What is the proper assessment and diagnosis for a non-healing wound?

Proper Assessment and Diagnosis of Non-Healing Wounds

Begin with ankle-brachial index (ABI) measurement as the initial diagnostic test to determine if vascular insufficiency is contributing to impaired wound healing, followed by wound-specific assessment including depth probing, infection evaluation, and perfusion studies when indicated. 1

Initial Vascular Assessment

Measure ABI immediately in all patients with non-healing wounds to identify peripheral arterial disease (PAD) and guide treatment decisions. 1, 2

ABI Interpretation and Next Steps

• ABI ≤0.90 confirms PAD diagnosis and requires vascular surgery referral for potential revascularization 1
• ABI 0.70-0.90 (mildly reduced) warrants additional perfusion studies (TBI, TcPO2, or SPP) to determine if factors other than PAD are contributing to impaired healing 1
• ABI >1.40 indicates noncompressible arteries (arterial calcification, common in diabetes); proceed immediately to toe-brachial index (TBI) measurement 1
• ABI 1.00-1.40 (normal) or 0.91-0.99 (borderline) in the setting of non-healing wounds requires TBI with waveforms, TcPO2, or SPP to diagnose critical limb ischemia 1

Critical Perfusion Thresholds

These values indicate critical ischemia requiring urgent vascular referral: 1, 2

• Toe pressure <30 mm Hg (decreases likelihood of wound healing)
• TBI ≤0.70 (diagnostic of PAD)
• TcPO2 <30 mm Hg (predicts poor ulcer healing)
• SPP <30-50 mm Hg (associated with decreased wound healing)
• Ankle pressure <50 mm Hg (critical ischemia)

Perform all perfusion measurements in a warm room to prevent arterial vasoconstriction that could falsely lower values. 1

Wound-Specific Physical Assessment

Probe to Bone Test

Use a sterile, blunt metal probe to assess wound depth, detect bone involvement (osteomyelitis), identify foreign bodies, and evaluate for communications with joint cavities or tendon sheaths. 1 Bone has a characteristic stony feel when touched with the probe and indicates possible osteomyelitis requiring imaging and infectious disease consultation 1.

Wound Measurement and Documentation

Measure and document the following parameters at initial assessment and weekly thereafter: 1, 3

• Length, width, and depth in centimeters
• Wound bed appearance: tissue type (granulation, slough, necrotic, eschar), color, and percentage of each tissue type 1, 3
• Exudate quantity and quality: amount (scant, moderate, copious), color, consistency, and odor 1, 3
• Undermining or tunneling: presence, location (clock position), and extent in centimeters 3
• Wound edges: attached vs. rolled, epithelialization, maceration 3
• Periwound skin: erythema extent, induration, warmth, edema 1

Infection Assessment

Diagnose infection clinically based on these secondary signs, as inflammation alone is unreliable: 1

• Purulent drainage (most specific sign) 1
• Wound dehiscence, bridging to other structures, or pocketing 1
• Increasing wound size despite treatment 1
• Temperature elevation at wound site 1
• New areas of breakdown 1
• Erythema extending beyond wound margins with edema 1
• Foul odor 1

Use the NERDS/STONES assessment tool for systematic infection evaluation: 1

• NERDS (superficial infection): Nonhealing, Exudate, Red friable tissue, Debris/discoloration, Smell
• STONES (deep infection): Size increasing, Temperature elevation, Os (probes to bone), New breakdown, Erythema/Edema, Exudate, Smell

Microbiological Assessment

Obtain wound cultures only when infection is clinically suspected, not routinely. 1

Collect tissue specimens via biopsy or curettage after debridement—these provide more accurate results than superficial swabs. 1 If tissue biopsy is not feasible, use semiquantitative swab cultures with the Levine technique (rotate swab over 1 cm² area with sufficient pressure to express fluid from wound tissue) 1.

Avoid superficial swab specimens as they yield more contaminants and colonizers than deep pathogens. 1

Imaging Studies

For Suspected Osteomyelitis or Deep Infection

Order plain radiographs as the initial imaging study for suspected bone involvement. 1 If radiographs are negative but clinical suspicion remains high, MRI is the most sensitive and specific test for detecting osteomyelitis, soft tissue abscesses, and sinus tracts. 1

Ultrasound or CT scanning can detect deep soft-tissue abscesses requiring drainage. 1

For Anatomic Vascular Assessment

When revascularization is being considered, obtain duplex ultrasound as the first-line imaging method to confirm PAD lesions and assess anatomic location and severity of stenosis. 1

For aorto-iliac or multisegmental/complex disease, CTA or MRA are recommended as adjuvant imaging techniques for revascularization planning. 1

Specialized Assessment for Specific Wound Types

Diabetic Foot Ulcers with Amputation Risk

In patients with diabetes and chronic lower-limb wounds, apply the WIfI (Wound, Ischemia, and foot Infection) classification system to estimate individual amputation risk. 1 This system integrates wound size, limb perfusion parameters, and extent of foot infection 1.

Measure toe pressure or TBI in all diabetic patients with wounds, even if resting ABI is normal, due to high prevalence of arterial calcification. 1

Pressure Injuries

For sacral or gluteal pressure injuries, assess for underlying osteomyelitis if the wound probes to bone or fails to heal despite appropriate treatment. 1 Consider MRI to evaluate pelvic bone involvement 1.

Implement immediate pressure offloading with specialized pressure-relieving mattresses and turning schedules every 2-3 hours. 4

Venous Leg Ulcers

Confirm adequate arterial perfusion (ABI >0.8) before initiating compression therapy to avoid tissue necrosis. 5, 2

Critical pitfall: Never apply compression if ABI <0.5 or ankle pressure <50 mm Hg, as this indicates critical arterial disease. 5

Systematic Evaluation of Contributing Factors

Assess and document these host factors that impair healing: 2

• Diabetes control: HbA1c level 2
• Nutritional status: albumin, prealbumin, protein intake 4
• Smoking status 2
• Medications: immunosuppressants, corticosteroids 2
• Functional status: ability to offload pressure, mobility 1

Diagnostic Algorithm Summary

1. Measure ABI in all patients 1, 2
2. If ABI >1.40 or patient has diabetes, measure TBI 1
3. If perfusion thresholds indicate critical ischemia, obtain urgent vascular surgery consultation 1, 2
4. Perform comprehensive wound assessment including probing to bone 1, 3
5. Assess for clinical signs of infection using NERDS/STONES criteria 1
6. Obtain tissue cultures only if infection is present 1
7. Order imaging (plain films, then MRI) if osteomyelitis suspected 1
8. Obtain vascular imaging (duplex ultrasound, CTA/MRA) if revascularization considered 1
9. Apply WIfI classification for diabetic foot ulcers 1
10. Reassess weekly to monitor healing progress 4