Bridging Long Nerve Defects: A Review of Microscopic Nerve Grafting Standards and Practices

Harilaos T. Sakellarides, MD

Disclosures
In This Article

Indications for Nerve Grafting

Primary nerve sutures remain the treatment of choice for the repair of divided peripheral nerves (Figures 1-3). Based on a series of 172 patients treated in 1961,[3] the following materials were identified as crucial for surgery: a clean incision, operating room (OR) assistance, appropriate OR facilities, fine instruments for microsurgery, and proper magnification. When used appropriately, these materials can be used to repair a 3-cm median motor sensory nerve defect, a 3- to 3.5-cm ulnar nerve defect, or a 3-cm radial nerve defect.

Epineural repair.

Perineural repair.

Group fascicular repair.

Nerve grafting is indicated when nerve suture is either impossible or undesirable. Specifically, in repairing median, ulnar, and radial nerves, grafting should be attempted if the nerve gap after mobilization of the nerve ends cannot be closed by 45° flexion of the elbow and 30° flexion of the wrist. As with primary nerve sutures, certain qualities that improve the chances of surgical success have been identified. The ideal nerve graft should be immunologically acceptable, should undergo Wallerian degeneration, should contain active nerve cells, and should become vascularized after being placed in a favorable nourished bed.[4] The primary sources of nerve grafts include: (1) sural nerves; (2) superficial radial nerves; (3) medial and lateral cutaneous nerves of the forearm; (4) medial and lateral cutaneous nerves of the arm; (5) posterior cutaneous nerve of the thigh; and (6) anterolateral femoral cutaneous nerve of the thigh.

During the last 30 years, a magnification of 2.5X has been used in a large number of peripheral nerve injuries. However, the results were not satisfactory. Extensive mobilization of the ends of the nerve resulted in limited blood supply to the nerve segments and scar tissue formation. Consequently, nerve regeneration was delayed or impossible. In addition, standard procedure called for immobilization of the joints in acute flexion in order to make the nerve suture possible. However, mobilization of the extremity after 4-5 weeks of immobilization caused stretching at the suture line and interstitial fibrosis, which, in turn, interfered with distal advancement of the regenerating proximal nerve fibers.

Some of the complications seen in the past may also have been a function of the timing of surgery: injured nerves were often repaired many months, or even years, after the original injury. Atrophic changes that had taken place in the paralyzed muscles prevented motor recovery. Resection of the neuroma was therefore often inadequate, and favorable results were hindered.

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