Failure of an acetabular cup is uncommon and has been attributed to wear or creep, trauma or bony irregularities in the acetabulum. We report ten cases in which fracture of the cup occurred at the site of drill holes used to anchor the marker wire. The role of such indentations as stress raisers has not been previously reported; we suggest that deep indentations or grooves should not be placed in the most highly stressed areas and that the cup thickness should allow for predicted wear rates.

Five children with atlanto-axial rotatory fixation (AARF) in association with fractures of the clavicle are described. It is postulated that the rotary fixation is a direct result of the trauma which produces the fracture. The importance of early diagnosis is stressed, since delayed diagnosis may lead to chronic deformity. Early diagnosis depends on awareness of the possibility of AARF, and either fluoroscoping the patient in order to take appropriate spot films or imaging the atlanto-axial joint by CT. A simple classification of AARF is proposed based on distinct radiological features which differentiate subluxation from dislocation.

We investigated the relationship between the pain experienced by 50 patients with osteoarthritis of the hip and the resting intra-articular pressure of the synovial fluid. We found a significant linear correlation between these factors, greater pain being experienced by patients with higher pressures. In 20 cases we showed that the pressure rises in extension and medial rotation and is least in flexion and mid-abduction. These results help to explain the benefits of rotation osteotomy of the hip and of psoas release. They also help explain the natural resting position of the hip in patients with an acute effusion and the fixed deformities associated with late osteoarthritis of the hip.

The use of a rotation osteotomy of the humerus in 10 patients with disabling loss of lateral rotation at the shoulder due to brachial plexus birth injuries is described. The operative technique and complications are discussed. Before operation only one patient was independent, but after operation nine of them were. Restoration of lateral rotation at the shoulder can improve the function, the appearance and the independence of these handicapped patients.