Anterolateral tenodesis or anterolateral ligament complex reconstruction:

effect of flexion angle at graft fixation when combined with ACL reconstruction

Eivind Inderhaug MD PhD 1, Joanna M Stephen PhD 2,3, Andy Williams FRCS(Orth) 2, Andrew A Amis FREng, DSc 3,4.

1: Haraldsplass Deaconess Hospital, Bergen, Norway

2: Fortius Clinic, London, UK

3: Biomechanics Group, Mechanical Engineering Department, Imperial College London, London, UK.

4: Musculoskeletal Surgery Group, Department of Surgery & Cancer, Imperial College London School of Medicine, London UK.

Study performed at Imperial College London.

Correspondence to: Prof Andrew Amis, Biomechanics Group, Mechanical Engineering Department, Imperial College London, London SW7 2AZ, UK; a.amis@imperial.ac.uk.

Acknowledgements:Dr Inderhaug was supported by a fellowship grant from the Bergen Regional Health Authority. Dr Stephen was supported by the Fortius Clinic. The laboratory work was supported by a grant, euipment loan and donation of surgical devices from Smith & Nephew Ltd, which was paid to a research account of Imperial College London. The authors also thank Dr Bertrand Sonnery-Cottet, of Lyon, France, for visiting the laboratory to demonstrate his surgical methods; he also provided the illustrations of the surgical procedures (Figures 2 and 3).

Blinded text in manuscript:Line 125: The ethics permit: ICHTB HTA licence 12275, REC Wales 12/WA/0196.Line 126: tissue bank: Science Crae, Phoenix, AZ, USA.

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ABSTRACT:

Background: Despite numerous technical descriptions of anterolateral procedures,

there is limited knowledge regarding the effect of knee flexion angle during graft

fixation.

Purpose: To determine the effect of knee flexion angle during graft fixation on

tibiofemoral joint kinematics for a modified Lemaire tenodesis, or an anterolateral

ligament complex reconstruction, combined with ACL reconstruction.

Study design: Controlled laboratory study.

Methods: Twelve cadaveric knees were mounted in a test rig with kinematics

recorded from 0° - 90°. Loads applied to the tibia were: 90-N anterior translation, 5-

Nm internal tibial rotation, and combined 90-N anterior force and 5-Nm internal

rotation. Intact, ACL-deficient and combined ACL plus anterolateral-deficient states

were tested, and then ACL reconstruction was performed and testing was repeated.

Thereafter modified Lemaire tenodeses and anterolateral ligament procedures with

graft fixation at 0 °, 3 0 ° and 6 0 ° knee flexion and 20-N graft tension were performed

combined with the ACL reconstruction - and repeat testing was performed

throughout. Repeated-measures ANOVA and Bonferrroni-adjusted t tests were used

for statistical analysis.

Results: In combined ACL and anterolateral-deficiency, isolated ACL reconstruction

left residual laxity for both anterior translation and internal rotation. Anterior

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translation was restored for all combinations of ACL and anterolateral procedures.

The combined ACL reconstruction and ALL procedure restored intact knee

kinematics when fixed in full extension, but when fixed in 30 ° and 60 ° left residual

laxity in internal rotation (P=0.043). The combined ACL reconstruction and modified

Lemaire procedure restored internal rotation regardless of knee flexion angle at graft

fixation. When comparing the combined ACL reconstruction and lateral procedure

states to the ACL-only reconstructed state, a significant reduction in internal rotation

laxity was seen with the modified Lemaire tenodesis, but not with the ALL procedure.

Conclusion: In a combined ACL and anterolateral injured knee the modified Lemaire

tenodesis combined with ACL reconstruction restored normal laxities at all angles of

flexion for graft fixation (0°, 30° or 60°), with 20-N tension. The combined ACL and

ALL procedure restored intact knee kinematics when tensioned in full extension.

Clinical relevance: In combined anterolateral procedure plus intraarticular ACL

reconstruction, the knee flexion angle is important when fixing the graft. A modified

Lemaire procedure restored intact knee laxities when fixed at 0°, 30° or 60° flexion.

The ALL procedure restored normal laxities only when fixed in full extension.

Key terms: Anterior cruciate ligament reconstruction, ACL, lateral extraarticular

tenodesis, LET, Lemaire, anterolateral ligament, ALL, biomechanics.

