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 experimen tal 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 w ere studied to assess correlations. We assessed nonenhanced and gadolinium- enhanced T1-weighted, intermediate-weighted, T2-weighted, and spoiled gradi ent-recalled-echo T1-weighted images. RESULTS: In all MR studies, the injury was visible as a cleft of signal int ensity lower than the signal intensity of the physeal cartilage. Juxtaepiph yseal 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 p roximal tibial physis (P = .008). In 20 of 23 specimens, MR imaging and his tologic findings had excellent correlation for the detection of fracture le vel 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 jux taepiphyseal physis, a potential risk factor for growth arrest, is detectab le with MR imaging; MR imaging and histologic findings correlate well.