M01.03.008 Ulnar (Guyon’s) Canal

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Learning Objectives

By the end of this article, learners should be able to:

Describe the anatomical location and borders of the ulnar (Guyon’s) canal
Identify the contents of the canal, including the ulnar neurovascular structures
Explain the clinical significance, including the presentation and management of ulnar canal syndrome

The ulnar (Guyon’s) canal is a fibro-osseous tunnel at the level of the palm, allowing the ulnar neurovascular bundle to pass from the forearm into the hand. It is clinically important as a site of nerve compression, which can lead to ulnar canal syndrome.

Borders

The ulnar canal is approximately 4 cm long, extending from the proximal aspect of the pisiform bone to the origin of the hypothenar muscles at the hook of the hamate. Its borders are defined as follows:

Medial (ulnar): Pisiform, flexor carpi ulnaris tendon, abductor digiti minimi
Lateral (radial): Hook of hamate
Roof: Palmar carpal ligament
Floor: Flexor retinaculum, pisohamate ligament, and hypothenar muscles

The ulnar canal transmits the ulnar neurovascular bundle into the hand:

Ulnar nerve – bifurcates within the canal into:
1. Superficial branch (sensory)
2. Deep branch (motor)
Ulnar artery – located radially to the nerve; gives rise to:
1. Deep palmar branch
  1. Continues laterally as the superficial palmar arch
Venae comitantes of the ulnar artery
Lymphatic vessels

Clinical Relevance: Ulnar Canal Syndrome

Ulnar canal syndrome occurs when the ulnar nerve is compressed within the canal. Common causes include:

Ganglion cysts
Lipomas
Trauma

Clinical Features:

Sensory:

Pain and paraesthesia affecting the ulnar one and a half digits

Motor:

Weakness of thumb adduction (adductor pollicis)
Weakness of finger abduction and adduction (interossei)
Weakness of the little finger flexion, abduction, and opposition (hypothenar muscles)