1. The changes in the head and neck of the femur in children with Perthes disease were constant. within fairly narrow limits, and included aseptic necrosis or necrobiosis, evidence suggestive of crushing, concurrent degeneration and repair, partial ossification of displaced cartilaginous tissue, loss of polarity of chondrocytes, small cartilaginous cysts, and areas of fibrous-cyst formation with giant cells in the walls, similar to those found in osteitis fibrosa cystica.

2. The pathological changes are those of disturbed metabolism rather than of trauma or infection, and suggest that each case should be studied for bone age and disturbances due to hormone and vitamin deficiencies. As no single deficiency seems to be present in all cases, each case should be studied individually.

3. Removal of the contents of the head should in itself be beneficial, since it eliminates debris that may lead to the formation of cysts and giant-cell reactions.

4. The interpretation of Legg-Calvé-Perthes disease, based on a study of the material presented, is (a) that the disease is primarily a prepuberal degenerative condition with aseptic necrosis of the epiphysis and upper portion of the metaphysis of the femur, depending in part upon some deficiency; (b) that the head becomes weakened to the point where weight-bearing injuries lead to slight flattening; and (c) that the remainder of the changes result from frustrated attempts at healing, which are obstructed by the presence of degenerated and displaced bone constituents and further complicated by the continued injuries of weight-bearing.