Risk Factors for Failure of Nonsurgical Management of Ulnar Shaft Fractures.

PURPOSE: Isolated ulnar shaft fractures are frequently managed nonsurgically. However, rates of nonsurgical treatment failure remain substantial, and risk factors for the failure of nonsurgical management are not well described. This study investigated radiographic and patient-specific risk factors for the failure of nonsurgical management of isolated ulnar shaft fractures. METHODS: A retrospective review of patients with ulnar shaft fractures initially treated nonsurgically was performed at two tertiary referral centers over a 19-year period from 2001 to 2020. Patient- and injury-related variables, surgical interventions, and plain radiographic measurements were recorded. The outcome of interest was failure of nonsurgical management, defined as failure to achieve fracture union nonsurgically within 3 months of injury. RESULTS: One hundred fifty four patients initially treated nonsurgically for isolated ulnar shaft fractures were included. Twenty six patients (17%) experienced failure of nonsurgical management; these included five nonunions, 16 delayed unions, and 10 conversions to surgical management. Patients who experienced failure of nonsurgical management had a higher prevalence of diabetes mellitus, a higher employment rate, and fractures with higher initial median posteroanterior and lateral translations, fracture gap, and angulation; 83% of the patients with an initial fracture gap of ≥4 mm and 41% of the patients with an initial fracture angulation of >10° failed nonsurgical management. CONCLUSIONS: Although most ulnar shaft fractures heal successfully with nonsurgical management, a substantial percentage of these fractures do not. Patients who are currently working, have diabetes mellitus, or have fractures with an initial fracture gap of ≥4 mm or an initial fracture angulation of > 10° may be more likely to fail nonsurgical treatment, although additional studies with larger sample sizes are needed to confirm these associations. TYPE OF STUDY/LEVEL OF EVIDENCE: Prognostic IV.