In response to the abnormal pressure on these joints, the underlying metatarsal fat pads atrophy and a plantar callus forms. Additional pressure on the callus during ambulation causes it to rupture, leading to the formation of a neuropathic ulcer. Patients usually remain unaware of the ulcer formation because of their diminished sensitivity to pain. Diabetic ischemic ulcers differ from neuropathic ulcers. Regardless of type, foot ulcers in a diabetic patient heal more slowly than in nondiabetics and these patients are at greater risk for infection because of chronic degenerative changes.
Venous ulcers arise from disorders of the deep venous system.
Chronic venous hypertension causes changes in the microcirculation which alters the inflammatory mechanism. Transient elevations in venous pressures decrease capillary blood flow and trap white blood cells at the capillary level. In turn, the white blood cells plug capillary loops causing localized ischemia which can lead to ulceration. Factors that contribute to PVD are both genetic and environmental, such as hypertension, hyperlipidemia, diabetes mellitus, smoking, obesity, and a sedentary life style. Management and successful treatment of any lower extremity ulcer are dependent on the skills of the healthcare provider in assessing and recognizing the cause and pathogenesis of each type.