Embryogenesis of the upper limb vascular tree involves a series of dynamic events, including the formation of the superficial palmar arch (SPA). The arterial supply of the hand begins as the seventh intersegmental artery, which eventually becomes the subclavian artery and capillary plexus in the distal portion of the hand, forming arches and digital arteries. The median artery (MA), a branch of the anterior interosseous, typically regresses at the level of the elbow. The palmar capillary plexus differentiates into superficial and deep arches, with the radial artery (RA) and ulnar artery (UA) located deep and superficial, respectively. The RA and UA display a range of anastomosing vascular calibers depending on their vascular arborization, thereby affecting blood perfusion to the digits. Incorrect grafting within these structures or trauma to the area poses a risk of accelerating vascular pathologies [1,2].

The SPA is one of the important arterial structures necessary for proper vascularization of the hand. Procedures such as hand replantation or transplantation, post-traumatic revascularization, and composite tissue transfer may involve the SPA, making familiarity with its morphological variations clinically relevant in select surgical contexts [3]. Variation in arterial structures arises from aberrations in angiogenic signaling during vascular development in utero and often develops proportionally within the individual [4-6]. Arising from the mesodermal angioblast precursor cells, vasculogenesis of the vessels is driven by basic fibroblast growth factor, which initiates cellular migration in the embryo to form loose cords [7,8]. It has been hypothesized that morphological variation of vessels can also result from postnatal vasculogenesis, in which vascular endothelial growth factor stimulates proliferation of bone-marrow-derived endothelial precursor cells [9,10]. While most variations are unremarkable, some result in hand and digital ischemia requiring surgical intervention [11,12]. In this study, we examined the anatomical variation of the SPA, documenting patterns that may inform reconstructive microsurgical procedures of the hand, such as posterior interosseous artery flap reconstruction [12,13]. Moreover, a robust knowledge of variant arterial arch patterns, arterial diameter capacity, and subsequent comprehensive surgical-anatomical implications is instrumental [14,15].

In the most common pattern, the SPA represents the principal continuation of the UA, which courses laterally deep to the palmar aponeurosis to anastomose with the superficial palmar branch of the RA on the lateral aspect of the hand. This configuration gives rise to the ulnar metacarpal arteries supplying the second, third, and fourth lumbrical muscles, as well as a single proper palmar digital artery along the medial aspect of the little finger. Previously described variations include formation of the SPA solely by the UA or through anastomoses between the UA and the princeps pollicis artery, arteria radialis indicis, or MA [11,13,16-18]. The classification system proposed by Coleman and Anson [19] remains one of the most commonly used frameworks for describing morphological variation of the SPA. While these variations are known, their relative prevalence, anatomical presentation, and correspondence to a standardized classification framework remain inconsistently characterized. Using cadaveric palms and applying the Coleman and Anson classification, this study systematically documents SPA variants, quantifies their distribution, and evaluates their relevance to surgical anatomy. By correlating observed configurations with established classifications, this work provides a more comprehensive and standardized understanding of SPA diversity, offering practical insights for surgical planning and anatomical education.

Morphological variation of the SPA was observed during dissection of ten cadavers. Variation was also noted between the right and left hands of individual cadavers, and differences in SPA patterns were apparent across different cadavers. A wide spectrum of complete and incomplete configurations was observed, underscoring the heterogeneity of superficial palmar arterial anatomy. Among our findings, only one hand demonstrated the classic radial-ulnar anastomotic configuration.

On the right hand of M1, the classical radial-ulnar arch was present, formed by the superficial palmar branch of the well-developed RA and UA. This configuration represents the typical Type 1 complete arch in which both arteries contribute to the superficial palmar circulation. From this arch, branches arose and bifurcated to supply the digits, serving as a reference pattern for comparison with less common configurations (Figure 1).

A more complex and uncommon arrangement was observed in the left hand of M1. In this corpse, the superficial palmar circulation arose predominantly from a dominant ulnar-derived vessel that supplied multiple digital branches, including branches to the medial and lateral aspects of the fourth digit and the lateral aspect of the third digit. Distally, the vessel terminated as a small bifurcation coursing deep toward the second digit, where communication with a deeper arterial branch was suspected. Although the course and depth of this terminal branch raise the possibility of contribution from the MA, definitive identification could not be established without further exploration of the deep palmar plane. Consequently, this configuration did not conform precisely to a defined Coleman and Anson classification, but most closely resembled a mirror-image variant of the rare Type 2 complete arch. Unlike a true Type 2 pattern, however, the RA was observed to traverse the anatomical snuffbox without contributing to the formation of the SPA, which was supplied predominantly by the UA (Figure 2).

In the right hand of F2, the SPA demonstrated a complete configuration in which the UA formed the primary transverse arch, with completion provided by a radial-derived contribution entering the palm between the heads of the first dorsal interosseous muscle and anastomosing with the terminal portion of the UA. This anastomosis resulted in a continuous arterial loop across the palm, consistent with a Type 1 complete arch (Figure 3).

Several specimens demonstrated incomplete arches characterized by ulnar dominance and absence of a transverse anastomosis. In the right hand of F1, reflection of the palmar tissues revealed a SPA formed exclusively by the UA. The UA gave rise to three common palmar digital branches supplying the third and fourth digits and the medial aspect of the fifth digit, as well as a proper palmar digital artery to the medial side of the fifth digit. No anastomotic contribution from the radial or median arteries was identified, consistent with a Type 1 incomplete arch (Figure 4).

