Bilateral double axillary artery: embryological basis and clinical implications.

An unusual bilateral variation in the arterial pattern of the axilla was observed in an embalmed cadaver. Each axilla contained two axillary arteries of similar origins but different patterns of branching and fate. The first part of each axillary artery was a single vessel as is the norm. It gave off a supreme thoracic artery and then bifurcated into two medium-sized arteries hence referred to as regular and variant. The variant artery ran in an antero-medial course, partly covered by the one axillary vein. The regular artery gave off the thoracoacromial and two posterior branches from its second part, the anterior and posterior humeral circumflex arteries from its third part, and then continued as the brachial artery with all the usual branches except the profunda brachii on the right side. The variant gave off five arteries from the second part, a thoracoacromial artery, two separate long thoracic arteries each with a branch that ran along the intercostobrachial nerve to the arm, and two posterior branches. In the third part of the variant, the subscapular artery arose with its usual branches plus a common origin for two additional humeral circumflex arteries. The variant terminated as the profunda brachii artery to the right side while on the left side it terminated in muscular branches to the triceps. Hence, the arterial blood supply to the upper limb, and the axillary region in particular, was shared on both sides by two major arteries instead of one. These two arteries emanated from the first part of the axillary artery and may represent persisting branches of the capillary plexus of the developing limb buds. The findings have an embryological basis and clinical relevance considering the frequency of procedures in this region.