Peripheral Nerve & Brachial Plexus | Repair, grafts and transfers

The key issue is tension, not just the cut. If the ends meet easily and stay relaxed, the outer nerve covering can be sewn under a microscope with fine sutures. If they must be pulled together, or nearby joints must be bent to reduce tension, direct repair is too tight and grafting is preferred. A gap under about 2 cm may allow primary repair, while larger gaps usually need grafting. Timing also matters: clean cuts are repaired early, while unclear injuries may need waiting for the damaged zone to settle before reconstruction. Microsurgical repair also requires healthy nerve ends and careful alignment, so the surgeon can match fascicles and vessels. This is assessed during surgery.

Nerve repair works best when healthy proximal and distal stumps are joined with little or no tension. If trimming damaged ends and mobilising the nerve would require more than about 10% elongation, or the gap is large, a graft may be used instead of pulling ends together. A 1 cm digital nerve gap may not be overcome directly; 4 cm is often used as a critical defect threshold, and a 6 cm gap is difficult without grafting. Delayed treatment can cause fibrosis that prevents approximation even without tissue loss. Grafts need a healthy bed and cannot be used in burned or irradiated tissue.

The sural nerve is usually chosen for a peripheral nerve graft because it is an outstanding source of graft material: it is long, up to about 40 cm, about 2–3 mm wide, and has relatively low donor-site morbidity. It lies in the back of the leg near the lesser saphenous vein and can be found at the outer ankle, halfway between the back of the outer ankle bone and the front of the Achilles tendon. Other donor nerves, such as forearm cutaneous nerves or the superficial radial nerve, are smaller and may not match as well. The choice depends on injury location, gap size, surgeon preference, and associated donor-site morbidity.

Nerve grafting keeps the original pathway but adds donor nerve between healthy stumps, so regeneration must travel the full distance and pass two joins, with possible axonal loss and donor-site morbidity. A nerve transfer instead converts a proximal injury into a distal one by using redundant nearby innervation, avoiding the injured zone and often shortening reinnervation time, and potentially stronger axonal input. It may be considered when the injury is far from target, presentation is delayed, scarring blocks safe dissection, or no proximal stump exists. The trade-off is that recovery depends heavily on motor re-education, and movements may not be fully spontaneous or emotional.

Nerve transfer attaches a functioning donor nerve to an injured nerve. Donor nerves are chosen because they are near the target muscle, have enough motor fibres, and are not essential for another important function. The donor nerve should be tested electrically, and the surgeon should avoid using one that may be needed later, such as for tendon transfer. Even with careful selection, donor-site weakness can occur, and recovery after nerve injury is often incomplete. Synergistic donor muscles can make retraining easier, while non-synergistic donors may make rehabilitation harder. The donor nerve should have a similar number of fibres to the recipient nerve when possible. Nerve transfers are not suitable when no redundant donor is available, such as in multi-nerve injuries.

Neurolysis means freeing a nerve from surrounding scar or compressing tissue; external neurolysis separates it from adherent structures, while internal neurolysis separates fascicles. It may be used for entrapment by fibro-osseous structures, or compression by hematoma, fibrous tissue or fracture fragments. If the nerve appears intact and conducts across the lesion, neurolysis may be performed with intraoperative electrodiagnostic studies. If exploration shows a neuroma in continuity that does not conduct a nerve action potential, or a rupture or transection, excision with grafting is preferred. Only mechanically caused damage is likely amenable to direct surgical treatment. The final choice depends on what is found at surgical exploration and on your goals.

A tendon transfer does not repair the nerve; it redistributes available power. The donor tendon must be expendable, strong enough and have similar movement to the tendon it replaces. Scar tissue or joint stiffness can make it less effective. If nerve recovery is still possible, surgeons often wait about four to six months and maintain passive joint motion; if recovery is not expected, the transfer may be permanent. Early transfers can act as a temporary internal splint. The plan is individualized because tendon transfer is palliative and does not restore full normal function. Each problem is individualized by loss of function, severity, reconstructive possibilities and patient needs.

It is a complex microsurgical transfer of a working muscle from a distant site, together with its blood supply and nerve, with microvascular anastomoses and neural coaptation, to replace a permanently lost critical upper-limb function. It is usually considered only after severe trauma, Volkmann ischemic contracture, extensive tumor removal, longstanding brachial plexus injury, electrical burns, gas gangrene or replantation, when no simpler local option such as nerve reconstruction, nerve transfer or tendon transfer is suitable. Selection also requires a motivated, compliant patient, adequate hand sensation, sufficient recipient vessels, a healthy adequately sized donor nerve, adequate soft-tissue cover, mobile joints and free tendons. Because muscle denervation becomes irreversible around 12–18 months, timing matters.

The plan is not one-size-fits-all. For complete pan-plexal injury, priorities include elbow flexion, shoulder stabilization, abduction and external rotation, hand sensation, wrist and finger flexion, wrist and finger extension, and intrinsic hand function. For children over 12, priorities resemble adults: elbow flexion, shoulder abduction or stability, hand sensation, wrist extension and finger flexion, wrist flexion and finger extension, and intrinsic hand function. Before surgery, the surgeon also considers injury level, available donor nerves, gap, scarring and your daily tasks; no single priority list fits every patient. Your expectations, desires and needs are critical and discussed with you before surgery; functional restoration, not just anatomical repair, guides reconstruction.