DIABETIC FOOT ULCERATION
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| LESIONS OF THE DIABETIC FOOT |
Patients with diabetes are susceptible to a host of foot-related problems. One of the most common and troublesome problems is ulceration and subsequent infection of the foot. Ulceration of the foot develops in the diabetic patient primarily as a result of peripheral neuropathy and loss of the normal protective sensation. Whereas the individual with normal protective sensation would immediately sense minor trauma such as the rubbing of a shoe and take immediate steps to correct it, the diabetic individual is not aware of the problem, allowing the pressure to continue unabated. Eventually, even minor repetitive trauma can result in formation of an ulcer. Ulcers occur most commonly on the weight-bearing plantar surface of the foot and over bony prominences. Once ulceration develops, it is also more likely to become infected in the diabetic patient owing to diminished immune function and impaired circulation. Failure to sense the normal signs of infection due to neuropathy can result in progression to osteomyelitis and extensive, limb-threatening infection in the diabetic patient.
Classification. Diabetic ulcerations are best characterized by evaluating the lesion’s
depth and the vascularity of the foot. Wagner popularized a classification of
diabetic foot ulcers that included six categories. Grade 0 refers to a pressure
area that has not yet ulcerated. Grade 1 describes superficial, noninfected
ulcers. Grade II describes deep, noninfected ulcers, commonly with involved
tendon. Grade III describes deep, infected ulcers usually with osteomyelitis.
Grades IV and V refer to the vascularity of the foot, with partial gangrene
included as grade IV and complete gangrene as grade V.
Physical Examination. After assessing and classifying the depth and
tissue involvement of the diabetic foot ulceration, the patient must be evaluated
as a whole to determine the ulcer’s healing potential. The ability to heal a
diabetic foot ulcer is directly affected by the patient’s vascular and
nutritional status. Vascular assessment begins by recording the color and
temperature of the feet and palpating for dorsalis pedis and posterior tibial
pulses. If the pulses are absent or significantly diminished, formal evaluation
by a vascular medicine specialist is indicated. This formal vascular evaluation
often includes measurement of the ankle-brachial index (ABI) and transcutaneous
oxygen saturation. The ABI assesses the blood pressure in the foot relative to
the blood pressure in the arm. An ABI value less than 0.45 has been associated
with decreased ability to heal a diabetic foot ulcer. Similarly, transcutaneous
oxygen saturation reflects how well oxygenated the blood is that perfuses the
foot. Transcutaneous oxygen pressures less than 30 mm Hg have also been
associated with decreased healing potential.
Diabetic patients, although
frequently overweight, may paradoxically be malnourished. Malnourishment can
impair the diabetic patient’s ability to heal foot ulceration. Nutritional
status can be assesses through simple blood tests such as measuring the
patient’s albumin level and total lymphocyte count. A serum albumin level less
than 3.0 g/dL or a total lymphocyte count less than 1500 cells/mm3
suggest poor nutrition that may complicate healing of an ulcer.
Treatment. A successful treatment plan for diabetic foot ulceration must address all
of the contributing factors in a comprehensive manner. If vascular supply is
suboptimal, peripheral arterial stenting or bypass procedures may be indicated
to improve blood supply to the foot. A vascular surgeon is needed to determine
if this is feasible and appropriate. Poor nutrition can be aggressively
addressed by correcting dietary errors and augmenting with protein supplements.
Blood glucose control should also be optimized because this improves healing
and decreases the risk of infection. Ulcerations associated with infection must
be aggressively debrided of all involved tissue, and appropriate antibiotic
therapy is then instituted.
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| CLINICAL EVALUATION OF PATIENT WITH DIABETIC FOOT LESION |
Most diabetic foot ulcerations
develop as a result of abnormal pressure applied to the insensate foot. Thus,
the most critical part of treatment is removing the abnormal pressure. For
plantar foot ulcerations, this often requires use of a total contact cast. A
total contact cast is an intimately fitting cast applied to the leg and foot
that distributes the load of weight bearing across the entire bottom of the
cast, effectively unloading the area of ulceration. A good total contact cast
allows the diabetic patient to remain mobile while the ulcer heals, usually in
6 to 8 weeks. Forefoot ulceration is often accompanied by tightness of the
Achilles tendon, which is thought to increase pressure beneath the metatarsal
heads, contributing to ulceration. Percutaneous lengthening of the Achilles
tendon concomitantly with total contact casting has been demonstrated to
decrease the likelihood of ulcer recurrence.
Once the ulcer has healed,
casting can be discontinued and the patient transitioned into proper diabetic footwear.
Good diabetic shoes should be wide and deep to accommodate the foot and
decrease the risk of friction and subsequent ulceration. Patients with
deformities or bone prominences may require custom shoes or custom orthotic
inserts to further protect and unload these structures. In severe cases,
surgery may be necessary to reduce deformity to prevent recurrence of ulceration.
