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A biomechanical assessment of a distally-fixed lateral extra-articular
augmentation procedure in the treatment of anterolateral rotational laxity of the
knee
Devitt BM1*, Lord BR2*, Williams A3, Amis AA2,4, and Feller JA1
1 OrthoSport Victoria, Epworth Healthcare, Melbourne, Australia
2 The Biomechanics Group, Department of Mechanical Engineering, Imperial College
London, London, SW7 2AZ, United Kingdom
3 Fortius Clinic, London, United Kingdom
4 Musculoskeletal Surgery Group, Imperial College London School of Medicine,
London, United Kingdom.
* The following authors are co-first-named authors
Corresponding author: Brian M Devitt
Email: [email protected]
Twitter feed: @OSVResearchUnit
Address: OrthoSport Victoria, 89 Bridge Road, Richmond, VIC 3121, Australia
Telephone: +61390385200
Fax: +61390385200
Primary Affiliation:
This investigation was performed at Department of Mechanical Engineering, Imperial
College London, London, SW7 2AZ, United Kingdom.
Acknowledgements:
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Mr BR Lord was supported by a grant from the North Hampshire Hospital
Orthopaedic Research Fund. The robotic testing system was provided by the
Imperial College London Centre of Excellence in Biomedical Engineering in
Osteoarthritis, funded by the Wellcome Trust and the EPSRC. We thank Dr H El-
Daou for writing the robot control software and running the robot, Dr JM Stephen for
help in the laboratory, and Dr KK Athwal for the statistical analysis.
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A biomechanical assessment of a distally-fixed lateral extra-articular
augmentation procedure in the treatment of anterolateral rotational laxity of the
knee
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Abstract:
A variety of lateral extra-articular tenodesis (LEAT) procedures have been described
and most rely upon passing a strip of the iliotibial band (ITB) under the Fibular
(lateral) collateral ligament (FLCL) and fixing it proximally to the femur. One of the
concerns is the potential to increase lateral compartment constraint. The Ellison
procedure is a distally-fixed lateral extra-articular augmentation procedure with no
proximal fixation of the ITB. It has the potential advantages of maintaining a dynamic
element of control of knee rotation and avoiding the possibility of over-constraint.
Purpose:
To assess the ability of a distally-fixed lateral extra-articular augmentation procedure
(modified Ellison) to restore native knee kinematics following complete sectioning of
the anterolateral capsule (ALC). A secondary aim was to assess what effect closure
of the ITB defect would have on knee kinematics.
Hypothesis:
The modified Ellison procedure would restore native knee kinematics following
sectioning of the ALC, and closure of the ITB defect would decrease rotational laxity
of the knee.
Study design: Controlled laboratory study
Methods:
Twelve fresh frozen cadaveric knees were tested in a 6 degrees of freedom robotic
system through 0-90 of knee flexion to assess anteroposterior, internal (IR) and
external rotation (ER) laxities. The simulated pivot-shift (SPS) was performed at 0,
15, 30, and 45 of flexion. Kinematic testing was performed in the intact knee, ALC-
injured knee, and following the modified Ellison procedure, with and without closure
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of the ITB defect. A novel pulley system was used to load the ITB at 20N for all
testing states. Statistical analysis used repeated-measures analyses of variance and
paired t tests with Bonferroni adjustments.
Results:
Sectioning of the ALC significantly increased anterior drawer and IR during isolated
displacement and with the SPS (P<0.05). Analysis of both isolated and coupled IR, at
0° of knee flexion or greater, revealed that the modified Ellison reduced this
anterolateral rotatory laxity significantly (P<0.05). During isolated IR testing, IR was
reduced close to the intact state with the modified Ellison procedure, except at 30 of
knee flexion when it was slightly below the intact knee (overconstraint).
Measurement of IR during the SPS revealed that IR with the closed modified Ellison
was below that of the intact state at 15° and 30° of flexion. No significant differences
in knee kinematics were seen between the ‘ITB-defect open’ and ‘ITB-defect closed’
states.
Conclusion:
A distally-fixed lateral extra-articular augmentation procedure (modified Ellison) can
reduce anterolateral rotatory laxity of the knee and restore knee kinematics close to
the intact state. Closing the ITB defect did not affect knee kinematics, compared to
leaving it open.
