What are the types of diabetic foot ulcers?

Types of Diabetic Foot Ulcers

Diabetic foot ulcers are classified into three main types based on their underlying pathophysiology: neuropathic (50% of cases), ischemic (15% of cases), and neuro-ischemic (35% of cases). 1, 2

Primary Classification by Etiology

Neuropathic Ulcers

• Location: Occur predominantly on the plantar (bottom) surface of the foot or over areas with bony deformities 1, 3
• Mechanism: Result from loss of protective sensation due to peripheral neuropathy, combined with repetitive mechanical stress and trauma 3
• Characteristics: Typically develop at high-pressure points where patients cannot feel pain or injury 1

Ischemic Ulcers

• Location: More commonly found on the tips of toes or the lateral (side) borders of the foot 1, 3
• Mechanism: Caused by peripheral arterial disease (PAD) leading to inadequate blood supply and tissue perfusion 3
• Prevalence: PAD is present in up to 50% of patients with diabetic foot ulcers 3

Neuro-ischemic Ulcers

• Mechanism: Combination of both neuropathy and vascular insufficiency 3, 2
• Clinical significance: These ulcers carry higher risk for adverse outcomes including non-healing, infection, amputation, and death 4
• Trend: Recent data suggest ischemic and neuro-ischemic ulcers are increasing in prevalence 4

Additional Wound Types in Diabetic Patients

Beyond the three primary classifications, diabetic patients can develop several other wound types 5:

• Diabetic ulcers due to trauma (DUDT) 5
• Arterial wounds 5
• Venous wounds 5
• Mixed wounds (combination of arterial and venous pathology) 5
• Diabetic bullae (fluid-filled blisters) 5
• Furuncles and carbuncles (deep skin infections) 5
• Cellulitis (spreading skin infection) 5

Clinical Assessment Approach

Key Evaluation Steps

When assessing any diabetic foot ulcer, you must determine 1:

1. Type classification: Through history and clinical examination, classify as neuropathic, neuro-ischemic, or purely ischemic 1

2. Vascular assessment:

   • Palpate foot pulses in all patients 1
   • Measure ankle-brachial index (ABI) using Doppler; normal is 0.9-1.3 1
   • Check toe-brachial index (TBI); normal is ≥0.75 1
   • Note that ankle pressures can be falsely elevated due to arterial calcification in diabetes 1

3. Location and depth:

   • Neuropathic ulcers: plantar surface or over bony prominences 1
   • Ischemic/neuro-ischemic: toe tips or lateral foot borders 1
   • Debride callus and necrotic tissue to accurately assess depth (except in severely ischemic non-infected ulcers) 1

Important Clinical Pitfalls

• Do not rely solely on symptoms or signs to predict PAD: No specific clinical findings reliably predict ulcer healing 1
• Always examine footwear: Ill-fitting shoes and barefoot walking are the most frequent causes of ulceration, even in patients with purely ischemic ulcers 1
• Recognize the rising trend: The paradigm has shifted from neuropathy as the main cause to an increasing preponderance of ischemic and neuro-ischemic ulceration over the past two decades 4