Diabetic foot ulcers and infections: Current concepts

Advances in Skin & Wound Care, Jan/Feb 2002 by Calhoun, Jason H, Overgaard, Kristi A, Stevens, C Melinda, Dowling, James P E, Mader, Jon T

To aid in the proper selection of dressing material, an accurate description of the wound characteristics should be obtained.51 Several aspects of a wound that should be given particular attention include the color of the wound bed, the size and location of the wound, the wound margins (to identify sinus tracts and undermining), and the characteristics of the exudate (type, amount, color, consistency, odor, and adherence to the wound base). The wound should be observed on an ongoing basis so that dressing selection is based on the wound stage. One particular dressing should not be used for all wound healing stages and situations. The overall goal is to select the appropriate dressing for restoring and maintaining normal wound physiology.52

Off-loading

Pressure reduction, or off-loading, is a key element in the proper treatment of diabetic foot ulcers. The excessive and prolonged abnormal pressures that occur in a neuropathic diabetic foot must be corrected before wound healing can occur. Off-loading is any measure to eliminate these abnormal pressure points to promote healing or prevent recurrence of diabetic foot ulcers. Several methods have been used to protect the foot from abnormal pressures, such as bed rest, non-weight bearing crutches, walkers, and a myriad of orthotic devices. Many of these methods are impractical; patients are often noncompliant and their wounds are unable to heal.

The goal of off-loading therapy, therefore, should be to reduce the pressure at the ulcer site while maintaining ambulation. Total contact casts (TCCs) have been shown to be effective in the treatment of plantar foot ulceration while allowing the patient to be ambulatory.53,54 TCCs are minimally padded, well-molded plaster casts that allow for even distribution of pressure across the plantar surface of the foot,55 thereby eliminating the excessive concentration of pressure responsible for the ulceration. Patients are unable to remove the casts, forcing compliance. Most studies using TCCs to treat plantar ulcers have found typical mean healing times of approximately 8 weeks.54 TCCs are not indicated for infected wounds. They also require a high degree of skill on the practitioner's part to ensure proper fitting.

Other devices such as the Charcot's restraint orthotic walker (CROW walker), removable walking casts, or half shoes are alternatives that can be removed for local wound care. Patient compliance while using removable devices is essential or healing will not occur. Pressure reduction must be maintained following healing to prevent recurrent ulceration.

Hyperbaric oxygen therapy

Wound healing is a dynamic process and adequate oxygen tensions are needed for healing to occur. Hyperbaric oxygen (HBO) therapy has been used for many years as an adjunctive therapy in the treatment of diabetic foot wounds. In 1969, Silver56 demonstrated the oxygen gradient in wounds. Since that time, both hypoxia and lactic acid production have been found to be stimulants for fibroblast replication,57 collagen production,58 and angiogenesis.59 Fibroblasts are stimulated to divide by low oxygen tensions, yet require higher (>30 mm Hg) oxygen tension for collagen synthesis. Tissue, especially healing tissue, requires oxygen for viability. HBO therapy increases tissue oxygen levels, combating the local ischemic effect at the perimeter of the wound where much of the collagen is laid down by the fibroblasts. The increased tissue oxygen levels at the wound perimeter also increase the oxygen gradient between the viable wound edge and the wound's dead space, thereby stimulating fibroblast division at the wound edge and the wound healing process.