Of twenty-seven fracture-dislocations of the hip joint presented here, fifteen were fractures of the posterior rim, eight were comminuted fractures of the acetabulum, and four were fractures of the head of the femur. Treatment was either conservative or by open operation.

Results at the end of two years, in nineteen patients who could be followed, suggest the following conclusions:

1. Fractures of the posterosuperior rim of the acetabulum with displacement should be repaired as carefully as any other fracture of a weight-bearing joint.

2. Fractures of the posterior rim of the acetabulum, associated with dislocation of the hip, should be treated by cautious closed manipulation, followed by open reduction and internal fixation of the fracture through a posterior approach.

3. Dislocation of the hip joint, associated with comminuted fracture of the acetabulum, should not be subjected to closed manipulation. The only safe and efficient method of treatment is primary open reduction, as soon as the patient is in fit condition for a major procedure. When the goal of the operation is replacement of large fragments and exploration of the sciatic nerve, the posterior approach is required; when replacement of the head of the femur and erasion of the joint surface in preparation for fusion are indicated, the anterior approach is advisable.

4. Fractures of the head of the femur, except in cases in which it is necessary to reduce the size of the head or to excise the intra-articular fragments, are best treated by conservative methods.

5. Degenerative arthritis may be expected to occur in most cases in which the superior or weight-bearing surface of the head or the suiperior rim of the acetabulum is defective, and in many cases in which fragments of cartilage and bone were not cleaned out of the joint by open operation.

The diagnosis of avascular necrosis may be disclosed a short time after the injury in cases in which early arthrotomy is indicated. Two patients in this series differed from thirteen others with fresh fractures in that gross hemorrhages were fouind in the retinacula and the reflected capsule of the hip joint at open operation. One year later, only these two cases showed disintegration of the bone structure of the superior portion of the head of the femur. These observations suggest that avascular necrosis originates in a traction injumry and in subsequent thrombosis of the articular branches of the medial division of the femoral circumflex vessels.