What is known about this subject: Clinical and radiological findings suggest that

anterolateral structures can be injured at the time of the ACL tear. This provides a

rationale for combining extraarticular procedures with the intraarticular ACL

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reconstruction in selected cases. Although numerous descriptions of anterolateral

techniques exist, there is no consensus on how graft fixation should be performed to

best restore native knee laxity.

What this study adds to existing knowledge: If performing a modified Lemaire

tenodesis in combination with an ACL reconstruction in a combined ACL and

anterolateral injured knee, native knee kinematics can be restored if the graft is fixed

at 0°, 30° or 60° of knee flexion. If, however, performing an ALL procedure, the most

favorable kinematics were found if the graft was tensioned at full extension.

INTRODUCTION:

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Extra-articular procedures have historically been used in isolation as surgical

treatment for ACL deficiency 12,27,30. With arthroscopic assistance, intra-articular ACL

reconstruction was popularized and quickly became the primary treatment due to the

less invasive approach and improved clinical outcomes 6,8. Some studies have,

however, reported that combining extra-articular procedures with the intra-articular

ACL reconstruction can improve outcomes as compared to an isolated ACL

reconstruction 29,32,36,47. Recently there has been renewed interest in the importance of

anterolateral structures in controlling anterolateral rotational instability (ALRI) of the

knee 16,19,35,41. Biomechanical studies provide a rationale for this additional effect

observed when performing anterolateral procedures in conjunction with ACL

reconstruction 2,17,44.

Numerous extra-articular techniques have been described in the literature 4,12,18,26,27.

While many of these have been abandoned, some - such as the Lemaire tenodesis -

are still in use 9,30,46. More recent techniques, based on the anterolateral ligament,

have been described as less invasive and more anatomic than traditional

approaches, and have provided promising preliminary clinical data 43. Several

biomechanical studies have explored technical aspects of potential anterolateral

procedures 22,31,44. A graft path deep to the LCL and with the femoral graft insertion in

the area proximal and posterior to the lateral epicondyle has been shown to have a

desirable length change pattern with knee flexion 22.

Although the understanding of extra-articular techniques has been advanced by

recent studies, there are still unanswered questions for surgeons who want to add

such procedures to intra-articular ACL reconstruction. An important issue is the angle

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of flexion that should be used when tensioning and fixing the graft. Technical

descriptions diverge in their recommendations and there is no clear consensus on

protocols. The current study therefore aimed to investigate the effect of knee flexion

angle during graft fixation when performing a modified Lemaire tenodesis - that had

previously been found to have favorable kinematic effects 17 - and a recently

described anterolateral ligament complex (ALL) procedure 41 , in combination with an

ACL reconstruction in a knee with a combined ACL and anterolateral injury.

The underlying hypotheses for the current study were: (1) that a combined ACL and

anterolateral lesion would increase knee laxity as compared to an isolated ACL

injury. (2) That an isolated ACL reconstruction could not restore intact knee

kinematics in a combined ACL and anterolateral injured knee, (3) that there would be

no difference in kinematics between the intact knee and the combined ACL

reconstruction/modified Lemaire tenodesis tensioned at 0°, 30° or 60° of knee flexion,

and (4) that there would be no difference in kinematics between the intact knee and

the combined ACL reconstruction/anterolateral ligament procedure tensioned at 0°,

30° or 60° of knee flexion.

MATERIALS AND METHODS:

Preparation of specimens

After ethical approval (blinded for review), 12 fresh-frozen cadaveric knees were

obtained from a tissue bank (blinded for review). Mean age was 49 (range 28-62: 5

right and 7 left knees, 6 male, 6 female). Specimens were stored at -20°C and

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thawed for 24 h before testing. During experiments they were kept moist using water

spray. Soft tissues were removed further away than 15 cm from the joint and both

tibia and femur were cut 20 cm from the joint line. Skin and subcutaneous fat were

removed. An intramedullary rod was cemented into the femur using poly

methylmethacrylate bone cement.

The femoral rod was secured in a six degree-of-freedom rig at 6° valgus to align the

mechanical axis of the knee to the test rig (Figure 1) 49. A tibial pot with a 50 cm axial

extending rod was cemented onto the distal tibia. The rig allowed passive knee

motion from 0° to 100° of flexion by moving the femur whilst the tibia hung vertically.

