Diabetic Foot
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Direct answer
The diabetic foot results from the combined action of peripheral neuropathy (sensory, motor and autonomic), peripheral arterial disease and infection on a foot whose protective pain sense is lost, so ulcers develop under metatarsal heads and deformities and progress painlessly to deep sepsis and gangrene. Neuropathic ulcers are painless, punched-out, occur on weight-bearing plantar skin with warm feet and palpable pulses, whereas ischaemic ulcers are painful, marginal, and accompanied by cold skin and absent pulses; most Indian ulcers are mixed. Management follows the Wagner grade (0 intact skin to 5 whole-foot gangrene): offloading in a total contact cast for plantar neuropathic ulcers, sharp debridement, culture-directed antibiotics with anaerobic cover, glycaemic control, revascularisation for ischaemia, and amputation scaled from ray resection to major limb loss.
What you must remember
- The pathogenic triad is neuropathy, ischaemia and infection; sensory loss is screened at the bedside with the 10 g monofilament and the 128 Hz tuning fork.
- Wagner classification: grade 0 intact but at-risk skin; 1 superficial ulcer; 2 ulcer reaching tendon or joint capsule; 3 deep ulcer with abscess or osteomyelitis; 4 gangrene of toes or forefoot; 5 extensive gangrene of the whole foot.
- The probe-to-bone test with a sterile blunt probe, together with radiography and MRI when needed, evaluates osteomyelitis beneath an ulcer.
- Neuropathic ulcers are painless, plantar, punched-out lesions of warm feet with pulses, treated by offloading — total contact casting being the reference standard; ischaemic ulcers are painful, digital and marginal, in cold pulseless feet needing revascularisation.
- Infection ranges from oral-treatment cellulitis to deep sepsis needing intravenous broad-spectrum anaerobic cover with urgent debridement; vascular assessment is central, since mediasclerosis falsely elevates the ankle-brachial index in diabetics.
- Charcot neuroarthropathy presents as a red, hot, swollen, yet relatively painless foot with preserved sensation profile, treated primarily by immobilisation; bisphosphonates are adjunctive.
- Prevention halves recurrence: daily foot inspection, glycaemic control, never barefoot walking, nail and skin care, and therapeutic footwear.
Common confusion
Students call every diabetic foot ulcer 'infected gangrene needing amputation'. A Wagner 1–2 neuropathic ulcer with good perfusion heals with offloading and debridement alone, and antibiotics without offloading achieve nothing plantar. The second trap is the warm, swollen diabetic foot automatically diagnosed as cellulitis — Charcot neuroarthropathy mimics it exactly, and continued weight-bearing on a Charcot joint destroys the arch into the classic rocker-bottom deformity.
Exam-focused takeaway
Learn the Wagner grades verbatim with their depth descriptors — the classification is a direct one-mark question. Expect stems contrasting painless plantar ulcer with palpable pulses (neuropathic, total contact cast) against painful black toes with absent pulses (ischaemic, revascularise or amputate), and the red hot swollen foot asking the diagnosis (Charcot). The probe-to-bone test, the falsely high ankle-brachial index in diabetes, and the polymicrobial nature of diabetic foot sepsis all recur.
Frequently asked questions
What is the Wagner classification?
A six-point grading of diabetic foot lesions from grade 0 (intact skin, at-risk foot) through superficial and deep ulcers with or without abscess and osteomyelitis, to localised forefoot gangrene (grade 4) and whole-foot gangrene (grade 5).
How are neuropathic and ischaemic ulcers distinguished?
Neuropathic ulcers are painless, punched-out, callused, plantar ulcers over pressure points in a warm foot with pulses; ischaemic ulcers are painful, shallow-margin lesions of the toes and foot edges in a cold, pulseless limb.
Why is offloading central to plantar ulcer healing?
Because the ulcer exists at a pressure point in an insensate foot; healing is impossible while walking loads the wound, so total contact casting or irremovable walkers are the treatment backbone.
When is osteomyelitis suspected and confirmed?
When a sterile probe contacts bone through the ulcer, supported by radiographic cortical destruction, cross-sectional imaging with MRI, and occasionally bone biopsy for culture.