The Challenge of the Diabetic Foot
Michael S. Pinzur, MD

Dr. Pinzur is Professor of Orthopaedic Surgery, Department of Orthopaedic Surgery and Rehabilitation, Loyola University Medical Center, Maywood, IL. Address for correspondence: Michael S. Pinzur, MD, Department of Orthopaedic Surgery and Rehabilitation, Loyola University Medical Center, 2160 S First Ave, Maywood, IL 60153. E-mail: mpinzu1@lumc.edu.

A comprehensive program combining foot-specific patient education, ongoing skin and nail monitoring, and protective footwear will lower the incidence of diabetic foot ulcers and lower extremity amputations. Treatment of foot problems should be based on the relative risk category assigned to the individual patient. When a primary care physician is faced with a patient with ischemic leg pain or a nonhealing ulcer or wound and evidence of peripheral vascular insufficiency, consultation with a medical or surgical specialist and intervention are warranted. (Annals of Long-Term Care: Clinical Care and Aging 2002;10[1]:41-46)

At any given time, 2-3% of the 16 million persons with diabetes in the United States (4% of the population) have a diabetic foot ulcer (DFU). Fifteen percent of patients with diabetes will develop a DFU at some point during their lifetime. Yearly in the United States, more than 50,000 of those who develop a DFU will undergo a lower extremity amputation (LEA).1,2 Foot infection is the most common reason for hospital admissions of patients with diabetes. Foot infection and DFU are precursors of LEA. Longitudinal population studies have clearly shown that a comprehensive program combining foot-specific patient education, ongoing skin and nail monitoring, and protective footwear will lower the incidence of both foot ulcers and LEAs.3-5 Programs can be developed that do not require major capital expenditure. These programs are cost-effective in both the short and long term. Short-term costs can be recouped because Medicare and most health insurance providers appreciate the value of these services. Long-term costs are substantially decreased when one considers the cost in resource consumption (and dollars) for an amputation as compared to nurse-provided outpatient visits and protective footwear. Guidelines for the development of such a program can be obtained from the November 1999 issue of Foot and Ankle International, an issuededicated to the diabetic foot.3

RISK FACTORS

The primary risk factor for the development of DFUs is the presence of peripheral neuropathy. The clinical threshold for protective sensation is the ability to feel pressure applied by a Semmes-Weinstein 5.07 (10 g) monofilament (Figure 1). Although peripheral vascular disease is common in diabetic individuals and often leads to LEA, identification of asymptomatic peripheral vascular disease does not allow for prophylactic intervention. When patients develop ischemic pain, or have an ulcer or wound thatjdoes not appear to be making progress in healing, the physician should consider vascular intervention.

If dorsalis pedis or posterior tibial pulses are present, delayed healing is likely due to local infection that may require surgical intervention. If pulses are absent, noninvasive testing is appropriate. A Doppler ultrasound ankle brachial index (ratio of ankle Doppler pressure to brachial blood pressure) of less than 0.5 is predictive of inadequate blood flow to support wound healing. Due to calcified arteries, the Doppler ultrasound pressures are often falsely elevated and inaccurate. Measurement of the transcutaneous partial pressure of oxygen gives an accurate indication of the capacity of the cardiovascular system to deliver oxygenated blood to the level in question. Transcutaneous oxygen tensions of more than 30 mm Hg will generally support wound healing. When the tension is below 20 mm Hg, the wound rarely will heal. Therefore, when the clinician is faced with a patient with ischemic leg pain or a nonhealing ulcer or wound and evidence of peripheral vascular insufficiency, consultation and intervention are warranted. Deformities are easy to identify and are frequently amenable to protective care with inlay-depth shoes, custom foot orthoses, or ankle–foot orthoses (Figure 2). Bunions, prominent metatarsal heads, hammer toes, claw toes, diseased or hypertrophic nails, and bony prominences are the most likely places where ulcers will develop. This is due to the concentration of direct pressure or shearing forces to overlying skin that is not capable of handling the mechanical loading. Partial foot amputations are common sites of recurrent ulceration if protective footwear is not prescribed. Thirty to fifty percent of patients with a unilateralamputation will require amputation of the remaining limb if they live five years, so protection of the contralateral remaining limb is important.Patients who have had a previous foot ulcer or infection are prone to redevelop an ulcer or deep infection if not protected.6

