Background: The inframammary fold (IMF) is an important anatomic landmark in breast surgery. Despite the importance of this structure, its relationship to the pectoral muscle and its position on the chest wall are not fully understood. Objective: The purpose of this article is to identify the positional relationship of the inframammary crease to the pectoralis major muscle. Methods: The study included 20 female cadavers and 10 patients with breast cancer with planned mastectomies. The course of the inframammary crease was tattooed to the underlying chest wall with marking needles and methylene blue dye. Marking needles were placed along the fold at the midclavicular line, 2 cm medial to the midclavicular line and 2 cm lateral to the midclavicular line. After removal of overlying soft tissue, measurements were made between the IMF markings and the inferior origin of the pectoralis major muscle. Chest walls of the cadavers were examined bilaterally. Results: The IMF was located inferior to the inferior origin of the pectoralis major muscle in all measurements of all specimens. The average distance of the IMF below the pectoralis major origin in the cadaveric group at the medial, midclavicular, and lateral locations was 1.9, 2.0, and 2.5 cm, respectively. The average distance of the IMF below the pectoralis major origin in the mastectomy patient group at the medial, midclavicular, and lateral locations was 1.5, 1.6, and 2.2 cm, respectively. Conclusions: The IMF is inferior to the inferior origin of the pectoralis major muscle. Subpectoral dissection to the level of the IMF will disrupt the attachments of the pectoralis major muscle.
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