A previously unclassified variant of sternalis muscle
We propose an addition to the Snosek et al. classification to include a subtype variant of sternalis muscle: mixed type and triple subtype.
Dissection of the anterior thorax of a 96-year-old female cadaver revealed bilateral sternalis muscles with an undocumented variant of the right sternalis muscle.
The left sternalis muscle presented as a simple type—left single using the Snosek et al. classification scheme. The right sternalis muscle revealed a previously undocumented classification type. It consisted of three bellies and two heads, with the lateral head formed by two converging bellies and the medial head formed from the superficial medial belly.
The unique presentation of right sternalis muscle can be classified by expanding the Snosek et al. classification scheme to include triple-bellied subtypes. This presentation is classified as a mixed type—right triple, with single bicipital converging and single bicipital diverging. Documentation of sternalis muscle variations can prevent misdiagnoses within the anterior thorax.
KeywordsSternalis muscle Anterior thorax Variation Classification
The authors thank Catherine Stanley, Medical Illustrator in the Department of Surgery, Division of Anatomical Sciences, University of Michigan Medical School, Ann Arbor, USA, for her computer-generated image used in this publication. The anatomical donors of the University of Michigan Anatomical Donations Program make our research possible, and the authors additionally thank them for their selfless donation to furthering anatomic study.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.