Areas - Ulnar Canal

Question 1

What is the ulnar canal?

Answer 1

Ulnar (or 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.

Question 2

Borders?

Answer 2

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, pisohamate ligament and abductor digiti minimi.
• Lateral (radial) - hook of hamate
• Roof - palmar carpal ligament
• Floor - flexor retinaculum and hypothenar muscles.

Question 3

Contents?

Answer 3

The ulnar canal conveys the neurovascular bundle into the hand:

1) Ulnar nerve - bifurcates within the canal into superficial (sensory) and deep (motor) branches.
2) 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.
3) Venae comitantes of ulnar artery
4) Lymphatic vessels

Question 4

Clinical relevance - ulnar canal syndrome?

Answer 4

This syndrome refers to compression of the ulnar nerve within the ulnar canal. The most common causes are ganglion cyst, lipoma and trauma.

Its clinical feature are related to compression of the ulnar nerve and its branches:

1) Sensory - pain and paraesthesia ulnar 1 and a 1/2 digits.
2) Motor:
- Weakness of thumb adduction (adductor pollicis)
- Weakness of finger abduction and adductio (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.