In the left hand of F5, the SPA was formed exclusively by the UA, which coursed transversely across the palm and gave rise to the common palmar digital arteries without contribution from a superficial palmar branch of the RA. The absence of a transverse anastomosis resulted in a unilateral ulnar pattern of superficial palmar circulation, consistent with a Type 1 incomplete arch (Figure 5).

A similar incomplete configuration was observed in the left hand of M5. In this specimen, the UA formed the SPA and supplied three common palmar digital arteries, which subsequently bifurcated into proper digital branches. No radial or median arterial contribution was identified, and no anastomotic connection was present. The arch lay superficial to the flexor tendons and followed a typical transverse course across the distal palm, confirming a Type 1 incomplete ulnar-derived configuration (Figure 6).

Traditional hand performance is rated on the dexterity of thumb and finger movements. Movement is heavily dependent on the number of muscles intersecting a particular digit. The distal branch of the superficial arch should have a higher rate of perfusion or a larger arterial diameter due to dual vasculature and its increased mobility and muscle involvement in moving the index finger. The index finger is attached to an extra-extensor muscle, which requires additional vascular support from digital arteries such as those stemming from the superficial arch. Mobility of the index fingers results from the action of several muscles: extensor indicis, extensor digitorum communis, flexor digitorum profundus, flexor digitorum superficialis, the first lumbrical, and the interossei muscles. As a result of these muscle attachments, the index finger (second digit) requires greater oxygen perfusion and is richly supplied with vasculature.

One may ask how this is relevant to the perfusion of other digits in the hand or what best practices exist to ensure maximal perfusion following surgical intervention or when the SPA becomes the arterial graft site. Updated classification of the SPA depends on the continuity of the anastomosis circle within the deep arch, as it is considered more surgically reliable [19]. Notably, upwards of 59% of arches are ulnar type, with minimal or absent contribution from the RA [1,3]. Due to favorable anastomosis between the contributing vessels, the arches offer a highly beneficial collateral supply to the hand. In the absence of vascular disease, the RA can therefore be safely harvested for graft surgeries. A common example is coronary bypass surgery, where the UA's collateral supply prevents ischemic changes in the hand post-harvesting [17,18,20].

Although these anastomoses are common, preoperative assessment of collateral circulation may be considered in selected hand procedures, as anatomical continuity does not always correspond to functional perfusion [17]. Current protocol is based on collateral perfusion from the MA, but this is not always reliable, as the MA typically regresses in the second month of intrauterine life. If the MA does not regress, there will be variation from early vasculogenesis when the anterior interosseous artery becomes the MA. The resulting MA will present in two different patterns: palmar type (reaches the palm) and the antebrachial type (ends in the forearm) [18]. The palmar type of the MA traverses the carpal tunnel alongside the MN and has been reported as a rare anatomical variant that may be encountered in association with carpal tunnel syndrome [21]. Surgical intervention for carpal tunnel syndrome is well established [22] and is not further discussed in this case study.

We focused our analysis on the superficial palmar site. The index branch of the SPA was consistently identifiable, potentially reflecting its anatomical relationship with muscle attachments and the functional dynamics of the digits. Future studies could examine our findings in a clinical setting, evaluating methods to improve preoperative visualization of vascular variation, potentially using adjuvant arteriography to identify hidden arterial connections. Such visualization may support more precise surgical handling of the SPA. Steve et al. [20] demonstrated that a novel reconstruction utilizing the subscapular arterial system to reconstruct arterial vasculature, such as the SPA, demonstrated a promising arterial interposition graft, offering an optimal branching pattern along with generous graft length and perfusion. The applications of arterial grafts from the SPA are vast. Even with a small sample size, we observed dynamic variation between the SPAs in our cadavers. We believe this indicates that vascularity and perfusion differences among patients may be even greater than the current ratios reported in the literature.

Strengths of this study include the use of the Coleman and Anson classification system to categorize SPA variations, bilateral comparison of cadaveric hands, and documentation of both common and rare anatomical patterns. By linking these observations directly to clinical contexts such as grafting and reconstructive procedures, this work underscores the importance of individualized vascular assessment in surgical planning. Although this study has notable strengths, there were also several limitations. The small sample size of ten cadavers restricts the generalizability of our findings. All donors were elderly, which may have introduced age-related vascular changes not representative of younger populations. Functional perfusion assessments, such as dye injection or angiography, were not performed, and the deep palmar arch was not consistently examined in all cases, limiting our ability to fully map collateral circulation. Future research should include larger and more diverse samples, integrate functional imaging, and evaluate both superficial and deep palmar arches to provide a more comprehensive understanding of vascular variation in the hand.

This study demonstrates substantial variability in the morphology of the SPA. Differences were observed both between specimens and between the right and left hands of individual cadavers, indicating that SPA anatomy is highly variable and not reliably predictable. While many configurations could be described using the Coleman and Anson classification system, some patterns did not conform clearly to defined categories. These findings emphasize the importance of careful anatomical assessment of the superficial palmar system during surgical and interventional procedures involving the hand.