Diabetic Foot Ulcers - Classification Systems

Last updated on 2/5/24 | First published on 11/19/17 | Literature review current through Apr. 2025 [cite]

Authors: Elaine Horibe Song MD, PhD, MBA, Samantha Kuplicki MSN, APRN-CNS, AGCNS-BC, CWS, CWCN-AP, CRNFA, Scott A. Robinson MD, Alex K. Wong MD, FACS, Topic editors: Laura Shin DPM, PhD, more...

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INTRODUCTION

This topic provides details on the most used classification systems for Diabetic Foot Ulcer (DFU): Wagner [1][2], University of Texas [3], Infection classification by the Infectious Diseases Society of America (IDSA) [4] and the newer classification by the Society for Vascular Surgery Lower Extremity Threatened Limb Wound/Ischemia/Foot Infection (WIfI) [5]. For relevance of classification systems in DFU assessment, please refer to Diabetic Foot Ulcer - Introduction and Assessment, section 'Diabetic Foot Ulcer and Infection Classification Systems'

Classification systems that do not stratify severity of infection

Wagner [2]: Well established, however it does not fully address infection and ischemia. Hyperbaric oxygen therapy (HBO) practitioners in the United States are still required to refer to the Wagner system when deciding whether patients with DFU are candidates for HBO, as one of the criteria for Medicare coverage of this condition is that the DFU be classified as Wagner 3 or higher.[6] (See HBO criteria and protocol for Diabetic Foot Ulcer - Hyperbaric Oxygen Therapy)
University of Texas (UT) [3]: the most commonly used classification system in wound clinics in the United States.[7] The UT system is based on the Wagner classification system, and describes the presence of infection and ischemia better than Wagner. Despite its widespread use, it does not reference either neuropathy or ulcer area, which is considered to be one of the main determinants of time to healing.[8]

Classification systems that stratify severity of infection

Infectious Diseases Society of America (IDSA) [4]: for people with diabetes with suspected foot infections, with or without ulcers.[8] Does not include other elements such as ulcer, ischemic rest pain, ischemia or gangrene. The IDSA classification of diabetic foot infection was incorporated into the WIfI system, which includes these other elements and are more suited for patients with diabetic foot ulcers.
The Society for Vascular Surgery Lower Extremity Threatened Limb Wound/Ischemia/Foot Infection (WIfI) [5]: for assessing perfusion and any likely benefit of revascularization.[8] This relatively new, validated risk stratification tool is based on three major factors that impact amputation risk and clinical management for DFU: Wound, Ischemia, and foot Infection (WIfI). WIfI incorporates the IDSA infection grading, wound depth and vascular status for predictive outcomes. The WIfI classification has been shown to predict many types of DFU outcomes (e.g. extent of healing, time to heal, lower extremity amputation occurrence, need for revascularization, maintenance of ambulatory and independent living status, costs, and mortality).[8]

Linking DFU classifications with ICD-10

The DFU classification systems do not provide some of the details needed by medical coders for billing purposes. For instance, coders need to know the severity of tissue damage as described by the ICD-10. As a result, ulcer depth needs to be documented as: "limited to breakdown of skin", "with fat layer exposed", "with necrosis of muscle", etc. Otherwise the severity might be classified as “unspecified”, which will delay claim processing and reimbursement.[9]

The American Medical Association (AMA) recommends that ulcers such as DFU be properly documented for adequate code (ICD-10) assignment. That means that in addition to classifying the ulcer with one of the DFU classification systems, clinicians should clearly describe etiology, anatomical location with laterality and severity of tissue damage in a way that coders can easily match descriptions of existing ICD-10 codes to the medical record.

Tables 1A, 1B and 2 below correlate the Wagner and UT classification systems with the specific terminology medical coders need in order to correctly code the encounter.