A Steinman pin was drilled mediolaterally through the tibia so that a semi-circular

hoop could be mounted anteriorly. Using the hoop, anterior drawer force could be

applied to the proximal tibia by a string, pulley and weight system without restricting

the coupled tibial rotation. A 20 cm polyethylene disc was secured to the tibial rod

and hanging weights applied via a pulley and string system to opposite poles of the

disc allowed tibial internal rotation torques to be applied. A clamping device was also

attached to the central rod so that the tibia could be returned to and held in its neutral

position at any time during testing. The neutral position was marked at the start of the

experiment in three angles of knee flexion (0°, 30° and 60°).

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Figure 1 – The knees were mounted in the six-degree of freedom rig and optical

trackers were securely drilled into bone. A pulley and weight system was used to

apply external loads during the kinematic testing from 0° to 90° of knee flexion.

Kinematic measurements

Optical tracking was performed using a Polaris camera system (NDI, Waterloo,

Ontario, Canada) and BrainLab reflective Markers (BrainLab, Feldkirchen, Germany)

securely mounted to the tibia and femur (Figure 1). By digitizing fiducial markers

attached to anatomic landmarks on tibia and femur a reference coordinate system

was created. The most medial and lateral parts of the tibial plateau and the anatomic

axis (the distal extension rod) were used to create the tibial plane. For the femoral

plane a transverse axis from the medial to the lateral epicondyles and the proximal

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end of the intramedullary rod were used. The kinematic data were retrieved using an

established method 7,17,23. Zero degrees of flexion was defined as the position where

the tibial and femoral rods were parallel as seen in the sagittal plane. Anterior

translation was calculated as the perpendicular distance from the midpoint of the

femoral epicondylar axis to the tibial coronal reference plane, and motions were

described as tibial motion relative to the femur. The translational accuracy of the

tracking system was ± 0.04 mm 20 and the rotational accuracy was ± 0.03 °.

Surgical technique

The same experienced orthopaedic surgeon performed all surgery with the knee

mounted in the test rig. An initial arthroscopy was performed to ensure no damage to

cruciate ligaments, menisci, cartilage or other intraarticular structures. After testing

the intact state, the ACL was resected arthroscopically. After testing the ACL injured

state, an anterolateral lesion was created. A choice was made to create a “worst

case scenario” (including both the ALL and capsulo-osseous fibers of the ITB) as the

baseline for testing of anterolateral procedures. A 50 mm incision was made in the

mid-substance of the ITB along its fibers in a distal to proximal direction starting at

Gerdy’s tubercle. Through this incision the lateral (fibular) collateral ligament (LCL)

was identified and preserved. The mid-substance fibers of the ALL were identified

and a cut was made anterior and parallel to the LCL from the lateral epicondyle to the

tibiofemoral joint line to transect the ALL and the capsule 11,19. Proximal to the LCL

the retrograde, supracondylar and proximal femoral attachments of the ITB were

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identified and transected 21. The combined ACL and anterolateral injured knee was

then tested.

The arthroscopic ACL reconstruction was performed with a 10 mm bone-patellar

tendon-bone autograft harvested from the tested knee. The graft was positioned in a

central tibial to an anteromedial fiber bundle femoral attachment position. The

femoral bone block was fixed with a 7x25 mm interference screw (RCI, Smith &

Nephew, Andover, USA) and the tibial bone block was fixed with a 9x35 screw (RCI,

Smith & Nephew, Andover, USA). The knee was held at 30° of flexion and the graft

was tensioned with an 80 N manual pull, using a tensiometer. Secure back-up

fixation was performed on both the tibia and the femur by tying the bone block

sutures to cortical bone screws.

The modified Lemaire tenodesis and the ALL procedure were chosen due to their

recent popularity, and both were used in each knee. The former has been shown to

restore intact knee kinematics in a combined injured knee 17, while the latter was the

first ALL reconstruction used in a large clinical series 43 . To avoid any bias due to

tissue deterioration and order of procedures, a study administrator (not taking part in

surgery) determined a variable order that was only given to the surgeon throughout

the study. At the start of each procedure the knees were brought back to and held in

their native neutral position at the relevant flexion angle, using a clamping device. A

former study investigating the effect of graft tensioning protocols found that 20 N

tension gave optimal restoration of native knee kinematics and was therefore applied

in the current study 17 . Braided sutures (Ultrabraid, Smith & Nephew, Andover, USA)

were used to whipstitch the free ends of all grafts so that these could be passed to

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the medial side of the knee through a full-length femoral tunnel. A hanging weight

was thereafter applied to allow 10 cycles of flexion to extension to pre-condition the

graft before the final fixation was performed. An 8x25 mm interference screw (RCI,

Smith & Nephew, Andover, USA) was used . Additional secure back-up fixation was

achieved by tying the sutures to cortical bone-screws on the medial femoral (for the

Lemaire) and tibial (for the ALL procedure) cortex.