Clinical Relevance:
A distally-fixed lateral extra-articular augmentation procedure (modified Ellison) is
effective in reducing anterolateral laxity of the ALC-injured knee and restores
kinematics close to the intact state. Closure of the ITB defect has no effect on knee
kinematics.
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Key terms: Extra-articular tenodesis, Ellison, Anterolateral Rotatory Instability, knee
kinematics
What is known about the subject:
The vast majority of biomechanical studies to date have focused on proximally-fixed
LEAT and no biomechanical studies have analysed the efficacy of a distally-fixed
lateral augmentation procedure to control anterolateral rotatory laxity (ALRL) of the
knee.
What this study adds to existing knowledge:
This study uses a novel loading of the ITB in a robotic testing system, designed to
replicated normal physiological loads in the knee during simulated clinical
manoeuvres. In doing so, the authors have tested a distally-based lateral
augmentation procedure (modified Ellison) and demonstrated that it can reduce
ALRL and restore the knee kinematics close to the intact state. The study has also
shown that closure of the ITB defect has no effect on knee kinematics, which is a
new finding in the literature.
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Introduction
Anterior cruciate ligament (ACL) rupture typically occurs due to sudden axial loading
of the knee in conjunction with a coupled valgus and rotational moment about the
tibia27, 28, 36. The ACL is not the only structure damaged during this mechanism of
injury and studies have shown that the anterolateral complex of the knee is also
commonly involved5, 15, 34, 45. The anterolateral complex has been reported to consist
of the iliotibial band (ITB) with its superficial, middle, deep, and capsulo-osseous
layers as well as the anterolateral joint capsule (ALC)17. Among these structures,
some authors have identified a capsulo-osseous band: the anterolateral ligament
(ALL)6,9. Biomechanical studies have established that the anterolateral complex plays
a role as a secondary stabilizer to control anterolateral rotational laxity 13, 19, 24, 38.
Indeed, it has been suggested that failure to address the anterolateral injury at the
time of ACL reconstruction may increase the risk of graft failure due to persistent
anterolateral rotational laxity 1, 4, 19, 24, 37 38, 42.
Surgeons have long recognised that lateral extra-articular augmentation procedures
are an effective method to control rotation of the knee 10, 29, 33. The concept of
combining a lateral extra-articular augmentation with an intra-articular reconstruction
for the treatment of ACL injury emerged with a view to decrease the failure rate of
either technique carried out in isolation. The approach became popular in the 1980s
and was adopted by a number of surgeons using a variety of extra-articular
augmentation procedures, all non-anatomical in nature.10, 22, 29-31 However, following
recent reports describing the anterolateral ligament of the knee, anatomic
anterolateral reconstructions have also been reported41, 42.
The majority of these lateral extra-articular augmentation procedures are based on a
proximally-fixed construct, typically using a strip of ITB, which remains attached to its
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insertion at or near to Gerdy’s tubercle40. The free proximal end passes either deep
or superficial to the lateral collateral ligament (LCL)FCL, and is fixed to the femur
proximal to the lateral epicondyle. However, a distally-fixed ITB transfer, originally
described by Ellison, has also been used10. This technique uses a strip of ITB, which
is elevated from Gerdy’s tubercle with a sliver of bone and reflected proximally, then
passed deep to the FLCL, and reattached to the region of Gerdy’s tubercle. Prior to
passage of the strip of ITB deep to the FLCL, the ALC is plicated. The defect in the
ITB is subsequently closed. The proposed advantage of this technique was that it
maintained an element of dynamic control of rotation by not fixing the strip of ITB
proximally, but keeping it in continuity with the rest of the ITB. As a result the
construct will tend to tighten in extension, as it deviates from its natrural alignment
around the FLCL, and slacken as the knee flexes25 . As a result it will be effective at
the lower flexion angles when the pivoit shift phenomenon occurs and not have an
effect with more flexed knee positions so not interfering with natural rotatory laxities
and avoiding excess tightness.
One of the major concerns regarding proximally fixed lateral extra-articular tenodesis
(LEAT) procedures is that they can potentially increase the ‘constraint’ of the lateral
compartment and that this may have a long term impact on the knee35. To date,
biomechanical studies comparing LEAT procedures have focused on both
proximally-fixed techniques and anatomical ALL reconstructions. There have been no
studies examining the knee kinematics with a distally-fixed lateral extra-articular
augmentation procedure, which may potentially cause less constraint of the lateral
compartment due to the absence of proximal fixation to the femur.
