The Society for Vascular Surgery Wound, Ischemia, and foot Infection's (WIfI's) threatened limb classification system serves to comprehensively assess the severity of disease in patients with chronic limb-threatening ischemia by identifying and grading the main factors that place the threatened limb at greatest risk: wound severity, ischemic burden, and presence of infection. Each of these 3 factors is graded and the limb placed into a clinical stage, with increasing stage associated with severity of limb threat and predicted risk of major limb amputation at 1 year. Globally, there is a growing body of evidence reported from multiple institutions that has assessed amputation rates and wound-healing outcomes following revascularization in patients with WIfI clinical staging. Risk of major amputation at 1 year is low in clinical stage 1, moderate in stages 2 and 3, and high in stage 4. Higher clinical stages are associated with prolonged time to wound healing, while 1-year wound healing rates consistently decrease with increasing clinical stage. Additional avenues of investigation utilizing WIfI as an objective clinical staging tool have yielded new insights into which patients benefit from revascularization, complexity of care, hospital length of stay, quality of life, ethnic and socioeconomic disparities, as well as spurred interest in other modalities of assessing limb perfusion and their possible clinical utility. Ongoing study and refinement of WIfI grading and clinical staging will continue to improve its prognostic utility.
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