1. The ALL procedure was performed in accordance with a previously described

technique using a 2-strand gracilis autograft in an inverted V configuration 42.

The distal ends were fixed into two pre-drilled 7 mm tunnels positioned

between Gerdy´s tubercle and the fibular head on the tibia using interference

screws (Figure 2). The graft passed superficial to the LCL and was secured in

an 8 mm femoral tunnel using an 8x25 mm interference screw. The femoral

tunnel was placed 8 mm proximal and 5 mm posterior to the lateral

epicondyle, corresponding to the femoral ALL attachment and the insertion

site of the Lemaire procedure 11,19,22,26.

Figure 2 - The ALL procedure was performed using a gracilis tendon autograft fixed

with interference screws in two graft tunnels between Gerdy´s tubercle and the fibular

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head and one screw in a graft tunnel positioned proximal and slightly posterior to the

lateral epicondyle 9,26,31.

2. A modified Lemaire procedure was performed using a 15 x 100 mm central

strip of the ITB 9,17,26,30 (Figure 3). The tibial attachment of the ITB was kept

intact. The graft was routed deep to the LCL to the same femoral tunnel as

described for the ALL procedure. An 8x25 mm interference screw was used

for fixation, plus backup sutures.

Figure 3 - The modified Lemaire tenodesis was performed using a mid-strip of the

ITB that was left attached to the Gerdy’s tubercle, tunnelled deep to the LCL and

fixed in the same femoral tunnel as for the ALL procedure using an interference

screw.

Testing protocol

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The kinematic data were collected from three cycles of passive knee flexion from 0° -

90°. The following states were tested: (1) intact, (2) ACL transected, (3) combined

ACL and anterolateral lesion, (4) ACL reconstruction, (5) ACL reconstruction

combined with an ALL procedure, (6) ACL reconstruction combined with a modified

Lemaire procedure. States (5) and (6) were repeated with the graft fixed at 0°, 30°, or

60° of knee flexion. States (1) to (4) were tested in that order, whilst states (5) and

(6), and the order of flexion angles at graft fixation, were randomized throughout the

study.

Each state (1) to (6) was tested from 0° - 90° of knee flexion without any external

loads and with the following loads applied: 90 N anterior drawer force, 5 Nm internal

tibial torque and 90 N anterior drawer/5 Nm internal tibial torque combined. Again,

this order of testing was randomized.

Data analysis

An a priori alpha value of 0.05 was used to denote statistical significance, giving a P

value of 0.013 after Bonferroni correction to allow for 4 comparisons. With a

hypothesized effect size of d=1.25, 12 specimens would ensure a statistical power of

80% and were therefore included in the study 14. MatLab scripts (MathWorks Inc.,

Natick, Ma, USA) were used for data processing and for calculating mean tibial

translations and rotations at 10° intervals through 0° - 90° of knee flexion. SPSS

version 22.0.0 (IBM Corp, Armonk, NY) was used for statistical analysis. The Shapiro

Wilk test was applied to assess normality of the data sets. As normality was

confirmed, two-way repeated-measures analyses of variance (RM ANOVAs) were

used to compare (1) the intact state with both ACL cut and ACL plus anterolateral cut

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states, (2) the isolated ACL reconstructed state with the intact knee, (3) the intact

state with the three ALL procedures (fixed at 0°, 30° and 60° knee flexion), (4) the

intact knee with the three Lemaire tenodeses (fixed at 0°, 30° and 60° knee flexion),

and (5) the laxity of the knee with an isolated ACL reconstruction was compared with

the laxity after each of the combined procedures. Paired t tests with Bonferroni

corrections were applied when differences across test conditions were found to

examine the hypotheses defined in the introduction.

RESULTS:

The effect of ACL and combined ACL plus anterolateral lesions

Both sectioning the ACL and cutting the anterolateral structures resulted in significant

increases in anterior tibial translation in response to the anterior draw force (Figure

4), internal rotation in response to the internal torque (Figure 5), and both effects in

response to the combined anterior force and internal torque, as compared to the

intact knees (All: P<0.001).

