Techniques to treat necrosis

• Outpatient debridement

• Operative surgical debridement

• Facilitated autoamputation

Fig. 6.15 This 4th toe is dry and well demarcated and has been debrided at 2-weekly intervals by the podiatrist—note the beautifully clean demarcation line between necrosis and viable tissue.

Outpatient debridement

The rationale for outpatient debriding of necrosis is as follows:

• Removes wet necrosis, which is an excellent culture medium for microorganisms, thus rendering infection less likely (Figs 6.14, 6.15). Debridement enables inspection of the underlying tissues: are there pockets of pus, are the tissues well perfused, is there healthy granulating tissue underlying necrosis?

Fig. 6.14 This necrotic toe is exuding pus from along the demarcation line between necrosis and viable tissue and needs to be debrided.

• Speeds healing by converting the lesion into an acute wound

• Removes a physical barrier from the edge of the wound, enabling new epithelium to grow across more easily

• The necrosis removed can be sent to the laboratory for culture and sensitivities

• Enables the true dimensions of the lesion to be seen, and in particular the depth (Fig. 6.16a,b).

The operator works from proximal to distal, away from the demarcation line, to avoid cutting into viable tisse.

Wet necrosis is grasped in forceps and gentle traction is applied so that the tissue being cut is taut, which enables greater precision (Fig. 6.17a-c).

Heaped up material along the demarcation line is removed.

When necrotic material is sent for culture the surface material is first debrided away and the tissue sample is taken from deeper areas.

Haemodialysis patients, who undergo rapid haemody-namic changes on dialysis, are heparinized to prevent clotting of the access graft, so ulcerated and necrotic lesions may bleed on debridement around the time of dialysis.

Operative surgical debridement (neuropathic and neuroischaemic foot)

Surgical debridement or amputation should be considered if the necrotic toe or any other area of necrosis is painful or if the circulation is not severely impaired, that is, a pressure index above 0.5 or a transcutaneous oxygen tension above 30 mmHg. Postoperatively there may be a considerable tissue deficit with exposure of bone or tendon. Such deficits may be repaired by plastic reconstructive surgery.

Transcutaneous Oxygen Tension

Fig. 6.16 (a) This patient has developed dry necrosis on the lateral border of the heel but the depth of the necrosis is not clear, (b) An area of necrosis has been sharp debrided to reveal the true depth of the necrosis, but viable tissue has not been injured. In this case necrosis is superficial and can be treated by regular podiatric debridement.

Fig. 6.16 (a) This patient has developed dry necrosis on the lateral border of the heel but the depth of the necrosis is not clear, (b) An area of necrosis has been sharp debrided to reveal the true depth of the necrosis, but viable tissue has not been injured. In this case necrosis is superficial and can be treated by regular podiatric debridement.

Before surgery

The preparation and principles of operative debridement are similar to that described in stage 4. Patients will need:

• Full blood count and typing

• Serum electrolytes and creatinine

• Blood glucose

• Liver function tests

Consent should be obtained for the most extensive debridement anticipated, including digital or ray amputation.

During surgery

It is important to remove all necrotic tissue, down to bleeding tissue, as well as opening up all sinuses. Deep necrotic tissue should be sent for culture immediately.

Wounds should not be sutured. A foot with a large gaping wound following extensive tissue removal may be lightly held together by winding long strips of paraffin gauze around the foot: however, the strips should be cut through to accommodate swelling and must not prevent draining of exudate.

After surgery

In the neuropathic foot, irrigation with 2% Milton (1 in 50 dilution—see Chapter 5) maybe useful for 5 days. Any Milton solution in contact with the skin should carefully be rinsed off as it has an extremely drying effect. After rinsing, emollient cream should be applied to intact skin.

Ischaemic wounds are extremely slow to heal even after revascularization, and wound care needs to continue on an outpatient basis in the diabetic foot clinic. Some feet take many months, or even years, to heal, but with patience outcomes may be surprisingly good. Even if healing is never achieved many patients prefer to live with an ulcerated foot than to undergo amputation.

Repair of tissue deficits

Debridement of necrotic lesions of the foot often leads to severe tissue deficits. Management of these soft tissue deficits is complex and skin grafts, local flaps and free tissue transfer have been used. Free tissue transfer is usually carried out for limb salvage and combined with arterial reconstruction in the ischaemic limb. Donor tissue from above the waist is usually used, particularly muscle flaps from the rectus abdominis or latissimus dorsi.

In a free tissue transfer, the arteriovenous pedicle accompanies the transferred tissue and is anastomosed to recipient vessels. A pedal or tibial vessel, which is either a bypass graft or a native revascularized artery, serves as the inflow tract for the free flap which is anastomosed using microsurgical techniques.

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Responses

  • Haiden Martin
    How do you treat necrotic diabetic foot?
    7 years ago
  • mhret
    How to treat dry necrosis?
    7 years ago
  • ivano
    How to treat diabetic necrotic toes?
    6 years ago

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