Diabetic foot (Evaluation)
INTRODUCTION
1.
2.
Foot problems are important cause of morbidity in patients with DM. The lifetime risk of foot
ulcer for diabetic patients (type 1 or 2) may be as high as 25%. A potentially preventable
initiating event, most often minor trauma that causes cutaneous injury, can often be
identified. Foot amputations, many of which are preventable with early recognition and
therapy, may be required. These observations illustrate importance of frequent evaluation of
feet in patients with DM to identify those at risk for foot ulceration. Systematic screening
examinations for neuropathic and vascular involvement of lower extremities and careful
inspection of feet may substantially reduce morbidity from foot problems.
Evaluation of diabetic foot is provided here. A discussion of DM-related foot infections
(cellulitis and osteomyelitis) and management of diabetic foot ulcers are found elsewhere.
RISK FACTOR
1. Several risk factors are predictive of ulcers and amputation. Early recognition and
management of risk factors is important for reducing morbidity of foot ulceration. Most risk
factors are readily identifiable from Hx or PE. The most important are previous foot
ulceration, neuropathy (loss of protective sensation), foot deformity, and vascular disease.
The significance of these risk factors was confirmed by results of community-based study of
1300 T2DM patients. The incidence of lower extremity amputation was 3.8 per 1000
patient-years. Predictors of amputation were foot ulceration (HR 5.6), ABI < 0.9, elevated
HbA1C, and neuropathy.
2.
3.
Neuropathy is present in > 80% of patients with foot ulcers; it promotes ulcer formation by
decreasing pain sensation and perception of pressure, by causing muscle imbalance that can
lead to anatomic deformities, and by impairing microcirculation and integrity of skin. Once
ulcers form, healing may be delayed or difficult to achieve, particularly if infection penetrates
to deep tissues and bone and/or there is diminished local blood flow.
Risk classification
A. There is several risk classification systems designed to predict foot ulcer in patients with
diabetes. Risk categorization can be used to design preventive and monitoring strategies
(table 1). One system, developed by IWGDF, stratifies patients as follows.
i.
Group 0 - no evidence of neuropathy
ii.
Group 1 - neuropathy present but no evidence of foot deformity or peripheral
vascular disease
iii.
Group 2 - neuropathy with evidence of deformity or PAOD
iv.
Group 3 - history of foot ulceration or lower extremity amputation
B. In prospective case-control study of 225 patients with DM, stratification using this
classification system was predictive of incident ulceration and amputation. During 30
months (mean) of follow-up, ulcers occurred in 5, 14, 13, and 65% of patients in groups 0,
1, 2, and 3. Only patients in groups 2 and 3 had amputations (2 and 26%).
HISTORY
1. An abbreviated history combined with PE can usually establish presence and severity of
2.
3.
diabetic neuropathy and PAOD, 2 of the most important risk factors for developing foot ulcer.
Historical fact to ascertain include duration of DM, glycemic control, presence of micro- or
macrovascular disease, history of prior foot ulcers, lower limb bypasses or amputation,
presence of claudication, and history of smoking. Two cohort studies have demonstrated
increased risk of foot ulcers in those with longer history of DM. This may be related to finding
that risk of PAOD appears to increase with duration of T2DM. As example, in observational
study of 48,607 men, RR of PAOD in patients with T2DM compared with non-DM was 1.4 and
4.5 for 1 to 5 years and > 25 years of DM, even after controlling for other CV risk factors.
Peripheral neuropathy also increases with longer diabetes duration.
The patient should be questioned about leg discomfort. If present, further questions should
be asked that allow quantitative assessment of symptoms.
A. What is sensation felt? — Burning, numbness, or tingling (2 points); fatigue, cramping, or
aching (1 point). Maximum is 2 points.
B. What is location of symptoms? — Feet (2 points); calves (1 point); elsewhere (no points).
Maximum is 2 points.
C. Have symptoms ever awoken you at night? — Yes (1 point).
D. What is 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.
E. How are symptoms relieved? — Walking around (2 points); standing (1 point); sitting or
lying or no relief (no points). Maximum is 2 points.
4. The total symptom score can then be determined.
A. 0 to 2 — Normal
B. 3 to 4 — Mild
C. 5 to 6 — Moderate
D. 7 to 9 — Severe
PHYSICAL EXAMINATION
1. PE should include assessment for presence of existing ulcers, peripheral neuropathy, PAOD,
and foot deformities that may predispose patient to development of foot ulcers (table 2).
Several reports indicate that adequate examinations relevant to foot ulceration are often not
performed in DM patients.
A. When 1434 clinicians in the US were surveyed about how closely they were adhering to
nationally promoted and ADA endorsed recommendations for routine care, only 50% did
semiannual neurologic and foot examinations.
