Intraneural Median Nerve Anatomy and Implications for Treating Mixed Median Nerve Injury in the Hand

Background: Nerve transfers have resulted in increased interest in the microanatomy of peripheral nerves. Herein, we expand our understanding of the internal anatomy of the digital nerve to the ulnar index and long fingers, the radial long and ring fingers, and the nerves to the second and third web spaces. Methods: The median nerve was dissected from the digital nerves to the antecubital fossa in 14 fresh upper extremities. The distance of proximal internal neurolysis of the fascicles to the second and third web space and proper digital nerves was measured relative to the radial styloid. Plexi encountered during proximal lysis were noted. Results: Digital nerves to the ulnar index and radial long fingers were lysed 2.4 ± 0.5 cm (mean ± SD), and digital nerves to the ulnar long and the radial ring fingers were lysed 3.0 ± 0.6 cm distal to the radial styloid. Fascicles to the third web space were lysed to the takeoff of the anterior interosseous nerve, 21.1 ± 1.4 cm. Plexus groupings were encountered at 4.5 ± 1.6 cm, 8.3 ± 1.2, cm and 16.1 ± 1.9 cm proximal to radial styloid. The fascicles to the second web space were lysed to 5.0 ± 1.2 cm proximal to radial styloid where a plexus grouping was encountered. Another plexus group was found at 3.3 ± 1.3 cm. Conclusions: We demonstrate that extended internal neurolysis of second web space, along with the digital nerves, is technically and clinically feasible. This technique can be used to treat mixed median nerve injury in the hand and wrist.