A rare case of partial posterior interosseous nerve injury associated with radial head fracture

Abstract

A previously fit and healthy 28-year old male sustained a fracture of the right acetabulum and left radial head following a road traffic accident. His radial head fracture was a closed marginal segmental undisplaced fracture (Mason type 1). Sensation in the hand and forearm were intact. He had good extension in his index and little fingers but poor extension in his ring finger and no extension in his middle finger at the metacarpo-phalangeal joint (Fig. 1). This has been described as the ‘sign of horns’ (Fig. 2) resulting from partial injury to posterior interosseous nerve. This presentation was due to extensor digitorum paralysis with preservation of the extensor indices and extensor digiti minimi. Weak extension at the metacarpo-phalangeal joint of the ring finger was probably due to extensor digiti minimi giving a slip to the ring finger. His radial head fracture and nerve palsy were treated non-operatively with analgesia and early mobilization. After 2 months, he showed progressive recovery.