Bilateral brachio-antebrachial arterial variations with ontogenic explanation
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0975-2870.182516
During dissection in the Department of Anatomy, a female cadaver was encountered with arterial variations bilaterally. From third part of axillary artery, a branch was observed running superficial to median nerve, which was called as superficial brachial artery. The axillary artery after passing through the two roots of median nerve continued as normal (deep) brachial artery. The course of superficial and deep brachial arteries was different on both sides. Common interosseous artery was observed as a branch of radial artery bilaterally. Also, ulnar artery was seen entering the hand passing deep to flexor retinaculum bilaterally, which may get affected in carpal tunnel syndrome. It is important for the clinicians to have knowledge of such variations. An attempt has also been made to explain the variations ontogenically. Keywords: Antebrachial artery, brachial artery, ontogeny, radial and ulnar arteries, superficial brachial artery
Variations in the arterial pattern of the superior extremity have been frequently found either during anatomical dissection, surgery or angiography. Many authors have described the variations along with mention of high origin of radial or ulnar arteries. [1],[2],[3],[4] In the present case, in an adult female cadaver, superficial brachial artery with other arterial variations was observed bilaterally. The present work is an attempt to document the variations systematically and also try and explain them on the basis of Rodríguez-Baeza et al. modification [5] of Singer's developmental staging for arteries of upper limb. [6] Such knowledge is important for the clinicians to know about the arterial variations to avoid complications.
Meticulous dissection of both the superior extremities in the same cadaver has been performed in an adult female cadaver preserved in formalin-glycerin. Variations were documented and photographed. The same has been analyzed ontogenetically. The arterial variations observed were different on the right and left sides. Right superior extremity Two centimeters proximal to the lower border of teres major muscle, an artery was seen arising from the third part of axillary artery, labelled as superficial brachial artery, as it was running superficial to median nerve [Figure 1]a. Thus, third part of axillary artery had four branches. After passing through two roots of median nerve, the main artery continued as deep brachial artery, at the level of lower border of teres major muscle, which is the normal brachial artery. After giving the branches as arteria profunda brachii, nutrient artery to humerus and muscular branches, the artery finally narrowed and ended at elbow. Superior ulnar collateral artery was seen arising from superficial brachial artery. Inferior ulnar collateral artery was absent. Afterward, the artery crossed the median nerve superficially from medial to lateral side. In the antebrachial region at the level of medial epicondyle of humerus, the superficial brachial artery divided into radial and ulnar branches. The artery was superficially placed in the arm.
In the forearm, the course of radial artery was normal [Figure 1]b. In addition to its normal branches, it was seen giving a branch as common interosseous artery (this is normally a branch of ulnar artery), which divided into posterior and anterior interosseous branches. The ulnar artery in the forearm had a course superficial to all the flexors of forearm. In the distal 1/3 rd of its course [Figure 2], it was placed lateral to the tendon of flexor carpi ulnaris. It entered the hand by passing deep to flexor retinaculum. In the hand, it formed the superficial palmar arch which was incomplete. The artery ended by dividing into princeps pollicis and radialis indicis branches (these are normally the branches of radial artery).
Left superior extremity Just before passing through the two roots of median nerve, the third part of axillary artery gave a branch as superficial brachial artery [Figure 3]a. Thus, third part of axillary artery had four branches. The axillary artery after passing through two roots of median nerve continued lateral to median nerve as deep brachial artery at the level of lower border of teres major muscle. The superficial brachial artery was related medial to the median nerve and had a superficial course in the arm. This relation was maintained in the arm and continued in the forearm [Figure 3]a]. Deep brachial artery continued as radial artery, which had a normal course in the forearm. In addition to its normal branches, the radial artery gave a branch as common interosseous artery [Figure 4]a. The superficial brachial artery continued as ulnar artery and had a course superficial to all the flexors of the forearm in its upper 2/3 rd . In the lower 1/3 rd of its course in the forearm [Figure 4]b], the artery passed deep to the tendon of flexor carpi ulnaris from its lateral to medial side and entered the hand by passing deep to flexor retinaculum. In the hand, it formed an incomplete superficial palmar arch similar to the right side.
Arey [7] proposed that the anomalous blood vessels may be because of
Developmentally, there are two arterial systems. One is primitive axial arterial system and second is superficial arterial system. The superficial artery arises from primitive axial artery. Both the primitive axial artery and the superficial artery divided into radial, ulnar, and median branches. There develop multiple anastomoses between the two systems. Normally, the deep trunks attain hemodynamic predominance resulting in the regression of superficial arterial system and its preanastomotic segments. However, postanastomotic segments of superficial system form the distal segments of radial, ulnar, and median arteries [Figure 5]a and b, [Figure 6]a, and [Figure 7]a. [5]
Ontogenically, the present case can be explained as follows. [5] On the right side [Figure 6]b]: Hemodynamic dominance was variably attained in different segments of two systems. The primitive axial artery forming deep brachial artery between main trunk and its three branches regressed so also its radial and ulnar branches, resulting in deep brachial artery ending at elbow. One of the anastomotic channels between superficial and deep systems along with the median branch of primitive axial artery formed common interosseous artery, which was seen as a branch of radial artery. The superficial arterial system except its median branch attained hemodynamic dominance and formed superficial brachial artery dividing into radial and ulnar arteries On the left side [Figure 7]b: Hemodynamic codominance was attained. The primitive axial artery continuing as deep brachial artery, running lateral to median nerve in the arm, continued as radial artery in the forearm. The median branch existed as common and anterior interosseous arteries. Common interosseous is a branch of radial artery. The superficial brachial artery running medial to median nerve in the arm continued as ulnar artery in the forearm. Thus, ulnar artery was seen running superficial to forearm muscles. The radial and median branches of superficial brachial artery so also the ulnar branch of deep brachial artery with smaller anastomotic channels between the two systems regressed. The continuation of superficial or deep brachial arteries into ulnar or radial arteries, respectively, may have been called by some authors as high origin of ulnar or radial arteries. [8] The superficial brachial artery has also been called as vasa aberrantia. [9] The knowledge of arterial variations is important for surgeons during surgeries to avoid complications so also during angiography to read the angiograms. Being superficial, the arteries can be vulnerable to trauma. Also, superficial position of arteries as variation must be kept in mind while doing intravenous injections or cardiac catheterization. Ulnar arteries passing deep to flexor retinaculum on both the sides may be affected in carpal tunnel syndrome. An orthopedic procedure as simply applying a plaster for fracture of forearm bones may compress the superficially placed arteries. Anomalous brachial artery can be used as an alternative choice of arterio-venous feeding artery. [10] Acknowledgment We acknowledge the technical staff of the Department of Anatomy for the help. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
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