A case of injury of the axillary artery complicating a closed fracture of the neck of the humerus in a woman of eighty-six is reported. Spasm was not relieved despite repeated instillation of papaverine. Gangrene developed and amputation above the elbow was required.

1. A method of internal fixation of displaced subcapital fractures of the femoral neck is described, and a consecutive series of seventy-one patients whose fractures were treated by this method is reviewed.

2. It is claimed that this method gives better mechanical fixation than a trifin nail and that the operation is less formidable than the insertion of a pin and plate.

3. It is suggested that with improved fixation the avascular head can be supported while revascularisation occurs.

1. The structure and blood supply of the femoral head and neck, the mechanics of weight bearing, and the known effects of an inert foreign body are considered in relation to arthroplasty.

2. Some artificial hips are reviewed from the biomechanical standpoint.

3. From the information now available it is inferred that mechanical soundness and clinical success are not only co-related but interdependent; and that the mechanical problem of design offers most scope for further development at the present stage of our knowledge.

4. To this end six propositions are submitted.

5. A theoretical replacement arthroplasty, confined to the head and neck, in which breakdown of the component forces suggests that reciprocal use of both tensional and compressive loads might occur as in the natural femur, is described.