Nerve Repair

Nerve repair surgically reconnects a lacerated peripheral nerve to restore sensation and muscle function in its distribution.

A divided nerve does not recover on its own. The fibres beyond the injury degenerate, and regrowth from the cut end has nowhere organised to go, producing permanent numbness, loss of muscle function and often a painful neuroma. Repair aligns the two ends accurately under magnification so that regenerating axons can find their original pathways. Where a gap exists that cannot be closed without tension, a graft or conduit is used to bridge it, because a repair under tension fails. Timing, accuracy and magnification are what determine the result.

Anyone with a divided peripheral nerve, most often from a laceration to the hand, wrist or forearm, diagnosed by loss of sensation in a specific nerve territory or loss of a specific muscle function rather than by the appearance of the wound. Repair is best done within days. Where presentation is delayed by weeks to months, direct repair may no longer be possible because of retraction and scarring, and nerve grafting or a tendon transfer is considered instead. Results are substantially better in children, in more distal injuries, in pure sensory nerves and in sharp clean divisions than in adults, proximal injuries, mixed nerves and crush or avulsion injuries.

Performed under regional or general anaesthesia, usually as a day case, under an operating microscope or high-magnification loupes. The wound is extended, both nerve ends are identified and trimmed back to healthy fascicular tissue, and the ends are aligned by matching the fascicular pattern and the surface vessels so that motor and sensory fibres are directed correctly. Very fine sutures are placed in the epineurium — enough to hold alignment, no more, since excess suture provokes scar. Where a gap remains, it is bridged with a nerve graft, most often sural, or with a conduit for short gaps in small sensory nerves. Any associated tendon, vessel or bone injury is addressed at the same operation, and the limb is splinted in a position that keeps the repair free of tension.

This is the longest recovery in hand surgery. The repair is protected in a splint for around three to four weeks before movement is progressed. Axons then regenerate from the repair site at approximately one millimetre per day, so the time to reach the fingertip from a wrist-level repair is roughly six to twelve months, and a progressing Tinel's sign along the nerve is used to follow it. Sensation returns in a sequence — deep touch, then moving touch, then light touch and discrimination — and sensory re-education with a hand therapist materially improves the functional result. Muscle recovery, where motor fibres were divided, must occur before the muscle atrophies irreversibly, which sets a practical limit of roughly twelve to eighteen months.

Incomplete recovery is the rule rather than the exception, and normal sensation is not a realistic expectation after repair of a mixed nerve in an adult; this is discussed explicitly before surgery. Painful neuroma, cold intolerance — which is common, persistent and often the most troublesome long-term symptom — and altered or misdirected sensation all occur. Failure of regeneration may require revision with grafting or a tendon transfer to restore function. Infection, stiffness of the splinted joints, and donor-site numbness where a graft was harvested are recognised. Smoking impairs nerve regeneration.