Posteromedial Ligament Repair of the Knee With Suture Tape Augmentation: A Biomechanical Study

Abstract

Background: In cases of acute combined posteromedial and anterior cruciate ligament (ACL) injuries, primary repair of the superficial medial collateral ligament (sMCL) and posterior oblique ligament (POL) with suture tape augmentation may be a reasonable alternative to standard tendon reconstruction techniques. Purpose/Hypothesis: The purpose was to examine the rotational and valgus laxity with ACL strain following sMCL and POL repair with suture tape augmentation at various degrees of knee flexion. It was hypothesized that this technique would restore knee laxity and kinematics comparable with those of the intact state. Study Design: Controlled laboratory study. Methods: Ten cadaveric knee specimens (mean ± SD, 57.9 ± 5.9 years) were obtained. Specimens were tested with the tibia fixed and the femur mobile on an X-Y table. Each specimen was tested in 4 conditions according to the state of the sMCL and POL: native, deficient, repaired with suture tape augmentation, and reconstructed with tendon allografts. Valgus laxity was tested with 40-N force applied in the lateral direction of the femur, and rotational motion was tested with 5-N torque applied to the tibia. ACL strain during valgus stress was also measured. Each condition was tested in 0°, 15°, 30°, 45°, and 60° of knee flexion. Results: Dissection of the sMCL and POL led to significantly increased valgus laxity in all flexion angles, with a significant increase in ACL strain at 30° ( P < .001) and 45° ( P < .001). Ligament repair with suture tape augmentation demonstrated similar valgus and rotational laxity as compared with intact specimens, with the exception of increased internal rotation at 30° ( P = .005). Ligament reconstruction resulted in significantly increased valgus opening at 45° ( P = .048) and significantly increased internal rotation at 30° ( P < .001) as compared with the native state. Direct comparison between surgical techniques showed no significant differences. Conclusion: At time zero, ligament repair of the posteromedial knee with suture tape augmentation restored close-to-native valgus and rotatory laxity, as well as native ACL strain for cases of complete sMCL and POL avulsion. Clinical Relevance: Ligament repair of the sMCL and POL with suture tape augmentation may be a reasonable alternative to tendon reconstruction techniques in cases of acute combined posteromedial and ACL injuries with valgus and rotatory instability.