varies during
motion (Kurosawa et al. 1991). The ACL injured knees revealed almost the same
helical axis displacement in the sagittal plane suggesting other or supplementary
explanations for the tracking of knee motion than the cruciates. Blascharski et al.
(1975) concluded that joint geometry was the major determinant for knee
66
kinematics. The tracking of the knee motion is probably controlled by joint
geometry, ligaments and muscle activity.
67
GENERAL CONCLUSIONS
Measurement of knee laxity
• When used with 89 N the KT-1000 measured smaller translations than RSA in
injured and operated but not in normal knees resulting in smaller side to side
differences. The diagnostic sensitivity of the KT-1000 is inferior and this
arthrometer may overrate the stabilising effect of reconstructive surgery. (I )
• Using the RSA set-up a side to side difference between the knees of 2.5 mm
would indicate a rupture of the anterior cruciate ligament in more than 95 of 100
patients (I)
• The reproducibility of the KT-1000 in our hands did not deviate from other
studies.(I)
Knee stability and function
• Subjectively nine out of ten patients rated their knee function good or excellent
two years after surgery and about half of them reached statisfactory résultés
according to the functional tests. Only one out of ten patients had their knee
laxity in the operated knee returned within normal limits.(III)
• No numerical correlation was observed between the AP laxity (side to side
difference) and subjective or objective functional evaluation. If the laxity was
reduced wthin normal limits the patients had higher activity levels or were
stronger and performed better in the one leg hop tests. (Ill, IV)
Treatment of the anterior cruciate ligament inured knee
• Two of three braces investigated partially reduced the AP laxity. The internal
rotatory laxity was not affected. The external rotatory laxity was reduced by one
of the designs.(II)
• Six months after surgery about one third of the patients had an AP laxity within
normal limits. Increasing AP laxity was observed after six months suggesting
inappropriate graft strength even after the early remodelling and rehabilitation
phase.(III)
68
• The isometric ACL placement with the aid of a drill guide did not offer any
advantages compared to the over the top technique. (IV)
Knee kinematics
• Absence of the ACL ligament was associated with increased anterior and distal
displacements of the tibial intercondylar eminence during active knee extension
in the supine position. (V)
• During extension and weight-bearing lack of ACL was associated with
posterior displacement of the tibial intercondylar eminence.(VI)
• Between 100° and 80° degrees of knee flexion during the extension and weight­
bearing the helical axes were close to the femoral insertion of the ACL and
parallel to the joint line. From this position the axes moved anteriorly and
distally on the lateral side suggesting more translatory movements in the medial
compartment. The changes in the three-dimensional positions of the helical axes
observed imply that limited conclusions can be drawn from two dimensional
models (VI).
69
ACKNOWLEDGEMENTS
I wish to express my sincere gratitude to:
My friend and tutor, associate professor Johan Kärrholm for teaching me roentgen
stereophotogrammetry, for guiding me into science, his patience and encouragement, but most of
all for making this project enjoyable.
Professor Lars-Åke Broström, Department of Orthopaedics, University Hospital in Northern
Sweden in providing working facilities and constructive critisism of the manuscript.
Associate professor Sven Friberg, Head of the Department of Orthopaedics, University Hospital
in Northern Sweden for his encouragement.
The late professor Lars- Ingvar Hansson for bringing me to Umeå.
My co-authors Lars Gunnar Elmqvist, Umeå and Yelverton Tegner at the Ermeline Clinic in
Luleå.
Barbro Appelblad and Torsten Sandström for measuring innumerable number of radiographs.
Torsten Sandström, Dept, of Sports Medicine, Mats Långström, Department of Physical
Medicine and Rehabilitation ,University Hospital of Northern Sweden, Umeå and Sten-Allan
Pohjanen ,Dept of Physiotherapy, Central Hospital in Boden, for helping me with the functional
tests.
The staff at the department of radiology for helping me with the RSA examinations, never saying
no to additional patients.
Olle Carlsson, Department of Statistics for statistical advice.
Ulla Stina Frohm for helping me with practical arrangements.
My colleagues at the Department of Orthopaedics.
My patients who patiently tolerated all the examinations.
