We used dual-energy X-ray absorptiometry (DEXA) to measure the bone mineral content (BMC) of both tibiae in 13 patients who had been treated for a tibial fracture by rigid plate fixation. Within two weeks of plate removal the BMC was significantly greater in the bone that had been under the plate than at the same site in the control tibia. An unplated area of bone near the ankle showed a significant decrease in BMC at the time of plate removal with subsequent return to the level of the control tibia during the ensuing 18 months. We conclude that osteoinductive influences outweigh the potential causes of osteopenia, such as stress shielding and disuse, and that, contrary to expectation, demineralisation is not a factor in the diminished strength of the tibia after plating for fracture.

An experimental study performed in 16 mongrel dogs is presented, which shows that when venous stasis is combined with the local injection of non-esterified fatty acid an intense thrombosis results. This response is not produced by venous stasis alone, nor by the combination of venous stasis and triacylglycerol. Histologically it is quite different from the response produced by an inert intraluminal foreign body. It does resemble venous thrombosis described experimentally and in patients. The clinical relevance of these findings is that during accidental or operative trauma to a long bone, fat is commonly forced into the local venous circulation. If this event is combined with venous stasis or a tourniquet is used, then the circumstances of this experiment are reproduced. It is suggested that the venous thrombosis which commonly complicates long-bone injury or operation is in part caused by the thrombogenic nature of the introduced fat.

A prospective randomised trial of surgical treatment for the displaced subcapital femoral fracture in patients of 70 years or more is presented. Two hundred and eighteen patients were randomly allocated into one of three treatment groups: manipulative reduction and internal fixation using Garden screws; Thompson hemiarthroplasty through a posterior (Moore) approach; and Thompson hemiarthroplasty through an anterolateral (McKee) approach. There is no significant difference in the mortality of the internal fixation and posterior arthroplasty groups. Both groups showed a significantly higher mortality than patients operated on through the anterior approach. The technical results of operation were worse in the internally fixed group, with only 40 per cent being satisfactory. Mobilisation was best achieved after the posterior approach. It is concluded that Thompson hemiarthroplasty, using an anterolateral approach, is the safest operation in this group of patients.

A study of the natural history and aetiology of deep vein thrombosis in 499 patients after total hip replacement is presented. Deep vein thrombosis was diagnosed by scanning the leg for 125Iodine-labelled fibrinogen for a period of 14 to 18 days and by ascending phlebography. It has been shown that deep vein thrombosis occurs ater than in patients who have undergone abdominal operations, and the risk period is longer. The peak of onset of thrombosis is on the fourth day after the hip replacement. Attempts at prophylaxis using subcutaneous heparin or intermittent pneumatic compression of the calves delay the appearance of thrombosis. Analysis of possible aetiology factors shows that the age of the patient, the degenerative disease of the hip, the surgical approach, and under-transfusion of blood, all have a significant effect on the incidence of thrombosis.

A new radiological technique is presented in which serial axial radiographs of the patellofemoral joints are taken under conditions in which the muscles about the knee and hip are contracted in a manner similar to that during weight-bearing. A form of analysis has been developed whereby patellar rotation can be measured in two planes and femoral rotation about its long axis inferred. A population of asymptomatic adults and children was investigated in this way and their results (regarded as normal) compared with those in fifteen children with idiopathic chondromalacia patellae. In the normal child the femur rotates medially with the onset of muscle activity; by contrast the children with chondromalacia show a reversal of this mechanism.

The records of 107 patients with displaced subcaptial hip fractures treated by Thompson's femoral head replacements have been reviewed to determine the mortality and certain aspects of systemic morbidity. Comparison was made with a group, matched exactly for age and sex, in which intertrochanteric fractures were treated by nail-plate fixation. The patients treated by Thompson's arthroplasty were further subdivided into two groups: one in which methylacrylic cement was used, and one in which it was not used. We found no difference in the mortality of the patients undergoing replacement arthroplasty and nail-plate fixation. Similarly there was no difference in the incidence of cerebrovascular incidents and myocardial infarction after operation. There was a higher incidence of transient cardiac failure following Thompson's arthroplasty. Hypotension during the operation occurred irrespective of whether cement was used; nor was the use of cement associated with increased mortality. However, it seems that methylacrylic cement does contribute to the cardiac failure that may occur after Thompson's arthroplasty.