8.5 Characteristics of diabetic foot ulcers

Arteriosclerosis and peripheral vascular disease lead to ischaemia in diabetic patients. In diabetic patients, this is often caused by hypertension, high cholesterol, smoking and uncontrolled blood glucose. We distinguish between macro and micro angiopathy, depending on the size of the blood vessels affected.

Diabetic arteriosclerosis means calcification in the middle layer of the arteries which makes the vessels stiff and non-compressible. Poor blood glucose control leads to microangiopathy in the capillaries. The basal membrane is swollen, preventing effective circulation and exchange of nutrients and waste products in the capillaries.

Neuropathy can cause a lack of perspiration, causing dry, inelastic skin and cracked soles. This results in skin lesions and increased risk of infection. Another possibility may be increased blood circulation which will open standing arterioles and high venous pressure. This increases calcium absorption from the bone, which can lead to convergence of the joints. This leads to a deformed foot and causes new pressure points that can lead to ulceration.

Peripheral neuropathy is divided into sensory and motor neuropathy. Sensory neuropathy causes patients to lose their sense of touch and pain. As a result patients may not recognise ill-fitting footwear and therefore cannot respond to discomfort and injuries of the foot. Motor neuropathy leads to muscle weakness and atrophy of the small muscles in the foot. This leads to deformed toes, a thinner layer of fat over the bony prominences of the foot putting these areas at increased pressure.

Hyperkeratosis forms over pressure-prone areas, and the pressure in the deeper layers of tissue increases. Normally, patients are not able to sense this due to decreased sensation.

Symptoms of the neuropathic and ischaemic foot are as follows:

Neuropathic foot

• Hot and swollen
• Fresh red colour
• Lack of sensation
• Any uncharacteristic pain
• Pulse present
• Corns and calluses
• Risk factors for the development of neuropathy are: hyperglycaemia, alcohol use and a long history of diabetes

Ischaemic foot

• Cold, pale or mottle feet
• Pain at elevation or at rest
• No pulse present
• Lack of hair growth on the leg
• Thick yellow nails which may be loose
• Normal reflex status
• Risk factors for the development of the ischaemic foot are atherosclerosis, insulin resistance, smoking, hyperlipidemia and hypertension

Ischaemic ulcers are in peripheral areas of the foot. They are deep in appearance and there is no capillary bleeding.