Ulcers are skin wounds that are slow to heal. In the foot, as prominent metatarsal heads on the plantar (bottom of the foot) are subjected to increased pressure, the skin begins to become callused. When subjected to shearing forces, there is a separation between the layers on this callused skin, which fills with fluid and becomes contaminated and infected. The result is a foot ulcer.
International NPUAP-EPUAP Ulcer Definition
An ulcer is localized injury to the skin and/or underlying tissue usually over a bony prominence, as a result of pressure, or pressure in combination with shear. A number of contributing or confounding factors are also associated with pressure ulcers; the significance of these factors is yet to be elucidated.
Category/Stage I: Non-blanchable erythema. Intact skin with non-blanchable redness of a localized area usually over a bony prominence.
Category/Stage II: Partial thickness. Partial thickness loss of dermis presenting as a shallow open ulcer with a red pink wound bed, without slough.
Category/Stage III: Full thickness skin loss. Full thickness tissue loss. Subcutaneous fat may be visible but bone, tendon or muscle are not exposed. Slough may be present but does not obscure the depth of tissue loss.
Category/Stage IV: Full thickness tissue loss. Full thickness tissue loss with exposed bone, tendon or muscle. Slough or eschar may be present. Often includes undermining and tunneling.
Additional Categories/Stages for the USA
Unstageable/Unclassified: Full thickness skin or tissue loss – depth unknown
Full thickness tissue loss in which actual depth of the ulcer is completely obscured by slough (yellow, tan, gray, green or brown) and/or eschar (tan, brown or black) in the wound bed. Until enough slough and/or eschar are removed to expose the base of the wound, the true depth cannot be determined; but it will be either a Category/Stage III or IV. Stable (dry, adherent, intact without erythema or fluctuance) eschar on the heels serves as “the body’s natural (biological) cover” and should not be removed.
Suspected Deep Tissue Injury – depth unknown
Purple or maroon localized area of discolored intact skin or blood-filled blister due to damage of underlying soft tissue from pressure and/or shear. The area may be preceded by tissue that is painful, firm, mushy, boggy, warmer or cooler as compared to adjacent tissue. Deep tissue injury may be difficult to detect in individuals with dark skin tones. Evolution may include a thin blister over a dark wound bed. The wound may further evolve and become covered by thin eschar. Evolution may be rapid exposing additional layers of tissue even with optimal treatment.
The are also four major cause of foot ulcers:
- Neuropathic—Related to the nerves and characterized by a loss of sensation in the feet.
- Arterial—Related to poor blood circulation to the lower extremity. This type of ulcer can be very painful and is usually found on the tips of toes, lower legs, ankle, heel, and top of the foot. It can very easily become infected.
- Venous—Related to compromised veins. These ulcers are often seen around the inside of the ankle and are slow to heal.
- Decubitus—Derived from excessive and prolonged pressure on one area of the foot. The most common type of decubitus ulcer of the feet is bed sores on the backs of the heels of people confined to bed for long periods of time.
Foot ulcers are a common problem for diabetics. Contact casts are sometimes applied to the diabetic foot to relieve the bony prominent areas of pressure, allowing ulcers to heal.