Objectives: Our study was conducted to define the anatomy of the deep motor branch of the ulnar nerve based on known and recognizable landmarks of the hand. We sought to define the approximate location of the nerve along its course to aid surgeons in recognizing potential areas of injury during other procedures involving the hand.



Methods: Our study was performed using 10 fresh, frozen, matched cadavers harvested at the level of the distal forearm. The dissections were performed by and under the supervision of four fellowship-trained hand surgeons. The ulnar nerve was identified proximal to the Guyon canal and traced distally. The deep motor branch of the ulnar nerve was then dissected along its deep course until the level of its insertion into the adductor pollicis muscle.



Results: The deep motor branch of the ulnar nerve was described along its entire anatomic path in relation to each metacarpal and the carpal tunnel. The nerve sits proximal to the digital palmar crease at the level of the respective metacarpal at a distance of 61mm – 64mm. The nerve was always deep to the flexor tendons and distal to the distal edge of the transverse carpal ligament by an average of 11mm. The nerve was consistently found deep and proximal to the superficial palmar arch.



Conclusion: Thorough understanding of the anatomy of the deep motor branch of the ulnar nerve is of critical importance when performing surgeries of the hand. Knowing the nerve’s relative position in relation to identifiable landmarks can aid in preventing injury to the nerve and preserving the critical function of the hand intrinsic musculature.