The MPC:s of Boden for fruitful discussions throughout the years
But most of all my family, Marie, Henrik, Hanna and Johan
70
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84
APPENDIX
Tables A l - 4. Rotatory laxity in normal and ACL injured knees with and
without braces. Each brace design was tested on seven injured knees. Seven
(SKB group) or six (ECKO, Lenox Hill) contralateral normal knees were used as
controls.
Table A -l Internal rotation
Difference
_________________deg (SD)________________ p-value
All cases
Normal (N)
17.0 (4.7) N-I
n.s.
Injured (I)
n.s.
17.3 (5.2) I-IB
Braced (B)
n.s.
17.3 (5.2) N-IB
SKB
Normal (N)
17.9 (3.8) N-I
n.s
Injured (I)
n.s
18.0 (5.5) I-IB
Injured-braced (IB) 18.4 (5.3) N-IB
n.s.
ECKO
Normal (N)
n.s
17.5 (5.9) N-I
Injured (I)
15.4 (5.8) I-IB
n.s.
Injured-braced (IB) 15.8 (5.7) N-IB
n.s
Lenox Hill
Normal (N)
15.6 (4.7) N-I
n.s
Injured (I)
18.4 (4.3) I-IB
n.s.
Injured-braced (IB) 17.5 (4.9) N-IB
n.s
Table A-2 External rotation
Difference
p-value
deg (SD)
All cases
Normal (N)
Injured (I)
Braced (B)
SKB
Normal (N)
Injured (I)
Injured-braced (IB)
ECKO
Normal (N)
Injured (I)
Injured-braced (IB)
Lenox Hill
Normal (N)
Injured (I)
Injured-braced (IB)
n.s.
<0.005
<0.005
15.5 (7.5)
13.1 (5.3)
9.5 (4.4)
N-I
I-IB
N-IB
15.6 (7.4)
13.2 (5.1)
9.2 (3.6)
N-I
I-IB
N-IB
n.s
n.s
n.s
14.7 (7.9)
12.7 (5.3)
10.9 (3.3)
N-I
I-IB
N-IB
n.s.
n.s.
n.s.
16.7 (8.3)
13.4 (6.3)
8.4 (6.0)
N-I
I-IB
N-IB
n.s.
<0.005
<0.02
3.6
6.0
85
Table A-3 Internal rotation -Anterior traction
Difference
deg (SD)
All cases
Normal (N)
19.3 (4.8) N-I
Injured (I)
19.1 (5.3) I-IB
Braced (B)
19.1 (5.4) N-IB
SKB
Normal (N)
20.5 (2.5) N-I
Injured (I)
20.0 (6.6) I-IB
Injured-braced (IB) 19.7 (6.0) N-IB
ECKO
Normal (N)
19.9 (6.0) N-I
Injured (I)
17.3 (5.3) I-IB
Injured-braced (IB) 17.6 (6.3) N-IB
Lenox Hill
Normal (N)
17.5 (5.6) N-I
Injured (I)
20.2 (4.2) I-IB
Injured-braced (IB) 19.9 (4.3) N-IB
Table A-4 External rotation -Anterior traction
Difference
deg (SD)
All cases
Normal (N)
10.3 (8.1) N-I
8.5
Injured (I)
1.4 (6.4) I-IB
-2.7
Braced
4.1 (6.7) N-IB 6.4
SKB
Normal (N)
9.9 (9.1) N-I
Injured (I)
0.1 (6.8) I-IB
Injured-braced (IB) 4.0 (6.9) N-IB
ECKO
Normal (N)
9.1 (6.1) N-I
Injured (I)
3.4 (5.1) I-IB
Injured-braced (IB) 6.8 (7.0) N-IB
Lenox Hill
Nomai (N)
11.9 (9.7) N-I
10.2
Injured (I)
0.7 (7.4) I-IB
Injured-braced (IB)
1.4 (6.1) N-IB 9.9
p-value
n.s.
n.s.
n.s.
n.s
n.s
n.s.
n.s
n.s.
n.s
n.s
n.s.
n.s
p-value
<0.005
<0.03
<0.005
n.s.
n.s.
<0.04
n.s
n.s
n.s
<0.01
n.s.
