We have studied the long-term results of core decompression as the sole treatment for Ficat stages I, II and III ischaemic necrosis of 128 femoral heads in 90 patients. The 5-, 10- and 15-year survival rates for the three stages were respectively: stage I 100%, 96% and 90%; stage II 85%, 74% and 66%; and stage III 58%, 35% and 23%. At a mean follow-up of 11 years (4.5 to 19), 55 hips had failed (43%). No further surgery had been needed for 88% of stage-I, 72% of stage-II and 26% of stage-III hips; but despite the generally satisfactory clinical results, 56% of the hips had progressed radiographically by at least one Ficat stage. Complications of the core procedure included four fractures, all from postoperative falls, and one head perforation due to technical error. We conclude that core decompression delays the need for total hip replacement in young patients with ischaemic necrosis.

Thirty shoulders, in 20 patients, which had undergone core decompression for symptomatic avascular necrosis of the humeral head were reviewed 2 to 14 years later (average 5.6). Twenty-two showed good or excellent clinical results; the other eight shoulders had required arthroplasty. All 14 shoulders with stage I or II radiological changes (Ficat and Arlet 1980) at operation had good or excellent results. We advocate early core decompression for symptomatic avascular necrosis of the humeral head.

The osseo-integration of an uncemented acetabular component depends on its initial stability. This is usually provided by under-reaming of the acetabulum. We have assessed the fixation of 52 mm porous-coated hemispherical prostheses inserted into cadaveric acetabula under-reamed by 1, 2, 3 and 4 mm. We tested the torsional stability of fixation, after preloading with 686 N in compression, by measuring the torque required to produce 1 degree and 2 degrees of rotation. Under-reaming by 2 mm and 3 mm gave significantly better fixation than 1 mm (p less than 0.01, p less than 0.02). Insertion after under-reaming of 4 mm caused some fractures. To obtain maximum interference fit and optimal implant stability, we recommend the use of an implant 2 mm or 3 mm larger than the last reamer.

Retrospective review of 730 consecutive primary uncemented and cemented total hip arthroplasties revealed 19 intra-operative hoop-stress fractures of the femoral neck. These were incomplete, linear, and minimally displaced. Management was by cerclage wiring (12), bone graft and cerclage (two), further impaction (two), and the use of cement (three), with no change from our standard postoperative management and rehabilitation. Eighteen patients had excellent or good results with an average Harris hip score of 93. Radiographically, all but one patient had Engh stability-fixation scores consistent with stable bone ingrowth. We conclude that hoop-stress fractures of the proximal femur, properly managed, do not detract from the results of total hip arthroplasty.

From 1974 to 1981, we performed 28 core decompressions of the distal femur for pathologically confirmed avascular necrosis. At a mean follow-up of 54 months (range 20 to 140 months) and using the Ficat stages, all seven cases in stage I and stage II had good results. Of 21 cases in stage III, 11 cases had good results, four had poor results, and six needed total knee replacement. There were no significant orthopaedic complications. The procedure is worthwhile and will be more accurate with new methods of imaging.

Of 24 intertrochanteric osteotomies for avascular necrosis of the femoral head, 22 were followed up for an average of 63 months. Sixteen of the 22 cases had good or excellent results, including 5 of the 6 cases with Stage II disease and 11 of the 16 with Stage III changes. Success seemed to be inversely related to the size of the lesion. There were six major orthopaedic complications, but despite these we feel that the operation has a definite role in the treatment of the young active patient.

Thirty-six patients with reflex sympathetic dystrophy primarily affecting the knee were reviewed. Injuries or operation about the patellofemoral joint triggered its onset in 64% of patients. Co-existent mechanical derangement of the knee was present in 64% of patients. Those patients who underwent sympathetic blockade or sympathectomy within one year of onset of symptoms had significantly better pain and function scores than those in whom intervention was later. Early diagnosis remains the key to successful management. Surgery for co-existent mechanical derangement in the affected knee should not be performed until the syndrome is controlled.

Cadaver knee joints were mounted so that life-like forces of weight-bearing were simulated. The patello-femoral contact areas were defined under load throughout the range of movement by the dye method. During movement from extension to 90 degrees of flexion a band of contact sweeps across the patella from inferior to superior pole, but the odd facet makes no contact. At about 135 degrees of flexion separate medial and lateral contact areas form, the medial one limited to the odd facet. From extension to 90 degrees of flexion the patella holds the quadriceps tendon away from the femur, but in further degrees of flexion an extensive "tendo-femoral" contact area forms. Between 90 degrees and 135 degrees of flexion the patella rotates and the ridge between the medial and odd facets engages the femoral condyle. The odd facet is shown to be a habitual non-contact area and the ridge to be subject to high load, observations which correlate with cartilage lesions described in Part 2 of the paper.

Two distinct lesions affect the articular cartilage of the patella. Surface degeneration occurs particularly on the odd facet; it is age dependent, often present in youth and it becomes more frequent with increasing age. It probably does not occasion patello-femoral pain in youth, but may predispose to degenerative arthritis in that joint in later years and is regarded as a consequence of habitual disuse. The term "basal degeneration" is used to describe a lesion in which there is a fasciculation of collagen in the middle and deep zones of cartilage without, at first, affecting the surface. It was found astride the ridge separating the medial from the odd facet in twenty-three adolescents who had complained of prolonged patello-femoral pain. They were treated by excision of the disc of affected cartilage, with relief of pain in most cases. The pathogenesis of basal degeneration is related to the functional anatomy of the patella.