Diabetic Foot Ulcer

1. Clinical Overview

A Diabetic Foot Ulcer (DFU) is a full-thickness wound below the ankle in a patient with diabetes mellitus, arising from the complex interaction of peripheral neuropathy, peripheral arterial disease, and biomechanical abnormalities. DFUs represent one of the most devastating complications of diabetes, accounting for the leading cause of non-traumatic lower extremity amputations worldwide. [1]

The condition affects approximately 15-25% of individuals with diabetes during their lifetime, with annual incidence rates of 2-4%. [2] The clinical significance extends beyond local tissue damage: diabetic foot complications are associated with substantial morbidity, mortality, and healthcare costs, with 5-year mortality rates following major amputation approaching 50-70%, comparable to or exceeding many malignancies. [3]

Management requires a coordinated multidisciplinary approach involving diabetologists, vascular surgeons, orthopaedic or podiatric surgeons, specialist nurses, podiatrists, and orthotists. The fundamental principles rest on the "VIP" triad: Vascular assessment and revascularisation, Infection control, and Pressure offloading. Evidence-based interventions, particularly total contact casting for offloading and prompt revascularisation, can achieve healing rates exceeding 80-90% in appropriately selected patients. [4]

Key Facts

• Global Burden: Every 20 seconds, a lower limb is lost to diabetes complications worldwide. [5]
• Lifetime Risk: 25% of people with diabetes will develop a foot ulcer during their lifetime. [2]
• Amputation Link: 85% of diabetes-related lower extremity amputations are preceded by a foot ulcer. [1]
• The Triad: Neuropathy + Ischaemia + Trauma = Ulcer formation.
• Mortality: 5-year mortality after diabetic foot ulcer ranges from 30-40%; after major amputation it reaches 50-70%. [3]
• Osteomyelitis: Probe-to-bone test has positive predictive value > 90% for underlying osteomyelitis. [6]
• Recurrence: 40% of healed ulcers recur within 1 year; 65% within 5 years. [7]

Clinical Pearls

"Probe to Bone": In a deep diabetic foot ulcer, if a sterile metal probe touches something hard and gritty at the ulcer base, the positive predictive value for osteomyelitis exceeds 90%. This simple bedside test guides antibiotic therapy and surgical planning. [6]

"Assume Sepsis is Silent": Diabetic patients often have blunted inflammatory responses due to immunosuppression and neuropathy. Deep plantar space infections may present without fever, tachycardia, or leucocytosis. Unexplained hyperglycaemia, subtle foot swelling, or minimal pain may be the only clues to life-threatening infection. [8]

"Don't Trust the ABPI": Medial arterial calcification (Mönckeberg sclerosis) renders ankle vessels incompressible, producing falsely elevated ABPI readings > 1.3. Always use toe-brachial pressure index (TBPI) or pulse volume waveforms for accurate vascular assessment in diabetes. [9]

"It's Not the Sugar, It's the Shoe": Most neuropathic ulcers result from repetitive mechanical stress (ill-fitting footwear, walking barefoot) on insensate, deformed feet rather than direct metabolic injury. Offloading and pressure redistribution are as critical as glycaemic control. [10]

"Red Hot Foot = Charcot Until Proven Otherwise": An acutely red, hot, swollen foot in a diabetic patient with neuropathy suggests Charcot neuroarthropathy rather than infection in many cases. Elevate the leg: Charcot redness diminishes; cellulitis persists. Immediate immobilisation prevents catastrophic skeletal collapse. [11]

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2. Epidemiology

Incidence and Prevalence

Diabetic foot ulceration affects approximately 15-25% of individuals with diabetes during their lifetime. [2] Annual incidence rates range from 2-4% per year among people with diabetes, with point prevalence in diabetic populations estimated at 4-10%. [12]

Global estimates suggest over 18 million people worldwide currently have active diabetic foot ulcers, with the burden disproportionately affecting low- and middle-income countries where access to multidisciplinary foot care services is limited. [5]

Demographics

Age: Incidence increases with duration of diabetes. Patients with > 10 years of diabetes have significantly higher risk. [12]

Sex: Slightly higher prevalence in males (approximately 1.5:1 male-to-female ratio), potentially related to higher rates of peripheral arterial disease and occupational trauma. [13]

Ethnicity: Higher rates observed in Indigenous populations, Pacific Islanders, and individuals of African descent, partially attributable to increased diabetes prevalence and reduced access to preventive foot care. [13]

Risk Factors (The "Foot at Risk")

The International Working Group on the Diabetic Foot (IWGDF) identifies key predictive factors: [14]

High Risk (Immediate Prevention Required):

• Previous foot ulcer or amputation: Single strongest predictor (relative risk 10-fold increase). [7]
• Loss of protective sensation (LOPS): Inability to feel 10g Semmes-Weinstein monofilament.
• Peripheral arterial disease: Absent foot pulses, TBPI less than 0.5.
• Foot deformity: Claw toes, hallux valgus, Charcot foot, prominent metatarsal heads.

Moderate Risk:

• Peripheral neuropathy alone (without deformity or PAD).
• Peripheral arterial disease alone (without neuropathy).
• Poor glycaemic control: HbA1c > 8% (64 mmol/mol).
• Visual impairment (inability to inspect feet).
• Renal impairment (eGFR less than 30 mL/min/1.73m²).
• Smoking (accelerates macrovascular disease).

Additional Factors:

• Poor footwear: Ill-fitting shoes, walking barefoot.
• Living alone (reduced capacity for foot monitoring).
• Low socioeconomic status (reduced access to preventive care).

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3. Aetiology and Pathophysiology

Diabetic foot ulceration results from the complex interplay of three principal pathophysiological mechanisms: peripheral neuropathy, peripheral arterial disease, and biomechanical deformity, compounded by susceptibility to infection.

1. Peripheral Neuropathy (The Primary Driver)

Chronic hyperglycaemia induces nerve damage through multiple mechanisms:

A. Sensory Neuropathy

Diabetes causes progressive loss of small-fibre (pain, temperature) and large-fibre (vibration, proprioception) function through:

• Polyol pathway activation: Accumulation of sorbitol and fructose within Schwann cells, causing osmotic stress.
• Advanced glycation end-products (AGEs): Glycation of structural nerve proteins, disrupting axonal transport.
• Oxidative stress: Mitochondrial superoxide production damaging neuronal membranes.
• Microvascular ischaemia: Occlusion of vasa nervorum reducing endoneurial blood flow. [15]

Clinical consequence: Loss of protective sensation (LOPS) prevents detection of repetitive mechanical stress, acute trauma (stepping on foreign objects), or thermal injury. Patients continue ambulation on injured tissue, perpetuating the ulcerative cycle. [10]

B. Motor Neuropathy

Denervation of intrinsic foot muscles (lumbricals, interossei) causes:

• Intrinsic minus foot: Unopposed action of long flexors and extensors.
• Claw toe deformity: MTP hyperextension, IP flexion.
• Prominent metatarsal heads: Increased plantar pressure (can exceed 1200 kPa vs. normal 200-400 kPa).
• Pes cavus: High arch increasing forefoot pressure. [16]

Clinical consequence: Abnormal pressure distribution creates focal high-stress areas susceptible to callus formation and ulceration.

