Diabetic Foot Ulcer

Diabetic foot ulcer is a full thickness wound below the ankle in a person with diabetes, caused by neuropathy, ischaemia or both, usually precipitated by trauma or pressure. It is a leading cause of non traumatic amputation.

• Risk factors: peripheral neuropathy, peripheral arterial disease, foot deformity, previous ulcer or amputation, barefoot walking, poor glycaemic control, renal disease, visual impairment, callus.
• Ulcer types: neuropathic (plantar, warm foot, palpable pulses), ischaemic (toes and margins, cool foot, absent pulses), neuroischaemic (mixed).

Painless plantar ulcer with surrounding callus in neuropathic disease; painful punched out ulcer on toes or heel in ischaemic disease.

• Dry skin, claw toes, high arch, loss of sensation to a 10 g monofilament, absent ankle reflexes, absent pulses, delayed capillary refill, shiny hairless skin.
• Infection: erythema over 0.5 cm, warmth, swelling, purulence, odour; deep infection with fever, high glucose, systemic signs.
• Differential diagnosis: venous ulcer, pressure ulcer, arterial ulcer, pyoderma gangrenosum, vasculitis, leprosy, malignancy, Charcot arthropathy, gout, osteomyelitis, tropical ulcer.
• Complications: cellulitis, abscess, necrotising infection, osteomyelitis, gangrene, Charcot foot, sepsis, amputation, death.

Systematic foot examination and infection staging.

• Measure ulcer size and depth, probe to bone, examine pulses, monofilament testing, ankle brachial index (unreliable if over 1.3 from calcification, use toe pressure and toe brachial index).
• Full blood count, CRP, ESR, glucose, HbA1c, creatinine, blood cultures if systemic; deep tissue culture after debridement (swab of surface is unreliable).
• Plain radiograph for bone changes and gas; MRI for osteomyelitis and abscess; Doppler or CT angiography when ischaemia is suspected.

Offload, debride, treat infection, restore perfusion and control glucose.

• Supportive: complete offloading (total contact cast, removable walker made irremovable, or bed rest), glycaemic control (target HbA1c 7 to 8 percent), stop smoking, optimise blood pressure and lipids, nutrition with protein 1.25 to 1.5 g/kg/day, daily foot inspection and footwear education.
• Pharmacological: mild infection: amoxicillin clavulanate 625 mg three times daily for 7 days (or flucloxacillin 500 mg four times daily; clindamycin 300 mg four times daily if penicillin allergic). Moderate or severe infection: ceftriaxone 2 g IV daily plus metronidazole 500 mg IV every 8 hours, or piperacillin tazobactam 4.5 g IV every 8 hours; add vancomycin 15 to 20 mg/kg IV every 12 hours (or linezolid 600 mg twice daily) for MRSA risk. Duration 1 to 2 weeks for soft tissue infection, 6 weeks for osteomyelitis without resection, 2 to 5 days after complete bone resection. Aspirin 75 mg daily and atorvastatin 40 mg at night in vascular disease. Analgesia with paracetamol 1 g, amitriptyline 10 to 25 mg or gabapentin 300 mg at night for painful neuropathy. Tetanus toxoid if indicated. Insulin for hyperglycaemia during infection.
• Procedures: sharp debridement of callus and necrosis; drainage of abscess; revascularisation (angioplasty or bypass) when toe pressure is under 30 mmHg or ankle brachial index under 0.5, or for non healing despite 4 weeks of care; resection of infected bone; negative pressure therapy after infection control; amputation for gangrene, uncontrolled infection or non reconstructable ischaemia.
• Special groups: renal impairment, adjust antibiotic doses and avoid nephrotoxins; pregnancy, avoid ACE inhibitors and statins and use insulin; HIV, screen for tuberculosis and hepatitis B; elderly, full geriatric assessment.
• Red flags: fever, spreading erythema, gas in tissue, rapid deterioration, severe pain in an ischaemic foot, wet gangrene, hypotension, diabetic ketoacidosis, exposed bone.
• Follow-up: weekly debridement and measurement; expect over 50 percent reduction in size at 4 weeks; foot screening every 1 to 3 months after healing; custom footwear and lifelong podiatry.