1. A three-year survey of avascular necrosis of bone has been carried out in a community of some 400 professional divers for shell-fish who had used no modern technique of decompression.

2. Of 301 divers radiographed, 152 (50·5 per cent) had bone lesions.

3. The incidence of bone necrosis increased in proportion to the length of diving experience, being highest in men with over ten years, experience.

4. The incidence was also higher in men who usually dived deeper than thirty metres.

5. There was a high incidence in men with a history of the bends but no significant relationship between the sites of the bends and those of the lesions.

6. Bone lesions were more frequently multiple than solitary.

7. The upper end of the humerus was significantly more affected than the upper end of the femur or tibia, but not significantly more than the lower end of the femur.

8. At the upper ends of the humerus and femur the lesions were more frequently unilateral than bilateral.

1. A review of 204 cases of prolapsed intervertebral disc treated by the author by operation ten to twenty-five years before is presented. Injury was an etiological factor in only 14 per cent.

2. The decision to operate should be made after a clearly defined and controlled, but limited, period of closed treatment. The patients should not have to wait for operation. Treatment by closed methods should not be continued in the absence of detectable signs of improvement. Continuation under such circumstances delays recovery from paralysis, prolongs convalescence and delays return to work. Persistence of paraesthesia and numbness are other probable consequences of such delay.

3. A central disc prolapse is an indication for urgent operation if persistent sphincter disturbance or incomplete bladder evacuation is to be avoided.

4. A recurrence rate of sciatica less frequent than that associated with treatment by closed methods is noted in this and other reported series. True recurrence, as opposed to a prolapse at another level, is rare and is most probably due to continuation of the biochemical process of degeneration leading to further sequestration of disc tissue. On the other hand, the altered spinal mechanics, particularly local rigidity resulting from enucleation of a deranged intervertebral disc, may predispose to prolapse at a higher level or may themselves be the cause of symptoms of "recurrence".

5. Operation gives early and lasting relief of sciatic pain, reduces the need for the subsequent use of a corset and assists the patient to an early return to work.

6. Operation does not affect the decision to change work. This is decided by the length of history before operation and the amount of disc degeneration; and the need to change work is the same whether the patient is treated by closed means or by operation.

7. Apart from simple back raising exercises to strengthen the spinal extensor muscles, no physiotherapy need be given because it is not likely to improve the prognosis.

8. Backache is the most frequent disability after operation (17 per cent) and is related to the degree of degenerative change present before and after operation. Injury precipitated the onset of backache in three cases. Operation does not by itself produce backache. The amount of bone removed has no demonstrable effect on the late results of operation, nor on the subsequent development of degenerative changes.

9. Enucleation of the nucleus is not followed by fibrous ankylosis across the intervertebral space.

1. The antero-posterior or sagittal diameter of the cervical spine has been measured radiographically in fifty-one Japanese men who fell into three groups-twenty with normal cervical spines, eleven with spondylosis but no neurological symptoms, and twenty with spondylosis and myelopathy.

2. The average normal diameter was found smaller by 2·25 millimetres in Japanese men than in European adults examined by other authors.

3. The average initial diameter in cases of spondylosis without neurological symptoms was found to be greater than normal, which suggests that the increased space round the cord helps to avoid compression.

4. The average initial diameter in cases of spondylosis with myelopathy was found to be less than normal, which suggests that compression may be determined by moderate osteophyte formation or disc protrusion.

5. The risk of myelopathy would appear to be high when the average diameter is 12 millimetres or less.

6. The difficulty with such radiological measurements is that standard lateral films cannot always record the degree of encroachment by disc protrusion or by hypertrophy of the soft tissues.

1. Further consideration has been given to the lateral rotation which occurs at the ankle joint in uncorrected club feet.

2. Medial rotation osteotomy of the tibia may be used to restore more normal alignment to the hind foot at the expense of an increase in varus of the forefoot, which must be corrected at a second operation.