PATIENT EDUCATION

Clearly, the most important preventive strategy is foot-specific patient education. Basic guidelines giving the specifics of diabetic foot care (“do’s” and “don’ts”) should be included in diabetic patient education programs. For example, walking barefoot or using chemical corn and callus removers should be avoided. Feet should be inspected and bathed daily with mild soap to decrease the risk for infection. A soft brush should be used to clean around the nails. Feet need to be kept dry, with special attention given to the web spaces. Maceration of the skin between the toes can lead to soft-tissue infection and the initiation of the downward spiral leading to amputation. Lambswool between the toes will prevent moisture or maceration. Natural-fiber stockings absorb perspiration, “breathe,” and cushion bony prominences; these socks also simplify the identification of drainage (white socks are best for this purpose). Dry, scaly skin is prone to cracking or ulceration, providing a site for the development of infection. Oils or skin creams containing lanolin should be used to avoid dryness and prevent skin breakdown. 7 Shoes need to be inspected to determine whether they are potentially harmful. They should accommodate the diabetic foot without being tight or constrictive. Slip-on shoes should be completely avoided due to their constrictive characteristics. Tight, undersized shoes will produce pressure over bony prominences, leading to ulceration and deep infection. The instep needs to be adjustable (by laces or straps) to prevent pressure ulceration. A toe box with inadequate depth or width can lead to pressure ulcers of the toes and/or metatarsal heads. Inspection of the inside of the shoe may reveal irregularities, prominent seams, or pressure sites. Insoles or foot orthoses lose their ability to dissipate pressure and must be replaced periodically. Unusual wear patterns, foot deformities, and partial foot amputations need to be identified and the foot protected with accommodative footwear. Patients who are at risk for amputation will benefit from one-on-one patient education sessions. If the patient has poor eyesight or is limited by arthritis or impaired mobility, a spouse, family member, or other caregiver can do the daily foot inspection. Oftentimes, simple aids such as magnifying glasses or pocket mirrors can be used to access difficult plantar areas. Patients need to notify their medical provider (primary care physician, nurse practitioner, etc) at the first sign of redness, ulceration, blister formation, nail or tissue inflammation, or infection. Early identification of ulcers, wounds, or infection provides the greatest potential for a favorable resolution.

BASIC TREATMENT GUIDELINES

Treatment is advised based on the relative risk category assigned to the individual patient (Table).

Risk Category 0

Risk Category 0 is for persons with a normal-appearing, sensate foot, as measured by the ability to feel pressure from the Semmes-Weinstein 5.07 (10 g) monofilament. These individuals may have minor foot or toe deformities. They can use normal footwear, avoiding shoes with a narrow forefoot, tight toe box, or tight instep. Laced shoes are strongly advised. Peripheral neuropathy will develop in virtually all diabetic individuals with time; therefore, even low-risk individuals should be provided with basic foot education and have their feet examined professionally every year.

Risk Category 1

This category is for persons with a normal-appearing foot with no or minimal deformity. The progression to Risk Category 1 is based on the loss of protective sensation as measured by insensitivity to the Semmes-Weinstein 5.07 monofilament. These persons require more intensive “at-risk” individualized patient education. Due to the loss of protective sensation, these individuals should use pressure-dissipating noncustom insoles, which need to be replaced at least every six months due to loss of resiliency (pressure dissipation; Figure 3). They should wear oxford, soft-leather, laced shoes with adequate size to accommodate pressure-dissipating foot orthoses. These individuals should avoid nonlaced shoes to prevent localized pressure concentration. Prescription footwear is reasonable but not necessary with this risk status. Follow-up examination (monitoring) should be performed every six to 12 months.