B. In major California HMO that provides care for 14,539 DM patients, only 6% had
documented foot examination within previous year.
2.
Physical signs of neuropathy
A. Neuropathy is present in over 80% of patients with foot ulcers; it promotes ulcer
B.
formation by decreasing pain sensation and perception of pressure by causing muscle
imbalance that can lead to anatomic deformities, and by impairing microcirculation and
integrity of skin.
PE may reveal several abnormalities that result from diabetic neuropathy, such as claw
toes and Charcot arthropathy (also called diabetic neuropathic arthropathy). Chronic
motor neuropathy often affects small intrinsic muscles of feet so that action of larger
muscles in anterior tibial compartment is unopposed. This leads to subluxation of
proximal interphalangeal-metatarsal joints, resulting in claw toe appearance. One
consequence of this abnormality is increased pressure on metatarsal heads, which are
common site of ulcer development.
C.
D.
3.
A later complication is Charcot arthropathy, which is characterized by collapse of arch of
mid-foot and abnormal bony prominences. These changes are induced by triad of small
muscle wasting, decreased sensation, and abnormal distribution of weight when
standing.
The associated autonomic neuropathy can lead to several additional problems.
Sweating is diminished or absent; as result, skin of feet remains dry and has tendency to
become scaly and cracked, thereby allowing infection to penetrate below skin. Lack of
autonomic tone in capillary circulation causes shunting of blood from arteries directly
into veins, bypassing tissues that need nutrition. This results in foot that feels warm and
has distended veins and bounding pulses. Despite these apparent signs of adequate
perfusion, foot is vulnerable to local "microvascular" gangrene, will heal very poorly and
slowly, and will be less able to resist infection.
Screening test for peripheral neuropathy
A. In clinical practice, peripheral neuropathy is most frequently assessed by determination.
i.
Vibration sensation
ii.
Pressure sensation (monofilament)
iii.
Superficial pain (pinprick) or temperature sensation
B.
The tests are designed to identify LOPS, important risk factor for ulcer formation.
Screening with simple vibration testing, monofilament examination, or superficial pain
sensation appear to have similar sensitivity and specificity for predicting diabetic
neuropathy and therefore risk of foot ulcer. One study found that failure to detect
pressure from monofilament at any of 12 places on foot was single most practical
measurement of risk assessment.
C.
Vibration sensation
i.
Vibration testing is typically conducted with 128-Hz tuning fork applied to bony
prominence at dorsum of first toe, just proximal to nail bed. The quickest method
of testing is to ask patient to report perception of both start of vibration sensation
the cessation of vibration on dampening. The test should be conducted twice on
ii.
iii.
each great toe. The sensitivity and specificity of vibration testing for peripheral
neuropathy have been estimated to be 53 and 99%.
Vibration sense can also be estimated quantitatively with Biothesiometer
(Bio-Medical Instrument Company). This device is essentially electronic tuning fork
that allows vibration to be adjusted up or down depending upon voltage applied.
The vibration-perception threshold (VPT) is defined as the lowest voltage at which
vibration can be sensed on pulp of big toe. The value in normal subjects increases
with age from approximately 6 volts at age 30 years to 20 volts at age 75 years.
In prospective trial of 469 diabetic patients with no history of foot ulceration, VPT
was found to be excellent predictor of future foot ulceration. < 4% of patients with
VPT < 25 volts developed new ulcers vs. almost 20% of those with VPT > 25 volts.
Furthermore, there was excellent correlation between VPT and severity of findings
on PE. A simpler alternative to the Biothesiometer is the graduated tuning fork,
which can also provide quantitative estimate of vibration sense.
D.
Pressure sensation
i.
Another simple device, monofilament pressure esthesiometer, permits quantitative
ii.
4.
assessment of cutaneous pressure perception threshold. The 5.07 (10-g)
monofilament is placed at right angle to skin on plantar surface of foot; pressure is
then increased until filament buckles, indicating that known amount of pressure
has been applied. The patient is asked if he or she felt pressure induced by
monofilament.
In cross-sectional study of 314 diabetic patients, those with foot ulcers had higher
pressure threshold than those without ulcers. A cutaneous pressure threshold of
4.21 U or above had sensitivity of 84%, specificity of 96%, and PPV of 76% for foot
ulceration. Prospective studies have shown that insensitivity to this monofilament
correlates with increased likelihood for developing plantar ulceration or lower
extremity amputation in future.
E. Pain and temperature sense
i.
Either pain or temperature sense can be tested; it is not necessary to evaluate both.
Physical sign of PAOD
A. The feet should be examined for signs of PAOD such as absence of foot pulse, decrease
in skin temperature, thin skin, lack of skin hair, and bluish skin color. However, these
signs are neither sensitive nor specific enough to be helpful in individual patient. More
useful tests are examination of lower limb pulses and measurement of venous filling
time. The absence of pedal pulses, presence of femoral bruits, or prolongation of venous
B.
