Evaluating Negative Margins in Foot Amputations for Diabetic Osteomyelitis: How Do We Decide?

Background. Amputation level in diabetic foot osteomyelitis (DFO) is most determined based on surgeon visualization of macroscopic criteria, leading to subjective variability. Wide variance in methods of bone histological analysis and culture are utilized to determine the presence of residual infection. We therefore conducted a systematic, qualitative review to evaluate the current available data on objective measures to delineate the appropriate level of resection in diabetic toe and forefoot amputations, as well as the accuracy of different methods to assess for persistent infection. Methods. We performed a systematic review of studies from 1990 to 2023 performed on methods to determine margins in toe and forefoot amputations for DFO following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Data were summarized to discuss the study main objectives, methods utilized to determine amputation level, and techniques used to assess margins for persistent deep infection. Results. 568 articles were identified, and 18 articles met the final inclusion criteria after review. All studies used plain radiographs for preoperative assessment. 13 used magnetic resonance imaging (MRI) as part of their algorithm to determine general amputation level and 3 used MRI to determine exact depth of resection. 15 studies used microbiological cultures and 13 used histopathological margins intraoperatively to assess margins for deep infection. Of those, 7 studies found that those with positive margins had higher rates of treatment failure. Conclusion. Overall, majority of studies used combination of plain radiographs of MRI to determine amputation level. Patients who ultimately had positive margins correlated with longer antibiotic duration and higher rates of continued infection, impaired wound healing, reoperation, or readmission. Elucidating the optimal method of evaluating clean surgical margins is critical to lessen the burden on health care systems and improve patient care. Level of Evidence: Level III: Qualitative Review