3. The early results in seven feet treated in this manner are reported.

4. We hope that this paper will be regarded more as a contribution to the understanding of the anatomy of uncorrected club foot than as advocacy of a new method of surgical treatment.

1. A thousand arthritic hips have been replaced by an uncemented metal-on-metal prosthesis, and 942 followed by annual review. The mortality of the operation has been 1·1 per cent, the rate of deep-seated infection 0·7 per cent and the incidence of dislocation 0·3 per cent.

2. Of 169 hips replaced by an earlier type of the prosthesis and followed for five to eight years, 45 per cent have remained excellent and 29 per cent good, but 14 per cent have required revision, mainly for loosening of the femoral component.

3. The current types of prosthesis, now used for five years, have given excellent results in 69 per cent and good results in 21 per cent of 535 patients followed for one to five years. Revision for loosening has been necessary in 2 per cent.

4. The improvement in results has been obtained by the introduction of a tapered screw thread on the pelvic component, and by a range of femoral components that ensures a good cortical fit.

The effects of the liquid component of commercial acrylic cement and of pure methylmethacrylate monomer on mean arterial blood pressure, central venous pressure, heart rate and cardiac output have been compared in a series of six anaesthetised dogs. No significant differences were found between the two substances.

1. Experimental work with piglets supports the theory that diminished blood supply to the femoral head not only causes necrosis of the epiphysis but also a decrease in cartilage cell production in the germinal layer of the epiphysial plate, thus causing decreased longitudinal bone growth. Appositional growth continues in the metaphysis because its blood supply remains intact or, at least, is less impaired. The resulting disturbance of the normal remodelling must lead to a short wide neck such as occurs in Legg-Perthes' disease.

2. Measurements were made of the length and width of the femoral neck on radiographs of forty patients with Legg-Perthes' disease. The results showed that the degree of shortening and widening is related to the extent of structural change in the head.

3. Repeated measurements in the early stages of the active disease may permit an early prognosis which may be of great assistance in selecting the treatment suitable to each patient. The financial assistance of the Ontario Society for Crippled Children is gratefully acknowledged.

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. Observations on ninety-four persons with congenital coxa vara living in a Turkish village named Gonyeli in Cyprus are presented.

2. Various clinical and laboratory studies showed, in addition to the congenital coxa vara of varying severity, marked short stature and bowing of the lower extremities in almost all affected individuals and relative iliac hypoplasia and protrusio acetabuli in some.

3. Pedigree analysis indicates that this hitherto undescribed condition is inherited as an autosomal dominant trait.

1. Early recognition of femoro-pelvic instability in proximal femoral dysplasia is essential to rational management.

2. Certain radiological signs helpful in identifying such patients within the first year are described.

3. Early operation is recommended to prevent displacement of a pseudarthrosis and to encourage healing. Alternative methods are described for established defects.

4. Radiological signs are described which indicate that healing without loss of femoro-pelvic stability will occur. Such patients may be managed expectantly.

1. The results of treatment of fractures of the shaft of the femur in fifty patients aged sixty-five years and over seen over a twelve-year period are presented.

2. Half of the patients were treated by internal fixation and half by conservative methods. The mortality in the former group was three times that of the latter.

3. The length of hospital stay was only slightiy less after internal fixation because many patients in both groups had to remain in hospital because of social problems.

4. The indications for internal fixation of fractures of the shaft of the femur in elderly patients are discussed.

1. In a prospective study of sixty patients with cerebral palsy and contracture of the hamstrings, 112 operations were performed by three different techniques after any necessary correction of flexion contracture of the hip or equinus of the ankle.

2. Transposition by the method of Eggers has been abandoned because simple lengthening has been found to have several advantages.

3. Proximal lengthening, at or near the ischial tuberosity, is employed when fixed flexion of the knee does not exceed 5 degrees, and is now the standard method. A transverse incision in the natal fold avoids cheloid formation.