The primary aim of this study was to investigate the effect of a modified Ellison
procedure in restoring native kinematics of the knee following complete sectioning of
the ALC. The secondary aim was to assess the effect of closure of the ITB graft
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harvest site on knee kinematics. The authors hypothesised that a distally-fixed lateral
extra-articular augmentation procedure would restore native knee kinematics
following sectioning of the ALC and that closure of the ITB defect would decrease
rotational laxity of the knee compared to leaving it open.
Materials and Methods
Specimen Preparation
Twelve fresh-frozen (6 female and 6 male; 4 left and 8 right) human cadaveric knees
(mean age 55 years (SD, ±7.5 years; range, 42-64 years) without evidence of prior
injury, abnormalities or surgery, were used in this study. A power calculation based
on a previous studiesy determined that a sample size of 8 would allow the
identification of changes in translation and rotation of 2 mm and 1.2, respectively,
with 80% power and 95% confidence24, 26, 32. Based on the greatest SD of laxity being
±1.1 mm at 60, 12 knees were used to identify potentially small differences.
The specimens were procured from a tissue bank after approval from the local
research ethics committee. Each specimen was thawed for 24 hours before use. The
femur was sectioned 190 mm from the joint line and the soft tissues resected from
the proximal 80 mm, leaving 110 mm of ITB and soft tissue remaining. The tibia was
sectioned 160 mm from the joint line and the soft tissue resected from the distal 60
mm. The fibula was transfixed to the tibia with a tri-cortical screw.
A longitudinal lateral incision was made from Gerdy’s tubercle to the proximal skin
edge and the superficial fat was reflected to expose the ITB. The ITB was identified
and the proximal 20 mm was reinforced with a cotton patch to avoid suture pull out.
Two strands of 2-0 suture (wasn't it #2?) (Ultrabraid, Smith & Nephew Endoscopy,
Andover, Massachusetts) were whip-stitched to the anterior and posterior borders of
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the ITB to facilitate tensioning during robotic testing (Figure 1). This was necessary
due to the fact that in the Ellison technique10 there is no proximal fixation of the ITB,
as it relies upon the dynamic effect of the tensor fasciae latae on the ITB.
Figure 1: A clinical photograph of a right knee. The ITB (black arrow) was identified
and the proximal 20 mm was reinforced with a cotton patch (white arrow) to avoid
suture pull out. Two strands of 2-0 (?) suture (ULTRABRAID (ltrabraid, Smith &
Nephew Endoscopy, Andover, Massachusetts) were whip-stitched on the anterior (A)
and posterior (B) borders of the ITB to facilitate tensioning during robotic testing.
The tibia was cemented into a 60 mm diameter stainless steel pot using
polymethylmethacrylate (Simplex Rapid, Kemdent, UK). The long axis of the cylinder
was perpendicular to the joint surface in the coronal plane and parallel to the long
axis of the bone in the sagittal plane. Having fixed the tibia into the end-effector of the
robot, zero degrees flexion was defined when 3.2 mm guide wires drilled postero-
anteriorly through the tibia and femur at 70 mm and 100 mm from the joint line,
respectively, were parallel. A 60 mm pot was mounted on the base plate with anterior
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and posterior polyethylene tubes passed through it, aligned with the respective
borders of the ITB; these were lubricated with food grade silicone lubricant (CRC,
Horsham, PA) to minimise the friction during dynamic testing. Having cemented the
femur and the tubes with the knee in extension, the ITBT loading sutures were tied in
loops, passed through the appropriate tube and a 30 N tensile load was applied
parallel to the femoral axis 43 (Figure 2A and B).
Figure 2A and B: A clinical photograph of a right cadaveric knee with the femur (F)
mounted on the base plate with the tibia (T) connected to the robotic arm. A: A lateral
view of the specimen demonstrating the iliotibibial band (ITB) under tension with the
sutures running through anterior and posterior polyethylene tubes aligned with the
respective borders of the ITB; B: The sutures fixed to the ITB pass throught the
polyethylene tubes (Red arrow,) which areis lubricated with silicone to reduce friction,
are passed over a pulley (White arrrow) and a fixed to weights applying a 30 N
tensile load (Dashed arrow).