Risk Category 2

Risk Category 2 individuals have insensate feet with structural deformity. The deformity may be a bunion, hammer toes, or bony prominences anywhere about the foot. These individuals do not presently have a foot ulcer or a history of a foot ulcer. In addition to “at-risk” education and instruction, it is now advised that these individuals use custom-fabricated, pressure-dissipating, accommodative foot orthoses and inlay-depth, soft-leather, adjustable-lacing shoes (Figure 2). They require more frequent monitoring, with foot examinations every three to six months.

Risk Category 3

The Risk Category 3 foot is insensate, has structural deformity, and has the presence or history of a foot ulcer. These patients require careful clinical treatment and monitoring of the ulcer. Localized or reconstructive surgery is often indicated in this patient population. These individuals are carefully instructed to notify their physician with any new-onset skin or nail pathology. These individuals are patients who require treatment, as opposed to individuals with an at-risk status.8,9

SKIN AND NAIL CARE

Prophylactic nail care can be performed by a trained patient, nurse, or physician. The nails should be trimmed transversely with a commercial, straight nail clipper to avoid ingrown toenails and secondary infection. Thick, mycotic nails or paronychial infection should be treated by a trained professional. Ulceration or infection are likely to develop under thickened, callused skin. A thickened callus is the precursor of ulcer formation. Thickened calluses should be reduced with a pumice stone or power abrader, or sharply trimmed with a scalpel. Underlying ulcers are often identified following callus reduction. These lesions should be reduced with a pumice stone (if thin) or with a sharp blade by a professional (if thick).

WOUND AND ULCER EVALUATION

Open wounds should be assessed for the presence of infection, necrotic tissue, depth, and underlying involvement of bone. The proportions of the depth and width should be recorded in order to objectively monitor progress in healing. If bone can be felt with a probe, the presence of osteomyelitis is highly probable. Superficial swab cultures are inaccurate. If localized infection does not resolve with empiric antibiotic therapy combined with local skin care, tissue cultures taken at the time of surgical debridement are indicated. Osteomyelitis or soft tissue abscess generally requires surgical debridement. Antibiotic therapy can then be culture-specific. Erythema may indicate infection or inflammation from external sources. Swelling may indicate infection, peripheral vascular disease, or Charcot’s arthropathy.

ULCER/WOUND CARE

The first step in caring for an ulcer or an open wound is the creation of a clean, noninfected wound bed. The most effective method of creating a clean wound is with sharp debridement. Enzymatic and chemical “debriding” agents are effective in removing nonviable tissue, but they can create large tissue defects in insensate individuals when not carefully monitored. Ulcers without a deep crater and with no bone exposed can be treated with sharp debridement of infected or necrotic tissue. In the past, the common method for open wound management was applying wet-to-dry dressings saturated with povidone–iodine antiseptic solution. There is now evidence that a dry environment, combined with iodine and other chemical antiseptics, inhibits cell growth and causes the proliferating cells to desiccate and die. This has led to the development of whole commercial families of products for use in debriding, cleansing, and maintaining wounds. The optimal wound environment, following removal of infected or dead tissue, is a continuously moist wound. This can be accomplished with saline-soaked gauze sponges. Dry, nonproliferative, nonproductive wounds can be kept moist with hydrocolloid gels. When the wound produces copious exudate, the skin can become macerated. Secondary infection can be avoided by the use of adsorbents, such as calcium alginate (extracted from seaweed). These products keep the wound moist without allowing supersaturation. 10,11 Platelet-derived growth factors have been identified as playing an intricate role in the wound-healing cascade. This has led to the development of topical wound-healing enhancers, created from extracts of the patient’s platelets. The recombinant human platelet-derived growth factor becaplermin has been shown to stimulate healing in wounds that have the biological capacity to heal.12 Once a clean, noninfected wound is achieved, the next step is “off-loading.” This can be accomplished with the avoidance of weight bearing or the distribution of weight-bearing forces with various types of “healing shoes” (Figures 4a and 4b). Antibiotics are not indicated unless signs of soft-tissue infection (ie, cellulitis) are present. Broad-spectrum drugs directed at skin flora organisms, such as first-generation cephalosporins, are best used empirically at this point. When apparent infection persists, specialty consultation is advised.

