Critical limb ischemia (CLI) was first defined in published form in 1982 (Bell et al. Br J Surg 1982;69 S2). The authors' expressed intent was that the term be only applied to patients without diabetes whose major threat to limb was chronic ischemia. CLI was defined as an ankle pressure (AP) <40 mm Hg in the presence of rest pain and <60 mm Hg in the presence of tissue necrosis.

For a disease staging system to be clinically relevant, it must achieve two primary goals:

• accurately provide risk stratification of patients with respect to disease natural history
• accurately stratify patients with sufficient granularity to allow meaningful comparison of different

There are two major problems with current classification systems:

• the validity and natural history of the concept of CLI
• the failure of most existing systems to assess and grade the major factors that influence both risk of limb loss and clinical management

The rising incidence of diabetes and diabetic foot ulcers (DFUs) as well as an increased incidence of peripheral artery disease (PAD) in patients with diabetes further mandates a reconsideration of the concept of CLI.

An adequate classification system that risk stratifies patients and aids in clinical decision-making represents an enormous unmet need in the field of chronic limb ischemia. While limb perfusion and arterial anatomy are key factors in predicting amputation risk, so too are wound depth and presence and extent of infection. The presence of neuropathy also has an important impact on risks of ulcer recurrence and amputation.