This paper describes a new technique for greater trochanteric hip arthroplasty in which the femur is divided at the subtrochanteric level and the upper fragment rotated through 180 degrees to place the greater trochanter deeply in the acetabulum; with the lower limb in the weight-bearing position the fragments are then fixed with a short intramedullary nail. This operation was carried out in a boy aged 4 years 6 months in whom the femoral head and neck had been destroyed by septic arthritis. Ten years later leg-lengthening was performed. When reviewed at the age of 20, he had a stable hip, a satisfactory range of painless movement, and shortening of only 2.5 cm; he could walk and run for long distances with only a slight abductor lunch.

The residual shortening of the affected limbs in 55 patients treated by subtrochanteric varus derotation osteotomy was compared with that in 71 patients treated with weight-relieving calipers. When last examined, 43 of the former group and 47 of the latter had reached complete or near-complete skeletal maturity. The average follow-up was 9.1 years in the osteotomised patients and 5.25 years in the conservatively treated group. The average residual shortening (0.9 cm) was identical in both groups. In most patients the initial shortening caused by the osteotomy gradually corrected as, over a period of several years, the postosteotomy angle gradually became less varus. Any residual shortening depended principally on the severity of inhibition of endochondral ossification at the proximal femoral growth plate. Less residual shortening was seen in children who were under seven years of age at the onset of symptoms (under eight at operation) in whom the open-wedge technique of osteotomy was employed and who had good anatomical results.

1. Synovitis was induced in the hip joints of fifty-six rabbits by the intra-articular injection of surgical talc. The opposite hip joint and eleven suitable"sham" operations served as controls.

2. The results in the hips injected with talc were as follows. Widening of the medial joint space and sometimes acetabular changes were seen; enlargement of the femoral head and neck in two planes was found, with, in most cases, flattening of the superior aspect of the head; there was thickening of the joint cartilage and sometimes deformity of the capital epiphysis; thickening of the cartilage was the main cause of the coxa magna, cervix magna and ischium magnum.

3. The embryology, micro-anatomy and development of the hip joint is reviewed and attention is drawn to the configuration of the layers of germinal cartilage cells. The effect of an induced synovitis in producing hyperplasia of the joint cartilage, incongruity of the articulating surfaces and subsequent subluxation is discussed.

1. A rationale of subtrochanteric osteotomy with derotation and varus angulation in the treatment of Perthes' disease is suggested.

2. Three months after operation the child returns to a normal unrestricted life.

3. The anatomical results in twelve such operations with an average follow-up of two years and five months are presented. In five children the results were "very good," in four "good," in one "fair" and in one "bad."

4. These results seem to compare favourably with those observed after conservative treatment of two, three or more years duration.

1 . An operation for strengthening the lateral abdominal muscles in children after poliomyelitis is described. It consists of transposition of the proximal part of the gluteus maximus, the tensor fasciae latae and the ilio-tibial band ("the pelvic deltoid" of Henry) to a chosen rib.

2. The results of this operation in eight consecutive cases of paralytic scoliosis, pelvic obliquity and thoraco-pelvic instability are assessed.

3. A "strong" motor allows the child to lift the pelvis against gravity, whereas with a "weak" motor the child is unable to do so efficiently. However, even a "weak" musculotendinous tendinous unit helps invariably in restoring the thoraco-pelvic stability, just as a weak "hamstring-into-patella" transplant stabilises the knee.

4. Those motors (gluteus maximus with or without tensor fasciae latae) that contract vigorously and move the free end of the ilio-tibial band for at least three centimetres on direct faradic stimulation with a bipolar electrode during the operation become ultimately strong and most efficient.

5. The unreliability of the clinical test of tensor fasciae latae in small children is discussed, and the advantage of using the gluteus maximus as the motor for the musculo-tendinous unit is emphasised.

6. Using the proximal half (or less) of the gluteus maximus for strengthening the lateral abdominal muscles does not seem to affect appreciably the strength of hip extension. This phenomenon may be explained with reasonable probability by the existence of a twofold insertion of that muscle.

1. A dynamic muscle-tendon transposition is described for supplementing the power of weak lateral abdominal muscles, and the details of the operative technique are given.

2. A clinical assessment of the results in a series of twenty-four patients is given.

3. The indications for the operation in poliomyelitis are suggested.