During routine dissection of the upper extremity for undergraduate students in the department of anatomy in the Medical Faculty of Tabriz University, a unilateral variation of SPA was noticed in the right hand of an Iranian male cadaver, which was embalmed in formalin solution for 6 months in order to fixate. The dissection of the upper extremity was performed to exhibit the whole muscles, arteries, and vessels based on Cunningham’s manual of practical anatomy instructions (7). On the right side of the forearm area, three major artery branches were observed in the lower part of the cubital fossa (Figure 1). Between radial and ulnar arteries, the third major branch that is associated with the median nerve was considered as a median artery, which persists in only 4% cases of adults. However, the interosseous artery did not develop and accompanied by an interosseous nerve branch. Therefore, the median artery originated directly from the ulnar artery. The dissection process continued toward the hand to clear the terminal branches of these arteries. Surprisingly, the SPA was missed in the palm area, and the radial artery did not appear in the SPA. Median artery instead of radial artery irrigated the first and second interosseous spaces by 2 common palmar digital arteries. Then, the third and fourth common palmar digital arteries separately came from an ulnar artery, the medial side (Figure 2). More investigation was subsequently performed for exposing DPA. However, DPA did not involve any variations (Figure 3).

Figure 1. Arteries in the lower part of the cubital fossa
RA: Radial Artery, MA: Median Artery, UA: Ulnar Artery, MN: Median Nerve, UN: Ulnar Nerve

Figure 2. In the absence of SPA situation, MA instead of RA irrigated the first and second interosseous spaces; however, the third and fourth common palmar digitals separately came from UA
RA: Radial Artery, MA: Median Artery, UA: Ulnar Artery, MN: Median Nerve, UN: Ulnar Nerve
 

Figure 3. The absence of SPA with normal DPA
DPA: Deep Palmar Arch, RA: Radial Artery, MA: Median Artery, UA:  Ulnar Artery
 
Table 1. The classification of superficial palmar arches according to Coleman and Anson (from references 9)

Discussion

Human hand anatomy is the primary focus of surgeries and radiologist due to its complexity in vascularization and crucial role in microvascular surgery. Arterial supply for hand is derived from two superficial and deep palmar anastomotic arches. SPA is the principal vascular structure of the palm. Many attempts have been made to find the appropriate classification of vascular pattern in the hand region (8). The most famous one is the classification of Coleman and Anson based on which the superficial palmar arch has been classified into two groups, Group I and Group II, and each group has been divided into several subtypes (Table 1) (9). The predominant type is Group I (Type A), a superficial palmar branch of radial artery anastomosis with ulnar artery to form the arch. In the present study, the incomplete superficial arch has been discovered. This current variation in SPA fits into the Type C (Group II) category, according to Coleman and Anson classification (10). In a study conducted by Ikeda A et al. (1988), the complete arch was recorded in 96.4% of the cases and incomplete arch in the remaining 3.6% (11). However, a complete arch was reported in 84.4% of the cases in another study (12). Bataineh et al., in 2009, reported a rare variation in which superficial palmar arch was found in an incomplete type that has been formed by the median and ulnar artery. The princeps policies and radialis indicis arteries have been originated from a median artery. In addition, the ulnar artery supplied the most interosseous spaces except for the second space (13). In the present case report, an incomplete arch was found in which the ulnar artery directly supplied the third and fourth interosseous spaces. Also, the persistent median artery (PMA) was terminated uniquely as the common palmar digital for the first and second interosseous spaces. Accidental injury during surgical procedures or occluding artery on one side of the wrist could be compensated by collateral circulation. Hence, incomplete superficial palmar is important concerning the clinical aspect (5). Inefficient blood supply may induce digital ischemia and disturb movements of fingers and hands. Variations in the SPA may be due to initial persistence network of fetus vessels like the median artery, which normally undergoes regression in the embryonic period. PMA can originate from different sources, such as brachial, ulnar, radial, or interosseous arteries (14). In the present study, PMA raised from the ulnar artery. Clinically, MN may be compressed by the pressure of PMA; consequently, compressive neuropathies like Carpal Tunnel Syndrome (CTS) may happen (6). Embryological anatomical studies have suggested that the presence of the PMA may be explained with some theories. One distinct possibility is the retention of primitive patterns as a branch of the embryological axial artery. Another hypothesis explains that, in a proximal-to-distal differentiation pattern, the upper limb arteries develop from an initial capillary plexus. Variations in the formation of SPA or PMA may be a result of the differentiation, maintenance, and enlargement of certain capillary vessels while others undergo regression (6). Although the exact mechanism of this variation has not been identified, some factors, such as chemical factors, developmental arrest in early stages, fetal position in the uterus, and genetic factors, have been suggested to be involved in this variation (15,16). Knowledge of SPA variations or PMA is vitally important because of the contribution to many surgical and diagnostic problems.

Conclusion

It is noteworthy to consider this variation before any surgical practice or other interference in the hand region. Also, these relationships may have contributed to the diagnosis and treatment of various tunnel syndromes related to the MN or its branches.

 

Acknowledgements

The authors wish to thank all those who donate their bodies to advance the education and research.

 

Conflicts of Interest

Authors declared no conflict of interest.