2015 ISAKOS Biennial Congress ePoster #1359

Analysis of Kinematics in a Large Sub-Population of Cadaver Knees Reveals High Variability in Anterior Cruciate Ligament Function

James Boorman-Padgett, BS, New York, NY UNITED STATES
Kyle Stone, MS, New York, NY UNITED STATES
Mohammad Kia UNITED STATES
Andrew D. Pearle, MD, New York, NY UNITED STATES
Daniel W. Green, MD, MS, FACS, New York, NY UNITED STATES
Carl W Imhauser, PhD, New York, NY UNITED STATES
Thomas L. Wickiewicz, MD, New York, NY UNITED STATES

Hospital for Special Surgery, New York, NY, USA

FDA Status Not Applicable

Summary: The role of the anterior cruciate ligament in articular stability varies widely in a sub-population of cadaver knees.

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Abstract:

Introduction

This study aims to explore the contributions of the anterior cruciate ligament (ACL) to kinematic variability in a large sub-population of cadaver knees. The question addressed is: Does the ACL contribute to knee stability equally within this sub-population?

Methods

Kinematic data were collected on 56 knees with an intact ACL. A subset of 41 knees were tested under both intact and ACL deficient conditions. The kinematics of the native knee was measured with a 6 degree-of-freedom robotic manipulator (1). The ACL was subsequently sectioned and the kinematics of the ACL deficient knee was determined using the same system in 41 of the 56 knees. The Lachman (134 N anterior load at 30° flexion) and pivot shift exams (a combined 8 Nm valgus moment and 4 Nm internal moment at 15° flexion) were simulated. Three measures of knee stability were analyzed: internal external (IE) rotation and anterior posterior (AP) displacement of the tibia during the simulated pivot shift, and AP displacement of the tibia during the simulated Lachman. Means, standard deviations, and ranges were reported and differences compared using paired t-tests (p<0.05).

Results

Internal rotation during the simulated pivot shift was 17.5° ± 6.6° (range: 8.1° to 30.2°) in the intact knee and 21.2° ± 6.4° (range: 11.5° to 33.3°) in the ACL deficient knee (p=0.009). Anterior translation during the simulated pivot shift was -0.8 mm ± 2.4 mm (range: -5.8 mm to 4.6 mm) in the intact knee and 6.5 mm ± 2.5 mm (range: 1.8 mm to 11.4 mm) in the ACL deficient knee (p<0.001). Anterior translation during the simulated Lachman was 7.2 mm ± 2.0 mm (range: 3.7 mm to 13.9 mm) in the intact knee and 18.5 mm ± 3.2 mm (range: 11.6 mm to 26.5 mm) in the ACL deficient knee (p<0.001). The change in internal rotation during the simulated pivot shift after cutting the ACL was 2.9° ± 1.8° (range: -0.7° to 7.4°). The change in anterior translation during the simulated pivot shift after cutting the ACL was 7.1 mm ± 3.9 (range: -1.2 mm to 15.7 mm). The change in anterior translation during the simulated Lachman after cutting the ACL was 11.4 mm ± 2.9 (range: 5.8 mm to 17.4 mm).

Discussion And Conclusion

The role of the ACL in resisting internal rotation and anterior translation of the tibia varied widely within this sub-population. This may explain why some patients can retain function after tearing their ACL while others cannot.
Surgical approaches for ACL reconstruction are developed to produce favorable results for the “average” patient, but do not consider wide population variability in knee function. This may explain why current outcomes following treatment of ACL injury remain suboptimal including inability to return to previous level of play and 5% revision rates (2, 3). Future treatment of patients should consider this broad spectrum of kinematic behavior.
References:
1.McCarthy, et al. Am J Sports Med. 2013.
2.Ardern, et al. Am J Sports Med, 2011.
3.Paxton, et al. J Bone Joint Surg Am, 2010.