Cartilaginous path of physeal fracture-separations: Evaluation with MR imaging - An experimental study with histologic correlation in rabbits

PURPOSE: To define the transverse levels of intracartilaginous fractures by using magnetic resonance (MR) imaging and histologic analysis in experimental physeal fracture-separations. MATERIALS AND METHODS: Physeal fracture-separations were evaluated with MR imaging in 28 distal femurs and 28 proximal tibias of 22 immature rabbits. The intraphyseal transverse level of injury was graded as juxtaepiphyseal (germinal or proliferative zones) or juxtametaphyseal (hypertrophic zone or zone of provisional calcification). Histologic sections from 23 specimens were studied to assess correlations. We assessed nonenhanced and gadolinium-enhanced T1-weighted, intermediate-weighted, T2-weighted, and spoiled gradient-recalled-echo T1-weighted images. RESULTS: In all MR studies, the injury was visible as a cleft of signal intensity lower than the signal intensity of the physeal cartilage. Juxtaepiphyseal extension, seen in 18 (64%) of 28 fractures, was more frequent in the undulating central part of the distal femoral physis than in the flatter proximal tibial physis (P = .008). In 20 of 23 specimens, MR imaging and histologic findings had excellent correlation for the detection of fracture level and morphology. CONCLUSION: The course and level of injury within the cartilage in physeal fracture-separations can be defined with MR imaging. Extension into the juxtaepiphyseal physis, a potential risk factor for growth arrest, is detectable with MR imaging; MR imaging and histologic findings correlate well.