C. Autonomic Neuropathy

Sympathetic denervation produces:

• Anhidrosis: Loss of sudomotor function causing dry, fissured skin (portals for bacterial entry).
• Arteriovenous shunting: Opening of AV anastomoses shunts blood away from nutritive capillaries, paradoxically creating a "warm, well-perfused" foot with tissue ischaemia.
• Bone demineralisation: Increased bone blood flow contributes to Charcot neuroarthropathy. [17]

Exam Detail: Molecular Mechanisms of Diabetic Neuropathy:

1. Polyol Pathway: Aldose reductase converts glucose → sorbitol → fructose within Schwann cells. Intracellular sorbitol accumulation causes osmotic stress, depletes myo-inositol, and reduces Na⁺/K⁺-ATPase activity, impairing nerve conduction.

2. AGE Formation: Non-enzymatic glycation of proteins produces irreversible advanced glycation end-products that bind to RAGE (receptor for AGE), triggering NF-κB activation and inflammatory cytokine release (TNF-α, IL-6), causing neuronal apoptosis.

3. Protein Kinase C (PKC) Activation: Hyperglycaemia activates diacylglycerol (DAG)-PKC pathway, increasing vascular permeability, reducing endoneurial blood flow, and promoting endothelial dysfunction.

4. Oxidative Stress: Mitochondrial electron transport chain overactivity generates reactive oxygen species (ROS), overwhelming endogenous antioxidant defences (glutathione, superoxide dismutase) and causing lipid peroxidation of neuronal membranes.

These pathways converge to produce axonal degeneration, segmental demyelination, and irreversible nerve fibre loss detectable on nerve conduction studies (reduced amplitudes, slowed velocities). [15]

2. Peripheral Arterial Disease (PAD) (The Healing Inhibitor)

A. Macrovascular Disease

Diabetes accelerates atherosclerosis with distinct features:

• Distal distribution: Preferentially affects tibial and peroneal arteries (below-knee disease), often sparing femoral-popliteal segments.
• Multisegmental occlusions: Multiple tandem lesions reducing collateral compensatory capacity.
• Medial arterial calcification (Mönckeberg sclerosis): Calcium deposition in the medial layer (distinct from intimal atherosclerotic calcification), rendering vessels incompressible and ABPI unreliable. [9]

Clinical consequence: Critical limb ischaemia (rest pain, tissue loss) develops when perfusion is insufficient for tissue healing. Transcutaneous oxygen tension (TcPO₂) less than 30 mmHg or toe pressure less than 30 mmHg predicts poor ulcer healing. [18]

B. Microvascular Dysfunction

Previously thought central, microvascular changes are now considered contributory rather than primary:

• Basement membrane thickening: Capillary basement membrane hypertrophy impairs oxygen diffusion.
• Endothelial dysfunction: Reduced nitric oxide bioavailability, increased endothelin-1 causing vasoconstriction.
• Impaired angiogenesis: Reduced VEGF responsiveness limiting compensatory neovascularisation. [19]

3. Biomechanical Abnormality and Repetitive Trauma

Plantar pressure distribution is the proximate cause of most neuropathic ulcers:

• Normal foot: Peak plantar pressure 200-400 kPa, evenly distributed across metatarsal heads.
• Diabetic neuropathic foot: Peak pressures exceed 1000-1200 kPa focally (metatarsal heads, hallux, heel).
• Callus formation: Repetitive stress induces hyperkeratotic callus, which itself acts as a "foreign body" increasing local pressure by 30%, causing subcutaneous haemorrhage and eventual skin breakdown. [16]

Common sites:

1. Plantar metatarsal heads (1st and 5th most common) - 60%
2. Plantar hallux - 15%
3. Heel - 15%
4. Dorsal interphalangeal joints (claw toes) - 10%

4. Infection and Impaired Immunity

Hyperglycaemia impairs host defences:

• Neutrophil dysfunction: Impaired chemotaxis, phagocytosis, and intracellular killing.
• Lymphocyte suppression: Reduced cell-mediated immunity.
• Vascular insufficiency: Reduced antibiotic penetration to infected tissue. [20]

Microbiology:

• Mild-moderate infections: Gram-positive cocci (Staphylococcus aureus, β-haemolytic streptococci).
• Severe/chronic infections: Polymicrobial (Gram-positives + Gram-negatives [Enterobacteriaceae, Pseudomonas] + anaerobes [Bacteroides, Peptostreptococcus]).
• Osteomyelitis: S. aureus predominates; MRSA increasingly prevalent in healthcare-associated cases. [21]

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4. Clinical Presentation

Ulcer Characteristics by Aetiology

A. Neuropathic Ulcer (50-60% of DFUs)

Site: Plantar surface at high-pressure points (metatarsal heads, hallux, heel, dorsal toe apices).

Appearance:

• "Punched-out" circular shape with well-defined edges.
• Deep penetration (often to tendon, joint capsule, or bone).
• Surrounded by thick hyperkeratotic callus rim.
• Base may have granulation tissue (if well-perfused) or slough.

Pain: Painless due to sensory neuropathy (critical diagnostic feature).

Pulses: Palpable, often bounding (autonomic shunting creates warm foot despite tissue hypoxia).

Skin: Dry, fissured (anhidrosis); warm to touch.

B. Neuro-Ischaemic Ulcer (30-40% of DFUs)

Site: Margins of foot (medial/lateral borders), toe tips, inter-digital spaces.

Appearance:

• Irregular, shallow ulcers with poorly defined edges.
• Sloughy or necrotic base (yellow/black eschar).
• Minimal or absent surrounding callus.
• Pale, dusky, or cyanotic peri-ulcer skin.

Pain: May be painful (if some sensory function preserved) or painless (if complete neuropathy).

Pulses: Absent or diminished. Foot cool, hairless, shiny skin.

Skin: Thin, shiny, hairless; dependent rubor; pallor on elevation.

C. Purely Ischaemic Ulcer (5-10% of DFUs)

Rare in diabetes (usually neuro-ischaemic). Painful, affecting toes/margins, with intact sensation and absent pulses.

Signs of Infection

Local Signs (modified by neuropathy and ischaemia):

• Purulent drainage from ulcer (most reliable sign).
• Erythema extending > 2 cm from ulcer edge.
• Warmth around ulcer (distinguish from Charcot foot or baseline autonomic changes).
• Swelling/induration of surrounding tissue.
• Foul odour (suggests anaerobic infection).
• Crepitus (gas gangrene - surgical emergency).
• Lymphangitis (red streaking) or lymphadenopathy (inguinal nodes).

Systemic Signs (often ABSENT in diabetics):

• Fever (present in less than 50% of infected DFUs). [8]
• Tachycardia.
• Hypotension (late sign of sepsis).
• Confusion/delirium (especially elderly).
• Unexplained hyperglycaemia may be the only sign of sepsis. [8]

Clinical Pearl: Deep plantar space infections may present with minimal superficial signs. Look for swelling of the dorsum of the foot (pus tracking along tendon sheaths), inability to dorsiflex toes, or "sausage toe" appearance.

Red Flag Features (Requiring Urgent Surgical Assessment)

1. Wet gangrene (ischaemic tissue + infection).
2. Gas in tissues (crepitus, gas on X-ray) - necrotising fasciitis.
3. Deep abscess (plantar space, flexor sheath).
4. Systemic sepsis (organ dysfunction).
5. Rapidly spreading cellulitis (limb-threatening).
6. Exposed bone/joint in ulcer base.

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5. Clinical Examination

Structured Foot Assessment ("3-Minute Foot Exam")

1. LOOK (Inspection)

Skin:

• Colour: Pallor (ischaemia), rubor (dependency, Charcot), cyanosis, necrosis.
• Integrity: Ulcers, fissures, blisters, callus.
• Dryness/scaling (anhidrosis).
• Previous amputation scars.

