Diabetic patients are prone to foot deformities leading to ulceration and infection of the foot which may progress to tissue necrosis requiring amputation. This is due to a combination of vascular disease and neuropathy.
Diabetes impairs the function of the nerves and blood vessels supplying the feet. This makes them prone to small cuts and pressure ulcers which allow infection to enter and spread through the foot.
Sensory neuropathy robs the diabetic foot of the protective mechanism of pain allowing ulceration to develop in response to minor trauma or rubbing.
Autonomic neuropathy reduces sweating and opens arteriovenous shunts in the foot. The diabetic foot is typically warm, may have strong pedal pulses and dry, cracked skin. The skin fissuring allows entry of bacteria causing localised infection.
Motor neuropathy causes wasting of the small intrinsic muscles of the foot with collapse of the longitudinal and transverse arches. Abnormal pressure areas then develop which progress to ulceration.
Atherosclerosis in diabetics develops at a much younger age and is more extensive and distal. It is not uncommon for a diabetic to have a critically ischaemic foot in the presence of a normal popliteal pulse due to occlusion of the crural arteries. In addition to disease of the major arteries, the capillary basement membranes thicken, impairing oxygen diffusion to the tissues of the foot.
Management is aimed at prevention by careful foot care. Good diabetic control helps reduce the severity of foot complications. There is no specific treatment for neuropathy. Localised infections should be treated with debridement (surgical removal of infected tissue) Plain X-rays may show evidence of osteomyelitis (bone infection) and MRI is an accurate way of defining the extent of infection in the foot.
The outcome for patients with diabetic foot problems is greatly improved by multidisciplinary team-working including diabetes specialist, vascular surgeon, radiologist, and microbiologist. After treatment, ongoing care with a specialist podiatrist and surgical appliance technician to ensure good footwear are beneficial.
It is crucial to maximise the blood flow into the foot. Angioplasty works quite well for the larger arteries but is less reliable for the small arteries around the ankle. Here, bypasses using microsurgical techniques are highly effective at promoting blood flow into the foot to aid healing of wounds.