Langer's axillary arch (musculotendinous arch of the axilla) is an anomalous muscle band crossing the axilla from the latissimus dorsi to the pectoralis minor, coracoid, or coracobrachialis, present in 6-8% of individuals. It passes anterior to the neurovascular bundle of the axilla, potentially compressing the brachial plexus, axillary artery, or musculocutaneous nerve.
| Origin | Latissimus dorsi muscle belly or its tendon, in the posterior axilla |
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| Insertion | Pectoralis minor tendon, coracoid process, or coracobrachialis; crosses the axilla anteriorly |
| Nerve Supply | Thoracodorsal nerve (C6-C8) or medial pectoral nerve |
| Blood Supply | Subscapular artery or lateral thoracic artery branches |
| Actions | Adduction and internal rotation of the shoulder (consistent with its latissimus dorsi derivation); may compress neurovascular structures crossing the axilla |
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Langer's arch is the most clinically significant axillary muscle variant because it can cause thoracic outlet-like compression of the brachial plexus or axillary vessels. It is identified during axillary lymph node dissection for breast cancer as an anomalous band that must be divided for complete level I-II dissection and to prevent ongoing neurovascular compression. The musculocutaneous nerve entering the coracobrachialis may be compressed by the arch. Preoperative awareness reduces operative surprise and inadvertent neurovascular injury.
An anomalous Langer's arch crossing the axilla compresses the brachial plexus or axillary vein, producing upper extremity neurovascular symptoms mimicking thoracic outlet syndrome; surgical division of the arch through an axillary approach decompresses the neurovascular bundle and resolves symptoms.
