Anterior Knee Laxity Increases Gapping of Posterior Horn Medial Meniscal Tears

Abstract

Background Meniscal tears often occur in association with anterior cruciate ligament (ACL) lesions or in chronically lax knees. It is also known that meniscal repairs are less likely to heal in ACL-deficient knees. Purpose To test the effect of different knee joint motion and loading conditions on the gapping behavior of longitudinal posterior horn meniscal tears in stable and ACL-deficient knee joints. Study Design Controlled laboratory study. Methods Longitudinal tears of 3 cm were set in the posterior horn of the medial menisci in 10 human cadaveric joints. The medial plateau of the knees was replaced by a transparent replica, and an arthroscope was placed underneath to observe the gapping phenomenon of the meniscal tears. The maximum gap width occurring during flexion-extension under various motion and loading situations was registered in intact and ACL-deficient joints before and after meniscal repair with FasT-Fix suture anchors. Results Longitudinal meniscal tears gapped significantly wider after ACL transection under 30-N axial joint load ( P < .05). Increasing the axial load to 200 N or applying external moments to the knee did not lead to further alterations in the gap size. Gapping was significantly reduced after meniscal repair ( P < .01). However, after meniscal repair, gapping under 30-N and 200-N axial joint load was still increased significantly after ACL transection compared with the ACL-intact state ( P < .05). Conclusion Anterior knee laxity increases gapping across both unrepaired and repaired vertical peripheral medial meniscal posterior horn tears. Clinical Relevance Repairing such meniscal tears without reconstructing the ACL may affect meniscus healing rates or increase the risk of retears. Moderate rehabilitation regimens can be recommended, allowing at least for partial weightbearing and knee motion from extension to 120° of flexion in a stable knee. However, caution should be recommended if meniscal repair is performed in a knee joint with persistent anterior laxity due to ACL deficiency.