The ulnar (Guyon’s) canal is a fibro-osseous tunnel located at the level of the palm. It transmits the ulnar neurovascular bundle from the forearm into the hand.
In this article, we shall look at the anatomy of the ulnar canal – its borders, contents, and clinical relevance.
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Borders
The ulnar canal is approximately 4cm in length. It extends from the proximal aspect of the pisiform bone to the origin of the hypothenar muscles at the hook of hamate.
Its borders consist of:
- Medial (ulnar) – pisiform, flexor carpi ulnaris tendon, abductor digiti minimi muscle.
- Lateral (radial) – hook of hamate.
- Roof – palmar carpal ligament.
- Floor – flexor retinaculum, pisohamate ligament, and hypothenar muscles.
Fig 1
The borders of the ulnar canal
Pro Feature - Dissection Images
Contents
The ulnar canal conveys the ulnar neurovascular bundle into the hand:
- Ulnar nerve – bifurcates within the canal into superficial (sensory) and deep (motor) branches.
- Ulnar artery – located on the radial aspect of the ulnar nerve. It gives rise to a deep palmar branch and continues laterally across the palm as the superficial palmar arch.
- Venae comitantes of ulnar artery
- Lymphatic vessels
Clinical Relevance
Ulnar Canal Syndrome
Ulnar canal syndrome refers to compression of the ulnar nerve within the ulnar canal. The most common causes are ganglion cyst, lipoma and trauma.
Its clinical features are related to compression of the ulnar nerve and its branches:
- Sensory – pain and paraesthesia ulnar 1 1/2 digits
- Motor:
- Weakness of thumb adduction (adductor pollicis)
- Weakness of finger abduction and adduction (interossei)
- Weakness of little finger flexion, abduction and opposition (hypothenar muscles)
Initial treatment is usually conservative – analgesia, activity modification, splinting of the wrist. Surgical decompression can be considered in patient who fail conservative measures.
Fig 2
Ulnar canal syndrome can cause pain and paraesthesia in the distribution of the ulnar nerve.