Thumb and Guyon Canal Approaches

Diagram of the zones of the Guyon canal at the wrist with the ulnar nerve branches, hypothenar muscles and pisiform labelled
Zones of the Guyon canal at the wrist and the structures in each zone. Image by Jmarchn, Wikimedia Commons, CC BY-SA 3.0.

Indications

  • Dorsal approach for thumb MCP and CMC arthrodesis, capsular repair and fixation
  • Wagner volar approach for Bennett fracture fixation and trapeziometacarpal surgery
  • Bruner volar incisions for flexor pollicis longus repair, volar plate injury and contracture release
  • Guyon canal release for ulnar tunnel syndrome, hook of hamate pathology, ganglion and ulnar artery thrombosis

Position

  • Supine with the arm on a hand table and a tourniquet
  • Pronated or neutral for dorsal thumb approaches
  • Supinated for Wagner, Bruner and Guyon approaches

Landmarks and Incision

  • Dorsal incision is curvilinear over the joint, with extensor pollicis longus ulnar and extensor pollicis brevis radial
  • Wagner follows the glabrous and non-glabrous skin junction along the first metacarpal, then curves ulnarly at the wrist crease
  • Bruner zigzag runs between the flexion creases with flap angles of 90° or more
  • Guyon incision curves over the canal between the pisiform and the hook of hamate

Superficial Dissection

  • Dorsal approach protects the superficial radial nerve branches and dorsal veins
  • Wagner detaches the thenar muscles from the first metacarpal base and reflects them palmarly
  • Bruner raises full thickness flaps to preserve the neurovascular bundles
  • Guyon divides the palmar fascia, palmaris brevis and volar carpal ligament (the roof)

Deep Dissection

  • Guyon floor is the transverse carpal ligament and pisohamate ligament
  • Ulnar wall is the pisiform and radial wall the hook of hamate
  • Zone 1 is proximal to the bifurcation (mixed)
  • Zone 2 holds the deep motor branch at the hook of hamate (motor)
  • Zone 3 holds the superficial branch (sensory) and the ulnar artery
  • Ulnar nerve lies ulnar to the ulnar artery

Structures at Risk

  • Superficial radial nerve branches and radial artery on the dorsal thumb
  • Dorsal sensory branch of the radial nerve and abductor pollicis longus tendon in the Wagner approach
  • Digital nerves in Bruner flaps
  • Palmar cutaneous branch of the ulnar nerve over the Guyon roof
  • Deep motor branch around the hook of hamate

Extension

  • Bruner extends into the palm
  • Guyon continues into carpal tunnel release or ulnar forearm incision

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 20 October 2026.