2017 ISAKOS Biennial Congress ePoster #1037

 

The Biomechanical Role of the Anterolateral Ligament of the Knee in the Context of Anterior Cruciate Ligament Reconstruction

Ran Thein, MD, Ramat-Gan ISRAEL
James Boorman-Padgett, BS, New York, NY UNITED STATES
Jelle P. van der List, MD, PhD, Amsterdam NETHERLANDS
Danyal H. Nawabi, MD, FRCS(Orth), New York, NY UNITED STATES
Thomas L. Wickiewicz, MD, New York, NY UNITED STATES
Carl W Imhauser, PhD, New York, NY UNITED STATES
Andrew D. Pearle, MD, New York, NY UNITED STATES

Hospital for Special Surgery, New York, NY, UNITED STATES

FDA Status Not Applicable

Summary

On average, ACL reconstruction restores the motions of the native knee closely enough that the ALL does not carry higher loads during most clinical exams of knee stability. However, in the presence of an imperfect ACL reconstruction, there might be an increased role of the ALL in stabilizing internal rotation and this may increase loads on the ACL graft during applied rotatory loads at 30° flexion

Abstract

Introduction

The biomechanical role of the anterolateral ligament (ALL) of the knee as a secondary stabilizer in the anterior cruciate ligament (ACL) - competent and deficient knees has been recently described. However, limited biomechanical data are available quantifying the biomechanical influence of the ALL in the ACL-reconstructed knee. Therefore, we posed three research questions: 1) Are loads borne by the ALL in the setting of ACL reconstruction different than the loads born by the ALL in the ACL-competent knee; 2) does ALL deficiency with ACL reconstruction alter knee kinematics and 3) does deficiency of the ALL change the loads carried by the ACL graft during simulated stability exams?

Methods

Eight fresh frozen human cadaveric knees were acquired for testing. The tibia of each specimen was mounted to a robotic manipulator equipped with a universal force-moment sensor. Clinical Lachman (30°), anterior drawer (90°) and pivot shift (15° & 30°) exams were simulated. The motions of the tibia relative to the femur were determined with an intact ACL, after an autograft bone patellar tendon bone ACL reconstruction and after the ALL was sectioned from its tibial attachment.

Results

After ACL reconstruction, anterior translation during a simulated Lachman exam was 2.5 mm higher on average than in the intact knee (38% increase). The average load carried by the ALL differed from the native knee in both the simulated Lachman test and applied rotatory loads by less than 6.2± 7.1 N and 6.1 ± 8.3 N, respectively (p = 0.096 and p = 0.101, respectively). In the anterior drawer test the load carried by the ALL was 8.6 ± 8.8 N higher in the ACL-reconstructed knee than in the ACL-intact knee (p = 0.041). In the ACL-reconstructed knee, average specimen-specific increases in anterior tibial translation in the anterior drawer test relative to the ACL-competent knee differed by less than 0.6 ± 0.7 mm (p = 0.080). Under applied rotatory loads at 15° and 30° flexion, in the ACL-reconstructed knee, average specimen-specific increases in anterior tibial translation relative to the ACL-competent knee differed by less than 0.3 ± 0.9 and 0.8 ± 1.1 mm, respectively (p >0.05). Under applied rotatory loads, a 1.8 ± 1.5° larger increase in internal rotation was observed in ALL-deficient knees compared to ALL-intact knees at 30° flexion (p = 0.011). Small increases in graft loads were observed in every test with the greatest increase in graft load being 19.0 ± 12.9 N (p = 0.004) in response to applied rotatory loads at 30° flexion.

Discussion

The present data suggest that, on average, the reconstruction restores the motions of the native knee closely enough that the ALL does not carry higher loads during most clinical exams of knee stability. However, in particularly lax individuals or in the presence of an imperfect ACL reconstruction, there might be an increased role of the ALL in stabilizing internal rotation and this may increase loads on the ACL graft during applied rotatory loads at 30° flexion.