10 - The diabetic foot: Pathophysiology and treatment

Abstract

The diabetic foot can be classified into the neuropathic foot, characterized by the neuropathic ulcer, the Charcot joint and neuropathic oedema associated with a good circulation, in which neuropathy predominates, and the ischaemic foot in which atherosclerosis is the dominant factor leading to a reduction in blood flow with absent pulses. In the neuropathic foot, blood flow is increased, the vessels are still and dilated as a result of medial wall calcification and there is evidence for arteriovenous shunting. The neuropathic ulcer characteristically develops on the plantar surface following inflammatory autolysis and haematoma formation under neglected callosities. Chiropody is therefore the mainstay of treatment and recurrence is prevented by redistribution of weight bearing forces by moulded insoles in special footwear. Charcot osteoarthropathy is often preceded by fracture which is a further complication of diabetic neuropathy and which precipitates the rapid bone and joint destruction of the Charcot joint. Neuropathic oedema responds to ephedrine with a reduction in peripheral flow and an increase in urinary sodium excretion. The ischaemic foot is characterized by rest pain, ulceration and gangrene. Medical management can be successful in up to 72%, the remainder needing arteriography to assess suitability for arterial reconstruction or angioplasty. In the diabetic leg, atherosclerosis is predominant in the branches of the popliteal artery making arterial reconstruction difficult. Optimum care of the diabetic foot is provided in a diabetic foot clinic where the skills of chiropodist, shoe-fitter and nurse receive full support from physician and surgeon. Many lesions of the diabetic foot are avoidable and thus patient education is the cornerstone of prevention.