Local mechanical factors, inadequate perfusion, and foreign material can impair tissue repair. Chronic ulcers illustrate several distinct mechanisms of healing failure.
Factors that interfere with repair
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Increased local pressure or torsion caused by mobility may pull wounds apart.
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Poor perfusion caused by arteriosclerosis, diabetes, or obstructed venous drainage impairs healing.
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Foreign bodies, including fragments of steel, glass, or bone, impede healing.
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Glucocorticoids may be prescribed with antibiotics for corneal infections to reduce collagen deposition and the associated risk of vision loss.
Patterns of abnormal repair
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Complications of repair include deficient scar formation, excessive deposition of repair components, and contractures.
Chronic wound types
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Venous leg ulcers develop most often in elderly people with chronic venous hypertension. Severe varicose veins or congestive heart failure may cause this hypertension, resulting in poor oxygen delivery.
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Arterial ulcers occur with atherosclerosis of peripheral arteries, especially in association with diabetes. Vascular compromise causes ischemia, impairs repair, and may produce painful necrosis of the skin and underlying tissues.
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Diabetic ulcers affect the lower extremities, particularly the feet. Small vessel disease causing ischemia, neuropathy, and secondary infections contribute to necrosis and failure to heal.
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Diabetic ulcers show epidermal ulceration and extensive granulation tissue in the underlying dermis.
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Pressure sores consist of skin ulceration and underlying tissue necrosis caused by prolonged compression against bone, as in bedridden individuals. Mechanical pressure and local ischemia produce the lesions.