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Nerve Injuries of the Upper Limb — Radial, Median & Ulnar

General Surgery · Final Professional

Principle

Every upper-limb fracture carries a risk to a specific nerve because of the close anatomical relationship of nerve to bone. Recognising the pattern of motor and sensory loss localises the lesion and guides whether to observe or explore. Most closed traction (neurapraxia) injuries recover; a deficit appearing after manipulation, or with an open or penetrating wound, is explored.

Nerve	Typical injury	Motor loss / deformity	Sensory loss
Radial	Humeral shaft fracture; 'Saturday-night' palsy	Wrist drop — loss of wrist/finger/thumb extension	Dorsal first web space
Median	Supracondylar fracture; wrist laceration; carpal tunnel	'Ape thumb' (loss of opposition); 'pointing index' on making a fist	Radial 3½ digits (palmar)
Ulnar	Medial epicondyle fracture; elbow/wrist injury	'Claw hand' (ulnar 2 fingers); wasting of intrinsics	Ulnar 1½ digits

Bedside Tests Worth Knowing

Radial: ask the patient to extend the wrist and fingers — a wrist drop is unmistakable; sensation is tested in the dorsal first web space. median: test abduction/opposition of the thumb (abductor pollicis brevis); the 'pointing index' appears on trying to make a fist (the index cannot flex); Ochsner's clasp test. ulnar: Froment's sign (the patient flexes the thumb IP joint to grip paper because adductor pollicis is weak) and the card (Egawa) test for the interossei; a low ulnar lesion gives a more marked claw (the 'ulnar paradox').

Grading and Recovery (seddon)

The prognosis depends on the severity of the nerve injury, described by Seddon: neurapraxia (a conduction block from stretch or pressure — the commonest, and it recovers fully in days to weeks), axonotmesis (axons divided but the sheath intact — recovers slowly by axonal regrowth at roughly 1 mm/day), and neurotmesis (the nerve is completely divided — it will not recover without surgical repair). A closed traction injury is usually neurapraxia or axonotmesis and is watched, with splinting to prevent contractures and physiotherapy to keep the joints supple; recovery is monitored clinically (an advancing Tinel's sign) and by nerve-conduction studies at about 6 weeks if there is doubt.

DANGER / REMEMBER

A nerve deficit that appears after manipulation of a fracture, or one that accompanies an open or penetrating wound, should be explored — the nerve may be trapped or divided. A deficit present at the time of a closed injury is usually a neurapraxia and is observed.

Level of the lesion determines which muscles escape.

KEY POINT

Key points TO remember

Radial → humeral shaft fracture → wrist drop + sensory loss over the dorsal first web space.
Median → supracondylar fracture / carpal tunnel → 'ape thumb', 'pointing index', loss of thumb opposition; sensory loss over the radial 3½ digits.
Ulnar → medial-epicondyle / elbow injury → 'claw hand' of the ulnar two fingers, wasted intrinsics, Froment's sign positive; sensory loss over the ulnar 1½ digits.
Most closed (neurapraxia) injuries recover; a deficit appearing after manipulation, or with an open wound, is explored.

EXAM TIP

Sources: Maheshwari's Essential Orthopaedics; Apley & Solomon's System of Orthopaedics and Trauma; AO Principles of Fracture Management.

All questions in Upper Limb Trauma

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