Important variations of the axillary arch muscle that every clinician should know

Abstract

The axillary arch (AA) has been recognized as the most common variant muscle of the axilla since the early 1800s. It has been called various names by different authors such as: “axillopectoral muscle,” “axillodorsal muscle,” “achselbogen muskell,” “arcus axillaris,” and the “pectodorsal muscle;” but it is widely and most commonly known as “Langer's axillary arch”. It presents in varied morphological variants both in unilateral and bilateral fashion and has no apparent physiological function. Much disagreement still exists about its nerve supply and embryological origin. With the advent of medical imaging and upper limb surgery the clinical importance of this muscle has been re emphasized. The aim of this study was to conduct a meta‐analysis on AA muscle with special emphasis on its anatomy, embryology, clinical implications and potential iatrogenic complications. The embryological origin of the AA is most likely to be a remnant of the Panniculus carnosus— highly developed pectoral muscle group in some lower animals, but in humans has regressed throughout evolution. Incidence of the AA ranges from 3.0% to 19.0% in cadaveric studies, and 0.25% to 37.5% in clinical observations. Knowledge of this important muscular anomaly and familiarity with the AA in the clinical setting, especially in surgical procedures of the axilla (i.e. axillary lymphadenectomy and sentinel node biopsy), or in any procedure requiring dissection of the axilla where the neurovascular structures could be compromised, is important for establishing differential diagnoses of other pathologies in the axilla, as well as crucial for proper lymph node staging.