Misdiagnosis of OTA type B (Weber B) ankle fractures leading to nonunion.

Little is known about the specific etiology of nonunion of stable Orthopaedic Trauma Association (OTA) type B fractures. In the present retrospective cohort study, we investigated all patients with a nonunion in a level 1 trauma center during an 8.5-year period. Patient history, clinical findings, radiographic features, and therapeutic aspects were critically evaluated to be able to predict the nonunion. In the predefined period, 388 patients were treated for a stable OTA type B fracture. Eight patients (2.1%) developed a nonunion. Retrospectively, the radiographic features in 6 of the 8 patients and clinical findings in 1 of the 8 patients could predict the nonunion. We conclude that in almost every nonunion occurring after a "stable" OTA type B fracture in the present study were, in fact, originally unstable fractures.