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0° 10° 20° 30° 40° 50° 60° 70° 80° 90°0

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16 Intact ACL Def Comb Def ACL Recon

Flexion Angle (degrees)Ante

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(m

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Figure 4 - The response to 90 N anterior drawer force for intact knees, ACL cut,

combined ACL and anterolateral cut and an ACL reconstructed state (N=12; Mean +

or - SD).

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25 Intact ACL Def Comb Def

ACL Recon

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Figure 5 - The response to 5 Nm internal torque for intact knees, ACL cut, combined

ACL and anterolateral cut and an ACL reconstructed state (N=12; Mean + or - SD).

The effect of an isolated ACL reconstruction in the combined injured knee

Increased laxity persisted following an isolated ACL reconstruction, when compared to the

intact state, with increased tibial translation (P=0.035, Figure 4), internal rotation (P=0.001,

Figure 5) and combined internal rotation and anterior translation (P=0.025)

The effect of combining ACL reconstruction and anterolateral procedures on

tibiofemoral kinematics

After combining the ACL reconstruction with the ALL procedures (fixed at 0 °, 30° or

60° of flexion) , there were no differences in the response to an anterior draw force

(Figure 6) or combined anterior draw and internal rotation torque compared to the

intact knee state (both: P>0.05). For an isolated tibial internal rotation torque, an

overall residual increase of rotational laxity was observed (P=0.043 by RM-ANOVA)

(Figure 7). When the angle of graft fixation was examined by post-testing, a

significant difference was not found between the intact knees and the ALL procedure

tensioned at full extension (P>0.05). If the ALL procedure was fixed at 30° knee

flexion, pairwise testing found increased internal rotation, at 20° and from 50°- 70°

degrees of flexion (P=0.005-0.012). The ALL procedure fixed at 60° had an increased

rotation at 60° - 90° degrees of flexion (P=0.001-0.006). When comparing the laxities

of the combined ACL and ALL procedures to those of the ACL-only reconstructed

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state, significant reductions in internal rotation from adding the ALL procedures were

not found (P>0.05).

0° 10° 20° 30° 40° 50° 60° 70° 80° 90°1

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8Intact ALL 0 degrees ALL 30 degreesALL 60 degrees

Flexion Angle (degrees)

Tran

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Figure 6 - The response to 90 N anterior drawer force for intact knees and combined

ACL and ALL procedure fixed at 0°, 30° or 60° of knee flexion (N=12; Mean + or -

SD).

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Figure 7 - The response to 5 Nm internal torque for intact knees and combined ACL

and ALL procedure fixed at 0°, 30° or 60° of knee flexion (N=12; Mean + or - SD).

Circles denote statistical difference (P<0.05) from intact knees.

After combining the modified Lemaire procedures (tensioned at 0 °, 30° and 60° of

flexion) with the ACL reconstruction, there were no differences in response to

anterior draw force as compared to the intact knees (P>0.05) (Figure 8). Neither were

any differences in the response to the internal torque (Figure 9) or internal torque and

anterior force combined between intact knees and any of the Lemaire procedures

(tensioned at 0 °, 30° and 60° of flexion) found (both: P>0.05). When comparing the

combined ACL and Lemaire states to the ACL-only reconstructed state, significant

reductions in knee internal rotation laxity were found (P<0.05)

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0° 10° 20° 30° 40° 50° 60° 70° 80° 90°1

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8Intact Lemaire 0 degrees

Flexion Angle (degrees)

Tran

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(mm

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Figure 8 - The response to 90 N anterior drawer force for intact knees and combined

ACL and modified Lemaire procedure fixed at 0°, 30° or 60° of knee flexion (N=12;

Mean + or - SD).

