Diabetic foot ulcers can be divided into two groups: those in neuropathic feet (so called neuropathic ulcers) and those in feet with ischaemia often associated with neuropathy (so called neuroischaemic ulcers). The neuropathic foot is warm and well perfused with palpable pulses; sweating is diminished, and the skin may be dry and prone to fissuring. The neuroischaemic foot is a cool, pulseless foot; the skin is thin, shiny, and without hair. There is also atrophy of the subcutaneous tissue, and intermittent claudication and rest pain may be absent because of neuropathy.

Left: Neuropathic foot with prominent metatarsal heads and pressure points over the plantar forefoot. Right: Neuroischaemic foot showing pitting oedema secondary to cardiac failure, and hallux valgus and erythema from pressure from tight shoe on medial aspect of first metatarsophalangeal joint

The crucial difference between the two types of feet is the absence or presence of ischaemia. The presence of ischaemia may be confirmed by a pressure index (ankle brachial pressure index < 1). As many diabetic patients have medial arterial calcification, giving an artificially raised ankle systolic pressure, it is also important to examine the Doppler arterial waveform. The normal waveform is pulsatile with a positive forward flow in systole followed by a short reverse flow and a further forward flow in diastole, but in the presence of arterial narrowing the waveform shows a reduced forward flow and is described as “damped.”

Left: Hand held Doppler used with sphygmomanometer to measure ankle systolic pressure. Right: Doppler waveform from normal foot showing normal triphasic pattern (top) and from neuroischaemic foot showing damped pattern (bottom)

Neuropathic foot ulcer

Neuropathic ulcers usually occur on the plantar aspect of the foot under the metatarsal heads or on the plantar aspects of the toes.

Left: Neuropathic foot with plantar ulcer surrounded by callus. Right: Ulcer over …