There are various ways of classifying diabetic foot ulcers (DFUs). Some guidelines refer to a staged system ranging from stage 1 — no symptoms and no risk — to stage 6, where treatment can no longer save the foot.

DFUs are a potential complication of diabetes. Prolonged high blood sugar levels can damage blood vessels and nerves, which can affect wound healing and lead to ulcers.

To help with the treatment and management of a DFU, health professionals can use a classification and scoring system. These refer to guidelines that can help to facilitate communication, treatment, and outcomes of the wound.

This article discusses the different classification systems that doctors may use to determine the severity and management of DFUs.

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DFUs are open wounds that commonly occur in the weight-bearing areas of the feet, such as the ball of the foot, heel, and tips of bent toes. Damage to blood vessels and nerves can lead to poor circulation and a loss of sensation in the feet. Nerve damage may mean that a person does not notice any injuries to their feet and therefore does not treat them. Due to poor blood flow, their body is less capable of healing and clearing infections.

Evidence suggests that approximately 5% of people living with diabetes will develop a foot ulcer. They are often responsible for more hospital admissions than other diabetic complications. It is vital to receive treatment for DFUs, as neglecting them can result in serious infections that may lead to necrosis — the death of body tissue — and gangrene. A 2021 study highlights that complications from diabetes are a leading cause of lower extremity amputation.

Learn more about diabetes and amputation.

Some guidelines may use the following stages to describe a DFU:

  • Stage 1: normal foot with no risk factors
  • Stage 2: high risk foot
  • Stage 3: ulcerated foot
  • Stage 4: cellulitic foot
  • Stage 5: necrotic foot
  • Stage 6: foot that cannot be rescued

To help manage DFUs and prevent adverse outcomes, doctors use classification and scoring systems to help guide treatment. These refer to descriptive tools that can help group individuals and determine the risk of further complications.

Health experts most commonly use the Wagner’s classification system. Other common classification systems include:

  • University of Texas classification system
  • Wound, Ischemia, and Foot Infection (WIFI) classification system
  • Site, Ischemia, Neuropathy, Bacterial Infection, Area, and Depth (SINBAD) classification system
  • International Working Group on the Diabetic Foot/Infectious Diseases Society of America (IWGDF/IDSA) classification system

Wagner’s classification system can help determine the severity of a DFU by using six different grades. It focuses on the depth of ulcer penetration, the extent of tissue necrosis, and the presence of osteomyelitis, which is infection and inflammation of the bone.

It uses a 0–5 scale for the analysis of ulcers as well as an accurate treatment option. The grades of Warner’s classification system are:

  • Grade 0: no open lesions
  • Grade 1: superficial ulcers
  • Grade 2: deeper ulcer that penetrates through the skin and ligaments
  • Grade 3: deeper ulcer with osteomyelitis or abscess
  • Grade 4: gangrene of the forefoot
  • Grade 5: gangrene of the entire foot

The University of Texas classification system focuses on the depth of the ulcer, the presence of infection, and the presence of signs of ischemia. It uses grades 0–3 to signify the severity of the ulcer. Each of these grades has four stages.

The grades of this classification system are:

  • Grade 0: healed pre- or post-ulcerative site
  • Grade 1: superficial ulcer that does not involve capsule, tendon, or bone
  • Grade 2: deep ulcer that penetrates to tendon or capsule
  • Grade 3: deep ulcer that penetrates joint or bone

The stages within each grade include:

  • Stage A: clean ulcers
  • Stage B: nonischemic but infected ulcers
  • Stage C: ischemic but noninfected ulcers
  • Stage D: ischemic and infected ulcers

The Society for Vascular Surgery developed the WIFI classification system. It uses multiple diagnostic measurements to predict the risk of amputation. WIFI uses three different grading systems to determine the extent of wound, ischemia, and infection.

The grading system for wounds includes:

  • Grade 0: no ulcer or gangrene
  • Grade 1: small and shallow ulcers on foot or distal leg but no gangrene
  • Grade 2: deep ulcer leading to the exposed joint, tendon, or bone and gangrene limited to toes
  • Grade 3: extensive ulcer and gangrene that involves midfoot, forefoot, or both

The grading system of ischemia uses the ankle-brachial index (ABI), which measures blood pressure in the ankle. The system is as follows:

  • Grade 0: ABI greater than or equal to 0.8
  • Grade 1: ABI between 0.6–0.79
  • Grade 2: ABI between 0.4–0.59
  • Grade 3: ABI less than or equal to 0.39

The grading system for infection includes:

  • Grade 0: no signs of local infection
  • Grade 1: local infection involving subcutaneous tissue and skin along with symptoms such as local swelling, less than 2 centimeters (cm) erythema around the ulcer, local pain, or local warmth
  • Grade 2: local infection involving structures that are deeper than subcutaneous tissue and skin but no signs of systemic inflammatory response
  • Grade 3: signs of systemic inflammatory response

SINBAD is a classification system that focuses on the features of ulcers, which includes area, depth, ischemia, neuropathy, and infection. The SINBAD system is a simple system that can help predict amputation as well as healing of the ulcer. The SINBAD system uses scores of 0–1 to achieve a total of 6 points. People with scores of 3 or above are at a higher risk of amputation.

The scores for the SINBAD system are as follows:

  • Site of infection:
    • 0 — forefoot
    • 1 — midfoot or hindfoot
  • Ischemia:
    • 0 — intact blood flow
    • 1 — evidence of ischemia
  • Neuropathy:
    • 0 — absent
    • 1 — present
  • Bacterial infection:
    • 0 — absent
    • 1 — present
  • Area:
    • size of ulcer less than or equal to 1 square cm — 0
    • size of ulcer greater than 1 square cm — 1
  • Depth:
    • superficial — 0
    • deep — 1

The IWGDF/ISDA classification system helps predict the need for hospitalization for people with DFUs along with the risk of amputation. The IWGDF/ISDA system comprises 4 grades that indicate the severity of DFUs.

The grades of the IWGDF/ISDA system are as follows:

  • Grade 1: no infection
  • Grade 2: superficial ulcer with mild infection
  • Grade 3: deep ulcer with gangrene, moderate infection, and involvement of bone, muscle, or tendon
  • Grade 4: deep ulcer with severe infection involving metabolic instability or systemic toxicity

Diabetic foot ulcers are a common complication of diabetes. They typically occur due to long periods of high blood sugar levels, which impact wound healing.

Several classification systems are available to help determine the severity of ulcers and guide appropriate treatment options. Early diagnosis and prompt treatment are important for better management of the condition, as well as avoiding the formation of gangrene and other potential complications.