Intramedullary entrapment of the radial nerve associated with humeral shaft fracture.

We present an unusual case of a humeral shaft fracture with intramedullary entrapment of the radial nerve by an undisplaced posterior triangular fragment tightly fixed to the lateral intermuscular septum. Initial examination showed a complete high radial nerve palsy and an angulated mid-shaft humeral fracture associated with an undisplaced posterior triangular fragment. After failure of several closed reductions, we decided to attempt an open reduction and internal fixation with simultaneous exploration of the radial nerve. During surgery, the radial nerve was found emerging from the medullary canal of the proximal fragment. The nerve was freed by briefly displacing the undisplaced posterior triangular fragment. The fracture was then reduced and fixed by plate and screws. Six months after the operation, there was full recovery of the radial nerve and complete union of the fracture. Clearly, closed intramedullary nailing would be contraindicated in this particular type of associated radial nerve injury. We therefore suggest that in cases of mid-shaft fractures of the humerus with associated radial nerve palsy, and an undisplaced posterior triangular fragment, consideration should be given to the possible entrapment of the radial nerve in the medullary canal.