The anatomy of the pectoral nerves and their significance in brachial plexus reconstruction

Twenty-nine brachial plexuses from 13 embalmed and 5 fresh cadavers were ex amined under x3.5 loupe magnification to collect systematic and topographic anatomical data regarding the lateral and medial pectoral nerves. Addition ally, nerve biopsy specimens were harvested in 5 fresh cadavers to obtain h istomorphometric data. In all dissections the pectoral nerves Exited at the trunk level as 3 distinct nerves. The superior pectoral nerve (from the an terior division of the superior trunk) commences just distal to the suprasc apular nerve and courses laterally to innervate the lateral clavicular port ion of the pectoralis major muscle (PM) with 2 to 4 branches. The middle pe ctoral nerve (from the anterior division of the middle trunk) courses dista lly and enters the infraclavicular fossa with 2 constant branches. The supe rficial branch terminates in the medial clavicular and upper sternal parts of the PM. The deep branch always forms a plexus with the medial pectoral o r inferior pectoral nerve (from the anterior division of the inferior trunk ), which courses at a right angle around the the lateral thoracic artery. F rom this plexus several branches terminate in the Pm. The branch to the low er aspect of the PM pierces the pectoralis minor muscle in two thirds of ca ses, whereas it passes its inferior border to reach the lower aspects of th e PM with an average length of 15 cm in one third of cases. Knowledge of th e detailed anatomy of the pectoral nerves, as outlined in this study, clari fies the obscure anatomic relationship of the lateral and medial pectoral n erves and allows easy intraoperative location of the medial pectoral nerve at the exit of the lateral thoracic artery. The length of the inferior pect oral nerve, the number of motor axons, and the anatomical proximity of this nerve make it an expendable but powerful source of reinnervation to the mu sculocutanous nerve in upper brachial plexus injuries. (J Hand Surg 2000;25 A:942-947. Copyright (C) 2000 by the American Society for Surgery of the Ha nd.).