An MRI-Based Staging System for Osteochondritis Dissecans Demonstrates Substantial Interrater Reliability and Tracks Progressive Ossification During Healing

PurposeTo evaluate the interrater reliability and clinical applicability of a novel MRI-based radiological staging system for osteochondritis dissecans (OCD) that incorporates a short echo time GRE sequence to assess progressive ossification and healing status. Methods and MaterialsThis retrospective HIPAA-compliant study was approved by the institutional IRB. MRI exams from April 2017 to December 2023 were reviewed for patients undergoing diagnostic OCD evaluation. Inclusion required the first MRI with a short echo time GRE (Gradient-Recalled Echo) and TSE (Turbo Spin Echo) sequences. Fifty-two MRIs (mean patient age: 13.4 {+/-} 3.8 years; 28 male, 24 female knees) were randomly selected to ensure balanced stage distribution. Five musculoskeletal radiologists and fellows independently applied the proposed staging system based on progressive ossification, bridging, and lesion stability. Interrater reliability was measured using Fleiss Kappa. Healing outcomes were stratified as: (i) early surgery, (ii) successful non-operative therapy, or (iii) delayed surgery after failed non-operative management. Mean healing times were compared across groups using ANOVA. ResultsSubstantial interrater reliability (Fleiss Kappa = 0.71, 95% CI: 0.65-0.77; p < 0.01) indicates strong agreement across five readers. Among 43 cases with clinical data, 19% (n=8) underwent immediate surgery, while 81% (n=35) received initial non-operative care; 29% (n=10) later required surgery. Healing times differed significantly (p = 0.002, ANOVA): 0.75 {+/-} 0.38 years for early surgery, 0.86 {+/-} 0.62 years for successful non-operative treatment, and 2.4 {+/-} 1.5 years for failed non-operative management with delayed surgery. Findings support the reproducibility of the staging system and its potential to identify lesions at risk of failed non-operative healing. ConclusionThis novel MRI-based radiological staging system demonstrates substantial interrater reliability and enables tracking of progressive ossification, improving assessment of OCD healing. Its integration of short echo time GRE sequences supports broader application in musculoskeletal imaging, including monitoring of fracture healing. Key ResultsO_ST_ABSHigh Interrater ReliabilityC_ST_ABSThe novel MRI-based Osteochondritis Dissecans (OCD) staging system demonstrated substantial interrater reliability (Fleiss Kappa = 0.71), supporting its reproducibility for clinical and research use. Healing Time DifferentiationHealing timelines differed significantly across treatment groups--patients with failed non-operative therapy required nearly three times longer to heal than those who underwent early surgery or successfully completed conservative treatment. MRI-based Ossification Tracking with broader ApplicabilityThe staging system effectively visualized progressive ossification using short echo time GRE sequences (TE < 2.6 ms), enabling assessment of healing stages not captured by conventional MRI sequences. Beyond OCD, this framework may be applicable to other conditions involving endochondral ossification, such as fracture healing. Summary StatementA novel MRI-based radiological staging system for osteochondritis dissecans demonstrates substantial interrater reliability and enables assessment of healing through improved visualization of progressive ossification using short echo time GRE.