Diabetic foot ulcer evaluation: how a foot wound is assessed

A diabetic foot ulcer evaluation is the first step toward healing. Dr. Efe Ozturk, a Foot and Ankle Surgeon who is board certified in wound care (FAPWH), examines the wound, the whole foot and leg, and your general health, because what caused a wound often keeps it from healing.

Why the whole foot is examined

Most foot ulcers in people with diabetes form when nerve damage, narrowed arteries or both meet a trigger, such as a rubbing shoe or a bony spot under too much pressure.⁠^[1] About half of people with diabetes and a foot ulcer also have peripheral artery disease.⁠^[6]

We ask how the wound began, what has been tried, and about earlier ulcers, your diabetes, kidneys, smoking and medicines. Kidney disease, swelling, poor nutrition, high blood sugar and frailty can all affect healing, so they are weighed alongside the wound.⁠^[1]

We check the feeling in your feet with a thin nylon filament (the 10-gram monofilament) and a tuning fork.⁠^[1] Whatever caused an ulcer, walking on a numb foot slows healing.⁠^[1] The Nerve Institute explains peripheral neuropathy (external site).

We also look at the shape of your foot lying down and standing, how you walk, and your shoes. Deformities and bony prominences can lead to an ulcer, and ill-fitting shoes or walking barefoot often do, so naming the trigger matters for this wound and the next.⁠^[1] See ulcers caused by foot deformity.

Measuring the wound

We measure the wound’s area in square centimeters and record whether it reaches only the skin and fat, muscle or tendon, or bone.⁠^[1] Callus and dead tissue can hide the true depth, so they are trimmed away early, unless the wound is uninfected and blood flow is severely reduced.⁠^[1]

In a study of more than 31,000 people with diabetes and nerve-related foot ulcers, the wound’s size, how long it had been open and its grade were each linked to whether it healed within 20 weeks.⁠^[7] Because we re-measure at every visit, a wound that stops shrinking is noticed early. See wound care visits.

The probe-to-bone test

A sterile, blunt metal probe is gently slid into the wound. Feeling hard, gritty bone is a positive test. It is simple and essentially harmless, and the guideline calls it the most useful part of the foot examination for bone infection.⁠^[4]

In a study following 1,666 people with diabetes, 12% of those who developed a foot wound had bone infection; a negative probe test was correct 98% of the time, a positive one only 57%.⁠^[2] So a negative test is reassuring in a lower-risk wound, a positive test in a high-risk wound points toward bone infection, and the guideline suggests pairing it with X-rays and blood tests.⁠^[4]

Swipe sideways to see the whole drawing.

Is the wound infected?

Infection is diagnosed by examining the foot for at least two signs of inflammation, such as swelling, warmth, redness, tenderness or pus.⁠^[1] Nerve damage and poor circulation can blunt these signs, and fever is often missing in mild and moderate infections.⁠^[1] Blood tests for inflammation help when the exam is unclear, and infections are graded mild, moderate or severe.⁠^[4] See diabetic foot infections and a red, hot, swollen foot.

Every open wound carries germs, so bacteria on a culture don’t by themselves mean infection, and the guideline advises against antibiotics for an uninfected ulcer.⁠^[4] When a wound looks infected, it prefers a small piece of tissue scraped or snipped from the cleaned wound base over a surface swab, which is less accurate.⁠^[4] We choose antibiotics based on culture results.

X-rays, MRI and bone samples

X-rays, taken at our practice, show bone damage, gas deep in the tissues and some foreign objects.⁠^[4] X-rays can miss bone infection: in a pooled analysis of studies in people with diabetic foot ulcers, plain X-rays detected about 54% of bone infections and MRI about 90%.⁠^[3] When suspicion stays high, a normal X-ray is often repeated in 2–3 weeks.⁠^[4]

MRI is recommended when bone infection is still uncertain after the exam, X-rays and blood tests. It also shows how far infection reaches and whether pus has collected, which helps plan surgery.⁠^[4] We arrange MRI at an outside imaging center. On MRI, swelling inside the bone from an injury, earlier foot surgery or Charcot foot can look like infection.⁠^[4] The Center for Lower Extremity Surgery has a general guide to foot and ankle imaging (external site).

A sample of the bone itself is the accepted standard for diagnosing bone infection and the only definitive way to name the germ; in most studies, wound and bone cultures agree less than half the time.⁠^[4] Dr. Ozturk performs bone biopsy when a bone sample is needed. See bone infection of the foot.

Checking blood flow

In diabetes, feeling for pulses is not accurate enough on its own, so every foot ulcer calls for objective testing.⁠^[1] Nerve damage can also hide the usual warning pain of poor circulation.⁠^[6] For a foot ulcer in diabetes, guidelines recommend Doppler waveforms together with ankle and toe pressure indexes, because no single test is ideal and no reading fully rules artery disease out.⁠^[6] We start with noninvasive circulation testing at our practice and arrange detailed imaging with a vascular specialist when flow is reduced. See circulation tests for foot wounds.

If your foot hurts at night or a toe is turning dark, read about foot pain at night and dark or discolored toes.

How the findings are graded

Your records may include shorthand. The IWGDF recommends SINBAD (Site, Ischemia, Neuropathy, Bacterial infection, Area and Depth) to describe an ulcer and the IWGDF/IDSA grades for infection, and suggests WIfI (Wound, Ischemia and foot Infection) when artery disease is present.⁠^[1,8] WIfI reflects the idea that blood flow is only one part of the threat to a limb.⁠^[9] A Wagner grade may also appear; it is the most often tested system, but studies mainly checked its link with amputation.⁠^[10]

These systems give clinicians a common language, but none is recommended for predicting how one person’s ulcer will turn out.⁠^[8]

When the findings point to surgery

For some wounds, the evaluation shows that an operation is what will let them heal. For a deep or spreading infection, the guideline calls for urgent assessment for surgery to drain pus and remove dead tissue, including infected bone.⁠^[1] When a person with diabetes has a nerve-related ulcer under the ball of the foot that offloading hasn’t healed, the IWGDF suggests considering Achilles tendon lengthening or removing the metatarsal head, along with an offloading device. For an ulcer on the tip or underside of a flexible bent smaller toe, it recommends a small tendon release.⁠^[5]

For the wounds that need it, Dr. Ozturk drains infection, removes infected bone, lengthens a tight tendon or removes a bony prominence, choosing the smallest operation that will do the job. When blood flow is reduced, we coordinate timing with a vascular specialist (see restoring blood flow). Read about surgery for diabetic foot infection, surgery for bone infection and surgery that takes pressure off ulcers.

Limits of the tests

No single test settles every question. The probe test’s accuracy can vary with the examiner’s technique and experience, and a bone culture can be falsely negative, especially after recent antibiotics.⁠^[4] So results are read together, and an unclear answer may mean repeating a test. If you’ve been told your foot can’t be saved, a limb salvage second opinion starts with this same evaluation.

When to seek care

See us within a day or two for any foot wound that isn’t healing, especially if you have diabetes. We see foot wounds at all three offices: Lyndhurst, Paramus and Millburn. Bring your shoes, your medicine list, and any recent imaging reports or culture results. To book, call 908-215-5953 or use Zocdoc.