Steep medial posterior tibial slope angle and ramp lesion are independent risk factors for an increase in quantitatively measured pivot shift in patients with ACL-deficient knees.

Background: Delayed anterior cruciate ligament (ACL) reconstruction often causes residual anterolateral rotatory instability (ALRI) and consequent knee osteoarthritis, warranting the recommendation of early ACL reconstruction within 6 months after injury. Nonetheless, some cases show notable instability, even shortly after injury. The purpose of this study was to identify risk factors for an increase in quantitatively measured pivot shift in patients with ACL-deficient knees within 6 months after injury. Methods: Patients with primary ACL reconstruction within 6 months after injury and quantitative triaxial accelerometer measurements of preoperative pivot shift were included. Descriptive statistics were calculated for 11 independent variables (age, gender, time from injury to surgery, KT-1000, knee extension angle, lateral and medial posterior tibial slope angle, medial and lateral meniscus tears, ramp lesion and Tegner active scale). A single regression analysis was performed on the 11 items and acceleration during the pivot shift, and a multiple regression analysis was performed for items with Results: Overall, 111 patients met the inclusion criteria. Single regression analysis showed that medial posterior tibial slope angle, medial meniscus tear and ramp lesion were significantly correlated with acceleration during the pivot shift ( Conclusion: A steep medial posterior tibial slope angle and ramp lesion were independent risk factors for increased quantitatively measured pivot shift in patients with ACL-deficient knees. Level of Evidence: Level IV, case series study.