1. Evidence is presented which suggests that after total joint replacement bone necrosis and consequent loosening of the prosthesis may be due to the development of sensitivity to the metals used.

2. Nine patients, from a total of fourteen with loose prostheses, were found to be metal sensitive by skin-patch testing. In twenty-four patients with intact prostheses no sensitivity was demonstrated.

3. In material from the joints of sensitive patients the metal content was raised.

4. Examination of this material showed necrosis of bone and soft tissue following obliterative changes in the vascular supply.

5. Similar reactions were found following the injection of cobalt into a sensitive patient.

6. The release of metal around a prosthesis is greatest where metal rubs against itself.

7. We conclude that prostheses in which metal articulates with polyethylene should be preferred; that any patient in whom loosening or fragmentation occurs should be patch tested; and that if sensitivity is found the implant should be removed.

1. A method of treatment of posterior malleolar fracture is described which restores the proximal surface of the ankle joint to its normal position.

2. Reduction is achieved with a special clamp and the position held with a strong plate. Early ankle movements may therefore be encouraged without fear of redisplacing the fracture.

3. Perfect reduction is necessary to avoid the later onset of arthritis, and this was achieved in five of six patients reported.

1. Nine cases of stress fracture of the pelvis after total hip replacement are reported, five after Ring replacement and four after a McKee. In none of the cases did the fractures unite.

2. In three cases infection was probably an important cause of the fracture. In six cases there was no infection. Only one presented a history of injury.

3. The combination of the various factors that might have caused the stress fractures is discussed.