THE MUSCULOCUTANEOUS NERVE AND ITS BRANCHES TO THE BICEPS AND BRACHIALIS MUSCLES

The musculocutaneous nerve and its motor branches to the biceps and br achialis were dissected and studied under the operating microscope in 24 fresh-frozen cadaveric specimens. The motor branch to the biceps ex its from the musculocutaneous nerve at 179 mm distal to the coracoid p rocess. Anatomic variations were seen in the innervation of the two he ads of the biceps. A common primary motor branch that bifurcates to su pply the two heads was seen in 20 specimens (type I). Two specimens we re observed to have two separate primary branches originating from the main musculocutaneous nerve trunk to individually supply each head of the biceps (type II). The third variation, two specimens (type III), was observed in two specimens to be similar to type I, but with an add itional distal motor branch innervating the common belly of the biceps muscle. The motor branch to the brachialis muscle exits from the musc ulocutaneous nerve 170 mm distal to the coracoid process. A single pri mary motor branch (type I) was seen in 23 specimens, and 1 specimen (t ype II) showed two separate primary motor branches innervating the mus cle. The motor branches to the biceps and brachialis muscles may be di ssected proximally from their points of exit from the main trunk of th e musculocutaneous nerve for a mean distance of 44 mm and 53 mm, respe ctively. This information can be used by surgeons who elect to suture intercostal nerves to the motor branches of the biceps and brachialis muscles for elbow flexion in brachial plexus injuries.