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 1.5Â 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.
