1. Primary lumbar vertebral instability or "pseudo-spondylolisthesis" varies from about 3 millimetres to 1·7 centimetres, and is perhaps the commonest radiological sign associated with lumbo-sacral pain after the third decade of life. It was observed in 28·6 per cent of 500 consecutive cases of lumbo-sacral pain. The next commonest cause is gross disc degeneration, which is a late result of instability.

2. The secondary instability that may accompany a nuclear prolapse or osteoarthritis is excluded from this discussion.

3. This lumbar instability is an early sign of "incipient disc degeneration," occurring before narrowing of the disc space, sclerosis of the epiphysial rings, or osteophyte formation becomes evident. The instability in the lower lumbar region is caused by incomplete radial posterior tears, usually between the fourth and fifth lumbar vertebrae; and in the upper lumbar region from anterior concentric fissures or slits between some of the lamellae of the annulus fibrosus.

4. As shown radiologically, lumbar instability is commonest between L.4-5 and is rare between L.5 and sacrum because the facets between L.5-S.1 normally face forwards and backwards and thus resist anterior sliding.

5. The usual direction of antero-posterior sliding in the case of the upper four lumbar vertebrae is posterior—that is, the upper vertebra is displaced backwards on the one immediately below it during full extension in the erect position. The displacement tends to disappear on forced flexion, which may cause anterior displacement. On the other hand, the reverse displacement may exist between the fifth lumbar vertebra and the sacrum.

6. Operative treatment by bone grafting is a last resort in carefully selected individuals. After operation the patient rests in bed for three months without rigid splinting. Bone grafting is best for a localised lesion (affecting only one disc); it is generally not advisable if more than two discs are involved.

7. The results in thirty patients treated by spinal fusions showed that 70 per cent had no pain and resumed work, l3·3 per cent had improvement and resumed work, and l6·7 per cent were worse or no better.

1. Seventy-five injuries of the cervical spine are reported. Fifty-three were dislocations and fracture-dislocations involving the third to the seventh segments.

2. The importance of careful examination in all neck injuries is stressed.

3. The injuries are divided into stable and unstable types and the causation of the instability is discussed.

4. Plaster immobilisation for more than six months failed in some patients to prevent recurrence of dislocation.

5. Operative treatment was advised in all cases of dislocation, the spine being wired and grafted with iliac bone. This prevents recurrence and shortens the period of convalescence.

A case of pseudohypoparathyroidism is reported. The clinical, biochemical and radiological findings are described. There was a satisfactory response to large doses of Calciferol.

We adduce the following conclusions from our experience of using this spring-loaded compression screw on completely displaced medial fractures of the femoral neck:

1. That this method probably eliminates non-union when the head is fully viable.

2. That primary "first-intention" osseous union occurs in approximately 33·3 per cent of cases.

3. That a vascular complication, of varying severity, undetectable by orthodox radiological tests, is revealed by extrusion of the screw in 66·6 per cent of cases.

4. That these observations disprove the idea that the main obstacle to revascularisation of an ischaemic head is the existence of forces so inclined to the axis of the femoral neck as to cause "shear."

5. That, compared with the Smith-Petersen nail used for completely displaced fractures, continuous spring compression can materially reduce the incidence of utter mechanical failure within the first year after operation. This is the result of "mushroom" impaction which itself can resist shearing strain and so can permit function as a fibrous union.

6. That early and rapid extrusion is a sensitive indication of a vascular complication in the head. Forewarned by this, activity can be restricted, or possibly other measures adopted, to anticipate or permanently postpone serious trouble.

