To investigate the effect of instability on the remodelling of a minor articular surface offset, we created a 0.5 mm coronal step-off of the medial femoral condyle in 12 New Zealand white rabbits and transected the anterior cruciate ligament (ACL). A control group of 12 rabbits had only ACL resection and the opposite knee was used as the non-operated control. The osteoarthritic changes at 6, 12 and 24 weeks after surgery were evaluated histologically. In addition, changes in the immunological detection of 3-B-3(-) and 7-D-4 chondroitin-6-sulphate epitopes were determined because of the previous association of such changes with repair of cartilage and early osteoarthritis.

In the instability/step-off group there was rapidly progressing focal degeneration of cartilage on the high side of the defect, not seen in previous step-off studies in stable knees. The rest of the femoral condyles and the tibial plateaux of the instability/step-off group had moderate osteoarthritis similar to that of the instability group. 3-B-3(-) was detectable in the early and the intermediate stages of osteoarthritis but no staining was seen in the severely damaged cartilage zones. Immunoreactivity with 7-D-4 increased as degeneration progressed.

Our findings have shown that even a minor surface offset may induce rapid degeneration of cartilage when the stability of the knee is compromised.

We compared the radiographic results of secondary total hip replacements, 99 following failed uncemented hemiarthroplasties and 21 following failed mould arthroplasties, with those of 825 primary cemented total hip replacements. The probability of occurrence of a number of radiological changes over time was calculated using survival analysis. The mean follow-up was 7.6 years (range one month to 20 years). The performance of the secondary total hip replacements varied with the preceding implant and was different for acetabular and femoral components. The incidence of radiological loosening was higher for femoral components implanted after failed hemiarthroplasties and for acetabular components after failed mould arthroplasties. However, the incidence of continuous radiolucent lines was lower for the acetabular components of converted hemiarthroplasties than for the primary replacements.

We reviewed the radiographs of 864 Charnley and STH (Zimmer) cemented total hip arthroplasties with a mean follow-up of seven years (maximum 16 years). Survivorship analysis was used to assess the correlation between radiographic performance and the bony containment or the coronal orientation of the acetabular cup. The cup orientation and containment were interrelated; all vertically oriented cups were completely contained, whereas 25% of more horizontal cups were only partially contained. Completely contained cups had significantly lower incidences of complete cement-bone radiolucency (p = 0.02) and of wear (p = 0.09). Vertically oriented cups had a lower incidence of continuous radiolucency than neutrally oriented cups, but this was not statistically significant (p = 0.25). Our results confirm the importance of complete bony containment, and also indicate that it is better to accept vertical orientation and obtain full bony coverage than to have a more horizontal orientation with partial containment.

From 1982 to 1987 we treated 85 extra-articular comminuted distal third humeral fractures in adults with prefabricated plastic braces. Of these, 15% were open fractures and 18% had initial peripheral nerve injury. On average, the sleeve was applied 12 days after injury and used for 10 weeks. There was 96% union, with no infections. All nerve injuries resolved or were improving at the latest examination. At union there was varus deformity averaging 9 degrees in 81% of patients, but loss of range of movement was minimal and functional results were good.

We have reviewed our recent results with functional bracing of tibial shaft fractures in adults in order to define its role in management. We also analysed several parameters of these fractures to discover those which influence healing. A total of 780 tibial fractures treated in prefabricated functional braces were followed to union; shortening of less than 10 mm and angulation of less than 5 degrees in any plane were our parameters for successful treatment. The average time before applying a brace was 3.8 weeks for closed fractures and 5.2 weeks for open ones. Closed fractures healed in an average of 17.4 weeks and open fractures in an average of 21.7 weeks, 90% of them with 10 mm of shortening or less. Varus angulation and posterior angulation were the most common deformities encountered at union. There were 20 nonunions (2.5%) and 46 braces were discontinued during treatment. We found no association between fracture healing and the patient's age, the mechanism of injury or the fracture location. The degree of soft tissue injury appeared to have most influence on the speed of fracture healing. Fracture comminution and initial displacement, the condition of the fibula and the time from injury to bracing also appeared to affect the speed of union.