An Anatomical Study of the Palmaris Brevis, Transverse Carpal Ligament, and the Recurrent Motor Branch of the Median Nerve

Background: The anatomical structures in relation to the carpal tunnel release are the palmaris brevis muscle (PBM), transverse carpal ligament (TCL), and the recurrent motor branch of the median nerve (RMBMN). Our aim is to describe the gross morphology in the Korean population of the PBM, TCL, and RMBMN specifically looking for anomalies, and to determine the muscles encountered during a standard carpal tunnel release. Material and Methods: A total of 30 cadaveric hands were dissected. A longitudinal line drawn from the third web space to the midpoint of the distal wrist crease served as the reference line (RI). The PBM and TCL were classified according to its shape and location. The length, width, and thickness of the TCL were measured. The ratio of the lengths of PBM and TCL to RI was calculated. The course of the RMBMN was dissected specifically looking for anomalies. We also looked at the muscle fibers encountered during a standard carpal tunnel release to identify the muscle. Results: PBM was classified into three different types based on the shape. The average thickness of the PBM and TCL were 0.89 +/- 0.16 mm and 1.43 +/- 0.40 mm, respectively. The distal border of the TCL was thicker than the proximal border. The average ratio of the length of the PBM to the RL was 25.65 +/- 8.62% and TCL to the RL was 24.00 +/- 3.37%. The distribution of the RMBMN was classified into three different types. A few accessory branches of the RMBMN were also noted. And 36 muscle fibers were noted within the TCL in line with the RL. Conclusion: We clarified findings and added quantitative information about the anatomical structures surrounding carpal tunnel. A thorough knowledge of the anatomy and anomalies around the carpal tunnel is helpful for surgeons to ensure optimal surgical results.