C.
D.
filling should prompt referral for more detailed evaluation.
The venous filling time can be determined by identifying prominent pedal vein with
patient in supine position. The leg is elevated to 45º for 1 minute, leading to collapse of
vein. The patient then sits up and hangs leg over examination table; important arterial
disease is probably present if > 20 seconds elapse before vein bulges above skin.
Patients with clinical evidence of PAOD should have ABI. This index is calculated by
measuring SBP in brachial, posterior tibial, and dorsalis pedis arteries. The highest of
four measurements in ankles and feet is divided by higher of 2 brachial measurement.
The normal index is > 1.0, because pressure is higher in ankle than in arm. An index < 0.9
has 95% sensitivity for detecting angiogram-positive PAOD. We typically refer patients
with abnormal ABI to vascular specialist.
A low index in absence of foot ulcer does not correlate with risk of future foot ulceration;
however, low index in presence of foot ulcer suggests that prognosis will be improved
with reconstructive vascular surgery. In one series of patients with neuropathic foot
ulcers and severe arterial insufficiency, for example, 35 of 42 extremities (83%) with
patent bypass grafts achieved and maintained primary healing of their ulcer. A low index
also indicates more generalized arteriosclerosis and is associated with increased risk of
CV death.
5.
Foot ulceration
A. Foot ulcers are usually classified into two groups: acute ulcers secondary to dermal
abrasion from poorly fitting shoes and chronic plantar ulcers occurring over
weight-bearing areas. Chronic ulceration is probably multifactorial, due to combination
of diabetic neuropathy (with decreased pain sensation), autonomic dysfunction, and
vascular insufficiency.
B. Findings that may herald developing foot ulcer include following.
i.
Lesions between adjacent toes due to pressure from tight shoes cramming them
together
ii.
Macerated areas between toes ("athlete's foot"); these lesions are often painless
and may go unnoticed until bacterial infection supervenes
iii.
Bunions (callused areas)
C. Wound evaluation
i.
The evaluation of existing diabetic foot ulcer includes careful examination and
classification of wound. The ulcer is observed for drainage, odor, presence (or
absence) of granulation tissue, and any exposed underlying structures, such as
tendons, joint capsule, or bone. The wound can be probed gently by experienced
clinician or surgeon with sterile, blunt probe to reveal presence of sinus track or
communication with deeper structures, which may change wound classification.
D. Sign of infection
i.
The presence of diabetic foot infection is usually presumed if these conditions are
present.
1. At least two of following: erythema, warmth, tenderness, or swelling OR
2. Pus coming out of ulcer site and/or nearby sinus tract
ii.
Osteomyelitis is likely to be present if bone can be seen at floor of deep ulcer, or if
it can be easily detected by probing ulcer with sterile, blunt, stainless steel probe.
Other signs that suggest osteomyelitis are ulcer size > 2 x 2 cm and otherwise
unexplained elevation in ESR.
iii.
A discussion of diabetes-related foot infections (infected ulcer, cellulitis, and
osteomyelitis) is found elsewhere.
E. Imaging
i.
Plain radiographs can detect structural foot deformities, soft tissue gas, foreign
bodies, and may be able to detect osteomyelitis. However, radiologic changes occur
late in course of osteomyelitis and negative radiographs do not exclude it. Other
imaging techniques that have been used include radionuclide bone imaging, MRI,
and imaging with indium-labeled leukocytes.
F.
Wound classification
i.
Diabetic foot ulcers can be graded according to scheme, such as that proposed by
Wagner.
1. Grade 0 — No ulcer in high risk foot
2. Grade 1 — Superficial ulcer involving full skin thickness but not underlying
tissues
3. Grade 2 — Deep ulcer, penetrating down to ligaments and muscle, but no
bone involvement or abscess formation
4. Grade 3 — Deep ulcer with cellulitis or abscess formation, often with
osteomyelitis
5. Grade 4 — Localized gangrene
ii.
6. Grade 5 — Extensive gangrene involving whole foot
Wound classification is reviewed in more detail separately.
SCREENING FOR RISK OF FOOT ULCERATION
1. A meta-analysis of 16 case-control or cohort studies found that the following diagnostic
screening tests reliably identified those at risk for foot ulceration.
A. Peak plantar pressure (requires special equipment to identify specific areas of high
pressure under the foot)
B. Vibration perception with tuning fork or Biothesiometer
C. Cutaneous sensation with monofilament
2. PE findings of absent ankle reflexes and limited joint motion at both first
3.
metatarsal-phalangeal joint and subtalar joint also increased risk of future foot ulcers, as did
patient history of previous amputation, ulceration or lower limb bypass procedures. Other
physical examination findings, such as absence of pedal pulses and ABI, were less reliable
predictors of foot ulcers.
