Injury Reporting Frequency of the Anterolateral Ligament in Sport-related Anterior Cruciate Ligament Tears: A Retrospective Magnetic Resonance Imaging Review

Background: The anterolateral ligament (ALL) has gained interest due to ongoing debates on its clinical significance. This retrospective study aimed to determine the ALL-injury reporting rate on primary magnetic resonance imaging (MRI) assessment compared to a secondary review by a fellowship-trained musculoskeletal radiologist. We hypothesized that ALL injuries were underreported on routine MRI assessments. Materials and Methods: Inclusion criteria consisted of patients ≤25 years with sport-related anterior cruciate ligament (ACL) tears and concomitant injuries in the lateral compartment treated with primary ACL reconstructions from 2015 to 2019. ACL revisions and non-sport–related injuries were excluded. Secondary ALL visualization was defined as full, partial, or not visualized and characterized as Grade I (mild/intermediate sprain), II (severe sprain/partial tear), or III (complete tear/avulsion). Sample size was determined using chi-squared test of independence ( P < .05). Results: A total of 370 patients met the inclusion criteria and 200 were sequentially enrolled (average age: 21.1 ± 6.0 years, 34% women, 66% men). Injuries occurred during recreational (n = 86), high school (n = 83), college (n = 29), and professional sports (n = 2). The primary ALL-visualization rate was 0% (0/200) compared to 99.5% (199/200) during secondary review (133 fully, 66 partially). Of visualized ALLs, 67.5% (n = 135) demonstrated a concomitant injury that was missed on the initial MRI assessment: 41.5% Grade I, 44.4% Grade II, and 14.1% Grade III. Conclusion: Concomitant ALL injuries are frequently missed on routine MRI in young patients with primary sports-related ACL tears. Education and heightened awareness of the ALL may improve diagnostic accuracy on routine MRIs and provide guidance for surgical management.