Uncommon type 3 Monteggia equivalent lesion due to an ulnar shaft nonunion in adults: A case report.

It is uncommon to observe a nonunion of an isolated ulnar shaft fracture after surgical treatment; therefore, complications due to this nonunion are very rare. Adults are more likely to develop nonunions compared to children. We report the case of a 34-year-old man, who had a left ulnar shaft fracture, treated with a screwed plate. Four months later, a septic nonunion occurred causing a type 3 Monteggia equivalent lesion with a lateral dislocation of the radial head. We describe the consecutive methods of treatment that resulted in complete bone consolidation. The case report aims to underline the diagnostic particularities and the therapeutic challenges of this rare complication.