Intra-corporeal Method for Observing Deformity of the Femoral Head under Mechanical Loading in the Rat

We observed the histological deformities in the rat hip joint caused by mechanical loading using an original intra-corporeal method. This was done to investigate the pathogenesis of disorders in the proximal femoral epiphysis such as slipped capital femoral epiphysis and Perthes' disease which usually deform the femoral head architecture.Under a compressive loading force of 3 Kilogram, the articular cartilage was depressed at the lateral part of both the femoral head and acetabulum in Wister rats from 9 weeks of age. Plump chondrocytes became spindle shape and the osseous nucleus sank into the growth plate. The growth plate decreased in thickness and the cellular column was distorted in that region, Deformity of the growth plate was more prominent in the lateral rather than the medial part. The above findings lessened with progression of age.Our new method is useful for understanding histological damage to the hip joint caused by mechanical loading.