Factors Associated with Non-Unions of Fifth Metatarsal Fractures.

Objectives: Metatarsal fractures account for 5-6% of all fractures presenting to emergency care centers with 68% being fifth metatarsal (5MT) fractures. While most heal uneventfully, non-union is one of the most common complications regardless of treatment modality. Predicting the risk for non-union would potentially change treatment decisions thus lowering burden on patients and the healthcare system. The aim of this study was to identify factors associated with non-union in 5MT fractures. Methods: In this retrospective case-control study, 731 patients met inclusion criteria. Radiographs and clinical documentation were utilized to determine fracture characteristics and final healing status. 547 were assigned to the union group and 184 to the non-union group. Patients' data were gathered and analyzed using machine learning methods, as well as Mann-Whitney U, Pearson R chi-square test, and multivariable logistic regression analysis. P<0.05 was considered statistically significant. Results: The overall radiographic non-union rate was 25.2%. The highest incidence of non-union was observed for Zone 3 fractures (31.2%). Fracture displacement (P=0.03) was found to have an independent correlation with healing. Several chronic conditions such as osteoporosis (P=0.03), irritable bowel syndrome (P=0.01), cardiovascular disease (P=0.01) and sleep apnea (P=0.03), were found to have an independent correlation with healing. Beta-blockers (P=0.047) and topical steroids (P=0.04) were also found to be associated with 5MT non-union. Conclusion: In this study, we identified several non-traditional factors associated with 5MT fracture non-union that warrant further consideration and may assist clinicians during the decision-making process. The relationship between non-fracture related factors with non-union needs to be further examined via larger clinical studies before causality can be determined and designation of those variables as risk factors.