Deformity:

• Claw toes (MTP hyperextension + IP flexion).
• Hammer toes (PIP flexion).
• Hallux valgus/rigidus.
• Pes cavus (high arch).
• Charcot foot (rocker-bottom deformity, mid-foot collapse).
• Prominent metatarsal heads.

Nails: Onychomycosis, ingrown toenails, onychogryphosis.

Footwear: Inspect for foreign objects, areas of abnormal wear, inadequate cushioning.

2. FEEL (Palpation)

Temperature:

• Hot foot: Infection vs. Charcot neuroarthropathy vs. autonomic neuropathy.
• Cold foot: Ischaemia (PAD).
• Temperature gradient: Compare affected vs. contralateral foot. Difference > 2°C suggests Charcot or infection. [11]

Pulses:

• Dorsalis pedis (lateral to extensor hallucis longus tendon).
• Posterior tibial (posterior to medial malleolus).
• Popliteal, femoral (if foot pulses absent).
• Capillary refill time (> 2 seconds abnormal).

Oedema: Bilateral (cardiac/renal) vs. unilateral (infection, venous, Charcot).

3. TEST (Neurological and Vascular Assessment)

A. Sensory Neuropathy Testing

10g Semmes-Weinstein Monofilament (Gold standard screening):

• Test 10 sites on plantar surface (hallux, metatarsal heads 1-5, mid-foot, heel).
• Apply perpendicular pressure until filament bends; hold 2 seconds.
• Patient (eyes closed) reports when/where felt.
• Inability to feel at ≥1 site = Loss of Protective Sensation (LOPS). [14]

128 Hz Tuning Fork (vibration sense):

• Apply to bony prominence (hallux IP joint, medial malleolus).
• Loss indicates large-fibre neuropathy.

Pinprick (pain sensation): Disposable neurotip.

Proprioception: Move hallux up/down, patient identifies direction.

Ankle reflexes: Absent in peripheral neuropathy.

B. Vascular Assessment

Ankle-Brachial Pressure Index (ABPI):

• Interpretation:
  • 0.9-1.3: Normal.
  • 0.5-0.9: Mild-moderate PAD.
  • less than 0.5: Severe PAD/critical limb ischaemia.
  • "> 1.3: Unreliable (medial arterial calcification). [9]"
• Action: If ABPI > 1.3, proceed to TBPI or waveforms.

Toe-Brachial Pressure Index (TBPI):

• Photoplethysmography cuff on great toe.
• Normal: > 0.7.
• Abnormal: less than 0.7 (PAD); less than 0.3 (critical ischaemia, poor healing potential). [18]

C. Ulcer Probing

Probe-to-Bone Test:

• Use sterile blunt metal probe.
• Gently insert into debrided ulcer.
• Positive: Probe contacts hard, gritty bone.
• Sensitivity: 87%, Specificity: 83%, PPV: 89% for osteomyelitis. [6]

Ulcer Depth: Document in cm; photograph if possible.

4. CLASSIFY

Apply Wagner or University of Texas classification (see below).

Examination Pearls

Elevate the Red Hot Foot: If foot is erythematous and warm, elevate to 45° for 3-5 minutes. Charcot foot will blanch significantly; cellulitis remains red. [11]

Squeeze Test for Deep Infection: Gently squeeze metatarsal heads together (medial-lateral compression). Pain suggests deep plantar space infection or osteomyelitis.

Wagner "Sausage Toe": Fusiform swelling of entire toe indicates flexor sheath infection or phalangeal osteomyelitis.

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6. Investigations

Bedside Tests

Point-of-Care Glucose: Assess current glycaemic control; unexplained hyperglycaemia may indicate infection.

ABPI/TBPI: As above; TBPI is essential if ABPI > 1.3. [9]

Transcutaneous Oxygen Tension (TcPO₂):

• Measures oxygen partial pressure in dermal capillaries.
• Interpretation:
  • "> 40 mmHg: Good healing potential."
  • "30-40 mmHg: Marginal; consider revascularisation."
  • "less than 30 mmHg: Poor healing; revascularisation mandatory. [18]"

Skin Perfusion Pressure (SPP):

• Alternative to TcPO₂; > 40 mmHg predicts healing.

Laboratory Tests

Blood Tests:

• FBC: Leucocytosis (may be absent in diabetics). [8]
• CRP/ESR: Elevated in infection/osteomyelitis (CRP > 5 mg/L sensitive but non-specific).
• HbA1c: Long-term glycaemic control (target less than 7% [53 mmol/mol] for healing).
• Renal function (eGFR): Affects antibiotic dosing, prognosis.
• Albumin: Malnutrition impairs healing.

Blood Cultures: If systemic sepsis suspected (fever, tachycardia, hypotension).

Microbiology:

Deep Tissue Biopsy/Curettage (Gold Standard):

• After ulcer debridement, curette base to obtain tissue sample.
• Send for aerobic/anaerobic culture and sensitivity.
• Superior to swabs (which only capture surface colonisers). [21]

Wound Swab:

• Only if pus is expressible; otherwise unreliable.
• Predictive value limited (> 10⁵ organisms/g tissue indicates infection).

Bone Biopsy:

• If osteomyelitis suspected: obtain bone sample (percutaneous or intra-operative) for culture and histology (gold standard). [22]

Imaging

Plain Radiography (X-ray) of Foot

Indications: All diabetic foot ulcers (baseline assessment).

Findings:

• Osteomyelitis (appears after 2-4 weeks):
  • Cortical erosion.
  • Periosteal reaction.
  • Bone lysis.
  • Sequestrum (devascularised bone fragment).
• Gas in soft tissues: Radiolucent streaks (necrotising infection).
• Foreign body: Radiopaque objects.
• Charcot arthropathy: Fragmentation, subluxation, dislocation, sclerosis.

Sensitivity for osteomyelitis: 50-60% (low early in disease). [22]

Magnetic Resonance Imaging (MRI)

Indications:

• Suspected osteomyelitis (probe-to-bone positive, exposed bone, non-healing deep ulcer).
• Suspected deep soft tissue abscess.
• Pre-operative planning.

Findings:

• Osteomyelitis:
  • Bone marrow oedema (low T1, high T2/STIR signal).
  • Cortical destruction.
  • Soft tissue ulcer tract connecting to bone.
• Abscess: Rim-enhancing fluid collection.

Sensitivity: 90%, Specificity: 80% for osteomyelitis. [22]

Limitations: Cannot always distinguish acute Charcot from osteomyelitis (both show bone marrow oedema).

White Blood Cell Scan (Leukocyte Scintigraphy)

Indications: MRI contraindicated/unavailable; suspected osteomyelitis.

Method: ⁹⁹mTc-labelled leucocytes accumulate in infection.

Sensitivity: 74%, Specificity: 68% (lower than MRI). [22]

CT Scan

Indications: Gas gangrene assessment, pre-operative planning for Charcot reconstruction.

Advantages: Detects gas, bony anatomy.

Disadvantages: Inferior to MRI for osteomyelitis, soft tissue detail.

Vascular Imaging

Arterial Duplex Ultrasound

Indications: Absent pulses, TBPI less than 0.5, non-healing ischaemic ulcer.

Findings: Stenosis, occlusions, flow velocities.

Advantages: Non-invasive, no radiation/contrast.

Limitations: Operator-dependent; calcified vessels limit visualisation.

