Background: Knowledge of risk factors is crucial to develop management and treatment protocols for the prevention of lower extremity amputation for patients with diabetic foot infections (DFIs).

Methods: We searched the research literature for studies reporting risk factors for lower extremity amputation in patients with DFI. The main outcome variables included both minor and major amputations. This study was reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines, and the protocol was registered in PROSPERO (CRD42018118543).

Results: A total of 2471 potential articles from the database search met the inclusion criteria. After reviewing the titles, abstracts, and full texts, remaining 25 articles were included in the final analysis. We identified 6132 patients with DFI in the 25 included articles. Of these, 1873 patients who underwent amputation were investigated. Male gender (odds ratio [OR]: 1.31), smoking (OR: 1.38), history of amputation (OR: 1.47), history of osteomyelitis (OR: 1.94), peripheral arterial disease (OR: 2.35), retinopathy (OR: 1.32), International Working Group on the Diabetic Foot (IWGDF) grades 3 and 4 (OR: 1.7 and 2.5), Wagner grades 4 and 5 (OR: 4.3 and 6.4), gangrene/necrosis (OR: 9.9), osteomyelitis (OR: 4.5), neuroischaemic DFI (OR: 3.06), severe infection (OR: 3.12), length of hospitalization (standardized mean difference [SMD]: 0.7), leukocytosis (OR: 1.76), mean erythrocyte sedimentation rate (ESR) (SMD: 0.5), mean C-reactive protein (CRP) (SMD: 0.8), tissue culture positivity (OR: 1.61), and isolation of Gram-negative bacteria from tissue culture (OR: 1.5) were found as predictors of amputation in DFI.

Conclusions: The present study highlighted some differences in diabetic foot ulcers and DFIs in terms of risk factors for lower extremity amputation. These data provide detailed information about risk factors for amputations among patients with DFI, thus contributing to the creation of new classification systems for assessment of high-risk patients.