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.10 Onychomycosis 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.