We measured bone mineral density (BMD) in the proximal femur by dual-energy X-ray absorptiometry (DEXA) in 20 patients after cemented total hip arthroplasty over a period of one year. We found a statistically significant reduction in periprosthetic BMD after six months on the medial side and on the lateral side adjacent to the mid and distal thirds of the prosthesis. At one year after operation there was a mean 6.7% reduction in BMD in the region of the calcar and a mean 5.3% increase in BMD in the femoral shaft distal to the tip of the implant. These changes reflect a pattern of reduced stress in the proximal femur and increased stress around the tip of the prosthesis. They support current concepts of bone remodelling in the proximal femur in response to prosthetic implantation.

We reviewed 12 patients six years after they had undergone total hip replacement with a cementless prosthesis, the Ribbed Hip System (Waldemar Link GmbH & Co, Hamburg, Germany). Aseptic loosening of one or both components had necessitated revision surgery in seven patients, in five within two years of operation. In view of our experience we question the wisdom of allowing the uncontrolled use of new prosthesis without postoperative surveillance.

Dual-energy X-ray absorptiometry (DEXA) is increasingly used to measure changes in bone mineral density (BMD) around femoral prostheses after total hip arthroplasty. We have studied the factors which affect the accuracy of these measurements. The coefficient of variation was < 2% using a hydroxyapatite phantom, 2.7% in an anthropomorphic phantom specimen, and < 1% in repeated measurements on implanted cadaver femora. The precision did not vary with different implant materials or designs. In patients we found a mean precision error of 2.7% to 3.4%. The most significant factor affecting reproducibility was rotation of the femur. We conclude that DEXA is a precise method of measurement for small changes in BMD around femoral implants, but that correct and careful positioning of patients is essential to obtain reliable results.

The prevalence of HIV infection in East Africa has increased rapidly in recent years. We made a prospective study of the incidence of HIV-seropositivity in patients undergoing orthopaedic procedures in a large district hospital in Bulawayo, Zimbabwe. One of our aims was to determine whether a clinically-based screening programme, derived from the Centre for Disease Control classification of HIV infection, could identify high-risk individuals before surgery. During a 3-month period, 76 patients were tested, and 12 were HIV-positive (16%). Only two of these patients (17%) had clinical features associated with HIV infection; ten (83%) were entirely asymptomatic. Our results indicate that preoperative clinical screening is unlikely to be successful in identifying seropositive patients before routine surgery.

We studied the pedigrees of 17 index patients with osteosarcoma, recording malignant disease and cause of death for first- and second-degree relatives. There were seven cancers and five cancer deaths per 2151.5 person-years in first-degree relatives of osteosarcoma patients under the age of 50 years, a significantly greater incidence than in an age- and sex-matched population group (p < 0.001). This excess of malignancy was largely due to two families which fulfilled the criteria for the Li-Fraumeni cancer family syndrome. Both of these families were shown to have the genetic alterations in the p53 gene which have been implicated in this syndrome. Our study suggests that orthopaedic surgeons seeing new cases of osteosarcoma should arrange screening for familial malignancy.

1. Four cases of abnormal arrangement of the lower lumbar and sacral nerves within the spinal canal are reported.

2. In all four cases the presentation was like that associated with acute lumbar disc protrusion, though in only two cases was a protrusion found at operation.

3. The significance of the findings is discussed and the findings are compared with those in the eighteen other recorded cases.

Twenty-one post-irradiation fractures of the femoral neck are reported in seventeen patients who had been treated by radiotherapy for carcinoma of the uterus.

The clinical and radiological appearances are described and the diagnosis, prognosis and treatment of this type of fracture are discussed.

Histological material has been studied in three cases.

It is concluded:

1. That there is a characteristic clinical picture in which premonitory pain is of paramount significance.

2. That when the diagnosis is considered, the likelihood of irradiation damage should take precedence over the remote possibility of metastatic invasion.

3. That the disability varies, but in general the prognosis is favourable.

4. That there is no specific line of treatment applicable to these fractures.

5. That avascularity is not the underlying cause of this lesion.

1. In patients who develop de Quervain's disease variations from the standard pattern of tendons at the wrist are the rule rather than the exception.

2. Conservative treatment is of no value.

3. Adequate exposure, allowing full recognition of all anatomical structures in the region, is advisable, but branches of the radial nerve must be treated with respect.

4. The extensor pollicis brevis tendon is normally small and may pass through a separate osteofibrous canal.

5. Though incision only of the stenosing tendon sheaths may be sufficient, thorough excision is more certain and does no harm.