The conjoined sternalis-pectoralis muscle flap in immediate tissue expander reconstruction after mastectomy

The sternalis muscle is an accessory muscle of the anterior chest wall. This is a rare anatomic variant reported in approximately 8% of the population, with variation among races. While several anatomic studies of the sternalis muscle exist, nothing in the literature addresses the implications of this muscle on reconstruction of the breast after mastectomy. Based on several encounters of this muscle variant by the senior author over a 15-year period, we offer a strategy and rationale for dealing with this rare, but known, anatomic variant during immediate tissue expander reconstruction of the breast after mastectomy. First is the importance of recognizing the presence of a sternalis muscle, which may present in a variety of configurations. We offer our technique of conjoined sternalis-pectoralis muscle flap during tissue expander reconstruction of the breast. This allows for the creation of a larger, more properly placed submuscular pocket with adequate muscle coverage of the tissue expander. Our experience illustrates that the reconstructive surgeon must be familiar with the sternalis muscle and be prepared to adapt his or her technique for tissue expander placement when faced with this accessory muscle.