Evaluation of the diabetic foot
SUMMARY AND RECOMMENDATIONS
Foot ulcers are an important cause of morbidity in patients with diabetes. Both vascular and neurologic diseases increase the risk of foot ulcers.
-All patients with diabetes should be screened annually to identify those at risk for foot ulceration.
Perform a history, comprehensive foot examination, and test for loss of protective sensation using a 5.07 (10 g) monofilament for screening purposes.
Perform ankle-brachial pressure index (ABI) testing in any patient with symptoms or physical exam findings of peripheral artery disease.
-Counselling regarding preventive foot care should be given to any patient whose feet are at risk for ulceration.
Foot problems are an important cause of adverse health effects in patients with diabetes mellitus. The lifetime risk of a foot ulcer for diabetic patients (type 1 or 2) may be as high as 25 percent. Foot amputations, many of which are preventable with early recognition and therapy, may be needed in some patients. These observations illustrate the importance of frequent evaluation of the feet in patients with diabetes to identify those at risk for foot ulceration.
RISK FACTORS — Several risk factors are predictive of ulcers and amputation. Early recognition and management of risk factors is important for reducing morbidity of foot ulceration. The most important risk factors are previous foot ulceration, neuropathy (loss of protective sensation), foot deformity, and vascular disease.
Nerve damage (neuropathy) is present in over 80 percent of patients with foot ulcers; it promotes ulcer formation by decreasing pain sensation and perception of pressure.
An abbreviated history combined with physical examination can usually establish the presence and severity of diabetic neuropathy and peripheral artery disease. The patient should be questioned about leg discomfort. If present, further questions should be asked that allow a quantitative assessment of symptoms:
-What is the sensation felt? – Burning, numbness, or tingling (2 points); fatigue, cramping, or aching (1 point). Maximum is 2 points.
-What is the location of symptoms? – Feet (2 points); calves (1 point); elsewhere (no points). Maximum is 2 points.
-Have the symptoms ever awoken you at night? – Yes (1 point).
-What is the timing of symptoms? – Worse at night (2 points); present day and night (1 point); present only during the day (no points). Maximum is 2 points.
-How are symptoms relieved? – Walking around (2 points); standing (1 point); sitting or lying or no relief (no points). Maximum is 2 points.
The total symptom score can then be determined:
0 to 2 – Normal
3 to 4 – Mild
5 to 6 – Moderate
7 to 9 – Severe
Screening tests for peripheral neuropathy — In clinical practice, peripheral neuropathy is most frequently assessed by determination of:
-Pressure sensation (monofilament)
-Superficial pain (pinprick) or temperature sensation
Vibration sensation — Vibration testing is typically conducted with a 128 Hz tuning fork. The quickest method of testing is to ask the patient to report the perception of both the start of vibration sensation and the cessation of vibration on dampening. The test should be conducted twice on each great toe.
Pressure sensation — Another simple device, the monofilament pressure esthesiometer, permits quantitative assessment of the skin pressure perception threshold. The patient is asked if he or she felt the pressure induced by the monofilament.
Pain and temperature sense — Either pain or temperature sense can be tested; it is not necessary to evaluate both.
Physical signs of peripheral artery disease — The feet should be examined for signs of peripheral artery disease such as diminished foot pulses, decrease in skin temperature, thin skin, lack of skin hair, and bluish skin color. More useful quantitative clinical tests include measurement of venous filling time, Doppler examination of lower limb pulses, and leg blood pressure measurements (eg, ankle-brachial pressure index [ABI]). The absence of foot pulses, presence of femoral bruits, prolongation of venous filling, and reduction in ABI should prompt referral for more detailed evaluation. Patients with clinical evidence of peripheral artery disease should have ABI testing.
SCREENING FOR RISK OF FOOT ULCERATION
-Peak plantar pressure (requires special equipment to identify specific areas of high pressure under the foot)
-Vibration perception with a tuning fork or biothesiometer
-Cutaneous sensation with monofilament
It is suggested that all patients with diabetes be screened annually to identify those at risk for foot ulceration.
Preventive foot care — In conjunction with screening, counselling regarding preventive foot care should be given to any patient whose feet are at risk.
There are a series of recommendations that can markedly diminish ulcer formation; they are particularly important in patients with existing neuropathy.
-Avoid smoking, walking barefoot, the use of heating pads or hot water bottles, and stepping into a bath without checking the temperature.
-The toenails should be trimmed to the shape of the toe and filed to remove sharp edges.
-The feet should be inspected daily, looking between and underneath the toes and at pressure areas for skin breaks, blisters, swelling, or redness. The patient may need to use a mirror or, if vision is impaired, have someone else perform the examination.
-The patient’s shoes should fit properly and not be too tight, and the socks should be cotton, loose fitting, and changed every day. Patients who have misshapen feet or have had a previous foot ulcer may benefit from the use of special customized shoes.
-The feet should be washed daily in lukewarm water. Mild soap should be used and the feet should be dried by gentle patting. A moisturizing cream or lotion should then be applied.
— The guidelines from the American Diabetes Association (ADA), recommends the following with regard to foot care:
-Perform a comprehensive foot examination annually on patients with diabetes to identify risk factors predictive of ulcers and amputation.
-The comprehensive foot examination can be accomplished in the primary care setting and should include inspection of the skin for integrity, especially between the toes and under the metatarsal heads. The presence of erythema, warmth, or callus formation may indicate areas of tissue damage. Bony deformities, joint mobility, and gait and balance should also be assessed.
-Test for loss of protective sensation using a 5.07 (10 g) monofilament at specific sites to detect loss of sensation in the foot, plus any one of the following: vibration using a 128 Hz tuning fork, pinprick sensation, ankle reflexes, or vibration-perception threshold with a biothesiometer.
Screen for peripheral artery disease by asking about a history of claudication and assessing the pedal pulses. Ankle-brachial pressure index (ABI) testing should be performed in patients with clinical evidence of peripheral artery disease.
-Advice for prophylactic foot care should be given to all patients.
-Refer high-risk patients (eg, those with any positive findings from the comprehensive examination) to a foot care specialist.
-Advise specialized therapeutic footwear for patients with severe neuropathy, foot deformities, or history of amputation.