Rodriguez-Niedenfuhr et al., have recently proposed a system of classification of upper limb arterial variations, based on their extensive experience of almost 400 upper limb dissections, and based on a thorough literature review on the subject [3, 8, 9]. This terminology, which recently has been taken up by several authors , considers each arterial variation as an individual entity along its full extension in the upper limb . Furthermore, this classification divides upper limb arterial variants in three broad groups based on their location in the arm, the arm and forearm, or the forearm. These three groups are further subdivided in several different categories, depending on the absence or duplication of arteries, and on whether these variants adopt a superficial or usual course in the forearm .
The variations found exclusively in the forearm are the superficial brachial artery and the accessory brachial artery. The former represents a brachial artery coursing in front of the median nerve, instead of being placed behind it. The accessory brachial artery is characterized by the existence of 2 brachial arteries that rejoin before giving off the forearm arteries. The accessory brachial artery originates from the main brachial artery .
The variations located at the level of both the arm and forearm are the superficial brachioulnar (SuBUA), the brachioulnar, the brachioradial, the superficial brachioradial, the brachiointerosseous, the superficial brachiomedian, and the superficial brachioulnoradial arteries .
The SuBUA is characterized by an ulnar artery that originates higher than usual and that courses over the forearm flexor muscles. In this setting, there is a whole arterial pattern, with a brachial or superficial brachial artery branching into the radial and common interosseous arterial trunk, or more rarely into the radial and ulnar arteries .
The brachioulnar artery corresponds to a high origin of the ulnar artery from the brachial artery, with the latter branching into the radial artery and the common interosseous arterial trunk .
The brachioradial artery represents a high origin of the radial artery from the brachial or superficial brachial artery that in turn branches into the ulnar artery and the common interosseous arterial trunk .
The superficial brachioradial artery consists of a high origin of the radial artery coursing over the brachioradialis muscle or the tendons that limit the snuffbox. In these circumstances the brachial artery usually originates the ulnar artery and the common interosseous arterial trunk .
The brachiointerosseous artery is defined by a high origin of the interosseous arterial trunk, in the context of a whole arterial pattern of the upper limb, with a brachial artery that divides into the radial and ulnar arteries .
The superficial brachiomedian artery is characterized by a high origin of the median artery that courses above the superficial flexor muscles and by a brachial artery that divides into the radial and ulnar arteries .
Finally, the superficial brachioulnoradial artery represents a superficial brachial artery that at the level of the elbow branches into the radial and ulnar arteries, which in turn will course over the superficial forearm flexor muscles. In this variant, the superficial brachial artery coexists with a normal brachial artery that ends in the common interosseous arterial trunk .
The variations found exclusively at the forearm level include the superficial radial artery, the duplication of the radial arteries, and the absence of the radial or ulnar arteries .
The superficial radial artery consists of a radial artery coursing above the tendons limiting the snuffbox. The absence of either the radial or ulnar arteries is considered very rare, as is the true duplication of the radial artery .
Therefore, considering Rodriguez-Niedenfuhr’s classification, our case most closely resembles a SuBUA variant . This variant corresponds to a brachial artery originating a superficial ulnar artery high up in the arm, whereas the radial artery is a continuation of the brachial artery . The origin of the interosseous arteries from the radial artery, as recorded in the present case, is considered common in cases of ulnar arteries arising in the arm .
According to most authors, the SuBUA most frequently courses posteriorly to the bicipital aponeurosis, and not anteriorly as it was observed in our dissection (Figures 1C and 2A) . In addition, in the work conducted by Rodriguez-Niedenfuhr et al., in all cases the SuBUA coursed anteriorly to all the flexor muscles of the forearm, and then placed itself in the lateral border of the flexor carpi ulnaris to adopt its position in the lateral aspect of the ulnar nerve at the level of the middle third of the forearm . As far as the authors could determine, a SuBUA variant similar to the one we observed, with a path deep to the palmaris longus muscle, has just been reported twice in the literature. Quain found it in 2 cases while dissecting 429 upper limbs , and Hazlet once in 188 limbs .
Upper limb vascular variations are presently thought to result from a stochastic process of persistence, enlargement and differentiation of parts of the initial capillary network which would normally remain as capillaries or even regress [5, 11]. The precise mechanisms that lead to the higher frequency of certain variants over others, remain to be elucidated [5, 11]. Interestingly, Rodriguez-Niedenfuhr et al., identified a SuBUA in 4,7% of 150 upper limbs of embryos, which is a value superior to that reported by most authors in the general adult population .
The clinical importance of the superficial variations of the arteries of the upper limb are increasingly being recognized . For example, by being superficial, they can be easily mistaken for subcutaneous veins, leading to inadvertent artery cannulation, with the potential risk of distal limb ischemia [1, 12, 13]. In addition, the superficial position of the radial or ulnar arteries makes them more vulnerable to trauma . Moreover, the possibility of a SBUR variant should always be born in mind when using the arm or forearm as a source or as a recipient of microvascular flaps, or when using the radial artery as vascular graft [14–16].
Clinically, the presence of superficial forearm arteries can be suspected in the absence of palpable ulnar or radial pulses in their usual location, when superficial pulsatile vessels are found, or when patients complain of intermittent forearm or hand pain .