Complete coverage of a tissue expander by a musculofascial pocket including the sternalis muscle during breast reconstruction.

The sternalis muscle is a vestigial muscle that is vertically long with a rectangular shape, courses parallel or oblique to the long axis of the medial sternocostal part of the pectoralis major, and presents in rare cases (1.3%) [1,2]. It often has a major effect on the insertion of a tissue expander during breast reconstruction; however, there has only been a single report of the sternalis muscle and the pectoralis major muscle being elevated as a lower mastectomy flap, and no reports have been published about repairing intraoperative trauma [3].

A 66-year-old woman underwent immediate breast reconstruction using a tissue expander after total mastectomy. She had a left-sided sternalis muscle that was 3.5 cm wide and 12.0 cm long (Figs. 1, 2). In a musculofascial pocket that included the muscle, a loose adipose connection between the sternalis muscle and the pectoral major muscle collapsed due to the textured surface of the tissue expander to form a caudal lesion that was 5.0 cm long. However, this was successfully repaired using an untied suture technique (Fig. 3).

Fig. 1.

Imaging analysis of the sternalis muscle. (A) Image obtained 6.0 cm distal from the origin in T1-weighted magnetic resonance imaging. (B) Image obtained 9.0 cm distal from the origin in T1-weighted magnetic resonance imaging. (C) Image obtained 8.0 cm distal from the origin in computed tomography. The blue arrow indicates the sternalis muscle.

Fig. 2.

Schematic depiction of the sternalis muscle. The sternalis muscle was 3.5 cm wide and 12.0 cm long, coursed adjacent to the sternum and longitudinally for 8.5 cm of its length, and then coursed slightly obliquely, running lateral to the fascia of the rectus abdominalis muscle. It connected to the medial portion of the pectoralis major muscle via loose adipose connective tissue. SM, sternalis muscle; PM, pectoralis major muscle; FRM, fascia of rectus abdominalis muscle.

Fig. 3.

(A) Repair of the loose adipose connection. The textured surface of the tissue expander filled with saline caused the collapse of the loose adipose connection between the sternalis muscle and pectoralis major muscle, resulting in a caudal lesion that was 5.0 cm long. The tissue expander was subsequently removed and 6 untied sutures were inserted in these muscles. The SV-14 tissue expander (volume, 500 mL; height, 12 cm; width, 14 cm; projection, 7.1 cm) was made by Allergan Inc. (Santa Barbara, CA, USA). (B) Insertion of the tissue expander in the musculofascial pocket. Untied sutures were ligated carefully and both the pectoralis major muscle and the fascia of the serratus anterior muscle were sutured. The tissue expander was subsequently inserted into the musculofascial pocket. The blue arrows indicates the ligated untied sutures. SM, sternalis muscle; PM, pectoralis major muscle; FRM, fascia of rectus abdominalis muscle; TE, tissue expander.

Many plastic surgeons may be unfamiliar with the sternalis muscle; however, they should investigate whether it is present preoperatively via imaging. The merits of the untied suture technique include the certain and safe suturing of both the sternalis muscle, which is often thin, and the pectoralis major muscle without damaging the tissue expander, preventing the recurrence of collapse in this area of connective tissue when inserting it after the ligation of sutures during repair. This technique may be improved by combining it with horizontal mattress sutures.