The records of these patients show that restitution of joint function is quite possible even after severe disease. These results have been obtained by a combination of three methods, constitutional, antibiotic and operative. The duration of treatment averaged ten months and the patients were discharged to full activities in a short time without splints. There was one immediate failure in a child who received full, early and adequate treatment. There were two late relapses in patients treated early in the series whose operation was inadequate. The results were more variable in adults. If it is conceded that the triple treatment is valuable for patients with bone necrosis or severe synovial disease with pus in the joint, eight patients in this series remain who might have got better without operation. Two of these had had a synovial biopsy before admission. Whether the remaining six would have done as well without operation is a matter for speculation. It is difficult to assess the condition inside the joint solely by radiographic examination. Cauchoix (1955) allows me to say that, at the Institut Calot, Berck Plage, he has used similar methods to those reported in this paper, and that he endorses my belief that good results can be obtained by them. He does not, however, open the joint when operating upon an iliac focus, and for patients with purely synovial disease he prefers repeated intra-articular injections of streptomycin to operation. For my part, I consider that a simple arthrotomy at the beginning of treatment is less disturbing, and that, even if it is only done for diagnosis, it may be of therapeutic benefit. To me it seems unjustifiable to delay intra-articular operation for a patient whose hip disease is not manifestly resolving: operation is especially indicated for patients who have necrotic bone lesions.

1. Radiological criteria in the diagnosis of congenital dislocation of the head of the radius are suggested.

2. Some of the radiographic features described as characteristic of congenital dislocation of the head of the radius may be found also in post-traumatic dislocation of the radial head.

1. Forty-four patients with tuberculous tenosynovitis have been reviewed.

2. The lesions (fifty-two in all) are classified and described according to their anatomical sites.

3. Particular reference is made to the natural history of the condition and the results of treatment.

4. Early and extensive excision of the affected tendon sheaths combined with the use of anti-tuberculous drugs is recommended.

1. The clinical appearance and histological structure of a myo-epithelial tumour of a sweat gland of the hand is described.

2. A review of previously published papers is given.

3. It is suggested that trauma may play a part in the causation of these tumours.

1. The condition of persistent foetal alignment is discussed both as an entity and in its relationship to the development of a normal hip, and also to the varying degrees of congenital dislocation of the hip. A possible connection with osteoarthritis is also mentioned.

2. The secondary deformities to which it may give rise are discussed, and the way in which both primary and secondary deformities may be corrected is described.

3. The importance of estimating rotation with the hip in full extension is emphasised.

4. The results in eight patients so treated are mentioned.

1. Fifty cases of recurrent dislocation of the shoulder are reported, operated upon by Bankart and his colleagues from 1925 to 1954.

2. This is the first detailed survey of his patients, some of whom we were unable to trace.

3. It has been confirmed that the operation is successful, and that a full range of movement can be regained after operation, though not in every case.

4. Two cases treated unsuccessfully are described and discussed.

1. Bones consist essentially of bundles of collagenous fibres united by a cementing substance in which the inorganic material lies in the form of minute plate-like crystals.

2. During weight bearing and muscle action bones as a whole are deformed to a variable extent. Periods of deformation are followed by periods of relaxed pressure during which the bones tend to return to their normal form.

3. These variations in deformation and elastic recoil set up alternating pressures and tensions within the bones along the bone cyrstal encrusted fibres which make up the trabeculae, lamellae and Haversian systems, and these alternating phases of compression and tension stimulate the activity of osteoblasts so that bone formation predominates over bone resorption.

4. These alterations of pressure and tension are intermittent and reciprocal in nature and do not, as postulated by the trajectorial theory, involve different trabeculae, nor is it necessary to consider whether tension or pressure is the more important phase in determining bone deposition.

5. The pressure exerted by cysts, tumours, erupting teeth, etc., is of a quite different nature, as is the response to trauma or callus formation in the healing of fractures. These processes are essentially vascular phenomena involving localised areas of bony tissue and not bones as mechanical units.

Photoelastic techniques were used to study the stresses in models which represented the central frontal plane of a normal hip joint. The pelvis and the femur were inclined and the direction of the resultant thrust on the joint was estimated. Inward tilting of the pelvis causes a force which tends to push the head of the femur out of joint.

The load distribution on the joint is not significantly changed if the line of action of the load is moved relative to the joint. The directions of the lines of principal stress in both bones are shown.