<0.03
86
All RSA examined patients
Nr
201
202
203
207
210
211
212
213
215
217
218
219
220
222
224
225
227
228
229
230
231
232
233
234
235
236
238
240
242
Study
III
m
m
m
I,in
m
in
in
i,in
i,m
i,m
i,in
i,m
ii
i,in
I,HI
i,in
i,m
ii
ii
IJWV
I,II,IV
i,in
ii
uv,v
i
i,in
i,in
I,in
Age
44
25
24
21
37
28
18
31
26
46
24
25
21
29
30
30
22
32
27
28
28
24
32
16
23
29
26
40
23
Sex
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
F
M
F
M
M
M
Pur
1.5
4
1
0.7
15
2
1
1
3
1
2
1
2
Surg
NAP
NAP
NAP
NAP
NAP
NAP
NAP
NAP
NA
NAP
NAP
NAP
NAP
2
7
1
13
NAP
NAP
NAP
NAP
6
6
6
OTT
OTT
NA
2
12
5
3
2
ISO
GOR
OTT
OTT
OTT
Sex: M= male, f=Female
Dur: Duration injuryexamination or surguy
Surg: Type of surgery
OTT= over the top with Kennedy
LAD
ISO=isometric, with drill guide
NA=Non Agmented over the top
NAP= NA and pes anserine
transposition
GOR=Goretex graft
AP laxity
N
I
6.6
14.4
3.9
5.8
5.5
4.6
4
2.9
6.7
4.4
2.5
2.5
7.2
4
5.4
5.2
4.2
6.9
2.6
3.2
3.4
7.4
2.4
17.7
10.5
16.1
10.7
12.7
9.3
17.9
12.3
10.5
8.1
19.7
15
13.3
14.6
9.6
13.3
9.3
16
16.2
13
7.8
6m
5.6
7.3
9.3
4.3
8
8.3
8.6
3.3
10.4
7
6.8
12.3
4.7
12m
8.6
5
9.2
6.5
7.7
9.5
2.9
6.6
11.8
8.1
7.6
10.3
7.8
24m
7.3
8
9.7
9.5
6.4
8.4
10.9
4.6
10.9
9.9
10.2
12.8
7.5
Functional score
PL
PT 2L
53
3
100
3
97
63
60
4
51
99
65
5
74
58
6
4
67
99
70
3
95
59
94
5
84
59
4
45
4
93
59
95
5
80
4
100
77
99
5
2T
5
7
3
9
2
7
3
7
4
4
6
9
9
10
5
0.2
9.6
10.4
5.4
6
10.3
10.5
8.7
8.4
10.7
48
53
77
47
4
4
5
0
84
54
95
82
7
4
7
3
8.8
13.9
5.6
9.2
14
8.9
8.1
11.3
10.2
52
71
61
4
7
4
95
95
100
5
8
7
5.6
3.4
8.5
12.4
7.8
8.6
9.6
11.3
12.9
8.4
8.7
7.9
11.4
14.1
9.8
76
5
76
3
76
54
66
5
3
5
96
91
99
7
4
7
N: Normal
I: Injurred
PL: Preoperative Lysholm score
PT: Preoperative Tegner score
6m, 12m, 24 m: 6,12,24 month
examination of AP-laxity
2L: 2 year Lysholm score
2T: 2 year Tegner score
87
Nr
245
246
249
250
251
252
253
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273a
275
276
277
278
280
281
282b
283
285c
286d
287
Study
I
1.111
I
1.111
1.111
1.111
1.11.111
I
U V ,v
I
II
1.111
I,V
IJV,V
1.111,V
i,ni,v
i ,ih ,v
i,m
ijv .v
i,v
1.111,V
I,IV
i ,iv ,v
I,II,IV
i,rv ,v
i
I,IV
I,IV
I
I,II,IV
I,IV
i ,iv ,v
il
I,IV
i
i
I,II,IV
Age
19
38
25
20
26
24
24
31
24
21
39
22
22
22
20
26
35
32
36
20
25
23
26
17
27
23
20
19
25
28
15
17
24
21
23
32
29
Sex
F
F
M
F
M
M
M
M
M
M
M
F
M
F
M
M
M
M
M
M
M
F
M
M
M
M
M
M
M
M
F
F
M
F
F
M
F
Surg
OTT
4
1
1
2
15
4
OTT
OTT
NA
OTT
GOR
OTT
GOR
OTT
6
1
1
13
2
12
6
2
6
4
1
1
2
2
3
1
5
7
5
a: Not included in study IV
because of both ACL and PCL
injury
b: Bilateral ACL injuries.