CT Angiography (CTA)

Indications: Pre-revascularisation planning.

Advantages: Rapid, detailed arterial anatomy (inflow, outflow).

Limitations: Nephrotoxic contrast (caution in renal impairment); calcification may obscure stenoses.

Magnetic Resonance Angiography (MRA)

Indications: Alternative to CTA if renal impairment prohibits iodinated contrast.

Advantages: No nephrotoxic contrast (gadolinium-based; avoid if eGFR less than 30).

Limitations: Overestimates stenoses; artefact from metallic clips.

Catheter Angiography

Gold Standard for arterial imaging; therapeutic (angioplasty/stenting) at same sitting.

Indications: Definitive pre-operative planning; simultaneous intervention.

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7. Classification Systems

Wagner Classification (1976)

Widely used, simple, but does not separately score infection or ischaemia.

Limitations: Does not separately assess ischaemia or infection severity.

University of Texas (UT) Classification (1996)

Two-dimensional system: Depth (0-3) × Ischaemia/Infection (A-D).

Better prognostic value than Wagner. [23]

Depth Grades:

• 0: Pre-ulcerative (healed ulcer site, high-risk foot).
• 1: Superficial (not involving tendon, capsule, or bone).
• 2: Deep to tendon or capsule.
• 3: Deep to bone or joint.

Modifiers:

• A: No infection, no ischaemia.
• B: Infection present.
• C: Ischaemia present (PAD).
• D: Both infection and ischaemia.

Example: UT 2B = Deep ulcer to tendon with infection, no ischaemia.

Prognostic utility: Stage 3D (deep ulcer with infection + ischaemia) has highest amputation risk. [23]

PEDIS Classification (IWGDF)

Perfusion, Extent, Depth, Infection, Sensation.

Used primarily in research; comprehensive assessment tool. [14]

IDSA/IWGDF Infection Severity Classification

Guides antibiotic therapy and need for surgical intervention. [21]

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8. Management

Management requires a multidisciplinary team (MDT) approach involving:

• Diabetologist/Endocrinologist
• Vascular surgeon
• Orthopaedic/Podiatric surgeon
• Specialist podiatrist
• Specialist nurse
• Orthotist
• Microbiologist
• Radiologist

Fundamental Principles: The "VIP" Approach

1. Vascular assessment and revascularisation if indicated.
2. Infection control (antibiotics, debridement, drainage).
3. Pressure offloading (total contact cast, therapeutic footwear).

Additional pillars:

• Glycaemic control (target HbA1c less than 7%).
• Wound care (debridement, moisture balance, dressings).
• Patient education (prevention strategies).

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A. Infection Management

1. Wound Debridement

Indications: All diabetic foot ulcers (remove necrotic tissue, callus, biofilm).

Technique:

• Sharp debridement: Scalpel removal of hyperkeratotic callus rim (reduces pressure by 30%), slough, necrotic tissue down to bleeding healthy tissue.
• Frequency: Weekly until ulcer healed.

Benefits:

• Reduces bacterial load.
• Removes pressure-inducing callus.
• Stimulates wound edge healing.
• Allows accurate depth assessment (probe-to-bone). [24]

2. Antibiotic Therapy

Indications: Clinical signs of infection (purulence, erythema > 2 cm, systemic signs).

Not indicated: Clean, uninfected ulcers (no evidence of benefit). [21]

Empirical Therapy (IDSA/IWGDF Guidelines): [21]

Osteomyelitis:

• Medical therapy: 6 weeks total (IV + oral); requires bone-penetrating agents.
  • "Options: Clindamycin, Ciprofloxacin, Rifampicin, Linezolid (MRSA)."
• Surgical therapy: Bone resection (digit amputation, metatarsal head resection, ray amputation) followed by 2-4 weeks antibiotics. [22]

De-escalation: Narrow spectrum based on deep tissue culture results.

3. Surgical Source Control

Indications:

• Deep abscess (plantar space, flexor sheath).
• Necrotising infection (gas gangrene).
• Wet gangrene.
• Osteomyelitis (if medical therapy fails or extensive bone involvement).

Procedures:

• Incision and drainage (I&D): Open deep abscesses; leave wound open (delayed closure).
• Debridement: Excise all necrotic, infected tissue.
• Digital amputation: Remove infected phalanx/toe.
• Ray amputation: Toe + metatarsal resection (preserves forefoot).
• Transmetatarsal amputation (TMA): Removes all toes and metatarsal heads; preserves heel for weight-bearing; requires Achilles lengthening to prevent equinus contracture.
• Major amputation (below-knee [BKA], above-knee [AKA]): For extensive gangrene, limb-threatening sepsis, non-reconstructable ischaemia. [25]

Surgical Pearl: Ray amputation of the 2nd/3rd/4th ray is biomechanically tolerated. Ray amputation of 1st or 5th ray creates imbalance; consider transmetatarsal amputation instead.

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B. Vascular Management (Revascularisation)

Indications:

• TBPI less than 0.5.
• TcPO₂ less than 30 mmHg.
• Non-healing ischaemic or neuro-ischaemic ulcer despite optimal offloading.
• Absent foot pulses with tissue loss. [26]

Principle: Restore pulsatile blood flow to foot to enable healing.

Endovascular Intervention

First-line for infrainguinal disease (tibial/peroneal arteries). [26]

Techniques:

• Balloon angioplasty: Dilation of stenotic segments.
• Stenting: Scaffolding to maintain patency (reserved for flow-limiting dissection or recoil).
• Atherectomy: Plaque excision (adjunct in heavily calcified lesions).

Outcomes:

• Technical success: 85-90%.
• Limb salvage at 1 year: 80-85%.
• Ulcer healing: 60-70% at 6 months. [26]

Advantages: Minimally invasive, local anaesthesia, rapid recovery.

Limitations: Restenosis (20-30% at 1 year); not suitable for long occlusions or poor distal targets.

Open Surgical Bypass

Indications:

• Long-segment occlusions not amenable to endovascular therapy.
• Failed endovascular intervention.
• No endovascular option (occluded tibial vessels, poor distal target).

Techniques:

• Femoral-popliteal bypass: For superficial femoral artery occlusion.
• Femoral-distal (tibial/pedal) bypass: For infra-popliteal disease; requires vein conduit (autologous saphenous vein gold standard).

Outcomes:

• 1-year patency: 70-80% (vein graft).
• Limb salvage: 85-90%. [26]

Disadvantages: General/regional anaesthesia; longer recovery; vein harvest site morbidity.

Hybrid Procedures

Combination of endovascular (iliac/femoral angioplasty) + open bypass (distal) to minimise surgical trauma.

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C. Pressure Offloading (The Cornerstone of Neuropathic Ulcer Healing)

Rationale: Repetitive plantar pressure prevents healing. Offloading reduces pressure by 80-90%, allowing re-epithelialisation. [10]

1. Total Contact Cast (TCC) - Gold Standard

Description: Non-removable, well-padded plaster/fibreglass cast extending from below knee to toes, moulded to foot contour to distribute pressure over entire plantar surface and lower leg.

Evidence: RCTs show 85-90% healing at 6-8 weeks, superior to all other offloading modalities. [27]

Mechanism:

• Distributes pressure over large surface area (reduces peak pressure by 85%).
• Forces compliance (patient cannot remove; ensures continuous offloading).
• Reduces oedema (compression effect).
• Limits ankle/foot motion.

Indications: Plantar neuropathic ulcers (Wagner 1-2, non-infected, non-ischaemic).

