Diabetic foot syndrome

Definition. Diabetic foot syndrome is ulceration, infection and/or destruction of deep tissues of the foot in a person with diabetes, arising from the interaction of peripheral neuropathy, peripheral arterial disease and repetitive mechanical stress. The majority of the elderly diabetic population is at increased risk of developing foot ulcers.

Principal antecedents. Peripheral vascular disease, sensorimotor and autonomic neuropathy, limited joint mobility — which impairs the ability of older people to inspect their own feet — and high foot pressures. Coexisting visual loss exacerbates the consequences of this situation, and visual acuity is impaired in about 40% of older diabetics.

Peripheral sensorimotor neuropathy is the dominant mechanism — the primary cause or a contributory factor in the vast majority of cases. It causes numbness, lancinating and burning pain, "pins and needles" and hyperaesthesia typically worse at night, and produces high foot pressures leading to gait disturbance, falls and other foot injuries. Autonomic neuropathy causes dry, fissured skin and arteriovenous shunting.

Ulcer characteristics. Diabetic ulcers most commonly form in weight-bearing areas — the metatarsal heads and heel. They are usually deep, with undermined edges, surrounded by hyperkeratosis (callus), and are often painless because of the peripheral neuropathy — which is why they present late.

Distinguish from the other foot ulcers of old age. Arterial — painful, with coldness, atrophy and hairlessness of surrounding skin. Venous — between the ankle and calf, shallow, irregular borders, substantial exudate, with oedematous and hyperpigmented surrounding tissue. Decubitus (pressure) — posterior heel or malleoli in those confined to bed or using wheelchairs.

Clinical classification. Describe the ulcer as neuropathic (loss of protective sensation, no PAD), neuro-ischaemic (both) or ischaemic (PAD without loss of protective sensation). Severity is graded by the Wagner grades, or by the SINBAD and WIfI systems; infection severity by the IWGDF/IDSA scheme.

Assessment. 10 g Semmes–Weinstein monofilament and 128 Hz tuning fork for loss of protective sensation; palpation of pedal pulses and ankle–brachial index, with toe pressures or TcPO₂ when vessels are calcified and the ABI is falsely high; probe-to-bone test; plain radiograph and MRI for osteomyelitis; deep tissue culture rather than superficial swab; plus glycaemic, renal, nutritional and vision and gait assessment.

Management principles. Managing foot ulceration in older people involves addressing the underlying aetiology — surgical revascularisation for arterial ulcers and optimum management of blood sugar levels for diabetic foot ulcers — in addition to debridement, management of infection, and application of appropriate topical medications, wound dressings and offloading techniques.

Prognosis and burden. The three-year survival following lower extremity amputation is about 50%, and in about 70% of cases amputation is precipitated by foot ulceration. Increasing age and a higher level of amputation are important factors increasing both length of hospitalisation and cost. A history of foot ulceration is independently associated with visual loss and with increased mortality at ten years.

Prevention — five key elements. Identify the at-risk foot; inspect and examine the at-risk foot regularly; educate the patient, family and healthcare providers; ensure routine wearing of appropriate footwear; and treat pre-ulcerative signs — callus, haemorrhage under callus, blister, fissure, ingrowing nail. A multidisciplinary foot-care team approach decreases the incidence of major amputation. Diabetic foot ulcer ↓ Assess: neuropathy (monofilament) · perfusion (pulses, ABI, toe pressure) · infection (IWGDF/IDSA) · depth (probe-to-bone) ↓ Neuropathic Neuro-ischaemic / ischaemic Debride callus · non-removable knee- Urgent vascular assessment · high offloading · dressings revascularisation · cautious offloading ↓ Infection → culture-directed antibiotics · surgical drainage · exclude osteomyelitis LATEST UPDATES (2023–PRESENT) — 2 POINTS

IWGDF 2023 classification guideline. SINBAD (Site, Ischaemia, Bacterial infection, Area, Depth) is the recommended first-choice system for communication between healthcare professionals — stating the presence or absence of each composing variable rather than only a total score — and the full SINBAD score is recommended for regional, national and international audit. Use the IWGDF/IDSA (2015) system to classify infection severity and consider WIfI to stratify healing likelihood and amputation risk in peripheral arterial disease. Crucially, no currently available classification should be used to give an individual patient an outcome prognosis.

IWGDF 2023 offloading guideline — offloading is the single most important healing intervention. The preferred treatment for a neuropathic plantar forefoot or midfoot ulcer is a non-removable knee-high offloading device — either a total contact cast or a removable walker rendered irremovable by the provider fitting it. If a non-removable device is contraindicated or not tolerated, use a removable knee-high or ankle-high device with explicit education on adherence; if no other biomechanical relief is available, use felted foam only in combination with appropriate footwear. For ulcers on digits 2–5 secondary to a flexible toe deformity, perform digital flexor tenotomy. Be more cautious with offloading when infection or ischaemia is present.