The superficial palmar arch is the primary arterial supply to the fingers, formed predominantly by the ulnar artery with a variable radial contribution. The Allen test assesses its integrity by compressing both radial and ulnar arteries at the wrist and releasing them alternately while observing palmar flushing. The arch depth in the palm corresponds to the outstretched thumb tip, making this the anatomical landmark for carpal tunnel incisions — cutting distal to this line risks injuring the arch.
| Origin | Continuation of the ulnar artery into the palm, completing the arch with a contribution from the superficial palmar branch of the radial artery |
|---|
The superficial palmar arch is the primary reason that the carpal tunnel incision must stay proximal to a line corresponding to the outstretched thumb tip (Kaplan's cardinal line). The arch can be lacerated in deep palm lacerations, producing significant haemorrhage that is difficult to control due to the arch's central position. The Allen test before radial artery harvest for coronary bypass or arterial line insertion confirms adequate ulnar collateral circulation through the superficial arch.
Deep palm laceration transecting the superficial arch producing significant digital artery haemorrhage requiring surgical repair for hand viability.