Robotic System
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The robotic biomechanical testing system comprised a 6 degrees-of-freedom (DOF)
robotic manipulator (TX90, Stäubli Ltd, Switzerland) and a 6-axis universal force-
moment sensor (Omega 85, ATI Industrial Automation), with custom-designed tibial
and femoral fixtures (Figure 2 B). The force sensor had a resolution of 0.3 N, 0.3 N
and 0.4 N for X, Y and Z axis forces, respectively, and 0.01 Nm for X, Y and Z axis
torques. The robotic system had a load capacity of 200N and a test-retest SD of ±
0.10 mm and ± 0.12 in translation and rotation between the bone mountings.
Biomechanical Testing
Maintaining 0° knee flexion, the system minimized the forces and torques in the
remaining 5 DOF and recorded a known starting point for the intact knee. From this
point, the force sensor guided the passive path of knee flexion from 0°-90° while
minimizing the five remaining forces and torques. Three cycles of flexion-extension
were performed to minimize error from the inherent stress-relaxation properties of
soft tissue17. As in previous work using this platform32, knee laxity was quantified by
holding a fixed degree of flexion along the passive path whilst imposing a
rotatory/translational displacement and neutralising the remaining four DOF: 90 N for
anterior tibial translation, 5 Nm for internal/external rotation (IR/ER) and coupled
moments of 4 Nm IR with 8 Nm valgus to simulate the pivot-shift laxity21. The
anterior, IR and ER laxities were evaluated at 0, 30, 60 and 90 of flexion3, 13, 26,
47.The simulated pivot shift (SPS) was performed at 0, 15, 30 and 45 of flexion3, 12, 46
and the coupled tibial displacement divided into IR and anterior translation
components.
Transection of Anterolateral Capsule
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Following assessment of the intact state, the knee was held in 90 of flexion. The
lateral fibular collateral ligament (FLCL) was identified deep to the ITB. The ITB was
retracted with a Langenbeck retractor and, using a Beaver blade (Smith & Nephew
Endoscopy, Andover, Massachusetts), the ALC was incised by making an incision
directly anterior to the anterior border of the FLCL; the incision was approximately 20
mm in length and extended from the femoral attachment of the FLCL to the joint line
as previously described6, 9, 23, 25. The release was confirmed using a haemostat
forceps to ensure all fibres had been transected (Figure 3).
Figure 3: A clinical photograph of a left knee specimen with the femur(F) and tibia(T)
marked. The iliotibial band was undermined distal to the fibular collateral ligament
(FCL) (outlined with white dashed-lines) (we need to be consistent re LCL or FCL as
the text uses both – for AJSM I think FCL preferred) and is being elevated with a
scissors(S). A blade was used to transect the anterolateral capsule of the knee distal
to the FCL without violating the ITB a as depicted by the red dashed-line.
Surgical Technique
A modified Ellison procedure was performed in line with current clinical practise
among the authors. The modifications of the technique were that the ALC was
neither repaired or plicated, and the distal end of the strip of ITB was reduced
anatomically and fixed, rather than shifted anteriorly and proximally as advocated in
the original description10. In order to focus purely on the effect that the ALC pathology
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and Ellison procedure had on knee kinematics, the ACL was left intact, to represent a
‘perfect’ ACL reconstruction.
The knee was held in 60 of flexion and neutral tibial rotation. The bony landmarks of
the lateral femoral epicondyle and Gerdy’s tubercle were identified and the posterior
border of the ITB was clearly exposed. An incision was made 10 mm anterior and
parallel to the posterior border of the ITB starting distally at Gerdy’s tubercle and
extending proximally to a point proximal to the origin femoral attachment of the FLCL.
