What is the treatment for wound undermining caused by infection?

Treatment of Wound Undermining Caused by Infection

Infected wounds with undermining require aggressive surgical debridement combined with systemic antibiotic therapy targeting the causative organisms, followed by proper wound dressing and off-loading. 1

Recognition of Infection in Undermined Wounds

Undermining of wound edges is recognized as a secondary sign of infection, particularly in patients who may not manifest classic inflammatory signs due to neuropathy or ischemia. 1 The presence of undermining alongside other findings such as:

• Nonpurulent secretions 1
• Friable or discolored granulation tissue 1
• Foul odor 1
• At least 2 classic inflammatory signs (erythema, warmth, tenderness, pain, induration) or purulent secretions 1

These findings establish the diagnosis of wound infection and mandate treatment. 1

Surgical Management: The Primary Intervention

Most infected wounds require surgical intervention ranging from minor debridement to major resection. 1 This is the cornerstone of treatment because:

• Infection disrupts the bacteria-host equilibrium and inhibits all wound healing processes 2
• Bacterial proliferation in undermined spaces creates protected environments that antibiotics alone cannot adequately penetrate 2
• Debridement removes necrotic tissue and reduces bacterial load, re-establishing conditions favorable for healing 1, 3

For undermined wounds specifically, surgical debridement must address the undermined pockets to eliminate dead space where bacteria proliferate. 1

Antibiotic Therapy

Systemic antibiotics are mandatory for infected wounds with undermining. 1 The approach should be:

Empiric therapy: Target gram-positive cocci (especially staphylococci) as they are the most common pathogens in diabetic foot infections and skin/soft tissue infections. 1

Definitive therapy: Base treatment on cultures of infected tissue (not swabs). 1 For diabetic foot infections with undermining, piperacillin-tazobactam 3.375 grams IV every 6 hours for 7-10 days is appropriate for polymicrobial infections. 4

MRSA coverage: Add empiric MRSA coverage for patients with risk factors including long-stay care facilities, recent hospitalization, or previous antibiotic exposure. 1

A critical pitfall: superficial incisional infections that have been opened and drained can often be managed without antibiotics, but infected wounds with undermining require systemic therapy due to the depth and complexity of infection. 1

Wound Management After Debridement

Following surgical debridement and initiation of antibiotics:

• Proper wound dressing: Apply antimicrobial dressings to reduce wound colonization 5, 6
• Off-loading: Essential for pressure-related undermined wounds to prevent continued tissue damage 1
• Moisture control and infection management: Follow the T.I.M.E. framework (Tissue debridement, Infection control, Moisture balance, Edge preparation) 7, 3
• Regular monitoring: Frequent assessment for recurrent infection and measurement of wound dimensions 7

Assessment for Underlying Complications

Evaluate for osteomyelitis in diabetic foot infections with undermining, as bone infection occurs frequently and requires prolonged antibiotic therapy (often 4-6 weeks) or surgical resection. 1 MRI is the most sensitive and specific imaging modality for this diagnosis. 1

Assess for arterial ischemia in the affected limb, as ischemic wounds may require revascularization before healing can occur. 1

Advanced Therapies

For undermined wounds that fail standard treatment after infection control:

• Injectable dermal matrix fillers may eliminate dead space in undermined areas 8
• Negative pressure wound therapy can facilitate drainage and granulation tissue formation 3
• These should only be applied after infection is controlled and healthy granulation tissue is present 7, 3

Key Pitfalls to Avoid

• Never apply advanced wound products to actively infected wounds - this will result in treatment failure and abscess formation 7, 3
• Do not rely on antibiotics alone - surgical debridement is essential for infected undermined wounds 1
• Avoid inadequate debridement - all undermined pockets must be addressed to eliminate bacterial reservoirs 1
• Do not use wound swabs for culture - obtain tissue biopsies for accurate microbiological diagnosis 1