Is a patient with an exposed tendon, 2.5 cm deep tunneling, and a 3 cm wide cavity after total knee revision, on dapsone (Daps), linezolid (Zero), and rifampin, a candidate for wound vac therapy?

Wound VAC Candidacy in Post-Revision Total Knee Arthroplasty with Exposed Tendon

This patient is a candidate for wound VAC therapy, but only after confirming adequate infection control and ensuring no active purulence is present in the wound. The exposed tendon with deep tunneling and cavity formation represents a complex wound that can benefit from negative pressure wound therapy as a bridge to definitive closure, provided specific conditions are met.

Critical Prerequisites Before VAC Application

Active purulence is an absolute contraindication to VAC therapy. 1 The wound must be thoroughly debrided and free of gross purulent drainage before applying negative pressure. 1 Given this patient is already on triple antibiotic therapy (dapsone, linezolid, rifampin) under infectious disease management, the infection is being addressed systemically, but local wound assessment is paramount.

Mandatory Pre-VAC Steps:

• Perform aggressive surgical debridement to remove all necrotic tissue and purulent material before VAC application 1
• Obtain intraoperative cultures from deep tissue and bone to guide ongoing antibiotic therapy 1
• Confirm absence of active purulence at the wound bed—VAC should not be applied if purulent drainage persists 1
• Assess for osteomyelitis through probe-to-bone testing and imaging (MRI is gold standard) 2, as the exposed tendon and deep cavity raise concern for underlying bone infection

Evidence Supporting VAC Use in This Clinical Scenario

VAC therapy has demonstrated efficacy specifically for orthopedic infections with exposed structures. 3 Multiple studies support its use in post-arthroplasty infections with wound complications, showing successful infection eradication while preserving implants when appropriate. 3

Specific Benefits for This Patient:

• Manages exposed tendons effectively: VAC therapy has proven successful in diabetic foot wounds and orthopedic cases with exposed tendon, fascia, and bone 4, 5
• Promotes granulation over exposed structures: Studies show >90% coverage of exposed structures achieved with VAC therapy 5
• Reduces bacterial load: All patients in key studies cleared bacterial infection by end of VAC therapy 6, 4
• Manages deep cavities and tunneling: The controlled negative pressure eliminates dead space and promotes wound contraction 7, 6

Treatment Algorithm

Phase 1: Wound Preparation (Days 1-3)

• Surgical debridement of all necrotic tissue and removal of purulent material 1
• Obtain deep tissue and bone cultures 1
• Continue systemic antibiotics (current triple therapy is appropriate for complex prosthetic joint infection) 1
• Assess wound bed—proceed to VAC only if no active purulence remains 1

Phase 2: VAC Application (Average 14-23 days)

• Apply controlled negative pressure (typically -125 mmHg) uniformly across wound surface 6, 4
• Change dressings every 4-5 days 6
• Monitor for granulation tissue formation and wound size reduction 4, 5
• Continue systemic antibiotics throughout VAC therapy 1, 3

Phase 3: Definitive Closure

• If adequate granulation achieved: Proceed to split-thickness skin graft (most common approach, used in 89% of cases) 4, 5
• If persistent exposed structures: Consider muscle flap coverage after VAC preparation 1
• If infection persists: VAC serves as bridge to further surgical intervention 1, 3

Critical Caveats and Pitfalls

The multidrug-resistant nature of prosthetic joint infections requires special consideration. 1 If cultures reveal MRSA, Pseudomonas, or multidrug-resistant organisms, graft preservation becomes more challenging and may require more aggressive surgical management beyond VAC therapy alone. 1

Do not use VAC as monotherapy for active infection. 1 The IWGDF guidelines specifically note that while VAC is used for infected wounds in other contexts, there is insufficient evidence supporting its use as primary treatment for infected diabetic foot wounds, and one study showed non-significantly higher infection rates with VAC. 1 This patient requires continued aggressive antibiotic therapy and infectious disease follow-up.

Quantitative bacterial cultures should guide decision-making. 1 Some authorities suggest graft preservation should not be attempted until colony counts are <10^5 colony-forming units per gram of tissue. 1

Monitor for VAC-related complications: While generally safe, ensure proper application technique and monitor for pain, bleeding, or signs of worsening infection during therapy. 6, 3, 5

Duration and Cost Considerations

Expected VAC therapy duration is 14-23 days based on published series. 6, 4, 5 This represents a cost-effective approach compared to prolonged hospitalization with conventional dressings, particularly in preparing the wound bed for definitive closure. 4, 5