Timing and technique of peripheral nerve repair.

Surgery of the peripheral nerves is briefly reviewed with special emphasis on the timing and the techniques of nerve repair. The sooner a severed nerve can be repaired, the better the quality of the recovery. While delays of a few months after injury appear to have no serious effect on the out come of nerve sutures, the chances of successful recovery decline after six months. It is not common for markedly good recovery to follows nerve suture a year or more after injury. Investigation of the local neuropathological factors and the metabolic changes within the neuron suggests that, in the divided nerve, the interrupted fascicles should be sutured as soon as the longitudinal extent of the injury can be accurately determined. A short delay in nerve repair, however, is often indicated when successful regeneration of the budding neuron across a repair site is thought possible. The possibility for recovery of a lesion in continuity can be predicted eight to twelve weeks after injury by recording nerve action potentials. Nerve action potential recording in the early months after injury allows identification of partial injury and the neuroapraxic element of an injury. It also provides a measure of relatively early regeneration. The traditional method of repairing peripheral nerves has been the epineurial suture. Concern over the reaction to suture materials which might interfere with nerve re generation resulted in the search for sutureless methods of uniting the nerve ends. Plasma clot maintains the nerve ends in apposition and does not appear to set up any reaction, but it is absorbed before natural healing has effected a firm union at the nerve ends. Sheathing methods have been designed to hold the nerve ends together and protect the junctional zone by an encircling tube of biological or non-biological materials, and at the same time confine regenerating axons to the suture line by preventing them from straying further afield. None of these methods has eliminated the malalignment of axons and is suitable for large nerves or nerve sutures with a tension on the suture line. A good epineurial closure does not always mean that all of the internal architecture of the nerve has been restored. Funicular nerve suture to improve the results of nerve repair was discussed by Langley and Hashimoto as early as 1917. By careful approxi mation of the corresponding fascicles, this method can improve the quality of the recovery after nerve suture by preventing the wasteful regeneration of axons outside funiculi and their entry into functionally unrelated endoneurial tubes. With the increasingly wide use of the operating microscope in neurosurgical practice, it is now clear that this method can be applied more generally.