4. Distal lengthening behind the knee is reserved for cases in which the fixed flexion exceeds 5 degrees.

5. After lengthening and weakening of the hamstrings, these spastic patients could stand more easily and walk with straighter knees, the length ofstride became greater, stairs could be climbed more easily, the feet could be lifted more from the ground, and the wear on the front of the sole became less. In addition the sitting position often improved because flexion of the hips became normal.

1. A sagittal technique for below-knee amputation for ischaemic gangrene based on mediolateral musculo-cutaneous flaps is described, similar to the one independently presented by Tracy (1966).

2. The results with this method are illustrated by the evolution of the below-knee healing rate over six years in 172 patients with ischaemic gangrene.

3. A comparison between sagittal and conventional flap techniques shows a reamputation rate of six out of fifty-eight in the former and sixteen out of forty-one in the latter.

4. The overall relative knee joint preservation during 1971 was 82 per cent, and the frequency of attempted below-knee amputation was 93 per cent.

5. It is concluded that the sagittal technique has several advantages in comparison to the posterior flap technique, and that the potential for healing is on the same high level.

6. A fully controlled comparison between different techniques is proposed.

1. The details of construction of the Stanmore cosmetic caliper using modern plastic materials have been described.

2. The considerable advantages of this light-weight caliper over the cumbersome traditional appliance are discussed.

1. Clinical, radiological and pathological findings in seven cases of rheumatoid arthritis with giant bone cysts are presented.

2. In three cases the large cysts represented massive involvement of subchondral bone by rheumatoid granulation tissue; in two cases the cysts were due to rheumatoid nodules, and in two other cases the diagnosis was made only on the radiological findings.

3. The pathogenesis of this condition is discussed. It is suggested that cystic bone lesions in rheumatoid arthritis can arise either by replacement of subchondral bone by the rheumatoid process, or by the formation of rheumatoid nodules within the bone.

1. A case of massive osteolysis of the bones and soft tissues of the left foot is reported.

2. Arteriography revealed slowed circulation in the foot, hut the tumour vessels did not fill with contrast medium.

3. Two years after below-knee amputation of the left leg and four years after the onset of symptoms, the patient appeared to be free from disease.

1. Two cases of haemangioma of the patella are reported.

2. In one case pain alone brought the patient for treatment; in the other, a pathological fracture was the first symptom.

3. In neither case was a firm diagnosis made before excision and histological examination of the patella.

4. In each case a good result followed removal of the patella: this is probably the best method of treatment.

5. The literature relating to haemangioma of bone and to tumours of the patella is briefly reviewed.

1. A case of ulnar nerve compression at the wrist caused by rheumatoid arthritis producing motor and sensory changes is presented.

2. The diagnosis from compression at the elbow can be determined by electromyography.

3. It may be that lesions of the deep branch leading to motor changes only occur in rheumatoid arthritis more often than is suspected, their effects being hidden by the concomitant disease and its associated muscle wasting.

1. A case of late infection about a total knee prosthesis secondary to urinary tract infection is described, indicating that haematogenous spread of infection to a prosthetic joint can occur.

2. The prophylactic use of antibiotics to cover surgical and dental treatment and the energetic treatment of intercurrent infection are urged for patients with artificial joints.

3. Any conservative treatment of established infection in such cases should include complete excision of all necrotic material from the joint.

1. A case of dysphagia caused by a large cervical osteophyte is presented.

2. The literature from 1960 is reviewed, with special reference to the cases in which operation was done, and etiological factors are considered.

3. Excision of the osteophyte should in most cases be combined with fusion.

1. Trigger thumbs present at birth can be safely watched for twelve months because there is an expected spontaneous recovery rate of at least 30 per cent.

2. Trigger thumbs in children first noticed between the age of six to thirty months can be safely watched for six months because there is an expected spontaneous recovery rate of about 12 per cent.

3. Delayed operation left no residual contracture of the interphalangeal joint provided the release was done before the age of four years.

