We have measured anterior and posterior displacement in 563 normal knees and 487 knees with chronic deficiency of the anterior cruciate ligament (ACL). We performed stress radiography using a simple apparatus which maintained the knee at 20° of flexion while a 9 kg load was applied. There was no significant difference in posterior translation dependent on the condition of the ACL. Measurement of anterior translation in the medial compartment proved to be more reliable than in the lateral compartment for the diagnosis of rupture of the ACL, with better specificity, sensitivity and predictive values.

We have classified anterior laxity based on the differential anterior translation of the medial compartment and identified four grades in each of which we can further distinguish four subgrades for laxity of the lateral compartment. Within each of these subgroups, either internal or external rotation may dominate and sometimes there is a major translation of both compartments.

Radiological evaluation of displacement of the knee in 20° of flexion provides conclusive evidence of rupture of the ACL. A detailed study of pathological displacement is the basis for a classification of laxity. It is then possible to decide for each type of laxity, the surgical treatment which is specifically adapted to the lesion, and to define a reference value for judging outcome.

In this study, we discuss 68 cases in which peripheral nerve trunks were inadvertently divided by surgeons. Most of these accidents occurred in the course of planned operations. Delay in diagnosis and in effecting repair was common. We list the nerves particularly at risk and the operations in which special care is needed. We recommend steps to secure prompt diagnosis and early treatment.

1. Forty-seven tibial nerves of rabbits were stretched, twenty-four gradually by the Instron machine and twenty-three suddenly by dropping a load. The stretched nerves were examined histologically throughout their length.

2. Nerve trunks possess a high degree of elasticity, which is mainly a feature of the epineurium.

3. The initial elongation of the nerve is due to extension of the epineurium and straightening of the funiculi and of the nerve fibres. Such elongation is "physiological" in the sense that it does not affect the nerve fibres.

4. The first structure to be ruptured during stretching is the epineurium ; this occurs when the nerve trunk has reached its limit of elasticity.

5. Before rupture of the epineurium the damage to the nerve fibres is either neurapraxia or axonotmesis, because the endoneurial sheaths and Schwann tubes remain intact.

6. Beyond the limit of elasticity very severe damage of the nerve trunk occurs; all elements of the nerve may be ruptured. If less violent force is applied, some funiculi may survive. The longitudinal extent of the lesion is always great, reaching 2 to 5 centimetres in the rabbit.

We describe a new surgical technique for the treatment of lacerations of the extensor tendon in zone I, which involves a tenodesis using a length of palmaris longus tendon one-quarter of its width. After exposing the dorsal aspect of the distal interphalangeal joint and harvesting the tendon, a 1.5 mm drill bit is passed through the insertion of the extensor tendon into the distal phalanx where it penetrates through the skin of the pulp of the digit. The palmaris longus tendon is threaded through the drill hole from dorsal to ventral and the ventral end is tied in a simple knot and trimmed. The palmaris longus tendon is then sutured to the extensor tendon close to its insertion, and also at the middle of the middle phalanx.

The operation was undertaken on 67 patients: 27 with an acute injury and 40 patients with a chronic mallet deformity. One finger (or the thumb) was involved in each patient. At a mean follow-up of 12 months (6 to 18), 66 patients (98.5%) received excellent or good results according to both the American Society for Surgery of the Hand (ASSH) classification and Miller’s classification.

Tenodesis using palmaris longus tendon after complete division of an extensor tendon in zone 1 is a reliable form of treatment for isolated acute or chronic ruptures.