1. The case reported is of interest because, despite the relative frequency of traumatic dislocation of the hip with accompanying tear of the round ligament, no report was found in the literature of a similar case of aseptic necrosis and breaking down of a part of the head of the femur as a sequel. The chronic arthritis of the hip appeared to be secondary to the necrosis. The picture is somewhat similar to that sometimes seen in intracapsular fracture of the neck of the femur, with necrosis of the head, in which bony union occurs but the head subsequently breaks down as a result of weight-bearing before bony transformation has taken place. When it becomes evident from roentgenograms that aseptic necrosis in the femoral head from any cause has occurred, weight-bearing should be avoided during the period of repair. A study of the late results of hip dislocation might reveal similar cases.
2. Attempts were made to reproduce the picture in dogs and rabbits by cutting the ligamentum teres and, in some cases, also the vessels in the periosteum of the femoral neck. They were only partially successful. A part of the bone died in some experiments, as shown in Table III, and was transformed; but in no instance was collapse of the head and necrosis of its articular cartilage observed. The divided ligamentum teres showed a distinct tendency to unite in the experimental animals. It appears that the vascular supply of the head of the femur by way of vessels within the femoral neck of these animals was usually sufficient to preserve the vitality of the head.
3. There was no regularity in the process of transformation of the femoral heads following operative circulatory interference. Apparently, the variability of the blood supply to the head of the femur is such that, by interrupting identical portions of it in a series of experimental animals, identical and progressive stages of aseptic necrosis, followed by transformation of the femoral heads, could not be demonstrated. There is a certain individual reaction of each head in a series of similar operative procedures.
4. The ligamentum teres showed a distinct tendency to unite after operative division.
5. No head in the animals with open epiphyseal lines showed changes similar to Legg-Calve-Perthés' disease.