Ninety-seven revisions of total hip replacements are reviewed with a median time of observation of 47 months. Satisfactory pain relief was obtained in 86%. There were six complete failures which were reduced to three by further surgery. One hip became infected and was excised. In 12 cases the revisions were complicated by peroperative fractures and in five by dislocations. Radiographic analysis disclosed a high percentage of periarticular ossification and 25 cases of radiographic loosening of the femoral implant.

The St Georg modular knee replacement has been studied in 59 cases with an observation period ranging from 28 to 73 months. In 47% of the knees both compartments were replaced; five of the six poor results were in this group. These were revised to a hinge arthroplasty or, in one case, to an arthrodesis. Other complications were few and insignificant. There were no infections. We concluded that unicompartmental knee arthroplasty can be recommended when joint involvement is localised to one compartment only. With more generalised joint disease we prefer a semiconstrained total condylar prosthesis.

The reliability of the Catterall grouping of Perthes' disease was examined by determining the agreement between pairs of observers using weighted kappa statistics. Anteroposterior and lateral radiographs of 100 hip joints were grouped independently by four experienced observers. There was a low, and in our opinion, unacceptable degree of inter-observer agreement even when Groups 2 and 3 were combined.