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Radial Nerve at the Arm — Spiral Groove

nervus radialis (sulcus nervi radialis)

The radial nerve is vulnerable in the spiral groove of the humerus where it is directly applied to the bone — humeral shaft fractures at this level produce radial nerve palsy in 11-18% of cases. The nerve is also compressed here during 'Saturday night palsy' (arm draped over a chair back). Complete radial nerve palsy at the spiral groove produces wrist drop, finger drop, and thumb drop with preserved elbow extension (the triceps branch arises proximal to the groove).

Region: Upper Arm

Anatomical Data

Origin, Insertion & Supply

Origin	Posterior cord of the brachial plexus (C5-T1)

Clinical Relevance

Clinical Notes

Radial nerve palsy from humeral shaft fracture resolves spontaneously in 70% by 3-4 months — expectant management with functional splinting is first-line. EMG at 6 weeks confirms denervation and predicts recovery timeline. Failure to recover at 3-4 months prompts nerve exploration — identifying continuity (neuroma-in-continuity) vs transection (neurotmesis) guides repair vs grafting.

Pathology

Common Injuries & Conditions

Radial Nerve Palsy (Humeral Fracture)

Spiral groove radial nerve injury from humeral fracture producing wrist and finger drop — 70% spontaneous recovery managed with expectant splinting and EMG monitoring.