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0° 10° 20° 30° 40° 50° 60° 70° 80° 90°5

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21Intact Lemaire 0 degrees

Lemaire 30 degrees Lemaire 60 degrees

Flexion Angle (degrees)Inte

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Figure 9 - The response to 5 Nm internal rotation torque for intact knees and

combined ACL and modified Lemaire procedure fixed at 0°, 30° or 60° of knee flexion

(N=12; Mean + or - SD)

DISCUSSION:

The main finding in the current study is the restoration of intact knee laxity in a

combined ACL and anterolateral injured knee when performing anterolateral

procedures along with the intraarticular ACL reconstruction. This study confirmed that

an isolated ACL reconstruction could not restore native knee laxity in the presence of

the combined ACL plus anterolateral lesions. The results provide greater insight

regarding the performances of the anterolateral procedures in relation to the angle of

knee flexion during graft tensioning and fixation. The modified Lemaire tenodesis

restored native knee laxity regardless of the angle of knee flexion (0°, 30° or 60°) for

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graft tensioning and fixation. Native knee laxity was also restored by an ALL

procedure when the graft was tensioned in full knee extension. The current findings

largely support our initial hypotheses: (1) The combined ACL and anterolateral lesion

caused an increase knee laxity as compared to an isolated ACL injury; (2) The

isolated ACL reconstruction could not restore intact knee kinematics in a combined

ACL and anterolateral injured knee; (3) There was no difference in kinematics

between the intact knee and the combined ACL reconstruction/modified Lemaire

tenodesis tensioned at 0°, 30° or 60° of knee flexion; (4) There was no difference in

kinematics between the intact knee and the combined ACL

reconstruction/anterolateral ligament procedure tensioned at 0° of knee flexion,

although residual internal rotation laxity persisted when the ALL procedure was

tensioned at greater angles of knee flexion. These findings highlight how details of

the surgical procedure, such as the knee flexion angle at graft tensioning, influence

results when addressing a combined ACL and anterolateral injury 28,45 . A

biomechanical factor which helps to explain the efficacy of the modified Lemaire

procedure is the relatively anterior attachment to Gerde’s tubercle, which gives a

more efficient force vector to resist anterior movement of the lateral aspect of the

tibia than if the graft is attached towards the head of the fibula 2 .

Given that anterolateral structures are believed to have a role in ALRI, it is

reasonable to think that graft fixation near full knee extension (the flexion angle

where the pivot shift can be elicited) may be favorable when aiming to restore normal

knee kinematics. Lemaire´s original tenodesis adhered to this principle as it was

tensioned at 30° knee flexion 26. The Lemaire procedure has been modified in later

publications, but few of the authors have reported angle of flexion at graft fixation

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9,25,30. A recent description by Wagner et al. differed from Lemaire by fixing at 70°, but

no clear rationale was given for the use of a higher angle of flexion 48. There has

been little biomechanical study of the Lemaire procedure. For the relatively new ALL

procedures most descriptions also recommend fixation at the traditional 20° - 30°

knee flexion 40,42. Sonnery-Cottet et al. reported tensioning and fixation in full

extension in their follow-up evaluation of 92 patients treated with a combined ACL

and anterolateral approach 43. On the other hand Nitri et al. have suggested using 75°

knee flexion - on the basis of findings from a biomechanical study by Parsons et al.

31,33. In that latter study the ALL was described as a primary stabilizer in internal

rotation of the tibia at high flexion angles. These results have, however, later been

disputed due to the authors removing the ITB prior to kinematic testing 34. Since a

later study has shown that the ITB is the most important restraint for tibial internal

rotation 21, not accounting for this structure could likely over-estimate the importance

of the ALL. Translation of these results to a clinical setting should therefore be done

with caution.

A number of studies have investigated the biomechanical performance of

anterolateral tenodeses in combination with intraarticular ACL reconstruction

3,5,13,17,31,37,44. Of these only three have evaluated the procedures used in the current

work. Spencer et al. performed an ALL reconstruction using braided suture tape and

a modified Lemaire procedure using a 10 mm strip of the ITB 44. The ALL procedure

used in that study was unable to restore the intact internal rotation pattern whilst the

Lemaire procedure caused significant improvements in rotational control; these

findings are consistent with the present results in spite of differences in technique.

