Report of a rare human variation: absence of the radial artery.

A case of unilateral absence of the radial artery is reported. The arterial system of the specimen was developmentally primitive with the anterior interosseous artery the chief blood supply to the forearm and hand. A "superficial ulnar artery" of small caliber supplemented the supply of the hand. Three large branches of the anterior interosseous artery supplied the hand with the lateral terminal branch replacing the radial artery distal to the wrist. The superficial palmar arch was formed by an anastomosis of the media and lateral terminal branches of the anterior interosseous artery. No deep palmar arch was present, but three palmar metacarpal arteries arose from a perforating artery which branched from a large dorsal branch of the anterior interosseous artery. The median artery was of small caliber and could not be traced beyond the midforearm. Based on this specimen and a review of other forearm and hand arterial variations, it is postulated that the ulnar artery may developmentally precede the median artery.