Pectoralis major transfer for subscapular deficiency: anatomical study of the relationship between the transferred muscle and the musculocutaneous nerve.

PURPOSE: Pectoralis major transfer is indicated for irreparable subscapularis tendon tears. One surgical option is transferring the sternal part of the pectoralis major to the humeral insertion of the subscapularis under the conjoined tendon of the coracobrachialis and biceps muscles. The purpose of this study is to define the anatomical relationship between the transferred tendon and the musculocutaneous nerve.

METHODS: In 52 cadaveric fresh-frozen shoulders, the relevant structures were dissected and a pectoralis major transfer was performed. The relationship between the transferred tendon, the musculocutaneous nerve branches distally and the coracoid process proximally was examined. Measurements were taken at the conjoined tendon level.

RESULTS: The distance between the coracoid process and the most proximal musculocutaneous nerve branch was 54.2 ± 33.2 mm. In 25 cases (48%), the transferred tendon passed freely between both structures. In 16 cases (31%), there was contact distally with the musculocutaneous nerve. In 11 cases (21%), there was contact both proximally with the coracoid process and distally with the musculocutaneous nerve, making a safe transfer impossible.

CONCLUSIONS: When performing a pectoralis major transfer, it is essential to identify the musculocutaneous nerve and its branches. In some cases, a subcoracobicipital transfer may not be feasible and a more superficial transfer should be considered.