Contraindications:

• Active infection (prevents wound inspection).
• Critical ischaemia.
• Fragile skin (risk of cast-induced ulcer).
• Non-adherent patient (risk of falling).
• Charcot foot (acute phase - use total contact walker instead).

Complications: New ulcers (5-10% - requires skilled application), falls.

Application: Must be applied by trained practitioner; changed weekly or if cast loosens.

2. Removable Cast Walker (RCW) / "Moonboot"

Description: Pre-fabricated ankle-foot orthosis with rocker sole.

Evidence: Effective only if rendered irremovable (wrap with cohesive bandage). Otherwise, poor compliance (patients remove for > 50% of steps). [27]

Healing rate: 70-80% if compliance ensured (vs. 30-40% if removable).

Advantages: Easier to apply; allows wound inspection.

Disadvantages: Patient non-compliance if removable.

3. Therapeutic Footwear (Custom Shoes/Insoles)

Indications:

• Healed ulcer (secondary prevention).
• Deformities (claw toes, Charcot foot).
• High plantar pressures.

Features:

• Extra-depth toe box (accommodates deformities).
• Custom moulded insoles (redistribute pressure; reduce peak pressures by 30-50%).
• Rocker sole (reduces forefoot pressure during gait).

Evidence: Reduces ulcer recurrence by 50% vs. standard footwear. [28]

4. Felted Foam / Temporary Offloading

Indications: Interim measure until definitive offloading applied.

Technique: Adhesive felt pads (5-7 mm thick) around ulcer to offload pressure.

Limitations: Short-term only; requires frequent replacement.

5. Bed Rest / Non-Weight Bearing (NWB)

Indications: Acute infection, severe ischaemia, post-operative.

Limitations: Impractical long-term; deconditioning, thromboembolism risk.

---

D. Wound Care

Dressings

Principles:

• Maintain moist wound environment.
• Absorb exudate.
• Protect from trauma.
• No dressing type has proven superiority over simple saline gauze in diabetic foot ulcers. [29]

Common options:

• Saline gauze: Simple, inexpensive.
• Hydrocolloids: For light exudate, granulating wounds.
• Foam dressings: For moderate-heavy exudate.
• Antimicrobial dressings (silver, iodine): Limited evidence; consider if high bacterial load, but no substitute for systemic antibiotics.

Avoid: Povidone-iodine soaks (cytotoxic to fibroblasts), hydrogen peroxide (damages granulation tissue).

Negative Pressure Wound Therapy (NPWT)

Mechanism: Vacuum-assisted closure promotes granulation, reduces oedema, increases perfusion.

Indications: Post-surgical wounds (amputation sites), deep cavity wounds.

Evidence: Accelerates granulation; may reduce amputation rates in post-operative DFUs. [30]

Hyperbaric Oxygen Therapy (HBOT)

Mechanism: 100% oxygen at 2-3 atmospheres increases tissue oxygen tension.

Evidence: Moderate-quality evidence suggests reduced major amputation risk (NNT ~5) in Wagner 3-4 ulcers. [31]

Indications: Adjunct for non-healing Wagner 3-4 ulcers despite optimal therapy.

Limitations: Expensive, time-consuming (daily sessions for weeks), limited availability.

Contraindications: Untreated pneumothorax, concurrent bleomycin therapy.

Biological Therapies

Platelet-Derived Growth Factor (becaplermin gel): FDA-approved; modest benefit (10% absolute increase in healing). [29]

Bioengineered Skin Substitutes: Apligraf, Dermagraft - some RCT evidence of benefit, but high cost limits widespread use. [29]

---

E. Glycaemic Control

Target HbA1c: less than 7% (53 mmol/mol) for optimal healing. [32]

Rationale: Hyperglycaemia impairs:

• Neutrophil function.
• Collagen synthesis.
• Angiogenesis.
• Re-epithelialisation.

Caution: Avoid hypoglycaemia (risk of falls, impaired healing).

---

F. Multidisciplinary Foot Clinic

Evidence: Integrated MDT foot clinics reduce amputation rates by 50-85%. [33]

Components:

• Regular structured review (weekly for active ulcers).
• Rapid access to vascular/orthopaedic surgery.
• Podiatry-led debridement and offloading.
• Specialist nursing for wound care, education.
• Orthotist for custom footwear.

---

G. Management Algorithm (Flowchart)

┌─────────────────────────────────────────┐
│    DIABETIC FOOT ULCER PRESENTS         │
└─────────────────┬───────────────────────┘
                  │
                  ▼
┌─────────────────────────────────────────┐
│   ASSESS: "VIP"                         │
│   - Vascular (pulses, ABPI/TBPI)        │
│   - Infection (local/systemic signs)    │
│   - Pressure (neuropathy, callus)       │
│   + Depth, Classification               │
└─────────────────┬───────────────────────┘
                  │
        ┌─────────┴────────┬──────────────┐
        │                  │              │
        ▼                  ▼              ▼
┌──────────────┐   ┌──────────────┐   ┌──────────────┐
│ ISCHAEMIC?   │   │ INFECTED?    │   │ NEUROPATHIC? │
│ (PAD)        │   │              │   │ (No PAD/     │
│              │   │              │   │  infection)  │
└──────┬───────┘   └──────┬───────┘   └──────┬───────┘
       │                  │                  │
       ▼                  ▼                  ▼
┌──────────────┐   ┌──────────────┐   ┌──────────────┐
│ VASCULAR     │   │ INFECTION    │   │ OFFLOADING   │
│ REFERRAL     │   │ CONTROL      │   │              │
│              │   │              │   │              │
│ • Duplex     │   │ • Debridement│   │ • TCC        │
│ • CTA/MRA    │   │ • Deep tissue│   │   (Gold Std) │
│ • Angioplasty│   │   culture    │   │ • RCW        │
│   / Stent    │   │ • Antibiotics│   │ • Custom     │
│ • Bypass     │   │   (IDSA/IWGDF│   │   footwear   │
│              │   │   guidelines) │   │ • Debride    │
│ Target:      │   │ • I&D abscess│   │   callus     │
│ TBPI > 0.5    │   │ • Amputation │   │              │
│ TcPO₂ > 30    │   │   (if osteo/ │   │              │
│              │   │   gangrene)  │   │              │
└──────┬───────┘   └──────┬───────┘   └──────┬───────┘
       │                  │                  │
       └─────────┬────────┴──────────────────┘
                 │
                 ▼
┌─────────────────────────────────────────┐
│   ADJUNCTS (All Ulcers)                 │
│   • Glycaemic control (HbA1c less than 7%)       │
│   • Wound dressings (moist environment) │
│   • Nutrition (protein, micronutrients) │
│   • Patient education (foot care)       │
│   • Weekly review until healed          │
│   • Consider: NPWT, HBOT (severe cases) │
└─────────────────────────────────────────┘
                 │
                 ▼
┌─────────────────────────────────────────┐
│   MONITOR HEALING                       │
│   • Expected: 50% size reduction in 4 wk│
│   • If not improving: Re-assess VIP     │
│     - Check offloading compliance       │
│     - Repeat vascular studies           │
│     - Consider occult infection/osteo   │
│     - Consider adjunct therapies        │
└─────────────────┬───────────────────────┘
                  │
        ┌─────────┴─────────┐
        │                   │
        ▼                   ▼
  ┌──────────┐        ┌──────────┐
  │  HEALED  │        │ AMPUTATION│
  │          │        │ (if failed│
  │ Prevent  │        │  healing, │
  │ recur:   │        │  gangrene,│
  │ • Custom │        │  sepsis)  │
  │   shoes  │        └───────────┘
  │ • Podiatry│
  │ • Monitor│
  └──────────┘

---

9. Complications

A. Infection-Related

B. Vascular-Related

C. Amputation

Post-amputation outcomes: [25]

• Contralateral amputation at 5 years: 50-70%.
• Prosthetic use: BKA 60-80%; AKA 30-50%.
• Return to independent ambulation: BKA 50-70%; AKA 20-30%.