In another report, conventional clinical examination had low reproducibility compared with
examination using monofilament, and the latter was recommended for screening diabetic
patients for neuropathy.
4.
5.
We suggest that all patients with diabetes be screened annually to identify those at risk for
foot ulceration. We perform Hx, PE of foot, and use 5.07 U monofilament for screening
purposes. As alternative or in addition to monofilament, vibration testing, ankle reflex
assessment, or tests of pinprick sensation can be used to identify LOPS.
Preventive foot care
A. In conjunction with screening, counseling 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.
i.
Avoid smoking, walking barefoot, use of heating pads or hot water bottles, and
stepping into bath without checking the temperature.
ii.
iii.
iv.
The toenails should be trimmed to shape of toe and filed to remove sharp edges.
The feet should be inspected daily, looking between and underneath toes and at
pressure areas for skin breaks, blisters, swelling, or redness. The patient may need
to use mirror or, if vision is impaired, have someone else perform 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. A prospective study found that shoe variables other than the
recommendation for customized shoes (style, width, length, or type of shoe) had no
preventive effect. The use of customized shoes, however, reduced the development
of new foot ulcers from 58 to 28% over one year of follow-up in second report. In
third review, use of viscoelastic insole in conjunction with well-fitting shoes
(whether customized, standard "comfort" or athletic shoes) was associated with
decrease in plantar pressure; whether this results in reduced incidence of foot
ulcers remains to be determined.
v.
The feet should be washed daily in lukewarm water. Mild soap should be used and
feet should be dried by gentle patting. A moisturizing cream or lotion should then
be applied.
B. A particularly effective strategy is to make specific recommendations to the patient in
the form of "contract" and to advise patient to request that his or her feet be examined
C.
at every visit to doctor or nurse.
In addition to foot care measures described above, preliminary data suggest that home
temperature monitoring may be effective in preventing foot ulceration in very high risk
patients (for example, those with severe neuropathy and history of prior amputations or
ulcers). Temperature monitoring involves daily or twice daily measurements of skin
surface temperature with thermometer equipped with touch sensor. If temperature
difference (elevation) is detected between right and left foot site, patients are instructed
to reduce activity until temperature normalizes.
D.
6.
Whether benefit of monitoring temperature is specifically related to monitoring, or
heightened attention to foot care in those performing the monitoring, is not clear.
Additional efficacy and feasibility studies are required before home temperature
monitoring can be recommended to reduce risk of foot ulcers.
Guideline
A. Perform comprehensive foot examination annually on patients with diabetes to identify
risk factors predictive of ulcers and amputation. Perform visual inspection of feet at each
routine visit.
B. The comprehensive foot examination can be accomplished in primary care setting and
should include inspection of skin for integrity, especially between toes and under
metatarsal heads. The presence of erythema, warmth, or callus formation may indicate
C.
D.
E.
areas of tissue damage. Bony deformities, joint mobility, and gait and balance should
also be assessed.
Test for loss of protective sensation using Semmes-Weinstein 5.07 (10-g) monofilament
at specific sites to detect loss of sensation in foot, plus any one of the following:
vibration using 128-Hz tuning fork, pinprick sensation, ankle reflexes, or vibration
perception threshold with biothesiometer.
Screen for PAOD by asking about history of claudication and assessing pedal pulses.
Obtain ABI in patients > 50 and consider measurement in younger patients with multiple
risk factors for PAOD, as many patients with PAOD are asymptomatic.
Advice for prophylactic foot care should be given to all patients.
F.
Refer high risk patients (those with any positive findings from the comprehensive
examination) to foot care specialist.
SUMMARY AND RECOMMENDATIONS
1. Screening — Foot ulcers are an important cause of morbidity in patients with diabetes. Both
vascular and neurologic disease increase the risk of foot ulcers.
A. We suggest that all patients with diabetes be screened annually to identify those at risk
for foot ulceration.
B. We perform a history, comprehensive foot examination, and test for loss of protective
sensation using Semmes-Weinstein 5.07 (10-g) monofilament for screening purposes.
C. We perform ankle-brachial pressure index (ABI) testing in any patient with symptoms or
2.
physical exam findings of peripheral artery disease.
D. Counseling regarding preventive foot care should be given to any patient whose feet are
at risk for ulceration.
High risk for future ulcer — We refer patients to foot care specialist if they are at particularly
high risk for foot ulceration due to the following risk factors.
A. A previous history of foot ulceration or amputation
B. Loss of protective sensation and/or neuropathic foot deformities
C. Peripheral vascular disease