Posterior interosseous nerve injury complicating ulnar osteotomy for a missed Monteggia fracture

We describe a 6-year-old boy with a posterior interosseous nerve injury after an ulnar osteotomy for a chronic Monteggia lesion. Although the first consultant did an ulnar osteotomy to reduce the radial head, the posterior interosseous nerve palsy did not recover. Next we found that the posterior interosseous nerve had been drawn into the radiocapitellar joint. It is important to confirm interposition of the nerve at the radiocapitellar joint during corrective osteotomy for a chronic Monteggia lesion.