A second parallel incision was made 10 mm anterior to the first to develop a strip of
ITB. At Gerdy’s tubercle a10 mm osteotome was used to remove a sliver of bone
along with the distal insertion of the ITB strip. The ITB strip was mobilised and
reflected in a proximal direction. The FLCL was identified and isolated by making
incisions anterior and posterior to the ligament. The distal end of the ITB strip was
then passed deep to the FLCL from proximal to distal, and secured anatomically to
the bone attachment site using a 5 mm TwinFix titanium anchor with Ultrabraid
(Smith & Nephew Endoscopy Co, Andover, Massachusetts) sutures. When
performed, primary closure of the ITB graft donor site was with a continuous stitch
using a 1-vicryl (Ethicon, Somerville, NJ, USA) suture.
With regard to the secondary aim of the study to assess the effect to closure of the
ITB on knee kinematics, the order of testing of the ‘open’ versus ‘closed’ ITB defect
was randomly selected for each knee.
Statistical Analysis
If Kiron was involved in stats does he need to be an author?
The kinematic data of the intact and deficient states were analysed using a 1-way
paired sample t-test to evaluate the effect of ALC transection. All kinematic data were
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subsequently analysed using a two-factor repeated measures analysis of variance
(RM-ANOVA) with Bonferroni corrections. The two factors assessed were the state of
the anterolateral side of the knee and the flexion angle of the knee. Pairwise
comparisons using a paired t test were performed where appropriate. The level of
significance was set at P < 0.05 for a single comparison. Statistical analysis was
performed in SPSS v 21, IBM Corp.
Results
The data for the intact state, ALC-sectioned state, and ITB-open and ITB-closed
modified Ellison procedures are displayed in Table 1.
Compared to the intact state, transection of the ALC resulted in very small but
statistically significant increases in both internal tibial rotation (IR) (mean increase
approximately 2o) and anterior tibial translation (ATT) (mean change approximately
0.2 mm) when measured as isolated displacements or as part of the simulated pivot
shift (SPS)(P<0.05, apart from coupled ATT in the SPS testing mode).
The modified Ellison procedures gave rise to a significant reduction in the laxity
increases seen with transection of the ALC (Figures 4 and 5). Specifically, there was
a reduction in IR in isolation and during the SPS compared to the ALC-sectioned
state (P<0.05). In some instances the IR was reduced to less than the intact state;
this overconstraint occurred at 30° of knee flexion for both the closed and open
modified Ellision procedures (Figure 4), but only for the closed procedure during the
SPS (Figure 5). Although the closure of the ITB resulted in a statistically significant
reduction in coupled IR during SPS at 15° and 30° compared to the intact state, there
was no significant difference between the open or closed modified Ellision procedure
at any flexion angle.
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Table 1 : Translational and rotational differences relative to the intact state
Flexion Angle
Translation/rotation at intact state (mm/deg)
Differences from intact (mm)
ALC-Sectioned “Closed” Modified Ellison
“Open” Modified Ellison
Anterior Tibial Translation (mm) 0° 2.5 ± 0.6 0.2 ± 0.1* 0.0 ± 0.1 -0.1 ± 0.1‡
30° 4.4 ± 0.6 0.2 ± 0.2* 0.1 ± 0.3 -0.1 ± 0.260° 4.6 ± 1.1 0.2 ± 0.2* 0.2 ± 0.3 0.0 ± 0.290° 3.4 ± 1.0 0.1 ± 0.2* 0.2 ± 0.4 0.1 ± 0.3
Simulated pivot shift: anterior tibial translation (mm) 0° 0.7 ± 0.5 0.1 ± 0.1* -0.3 ± 0.2*‡ -0.4 ± 0.3*‡
15° 1.3 ± 1.8 0.2 ± 0.3* -0.6 ± 0.4*‡ -0.7 ± 0.4*‡
30° 2.1 ± 2.4 0.3 ± 0.5 -0.5 ± 0.4*‡ -0.5 ± 0.4*‡
45° 2.5 ± 2.5 0.3 ± 0.6 -0.4 ± 0.4‡ -0.3 ± 0.4‡
Simulated pivot shift: internal tibial rotation (o) 0° 7.3 ± 4.7 1.1 ± 1.7* 0.1 ± 1.8‡ -0.1 ± 1.8‡
15° 11.3 ± 16.5 1.4 ± 2.0* -1.5 ± 1.8*‡ -1.9 ± 1.4‡
30° 14.6 ± 21.7 2.0 ± 2.3* -1.7 ± 1.8‡ -2.2 ± 1.9‡
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45° 15 ± 24.3 2.4 ± 2.1* 1.2 ± 1.7‡ -1.8 ± 2.4‡
Internal Tibial Rotation (o) 0° 7.1 ± 3.8 1.2 ± 0.5* -0.5 ± 0.9‡ -0.9 ± 0.8*‡
30° 15.6 ± 18.8 1.7 ± 0.7* -1.5 ± 1.3*‡ -1.6 ± 1.4*‡
60° 15.9 ± 21.4 1.9 ± 0.8* -0.6 ± 1.6‡ -0.4 ± 1.5‡
90° 14.4 ± 20.0 1.9 ± 0.7* 0.6 ± 1.4‡ 1.3 ± 0.9*‡
Key: Anterolateral Capsule (ALC), * – statistically significant difference from the intact state (P<0.05), ‡ - statistically significant difference from the ALC-sectioned state
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Figure 4: The difference from the laxity of the intact knee in degrees of tibial internal
rotation at 0°-90 of flexion following ALC-sectioning and a modified Ellison lateral
augmentation procedure (with and without closure of the ITB) during isolated internal
rotation testing. (ALC – anterolateral capsule, * significant difference from the intact
knee - P<0.05, ‡ significant difference from the ALC-sectioned state – P<0.05).
