Innervation of the extensor carpi radialis brevis and supinator muscles: Levels of origin and penetration of these muscular branches from the posterior interosseous nerve.

Dissections of 30 upper extremities from 15 skeletally mature cadavers were performed to identify the levels of origin and penetration of the innervation of the extensor carpi radialis brevis and supinator muscles. The humeroradial joint was used as a reference point for measurements. The most common pattern of extensor carpi radialis brevis innervation consisted of a single origin from the posterior interosseous nerve at the level of the humeroradial joint branching to penetrate the muscle at a level 30 mm to 60 mm distal to the humeroradial joint. The common innervation pattern of the supinator consisted of multiple origins from the posterior interosseous nerve at a level 0 mm to 30 mm distal to the humeroradial joint with multiple penetrations into the muscle at a level 10 mm to 40 mm distal to the humeroradial joint. Although there is variability in the innervation of the extensor carpi radialis brevis and supinator, our data provide useful patterns concerning the anatomy of these muscular branches from the posterior interosseous nerve. More complete knowledge of this anatomy allows safer approaches for the surgical exposure of the radius and improved diagnosis and localization of radial nerve lesions in the proximal forearm, with improved predictability of recovery of nerve injuries.