Anatomical Relationships among the Median Nerve Thenar Branch, Superficial Palmar Arch, and Transverse Carpal Ligament

Background: A possible complication of open, limited incision or endoscopic carpal tunnel release is transection of the thenar branch of the median nerve or the superficial palmar arch. Knowledge of the anatomy of these structures in relationship to the transverse carpal ligament is critical in preventing these complications. The authors investigated these anatomical relationships using cadaveric dissections. Methods: Forty-eight fresh cadaver hands were analyzed. The distance between the distal transverse carpal ligament and the superficial palmar arch, the distance between the distal transverse carpal ligament and the origin of the thenar branch of the median nerve, and the length of the transverse carpal ligament were measured. Results: In the 48 specimens, the thenar branch of the median nerve was extraligamentous in 44 (92 percent), subligamentous zero (0 percent), and transligamentous in four (8 percent). The thenar branch of the median nerve contained one branch in 28 (58 percent) and multiple branches in 20 specimens (42 percent). The average distance from the distal transverse carpal ligament to the superficial palmar arch was 18.8 ± 0.6 mm (95 percent CI, 17.6 to 20.1 mm) and that to the thenar branch of the median nerve was 6.9 ± 0.4 mm (95 percent CI, 6.0 to 7.8 mm) (p < 0.0001). The average length of the transverse carpal ligament was 28.5 ± 0.8 mm (95 percent CI, 26.9 to 30.1 mm). Conclusions: The anatomical relationships among the superficial palmar arch, thenar branch of the median nerve, and distal transverse carpal ligament were found to be consistent. This will assist the hand surgeon in preventing specific complications regardless of the method of carpal tunnel release chosen.