INTRODUCTION: Triangular fibrocartilage (TFC) injuries are being increasingly recognized as a cause of ulnar sided wrist pain, and arthroscopic repair is a successful technique for certain types of tears. This anatomical study of the commonly described inside-out Tuohy needle technique was performed to better define the course of needle passage relative to the anatomic structures in this region including the dorsal sensory branch of the ulnar nerve (DBUN) and extensor carpi ulnaris (ECU) tendon. METHODS: Ten fresh-frozen cadaveric specimens underwent arthroscopic guided passage of a Tuohy needle through the TFC. Dissection of the ulnar side of the wrist was performed and various measurements recorded. RESULTS: The average minimum distance between suture A (the suture closest to the nerve) and the DBUN was 1.9 mm. The average minimum distance between suture B and the DBUN was 2.7 mm. The distance between the two sutures at the level of the capsule averaged 6.2 mm. The distance between the DBUN and the ECU averaged 7.2 mm. In 5 of 10 specimens, the sutures exited on opposite sides of the DBUN. DISCUSSION AND CONCLUSION: The DBUN is variable in its course but in every case it passes in close proximity to the sutures that exit the ulnar side of the wrist in arthroscopic repair of ulnar sided TFC tears. This study supports the use of a longitudinal incisionon the ulnar side of the wrist with dissection limited just to that necessary to identify the DBUN. In this way, injury during needle passage can be avoided.