There are differences of opinion about the pathogenesis of Perthes' disease. All are agreed that it is due to ischaemia, but the cause of this and the size and number of infarctions are in dispute. Through the generosity of the contributors six whole femoral heads and core biopsies of five other cases have been studied radiographically and histologically. The findings ranged from an ischaemic arrest of ossification in the capital articular cartilage without infarction to multiple complete infarctions of the epiphysial bone. The ensuing reparative process contributes to the pathology, which is of a range to warrant grading or grouping.

Eighty-four children suffering from Perthes' disease are reviewed. The policy of management for these patients was one by which 55 per cent of the cases had no active treatment and the remainder were treated by operation. Results of the series show an improvement over a previously reported series of untreated controls, particularly where clinical management had been possible throughout the disease process. The importance of early definitive treatment for Group 4 cases is stressed. It is concluded that in the early stages where "head-at-risk" signs are not present, treatment may be conservative. Should these signs develop later the long-term result is not prejudiced if operative treatment is undertaken promptly.

Perthes' disease is thought to be rare in black children but no figures of incidence have previously been available. A search was therefore made for cases of the disease occurring in the Eastern Cape during the five-year period 1975 to 1979. Of 55 cases found, 38 were in white children, 11 in children of mixed ancestry ("coloured" children) and six in black children. The annual incidence in white children aged 14 years and under was 10.8 per 100 000, in coloured children 1.7 per 100 000, and in black children 0.45 per 100 000. In all races the incidence in the metropolitan area of Port Elizabeth was roughly twice that in the rural part of the region. The reason for the low incidence in coloured and black children is not known but various factors are suggested.

Almost one child in twenty with trisomy 21 will develop spontaneous dislocation of the hip between learning to walk and the age of 10 years. After the age of two years spontaneous habitual dislocation may occur. If left untreated, acute dislocation, subluxation and fixed dislocation follow in sequence. The natural history of the condition is described and the clinical and radiological features of 45 dislocations in 28 patients are presented. Nineteen had received no treatment. The most effective treatment was found to be pelvic or femoral osteotomy, combined with capsular plication, carried out in the phase of habitual dislocation. Once subluxation or fixed dislocation was present, the results of operation were poor and it is not recommended. All patients, even if left untreated, remain mobile. Pain is not a prominent feature.

The use of a total femoral prosthesis can offer a realistic alternative to amputation or disarticulation. The limited indications for such a prosthesis in the surgical management of primary bone tumours and pathological fractures still exist. In this specialised clinic there is an increased need to replace the entire femur where repeated procedures have failed, from loss of bone stock with infection or because of non-union in the presence of a prosthesis. Over the past eight years, four basic models have been developed. The most recent designs allow for the preservation of non-involved bone or for stable support where there is complete acetabular destruction.

A clinical, radiological and histopathological study of femoral heads from 125 patients with fracture of the neck of the femur and from 30 cadavers was carried out to identify various risk factors. The findings showed that the Singh index was unreliable as a radiological indicator of the bone content of the femoral heads; that the bone content of the femoral head in patients sustaining a fracture of the femoral neck did not differ from that of the controls; that osteomalacia was not found in any of the heads examined; and that the distribution of trabecular microfractures did not support the hypothesis that fracture of the neck was the result of progressive fatigue. It was concluded that the single most important factor leading to fracture in this Australian population was injury caused by falls and that such injury was frequently associated with other disease processes.

The suggestion that the knee behaves like a closed kinematic chain has been tested experimentally. The tibial joint surfaces were replaced by a deformable material and new surfaces were moulded by flexion and extension of the knee. The results support the closed kinematic chain theory; the newly moulded joint surfaces strikingly resemble the original joint surfaces. Inferences are drawn to explain why a fracture of the tibial condyle will remould with early mobilisation of the knee; why a jerk is elicited in tests for anterolateral instability; and why a flexion-compression force alone is unlikely to damage the menisci.

