Influence of lateral meniscal posterior root avulsions and the meniscofemoral ligaments on tibiofemoral contact mechanics

The purpose of this study was to investigate the effect of lateral meniscal posterior root avulsions combined with intact meniscofemoral ligaments (MFLs), deficient MFLs, anterior cruciate ligament (ACL) tears and reconstructions, and root repairs using an established tibiofemoral contact mechanics testing protocol. Ten fresh-frozen cadaveric knees were tested with six knee conditions (1: intact; 2: lateral meniscal posterior root avulsion; 3: root avulsion and deficient MFLs; 4: condition 3 with ACL tear; 5: condition 4 with ACL reconstruction; 6: ACL reconstruction with root repair) at five flexion angles (0A degrees, 30A degrees, 45A degrees, 60A degrees, and 90A degrees), under a 1000-N axial load. Contact area and pressure were measured with Tekscan sensors. Compared to the intact state, condition 2 did not significantly change lateral compartment contact area or pressure. Changes in contact mechanics were greater at increased flexion angles; for condition 3 at 0A degrees and 90A degrees, contact area decreased 37 and 52 % [95 % CI (21-53) and (39-66), respectively] and mean contact pressure increased 55 and 87 % [95 % CI (33-76) and (59-114), respectively]. Root repair with ACL reconstruction was not significantly different from the intact state. The MFLs protect the lateral compartment from changes in contact mechanics in the setting of a lateral meniscal posterior root avulsion, whereas a combination of lateral meniscal root avulsion and deficient MFLs leads to significant changes. Concurrent ACL reconstruction and lateral meniscal root repair restore mean contact pressure and area to the intact state and are recommended in this combined injury to prevent or slow the development of lateral compartment arthritis.