WIfI system

Background

• Developed by the Society for Vascular Surgery to stage at-risk limbs in patients with chronic limb-threatening ischemia, including patients with and without diabetes

Criteria

Wound

Grade	DFU	Gangrene	Description
0	No ulcer	No gangrene	Minor tissue loss. Salvageable with simple digital amputation or skin coverage.
1	Small, shallow ulcer on distal leg or foot; no exposed bone, unless limited to distal phalanx	No gangrene	Minor tissue loss. Salvageable with simple digital amputation or skin coverage
2	Deeper ulcer with exposed bone, joint, or tendon; generally not involving the heel; shallow heel ulcer, without calcaneal involvement	Gangrene limited to digits	Major tissue loss salvageable with multiple digital amputation or standard TMA ± skin coverage
3	Extensive deep ulcer involving forefoot and/or midfoot; deep full thickness heel ulcer ± calcaneal involvement	Extensive gangrene involving forefoot and/or midfoot; full thickness heel necrosis ± calcaneal involvement	Extensive tissue loss salveagable only with a complex foot reconstruction or non-traditional TMA (Chopart or Lisfranc); flap coverage or complex wound management needed for large soft tissue defect

Ischemia

Grade	ABI	Ankle SBP (mmHg)	Toe pressure, TcPO2 (mmHg)
0	≥0.8	>100	≥60
1	0.6-0.79	70-100	40-59
2	0.4-0.59	50-70	30-39
3	≤0.39	<50	<30

Foot Infection

Grade	Clinical Description
0	No signs or symptoms of infection.
1	Infection present with at least 2 of: local swelling or induration; erythema 0.5 to 2 cm around the ulcer; local tenderness or pain; local warmth; purulent discharge. Local infection involving only the skin and subcutanous tissue, without involvement of deeper tissues and without systemic signs. Excludes other causes of inflammation such as trauma, gout, acute Charcot foot, fracture, thrombosis, venous stasis.
2	Local infection (as above) with erythema >2 cm around ulcer or involving deeper structures (abscess, osteomyelitis, septic arthritis, fasciitis), without systemic signs of infection.
3	Local infection (as above) with systemic signs of infection (SIRS) with at least 2 of: temperature <36ºC or >38ºC; heart rate >90 bpm; respiratory rate >20 bpm or PaCO2 <32 mmHg; WBC <4 or >12 or 10% bands

Interpretation

• Used to predict risk of amputation at 1 year, and likelihood of benefit from revascularization (assuming infection is controlled)
• Clinical stages are: very low (clinical stage 1), low (clinical stage 2), moderate (clinical stage 3), and high (clinical stage 4); clinical stage 5 refers to an unsalveageable foot

Wound	Ischemia	Foot Infection	Risk of Amputation	Benefit of Revasculatization
0	0	0	Very low	Very low
		1
		2	Low
		3	Moderate
	1	0	Very low	Very low
		1	Low	Low
		2	Moderate
		3	High	Moderate
	2	0	Low	Low
		1
		2	Moderate	Moderate
		3	High
	3	0	Low	Moderate
		1	Moderate	High
		2
		3	High
1	0	0	Very low	Very low
		1
		2	Low
		3	Moderate
	1	0	Very low	Low
		1	Low	Moderate
		2	Moderate
		3	High
	2	0	Low	Moderate
		1	Moderate	High
		2	High
		3
	3	0	Moderate	High
		1
		2	High
		3
2	0	0	Low	Very low
		1
		2	Moderate
		3	High
	1	0	Moderate	Low
		1		Moderate
		2	High	High
		3
	2	0	Moderate	High
		1	High
		2
		3
	3	0	High	High
		1
		2
		3
3	0	0	Moderate	Very low
		1
		2	High
		3
	1	0	High	Moderate
		1
		2
		3		High
	2	0	High	High
		1
		2
		3
	3	0	High	High
		1
		2
		3

Further Reading

• The Society for Vascular Surgery Lower Extremity Threatened Limb Classification System: risk stratification based on wound, ischemia, and foot infection (WIfI). J Vasc Surg. 2014;59(1):220-34.e1-2. doi: 10.1016/j.jvs.2013.08.003. PMID: 24126108.