A 65-year-old man with type 2 diabetes of 12 years' duration was referred to the diabetic foot clinic with a dry necrotic 4th toe (Fig. 6.25a). He was admitted for vascular assessment but no intervention was possible so the necrosis was treated conservatively in the belief that surgical removal would leave a large defect which would be difficult to heal in an ischaemic foot. His transcutaneous oxygen tension was 25 mmHg. He was given oral antibiotics, regular debridement along the demarcation line between gangrene and viable tissue and insulin for optimal control of his diabetes. The toes were dressed with Melolin as a non-stick dressing and pieces of gauze were placed between them to separate the gangrenous toe from its neighbours, and the community nurses visited him every day.
After 5 months the gangrenous toe autoamputated to reveal a healed stump (Fig. 6.25b).
• When it is not possible to revascularize the limb, necrotic toes maybe managed conservatively by autoamputation
• We felt that the existing arterial perfusion, as reflected in the transcutaneous oxygen tension of 25 mmHg, was sufficient to allow successful autoamputation but might not enable a surgical amputation wound to heal.
Maggot therapy can be used to debride necrotic tissue and slough in stage 5 feet. The larvae used are those of the green bottle fly.
Medical maggots of Lucilia sericata (the larvae of the green bottle fly) may assist in the eradication of infection by ingesting and digesting bacteria, including MRSA, and infected, sloughy tissue. Because they feed on dead flesh and not on living flesh they are sometimes used to debride infected slough or necrotic tissue from ulcers, particularly in the neuroischaemic foot.
The maggots should be well contained within special bags provided by the 'maggot farm'. These are used to
Fig. 6.25 (a) Necrotic neuroischaemic toe. (b) Autoamputation: the toe has dropped off to reveal a healed stump. (a)
enclose the foot or part of the foot. The bag should be covered with dressings to help absorb exudate, but the maggots may drown or suffocate unless dressings are loosely applied.
Patients should be on bed rest. If the patient is allowed to walk the maggots may be crushed.
The normal skin around the wound should be masked with zinc oxide bandage to prevent the skin being affected by digestive enzymes produced by the maggots which will otherwise make it red and raw.
Copious amounts of thin discharge, which is often a rusty brown colour, and a 'fusty' smell are associated with wounds containing maggots, and patients and other members of staff should be forewarned about this.
Most patients are not bothered by the movements of the maggots within the wound, but ischaemic patients occasionally complain of increased pain during maggot therapy.
The maggots can be irrigated out of the wound on the fourth day.
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