 Quick Reference Tool: Wagner Classification

WAGNER CLASSIFICATION

Table 1A. Wagner Classification for Diabetic Foot Ulcers [1][2][10] and terms for proper documentation on Medical Records

Image	Wagner Grade and description	Medical Records Documentation to facilitate ICD-10 coding
	The GRADE 0 foot has intact skin. It has been found that this is the greatest protection to the diabetic foot. There may be bony deformities such as bunions, claw toes, depressed metatarsal heads and Charcot breakdown with bony prominences. There may be hyperkeratotic lesions around or under bony deformities	Conditions: Type 1, Type 2 or other type of diabetes (specify) peripheral neuropathy peripheral angiopathy neuropathic arthropathy
	The Grade 1 foot has a superficial ulcer without penetration to deeper layers. The base may be necrotic or may be viable with early granulation tissue	Conditions: Type 1, Type 2 or other type of diabetes (specify) Diabetic Foot Ulcer Ulcer location in foot: left or right foot heel or midfoot other part of the foot (specify) Ulcer depth: limited to breakdown of skin with fat layer exposed
	The Grade 2 foot has a lesion that is deeper and extends to the bone, ligament, tendon, joint capsule or deep fascia. There is yet no abscess or osteomyelitis	Conditions: Type 1, Type 2 or other type of diabetes (specify) Diabetic Foot Ulcer Ulcer location in foot: left or right foot heel or midfoot other part of the foot (specify) Ulcer depth: with necrosis of muscle with muscle involvement without evidence of necrosis
	The Grade 3 foot has ulcer with deep abscess, osteitis or osteomyelitis, pyarthrosis, plantar space abscess, or infection of the tendon and tendon sheaths. The exact extent of the lesion is frequently difficult to determine from superficial examination (*)	Conditions: Type 1, Type 2 or other type of diabetes (specify) Diabetic Foot Ulcer Ulcer location in foot: left or right foot heel or midfoot other part of the foot (specify) Ulcer depth: with necrosis of muscle with muscle involvement without evidence of necrosis with necrosis of bone with bone involvement without evidence of necrosis Type of infection: cellulitis abscess osteomyelitis
	The Grade 4 foot has some portion of the toes or forefoot that is gangrenous. Gangrene may be moist or dry	Conditions: Diabetic peripheral angiopathy with gangrene Diabetic Foot Ulcer Ulcer location in foot: left or right foot heel or midfoot other part of the foot (specify) Ulcer depth: with necrosis of bone
	A Grade 5 foot represents such complete involvement of gangrene that no foot healing or local procedure are possible. Amputation of the gangrenous area is indicated.	Conditions: Diabetic peripheral angiopathy with gangrene Diabetic Foot Ulcer Ulcer location in foot: left or right foot heel or midfoot and other part of the foot. Entire foot Ulcer depth: with necrosis of bone

Among other requirements listed on Medicare determinations, a diabetic foot ulcer needs to be classified as Wagner 3 or above to justify treatment with hyperbaric oxygen therapy. For details, refer to section 'Wagner Classification' in topic " Diabetic Foot Ulcer - Hyperbaric Oxygen Therapy".
Diabetic foot infections may not display classic signs of soft tissue infection and nevertheless may have underlying osteomyelitis. Probe-to-bone test, serum inflammatory markers, imaging tests (e.g., X-rays, MRI) or bone biopsy are usually needed for diagnosis of osteomyelitis. For more on diagnosis of soft tissue infection and osteomyelitis refer to "Diabetic Foot Ulcer - Introduction and Assessment".

Quick Reference Tool

See the 'Quick Reference Tool: Diabetic Foot Ulcer - Wagner Classification System' below (Table 1B)

Table 1B. Quick Reference Tool: Diabetic Foot Ulcer - Wagner Classification System

UNIVERSITY OF TEXAS CLASSIFICATION

Table 2. University of Texas Classification for Diabetic Foot Ulcers [3] and terms for proper documentation on Medical Records

Grade/

Stage

Grade 0

Grade 1

Grade 2

Grade 3

Medical Records Documentation to facilitate ICD-10 coding

Pre- or postulcerative, completely epithelialized

Superficial ulcer (partial or full thickness) not involving tendon, capsule, or bone

