Effects of varying periods of immobilization of a limb on the morphology of a peripheral nerve.

Immobilization of a hind limb of the cat in the resting position was found to result in morphological changes in the nerve supplying the medial head of the gastrocnemius muscle. A reduction in the diameter of the larger myelinated fibres (greater than 12 micrometers) concomitant with a reduction in the mean fibre diameter of the nerve were observed. This reduction in the mean fibre diameter of the nerve was found to be directly proportional to the period of immobilization. Prolonged immobilization beyond 8 weeks, resulted in the splitting of the myelin lamellae, formation of myelin rings and figures in some of the larger axons in addition to an abundant increase in collagen. These structural changes indicate a definite neural involvement in the disuse atrophy of the muscle as a result of immobilization extending for a period of 8 weeks and above.