ANATOMICAL CHARACTERISTICS OF THE MEDIAN NERVE BRANCH INNVERVATING THE FLEXOR CARPI RADIALIS AND THE POSTERIOR INTEROSSEOUS NERVE: APPLICATION IN NERVE TRANSFER SURGERY

Abstract

Objectives: Surgical transfer of the nerve branch innervating the flexor carpi radialis muscle to the posterior interosseous nerve is a new technique that facilitates restoration of finger extension in early-stage high radial nerve injuries. To perform this procedure effectively, a thorough understanding of the anatomy, the number of fascicles and axonal counts of both nerve branches, is essential. Therefore, we decided to investigate the applied anatomical characteristics of these two nerves.

Methods: A case-series study was conducted on 30 fresh cadaveric elbow–forearm specimen.

Results: The branch of the median nerve innervating the flexor carpi radialis muscle originates at a point 3.61 cm distal to the interepicondylar line. It typically gives rise to one to two independent branches and enters the muscle at the proximal one-third of its lateral surface. The posterior interosseous nerve is located at distances of 4.26 cm from the interepicondylar line, 4.99 cm from the lateral epicondyle, and 2.95 cm from the bifurcation of the radial nerve. These anatomical characteristics help facilitate end-to-end neurorrhaphy between the two nerves with minimal tension at the anastomotic site, without the need to transect the supinator muscle to mobilize the posterior interosseous nerve medially. The number of fascicles ranges from 2 to 8, and the ratio of axonal density between the donor nerve and the recipient nerve is 1:4.89.

Conclusions: This anatomical study of the median nerve branch innervating the flexor carpi radialis and the posterior interosseous nerve provides valuable insights for clinicians on morphology, fascicular composition, and axonal characteristics. These findings support the feasibility of transferring the median nerve branch to the flexor carpi radialis to the posterior interosseous nerve as a surgical option for restoring finger extension in high radial nerve injuries.

Keywords: posterior interosseous nerve; fascicles; axons; high radial nerve injury