Tendon or capsular involvement without palpable bone

Ulcer probes to bone

Type 1, Type 2 or other type of diabetes (specify)

With infection

cellulitis
abscess
osteomyelitis
location (foot, toe, left or right)

With ischemia

diabetic peripheral angiopathy with or without gangrene

With infection and ischemia

See B and C above

Conditions:

peripheral neuropathy
neuropathic arthropathy

Conditions:

Diabetic Foot Ulcer

Ulcer location in foot:

left or right foot
heel or midfoot
other part of the foot (specify)

Ulcer depth:

limited to breakdown of skin
with fat layer exposed

Conditions:

Diabetic Foot Ulcer

Ulcer location in foot:

left or right foot
heel or midfoot
other part of the foot (specify)

Ulcer depth:

with necrosis of muscle
with muscle involvement without evidence of necrosis

Conditions:

Diabetic Foot Ulcer

Ulcer location in foot:

left or right foot
heel or midfoot
other part of the foot (specify)

Ulcer depth:

with necrosis of bone
with bone involvement without evidence of necrosis

* Medical Records Documentation

INFECTIOUS DISEASES SOCIETY OF AMERICA (IDSA) CLASSIFICATION

Table 3. Classification of severity of diabetic foot infections, by the Infectious Diseases Society of America (IDSA) [4]

CLINICAL CRITERIA	GRADE/SEVERITY
No clinical signs of infection	Grade 1/ uninfected
Local infection (skin and/or subcutaneous tissue), with at least two of the items below: Local swelling or induration Erythema > 0.5 cm and ≤2 cm around the ulcer. Excluded other causes of an inflammatory response of the skin (eg, trauma, gout, acute Charcot neuro-osteoarthropathy, fracture, thrombosis, venous stasis)around the wound Local tenderness or pain Local warmth Purulent discharge	Grade 2/ mild
Local infection (as described above) with erythema > 2 cm, or involving structures deeper than skin and subcutaneous tissues (eg, abscess, osteomyelitis, septic arthritis, fasciitis), and no systemic inflammatory response signs (as described below)	Grade 3/ moderate
Local infection (as described above) with the signs of systemic inflammatory response syndrome, as manifested by ≥2 of the following: Temperature > 38 °C or < 36 °C Heart rate > 90 beats/min Respiratory rate > 20 breaths/min or PaCO2 < 4.3 kPa (32 mmHg) White blood cell count > 12 000/mm3 or < 4000/mm3, or > 10% immature (band) forms	Grade 4/ severe

THE SOCIETY FOR VASCULAR SURGERY LOWER EXTREMITY THREATENED LIMB WOUND/ISCHEMIA/FOOT INFECTION (WIfI)

Table 4. The WIfI Classification System [5]: a) W=Wound, b) I=Ischemia, c) fI=Infection

Table 4.a W=Wound

GRADE	ULCER	GANGRENE	CLINICAL DESCRIPTION
0	No ulcer	No gangrene	Ischemic rest pain (requires typical symptoms of ischemia grade 3); no wound.
1	Mild: Small, shallow ulcer(s) on distal leg or foot; no exposed bone, unless limited to distal phalanx	No gangrene	Minor tissue loss. Salvageable with simple digital amputation (1 or 2 digits) or skin coverage
2	Moderate: Deeper ulcer with exposed bone, joint or tendon; generally not involving the heel; shallow heel ulcer, without calcaneal involvement	Gangrenous changes limited to digits	Major tissue loss salvageable with multiple (more than 3) digital amputations or standard TMA +/- skin coverage
3	Severe: 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 salvageable only with a complex foot reconstruction or nontraditional TMA (Chopart or Lisfranc); flap coverage or complex wound management needed for large soft tissue defect

TMA: transmetatarsal amputation

Table 4.b: I=Ischemia

GRADE	ABI	ANKLE SYSTOLIC PRESSURE	TP, TcPO2
0	> or =0.80	>100 mmHg	> or =60 mm Hg
1	0.6-0.79	70-100 mmHg	40-59 mmHg
2	0.4-0.59	50-70 mmHg	30-39 mmHg
3	< or =0.39	<50 mmHg	<30 mmHg

ABI, Ankle-brachial index; PVR, pulse volume recording; SPP, skin perfusion pressure; TP, toe pressure; TcPO2, transcutaneous oximetry.

