Diabetic Foot

Overview

Pathophysiology - The Triad

1. Peripheral Neuropathy

• Multifactorial: both vascular and metabolic roots
• Hyperglycemia causes glycosylation of hemoglobin and proteins, forming advanced glycation end products (AGEs) that precipitate in small vessel walls and nerve tissue
• Results in thickening of basement membranes, reduced endothelial nitric oxide activity, and epineural vessel atherosclerosis
• Metabolic causes: sorbitol accumulation, enzyme deficiencies, increased oxygen-free radical activity
• Consequences:
  • Sensory neuropathy: loss of protective sensation (LOPS) - the pivotal defect; patient is unaware of injury
  • Motor neuropathy: intrinsic muscle weakness, overpowered by extrinsic muscles → hammer toes, claw toes, distal migration of the fat pad, gastrosoleus contracture increasing forefoot pressure
  • Autonomic neuropathy: absent skin oils → skin fissuring; decreased sweating → dry, cracked skin
• Inability to feel a Semmes-Weinstein 5.07 monofilament (10 g pressure) is the most predictive risk factor for foot morbidity
• Campbell's Operative Orthopaedics 15th Ed 2026

2. Peripheral Arterial Disease (Ischemia)

• Diabetic patients are twice as likely to develop peripheral arterial disease and 9 times more likely to develop a foot ulcer when PAD coexists
• Macro- and microvascular insufficiency combine: thickened basement membranes, medial calcinosis (arterial calcification), endothelial dysfunction
• Characteristically affects tibial and peroneal vessels (infrapopliteal)
• ABI is a useful screening tool: normal 0.9-1.2; values >1.3 suggest non-compressible calcified vessels; ABI <0.5 predicts poor healing without vascular intervention
• Absolute toe pressures >70 mm Hg needed for healing; toe-brachial index (TBI) more reliable than ABI when vessels are calcified
• Campbell's Operative Orthopaedics 15th Ed 2026

3. Infection

• Infection begins with bacterial invasion of compromised tissues and rapidly spreads to deep structures
• Immunosuppression in diabetes: altered chemotaxis and cell-wall abnormalities of polymorphonuclear cells
• Most mild infections: gram-positive cocci (S. aureus, streptococci)
• Severe/deep infections: polymicrobial - aerobic gram-positive cocci + gram-negative bacilli + anaerobes
• Pseudomonas is over-represented; empirical therapy for severe infections should cover it
• Bailey and Love's Short Practice of Surgery 28th Ed

Classification Systems

Wagner Classification (most widely used)

WIfI Classification (Society for Vascular Surgery - preferred for threatened limb)

• W - Wound
• I - Ischemia
• fI - foot Infection

University of Texas Classification

• Neuropathic (pure neuropathy, good blood supply)
• Ischemic (PAD-driven, neurologically intact)
• Neuroischemic (combined - most common and most dangerous)

Clinical Assessment

History

• Duration of diabetes, glycemic control (HbA1c)
• Episodes of prior ulceration, prior amputations
• Symptoms of claudication or rest pain
• Impaired vision, renal disease, paresthesias/numbness
• Note: impaired sensation means patients often deny pain or history of trauma

Physical Examination (Box 91.1 from Campbell's)

• Undersized shoes → pressure over bony prominences
• Abnormal wear pattern → structural/dynamic deformity
• Prominent seams or foreign bodies patient cannot feel → confirms neuropathy

• Atrophy of extensor digitorum brevis → motor neuropathy
• Claw/hammer toes, foot drop → motor neuropathy
• Corns and calluses → precursors to ulceration
• Arch and hindfoot alignment

• Dry, fissured skin (autonomic neuropathy)
• Warmth and erythema (infection or Charcot)
• Dependent rubor (ischemia)

• 10-g Semmes-Weinstein monofilament at 10 sites (or 4.5-g beneath both first metatarsal heads for quicker screening)
• Pinprick, temperature, vibration, proprioception

• Pedal pulse assessment (may be unreliable due to calcification)
• ABI / toe-brachial index
• Ankle and toe pressures

Wound Assessment

• Debride callus first to expose true wound dimensions
• Probe to bone with sterile cotton swab (positive "probe-to-bone" test = high PPV for osteomyelitis)
• Assess for depth, tunneling, undermining, exudate
• Three-view foot X-ray for all patients: foreign bodies, soft tissue gas, bone abnormalities, Charcot deformity, prior amputations