Tissue-culture–derived living skin has been developed for application to diabetic foot wounds, including wounds on the plantar surface of the foot. These products are as yet unproven and should be used only after standard methods of treatment have been exhausted. One must remember that split-thickness skin graft, when applied to high-demand regions, is not durable enough to withstand the demands placed upon it.

Consultation With a Medical or Surgical Specialist

The orthopaedic foot and ankle surgeon or podiatristis the first specialist to be consulted by diabetic patients with persistent swelling, erythema, pain, or a nonhealing ulcer. The vascular surgeon rarely advises intervention for nonsymptomatic, or “silent,” peripheral vascular disease. Consultation is advised when the patient develops rest pain, claudication, a nonhealing or expanding ulcer, an ischemic ulcer, or gangrene. Consultation with an infectious disease specialist is warranted when patients do not respond to empiric antibiotic therapy, have an atypical infectious course, or require special monitoring of antibiotic therapy. An endocrinology consultation is essential when glycemic control or overall diabetic management is beyond the scope of the individual primary care physician. Imaging studies beyond plain radiographs are expensive and often do not yield the specific information necessary to enhance treatment. The radiologist can be a valuable consultant in advising the managing physician on the specificity of the different diagnostic imaging studies available locally. Possibly the consultant with the greatest potential for impacting the care of the diabetic patient with foot pathology is a certified pedorthist—a trained professional, knowledgeable in the care of the diabetic foot. A consultation with a pedorthist will assist the primary care physician in prescribing the appropriate pressure-dissipating, accommodative foot orthoses and shoe wear.

References

1. National Diabetes Fact Sheet. Washington, DC: U.S. Dept of Health and Human Services; November 1, 1997.

2. Reiber GE, Lipsky BA, Gibbons GW. The burden of diabetic foot ulcers. Am J Surg 1998;176(suppl 2A):5S-10S.

3. Pinzur MS, Slovenkai MP, Trepman E. Guidelines for diabetic foot care: The Diabetes Committee of the American Orthopaedic Foot and Ankle Society. Foot Ankle Int 1999;20:695-702.

4. Malone JM, Snyder M, Anderson G, et al. Prevention of amputation by diabetic education. Am J Surg 1989;158:520-523.

5. Reiber GE, Smith DG, Boone DA, et al. Design and pilot testing of the DVA/Seattle Footwear System for diabetic patients with foot insensitivity. J Rehabil Res Dev 1997;34:1-8.

6. Pinzur MS, Anderson R, Cantrell R, Lamborn K. The American Orthopaedic Foot and Ankle Society Diabetes 2000 Foot Screen. Foot Ankle Int. In press.

7. American Orthopaedic Foot and Ankle Society. How to Care for Your Diabetic Feet. Seattle, WA: AOFAS. Available at: www.aofas.org/care diabetic.asp. Accessed December 5, 2001.

8. McDermott JE, ed. The Diabetic Foot. Rosemont, IL: American Academy of Orthopaedic Surgeons; 1995.

9. Brodsky JW. The diabetic foot. In: Coughlin MJ, Mann RA. Surgery of the Foot and Ankle. 7th ed. St. Louis, MO: Mosby Inc; 1999: 895-969.

10. Moneta GL, Cavorsi JP, Hunt TK, Veves A. New Approaches in Wound Healing. Monograph produced by the Postgraduate Institute of Medicine, Littleton, CO; 2000.

11. Kerstein MD, Bensing KA, Brill LR, et al. The Physiology of Wound Healing. Monograph produced by the Oxford Institute for Continuing Education, Yardley, PA; 1998.

12. Wieman TJ, Smiell JM, Su Y. Efficacy and safety of topical gel formulation of recombinant human platelet-derived growth factor-BB (becaplermin) in patients with chronic neuropathic diabetic ulcers: A phase III randomized placebo-controlled double-blind study. Diabetes Care 1998;21:822-827.

Annals of Long-Term Care - ISSN: 1524-7929 - Volume 10 - Issue 01 - January 2002