Development of the distal femoral epiphysis: a microscopic morphological investigation of the zone of Ranvier.

The distal femoral epiphysis, physis, and contiguous metaphysis were examined radiographically, morphologically, and histologically in 97 human specimens ranging in age from 9 prenatal weeks to 16 postnatal years. The earliest development of the femoral anlage was characterized by patterns of appositional and interstitial chondrogenesis throughout its entire structure. Once central endochondral ossification began, chondrogenic interstitial and appositional growth became regionally restricted to the femoral epiphyses. Interstitial chondrogenesis became limited to the germinal region of the developing physis, and appositional chondrogenesis was restricted to the region of loosely packed cells of the perichondrial ossification zone of Ranvier. Appositional chondrogenesis within the perichondrium appears to make its greatest contribution to transverse expansion of the distal femoral epiphysis during the first 5 months of gestation. After the sixth month of gestation, the perichondrial appositional growth contribution appears to decline steadily.