ASSESSMENT OF PATIENTS WITH DIABETIC FOOT ULCERS

Patients who present with an existing diabetic foot ulcer require holistic assessment that includes:

• Physical assessment of the wound
• Wound history
• Neuropathy assessment (discussed earlier in this course)
• Peripheral arterial disease assessment
• Ankle-brachial assessment
• Infection assessment
• Classification of the wound

One of the main goals of assessment is to identify the underlying cause of the diabetic foot ulcer and to make every effort to either correct it or remove it.

Physical Assessment of the Wound

Physical assessment begins with inspecting and comparing both feet for structural changes, pressure points, wound location, and other wound characteristics.

Structural change. Structural changes such as collapse of the arches of the foot and a rocker-bottom appearance on the plantar surface of the foot are frequently found on examination (see also “Diabetes Complications” earlier in this course).

Pressure points. Areas of increased redness may be observed in comparison to surrounding tissue.

Wound location. The location of an ulcer helps to determine the cause and the most appropriate method of relieving pressure. Diabetic ulcers can occur on any part of the foot. The most common locations are over the dorsal aspects of the toes and on the plantar surface of prominent metatarsal heads. Ulcers also frequently occur along the margins of the foot over bony prominences (Shin et al., 2020). Other sites for the development of diabetic foot ulcers are:

• Toe-webs, often the result of increased moisture, footwear that is too narrow, toe crowding, and toe deformities
• Over bunions, where there is increased pressure from shoes that do not fit correctly
• Distal ends of the toes, which indicate that there is poor arterial circulation
• Plantar surface of the mid-foot area, a common site for diabetic foot ulcers when a Charcot foot deformity is present
• Heels, often starting as deep, narrow fissures
  (Armstrong & Lavery, 2016; Abbas & Bal, 2019)

Shape. Diabetic foot ulcers are frequently round or oblong in shape.

Size. Initially, it may be hard to determine the size of the ulcer. In many cases, foot ulcers are covered with a layer of callous, and the true size cannot be determined until that is removed. The size of the wound is measured in centimeters using a plastic or paper disposable ruler. Methods for obtaining measurements include:

• Measure the longest part of the wound and the widest part of the wound perpendicular to the length.
• Use the face of a clock to represent the patient’s body and describe the wound’s orientation, with the patient’s head being at the 12 o’clock position and feet at 6 o’clock. The width of the wound is then stated as the distance from 3 o’clock to 9 o’clock.

Depth. Wound depth can range from partial thickness, where only the upper layers of the epidermis and dermis are involved, to full thickness, extending farther to deep bone structures. At initial view, the wound may appear to be a small, shallow surface wound; however, on further examination and probing of the wound, hidden depths may be found, along with sinus tracts extending down to bone. The depth of the wound is assessed by gently inserting a sterile cotton-tipped applicator into the wound until it reaches the bottom; a mark is made on the applicator parallel to the wound surface; and the applicator is then gently removed and the depth measured with a disposable centimeter ruler.

Wound base. Depending on its depth, the wound base can vary from pink to pale red for wounds that are shallow. Sometimes, it may not be possible to visualize the base of the wound, especially in the case of deep wounds that extend down to bone or where necrotic tissue is covering the base.

Undermining/tunneling. Undermining is the loss of tissue under intact skin surfaces, frequently extending a short distance from the wound. Tunneling is a tract that continues from the surface of the wound down through the underlying tissues; it is also referred to as a sinus tract. These wound characteristics can be measured and documented using the clock-face method (see above), i.e., “undermining for 2 cm from 8 o’clock to 12 o’clock, with the greatest depth of 3 cm.” Tunneling is measured by gently inserting a sterile cotton-tipped applicator to measure the depth of the wound (see above).

Wound edges. In diabetic foot ulcers the edges of the wound are usually well defined. Undermining may or may not be present. When assessing the wound edges, the clinician observes whether the wound edges are open and proliferative; such edges indicate a potential to assist with wound healing by facilitating cell migration across the wound bed, whereas edges that are closed and rolled under prevent the wound from closing. With diabetic foot ulcers, it is not unusual to find hyperkeratosis, a callus-like tissue that forms around the edges of the wound and causes them to become hard and thickened.

Periwound area. Callus formation frequently extends into the periwound area in diabetic foot ulcers. Other findings in the periwound area may be erythema, induration, and maceration, which indicate possible infection.