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Figure 5: The difference in degrees of tibial internal rotation between 0°-45 of flexion
following ALC-sectioning and a modified Ellison lateral augmentation procedure (with
and without closure of the ITB) compared to the intact knee during simulated pivot
shift. (ALC – anterolateral capsule, * significant difference from the intact knee -
P<0.05, ‡ significant difference from the ALC-sectioned state – P<0.05).
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Discussion
The main finding of this study was that the modified Ellison procedure was effective
in controlling anterolateral rotatory laxity of the knee. Specifically, the modified Ellison
procedure significantly reduced tibiofemoral motion from the anterolateral complex-
sectioned state and restored kinematics close to the intact state. This study also
found no statistically significant difference in knee kinematics at any flexion angle
whether the ITB defect was closed or left open following a modified Ellison
procedure. To the authors’ knowledge, this is the first biomechanical study to analyse
a distally-fixed lateral extra-articular augmentation procedure using a 6-DOF robotic
system with loading of the ITB.
A number of in vitro biomechanical studies have been performed to assess knee
kinematics following lateral augmentation or reconstructive procedures41. These
studies have focused mostly on proximally-fixed LEAT procedures or ALL
reconstruction and have reported varying results19, 39. A recent controlled laboratory
study by Geeslin et al14, using a 6-DOF robotic system, determined that both a
modified-Lemaire and an ALL reconstruction combined with an ACL reconstruction
resulted in significant reductions in tibiofemoral motion at most knee flexion angles,
although overconstraint was also identified. The current study found a reduction in
isolated internal rotation with the modified Ellison procedure across 0o to 90o flexion.
Similarly, during a simulated pivot shift, the coupled internal rotation was significantly
reduced at 15 and 30 of knee flexion compared to the native knee with a modified
Ellison procedure when the ITB was closed. These findings are similar to the results
of Geeslin et al14 during SPS when the modified Lemaire or ALL reconstruction had a
fixation angle of 30, albeit with less overconstraint at 30 of knee flexion. It is
important to note that there were methodological differences between the two studies
despite using a similar robotic testing model: in the study by Geeslin et al, the distal
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Kaplan fibres were cut as part of their sectioning to of the anterolateral complex, an
ACL reconstruction was performed in conjunction with the LEAT, and there was no
loading of the iliotibial bandITB. In the current study, the ITB was loaded for all
testing states to facilitate testing of a distally-fixed LEAT, which relies upon the
dynamic effect of the ITB. Furthermore, the ACL was left intact in the current study to
represent a ‘perfect’ ACL reconstruction.
