Segmental vascular changes in the femoral head in children and adults.

The segmental nature of the avascular involvement of the femoral head in both children and adults is similar. Avascular necrosis may be wrongly interpreted from roentgenograms in infancy, irregular ossification may be due to altered stress on the femoral head. The segment involved in Legg-Perthes' disease is superior and lateral to the fovea in an area supplied by a branch of the lateral epiphyseal artery. Secondary changes occur due to the separation of the dead segment from the living bone. Theron demonstrated the vascular interruption with micro-injection techniques in both child and adult. Finite analysis of the femoral head revealed the distortion of the computer model at the site of the branches of the lateral epiphyseal artery. Trauma with vascular interruption within the femoral head appears to explain the avascular segment.