Exudate. Exudate (drainage) can range from small to large amounts. The amount of drainage in diabetic foot ulcers is usually small to moderate. However, where infection or other disease conditions are present, such as heart disease, renal disease, or venous insufficiency, the amount of drainage can be large. Drainage from diabetic foot ulcers is usually clear or serous. The presence of purulent drainage with a foul odor is indicative of infection.

Type of tissue present. The type of tissue found in diabetic foot ulcers can vary from pink nonviable tissue to slough and necrotic tissue. Slough is a thin, stringy, or mucous-like substance that is yellow or tan in color and either loosely or firmly attached to the wound. Necrotic tissue is dead, devitalized tissue that is black or brown in color and usually firmly attached to the wound base. It is common for diabetic foot ulcers to have more than one type of tissue present in the wound. Exposed bone is also a critical finding in a diabetic ulcer and requires immediate attention (Abbas & Bal, 2019). (See also “Osteomyelitis” later in this course.)

Wound History

Another essential step in assessing a foot ulcer is obtaining a complete history, especially if this is the first time the clinician has seen the patient. (See also “Health and Family History” earlier in this course.)

Questions at this stage include:

• How long has the ulcer been there?
• Has the patient had previous foot ulcers and in what locations?
• Is the patient aware of precipitating circumstances that led to the ulcer development?
• Is there pain associated with the ulcer?
• What tests and treatments has the patient had in the past, and what is the current status of their wound care? How successful does the patient rate the treatments received?
• What is the patient’s perception of the seriousness of the ulcer?
• How has the ulcer affected the patient’s activities (i.e., work, recreation, hobbies)? Does it affect the amount and quality of sleep? How has it impacted relationships with loved ones, friends, and coworkers?
• What are the patient’s goals for treatment? Is the patient able and willing to commit to the time and effort necessary to achieve healing?
• What support does the patient have? Who can provide help with wound care, keeping appointments, and travel, if needed? What type of health coverage does the patient have? Is the patient aware of community resources and used them in the past?
• Does the patient have coexistent health conditions?
• Is the patient taking any medications, including prescription, over-the-counter, and herbal/naturopathic substances?
• Does the patient smoke, and if so, how many cigarettes daily? Does the patient drink alcohol and how much? Use any illicit drugs?
• What other healthcare providers does the patient see, and how frequently? The clinician ensures that the patient’s diabetes care team has access to all of the patient’s records from other providers so that these can be fully reviewed. This may necessitate getting the patient’s written consent for release of records from other providers.

Infection Assessment

It has been estimated that around 59% of diabetic foot ulcers are already infected when the ulcer is first evaluated by a healthcare provider (Zubair, 2021). Another source places the number of diabetic foot infections at 56%, with around 20% of these patients developing osteomyelitis (Baranoski & Ayello, 2020).

It is essential that infection in a diabetic foot ulcer is recognized early and treated. Every patient with diabetes who presents with a foot ulcer must be thoroughly assessed for infection. This can prevent a mild infection from progressing to a more critical stage. A 24-hour delay in recognizing and treating severe infection in a diabetic foot ulcer can result in irreparable damage (Abbas & Bal, 2019).

Detecting infection in a diabetic foot ulcer can be challenging. The patient’s temperature and white blood cell count are often normal. Studies show that no more than 50% of severe infections in diabetic foot ulcers result in elevation of white blood cell count. An elevated temperature is usually an indication that the infection has spread into the deep spaces of the foot.

Patients with diabetes who have an undiagnosed ulcer infection may complain of feeling generally unwell, and there is frequently a sudden spike in blood sugar levels even though the patient has not made any changes to diet or activity level.

In patients with diabetic neuropathy, pain is often not a finding, and so the patient will not complain of pain in the wound or surrounding tissues.

The most common early presenting sign of infection in the diabetic foot ulcer is cellulitis, which is an infection of the surrounding subcutaneous tissue and skin. The area of infection will be red and hot to the touch; swelling and hardness of tissue may also be present (Abbas & Bal, 2019).

Other more subtle signs of infection are friable (disintegrates easily) granulation tissue in the wound, undermining in the wound, large amounts of wound drainage, and a malodor that persists after the wound is cleaned (WOCN, 2022).

Taking cultures from a diabetic foot ulcer to check for infection is recommended if slough and necrotic tissue remain present after the wound has been surgically debrided. All open wounds are colonized with organisms, and this colonization will intensify if devitalized tissue is present.

