Diabetic Foot Orthopaedic Management
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Direct answer
Diabetic foot ulceration is a wound or infection of the foot in a person with diabetes, usually driven by neuropathy, peripheral vascular disease and repeated pressure. Orthopaedic management focuses on offloading the ulcer, controlling infection and choosing an amputation level that preserves function. The Wagner classification grades the ulcer by depth, from superficial to gangrene, and the Texas classification adds the status of infection and ischaemia.
What you must remember
- Wagner grade 0: intact skin at risk, with deformity or callus, and no open ulcer.
- Wagner grade 1: a superficial ulcer without deeper involvement.
- Wagner grade 2 and 3: ulcers reaching tendon, capsule or bone (grade 2), and deep ulcers with abscess or osteomyelitis (grade 3).
- Wagner grades 4 and 5: gangrene of the toes or forefoot (grade 4), and gangrene of the whole foot (grade 5).
- Texas classification: grades depth from 0 to III, with stages A to D for no infection or ischaemia (A), infection (B), ischaemia (C) or both (D).
- Probe-to-bone test: a positive result raises the suspicion of osteomyelitis, which needs imaging and bone sampling.
- Offloading: a total contact cast is the standard for plantar neuropathic ulcers, and other removable devices are used when a cast is not suitable.
A sequence for managing the diabetic foot
The diabetic foot needs a fixed sequence of decisions, and examiners expect the steps in roughly this order. The reasoning matters more than any single timing, and perfusion must be assessed before any surgery.
- Assess perfusion: check the pulses and the ankle-brachial index (toe pressure if calcified vessels make it falsely high), since ischaemia changes both healing and the risk of surgery.
- Probe the wound: a positive probe-to-bone test raises suspicion of osteomyelitis, and it prompts further imaging.
- Offload the foot: a total contact cast or another offloading device reduces pressure on the ulcer, which is essential for healing.
- Debride and treat infection: necrotic tissue is removed, and antibiotics are guided by culture from deep tissue or bone.
- Image for osteomyelitis: MRI is the most sensitive imaging test, and bone biopsy with culture gives a definitive diagnosis.
- Plan the amputation level: the limb is preserved where possible, and a ray or transmetatarsal level is chosen when perfusion allows healing.
Where the exam tries to catch you
Diabetic foot questions reward the logic of perfusion, offloading and the level of amputation.
- Trap: treating a deep infected ulcer with antibiotics alone while the patient keeps weight bearing. Correct: debridement and offloading are essential, because antibiotics alone do not heal a pressure-driven ulcer.
- Trap: choosing a high amputation level for gangrene without assessing perfusion. Correct: the level is chosen by perfusion and the extent of tissue loss, so that the wound heals and the most function is preserved.
- Trap: relying on a normal plain radiograph to exclude early osteomyelitis. Correct: radiographic changes lag behind infection, so MRI or bone biopsy is needed for early diagnosis.
Frequently asked questions
What does the Wagner classification of diabetic foot grade?
The Wagner classification grades a diabetic foot ulcer by depth and extent, from grade 0 with intact skin at risk to grade 5 with gangrene of the whole foot. Grade 1 is a superficial ulcer, and grade 3 is a deep ulcer with abscess or osteomyelitis. The grade guides the treatment and the urgency of surgery.
What is the probe-to-bone test in diabetic foot?
The probe-to-bone test is a sterile probe passed into the ulcer to see whether it touches bone. A positive test raises the suspicion of osteomyelitis in the underlying bone. It is a simple bedside test, and it is confirmed by imaging and bone sampling.
Why is a total contact cast used for diabetic foot ulcers?
A total contact cast is used for plantar diabetic foot ulcers because it spreads pressure evenly and off-loads the ulcer while the patient keeps walking. Continuous off-loading is the most effective way to heal a neuropathic plantar ulcer. The cast is used with careful monitoring for infection.
Which investigation is the most sensitive for diabetic foot osteomyelitis?
MRI is the most sensitive imaging test for diabetic foot osteomyelitis, and it shows marrow changes early. Bone biopsy with culture gives the definitive diagnosis and identifies the organism. Plain radiographs are less sensitive early in the course of infection.