Diabetic Foot
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Direct answer
Foot ulceration in diabetes follows a predictable chain: sensorimotor neuropathy abolishes the protective pain reflex and shifts pressure onto the metatarsal heads, autonomic neuropathy dries and fissures the skin, motor neuropathy deforms the arch, and macrovascular disease starves the resulting wound. Management therefore stands on four pillars — grading (Wagner), offloading, infection control with bedside debridement, and revascularisation of the ischaemic limb. A warm foot with palpable pulses and a punched-out plantar ulcer under a metatarsal head is neuropathic; a cold, pulseless foot with marginal gangrene is ischaemic and needs vascular imaging first. Charcot neuroarthropathy — a hot, swollen, misaligned but relatively painless foot — is immobilised in its acute phase, not operated upon.
What you must remember
- Wagner grades: 0 intact skin with deformity or callus; 1 superficial ulcer; 2 deep to tendon, capsule or bone; 3 deep with abscess or osteomyelitis; 4 forefoot gangrene; 5 whole-foot gangrene — treatment escalates from offloading through debridement to minor and major amputation by grade.
- Bedside tests: loss of perception of the 10-g Semmes-Weinstein monofilament defines the at-risk foot; probe-to-bone contact with a sterile probe strongly suggests osteomyelitis, which MRI confirms far earlier than plain films.
- Offloading: the total contact cast for plantar neuropathic ulcers equalises pressure and heals most ulcers within 6-12 weeks; therapeutic footwear after healing prevents the next one.
- Infection layers: mild — oral co-amoxiclav; limb-threatening — intravenous broad-spectrum cover with surgical debridement; osteomyelitis — resect infected bone (a ray amputation for a metatarsal head) with culture-directed therapy.
- Ischaemic limb: absent pulses or an ankle-brachial index under 0.9 sends the patient to duplex and revascularisation — angioplasty for short-segment disease, distal bypass for long occlusions; calcified diabetic vessels can falsely elevate the index, so toe pressures help.
- Charcot foot: an acutely hot, swollen, relatively painless foot with intact skin is not cellulitis — offload in a total contact cast for about three months until consolidation; fusion surgery is reserved for unstable deformity after the foot cools.
- Indian context: with one of the world's largest diabetic populations, most Indian ulcers are neuropathic and barefoot-walking related; NPCDCS district clinics now screen feet with monofilaments at diabetes visits — a national-programme detail worth quoting.
Walking a plantar ulcer through the clinic
A 54-year-old with twelve years of diabetes arrives with a callus ulcer under the second metatarsal head. The foot is warm, the pulses are bounding, and sensation to the 10-g monofilament is absent — a neuropathic Wagner 2 ulcer. The sterile probe does not touch bone and the X-ray is normal, so osteomyelitis is unlikely. Sharp debridement of the callus rim, a total contact cast, co-amoxiclav for the surrounding cellulitis, and review every two weeks: healed by week eight, then accommodative footwear for life.
Now change one variable. The probe grazes bone, the ulcer is deep and probing-to-bone positive, and MRI shows marrow oedema of the second metatarsal — Wagner 3 osteomyelitis. The pathway becomes resection: excise the infected metatarsal head as a ray amputation, culture the bone, target six or more weeks of culture-directed antibiotics, and offload throughout. Change the last variable — cold foot, absent pulses, black toes — and the patient belongs to the vascular theatre before any local wound care, because debridement on an unrevascularised foot creates a bigger, wetter wound.
Where students slip
The commonest slip is treating the hot Charcot foot as infection — antibiotics for a warm, anaesthetic, deformed foot with intact skin waste the three-month window in which casting protects the architecture. The second is misreading Wagner grades: forefoot gangrene is grade 4 and whole-foot gangrene grade 5, and the distinction decides ray amputation versus below-knee amputation in the examination answer. The third is assuming every diabetic ulcer marches to amputation; most neuropathic ulcers heal with nothing more sophisticated than offloading and debridement — which is exactly why NBE frames offloading as the "next best step" in so many stems.
Frequently asked questions
Which Wagner grade describes forefoot gangrene?
Grade 4; gangrene of the whole foot is grade 5, and that distinction usually decides between local and major amputation.
What does a positive probe-to-bone test indicate?
Osteomyelitis beneath the ulcer, best confirmed by MRI, since plain X-rays may stay normal for weeks.
What is first-line offloading for a plantar neuropathic ulcer?
The total contact cast, which heals most ulcers within 6-12 weeks by distributing pressure evenly across the sole.
How is acute Charcot neuroarthropathy managed?
By immediate immobilisation and total contact casting for roughly three months until consolidation — antibiotics have no role with intact skin.
When does a diabetic foot need revascularisation?
When ulcers or rest pain accompany absent pulses or an ankle-brachial index under 0.9 — duplex first, then angioplasty or bypass before local wound care.