Axilla; a rare variation: axillary arch muscle.

Axillary arch muscle or the Langer’s muscle is one of the rare muscular variation in the axillary region. It is the additional muscle slip extending from latissimus dorsi in the posterior fold of axilla to the pectoralis major or other neighbouring muscles and bones. In the present article a case of 68 yrs old female cadaver with axillary arch in the left axillary region is reported. It originated from the anterior border of lattissimus dorsi and merged with the short head of biceps and pectoralis major muscles. The arch was compressing the axillary vein as well as the branches of the cords of brachial plexus. The presence of the muscle has important clinical implications, as the position, unilateral presence, axillary vein entrapment, multiple insertions makes the case most complicated. Recognising the presence of axillary arch muscle in such complex form is important in clinical practice as the arch causes the difficulties in staging lymph nodes, axillary surgery, thoracic outlet syndrome, shoulder instability or cosmetic problems. The anatomy, embryological and clinical importance of this muscular variation is discussed in this paper.

Bilateral presence of axillary arch muscle passing through the posterior cord of the brachial plexus / Presencia bilateral del arco muscular axilar pasando por el fascículo posterior del plexo braquial

The axillary arch can be described as an anomalous muscular slip of latissimus dorsi muscle. In this paper, a rare case of bilateral axillary arch is reported during routine dissection of the axillary region of a 57-year old male cadaver. On both sides, the axillary arch muscle took origin from latissimus dorsi and teres major, and passed upwards through the posterior cord of the brachial plexus, but posterior to the bulk of axillary neurovascular bundle. It then split into two slips: the medial slip was inserted into the root of the coracoid process, while the lateral slip which was intracapsular, was attached to the lesser tubercle, above the attachment of subscapularis. The presence of the muscle has important clinical implications, and the position, bilateral presence, penetration of the posterior cord, and multiple connective tissue attachments makes the case most unique. The anatomy, surgical implications, and embryology of the anomalous muscle are discussed in this paper.

El arco axilar puede ser descrito como un fascículo muscular anómalo del músculo latísimo del dorso. En este trabajo, un raro caso de arco axilar bilateral se encontró durante la disección de rutina de la región axilar de un cadáver de 57 años de sexo masculino. En ambos lados, el músculo arco axilar se originó desde los músculos latísimo del dorso y redondo mayor y pasó hacia arriba a través del fascículo posterior del plexo braquial, pero posterior a la mayor parte del paquete neurovascular axilar. A continuación, se dividió en fascículos: el fascículo medial se insertó en la raíz del proceso coracoides, mientras que el fascículo lateral, era intracapsular y se insertaba en el tubérculo menor del húmero, por encima de la inserción del músculo subescapular. La presencia de este músculo axilar tiene importantes implicaciones clínicas, y la posición, la presencia bilateral, la penetración del fascículo posterior, y múltiples uniones de tejido conectivo hacen al caso más especial. La anatomía, las implicaciones quirúrgicas y embriología del músculo anómalo son discutidos en este trabajo.