ISO
OTT
OTT
OTT
OTT
OTT
OTT
OTT
ISO
OTT
OTT
OTT
OTT
ISO
OTT
OTT
ISO
ISO
OTT
NA
ISO
AP laxity
N
I
1.4
8.3
2.6
6.9
2.2
11
1.3
7.8
4.3
13.5
8.7
4.3
14.1
7.9
?
8.9
1.6
13.3
7.5
20.8
15
8.8
7.7
2.7
5.8
7.6
3.9
7.6
3.6
7.5
2.8
14.7
4.8
11.1
1.9
10.8
4.7
14.1
7.8
15.2
1.5
16.8
3.6
9
7.2
13.3
17.1
9.8
4.5
8.5
9.8
16.8
8.6
13.7
5.8
11
10.9
15.6
17.7
4.2
9.1
16.3
16.4
10.5
15.8*
19.2*
10.9
6.1
4.2
9.8
3.6
6.6
14.7
3.3
6m
12m
24m
Functional score
PL
PT 2L
6.1
6.3
7.4
62
2
94
7
11.1
12.1
5.3
14
10.9
8
9.3
11.4
10.4
6.6
13.2
12.3
9.4
14.2
10.7
9.4
6.2
12.4
10.4
7.9
22.2
57
69
64
74
50
60
65
3
4
3
4
2
5
3
90
95
100
96
88
83
66
5
6
7
7
4
6
4
5.9
8
10.2
66
4
95
5
6
10.3
10.1
5.8
5.5
10.2
7.4
8.5
10.4
8.1
7.8
9.3
9.1
9.4
9.7
8.5
7.4
62
76
71
74
71
80
4
6
4
4
4
5
64
100
100
100
99
98
3
7
9
7
5
7
13.1
6.4
10.3
12.9
3.4
10.6
9.5
7.8
12.4
7.9
13
12.7
6.9
12
9.7
7
13.2
7.2
10.7
10.2
7.1
13.3
10.6
8.5
69
64
51
80
62
4
2
0
5
4
95
70
67
85
73
9
7
3
7
5
84
84
3
4
84
100
9
9
8.4
13.7
13.7
8.1
13
11.9
6.4
12.1
12.1
59
76
87
4
5
9
76
90
100
4
8
10
7.7
6.0
1.2
10.2
11.1
7.0
5.2
11.1
9.6
69
5
76
5
6.4
10.1
65
3
c: Not included in study IV due to previous
intraarticular ACL surgery.
d: Did not want to participate instudy IV.
2T
88
AP laxity
I
Study Age Sex Dur Surg N
Nr
24
M
36
10
OTT 2.9
288 i,n ,iv
6
15.2
M
OTT 6
30
289 i,n ,iv
8.6*
10.9*
20
F
291.fr i
5
ISO 4
8
23
F
296 I,IV
7.7
F
3
OTT 5
300e I,IV
20
F
3
ISO 5.9
9.1
301 I,II,IV 19
12.3
6
OTT 3.2
29
M
302 i,n ,iv
3.7
17
F
11.1
304 i,ii
7.8
M 0.5 ISO 8.8
29
305 I,IV
9.9
M 0.5 ISO 5.1
25
306 I,IV
19.4
F
5
OTT 6.8
307 I,IV
22
15.3
F
6.1
308f i,ii
21
M 7
12.9
26
OTT 7
309 I,IV
19.6
24
F
2
OTT 5.7
310e I,IV
F
4
OTT 5.4
10.2
26
312 I,IV
14.9
19
F
1.5 ISO 7.2
313 IV
14.1
38
M
314e I,IV
1
OTT 9.8
7.3
16.2
33
M
11
315 I
27
12.4
M 2
OTT 5.1
3188 I
15.7
319 I,IV,VI 27
M 2
ISO 7.6
M
320 IV
22
2
ISO 4.5
15.1
24
M
1
13.5
321 I,IV
OTT 5.7
M
10.3
322 I,IV
26
12 OTT 7.6
M
10.3
323 I,IV,VI 21
1
ISO 7.6
2
324 I,IV,VI 18
8.7
F
OTT 2.2
325 I,IV
23
M
ISO 7.7
16.7
1
326e I,IV,VI 21
M 2
OTT 6
16
327 I,IV
26
M 2
ISO 7.2
13.8
328 I, IV
17
F
ISO 6.6
10.6
1
7.4
331 I,IV
26
M 3
OTT 2.6
12.7
2.5 OTT 4.4
332 I;IV,VI 31
F
10.7
333 I,VI
18
F
7.2
e : Excluded study IV due to
postoperative immobilisation.
