Association Between ACL Continuity on Magnetic Resonance Imaging at 5 Years After an Acute ACL Rupture and 11-Year Outcomes: A Secondary Analysis From the KANON Trial.

BACKGROUND Emerging evidence suggests that anterior cruciate ligament (ACL) ruptures can restore ACL fiber continuity. The relationship between ACL continuity on magnetic resonance imaging (MRI) (sign of ACL healing) and outcomes >5 years after an acute ACL rupture has not been investigated. PURPOSE This study aimed to (1) describe clinical outcomes and radiographic osteoarthritis (ROA) at 11 years based on ACL continuity status at 5 years and (2) investigate the relationship between 5-year ACL continuity status and 11-year Knee Injury and Osteoarthritis Outcome Score (KOOS4) scores. STUDY DESIGN Secondary analysis of KANON randomized controlled trial; Level of evidence, 3. METHODS Overall, 105 of 121 (87%) active adults with acute ACL ruptures randomized to undergo initial exercise therapy and optional delayed ACL reconstruction (ACLR) or early ACLR and postoperative exercise therapy completed 11-year follow-up. MRI scans at 5 years were evaluated using the Anterior Cruciate Ligament OsteoArthritis Score (0-3), with grades 0 to 2 considered to represent "ACL continuity." Patient-reported outcomes (KOOS4, 36-Item Short Form Health Survey, Tegner Activity Scale, self-reported new knee injuries), knee laxity, and radiographic findings (tibiofemoral and/or patellofemoral ROA) were assessed at 11 years. The relationship between 5-year ACL continuity and 11-year KOOS4 scores (0-100) was examined using linear regression, adjusted for age, sex, smoking, and baseline KOOS4 scores. RESULTS Of patients managed nonsurgically, 58% (n = 14) had ACL continuity and 42% (n = 10) had ACL discontinuity at 5 years. Analyses suggest that ACL continuity was associated with worse 11-year KOOS4 scores compared with delayed ACLR (adjusted mean difference, -20.2 [95% CI, -31.9 to -8.6]) and early ACLR (adjusted mean difference, -15.5 [95% CI, -26.4 to -4.7]) as well as similar or worse KOOS4 scores compared with ACL discontinuity (adjusted mean difference, -11.4 [95% CI, -26.5 to 3.6]). The proportion of patients with tibiofemoral ROA ranged from 14% (ACL continuity) to 23% (delayed ACLR), and the proportion of patients with patellofemoral ROA ranged from 11% (ACL discontinuity) to 41% (early ACLR). CONCLUSION ACL continuity on 5-year MRI may be associated with worse patient-reported outcomes at 11 years after an ACL injury compared with early or delayed ACLR. REGISTRATION 84752559 (ISRCTN).