Sciatic nerve palsy is a recognised complication of primary total hip replacement. In our unit this complication was rare with an incidence of < 0.2% in the past ten years. We describe six cases of sciatic nerve palsy occurring in 355 consecutive primary total hip replacements (incidence 1.69%). Each of these palsies was caused by post-operative haematoma in the region of the sciatic nerve.

Cases, which were recognised early and surgically-evacuated promptly, showed earlier and more complete recovery. Those patients for whom the diagnosis was delayed, and who were therefore managed expectantly, showed little or no recovery. Unexpected pain and significant swelling in the buttock, as well as signs of sciatic nerve irritation, suggest the presence of haematoma in the region of the sciatic nerve.

It is, therefore, of prime importance to be vigilant for the features of a sciatic nerve palsy in the early post-operative period as, when recognised and treated early, the injury to the sciatic nerve may be reversed.

Supracondylar osteotomy for traumatic cubitus varus is usually considered to be difficult, and to have a significant incidence of complications. Most difficulty is in maintaining correction after operation. We report 20 osteotomies performed by a modification of French's technique and managed postoperatively with the elbow extended. When a plaster splint was used only three of seven cases had good or satisfactory results, two requiring revision. Postoperative management by straight arm traction maintained correction and achieved a good or satisfactory result in all 13 cases. This new technique is recommended.

Complete dislocation of the knee is a relatively rare condition. When it occurs as a result of high-velocity injury, such as in a road traffic accident, associated vascular injury is generally suspected. In low-velocity injuries, however, distal pulses are often maintained throughout, and the possibility of vascular injury may erroneously be discounted. We report four cases of low-velocity dislocation of the knee, only one of which had an overt vascular disruption, but three of which had arterial damage. On the basis of our experiences, we recommend arteriography in all cases of complete dislocation of the knee.

The detection and recording of vibration emission from human joints, a technique which we have termed "vibration arthrography", is a sensitive, non-invasive method for the objective study of the locomotor system. Using vibration sensors attached to bony prominences around the knee, we studied the joints of both normal and symptomatic subjects. Normal subjects produced three signal types--physiological patellofemoral crepitus, patellar clicks, and the lateral band signal. In symptomatic subjects we identified and categorised many signal types and related them to pathology. Lesions of the menisci produced distinctive signals, and it was possible not only to lateralise the tear, but in many cases to determine the type of meniscal injury present. Vibration arthrography promises to be a useful tool in the non-invasive diagnosis of knee disorders.

Ninety-eight children with severely displaced supracondylar fractures of the humerus were treated by straight lateral traction. After a mean follow-up period of 3.5 years there were 90 satisfactory and only eight unsatisfactory results. Cubitus varus was present in only four children, which compares favourably with the results of operative treatment. The indications for straight lateral traction, and the advantages of this method, are discussed.

A case of locked hypersupination of the distal radio-ulnar joint is described in which the ulnar displacement was purely rotational rather than volar. The mechanism of injury is discussed in the light of cadaveric dissections which reproduced the injury.

Serious neck injury in rugby football is becoming more common, especially in schoolboys. We report five who presented with spinal cord damage between 1977 and 1983, two in the 1982-83 season. The mechanisms of injury, the treatment, and the outcome are discussed. We suggest measures to reduce the incidence of this most serious injury and draw attention to the appropriate management in the critical phase directly after injury.