Hemodynamics/perfusion: Measure TP or TcPO2 if ABI incompressible (>1.3). Patients with diabetes should have TP measurements. If arterial calcification precludes reliable ABI or TP measurements, ischemia should be documented by TcPO2, SPP, or PVR. If TP and ABI measurements result in different grades, TP will be the primary determinant of ischemia grade. Flat or minimally pulsatile forefoot PVR = grade 3.

Table 4.c. fI=Foot Infection

CLINICAL MANIFESTATION OF INFECTION	SVS WIfi	IDSA/PEDIS infection severity
No symptoms or signs of infection Local infection is defined by the presence of at least 2 of the following items: Local swelling or induration Erythema >0.5 to < or=2 cm around the ulcer Local tenderness or pain Local warmth Purulent discharge (thick, opaque to white, or sanguineous secretion)	0	Uninfected
Local infection involving only the skin and the subcutaneous tissue (without involvement of deeper tissues and without systemic signs as described below). Exclude other causes of an inflammatory response of the skin (eg, trauma, gout, acute Charcot neuro-osteoarthropathy, fracture, thrombosis, venous stasis)	1	Mild
Local infection (as described above) with erythema >2 cm, or involving structures deeper than skin and subcutaneous tissues (eg, abscess, osteomyelitis, septic arthritis, fasciitis), and No systemic inflammatory response signs (as described below)	2	Moderate
Local infection (as described above) with the signs of systemic inflammatory response syndrome, as manifested by ≥2 of the following: Temperature > 38 °C or < 36 °C Heart rate > 90 beats/min Respiratory rate > 20 breaths/min or PaCO2 < 4.3 kPa (32 mmHg) White blood cell count > 12 000/mm3 or < 4000/mm3,or > 10% immature (band) forms	3	Severe

PaCO2, Partial pressure of arterial carbon dioxide; SIRS, systemic inflammatory response syndrome.

Ischemia may complicate and increase the severity of any infection. Systemic infection may sometimes manifest with other clinical findings, such as hypotension, confusion, vomiting, or evidence of metabolic disturbances, such as acidosis, severe hyperglycemia, new-onset azotemia. From Lipsky et al. [4]

Key summary points for use of Society for Vascular Surgery Lower Extremity Threatened Limb (SVS WIfI) classification system

The full system above is to be used for initial, baseline classification of all patients with ischemic rest pain or wounds within the spectrum of chronic lower limb ischemia when reporting outcomes, regardless of form of therapy. The system is not to be employed for patients with vasospastic and collagen vascular disease, vasculitis, Buerger’s disease, acute limb ischemia, or acute trauma (mangled extremity)
Patients with and without diabetes mellitus should be differentiated into separate categories for subsequent outcomes analysis.
- Presence or absence of neuropathy should be noted when possible in patients with diabetes in long-term studies of wound healing, ulcer recurrence, and amputation, since the presence of neuropathy (loss of protective sensation and motor neuropathic deformity) influences recurrence rate
In the Wound (W) classification, depth takes priority over size. Although WIfI recommends that a wound, if present, be measured, a shallow, 8-cm2 ulcer with no exposed tendon or bone would be classified as grade 1
Toe pressures (TPs) are preferred for classification of ischemia (I) in patients with diabetes mellitus, since ABI is often falsely elevated. TcPO2, SPP, and flat forefoot PVRs are also acceptable alternatives if TP is unavailable. All reports of outcomes with or without revascularization therapy require measurement and classification of baseline perfusion.
In reporting the outcomes of revascularization procedures, patients should be restaged after control of infection, if present, and/or after any debridement, if performed, prior to revascularization
- Group a patients: no infection within 30 days, or simple infection controlled with antibiotics alone
- Group b patients: had infection that required incision and drainage or debridement/partial amputation to control

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