Radial nerve compression
Radial nerve compression (entrapment) is an uncommon but important cause of upper‑limb deficit. Presentations range from transient neuropraxia after fracture or external compression to focal compressive lesions of the posterior interosseous nerve (PIN).
This section summarises relevant anatomy, clinical localisation, practical emergency department (ED) assessment and investigations, initial management, indications for urgent referral, prognosis and common pitfalls.
Anatomy and common sites
- The radial nerve (C5-T1) is a mixed motor and sensory nerve.
- Course:
- It travels in the spiral (radial) groove of the humerus, passes anterior to the lateral epicondyle and divides in the proximal forearm into two branches.
- Superficial branch - sensory to the dorsoradial hand and dorsal radial 3½ digits.
- Posterior interosseous nerve (PIN) - mainly motor to finger and wrist extensors distal to the branch point.
- Typical sites of injury/entrapment:
- Humeral shaft / spiral groove - classically injured with mid‑shaft humeral fractures or iatrogenic during fixation/manipulation.
- Radial tunnel / supinator region in the proximal forearm - common site of PIN compression (radial tunnel syndrome / PIN syndrome).
- Distal forearm / wrist - trauma, laceration or local masses.
Clinical patterns and localisation
- Lesion proximal to the bifurcation (radial nerve):
- Motor: wrist drop (loss of wrist extensors), finger extension weakness, possible reduced supination or triceps weakness if the lesion is very high.