Ultrasound assessment of the distal pectoralis major: identification of two distinct tendons.

Purpose: Distal pectoralis major pathology is complex. Recent anatomical findings have identified the deltopectoral tendon, a structure distinct from the pectoralis major tendon, originating from the clavicular bundle and merging with the distal deltoid tendon. This study aims to characterize the deltopectoral tendon, assess its consistency, and define its relationship to the pectoralis major tendon to improve the understanding of distal pectoralis major pathology.

Methods: This study consisted of a prospective, monocentric, observational cohort design. Forty-six volunteer subjects with no history of trauma to the pectoralis major muscle underwent a systematic ultrasound examination of the muscle's connective skeleton. Complementing this prospective data, a retrospective review of five ultrasound scans documenting pectoralis major injuries was performed.

Results: The deltopectoral tendon was consistently identified on ultrasound. It was observed emerging between the deltoid and the clavicular bundle, adhering superficially to the terminal portion of the pectoralis major tendon, and merging with the anterior intramuscular tendon of the deltoid. The pectoralis major tendon, originating from the sternal and abdominal muscular portions and measuring 32 mm in length, 42 mm in width, and 2.1 mm in thickness, should be analysed independently of the clavicular bundle.

Conclusion: The distal insertion of the pectoralis major consists of two distinct tendons: the pectoralis major tendon and the deltopectoral tendon. The presence of an intact clavicular bundle, signifying the persistence of the deltopectoral tendon, may coexist with a complete rupture of the pectoralis major tendon and should not be mistaken for a partial, non-surgical injury.