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Diabetes Q&A

Diabetic Foot Ulcers: Managing a Common and Costly Complication

Volume 60 - Issue 3 - March 2020

AUTHORS:
Aswathi Kumar, MD, and Kim A. Carmichael, MD—Series Editor

CITATION:
Kumar A, Carmichael KA. Diabetic foot ulcers: managing a common and costly complication. Consultant. 2020;60(3):85-86. doi:10.25270/con.2020.03.00004

 

For patients with diabetes, the lifetime risk of developing a foot ulcer is approximately 15% to 34%.1,2 In the United States, $9 billion to $13 billion is spent on the management of diabetic foot ulcers and related complications yearly. These complications include lower extremity amputation. Nearly 60% of lower extremity amputations occur in patients with diabetes.3 Foot ulceration increases mortality: The 5-year survival rate of patients after developing a new diabetic foot ulcer is only 50% to 60%.3 This article will answer questions about the evaluation and management of diabetic foot ulcers.

 

Q. What are the risk factors for developing diabetic foot ulcers?

A. The classic triad of peripheral sensory neuropathy, deformity, and trauma is seen in 65% of patients with diabetic foot ulcers.4 Diabetic neuropathy is present in 90% of patients, since sensory neuropathy results in a loss of protective sensation, including nociceptive pain, pressure, and temperature. Autonomic neuropathy can result in decreased sweating, which in turn compromises skin integrity, thereby increasing risk of infection. The loss of protective sensation makes individuals prone to recurring minor trauma that can go undetected and eventually ulcerate. Deformities including Charcot neuroarthropathy, flatfoot, hallux valgus, and hammertoes increase the risk of ulceration by altering biomechanics and pressure points.

Another significant risk factor for diabetic foot ulcers is peripheral arterial disease (PAD), which occurs in 50% of patients with diabetes. These patients also develop PAD at younger ages and have more rapid progression. Concurrent PAD contributes to the risk of nonhealing ulcers, infection, and amputation.

Other risk factors include a history of prior foot ulceration, tobacco use, male sex, a history of diabetes of greater than 10 years’ duration, poor glycemic control, and the presence of cardiac, retinal, or renal complications of diabetes.1,2 Patients at risk should also avoid sodium-glucose transport protein 2 inhibitor therapy.

 

Q. How do you evaluate for diabetic foot ulcers?

A. The American Diabetes Association recommends that all patients with diabetes undergo an annual foot examination by a health care provider. This examination includes visual inspection of the nails, skin, and foot structure. The skin should be assessed for discoloration, wounds, dry skin, and cracks. Callus formation, erythema, or warmth can be signs of tissue damage. Claw toes and hammertoes are signs of motor neuropathy. Evaluation of gait can be informative regarding instability or abnormal biomechanics.5-7

Testing should also include ankle reflexes, vibratory sensation using a 128-Hz tuning fork, and protective sensation using a 10-g monofilament (Semmes-Weinstein). Vibratory sensation is tested at the tip of the big toe in both feet. If the patient loses vibratory sensation before the examiner, it is an abnormal test result. Monofilament testing can be completed at 4 sites (first, third, and fifth metatarsal heads and plantar surface of the big toe) or at 10 sites. The filament should be perpendicular to the skin and pressed until it buckles 1 cm. Pressure is applied for 1 to 2 seconds. Sites should be tested at random, and patients should say yes or no to perception. If the patient fails to respond, that site can be revisited 2 more times. A lack of sensation in a single site each time indicates a loss of protective sensation. Reusable monofilaments should be rested for 24 hours after every 100 compression cycles and replaced every 3 months.5,6

Vascular examination includes palpation of the popliteal, posterior tibial, and dorsalis pedis pulses. Other signs of peripheral arterial disease should be noted, including cold extremities, hair growth, shiny skin, or dependent rubor.5,7

Comprehensive assessment allows for identification of high-risk individuals. High-risk patients have one or more of the following: loss of protective sensation, absent pedal pulses, foot deformity, history of foot ulcers, or prior amputation. High-risk patients need to be monitored more closely. These patients may benefit from protective footwear, additional education, and earlier intervention to prevent the development of ulcers. Patients with known neuropathy should have their feet visually inspected at every visit.5

Existing ulcers should be evaluated for size, location, shape, depth, base, and border. Any drainage or odor should be noted. Radiographs are indicated for deep or infected ulcers. Magnetic resonance imaging is more sensitive for identification of osteomyelitis and abscesses. Culture from the wound base is unnecessary, since most wounds are colonized.4

 

Q. How should you assess for PAD in patients with diabetes?

A. Obtain a history about claudication and lower extremity ischemia. However, patients with PAD may be asymptomatic. Patients who have abnormal pedal pulses on examination should have further evaluation. Typically, the first step is obtaining an ankle-brachial index (ABI). An ABI of less than 0.9 indicates PAD. However, in patients with calcification of arterial walls, and therefore decreased arterial compliance, the ABI can be falsely elevated. For this reason, a toe-brachial index (TBI) should also be obtained in patients with diabetes to decrease false negatives. A TBI of less than 0.7 is consistent with PAD. Alternatively, lower extremity arterial pressures can be assessed using Doppler in a noninvasive vascular laboratory. Patients with a history suggesting ischemia or abnormal vascular pressures should be referred to specialists.4,7

