Transfer of flexor carpi ulnaris branch of the ulnar nerve to the pronator teres nerve: Histomorphometric analysis

Partial median-nerve injury high in the upper extremity, resulting from brachial plexus neuritis or trauma, can affect the pronator teres muscle and result in the inability to pronate the forearm. A nerve transfer from an ulnar nerve-innervated branch to the flexor carpi ulnaris (FCU) muscle to the branch to the pronator teres (PT) is an attractive option in this clinical scenario. This study, a histomorphometric analysis of nine cadaver specimens harvested at the proposed FCU branch to PT branch transfer site, demonstrates sufficient similarities between the two branches in total number of nerve fibers (371.6 with SEM 35.1, and 361.9 with SEM 47.1; p 0.87) and nerve cross-sectional area (122, 181 μm² with SEM 14,546 μ², and 142,492 μ² with SEM 19,633 μ²; p = 0.42), to predict a functional transfer result. In addition, clinical application of this transfer resulted in functional pronation strength of M4+.