Five vertebrae with unilateral spondylolysis are presented. The associated asymmetry of the posterior elements supports the concept of a localised form of growth deficiency. The defect is difficult to demonstrate radiologically, and is perhaps present more frequently than is recognised. It should be suspected clinically from asymmetry of the neural arch and from unilateral wedging of the vertebral body, and may be demonstrated by further radiographic examination. The clinical significance is uncertain, but one patient is presented in whom unilateral spondylolysis was associated with intermittent sciatic pain.

Injuries to the tarsometatarsal (Lisfranc) joint are not common, and the results of treatment are often unsatisfactory. Since no individual is likely to see many such injuries, we decided to make a retrospective study of patients from five different centres. In this way 119 patients with injuries of the Lisfranc joint have been collected. This paper classifies these injuries and describes their incidence, mechanism of production, methods of treatment, results and complications. Sixty-nine of the patients attended for review: 35 of these had been treated by closed methods, 27 had had an open reduction and seven patients had had no treatment. On the basis of our study we suggest that these injuries should be classified according to the type of injury rather than the nature of the deforming force and that their treatment be based upon this classification. It seems that, whatever the severity of the initial injury, prognosis depends on accurate reduction and its maintenance.

Between 1971 and 1976 eight patients underwent excision of the carpal lunate for pain from Kienbock's disease. The bone was replaced by a silicone rubber implant. An average of 84 months had elapsed when they were reviewed in December 1980. All eight were very satisfied with their operations. Objectively, the clinical results were good, but radiographs showed the presence of degenerative change in the region of the wrist and alteration of the position of the prosthesis on ulnar deviation of the hand. No implant has had to be removed.

Malunion of fractures of the forearm in children can lead to permanent disability. The capacity of the radius and ulna to remodel spontaneously after malunion has been assessed in this study. Forty-nine children who had malunited fractures of the forearm were examined when the remodelling process was complete. It was noted that fractures of the distal third of the radius and ulna led to fewer problems than those of the diaphysis. It was concluded that malunion of the distal third of the radius and the ulna will remodel satisfactorily providing the child is less than 14 years of age. Gross malunion of the midshaft of the radius and ulna will spontaneously correct in an infant but little useful correction of deformity can be anticipated in diaphysial fractures when the child is aged eight years or more.

This review of 27 cases serves to emphasis that periosteal chondrosarcoma and periosteal osteosarcoma are two distinct entities. Clinically, periosteal chondrosarcoma is less painful than periosteal osteosarcoma and runs a slower course. Radiographically, periosteal chondrosarcoma tends to affect the metaphysis and contains granular or "popcorn" opacities; while periosteal osteosarcoma more often affects the mid-diaphysis and shows lytic lesions with some spicules of reactive bone perpendicular to the underlying cortex. Histologically, periosteal chondrosarcoma shows lobular well-differentiated cartilage with Grade I or II (rarely Grade III) malignancy; periosteal osteosarcoma has a chondroid matrix with some osteoid component and Grade II or III malignancy. The prognosis in periosteal chondrosarcoma is good; conservative surgery is usually effective and metastases are very uncommon. In periosteal osteosarcoma the prognosis is less satisfactory but is better than that of other osteosarcomata; wide surgical excision is, however, needed and the incidence of metastases is about 15 per cent.

Thirteen patients with dyschondrosteosis from eight families are reviewed and their clinical and radiographic variation noted. Inheritance is likely to be autosomal dominant but with only 50 per cent penetrance. Stature was moderately reduced, due to shortening of the bones of the leg. Radio-ulnar shortening could either involve both bones equally or the radius predominantly, in which case a typical Madelung deformity was seen. Tibio-fibular disproportion was present in half the patients, two of them having severe deformity associated with tibia varum and a long fibula. The treatment of one of these patients is described. It is recommended that patients with dyschondrosteosis should be kept under surveillance during the growing period. Problems in the limbs, especially the legs, may require operations to equalise the length of the two bones.