A total of 192 embalmed cadavers were examined in order to present a detailed study of arterial variations in the upper limb and a meta-analysis of them. The variable terminology previously used was unified into a homogenous and complete classification, with 12 categories covering all the previously reported variant patterns of the arm and forearm.

Variations in connections between the musculocutaneous and median nerves in the arm are not as uncommon as was once thought. This opinion led us to perform a study in 138 cadavers (66 male, 72 female). These variations were seen in 64 cadavers (46.4%), 9 bilaterally and 55 unilaterally (26 right and 29 left); in total, therefore, variations were observed in 73 out of 276 arms (26.4%), 42 male and 31 female. No statistically significant differences by gender and side were observed. We classify the variations in three main patterns: Pattern 1, fusion of both nerves (14 arms, 19.2%); Pattern 2, presence of one supplementary branch between both nerves (53 arms, 72.6%); and Pattern 3, two branches (5 arms, 6.8%). Pattern 2 was further subdivided into a sub-group 2a when a single root from the musculocutaneous nerve contributed to the connection (51 arms, 69.9%), and 2b when there were two roots from the musculocutaneous nerve (2 arms, 2.7%). A combination of Patterns 1 and 2a was observed in one case (1.4%). Further variations are described, published classification systems are reviewed and a meta-analysis of previous results is presented. An overall incidence of 33% of variant arms was observed. Of these variant arms, Pattern 1 represented 13.1%, Pattern 2 represented 75.4%, and Pattern 3, 8.5%, similar to our figures.

Supernumerary humeral heads of the biceps brachii muscle were found in 27 (15.4%) of 175 cadavers. They were bilateral in five cadavers and unilateral in 22 (8 left, 14 right), giving a total of 32 examples in 350 arms (9.1%). Depending on their origin and location, the supernumerary heads were classified as superior, infero-medial, and infero-lateral humeral heads. Previous studies were reviewed using this classification. The infero-medial humeral head was observed in 31 of 350 (9%) arms and was therefore the most common variation. The superior humeral head was observed in five (1.5%). The infero-lateral humeral head was the least common variation, observed only in one (0.3%) of 350 arms. A biceps brachii with three heads was observed in 27 of 350 (7.7%) arms and with four heads in five (1.4%) arms.

Variations in the origin of STA and SLA from the carotid arterial tree and the similarity of their diameters mean that there is a significant possibility of their misidentified during surgery.

This study confirms that the median artery may persist in adult life in 2 different patterns, palmar and antebrachial, based on their vascular territory. The palmar type, which represents the embryonic pattern, is large, long and reaches the palm. The antebrachial type,which represents a partial regression of the embryonic artery is slender, short, and terminates before reaching the wrist. These 2 arterial patterns appear with a different incidence. The palmar pattern was studied in the whole sample (120 cadavers) and had an incidence of 20 %, being more frequent in females than in males (1.3 : 1), occurring unilaterally more often than bilaterally (4 : 1) and slightly more frequently on the right than on the left (1.1 : 1). The antebrachial pattern was studied in only 79 cadavers and had an incidence of 76 %, being more frequent in females than in males (1.6 : 1) ; it was commoner unilaterally than bilaterally (1.5 : 1) and was again slightly more prevalent on the right than on the left (1.2 : 1). The origin of the median artery was variable in both patterns. The palmar type most frequently arose from the caudal angle between the ulnar artery and its common interosseous trunk (59 %). The antebrachial pattern most frequently originated from the anterior interosseous artery (55 %). Other origins, for both patterns, were from the ulnar artery or from the common interosseous trunk. The median artery in the antebrachial pattern terminated in the upper third (74 %) or in the distal third of the forearm (26 %). However, the palmar pattern ended as the 1st, 2nd or 1st and 2nd common digital arteries (65 %) or joined the superficial palmar arch (35 %). The median artery passed either anterior (67 %) or posterior (25 %) to the anterior interosseous nerve. It pierced the median nerve in the upper third of the forearm in 41 % of cases with the palmar pattern and in none of the antebrachial cases. In 1 case the artery pierced both the anterior interosseous and median nerves.