Lateral meniscus repair contributes to controlling pivot shift in patients undergoing anterior cruciate ligament reconstruction with steeper lateral posterior tibial slope

Purpose: The lateral meniscus (LM) controls anterolateral rotatory instability (ALRI) and is considered a secondary restraint. However, how the anterior cruciate ligament (ACL) and LM contribute to ALRI control remains unclear. This study investigated the degree to which ACL and LM contribute to ALRI control and examined factors contributing to ALRI during anterior cruciate ligament reconstruction (ACLR). Methods: Twenty-six patients in ACL and LM-injured knees were enroled. Tibial acceleration in pivot shift was measured using a triaxial accelerometer by adjusting ACL graft tension before and after LM repair. ACL graft tension required for below-healthy-side pivot shift acceleration (minimum required tension [MRT]) was measured before and after LM repair. Patient factors for a larger contribution of LM to ALRI were determined by univariate linear regression analysis between changes in pivot shift acceleration before and after LM repair, and explanatory variables included patient and morphological factors. Furthermore, multiple regression analysis was conducted to identify independent factors significantly associated with the change. Results: = 0.001). In the multiple regression analysis as well, lateral PTS was the only factor identified as a significant predictor. Conclusions: LM repair decreased pivot shift acceleration and MRT, indicating the importance of LM repair in force-sharing with the ACL. LM contributes significantly to ALRI in patients with a larger lateral PTS. During ACLR, the LM should be repaired as much as possible. Level of Evidence: Level III, diagnostic study.