Prevalence of the sternalis muscle in a sample of routinely dissected human cadavers

Sternalis muscle is an uncommon muscle head attaching between the sternoclavicular joint superiorly and the costal cartilage near the xiphoid process.

In this study, 36 cadavers (18 male, 18 female) were obtained through the Anatomical Board of the State of Florida and complete, routine musculoskeletal dissection was performed while adhering to all relevant laws and practices.

Two examples of the sternalis muscle belly (5%) were identified, one in a black male and one a white female. The sternalis muscles were bilateral in both cases and each was formed of a single muscle belly. The superior attachments were continuous with the sternal attachment of sternocleidomastoid, and the inferior attachments connected to the costal cartilages. Sternalis did not cross the midline and the T2-T5 anterior intercostal neurovasculature associated closely with the muscle belly. In the female, a well-formed unilateral chondrocoracoideus muscle was apparent with a branch from the medial pectoral nerve closely associated on the deep surface. No other abnormalities in the chest, axilla, or brachial plexus were noted on either cadaver, and the pectoralis major and minor muscles were normally formed and innervated in both cases.

This study supports other evidence in the literature that indicates the sternalis muscle has an average prevalence in the population of approximately 5%, and it appears across race and sex. Education about this structure is important for radiologists, surgeons, and doctors of physical therapy that may be involved in treatment and post-surgical rehabilitation of this region.