Investigations

Management

General Principles (the pillars)

1. Glycemic control
2. Off-loading / pressure relief
3. Wound debridement
4. Infection control and antibiotics
5. Vascular assessment and revascularization
6. Appropriate footwear

Off-loading

• Total contact cast (TCC): gold standard for neuropathic plantar ulcers
• Removable cast walkers, walking braces, custom therapeutic footwear
• Strict non-weight-bearing for moderate-to-severe infections

Debridement

• Sharp debridement of all hypertrophic callus and non-viable tissue
• Goal: convert chronic wound to acute wound capable of healing
• Saline irrigation (avoid hydrogen peroxide, betadine - damage viable tissue)
• In OR for deeper/infected wounds
• For osteomyelitis: surgical resection of infected bone preferred

Antibiotics (by severity)

• Culture-specific antibiotics preferred once results available
• Simple toe amputations: 2-week oral course
• Partial ray amputation/metatarsal resection: 4-6 week prolonged course
• Rosen's Emergency Medicine, Current Surgical Therapy 14e, Bailey and Love's 28th Ed

Wound Care Products

• Advanced dressings (hydrocolloid, alginate, foam, silver-containing)
• Negative pressure wound therapy (NPWT): evidence supports use for diabetic foot ulcers; meta-analysis (PMID 39241769) confirms effectiveness in promoting healing
• Biological/dermal substitutes (e.g., Integra) for complex wounds after debridement

Vascular Intervention

• Full vascular assessment mandatory in patients with absent pulses or non-healing wounds
• Angioplasty or bypass surgery to improve distal vascularity before or alongside foot surgery
• Hyperbaric oxygen therapy (HBO): for Wagner grade 3+ with inadequate perfusion; shown 54% healing vs. 25% with standard methods; indicated for osteomyelitis, gangrene, or open wound with inadequate perfusion not amenable to revascularization

Surgical Treatment by Wagner Grade

Amputation

• Wound healing after amputation in diabetics is unreliable
• Excision must be adequate to remove all infected tissue; excess bone resected for tension-free closure
• If extensive peripheral neuropathy, below-knee amputation in area with better sensation may be preferable
• Up to one-third of patients with deep/limb-threatening infection eventually undergo amputation

Charcot Neuropathic Arthropathy (Charcot Foot)

• Acute phase: warm, swollen, erythematous foot; often mistaken for infection or DVT
• Chronic/collapsed phase: midfoot collapse ("rocker-bottom deformity"), bony prominences → ulceration risk
• MRI and bone scan for diagnosis; plain X-rays show fragmentation, subluxation, destruction
• Management: strict off-loading in TCC until acute inflammation subsides (can take 3-12 months); surgical reconstruction for unstable or deformity-causing cases

Prevention

• Daily foot inspection (patient + carer)
• Therapeutic footwear: adequate toe box, no prominent seams, custom insoles
• Regular foot care by podiatrist
• Glycemic control: lower HbA1c = less peripheral neuropathy and fewer ulcers
• Annual monofilament screening of all diabetic patients
• Education on risk factors, proper nail care, avoiding barefoot walking
• Multidisciplinary diabetic foot clinic: demonstrated to reduce LEA rates through early recognition and management

Key Points Summary

• The triad of neuropathy + ischemia + infection drives nearly all diabetic foot complications
• Sensory loss is the pivotal defect - it removes the protective "alarm" of pain
• Wagner classification guides treatment decisions; WIfI better predicts limb threat
• MRI is the most sensitive modality for osteomyelitis
• Superficial swabs are unreliable - use deep tissue/bone cultures
• Total contact casting is the gold standard for off-loading neuropathic ulcers
• Severe infections: broad-spectrum IV antibiotics (pip-tazo + vancomycin ± metronidazole)
• Vascular assessment is mandatory - revascularize before/alongside wound management when possible
• Multidisciplinary care reduces amputation rates

• Campbell's Operative Orthopaedics 15th Ed 2026, Ch. 91
• Bailey and Love's Short Practice of Surgery 28th Ed, Ch. 43
• Current Surgical Therapy 14e, Diabetic Foot chapter
• Rosen's Emergency Medicine, Ch. 115 / 125
• Recent evidence: NPWT meta-analysis, 2024, PMID 39241769 | Advanced wound dressings meta-analysis, 2024, PMID 38864979