D. Charcot Neuroarthropathy

Incidence: 0.5-2% of diabetics with neuropathy. [11]

Pathophysiology: Acute inflammatory bone destruction in insensate foot; exact mechanism unclear (neurovascular theory, neurotraumatic theory).

Presentation: Red, hot, swollen foot mimicking cellulitis or gout. Often precipitated by minor trauma.

Key distinction from cellulitis:

• Charcot: Bounding pulses, redness fades on elevation, ± deformity, X-ray shows fractures/subluxation.
• Cellulitis: Redness persists on elevation, may have ulcer/portal of entry, systemic signs.

Management:

• Acute phase: STRICT non-weight bearing, total contact walker (cast if no ulcer), until "cooling" (temperature difference less than 2°C vs. contralateral foot).
• Chronic phase: Custom moulded ankle-foot orthosis (AFO) or bespoke footwear.
• Surgical: Reconstruction if severe deformity prevents bracing (realignment arthrodesis).

Consequence of missed diagnosis: Progressive collapse → rocker-bottom deformity → ulceration at apex → amputation.

---

10. Prognosis

Natural History

Untreated DFU: Progression to infection (30-50%), gangrene (10-20%), amputation (5-15%). [1]

With optimal MDT care: Healing in 60-80% within 12-20 weeks. [33]

Healing Rates by Classification

Recurrence

40% of healed ulcers recur within 1 year; 65% within 5 years. [7]

Predictors of recurrence:

• Previous ulcer/amputation.
• Persistent foot deformity.
• Inability to use custom footwear.
• Poor glycaemic control (HbA1c > 8%).
• Continued smoking.

Mortality

Diabetic foot complications carry significant mortality:

Mortality exceeds that of many common cancers (breast, colon, prostate). [3]

Causes of death: Cardiovascular disease (MI, stroke) accounts for 50-60%; sepsis 10-15%; renal failure 10%.

Prognostic Factors for Healing

Favourable:

• Small ulcer (less than 1 cm²).
• Superficial (Wagner 1).
• Short duration (less than 3 months).
• Palpable pulses (TBPI > 0.7).
• No infection.
• Good glycaemic control (HbA1c less than 7%).
• Adherence to offloading.

Unfavourable:

• Large ulcer (> 2 cm²).
• Deep (Wagner ≥2, probe-to-bone positive).
• Long duration (> 6 months).
• PAD (TBPI less than 0.5).
• Infection/osteomyelitis.
• Poor glycaemic control (HbA1c > 9%).
• Non-adherence to treatment.

50% size reduction at 4 weeks is a validated predictor of eventual healing (sensitivity 75%, specificity 70%). [34]

---

11. Prevention and Screening

Primary Prevention (All Diabetics)

Education:

• Daily foot inspection (use mirror for plantar surface).
• Never walk barefoot (indoors or outdoors).
• Wash feet daily; dry thoroughly (especially between toes).
• Moisturise (avoid between toes - maceration risk).
• Trim nails straight across; file sharp edges.
• Check inside shoes for foreign objects before wearing.
• Avoid tight socks/shoes.
• Avoid heating pads (burn risk if neuropathic).

Footwear:

• Well-fitting, cushioned shoes (avoid pointed toes, high heels).
• Seamless socks (avoid constricting bands).
• Break in new shoes gradually.

Glycaemic control: HbA1c less than 7% reduces microvascular complications (including neuropathy). [32]

Smoking cessation: Reduces PAD progression.

Podiatry: Regular nail care, callus removal (self-treatment with blades contraindicated).

Secondary Prevention (High-Risk Foot)

Risk Stratification (IWGDF): [14]

Interventions for high-risk patients:

• Custom therapeutic footwear: Reduces recurrence by 50%. [28]
• Prophylactic surgery: Consider correction of severe deformities (hallux valgus, hammer toes) to reduce pressure points.
• Home temperature monitoring: Daily infrared thermometry of plantar foot; temperature difference > 2.2°C (compared to contralateral site) predicts inflammation/pre-ulceration. Alerts patient to reduce activity until normalises. Reduces ulcer incidence by 70%. [35]

Tertiary Prevention (Post-Ulcer Healing)

Lifelong custom footwear: Mandatory.

Regular podiatry: Monthly callus debridement.

Patient education: Recognise early signs (redness, warmth, swelling, blister, callus).

Immediate access pathway: Rapid MDT review if new lesion detected (less than 24-48 hours).

---

12. Key Guidelines

International Working Group on the Diabetic Foot (IWGDF) 2023 Guidelines [14]

Key Recommendations:

• Screening: Annual foot examination for all diabetics (10g monofilament, pulses, deformity).
• Classification: Use PEDIS or UT classification for prognostication.
• Offloading: Non-removable knee-high device (TCC or irremovable walker) for plantar neuropathic ulcers.
• Infection: Antibiotic therapy only for infected ulcers; duration based on severity (1-2 weeks mild, 2-3 weeks moderate, 3-4 weeks severe, 6 weeks osteomyelitis).
• Revascularisation: For ischaemic ulcers (TBPI less than 0.5 or TcPO₂ less than 30 mmHg).

NICE NG19: Diabetic Foot Problems (2015, updated 2020) [36]

Key Recommendations:

• Multidisciplinary foot protection service for all high-risk patients.
• Refer to multidisciplinary foot care service within 24 hours if acute foot problem (new ulcer, swelling, discolouration).
• Refer to vascular service within 1 week if absent pulses.
• Use removable cast walker rendered irremovable if TCC unavailable.
• Consider NPWT for post-operative dehiscence or large cavity wounds.

IDSA Clinical Practice Guideline for Diabetic Foot Infections (2012) [21]

Key Recommendations:

• Diagnose infection clinically (≥2 signs: purulence, erythema, warmth, pain, induration).
• Obtain deep tissue or bone cultures (not swabs).
• Empirical therapy based on severity (mild, moderate, severe).
• Osteomyelitis: 6 weeks antibiotics if no residual dead bone; shorter duration if bone resected.

---

13. Common Exam Questions and Model Answers

Question 1: "A 62-year-old man with 15-year history of type 2 diabetes presents with a painless ulcer on the plantar surface of his right foot under the 1st metatarsal head. How would you assess and manage this patient?"

Model Answer:

"This presentation suggests a diabetic neuropathic foot ulcer. I would approach this systematically using the 'VIP' framework: Vascular assessment, Infection assessment, and Pressure offloading.

History: I would ask about:

• Duration of ulcer, previous ulcers or amputations.
• Symptoms of infection (discharge, odour, systemic symptoms).
• Claudication, rest pain (vascular symptoms).
• Glycaemic control, smoking.

Examination:

• Look: Ulcer site, depth, surrounding callus, signs of infection (erythema > 2 cm, purulence).
• Feel: Pulses (dorsalis pedis, posterior tibial), temperature (hot = infection/Charcot; cold = ischaemia).
• Test: 10g monofilament (likely loss of protective sensation), probe-to-bone test (assess osteomyelitis), ABPI (may be falsely elevated; proceed to TBPI if > 1.3).

