Objective: The purpose of this study was to evaluate the effect of graft interposition into a physeal defect on the remaining physis.
Materials and methods: Bilateral partial physeal defects were made in the medial half of the proximal tibiae of 8-week-old New Zealand white rabbits (n=25). Biologic material (autogenous chondrocytes derived from perichondrial cells incorporated into beads) was implanted in the left-sided physeal defect, and right-sided untreated tibial defects were used as controls. Magnetic resonance (MR) imaging was obtained at 2, 4, 8, 12, and 16 weeks after operation using a 1.5-tesla MR unit. T1WI, T2WI, and gradient-recalled echo (GRE) images were obtained in the coronal plane. The MR features of physeal defects and of remaining physes were compared between grafted tibiae and controls, as were histologic results and the heights of the remaining physes.
Results: Histologically, cartilage clusters were detected in the 17 cases of grafted tibiae (68%), whereas a bone bridge was observed in all controls. The cartilage clusters showed high signal intensity on both T2WI and GRE and low signal intensity on T1WI at 2 weeks postoperatively, and became low signal intensity on T2WI at 8 weeks. On GRE images, high signal intensities of the remaining physes disappeared earlier in the control tibiae than in the grafted tibiae. The remaining physes of control tibiae showed altered histologic configurations and a progressive decrease in physis height. Quantitative measurements of the height of the remaining growth plates showed a significant difference between grafted tibiae and controls (P <0.001).
Conclusion: Graft interposition into a partial physeal defect may prevent early closure of the remaining physis and bone bridge formation. MR imaging can depict alterations of remaining physes that lead to early closure of the physis.