Managing the Infected Total Joint: A Treatment Algorithm

Visual Element: An interactive flow chart titled "The PJI Decision Tree". Users start at "Diagnosis Confirmed" and answer questions ("Symptoms < 4 weeks?", "Implant Loose?", "Host Compromised?") to arrive at the recommended procedure.

Diagnosing Periprosthetic Joint Infection (PJI) is only the first battle. The war is won in the operating theatre. The decision of how to treat PJI is one of the most complex in orthopaedics, balancing the desire to save the implant/function against the imperative to eradicate the biofilm.

This guide focuses on the surgical decision-making and technical execution of PJI management.

The Enemy: Biofilm

Understanding biofilm is crucial. Within minutes of bacterial adhesion to an implant, bacteria secrete a polysaccharide slime (glycocalyx). Within this matrix:

• Bacteria become sessile (dormant).
• Antibiotics cannot penetrate (requires 1000x MIC).
• The immune system is blocked.

Surgical Implication: You cannot "wash off" biofilm. You must physically remove the substrate it lives on (the implant) OR catch it before the biofilm matures (Acute PJI).

The 3 Treatment Pathways

1. DAIR (Debridement, Antibiotics, and Implant Retention)

The Goal: Save the prosthesis. The Golden Window:

• Early Post-op: < 4 weeks from index surgery.
• Acute Hematogenous: < 3 weeks of symptoms in a previously well-functioning joint.

Contraindications (Do NOT do DAIR if):

• Implant is loose.
• Sinus tract present.
• Organism is MRSA (high failure), Fungal, or Multi-drug resistant.
• Poor soft tissue envelope.

Surgical Technique:

1. Radical Synovectomy: Excision of all infected synovium.
2. Modular Exchange: You MUST remove the polyethylene liner and femoral head. This gives access to the posterior capsule and removes a colonized surface.
3. Chemical Adjuvants: Betadine soak, Hydrogen Peroxide, Chlorhexidine irrigation.
4. Antibiotics: 6 weeks IV + Oral.

2. One-Stage Exchange

The Goal: Eradicate infection and reconstruct in a single setting. Indications:

• Healthy host (McPherson A).
• Good soft tissues.
• Known, sensitive organism.
• Bone stock allows primary or simple revision implants.

Surgical Technique:

1. Explant: Remove all hardware and cement.
2. Debride: Radical bone and soft tissue clearance.
3. Resterilize: Reprep and redrape. New instruments. New gowns. Change suction/cautery.
4. Implant: Fixation with antibiotic-loaded cement (high dose).

3. Two-Stage Exchange (The Gold Standard)

The Goal: The safest, most reliable eradication method. Indications:

• Resistant organisms (MRSA, VRE, Fungi).
• Unknown organism (Culture negative).
• Soft tissue compromise (requiring flap).
• Systemic sepsis.

Stage 1 (Resection):

• Remove implants.
• Insert Antibiotic Spacer.
  • Static Spacer: Block of cement. Poor function, scarring.
  • Articulating Spacer: Molding cement onto a K-wire or using pre-made molds. Maintains soft tissue tension and motion. Use high-dose Vancomycin + Tobramycin in the cement (up to 4g per bag).
• Interval: 6-12 weeks of antibiotics. "Antibiotic Holiday" (2 weeks off) prior to re-aspiration to confirm clearance.

Stage 2 (Reimplantation):

• Only proceed if CRP trending down and aspiration is negative.
• Reconstruct with revision implants.

Technical Pearls for Spacers

High-Dose Antibiotic Cement:

• For fixation: < 2g powder per 40g cement (to preserve mechanical strength).
• For Spacers: Up to 4-8g powder per 40g cement. Mechanical strength doesn't matter. Elution matters.
• Mix: Vancomycin (Gram +) and Tobramycin/Gentamicin (Gram -). The combination increases elution of both (synergy).

The "Hand-Made" Spacer:

• Knee: Use a silicone mold if available. If not, shape the femur and tibia components by hand when doughy. Keep the joint distracted to preserve collateral ligaments.
• Hip: Use a rush rod or pinning of a massive cement bolus. Warning: Dislocation is common.

Outcomes

• DAIR: 60-80% success (lower for Staph).
• One-Stage: 85-90% success in selected patients.
• Two-Stage: 90-95% success (The benchmark).

Conclusion

The choice of procedure depends on the timing, the bug, and the host.

• Early + Healthy + Sensitive -> DAIR.
• Late + Healthy + Sensitive -> One-Stage.
• Late + Sick + Resistant -> Two-Stage.

Antibiotic Spacer Recipe

Download our guide on mixing high-dose antibiotic cement spacers.