Investigations:

• Bedside: TBPI, wound swab if purulent.
• Bloods: HbA1c, FBC, CRP, renal function.
• Imaging: X-ray foot (osteomyelitis, gas, foreign body); MRI if probe-to-bone positive.
• Vascular: Arterial duplex if absent pulses or TBPI less than 0.5.

Classification: Likely Wagner Grade 1-2 (or UT 1A/2A if no infection/ischaemia).

Management:

1. Offloading: Total contact cast (gold standard for plantar neuropathic ulcers) or irremovable cast walker. This is the single most important intervention.
2. Debridement: Sharp debridement of callus and any necrotic tissue.
3. Infection control: Only if signs of infection - deep tissue culture, then antibiotics per IDSA guidelines (e.g., flucloxacillin if mild).
4. Vascular: If TBPI less than 0.5 or absent pulses, urgent vascular referral for revascularisation.
5. Glycaemic control: Target HbA1c less than 7%.
6. Multidisciplinary: Refer to diabetic foot MDT for coordinated care.
7. Wound care: Moist dressings; no specific dressing type proven superior.
8. Follow-up: Weekly review until healed (expect 50% size reduction at 4 weeks; if not, reassess).

Prevention of recurrence (once healed):

• Custom therapeutic footwear with moulded insoles.
• Regular podiatry (callus removal).
• Patient education (daily foot checks, never barefoot)."

---

Question 2: "What is the probe-to-bone test and what is its significance?"

Model Answer:

"The probe-to-bone test is a simple bedside clinical test to assess for underlying osteomyelitis in a diabetic foot ulcer.

Technique:

• After wound debridement, insert a sterile blunt metal probe gently into the ulcer.
• If the probe contacts hard, gritty bone, the test is positive.

Significance:

• High positive predictive value (> 90%) for osteomyelitis. [6]
• Sensitivity: 87%, Specificity: 83%.
• Guides need for further imaging (MRI) and treatment (prolonged antibiotics vs. surgical bone resection).

Clinical application:

• If probe-to-bone positive → assume osteomyelitis → order MRI for confirmation and extent → treat with 6 weeks bone-penetrating antibiotics (e.g., clindamycin, ciprofloxacin, rifampicin) OR surgical bone debridement/amputation.

This is a key examination skill for MRCP and surgical exams."

---

Question 3: "Why is ABPI unreliable in diabetic patients and what alternative do you use?"

Model Answer:

"ABPI is unreliable in diabetic patients due to medial arterial calcification (Mönckeberg sclerosis).

Mechanism:

• Chronic hyperglycaemia causes calcium deposition in the medial layer of arterial walls.
• This makes vessels incompressible (stiff pipes).
• The blood pressure cuff cannot occlude the artery, resulting in falsely elevated ABPI readings (typically > 1.3, sometimes > 1.5).

Clinical consequence:

• ABPI > 1.3 suggests medial calcification and is non-diagnostic for PAD.
• A diabetic patient with ABPI 1.4 may still have significant arterial stenoses.

Alternative: Toe-Brachial Pressure Index (TBPI)

• Digital arteries are spared from medial calcification.
• Measured using photoplethysmography cuff on great toe.
• Interpretation:
  • "Normal: > 0.7."
  • "PAD: less than 0.7."
  • "Critical ischaemia (poor healing): less than 0.3. [18]"
• TBPI is the gold standard non-invasive vascular assessment in diabetics.

Adjuncts:

• Pulse volume waveforms (qualitative assessment).
• Transcutaneous oxygen tension (TcPO₂): less than 30 mmHg predicts poor healing.
• Arterial duplex ultrasound or CTA/MRA for anatomical assessment."

---

Question 4: "What are the indications for revascularisation in a diabetic foot ulcer?"

Model Answer:

"Revascularisation is indicated for ischaemic or neuro-ischaemic ulcers where impaired perfusion prevents healing.

Indications:

• TBPI less than 0.5 (or ABPI less than 0.5 if reliable).
• TcPO₂ less than 30 mmHg (critical ischaemia; poor healing potential). [18]
• Absent foot pulses with tissue loss (ulcer or gangrene).
• Non-healing ulcer despite optimal offloading and wound care, with evidence of PAD.

Goal: Restore pulsatile blood flow to foot to enable ulcer healing and limb salvage.

Methods:

1. Endovascular (first-line): [26]

   • Angioplasty ± stenting of tibial/peroneal arteries.
   • Advantages: Minimally invasive, local anaesthesia, rapid recovery.
   • Outcomes: 85-90% technical success; 80-85% limb salvage at 1 year.

2. Open bypass:

   • Indications: Long occlusions, failed endovascular, no endovascular option.
   • Femoral-distal bypass using autologous vein (saphenous vein gold standard).
   • Outcomes: 70-80% 1-year patency; 85-90% limb salvage.

Post-revascularisation:

• Continue offloading, wound care, glycaemic control.
• Antiplatelet therapy (aspirin or clopidogrel) to maintain patency.
• Monitor for re-stenosis (duplex surveillance).

Evidence: Revascularisation increases healing rates from 30-40% to 60-80% in ischaemic ulcers. [26]"

---

Question 5: "Describe the difference between Charcot foot and cellulitis in a diabetic patient."

Model Answer:

"Both present as a red, hot, swollen foot, but distinguishing them is critical as management differs completely.

Key Clinical Test: Elevate the leg to 45° for 5 minutes:

• Charcot: Redness substantially fades (congestion drains).
• Cellulitis: Redness persists (inflammation).

Management:

• Charcot: Total contact walker, strict non-weight bearing, immobilisation until 'cooling' (temperature normalises). Missed diagnosis → rocker-bottom deformity → amputation.
• Cellulitis: Antibiotics, wound care, treat underlying ulcer.

Both can coexist: If doubt, treat as both until imaging clarifies."

---

14. Viva Points

Viva Point: Opening Statement: "Diabetic foot ulcer is a full-thickness wound below the ankle in a patient with diabetes, resulting from the triad of peripheral neuropathy, peripheral arterial disease, and biomechanical deformity. It affects 15-25% of diabetics during their lifetime and accounts for 85% of diabetes-related lower extremity amputations. Five-year mortality following major amputation is 50-70%, comparable to many malignancies."

Key Facts to Mention:

• Lifetime risk 25%; annual incidence 2-4%. [2]
• Three pathophysiological pillars: neuropathy (sensory/motor/autonomic), ischaemia (macrovascular tibial disease + medial calcification), infection (impaired immunity).
• Assessment framework: VIP = Vascular (TBPI, not ABPI), Infection (probe-to-bone test PPV > 90%), Pressure (offloading).
• Classification: Wagner (0-5 depth-based) vs. UT (depth × infection/ischaemia matrix - better prognosis).
• Management: Total contact cast (gold standard offloading, 85-90% healing), revascularisation (if TBPI less than 0.5), antibiotics (only if infected, per IDSA guidelines), debridement, glycaemic control (HbA1c less than 7%).
• Osteomyelitis: 6 weeks antibiotics OR bone resection + 2-4 weeks antibiotics. [22]
• Prevention: Custom footwear reduces recurrence by 50%. [28]
• MDT foot clinics reduce amputation rates by 50-85%. [33]

Common Examiner Questions:

1. "Why is ABPI unreliable?" → Medial arterial calcification; use TBPI.
2. "What is probe-to-bone test?" → Bedside test; PPV > 90% for osteomyelitis.
3. "What is the gold standard offloading?" → Total contact cast (non-removable).
4. "How do you distinguish Charcot from cellulitis?" → Elevate leg; Charcot fades, cellulitis persists.
5. "What are indications for revascularisation?" → TBPI less than 0.5, TcPO₂ less than 30 mmHg, absent pulses with tissue loss.

