Unveiling Nerve Match in Free Gracilis Muscle Transplantation: A Comprehensive Anatomical Investigation

Objective: To evaluate the compatibility between common donor nerves such as the accessory nerve, phrenic nerve, and intercostal nerves in terms of cross-sectional area and the number of myelinated nerve fibers, compared with the obturator nerve's anterior branch to the gracilis muscle. Methods: Six fresh frozen cadavers were dissected to expose the accessory nerve, phrenic nerve, intercostal nerves, and the anterior branch of the obturator nerve to the gracilis muscle. Measurements of cross-sectional area, and the number of myelinated nerve fibers were taken. Results: The number of myelinated nerve fibers in the gracilis muscle nerve was 2870.56 ± 1216.99, with a cross-sectional area of 0.56 ± 0.24 mm²; the accessory nerve had 2210.55 ± 1461.82 myelinated nerve fibers with a cross-sectional area of 0.43 ± 0.28, giving a fiber ratio of 0.77 compared to the gracilis muscle nerve; the phrenic nerve had 2845.65 ± 765.40 myelinated nerve fibers with a cross-sectional area of 0.55 ± 0.15, giving a fiber ratio of 0.99. The detailed counts of myelinated nerve fibers, cross-sectional areas, and their ratios compared to the gracilis muscle nerve for each intercostal nerve are presented in Table-1 and Table-2. Conclusion： This study focuses on optimal nerve matching in functional muscle transplantation for brachial plexus injury reconstruction using FMT. Findings indicate a 0.7 ratio as optimal when using three intercostal nerves, compared to 0.77 and 0.99 for SAN and phrenic nerve matches, respectively.