Abstract
BACKGROUND: Studies have shown that Kaplan fibers (KFs) play a role in controlling anterolateral rotatory knee laxity in anterior cruciate ligament (ACL) injury. However, recent clinical studies have suggested that KF injuries are not associated with a higher-grade pivot shift in knees with acute ACL injuries. PURPOSE: To compare the effect of KF and anterolateral ligament injury on anterolateral rotatory laxity as measured by the pivot-shift test in both adult and adolescent patients with acute ACL injury. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: This study consisted of patients who experienced primary acute ACL tears between January 2019 and December 2021. The magnetic resonance imaging examinations and pivot-shift tests for these individuals were conducted within 14 days after injury. Variables associated with concomitant injury were included in a binary logistic regression model to evaluate risk factors of a high-grade pivot shift and a KF injury. RESULTS: The study included 540 patients with acute ACL tears (64 adolescent patients and 476 adults). The main risk factor for a high-grade pivot shift after acute ACL injury in adults was partial or total disruption of anterolateral ligament continuity (odds ratio [OR], 2.271; 95% CI, 1.499-3.442). In adolescent patients, the main risk factor was KF injury (OR, 19.98; 95% CI, 2.367-168.669), including edema and disruption of continuity. CONCLUSION: The main risk factor for a high-grade pivot shift after acute ACL injury differs between adolescent patients and adults: the KF injury sign in adolescent patients indicates a higher-grade pivot shift.