M01.03.008 Ulnar (Guyon’s) Canal

The ulnar (Guyon’s) canal is a crucial anatomical structure located at the level of the palm, transmitting the ulnar neurovascular bundle from the forearm to the hand. Understanding its anatomy and clinical significance is vital for diagnosing conditions like ulnar canal syndrome, which can result from compression of the ulnar nerve. In this article, we will examine the borders, contents, and clinical relevance of the ulnar canal.

1. Borders of the Ulnar Canal

The ulnar canal is a fibro-osseous tunnel approximately 4 cm in length, located at the palm. It extends from the proximal aspect of the pisiform bone to the origin of the hypothenar muscles at the hook of hamate.

Table: Borders of the Ulnar Canal

Points to Remember:

• The ulnar canal is approximately 4 cm in length.
• It extends from the pisiform bone (proximal) to the hook of the hamate (distal).
• The ulnar nerve and artery pass through this canal.

2. Contents of the Ulnar Canal

The ulnar canal conveys important structures into the hand, including both sensory and motor components.

Table: Contents of the Ulnar Canal

Points to Remember:

• The ulnar nerve bifurcates into sensory and motor branches.
• The ulnar artery continues as the superficial palmar arch.
• The ulnar artery and its venae comitantes pass alongside the nerve.

3. Clinical Relevance: Ulnar Canal Syndrome

What is Ulnar Canal Syndrome?

Ulnar canal syndrome refers to the compression of the ulnar nerve within the ulnar canal, often resulting in symptoms related to both sensory and motor dysfunction.

Common Causes:

• Ganglion cysts
• Lipomas
• Trauma

Symptoms of Ulnar Canal Syndrome:

• Sensory symptoms:
  • Pain and paraesthesia in the ulnar 1.5 digits (little finger and half of the ring finger).
• Motor symptoms:
  • Weakness in thumb adduction (affecting the adductor pollicis).
  • Weakness in finger abduction and adduction (affecting the Interossei muscles).
  • Weakness in little finger flexion, abduction, and opposition (affecting hypothenar muscles).

Treatment:

• Conservative:
  • Analgesia, activity modification, and wrist splinting.
• Surgical:
  • Decompression in cases where conservative measures fail.

Figure: Ulnar Canal Syndrome Symptoms

Ulnar canal syndrome can lead to sensory and motor impairments in the distribution of the ulnar nerve, especially in the fingers and hands.

Points to Remember:

• Ulnar canal syndrome is typically caused by external compression (e.g., cysts, trauma).
• The ulnar nerve is primarily responsible for motor control of hypothenar muscles and sensation in the medial aspect of the hand.