MRI Does Not Reliably Detect Kaplan Fiber Injury In Skeletally Immature Patients with an Acute ACL Tear

Background: To our knowledge, there have been no previous efforts to evaluate the prevalence of Kaplan fiber (KF) injury in skeletally immature patients with an acute anterior cruciate ligament (ACL) tear on magnetic resonance imaging (MRI) nor has there been any comparison of the reliability of previously described KF diagnostic criteria in this cohort. Purpose: To define the prevalence of KF injury in the setting of acute ACL tears using MRI performed within 90 days of injury among skeletally immature patients, and to compare the reliability of MRI in detecting KF injuries using 2 previously described diagnostic criteria. Study Design: Cohort study; Level of evidence, 3. Methods: Skeletally immature patients with an acute ACL tear confirmed using MRI within 90 days of injury were assessed. Two fellowship-trained musculoskeletal radiologists independently interpreted each MRI scan twice. KF injury was first assessed using the Van Dyck scheme (grade 0, normal; grade 1, periligamentous; grade 2, partial tear; and grade 3, complete tear). MRI scans were then reviewed again using the KF injury criteria proposed by Batty. Discrepancies in KF injury schemes were adjudicated by a third musculoskeletal radiologist. Interrater agreement for both methods was determined using Cohen κ. Results: Included were 45 patients (33 male, 12 female) with a mean age of 13.2 ± 1.6 years. KF injuries were identified in 17 of 45 (37.7%) knees of using the traditional Van Dyck grading scheme (interrater agreement κ = 0.40). The Batty diagnostic criteria identified KF injury in 5 of 45 (11.1%) (interrater agreement κ = 0.45); 17 (37.8%) MRI scans required a third reviewer adjudication for the Van Dyck scheme, while 4 (8.9%) required a third reviewer using the Batty criteria. Conclusion: The Batty diagnostic criteria detected a lower KF injury prevalence than previously reported in the adult population, while the Van Dyck prevalence was similar to rates in adult populations. Both grading criteria had poor interrater reliability in diagnosing a KF injury.