Histologic study of the femoral growth plate in beagle dogs

The femora of normal-growing beagle dogs were examined histologically at 6 and 12 mo of age to clarify the morphologic changes occurring in the femoral growth plate as background data for studies of chondrosseous toxicology. Enchondral ossification was active at 6 mo of age, and the growth plate disappeared at 12 mo. The growth plate showed degradation of the matrix and destructive lesions at 6 mo of age. Degradation of the matrix was observed between the chondrocytic columns accompanied by degeneration and disappearance of chondrocytes. Destructive changes were seen in the epiphyseal hyaline cartilage and proliferating and hypertrophic zones, resulting in disarrangement of the chondrocytic columns. Furthermore, abnormal chondrocytic proliferation of the epiphyseal hyaline cartilage zone and cleftlike fractures between the growth plate and cortex were frequently present. No abnormalities were detected in the articular cartilage at 6 and 12 mo of age.