It is evident from the literature that a distally-fixed LEAT is less widely used than a
proximally-fixed procedure8, 40. The operative technique of a distal ITB transfer was
described by Ellison in 1979 and used in isolation for the treatment of ACL-deficient
knees with anterolateral rotatory instability10. The technique described was more
extensive than the modified version detailed in the current study. The theory behind
this technique was that the broad-based shape of the strip of ITB preserves the blood
supply to the fascia and the dynamic pull of the tensor fasciae latae and part of the
gluteus maximus10. This theory was disputed by Kennedy et al in an earlier
publication in 1978, who reported relatively poor results using this technique in
isolation or combined with other reconstructive procedures22. The authors claimed
that they could not prove the dynamic function clinically and the subjective results did
not suggest such a function existed. Lipscomb et al, reporting on a series of 75 knees
with chronic ACL deficiency which were treated with a semitendinosus and gracilis
intra-articular ACL reconstruction, posteromedial and lateral capsular ligament
reefing, and an Ellison LEAT, contended that the distally-fixed LEAT did not
adequately prevent anterolateral instability 10, 30, 31, 33. However, no objective evidence
to support this assertion was presented in their studies. They subsequently went on
to use a proximally-fixed Losee procedure, which the authors claimed was static, and
therefore more effective33.
In the context of LEAT, it is important to consider what is the appropriate amount of
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constraint and what represents ‘over-constraint’. The term ‘over-constraint’ is usually
used to imply there will be longterm consequences of osteoarthritis from a procedure.
However authors rarely explain what they men by the term. It could mean loss of
normal flexion range, loss of normal rotational laxity, or increased articular contact
pressure. Biomechanical studies are limited by the fact that they assess the laxity of
a joint at time zero, i.e. immediately after surgery, but fail to account for laxity that
may occur as a result of elongation of tissues over time. In their systematic review,
Slette et al suggested that after a period of initial stability, LEAT procedures have
often shown a tendency to elongate, with return of anterolateral rotatory instability in
the ACL-deficient knee40. However, the studies used to support this claim focused on
LEAT procedures performed in isolation for the treatment of chronic ACL-deficiency2,
7, 22, 40. It is notable that two of these studies included distally-fixed Ellison LEAT
procedures, which is perhaps why this procedure fell out of favour. On the other
hand, Engebretsen et al have shown that when an LEAT is performed in conjuction
with an ACLR, the ACL graft is subjected to less load11.
Kittl et al have demonstrated that the superficial ITB, as well as deep layers, plays an
integral role in controlling anterolateral rotatory laxity25. Based on this finding, the
hypothesis that closure of the ITB defect would result in further restriction of IR due to
anteriorisation of the iliotibial tract was postulated. This study rejected this
hypothesis: closure of the ITB defect was not found to have a significant effect on
rotational laxity. Interestingly, in the original description of the Ellison procedure,
complete closure of the ITB defect was considered an essential step10. On a practical
level, closure of the defect may prevent muscle herniation of vastus lateralis and
makes for a more cosmetically acceptable appearance. Although it would seem
logicalis possible that closure of an ITB defect may also increase the contact
pressure placed on the lateral facet of the patella, this has only been found with a
proximally-fixed ITB graft excessively tensed to 80 N20 thereby causing fixed external
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rotation of the tibia (it did not occur with lower levels of tension and a neutral position
of fixation of the tibia) 20 . It, so would clearly not occur with the minimally-tensed
distally-fixed procedure.
Limitations
The authors acknowledge that there are some limitations of the present study. The
specimens were 55 ± 7.5 years old, higher than the patient group that typically suffer
an ACL rupture, but comparable to previous similar cadaveric studies19, 32. The results
presented are only representative of a ‘time zero’ state and do not take into account
subsequent healing, cyclic loading and rehabilitation. The clinical pivot shift is a
dynamic examination through a range of motion. Using a single robotic manipulator,
this and other studies have not replicated in vivo kinematics but only the coupled
laxities16, 24, 32. On the other hand, the advantages of this study design included
loading of the ITB to simulate any dynamic effect it might have in a lateral
augmentation. Because the optimal ACL reconstruction technique continues to be
debated, leaving the native ACL intact avoided any variations in technique or
prejudice against a particular technique of ACL reconstruction44. It is also important to
note that the differences in tibial anterior translation were less than 1 mm in all cases,
reflecting the dominant role of the ACL, and raising the question of the clinical
relevance of using a lateral procedure to control anterior translation despite the
statistical differences found.
Conclusion
A distally-fixed lateral augmentation procedure can closely restore knee laxities to
native values in an anterolateral capsule-sectioned knee. No significant difference
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was found between closing or leaving the ITB defect open in the modified Ellison
procedure.
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