Anatomic evaluation of the subcoracoid pectoralis major transfer in human cadavers

Subcoracoid transfer of the pectoralis major has recently been described as a reconstruction for subscapularis insufficiency. The purpose of this study was to examine the surgically relevant anatomy of this transfer. The importance of understanding this anatomy was recently highlighted to us following our encounter with musculocutaneous neuropraxia in 2 patients after transfer of the entire pectoralis major, one deep to the musculocutaneous nerve. Dissections were performed on 20 fresh, whole human cadavers in which the entire pectoralis major muscle, medial and lateral pectoral nerves, and musculocutaneous nerve were explored and quantified. The relationship between the pectoralis major and the conjoined tendon was studied in situ and after simulated transfers. The medial and lateral pectoral nerves were located far medial to the pectoralis major tendon insertion and appeared to be safe from injury as long as surgical dissection remained lateral to the pectoris minor and less than 8.5 cm from the humeral insertion. Transfer of the pectoralis major superficial to the musculocutaneous nerve created less tension than transfer deep to the musculocutaneous nerve. Because proximal innervation of the coracobrachialis and short head of the biceps is not an uncommon occurrence, a split pectoralis major transfer, release of the proximal musculocutaneous branches, or debulking of the pectoralis major muscle belly may be required in some instances to prevent tension on the nerve. Because of the variability and location of the musculocutaneous nerve, it should always be visualized operatively. Transfer of the pectoralis major tendon lateral to the biceps tendon appeared to best restore the muscle length-tension relationship.