1. In thirty-six out of seventy-two cases of cervical vertebral interlocking, luxation was still present after two weeks ("old luxation"). The principal reasons for overlooking the diagnosis are lack of familiarity with the radiographic appearances and incomplete or inadequate radiographic examination.

2. Failure to identify luxation probably hardly influences the prognosis of the immediate cord lesion; but recovery from the radicular lesion is unfavourably affected, and a progressive cord lesion may occur later when none previously existed.

3. Reduction is advisable if the luxation is not more than six weeks old. Operative reduction is preferred; manual reduction under anaesthesia and caliper traction with heavy weights are less satisfactory alternatives. Reduction is contra-indicated if the luxation is more than six weeks old.

4. Indications for fixation and the choice between internal and external (plaster jacket) fixation are discussed, and also the treatment of stable lesions which have not been reduced.

Bilateral interlocking of the articular facets of the cervical spinal column results from excessive flexion. Unilateral interlocking (hemiluxation) results from simultaneous excessive flexion and rotation. Patients with hemiluxation of the cervical spine often have only mild complaints and the clinical signs may be slight. The diagnosis is made radiologically, but it is often overlooked.

Various forms of treatment may give good results. In recent hemiluxation, reduction is advisable to promote recovery of radicular symptoms. The effect of reduction on spinal cord symptoms is uncertain. Manual reduction under general anaesthesia is usually successful, with the possible exception of some cases of interlocking at C.6-C.7, or C.7-T.1. Skull traction with weights of 5 to 10 kilograms even when prolonged is hardly ever successful; with weights of 10 kilograms or more there is a chance of success. Surgical reduction is not always necessary. A hemiluxation of more than two weeks' standing may still be reduced but non-operative methods offer little chance of success. In this series there has been no aggravation of the neurological deficit after reduction. Although hemiluxation shows a tendency to spontaneous stabilisation it is wise in our opinion to apply some form of fixation. The selection of the method of fixation depends on the neurological picture and on the estimated degree of instability. The latter depends on the presence or absence of additional damage to the interlocked and adjacent vertebrae. Manual reduction by means of traction in the longitudinal axis of the cervical spine under general anaesthesia with muscle relaxation, followed by immobilisation in a plaster jacket (Minerva type) for three months is successful in many cases. If surgical stabilisation is considered necessary an attempt at manual reduction should be made before operation so that when the patient is placed on the table the cervical spinal canal has regained its normal shape. In general, sufficient stability will have been achieved after approximately three months, so that for hemiluxations of more than three months duration surgical treatment will only rarely be necessary. Figure 11 shows the methods of treatment that we advise.