Variance of the pectoralis major in relation to the inframammary fold and the pectoralis minor and its application to breast surgery

Understanding the anatomy of the muscles and other structures of the chest is of great importance in breast surgery. We have conducted the first analysis of the overall variations and relationships among the pectoralis major (PM), inframammary fold (IMF), and pectoralis minor (Pm). We studied 30 patients and 10 cadavers, leading to a total of 50 breasts. Preoperatively, the breast width was measured, and the costal origin of the lowest IMF point was marked. Intraoperatively, we recorded the costal origins of the PM and IMF, PM width, the distance between the PM and IMF, and the relationship and distance between the PM and Pm. Among the patients, PMs originated from the sixth rib in 80% and above the IMF in 66.67%. The mean distances between the PM and IMF were 10.5 mm in the patients and 16 mm in the cadavers. The mean PM/breast width ratio was 0.82 in the patients and 0.85 in the cadavers. The PM and Pm mostly crossed on the fourth or fifth rib, and the average angles between the two muscles were 23.5° and 21.4° in the patients and cadavers, respectively. This study is the first to analyze the anatomical variations of the PM, IMF, and Pm simultaneously. We also examined the differences between Western and Asian populations. Understanding the anatomy is undoubtedly crucial for breast surgery, and here we provide a firm guide to the variations to be expected during operations, which can lead to successful outcomes. Clin. Anat. 30:357–361, 2017. © 2017 Wiley Periodicals, Inc.