2015 ISAKOS Biennial Congress ePoster #1133

Biomechanical Analysis of Anatomic Anterolateral Ligament Reconstruction of the Knee

Luke Spencer, MBBS, FRACS (Orth), FAOA, Lake Wendouree, VIC AUSTRALIA
Timothy A. Burkhart, PhD, Toronto, Ontario CANADA
Shaneel Deo, MD, London, ON CANADA
Michael Tran, MD, FRCSC CANADA
Alex Rezansoff, MD, FRCSC, Calgary, AB CANADA
Scott Caterine, Masters Candidate, London, ON CANADA
Alan Getgood, MD, FRCS(Tr&Orth), DipSEM, London, ON CANADA

Fowler Kennedy Sport Medicine Centre, London, Ontario, CANADA

FDA Status Not Applicable

Summary: Biomechanical analysis shows the ALL is a secondary stabiliser to the ACL in controlling anterolateral rotation and simulated pivot shift tests.

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Abstract:

- Background: - Recent studies have confirmed the presence of the anterolateral ligament (ALL) through MRI, anatomical dissection and histochemical analysis. It has been suggested that the ALL may play a role in anterolateral roatatory stability of the knee. To date, no biomechanical studies exist which test this theory. Numerous procedures have been described for the purpose of controlling anterolateral rotatory instability, yet concerns have been raised over the non-anatomic nature of these reconstructions.

Purpose

- 1) to confirm the role of the ALL in controlling anterolateral rotational instability; 2) compare the kinematic profile of an anatomic ALL reconstruction to a Lateral Extra-articular tenodesis (LET).

Methods

- A custom designed hip and knee joint simulator was used to test eleven cadaveric knee specimens in the following sequence: i) ACL intact; ii) partial ACL injury (ACLant) – anteromedial bundle of ACL sectioned; iii) complete ACL sectioned (ACLfull); iv) ALL sectioned (ALLsec); v) anatomic ALL reconstruction (ALLAnat); LET reconstruction (LET). Rigid marker clusters were attached to the tibia and femur to track the motion of the tibia with respect to the femur via joint coordinate systems. For each condition, a 5Nm and 10Nm internal/external and varus/valgus moment was applied to the tibia through a six degree of freedom load cell respectively, at varying degrees of knee flexion from 0° to 90° flexion in 15° increments. Four independent clinicians also performed and graded the pivot shift test and Lachman test. A two-way repeated measures ANOVA was used to analyze kinematic data with alpha set at 0.05 for all tests.

Results

- Throughout the range of motion, only the ALLsec condition resulted in a statistically significant increase in internal rotation and anterior translation from the intact state (p<0.001 and p<0.001 respectively). A significant increase in the pivot shift grade was found following sectioning of the ALL. As an objective surrogate measure of the pivot shift, internal rotation in full extension was significantly increased from the ACLintact condition (5.13°± 3.04°) to the ACLfull condition (6.67°± 2.48°), and then from ACLfull to the ALLsec condition (8.89 °± 3.83°) (both p<0.001). A trend in increasing anterior translation existed across all sectioning groups but statistical significance was not reached. Anatomic ALL reconstruction (ALLAnat) did not result in a significant reduction in internal rotation in extension (9.07°± 3.81°) or anterior translation (1.30mm ±0.90mm). Following LET, a non-statistically significant decrease in internal rotation was noted, however, a significant decrease in anterior translation was noted (0.75mm ±0.20mm) compared to the ACLfull (1.20mm±0.23mm) and the ALLsec (1.12mm±0.78mm) conditions (p=0.031).

Discussion

- This study confirms the important role of the ALL, in combination with the ACL, in providing anterolateral rotatory stability of the knee. High-grade pivot shift would be suggestive of combined ACL and ALL injury.
Only the LET was found to restore internal rotation and anterior translation closer to the ACL intact state, suggesting that the orientation of the LET graft has both ALL and ACL kinematic profiles. Further research is required to show if an LET or ALL reconstruction can assist in improving ACL reconstruction outcome.