The Anomalous Radial Artery: A Rare Vascular Variant and Its Implications in Radial Forearm Free Tissue Transfer

Abstract

The radial forearm free flap (RFFF) has become a workhorse for soft tissue reconstruction following surgical ablation of head and neck cancer. Given the popularity of the RFFF, it is important to understand potential variants of upper extremity vascular anatomy and the effects of these findings on pre- and intraoperative planning. The purpose of this series is to synthesize the existing literature to raise awareness for potential radial artery aberrations during planned reconstruction.

Introduction

The radial forearm free flap (RFFF) is a workhorse of head and neck soft tissue reconstruction. The RFFF is immensely popular due to its thin yet pliable skin, ability to include a variety of tissues along with the flap, and low donor-site morbidities. Although ulnar and radial artery anatomical abnormalities are rare, familiarity with them and their impact is of paramount importance to the reconstructive surgeon. We present two cases of radial artery abnormalities discovered during elevation of an RFFF. In addition, we outline the spectrum of radial artery anomalies as described in the English literature.

Discussion

The anatomy of the forearm vasculature is generally quite consistent. The radial artery branches off the brachial artery in the antecubital fossa, along with the ulnar artery. Distal to its origin, at the level of the radial head, the radial artery gives off a recurrent radial artery, which anastomoses with the radial collateral artery via the deep brachial artery. Septocutaneous branches from the radial artery supply the majority of the vascular needs of the forearm. Venous drainage typically involves two vena comitans, which follow the path of the radial artery.[1]

Given the nature of the RFFF and its role in reconstructive surgery, it is important to be aware of the possible aberrations found in its vascular supply. Literature review reveals several previously reported radial artery anomalies (

Table 1. Literature Review of Radial Artery Anomalies.

Radial Artery Anomaly	Source
Duplication of radial artery	[15,16]
Radial artery passing deep to pronator teres	[17]
Superficial dorsal antebrachial artery	[8,11,18,19,20]
Hypoplasia of radial artery	[6,7,21]
Aberrant dorsal course of radial artery around Lister’s tubercle	[22]
Absence of perforators from the radial artery to the skin	[13]
Distal origin of radial artery deep to pronator teres	[23]
Superficial dorsal antebrachial artery
High origin of radial artery
Aberrant midaxial vessel arising directly from the axial artery	[10]
High origin of the radial artery	[8,9,10,20,24,25,26,27,28]
Absent radial artery	[29]
Superficial radial artery lateral to normal vessel originating from it	[2]
Accessory branch of the radial artery at the level of mid forearm extending laterally subcutaneously into the dorsal wrist	[14]
Accessory branch of the radial artery	[5,26]
Duplication of the radial artery close to cephalic vein	[30]
Radial artery in the carpal tunnel	[31,32,33]

).[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33]

Cadaveric research by McCormack found radial artery variations in 4.3% of subjects.[8] Arteriographic examination by Uglietta and Kadir found aberrations in 9%.[9] Radial artery anomalies, primarily aplasia and hypoplasia, can be found in association with congenital malformation but quite often these vascular abnormalities are found in patients with no associated disorders.[5,6,7] Venkatanarasimha et al. most recently described a hypoplastic radial artery noted on computed tomography (CT) angiogram for evaluation of a hypothenar mass.[21] The contralateral side was not commented on; if the contralateral radial artery is present and patent, RFFF reconstructive planning can proceed accordingly, otherwise surgeons should pursue alternative options. In 2001, Porter and Mellow described an entirely absent radial artery.[29] In instances of absent radial artery, there is a described dominant anterior interosseous artery supplemented by an ulnar artery of varying caliber and a persistent small median artery. Given the anatomical abnormality, surgeons adjusted their preoperative planning to other reconstructive sites.

By far, the most described abnormality is a high radial origin, which has been described extensively in the literature.[8,9,10,24,25,26,27,28] High-origin radial arteries branch away from the axillary artery more proximally than normally described; this anomalous branching does not impact RFFF. Another abnormality reported is radial artery duplication. Li et al. documented duplication in 0.1% of 1400 transradial coronary angiography patients sampled via preprocedural ultrasound.[16] Occasionally, ultrasound may identify a dominant radial artery; consideration may also be given to the contralateral side (there was no note of bilaterality of findings) or the alternative site.

Accessory branches to the radial artery can occur (Figure 1), though locations at which the accessory vessels diverge and rejoin the radial artery are variable. Mordick described an aberrant vessel which originated at the axillary artery and paralleled the brachial artery on its course distally.[10] Funk et al. described a radial artery passing deep to the pronator teres rather than superficial to it.[17,23] In this report, preoperative Allen testing was normal, and the pronator teres was divided to secure the vessel.

We report a superficial dorsal branch of the radial artery (Figure 2); there are few previous reports in the literature of this anomaly.[8,11,18,19,20] Sasaki et al. discovered this anomaly intraoperatively and proceeded with the flap following equivocal intraoperative Allen testing. They noted cold intolerance in the affected hand postoperatively and recommended the use of either the contralateral forearm or an alternative flap site if this anomaly is detected preoperatively. Acaturk et al. described an accessory branch of the radial artery coursing superficially, naming it the superficial radial artery (SRA) in their report. In their report, the deep branch of the radial artery was taken leaving the superficial branch to perfuse the forearm and hand. Vadodaria, Brotherston, and Page recommended duplex scanning if this anomaly is suspected and disagreed with Sasaki et al. that a new flap site should be considered, proposing instead that if the SRA is identified preoperatively, the forearm flap could be based entirely on the SRA, leaving the dorsal branch to perfuse the forearm and hand.[34] To determine the viability of such a flap intraoperatively, the authors recommended releasing the tourniquet, performing an Allen’s test, and clamping the radial artery to evaluate perfusion of the flap.

Madaree and McGibbon discovered a radial artery that did not supply any fasciocutaneous perforators to the forearm.[13] In this case, the ulnar artery was chosen for the flap since it was providing all fasciocutaneous vascularization. Bhatt et al. discovered an aberrant vessel supplying the skin paddle, and this vessel was taken in favor of the radial artery to utilize the flap, the intraoperative Allen’s test was utilized in this case to determine which vessel was providing dominant supply to the skin paddle.[12]

Identification of these anomalies does not have to necessitate flap abandonment. The Allen’s test is useful in determining many of these abnormalities as described above, however cases exist in which Allen’s testing may be falsely favorable such as the superficial dorsal antebrachial arteries described by Funk et al. and Heden et al.[19] Ultrasound may be considered as an adjunct for vessel identification, specifically if abnormal Allen’s test is identified on examination. Many of the cases presented in the literature saw completion of reconstruction through either unchanged or adjusted procedures. These examples highlight the importance of early identification and evaluation of flap viability for reconstructive success.

Conclusion

Radial artery anomalies are rare, and their presence can have serious implications on the viability of the RFFF in select cases. Given this flap’s immense appeal to the reconstructive surgeon, it is important to be aware of possible abnormalities of the radial artery vasculature. Identifying these anatomical deviations may elicit change in surgical planning and prevent poor surgical outcomes.