Neurotization of free gracilis transfer with the brachialis branch of the musculocutaneous nerve to restore finger and thumb flexion in lower trunk brachial plexus injury: an anatomical study and case report

Abstract

Objective: To investigate the feasibility of using free gracilis muscle transfer along with the brachialis muscle branch of the musculocutaneous nerve to restore finger and thumb flexion in lower trunk brachial plexus injury according to an anatomical study and a case report.

Methods: Thirty formalin-fixed upper extremities from 15 adult cadavers were used in this study. The distance from the point at which the brachialis muscle branch of the musculocutaneous nerve originates to the midpoint of the humeral condylar was measured, as well as the length, diameter, course and branch type of the brachialis muscle branch of the musculocutaneous nerve. An 18-year-old male who sustained an injury to the left brachial plexus underwent free gracilis transfer using the brachialis muscle branch of the musculocutaneous nerve as the donor nerve to restore finger and thumb flexion. Elbow flexion power and hand grip strength were recorded according to British Medical Research Council standards. Postoperative measures of the total active motion of the fingers were obtained monthly.

Results: The mean length and diameter of the brachialis muscle branch of the musculocutaneous nerve were 52.66±6.45 and 1.39±0.09 mm, respectively, and three branching types were observed. For the patient, the first gracilis contraction occurred during the 4th month. A noticeable improvement was observed in digit flexion one year later; the muscle power was M4, and the total active motion of the fingers was 209°.

Conclusions: Repairing injury to the lower trunk of the brachial plexus by transferring the brachialis muscle branch of the musculocutaneous nerve to the anterior branch of the obturator nerve using a tension-free direct suture is technically feasible, and the clinical outcome was satisfactory in a single surgical patient.

Figure 1

Photograph showing the nerve branching from the musculocutaneous nerve that innervates the brachialis muscle. Musculocutaneous nerve; Brachialis muscle branch of musculocutaneous nerve; Median nerve; Lateral antebrachial cutaneous nerve.

Figure 2

Photographs showing that the strength of finger and thumb flexion was M0.

Figure 3

The preoperative surgical plan. Musculocutaneous nerve; Brachialis muscle; Gracilis muscle; flexion.

Figure 4

The gracilis was harvested along with the anterior branch of the obturator nerve and its vascular supply. A skin paddle was designed to facilitate postoperative flap monitoring (a). The harvested gracilis was placed beside the left arm (b). The harvested gracilis was placed inside the left forearm (c). The anterior branch of the obturator nerve of the gracilis was anastomosed to the brachialis muscle branch of the musculocutaneous nerve (arrow indicates the site of the anastomosis) (d). Schematic diagram of the operation (e).

Figure 5

Photographs showing that the transection of the brachialis muscle branch of the musculocutaneous nerve did not cause functional impairment of the elbow when the cast was removed after the first month (a, b). One year after the operation, a noticeable improvement was observed in digit flexion due to gracilis contraction (arrow). The muscle power was M4 (c, d).

Figure 6

Photograph showing the patient holding a bottle at 12 months postoperatively.