 

Q. What are treatment options for diabetic foot ulcers?

A. Debridement can involve surgical or nonsurgical methods. Surgical debridement is typically considered the gold standard for diabetic ulcers to remove necrotic tissue. Nonsurgical methods include the use of enzymes such as collagenase, the use of sterile maggots, or autolytic debridement using moist dressings to create an optimal environment for the host to clear nonviable tissue. With exception of dry gangrene, ulcers require moist dressings. Moist dressings decrease the risk of infection and promote faster wound healing.

Additionally, off-loading the ulcer area is critical for wound healing. Inadequate off-loading can result in delayed healing. A nonremovable total contact cast (TCC) is considered the most effective method. TCCs redistribute pressures from the forefoot and midfoot to the heel. TCCs provide complete rest of the foot but with restricted activity. Removable cast walkers are composed of a semirigid shell with a rocker sole to remove pressure from the forefoot with activity.

Negative-pressure wound therapy (NPWT) involves the use of intermittent or continuous negative pressure through a vacuum pump connected to foam surface dressing. NPWT improves wound healing and is indicated for complex diabetic foot wounds until formation of granulation tissue at the ulcer surface.1,4

Hyperbaric oxygen therapy has also been used historically to accelerate wound healing. Patients intermittently breathe 100% oxygen at a pressure higher than at sea level for 1 to 2 hours. With this approach, concerns exist regarding barotrauma, pneumothorax, and seizures. In a recent study evaluating the use of topical wound oxygen therapy (TWO2) in treating chronic diabetic foot ulcers, patients receiving TWO2 had increased wound closure rates at 12 weeks and 12 months compared with standard care alone.8

Other therapies that are used in the management of diabetic ulcers include growth factors, bioengineered skin substitutes, extracellular matrix proteins, and matrix metalloproteinase modulators. Further research is needed to investigate the efficacy and role that these modalities play in treating diabetic ulcers.1

 

Q. What should patients be told about proper foot care?

A. Patients should inspect their feet daily, including between the toes. A caregiver can assist if patient is unable to do this. They should wash feet with room-temperature water, be gentle when drying, and keep skin moisturized, except between the toes. Nails should be cut straight across. They should not remove corns and calluses at home. Patients should be counseled to always wear shoes and socks, and check their shoes for foreign objects before wearing. They should not walk barefoot. Recommend that they have their feet examined regularly by a health care provider.

Patients should be instructed on when to notify a health care provider—puncture wounds, ulcers, redness, or new-onset foot pain should be evaluated urgently, preferably the same day. 

 

Aswathi Kumar, MD, is a clinical fellow in the John T. Milliken Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, at the Washington University School of Medicine in St Louis, Missouri.

Kim A. Carmichael, MD, is a professor of medicine in the John T. Milliken Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, at the Washington University School of Medicine in St Louis, Missouri.

 

References:

  1. Alexiadou K, Doupis J. Management of diabetic foot ulcers. Diabetes Ther. 2012;3(1):4. doi:10.1007/s13300-012-0004-9
  2. Armstrong DG, Boulton AJM, Bus SA. Diabetic foot ulcers and their recurrence. N Engl J Med. 2017;376(24):2367-2375. doi:10.1056/NEJMra1615439
  3. Jeffcoate WJ, Vileikyte L, Boyko EJ, Armstrong DG, Boulton AJM. Current challenges and opportunities in the prevention and management of diabetic foot ulcers. Diabetes Care. 2018;​41(4):645-652. doi:10.2337/dc17-1836
  4. Kruse I, Edelman S. Evaluation and treatment of diabetic foot ulcers. Clin Diabetes. 2006;​24(2):91-93. doi:10.2337/diaclin.24.2.91
  5. American Diabetes Association. Preventive foot care in diabetes. Diabetes Care. 2004;27(suppl 1):S63-S64. doi:10.2337/diacare.27.2007.s63
  6. Mishra SC, Chhatbar KC, Kashikar A, Mehndiratta A. Diabetic foot. BMJ. 2017;​359:j5064. doi:10.1136/bmj.j5064
  7. Del Core MA, Ahn J, Lewis RB III, Raspovic KM, Lalli TAJ, Wukich DK. The evaluation and treatment of diabetic foot ulcers and diabetic foot infections. Foot Ankle Orthop. 2018;3(3). doi:10.1177/2473011418788864
  8. Frykberg R, Franks PJ, Edmonds ME, et al. Multinational, multicenter, prospective, randomized, double-blinded, placebo-controlled trial to evaluate the efficacy of cyclical topical wound oxygen therapy (TWO2) in the treatment of chronic diabetic foot ulcers [abstract 43-LB]. Diabetes. 2018;67(suppl 1):LB12. doi:10.2337/db18-43-LB