The pectoralis minor inserts via a flat, strong tendinous attachment on the medial surface and superior margin of the coracoid process of the scapula. The tendon is approximately 2-3 cm long and lies deep to the pectoralis major, directly anterior to the brachial plexus and axillary vessels as they pass beneath the coracoid. The tendon's medial margin forms the lateral boundary of the retropectoral space.
The pectoralis minor tendon compresses the brachial plexus in hyperabducted arm positions (pectoralis minor syndrome or hyperabduction syndrome, a subtype of thoracic outlet syndrome), producing neurological and vascular symptoms in the arm during overhead activity. Pectoralis minor release or tenotomy at its coracoid insertion is performed for this syndrome. In breast reconstruction, the pectoralis minor tendon is divided to allow complete submuscular pocket development. The tendon is also a landmark in sentinel lymph node biopsy, where level I nodes are lateral to pectoralis minor and level II nodes lie behind it.
Compression of the brachial plexus and subclavian-axillary vessels by the pectoralis minor tendon against the coracoid process during hyperabduction produces positional neurological symptoms in the arm, diagnosed by reproduction with the hyperabduction test and managed with stretching, physiotherapy, or pectoralis minor tenotomy.
Rare avulsion of the pectoralis minor from the coracoid process in weightlifters or from sudden violent arm abduction produces anterior shoulder pain and a palpable defect below the coracoid, managed conservatively for most cases or with reattachment for high-demand patients.
