Periprosthetic Joint Infection (PJI)

Periprosthetic Joint Infection (PJI)

Pathophysiology & Risk Factors

• Biofilm formation protects bacteria from antibiotics and immune response.

• Common organisms: Staphylococcus aureus, S. epidermidis, and Gram-negatives.

• Risk factors: prior surgery, obesity, diabetes, immunosuppression, long operative time, wound complications.
  💡 Host factors often outweigh surgical technique in determining infection risk.

Diagnosis

1.Clinical

• Persistent pain, drainage, erythema, or early implant loosening.

• Chronic PJI may lack systemic signs (fever often absent).

2. Laboratory

• ESR >30 mm/h, CRP >10 mg/L → highly suggestive.

• Normal ESR + CRP → infection unlikely.

3. Synovial Fluid

• Aspiration before antibiotics.

• Evaluate WBC count, %PMN, culture, and novel biomarkers (α-defensin, leukocyte esterase, synovial CRP).

• ≥2 positive cultures → diagnostic.

4. Imaging

• X-ray: loosening or osteolysis (nonspecific).

• MRI (metal-artifact reduction) → soft-tissue assessment.

• PET-CT / Indium-labeled WBC scan for uncertain cases.

5. Intra-operative

• ≥5 tissue samples; >5 PMNs/HPF = infection.

• Ultrasonication of explanted implants enhances microbial yield.

Treatment Strategies

1. Antibiotic Suppression

Reserved for unfit patients or non-surgical candidates.
Combination therapy (e.g., rifampicin + fluoroquinolone) may control low-grade infection.

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

• Indication: acute infection (<3 weeks), stable implant, sensitive organism.

• Success: 30–70%.
  💡 Early (<48 h) intervention improves eradication.

3. Resection Arthroplasty

• Salvage in non-ambulatory or medically fragile patients.

• High infection-control rate but poor function.

4. Single-Stage Exchange

• Removal and reimplantation in one operation.

• Indicated for known organism, healthy host, good bone stock.

• Control rate: 80–90%.

5. Two-Stage Exchange (Gold Standard)

• Step 1: remove all components, debridement, antibiotic spacer + 6 weeks IV therapy.

• Step 2: reimplant after infection markers normalize.

• Success: >90–95%.
  💡 Most reliable approach for chronic PJI.

Antibiotic-Loaded Cement & Spacers

• Deliver high local antibiotic concentration.

• Articulating spacers (e.g., PROSTALAC) maintain limb length and mobility while treating infection.

Recurrent or Resistant Infections

• Options: repeat two-stage revision, chronic suppressive therapy, or salvage resection.

• MRSA/VRE infections → rifampicin-based protocols remain effective.

Outcomes & Prognosis

• Infection eradication: >90% achievable with early multidisciplinary care.

• Function depends on timing, host status, and bone/soft-tissue preservation.

Key Pearls

• Always rule out infection before any revision.

• Combine serologic + synovial + intra-operative data for accurate diagnosis.

• Early, coordinated management (orthopaedics + ID + microbiology) is vital.

• Prevention: meticulous wound care, peri-op glucose control, skin optimization.

References 

1. Parvizi J, et al. Clin Orthop Relat Res. 2021; 479: 985-99.

2. Tande AJ, Patel R. N Engl J Med. 2014; 370: 2451-62.

3. Zimmerli W, et al. Lancet. 2004; 364: 1539-54.

4. Osmon DR, et al. Infect Dis Clin North Am. 2020; 34: 57-75.