---

15. Patient/Layperson Explanation

What is a Diabetic Foot Ulcer?

A diabetic foot ulcer is a sore or wound on the foot that develops in people with diabetes. It happens because diabetes can damage the nerves and blood vessels in your feet over time.

Why Does It Happen?

Three main reasons:

1. Nerve Damage (Neuropathy): You lose feeling in your feet. You might step on a stone, get a blister from tight shoes, or burn your foot without realising it. Because there's no pain, you keep walking on the injury and it gets worse.

2. Poor Blood Flow: Diabetes can narrow the blood vessels in your legs. This means less blood reaches your feet to help wounds heal.

3. Infection: High blood sugar makes it harder for your body to fight germs. Bacteria can get into the wound and cause infection.

Why Is It Dangerous?

• Diabetic foot ulcers heal very slowly or sometimes not at all.
• Infection can spread to the bone.
• Without treatment, gangrene (dead tissue) can develop, which may require amputation (surgical removal of the toe, foot, or leg).
• People with diabetic foot problems have a higher risk of serious illness and early death, mainly from heart disease.

What Are the Warning Signs?

• Any break in the skin on your foot (cut, blister, sore).
• Redness, warmth, or swelling.
• Discharge or bad smell from a wound.
• Black or discoloured tissue.
• Pain (though you might not feel pain if you have nerve damage).
• Unexplained high blood sugar levels.

If you notice any of these, see your doctor or foot specialist immediately (ideally within 24-48 hours).

What Is the Treatment?

Treatment depends on the severity:

1. Taking Pressure Off the Wound:

   • You'll need a special boot or plaster cast to stop you putting weight on the ulcer.
   • Walking on the wound prevents it healing - this is the most important part of treatment.

2. Cleaning the Wound:

   • A specialist nurse or podiatrist will remove dead skin and hard skin (callus) around the ulcer.
   • You'll need special dressings to keep the wound clean and moist.

3. Treating Infection:

   • If the ulcer is infected, you'll need antibiotics (tablets or sometimes through a drip).
   • Deep infections may need surgery to drain pus.

4. Improving Blood Flow:

   • If blood flow is poor, you may need a procedure to open blocked arteries (angioplasty - a small balloon is used to widen the artery).
   • Sometimes a bypass operation is needed (using a vein to go around the blockage).

5. Controlling Your Diabetes:

   • Keeping your blood sugar levels as close to normal as possible helps healing.
   • Your diabetes team will work with you to adjust your medications.

6. In Severe Cases:

   • If the infection is very bad or tissue has died, surgery may be needed to remove part of the toe or foot (amputation). This is done to save your life and the rest of your leg.

How Can I Prevent a Diabetic Foot Ulcer?

Check Your Feet Every Day:

• Look for cuts, blisters, red areas, swelling, or nail problems.
• Use a mirror to check the soles of your feet if you can't see them easily.

Protect Your Feet:

• Never walk barefoot - not even at home.
• Wear well-fitting, comfortable shoes (no pointed toes or high heels).
• Check inside your shoes for stones or rough areas before putting them on.
• Wear clean, dry socks every day (avoid tight elastic bands).

Care for Your Feet:

• Wash your feet every day with warm (not hot) water and mild soap.
• Dry thoroughly, especially between the toes.
• Moisturise your feet (but not between the toes).
• Cut your toenails straight across; file sharp edges. If you can't see well or reach your feet, see a podiatrist.

See a Podiatrist Regularly:

• If you have high-risk feet (nerve damage, poor circulation, previous ulcer), you should see a foot specialist every 1-3 months.
• They'll cut your nails, remove hard skin, and check for problems.

Control Your Diabetes:

• Take your medications as prescribed.
• Aim for HbA1c less than 7% (your doctor will check this with a blood test).
• Eat a healthy diet and stay active (as advised by your diabetes team).

Don't Smoke:

• Smoking makes blood flow worse and slows healing.

See Your Doctor Quickly:

• If you notice any problem with your feet, see your GP or diabetes nurse within 24-48 hours. Early treatment can prevent serious complications.

What Happens After the Ulcer Heals?

• You'll need to wear special shoes with custom insoles for the rest of your life to prevent another ulcer.
• Continue seeing your podiatrist regularly.
• Keep checking your feet every day.
• Important: Ulcers often come back (40% within a year), so prevention is lifelong.

Key Message

Diabetic foot ulcers are serious but often preventable. Daily foot checks, proper footwear, and good diabetes control are your best protection. If you develop a sore, seek help immediately - early treatment can save your foot and your life.

---

16. References

1. Armstrong DG, Boulton AJM, Bus SA. Diabetic foot ulcers and their recurrence. N Engl J Med. 2017;376(24):2367-2375. doi:10.1056/NEJMra1615439

2. Zhang P, Lu J, Jing Y, et al. Global epidemiology of diabetic foot ulceration: a systematic review and meta-analysis. Ann Med. 2017;49(2):106-116. doi:10.1080/07853890.2016.1231932

3. Armstrong DG, Swerdlow MA, Armstrong AA, et al. Five year mortality and direct costs of care for people with diabetic foot complications are comparable to cancer. J Foot Ankle Res. 2020;13:16. doi:10.1186/s13047-020-00383-2

4. Monteiro-Soares M, Russell D, Boyko EJ, et al. Guidelines on the classification of diabetic foot ulcers (IWGDF 2019). Diabetes Metab Res Rev. 2020;36 Suppl 1:e3273. doi:10.1002/dmrr.3273

5. Boulton AJM, Vileikyte L, Ragnarson-Tennvall G, Apelqvist J. The global burden of diabetic foot disease. Lancet. 2005;366(9498):1719-1724. doi:10.1016/S0140-6736(05)67698-2

6. Grayson ML, Gibbons GW, Balogh K, et al. Probing to bone in infected pedal ulcers: a clinical sign of underlying osteomyelitis in diabetic patients. JAMA. 1995;273(9):721-723. doi:10.1001/jama.1995.03520330051036

7. Dubsky M, Jirkovska A, Bem R, et al. Risk factors for recurrence of diabetic foot ulcers: prospective follow-up analysis in the Eurodiale subgroup. Int Wound J. 2013;10(5):555-561. doi:10.1111/j.1742-481X.2012.01022.x

8. Lipsky BA, Berendt AR, Cornia PB, et al. 2012 Infectious Diseases Society of America clinical practice guideline for the diagnosis and treatment of diabetic foot infections. Clin Infect Dis. 2012;54(12):e132-e173. doi:10.1093/cid/cis346

9. Williams DT, Harding KG, Price P. An evaluation of the efficacy of methods used in screening for lower-limb arterial disease in diabetes. Diabetes Care. 2005;28(9):2206-2210. doi:10.2337/diacare.28.9.2206

10. Bus SA, van Deursen RW, Armstrong DG, et al. Footwear and offloading interventions to prevent and heal foot ulcers and reduce plantar pressure in patients with diabetes: a systematic review. Diabetes Metab Res Rev. 2016;32 Suppl 1:99-118. doi:10.1002/dmrr.2702

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