The outermost layer of skin, the epidermis, is comprised of 5 sub-layers and is estimated to be 75 microns to 0.6mm thick, thinning as one ages. This organ's surface layer, or "horny" stratum corneum, is subjected to daily use and exposure to the environment. It is protected by an acid mantle, which retards certain bacterial and fungal proliferations, a protective water-repellent covering (Alterescu & Alterescu, 1988).
The innermost layer, the dermis, contains blood and lymphatic vessels, nerves and cellular components such as mast cells, leukocytes, macrophages, and fibroblasts (Alterescu & Alterescu, 1988). The dermis decreases in vascularity, elasticity and defensive ability as an individual ages, leading to a loss of water content and slowing of re-epithelialization.
Decreased circulation to the skin of the appendages results in diminished oxygen and nutrients at the cellular level. Reduced production of sebaceous and sweat glands couples with decreased water storage to produce a rough, scaly texture with decreased skin turgor. Diminished tactile sensation is caused by neurosensory changes; pain or friction to surface tissues may go unrecognized. Structural changes occur simultaneously; the loss of subcutaneous plantar fat pads allows for less tissue insulation and vessel support (Jaffe, 1991). The aforementioned physiological functional changes categorize the elderly foot as identifiable at high risk for impaired skin integrity (Jaffe, 1991).
Calluses, or diffuse areas of thickened skin, may form on bony prominences, or any area where soft tissue is exposed to prolonged unrelieved pressure, friction or shear (Lukacs, 1997). Tensile stress may also be a factor in callus formation. Digital deformity, such as toe alignment can cause the head of one phalanx to be compressed against the base of an adjacent metatarsal-phalangeal articulation. The continued pressure may create a hyperkeratotic lesion (Helfand, 1989). The formation of additional layers of skin reflects the body's attempt at a protective mechanism. Calluses may also form under weight bearing areas such as the heel or metatarsal heads. Wearing slippers or ill-fitting shoes that do not have a snug heel counter predisposes an individual to thickened, dry heel skin (Lukacs, 1997).
If the cause of the callus is not identified and eradicated, pressure may intensify as the keratin layers build. A central nucleus develops and a corn (heloma) is generated. The pressure acts as a foreign body, inflammation is common, and ulceration may occur (Helfand, 1989). Appropriate documentation should be made upon assessment of callus, corn or ulcerous conditions, noting the location, width and estimated depth in centimeters, as well as surrounding redness, dryness or bruising (Dorgan et al, 1995).
Skin care may be accomplished by the advanced practice nurse to debride the hyperkeratotic lesion with a pumice stone, foot file or rotary tool, followed by application of an emollient. There is little data available comparing the method of intervention, but general parameters include thickness of callus, degree of expertise, and level of associated patient discomfort (Lukacs, 1997). Most calluses cannot be completely removed, but thinning may bring about relief (Lukacs, 1997). A large foot file may be applied in one direction until the skin is smooth and even with the foot surface (Ruscin et al, 1993).It is not recommended that patients apply commercial products to aid in corn removal, as the concentrations of acid may produce a second degree chemical burn (Helfand, 1989).
Dryness of the skin, decreased elasticity and keratotic thickening may produce fissures which can extend into the dermis. Assessment of depth, size, drainage and condition of surrounding tissues is imperative (Lukacs, 1997) Recent documentation of acceptable interventions includes the application of a solid sheet of high-glycerin content hydrogel, which acts both as a cushion, and possesses bacteriostatic and anti-fungal qualities (Lukacs, 1997). Keratolytic compounds, in an emollient cream or lotion base utilize concentrations of urea, alpha-hydroxy acid, lactic acid and salicylic acid to exfoliate (Lukacs, 1997). Application of any petroleum-based barrier moisturizer to soften the skin should be preceded by a moisture-containing product, and be applied 2-4 times per day and after bathing (Lukacs, 1997).
Maceration of the interdigital web spaces may develop from the use of emollients between the toes, the inability of the elderly to dry their feet completely, or arise due to friction from lateral pressure of shoes or digital contractures (Kosinski & Ramcharitar, 1994). Lamb's wool or cotton gauze is used to separate and dry the interspace, but does not encircle the digit. (Kosinski & Ramcharitar, 1994). The patient is encouraged not to soak their feet, to dry between the toes completely, and switch to shoes with a roomier toe box (Lian, 1992).
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