Tardy posterior interosseous nerve palsy resulting from residual dislocation of the radial head in a Monteggia fracture: a case report.

INTRODUCTION: We report an extremely rare case of tardy posterior interosseous nerve palsy that developed 40 years after unreduced anterior dislocation of the radial head in a Monteggia fracture.

CASE PRESENTATION: A 46-year-old Asian woman was diagnosed with tardy posterior interosseous nerve palsy resulting from residual dislocation of the radial head in a Monteggia fracture. The patient remembered that she had sustained a fracture to the right elbow when she was 6 years old but could not remember the details of either the injury or its treatment. Intra-operatively, the posterior interosseous nerve was compressed at the radial head, wrapped around the medial side of the radial neck, and ran into the distorted supinator muscle, and was stretched. We therefore excised the radial head and performed neurolysis. The function of the right hand was normal at a follow-up examination 8 months after surgery.

CONCLUSION: We theorize that excessive repeated motion with loss of elasticity of surrounding tissues because of long-term dislocation of the radial head may cause delayed posterior interosseous nerve palsy. It is necessary to make an accurate diagnosis and render proper treatment when a Monteggia fracture occurs, making sure that the radial head does not remain dislocated, to avoid possible posterior interosseous nerve palsy due to excessive pronation and supination even several decades later.