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In talipes equino-varus the diminished bulk of the calf muscle suggests a neuromuscular defect. Accordingly, biopsies were taken from the postero-medial and peroneal muscle groups, and occasionally from abductor hallucis, in sixty patients mostly under the age of five years; 111 were studied histochemically and histologically, and a further fifty-three by electron-microscopy. Histochemical anomalies were revealed in ninety-two specimens; the muscle fibres in the other nineteen varied in size but were abnormal at the ultramicroscopic level, as were all specimens examined with the electron microscope. Evidence of neurogenic disease was seen in most instances and was more obvious in the older patients. The pattern of abnormality was similar in both muscle groups. It is thought that shortening of the postero-medial muscles may result from a small increase of fibrosis due to minor innervation changes occurring in intra-uterine life. There is evidence that immobilisation, stretching or relaxation of muscles does not account for the anomalies observed. This study of the extrinsic muscles in talipes equino-varus indicates a dominant neurogenic factor in its causation.

Synovial membrane and specimens of articular cartilage, obtained from the affected knee joints of 5 haemophilic patients at the time of surgical synovectomy, were studied. All the synovial specimens showed villous proliferation and multiplication of synovial cells. Haemosiderin granules were present within synovial cells and in macrophages. There was congestion and capillary proliferation. An inflammatory infiltrate of plasma cells and lymphocytes was seen in some instances. Articular cartilage changes were classified into the following 4 grades according to severity: 1--an increase in the number of surface chondrocytes with fibrous metaplasia, and the appearance of superficial fissures; 2--a fibrous vascularized overgrowth, resembling rheumatoid pannus; 3--deep fissuring and necrosis of cartilage; 4--erosion and disappearance of articular cartilage with exposure of subchondral bone. In the first 3 grades, deep nests of chondrocytes containing haemosiderin were present. These cell aggregates became larger and more degenerate as cartilage degradation progressed. Damaged articular cartilage was deficient in glycosaminoglycan (acid mucopolysaccharide). No excess enzyme activity could be demonstrated within the cartilage matrix. Immunofluorescent studies were not helpful. Electron microscopical examination revealed siderosomes within degenerate chondrocytes and synovial cells. Granules resembling haemosiderin were also present in the cartilage matrix. It is considered that iron products affect both chondrocytes and matrix adversely and play a part in articular cartilage destruction in haemophilia.

The Chiari pelvic osteotomy deserves better than the rather damning description of "salvage procedure." Although it cannot be regarded as a physiologic reconstructive procedure because hyaline articular cartilage is not brought over the femoral head, it nvertheless has unique advantages and specific indications. The procedure is entirely extra-articular, and the tissue (largely new bone) that forms between the displaced ilium above and the capsule of the joint below has the capability of adapting to irregularities in the femoral head. This provides the operation with flexibility of application and it may be used when acetabular rotation procedures are contraindicated. It is most effective in containing coxa magna and the moderately distorted, exposed femoral head. Because it success does not depend upon the shape of the acetabulum, it finds a further important role in containing the femoral head in conditions of acetabular dysplasia. The Chiari pelvic osteotomy must be performed accurately and with due care. When applied correctly, it has specific and important roles in the management of many difficult conditions of the hip joint.