Superficial Palmar Arch

Introduction

Introduction to the Superficial Palmar Arch

The superficial palmar arch is the principal arterial arcade of the palm, lying just deep to the palmar aponeurosis. It is formed predominantly by the ulnar artery, with a variable contribution from the superficial palmar branch of the radial artery. The arch gives off the common palmar digital arteries that supply the medial four digits and is the main source of digital blood flow. Its superficial location makes it vulnerable to penetrating trauma, and its variations have profound implications for hand revascularisation and reconstructive surgery.

This module covers the origin, course, branches, anatomical variations, and clinical significance of the superficial palmar arch.

Study

1. Formation and Course

The superficial palmar arch is formed primarily by the terminal part of the ulnar artery, which enters the palm through Guyon's canal, lateral to the pisiform. The artery then curves laterally, deep to the palmar aponeurosis and superficial to the long flexor tendons, to meet the superficial palmar branch of the radial artery. This anastomosis is typically complete, creating a continuous loop, but in up to 20% of individuals the arch is incomplete.

The arch lies at the level of the distal border of the fully extended thumb (Kaplan's cardinal line), an important surface landmark for surgical approaches.

2. Branches

The superficial palmar arch gives rise to four common palmar digital arteries. These run distally in the palm, each dividing into two proper palmar digital arteries that supply the adjacent sides of digits 2–5.

Specifically: The first common palmar digital artery supplies the ulnar side of the index finger and radial side of the middle finger. The second supplies the ulnar side of the middle finger and radial side of the ring finger. The third supplies the ulnar side of the ring finger and radial side of the little finger. The fourth is a short branch to the ulnar side of the little finger. The thumb and radial side of the index finger are supplied by the princeps pollicis artery (from the deep arch) and the radialis indicis artery.

Additional small branches supply the palmar skin, the lumbrical muscles, and anastomose with the deep palmar arch via perforating branches.

3. Relations

Superficially, the arch is covered by the palmar aponeurosis and palmaris brevis muscle. Deep to the arch lie the tendons of flexor digitorum superficialis and profundus, the lumbrical muscles, and the terminal branches of the median nerve. The common palmar digital arteries are accompanied by the common palmar digital nerves (from median and ulnar nerves) which lie volar to the arteries.

4. Anatomical Variations

The superficial palmar arch is classically described as an anastomosis between the ulnar artery and the superficial palmar branch of the radial artery. However, variations are frequent. The arch may be complete (about 80%) or incomplete (20%), where the radial contribution is absent and the digital arteries arise directly from the ulnar artery. The arch may be dominant radial (radial artery supplies the majority of the digits) or median (the median artery persists and contributes). Understanding these variations is critical for safe hand surgery and for planning radial artery harvest.

5. Clinical Significance

Allen's test: Pre‑operative assessment of ulnar collateral flow before radial artery cannulation or harvest relies on the integrity of the superficial palmar arch.

Laceration of the arch: Deep palmar lacerations can transect the arch, causing pulsatile haemorrhage. Ligation may compromise digital perfusion if collateral flow is insufficient.

Embolic events: Small emboli from proximal sources can occlude the digital branches, leading to finger ischaemia.

Flap design: Many local flaps in hand surgery are based on the perforating branches of the superficial arch or its digital tributaries.

Summary

Summary of the Superficial Palmar Arch

The superficial palmar arch is the main arterial supply to the medial four digits. It is formed primarily by the ulnar artery, with a variable contribution from the radial artery, and lies superficial to the flexor tendons deep to the palmar aponeurosis. Its branches are the common palmar digital arteries. Knowledge of arch completeness and variations is essential for vascular assessment and hand surgery.