4. Operation is recommended if the child is over the age of three years when first seen.

1. Two cases of locking of the metacarpo-phalangeal joint of the index finger are presented.

2. A simple classification of metacarpo-phalangeal joint locking is suggested, and the clinical features of the two main groups—degenerative and spontaneous—are described.

3. A routine approach to the treatment of the condition is suggested.

1. Rosette strain gauges placed on the lateral surface of the right calcaneus of eight sheep allowed recordings of bone deformation to be made during walking and trotting on a moving belt. From these recordings the changing direction and magnitude of the principal strains and the maximum shear strain could be calculated.

2. The cancellous architecture of the ovine calcaneus, when viewed in lateral radiographs, is arranged in two trabecular tracts which intersect in the form of an arch. in all cases during the main weight-bearing period the direction of the principal strains varied little, and at the time of maximum deformation coincided with the direction of the underlying trabeculae. The principal compressive strain coincided with the direction of the trabeculae in the dorsal tract, The principal tensile strain with those in the plantar tract. At the point of trabecular intersection the principal strains were more nearly equal but they maintained their alignment with their respective trabecular tracts.

3. in this particular site the trajectorial theory of bone structure has found some experimental support.

1. Articular cartilage from immature rabbits was placed in and near the rabbit knee joints for periods up to ten weeks.

2. Autografts of articular cartilage when placed free in the joint soon became adherent to its synovial lining; the cartilage with its subchondral bone remained viable.

3. Homografts remained viable in the presence of joint fluid, but when in contact with synovium antigenic cellular reaction was produced early. The presence of subchondral bone intensified this reaction and led to graft invasion and destruction.

4. Partial thickness homografts of articular cartilage were also antigenic and were absorbed. When full thickness cartilage was used, this cellular invasion was resisted by the zone of provisional calcification which appeared to function as a physical barrier against antigenic cells of the host.

5. When placed in muscle, both autogenous and homogenous grafts failed to survive through lack of nutrition, although the autogenous subchondral bone remained viable. It is inferred that subchondral circulation is not sufficient for cartilage survival and synovial fluid is essential for its proper nutrition.

6. Surviving immature articular cartilage transplants underwent "ageing" changes.

1. A comparative study has been made of the major transplantation antigens present on the chondrocyte isolated from articular cartilage of the sheep and lymphocytes from the cartilage donors.

2. It has been shown that the chondrocyte possesses antigens of the major histocompatibility system in common with the lymphocyte.

3. In order to demonstrate the similarity between the antigen structure of the chondrocyte and the lymphocyte it was necessary to treat cartilage cells with papain after isolation in order to remove the matrix more completely. Failure to do this led to an apparent deficit of antigens on the chondrocyte.

4. It was found that lysis of cells by antibodies was slower when chondrocytes were the target cells than when lymphocytes were used. It is concluded that this is due to a protective role of remaining cartilage matrix.

1 . Implants of heterogenous cartilage are known to excite a foreign body reaction in host tissues. In these experiments the way such implants hinder the spread of ossification across a fracture gap was studied. A segment of bone and periosteum was excised from both fibulae in twelve young grivet monkeys, and epiphysial cartilage from a four-day- old rat was implanted in the gap on the left side. The repair processes were investigated at intervals up to twenty-eight weeks.

2. On both sides the gaps were filled by fibrous tissue growing in from the adjacent muscle, and four weeks elapsed before callus started to form. Thereafter ossification across the gap was active on the right side, with bony union in seven or eight weeks.

3. On the left side the implant was slowly resorbed by macrophages and giant cells. Ossification made little headway in the gap after the seventh week. Remains of the implant were found up to the end of the period covered by the experiment. The ends of the fragments were united by fibrous tissue.

4. The fifth to the eighth week seemed to be a critical period, during which the implant and its surrounding inflammatory cells hindered chondrification and ossification and prevented fusion of the masses of callus at the ends of the fragments.

5. It is concluded that anything that impedes callus formation across the fracture line during this critical period may lead to non-union.