Ulnar Nerve Entrapment

Ulnar nerve entrapment

Ulnar nerve entrapment is the second most common peripheral nerve compression after carpal tunnel syndrome. Emergency clinicians should be able to recognise typical patterns, localise the lesion (elbow versus wrist), identify red flags requiring urgent referral, provide immediate symptom control and safety advice, and arrange appropriate investigations and follow‑up.

Anatomy and common sites

The ulnar nerve (C8-T1) travels medially down the arm, passes posterior to the medial epicondyle through the cubital tunnel at the elbow, and enters the hand via Guyon’s canal at the wrist.

The two common entrapment sites are:

• Cubital tunnel (elbow) - the most frequent site.
• Guyon’s canal (wrist) - second most common.

Predisposing mechanisms include:

• Repetitive elbow flexion.
• Prolonged pressure on the medial elbow (e.g. leaning).
• Osteophytes or bony deformity.
• Previous fracture or scar.
• Soft tissue masses (ganglion, lipoma).
• Nerve subluxation.
• Systemic disease (e.g. diabetes).

Clinical features

Symptoms range from intermittent paresthesia to progressive motor weakness and wasting.