The Median-Radial Type of Superficial Palmar Arch: A Case Report and Review of the Literature

The superficial palmar arch (SPA) of the hand is generally formed by the ulnar artery (UA) and superficial palmar branch of the radial artery (RA). Very rarely, however, the SPA is formed by the median artery (MA) and RA. This was termed the median-radial type (MRT) of SPA by Adachi in 1961 in Keen (Am. J. Anat. 108: 245-61). The recent use of the RA as a coronary artery bypass graft in myocardial revascularization makes the MRT of SPA clinically more significant. The SPA is a direct continuation of the ulnar artery. Upon entering the palm, the ulnar artery curves laterally behind the palmar aponeurosis and in front of the long flexor tendons. The arch is completed on the lateral side by one of the branches of the RA, the superficial palmar branch, the arteria radialis indicis (ARI) or the princeps pollicis. According to Adachi in Keen (1961) there are 3 types of SPA: type I, or “ulnar”, has a minimal or absent contribution from the radial artery; type II, or “radio-ulnar”; and type III, or “median-ulnar”, in which the median artery is strong enough to irrigate the palm of the hand and be a part of the arch. The author also described a very rare type of SPA, where the MA anastomoses with the RA, resulting in a minimal or absent contribution from the ulnar artery (median-radial type of SPA). Although the radial and ulnar arteries provide the majority of the blood supply to the hand, additional circulation may come from the median artery or the interosseous arterial system. Various anomalous patterns in the arterial arches have been studied, and a classification based on the relationship between the superficial branches of the RA and the UA has been proposed by various authors. The paucity of literature regarding the median-radial type of SPA makes additional case reports related to this variation particularly interesting for clinicians, surgeons and anatomists