Iatrogenic Symmastia: Causes and Suggested Repair Technique

Various theories exist to explain the etiology of iatrogenic symmastia. Subglandular over-dissection of the medial breast pocket over the sternum, disruption of midline sternal fascia, oversized implant base diameter, and over-dissection of the medial pectoralis muscle attachments to the sternum are popular explanations.The authors hypothesized that the most common risk factor for iatrogenic symmastia is subpectoral breast augmentation.A retrospective chart review was conducted including all symmastia patients who underwent surgery from January 2008 to April 2018 by a single surgeon (C.L.M.). ASAPS members were also surveyed regarding the etiology and incidence of symmastia in their practice.Twenty-three patients with symmastia were included in the retrospective chart review. All had previous subpectoral breast augmentation. In the ASAPS survey, 91 plastic surgeons reported seeing an average of 2.2 consults for acquired symmastia over the preceding year; 1.9 of the 2.2 (84.9%) acquired symmastia consults previously underwent subpectoral breast augmentation. Most surgeons attributed these patients' symmastia to over-dissection of the medial pectoralis muscle attachments to the sternum.Symmastia is most often caused by pectoralis major sternal dehiscence during subpectoral breast augmentation. In the senior author's experience, all patients with iatrogenic symmastia previously had a submuscular breast augmentation. The ASAPS survey supports multiple causes for symmastia with retromuscular breast augmentation occurring in the majority of patients. Repair of symmastia should include securing Scarpa's fascia to the sternum, reattaching the pectoralis major to the sternum, avoiding another subpectoral implant, and using postoperative modalities to protect the repair.