Another study compared the kinematic patterns of several anterolateral procedures

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including a modified Lemaire and an anatomic ALL-reconstruction 17. In that study the

optimal graft tension was investigated by applying several forces at graft fixation. The

Lemaire tenodesis restored intact knee kinematics with both 20N and 40N of graft

tensioning. The ALL reconstruction left residual laxity, even when 40N graft tension

was applied. Schon et al. investigated the effect of flexion angle during fixation of an

anatomic ALL graft on knee kinematics when combined with an ACL reconstruction

38. The ALL graft was tensioned stepwise from 0° to 90° of knee flexion and the

kinematic response was assessed. Their main finding was overconstraint of internal

rotation for all the graft fixation angles, but a relatively high 88 N graft tension was

used in that study. The use of 20 N graft tension in the present study follows earlier

work 17, and it did match the native knee laxity for the modified Lemaire procedure

with fixation at any of the knee flexion angles investigated (0o – 60o). The ALL

procedure, with a two strand configuration rather than the single strand used in

previous studies, restored intact knee kinematics when fixed in full knee extension –

but led to incomplete control of internal rotation if fixed in flexion. It was observed that

knee flexion-extension caused one or other of the separate arms of the ALL graft to

slacken, so that it was less effective for resisting tibial internal rotation; this suggests

use of a more robust single-strand graft. Although the long-term effects on cartilage

health of adding an anterolateral procedure are unknown 10,15, the authors suggest

that procedures that can restore knee laxity using lower graft tensions (such as 20 N)

should be a safer choice for surgeons wanting to address anterolateral injuries,

because a higher tension may alter knee kinematics and elevate articular contact

pressure.

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The current study found that the modified Lemaire procedure had close to normal

kinematic performance independent of the three fixation angles used for graft

tensioning (0°, 30° and 60°). A explanation for these results might be found in studies

looking at length change patterns of anterolateral procedures 22,24,39. Kittl et al.

investigated both anatomic structures and such potential surgical procedures

throughout the knee range of motion 22. Although the tested structures/procedures

had a wide variety of elongation patterns, two factors did reliably predict relatively

“isometric” graft behavior: a graft path deep to the LCL and femoral graft insertion

proximal/posterior to the lateral epicondyle. A key for these findings is thought to be a

“pulley effect” of the LCL that facilitates the favorable graft behavior. A graft path

such as the modified Lemaire tenodesis had a length change of less than 5% through

0° - 90° of knee flexion. This supports the current results and illustrates that the

choice of anterolateral procedure, the graft tension, and the knee flexion angle at

which the graft is tensioned and fixed, are all factors that influence time-zero

kinematics.

Limitations of this study include the reporting of results at time zero after surgery.

Postoperative effects of tissue regeneration and rehabilitation might affect graft

tension and knee laxity over time and are not accounted for in a laboratory setting.

Also, since the study was performed on unloaded knees, it is hard to predict how the

results translate into a fully weight-bearing knee facing the loads of vigorous sports.

The current anterolateral injury involved both the anterolateral ligament and the deep

proximal attachments of the ITB, and also split along the ITB. This might be a “worst

case scenario” as compared to anterolateral injuries seen in a clinical setting but

represents a base case scenario that is ideal if aiming to demonstrate performance of

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anterolateral procedures. A pilot study for a previous experiment 17 showed that the

longitudinal ITB split did not affect the kinematics, so it would not have

disadvantaged the ALL procedure (which is performed minimally-invasively in-vivo) in

the present work. While the analyses found many significant effects arising from the

surgical procedures, the variability among the knees is reflected by the large

standard deviations about the mean behavior. The range from loose to tight knees is

a commonplace clinical observation – some knees which are ACL-deficient can

remain tighter than other intact knees 1,17 – but this normal between-knees variability

was allowed-for by using the repeated-measures statistical analysis. We therefore

believe that the study gives a realistic time-zero picture of procedures with different

graft tensioning angles and that these results might be useful for surgeons deciding

to combine anterolateral procedures with intra-articular ACL reconstruction. Noting

the limitations of working in-vitro, future work should focus on clinical outcomes after

combined ACL reconstruction and anterolateral procedures to help to define

subpopulations of patients who will benefit from the combined approach.

Conclusion

In the combined anterolateral and ACL-injured state, the isolated ACL reconstruction

failed to restore normal kinematics and left persistent increased tibial translation and

internal rotation as compared to the intact state. The modified Lemaire tenodesis

combined with ACL reconstruction restored normal knee kinematics regardless of the

angle of flexion at which the graft was tensioned and fixed, so the graft can be

tensioned at the knee flexion angle of preference (from 0° to 60°). This finding relied

on the use of a 20 N graft tensioning protocol with the tibia held in neutral rotation, to

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avoid under- or over-constraint. The two-strand ALL procedure combined with ACL

reconstruction replicated the normal knee kinematics when fixed in extension but

failed to restore internal rotation when fixed in flexion.

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