What is the order of evaluation and diagnosis for a diabetic heel wound?

Evaluation and Diagnosis of Diabetic Heel Wounds

Evaluate every diabetic heel wound systematically in three sequential steps: first assess the patient's overall status and vascular supply, then examine the wound characteristics and infection severity, and finally obtain imaging to detect deep tissue involvement including osteomyelitis. 1

Step 1: Vascular Assessment (Perform First)

Assess arterial supply immediately in every diabetic foot wound patient, as peripheral artery disease (PAD) is present in 20-40% of cases and critically impacts healing and mortality. 1

Initial Bedside Vascular Evaluation:

• Palpate dorsalis pedis and posterior tibial pulses - if both are palpable, arterial supply is generally adequate 1
• Measure ankle-brachial index (ABI) and obtain Doppler arterial waveforms in all patients with foot ulcers 1

Interpret Vascular Studies:

• ABI 0.9-1.3 with triphasic pedal waveforms largely excludes PAD 1
• ABI <0.5 or ankle pressure <50 mmHg indicates severe ischemia requiring urgent vascular imaging and revascularization 1
• Caution: ABI >1.1 suggests arterial calcification and may be falsely elevated - use toe pressures or TcPO2 instead 1

Advanced Perfusion Testing (When Indicated):

• Toe pressure ≥30 mmHg, TcPO2 ≥25 mmHg, or skin perfusion pressure ≥40 mmHg each increase healing probability by at least 25% 1
• Consider urgent revascularization if toe pressure <30 mmHg or TcPO2 <25 mmHg 1

Step 2: Wound and Infection Assessment

Neuropathy Evaluation:

• Test for loss of protective sensation using 10-g monofilament at 2 of 3 sites (plantar heel, metatarsal heads, toe tips) 1

Wound Debridement and Examination:

• Debride all hyperkeratosis (callus) and necrotic tissue before assessment - this is essential for accurate evaluation and culture collection 1
• Exception: Do not debride non-infected ulcers with severe ischemia 1
• After debridement, measure and document wound size, depth, and drainage characteristics 1

Probe-to-Bone Test:

• Use a sterile, blunt metal probe to assess depth and detect palpable bone - bone has a characteristic stony feel and indicates likely osteomyelitis 1
• Document presence of foreign bodies, abscess cavities, joint involvement, or tendon sheath communication 1

Infection Diagnosis:

• Diagnose infection by presence of ≥2 signs of inflammation (erythema, warmth, tenderness, pain, induration) or purulent secretions 1
• Classify severity as mild (superficial cellulitis), moderate (deeper/extensive), or severe (systemic sepsis signs) 1
• Note: Systemic signs (fever, leukocytosis) are absent in 50% of severe infections due to neuropathy 1

Culture Collection (If Infected):

• Obtain tissue specimens from debrided wound base via curettage or biopsy before antibiotics - tissue cultures are superior to swabs 1
• Avoid swabbing undebrided ulcers - this yields contaminants and misses deep flora 1
• Obtain blood cultures if severe infection or systemic illness present 1

Step 3: Imaging Studies

Plain Radiography (Obtain in All Cases):

• Order two-view plain radiographs of the foot to detect osteomyelitis, foreign bodies, gas in tissues, and Charcot deformity 1

Advanced Imaging (When Indicated):

• MRI is best for detecting osteomyelitis, deep abscesses, sinus tracts, and muscle involvement 1
• Consider CT or ultrasound for detecting soft-tissue abscesses 1
• Nuclear medicine scans (labeled leukocytes) are highly sensitive but less specific than MRI 1

Vascular Imaging (When Revascularization Needed):

• Use color Doppler ultrasound, CTA, MRA, or digital subtraction angiography to visualize entire lower extremity arterial circulation with detailed below-knee and pedal artery visualization 1

Critical Pitfalls to Avoid

• Never rely solely on ABI in diabetics - arterial calcification causes falsely elevated readings; always correlate with pulse exam and consider toe pressures 1
• Do not attribute poor healing to "diabetic microangiopathy" - this should not be considered a cause of non-healing ulcers 1
• Patients with PAD and infection are at particularly high risk for major amputation and require emergency treatment 1
• If wound does not improve within 6 weeks despite optimal management, consider vascular imaging and revascularization regardless of bedside test results 1