6m
12m
24m
Functional score
PL
PT 2L
12.8
9
10
6.8
5.9
6.7
8.6
12.3
8.6
10.1
8.2
5.1
6.4
8.5
12.4
8.4
10.2
2.1
4.2
10.2
8.1
55
57
70
55
57
45
76
1
3
4
4
5
5
5
86
83
91
77
87
85
85
4
7
7
7
8.3
8.3
11.3
9.4
8.1
9.4
7.2
10.7
76
75
55
9
6
2
90
82
91
10
7
7
12.3
11.6
9.7
13
11.8
10.8
11.7
11.3
9.8
13.1
6.8
13.3
9.4
11.4
11
54
40
80
50
62
4
4
5
3
0
56
88
100
72
62
4
8
7
5
0
9.6
12.2
6.7
8.1
11.9
10.3
6.3
8.9
8.5
7.5
10.7
9.1
11.7
5.3
6.6
86
62
79
81
65
45
77
59
85
73
89
62
66
5
99
72
85
89
100
81
100
78
81
8
3
7
9
5
7
8
100
100
9
6
7.3
10.9
10.9
7.1
10.7
10.4
10.6
9.9
5.6
10.5
^ Not included . The surgeon did not
participate in the study.
10.2
8.3
9.9
9.8
3.4
12.2
9.5
9.5
6.6
4.6
4
5
5
5
1
6
4
3
2T
3
6
4
4
4
4
3
3
0
8 : Not included, was not
randomised
89
Nr
334
335
336
337
338
339
340
341
342
343
344
346
347
348
349
350
351
352
354
355
356
359
360
362
366
367
368
369
370
Study
I
I,IV
I,IV,VI
I,IV,VI
I,IV
I,IV,VI
I
I,IV,VI
I
I,IV
I,IV
I,IV,VI
I
I,IV,VI
IV
I
I
I
I,VI
I
I
I
I
I
I
I
I
I
I
Age
31
21
40
31
22
24
20
22
28
21
25
35
19
26
30
24
23
21
25
25
24
22
37
23
15
25
26
26
26
Sex
M
M
M
F
F
M
F
M
M
F
M
M
F
M
F
M
F
M
M
F
F
M
M
F
F
M
M
M
M
AP laxity
Dur Surg N
I
6.3
14.6
7
0.8 OTT 4.4
15 ISO 4.9
17.9
ISO 6.9
9.8
8
ISO 4.8
17.8
2
3
OTT 6.5
12.2
6.6
22.1
13.7
0.9 ISO 5.9
4.9
16.2
4
OTT 6.6
10
4
14.6
OTT 4.3
10.8
3
ISO 7.1
5.6
10.6
3
OTT 7
10.2
ISO 4.9
8
10
5.8
11.7
12.9
6
6.6
10
6.6
19
9.7
5.2
2.6
9.9
3.9
14.6
5.8
18.9
10.7
2.5
1.7
12.4
10.5
5.1
4.9
8.7
4.3
14.6
5.9
20.1
6m
12m
24m
Functional score
PL
PT 2L
2T
9.3
13
8
12.3
9.5
7.1
11.8
9.2
10.3
6.3
8.7
9.5
15
7.1
90
66
59
90
89
7
3
3
7
4
100
99
95
89
99
9
5
7
9
7
12.1
12.2
16.6
71
0
34
0
10.3
7.8
8
9.1
8.1
11
10
9.8
9.2
70
69
69
4
0
3
90
90
84
7
6
7
9.5
6.4
8.8
9.3
10.6
7.7
79
50
4
3
100
58
5
3