Source: Podiatry Daily
Written by: Christopher R. Hood, Jr., DPM, and Rhonda Cornell, DPM
Poor or neglected feet often lead patients down the path of ulceration, infection and amputation.1 People with diabetes are at higher risk for these sequelae. Up to 25 percent of the diabetic population will have at least one foot ulceration during their lifetime with 85 percent of lower-limb amputations being preceded by an ulcer.2,3
The latest Centers for Disease Control and Prevention (CDC) National Diabetes Statistics Report (2014) reported 29.1 million people (9.3 percent) in the United States have diabetes.4 The cost of treatment of diabetes and its complications in the United States in 2007 was approximately $116 million with 33 percent of that amount going toward ulcer treatment.3 This number is likely to increase as the diabetic population continues to grow with current estimates suggesting that diabetes will affect 366 million people worldwide by 2030.1
The purpose of this article is to remind us, as podiatric physicians, of the often underappreciated and perhaps sometimes forgotten importance of routine diabetic foot care. Although nail pathology may not be the most glamorous aspect of podiatry, it is our “bread and butter” and we need to be experts in providing this service to our patients.
How Nail Changes Can Lead To Ulcers
There are several pathways to ulceration in patients with diabetic neuropathy, ranging from biomechanical issues causing calluses to stepping on a foreign body. One pathway toward ulceration that we may overlook is the dystrophic, mycotic and neglected toenail. Dystrophy in the toenail can be a manifestation of hereditary, congenital or acquired conditions.
In the patient with diabetes, the origins of ulcers lie in microtrauma or changes in the vascular and nutritional supply to the toenail. Onychomycosis results from dermatophytes (most notably Trichophyton rubrum and Trichophyton mentagrophytes), yeasts (Candida albicans) and non-dermatophyte molds.5,6 It is this thickened nail that causes injury to adjacent skin (whether on the same toe or neighboring toe, known as a “kissing ulcer”) and can erode the nail bed and hyponychium, progressing to nail bed ulceration, paronychia, cellulitis of the skin or osteomyelitis to the underlying bone.7,8 The nail bed is a very thin tissue layer between two and five cells thick with the distal phalanx located directly beneath, putting it at increased risk of bone infection.9
Researchers have shown that one in three patients with diabetes has onychomycosis, making them 2.77 times more likely to develop onychomycosis versus people without diabetes.5,8 Authors have identified tinea pedis infection as another starting point and predictor of foot ulceration in the diabetic population.10Onychomycosis can precipitate tinea pedis and vice versa.10-12 Regardless of the starting mechanism, both fungal infections may lead to foot ulceration, cellulitis, osteomyelitis, gangrene and lower extremity amputation.13,14 Physicians can easily manage and treat onychomycosis and tinea pedis with scheduled podiatric assessment and intervention.
Predisposition to secondary (bacterial) infections may be a consequence of simply having diabetes. This is due to the multiple levels of compromise these patients have, whether it is diabetic peripheral and autonomic neuropathy, peripheral vascular and microvascular disease, immunosuppression, diabetic retinopathy, poor blood glucose control and/or a history of amputation.1,10,15 Even increased age, obesity and limited mobility can increase the potential for infection and are also obstacles to appropriate self care.5,15 Neuropathy prevents patients from feeling any trauma from the nail itself or shoe trauma that may be occurring in this local environment.
Additionally, approximately 20 to 30 percent of patients with peripheral arterial disease (PAD) have diabetes.16 The combination of the neuropathy, no feeling of any lesion development due to dystrophic, mycotic elongated toenails along with the vascular compromise will delay or prevent this lesion from healing. Ulcers stay open and exposed for a longer than ideal time, leaving them susceptible to colonization and infection.
Emphasizing The Role Of Toenail Debridement In Amputation Prevention
Sometimes as busy practicing podiatric surgeons, we forget that toenail debridement in the high-risk patient population is crucial in amputation prevention. Often our resident physicians do not even realize the importance until the patient comes in through the emergency department. At our institution, we provide routine care as an inpatient service often directed by the emergency room physician, primary care physician or infectious disease team. We find it important to stress to our residents, who are surgically driven, to remember the basics of what we do as well.
In a 1995 study, Reiber and colleagues showed that 7.5 percent of diabetic hospital admissions were caused by paronychia.12 The increased rates of onychomycosis in these patients may lend one to think the fungal infection to the nail had some effect. Improvement in foot care starting with debridement of toenail dystrophy and onychomycosis can reduce ulceration, cellulitis and infection rates. This can ultimately decrease complications arising from delayed diagnosis and their associated healthcare expenditures.2,15
Initially, it is important to evaluate these patients in the inpatient setting when possible or appropriate. Explain to patients their situation and stress to them the importance of personal at-home care as well as podiatric physician follow-up care after discharge. By having a podiatrist care for the nails, if a problem were to arise, treatments can start immediately to prevent for example, a neuropathic patient with PAD who cut himself from obtaining a chronic wound and infection. Morbach and colleagues, in an investigational study of 247 patients with an ulcer, found that 12 percent of those ulcers were attributed to “insufficient nail and foot care performed either by the patient, his family, or a professional.”17
In the Seattle Diabetic Foot Study, researchers compared the prediction of diabetic foot ulcer occurrence against certain risk factors and other clinical information in their study population.18 The presence of both tinea pedis and onychomycosis was statistically significant as a clinical finding relating to a higher risk of foot ulcers. Despite some of these fungal infections being treatable, diabetes and other comorbidities make this situation more limb-threatening. Interdigital maceration accounts for as many as 60 percent of cases of leg cellulitis while the fungal foot (toenails, interdigital or plantar) carries a significant risk for cellulitis (odds ratio 2.4) and is often a predictor for developing lower limb cellulitis.10,19
A study by Doyle and coworkers showed patients with diabetes and onychomycosis had a higher rate of foot ulceration, gangrene or a combination of the two.11 In their patient database study, researchers attributed 18 percent of gangrene and 10 percent of foot ulcers in patients with diabetes to starting with onychomycosis.