Society for Vascular Surgery WIfI (wound, ischemia, foot infection) classification

Usage of Classification System:

The table below is employed for the initial assessment of patients experiencing ischemic rest pain or wounds associated with chronic lower limb ischemia, especially when reporting treatment outcomes. This classification should not be applied to patients with specific conditions like vasospastic or collagen vascular disease, vasculitis, Buerger’s disease, acute limb ischemia, or acute trauma.

Distinguishing Diabetes Mellitus:

It’s important to differentiate patients with and without diabetes for subsequent outcomes analysis. Additionally, in long-term studies focused on wound healing, ulcer recurrence, and amputation, noting the presence of neuropathy (loss of protective sensation and motor neuropathic deformity) in diabetic patients is crucial, as it significantly affects recurrence rates.

Wound Classification Emphasis:

The priority in the Wound (W) classification lies in assessing depth rather than size. For example, a superficial ulcer covering an area of 10-cm² without any exposed tendons or bones would be categorized as grade 1. Size categories (small, medium, large) could also be considered.

Preferred Method for Ischemia Classification:

When classifying ischemia (I) in diabetic patients, Toe Pressures (TP) are recommended over Ankle-Brachial Index (ABI), as ABI readings can often be inaccurately elevated. If TP measurements are unavailable, alternatives such as Transcutaneous Oxygen Tension (TcPO2), Skin Perfusion Pressure (SPP), or flat forefoot Pulse Volume Recordings (PVRs) are acceptable. Regardless of the method chosen, it’s essential to measure and classify baseline perfusion in all outcome reports, regardless of whether revascularization therapy is involved.

Outcome Reporting after Revascularization:

When reporting the results of revascularization procedures, patients should be reevaluated after successfully controlling any existing infections, if applicable. Similarly, if debridement was performed before revascularization, patients should be restaged.

Component	0 (None)	1 (Mild)	2 (Moderate)	3 (Severe)
Wound (W)
Ulcer	No ulcer	Small, shallow ulcer on distal leg or foot; no exposed bone, unless limited to distal phalanx	Deeper ulcer with exposed bone, joint, or tendon; generally not involving the heel; shallow heel ulcer, without calcaneal involvement	Extensive, deep ulcer involving forefoot and/or midfoot; deep, full-thickness heel ulcer without calcaneal involvement
Gangrene	No gangrene	No gangrene	Gangrenous changes limited to digits	Extensive gangrene involving the forefoot/midfoot; full-thickness heel necrosis without calcaneal involvement
Ischemia (I)
ABI (Ankle-brachial index)	≥ 0.80	0.6-0.79	0.4-0.59	≤ 0.39
Ankle systolic pressure	>100mmHg	70-100mmHg	50-70mmHg	<50mmHg
TP(toe pressure),TcPO2 (transcutaneous oximetry)	≥ 60mmHg	40-59mmHg	30-39mmHg	<30mmHg
foot Infection (fI)
	No symptoms or signs of infection Infection present, (at least two of the following): - Local swelling or induration - Erythema 0.5–2 cm around the ulcer - Local tenderness or pain - Local warmth - Purulent discharge (thick, opaque to white, or sanguineous secretion)	Local infection involving only the skin and the subcutaneous tissue Exclude other causes of an inflammatory response of the skin (trauma, gout, acute Charcot, fracture, thrombosis, venous stasis)	Local infection (grade 1) with erythema >2 cm, or involving structures deeper than skin and subcutaneous tissues (e.g, abscess, osteomyelitis, septic arthritis, fasciitis), and No systemic inflammatory response signs (described in grade 3)	Local infection with the signs of SIRS,(two or more of the following): - Temperature > 38 or < 36°C - Heart rate > 90 beats/min - Respiratory rate > 20 breaths/min or PaCO2 < 32 mm Hg - White blood cell count > 12,000 or < 4,000 cu/mm or 10% immature bands

ABI, ankle brachial index; PaCO2, partial pressure of carbon dioxide; SIRS, systemic inflammatory response syndrome; TcPO2, transcutaneous oximetry; TP, toe pressure.
Notes: Patient’s symptoms are graded by three categories: foot wound severity, tissue perfusion by ABI or transcutaneous oximetry, and the presence of infection.

Estimate risk of amputation at 1 year for each combination:

	Ischemia – 0				Ischemia – 1				Ischemia – 2				Ischemia – 3
W-0	VL	VL	L	M	VL	L	M	H	L	L	M	H	L	M	M	H
W-1	VL	VL	L	M	VL	L	M	H	L	M	H	H	M	M	H	H
W-2	L	L	M	H	M	M	H	H	M	H	H	H	H	H	H	H
W-3	M	M	H	H	H	H	H	H	H	H	H	H	H	H	H	H
	fI0	fI1	fI2	fI3	fI0	fI1	fI2	fI3	fI0	fI1	fI2	fI3	fI0	fI1	fI2	fI3

VL - Very Low
L - Low
M - Moderate
H - HIgh

Estimate likelihood of benefit of/requirement for revascularization (assuming infection can be controlled first) :

	Ischemia – 0				Ischemia – 1				Ischemia – 2				Ischemia – 3
W-0	VL	VL	VL	VL	VL	L	L	M	L	L	M	M	M	H	H	H
W-1	VL	VL	VL	VL	L	M	M	M	M	H	H	H	H	H	H	H
W-2	VL	VL	VL	VL	M	M	H	H	H	H	H	H	H	H	H	H
W-3	VL	VL	VL	VL	M	M	M	H	H	H	H	H	H	H	H	H
	fI0	fI1	fI2	fI3	fI0	fI1	fI2	fI3	fI0	fI1	fI2	fI3	fI0	fI1	fI2	fI3

VL - Very Low
L - Low
M - Moderate
H - HIgh

The risk of amputation rises with an increase in wound class, as indicated by various wound classification systems including PEDIS and UT.
Peripheral Arterial Disease (PAD) and infection together have a synergistic effect, as observed in the Eurodiale study. When a wound is both infected and affected by PAD, the likelihood of requiring revascularization for wound healing significantly increases.
In the Infection 3 category, characterized by systemic or metabolic instability, there is a moderate to high risk of amputation, irrespective of other contributing factors. This aligns with validated guidelines from the Infectious Diseases Society of America (IDSA).

References

Mills, Joseph L Sr et al. “The Society for Vascular Surgery Lower Extremity Threatened Limb Classification System: risk stratification based on wound, ischemia, and foot infection (WIfI).” Journal of vascular surgery vol. 59,1 (2014): 220-34.e1-2. doi:10.1016/j.jvs.2013.08.003