An Anatomical Feasibility Study on the Use of the Hypoglossal and Hemihypoglossal Nerve as a Donor Motor Nerve for Free Functioning Muscle Transfer in Upper Extremity Reconstruction.

ABSTRACT

PURPOSE: Brachial plexus injuries (BPI) with complete root avulsions remains a clinical challenge due to a paucity of nerves available for nerve transfer and innervation of free functioning muscle transfers (FFMT). The hypoglossal and hemihypoglossal nerve has not been studied as a donor nerve option for FFMTs in brachial plexus reconstruction, despite successful outcomes of hypoglossal nerve transfers in facial reanimation surgery. We hypothesized that the hypoglossal nerve could be an appropriate candidate for surgical repair of BPI using FFMT. METHODS: A cadaveric study was performed to determine the anatomic feasibility of using the hypoglossal and hemihypoglossal nerves as donor nerves to neurotize the gracilis or latissimus dorsi muscle in an FFMT to restore elbow flexion. Twelve cadavers (6 males and 6 females) were studied. The hypoglossal nerve, thoracodorsal nerve, and obturator nerve branches to the gracilis muscle were dissected, measured, and analyzed. RESULTS: The average length of the hypoglossal nerve was 6.3 ± 0.5 cm in both sexes. The average distance between the lowest point of the hypoglossal nerve and the lateral clavicle was 8.4 ± 1.3 cm in males and 7.7 ± 0.8 cm in females. When the hypoglossal nerve was transected distally, the average distance to the clavicle was 4.5 ± 1.6 cm in males and 3.8 ± 1.5 cm in females. CONCLUSIONS: The maximum theoretical length of the donor nerve required to perform an adequate FFMT using the hypoglossal nerve was 8.9 ± 1.2 cm, which was well exceeded by the lengths of the thoracodorsal nerve (14.5 ± 1.3 cm) and nerve to the gracilis muscle (12.7 ± 1.7 cm). CLINICAL RELEVANCE This cadaveric study demonstrated that the hypoglossal or hemihypoglossal nerves may be used as potential motor donor nerves to innervate a free gracilis or latissimus dorsi muscle transfer for the restoration of elbow flexion via a direct nerve transfer without the need for nerve grafting.