An anatomic study of the musculocutaneous nerve and its relationship to the coracoid process.

The anatomy of the musculocutaneous nerve was investigated to determine its relationship to the coracoid process. The distance from the coracoid to the point of entrance of the main nerve trunk into the coracobrachialis muscle ranged from 31 to 82 mm, with a mean of 56 mm. Small nerve twigs to the coracobrachialis (proximal to the main nerve trunk) entered the muscle as close as 17 mm below the coracoid, with an average of 31 mm. The frequently cited range of 5-8 cm below the coracoid for the level of penetration cannot be relied on to describe a safe zone because 29% of the nerves entered the muscle proximal to 5 cm below the coracoid (74% if the proximal twigs are counted). If coracoid mobilization is necessary, the musculocutaneous nerve and its twigs should be identified and protected, keeping in mind the variations in anatomy and the level of penetration.