Modified Partial Radial to Axillary Nerve Transfer.

Abstract

Background: Nerve transfers are routinely performed in patients with brachial plexus injuries because these patients have limited alternative solutions secondary to their severe injury with substantial functional limitations^5,6. Nerve transfers offer distinct advantages over other surgical options, as they are able not only to bypass the zone of injury but also to decrease regeneration time because of the proximity of the motor end plate to the repair site^1,2. It is for this latter reason that a nerve transfer should be considered for an isolated axillary nerve injury, in which a full recovery is of paramount importance for shoulder function. Accordingly, surgeons should consider a partial radial to axillary nerve transfer as an option for restoring shoulder function.

Description: The procedure is performed with the patient in the lateral decubitus position after induction of anesthesia without the use of paralytics. An incision is made via a longitudinal, posterior approach to the proximal humerus. Careful dissection is performed to separate the brachial fascia from the triceps muscle. Following visualization of the radial nerve and profunda brachii within the triangular interval, the radial nerve is traced distally to identify each of its distinct branches. An intraoperative nerve stimulator is utilized to identify which branch of the radial nerve only supplies triceps extension and does not contribute to wrist or digital extension. This distinct branch is dissected proximally to the inferior border of the teres major. Next, the fascia overlying the inferior one-third of the teres major is released without damaging the underlying muscle fibers in order to prevent a tether point for the transferred branch of the radial nerve. The nerve stimulator is useful to confirm intraoperatively if the axillary nerve has been transected or if there are nerve fibers in continuity. For the former situation, the nerve transfer is performed in an end-to-end manner. For the latter situation, the isolated branch of the radial nerve is coapted in an end-to-side manner to the axillary nerve. Once both the donor radial nerve branch and the recipient axillary nerve have been isolated, the radial nerve is transposed superiorly to meet the axillary nerve. The nerve ends are coapted with 8-0 or 9-0 nylon simple interrupted sutures under the operating microscope, utilizing fibrin glue as an adjunct. The shoulder and elbow are manipulated passively in abduction and external rotation while directly visualizing the coaptation site to ensure the nerve is not under tension. The fascial, subcutaneous, and skin layers are closed to complete the procedure.

Alternatives: Surgical alternatives include neurorrhaphy with grafting, nerve grafting, tendon transfer, muscle transfer, arthrodesis⁴, and nonoperative treatment.

Rationale: In patients experiencing persistent axillary nerve paralysis, partial radial to axillary nerve transfer is an option for functional recovery of shoulder forward flexion and abduction. The radial nerve is an ideal donor nerve because (1) triceps action is synergistic with shoulder abduction and (2) there are most often redundant branches of the radial nerve that allow for a nerve transfer with limited to no functional deficit⁵.

Expected outcomes: Patients undergoing radial to axillary nerve transfer can expect increased MRC (Medical Research Council) scores and range of motion in cases with a time from injury to surgery of <6 months^3,6.

Important tips: The use of a nerve stimulator is critical to identify the branch of the radial nerve that innervates triceps extension but that does not contribute to wrist or digital extension.Positioning the arm in full forward flexion, abduction, and external rotation intraoperatively can help to confirm that there is no tension between the nerve ends and that there is adequate nerve mobilization to achieve tension-free closure.

Acronyms and abbreviations: MRC = Medical Research CouncilROM = range of motionEMG = electromyogram.