The technique used for obtaining cultures is important to distinguish between colonization and infection. To get the most accurate results, the culture is obtained either by biopsy from the debrided wound base or by aspirating tissue fluids. Tissue biopsy is done by removing a small piece of tissue from the ulcer base using a sterile scalpel and forceps. To obtain a fluid sample, a sterile needle is inserted into the tissues adjacent to the ulcer, and fluids are then aspirated. This procedure is done by a physician or other appropriately trained and licensed clinician (Baranoski & Ayello, 2020).

The presence of widespread inflammation and crepitus (a grating sound heard when the area adjacent to the wound bed is palpitated) are indicators of deep wound infection. Crepitus is caused by the presence of air in the subcutaneous tissues. Gangrene is another sign that is highly suggestive of a severe infection in the affected foot.

Osteomyelitis (infection in the bone) is a common finding in diabetic foot ulcers, especially in patients with moderately to severely infected diabetic ulcers. Clinical findings that suggest osteomyelitis include a diabetic foot wound >2 cm² that has been present for six months, an elevated erythrocyte sedimentation rate, elevated white blood cell (WBC) count, fever, and a positive probe-to-bone test. The recommendation from the Infectious Diseases Society of America is that a probe-to-bone test be done on any infected diabetic foot ulcer (ACR, 2019).

(See also “Osteomyelitis” and “Treating Infection” later in this course.)

Classification of Diabetic Foot Ulcers

Classification systems for diabetic foot ulcers have been developed to aid clinicians in organizing and relating assessment data regarding diabetic foot ulcers. Referring to the wound simply as a “diabetic foot ulcer” was considered too vague and did not provide concrete information from which to develop a treatment plan or determine a prognosis. Classification systems have helped to provide a consistent approach to treatment and a common language that facilitates better communication among providers. For any classification system to be meaningful, it must be used consistently by all members of the wound care team, with appropriate documentation in the patient’s records (WOCN, 2022).

Classification systems grade ulcers according to the presence and extent of several physical traits, namely, the location, size, depth, and appearance of the ulcer. The two mostly widely used are the Wagner System and the University of Texas Diabetic Foot Classification System.

WAGNER SYSTEM

The Wagner System was initially developed in the 1970s as a guideline for the level of surgical intervention. However, it is now a widely used system to determine the severity of the diabetic foot ulcer and to guide overall treatment. The Wagner System is centered on three components of the diabetic foot ulcer:

• Ulceration
• Infection
• Ischemia

It then divides the diabetic foot ulcer into six different grades, 0 to 5.

WAGNER CLASSIFICATION SYSTEM

Grade	Description
(Zubair et al., 2021)
0	No open areas, or a history of a previous healed ulcer
1	Superficial ulcer
2	Exposed deep structures such as tendon or bone
3	Abscess or osteomyelitis detected in deep tissues
4	Wet or dry gangrene present on the toes or part of the forefoot; infection present or not present
5	Gangrene encompassing the entire foot

UNIVERSITY OF TEXAS CLASSIFICATION SYSTEM

The University of Texas Diabetic Foot Ulcer Classification System uses grades and staging to classify diabetic foot ulcers. This system is seen as an improvement on the Wagner System, has been well validated, and is regarded as an accurate predictor of patient outcomes. Grades denote the depth of the wound, and staging signifies complications that impede healing, in particular infection and ischemia (WOCN, 2021). The depth grade ranges from 0 to 3 as described in the table below.

UNIVERSITY OF TEXAS CLASSIFICATION SYSTEM

Grade	Depth
(Zubair et al., 2021)
0	No open area present
1	Presence of a superficial full-thickness or partial-thickness ulcer
2	Presence of a deep wound that includes tendon or joint capsule
3	A wound that is down to bone
Stage	Infection/Ischemia
A	No infection present
B	Wound infection present, but not ischemic
C	Ischemia present, but no infection
D	Ischemia and infection both present

PEDIS SYSTEM

The PEDIS system was developed by the International Working Group on Diabetic Foot Ulcers as a user-friendly classification system for clinicians who are new to diabetic foot ulcer management. It looks at four different factors to assess the severity of the ulcer:

• Perfusion status
• Extent (size of the wound)
• Depth (amount of tissue lost)
• Infection and sensation (presence of neuropathy)
  (Abbas & Bal, 2019)