Periprosthetic Joint Infection (PJI): Causes, Symptoms, Diagnosis, Treatment, and Prevention

What is the Medical Term PJI?

PJI stands for Periprosthetic Joint Infection, a severe complication following joint replacement surgery where bacteria infect the tissues around the implanted prosthetic joint. It is a challenging and often devastating condition that significantly impacts patient outcomes and healthcare systems.

Understanding Periprosthetic Joint Infection (PJI)

Periprosthetic Joint Infection (PJI) refers to an infection that occurs in the tissue surrounding an artificial joint implant, such as a total knee replacement (TKR) or total hip replacement (THR). While joint replacement surgeries are highly successful in restoring function and relieving pain for millions, PJI represents one of the most serious complications, potentially leading to chronic pain, loss of joint function, the need for further complex surgeries, and in severe cases, even amputation or death. The infection can manifest acutely, shortly after surgery, or chronically, months to years later, making diagnosis and treatment particularly complex.

Causes and Risk Factors

PJI typically occurs when bacteria, and less commonly fungi, colonize the surface of the prosthetic implant and surrounding tissues. The implant material itself provides a surface where bacteria can form a protective biofilm, making them highly resistant to antibiotics and the body's immune response.

Common Pathways of Infection:

• Intraoperative Contamination: Bacteria entering the surgical site during the operation (e.g., from the patient's skin, surgical team, or environment). This is the most common cause.
• Hematogenous Spread: Bacteria traveling through the bloodstream from a distant site of infection (e.g., urinary tract infection, dental abscess, skin infection) and seeding the joint implant.
• Direct Inoculation: Bacteria entering through a breakdown in the skin overlying the joint, such as an open wound or fistula.

Risk Factors for PJI:

• Patient-Related Factors:
  • Immunocompromised states: Diabetes mellitus, rheumatoid arthritis, HIV/AIDS, patients on immunosuppressive medications.
  • Obesity: Increased surgical complexity and impaired wound healing.
  • Malnutrition: Compromised immune function.
  • Smoking: Impaired blood flow and wound healing.
  • Previous infections: History of septic arthritis in the joint.
  • Comorbidities: Renal failure, liver disease, peripheral vascular disease.
• Procedure-Related Factors:
  • Prolonged surgical time: Increased exposure to contaminants.
  • Complex or revision surgeries: Often involve more tissue damage and longer exposure.
  • Poor surgical technique: Inadequate sterile field maintenance.
  • Hematoma formation: Blood clots provide a culture medium for bacteria.
• Microorganism Factors:
  • Virulence of bacteria: Certain bacteria, like Staphylococcus aureus or coagulase-negative Staphylococci, are more commonly implicated due to their ability to form biofilms.

Signs and Symptoms

The presentation of PJI can vary significantly depending on the timing of onset and the specific microorganism involved.

Acute PJI (Onset within weeks to a few months post-surgery):

• Sudden onset of severe joint pain: Often out of proportion to typical post-operative pain.
• Swelling and warmth: Around the joint.
• Redness: Over the surgical incision site.
• Pus drainage: From the wound.
• Systemic symptoms: Fever, chills, fatigue, malaise.
• Limited range of motion: Due to pain and swelling.

Chronic PJI (Onset months to years post-surgery):

• Persistent or worsening joint pain: Often less acute than in early infections, but debilitating.
• Loosening of the prosthesis: Leading to instability and pain, often mimicking aseptic loosening.
• Swelling: May be subtle or intermittent.
• Fatigue and malaise: General feeling of unwellness.
• Fistula formation: A tract from the joint to the skin, with persistent drainage, is a definitive sign of infection.
• Subtle signs of inflammation: Such as mild warmth or tenderness.

Diagnosis of PJI

Diagnosing PJI can be challenging due to its varied presentation and the need to differentiate it from aseptic loosening or other complications. A comprehensive approach involving clinical assessment, laboratory tests, and imaging is typically required.

Key Diagnostic Tools:

• Clinical Examination: Assessment of pain, swelling, warmth, redness, wound status, and range of motion.
• Blood Tests:
  • Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP): Elevated levels are indicative of inflammation, though not specific to infection. Trends in these markers are often more useful than single values.
  • White Blood Cell Count (WBC): May be elevated, but not consistently.
  • D-dimer: Increasingly used as a screening tool, with low levels potentially ruling out PJI.
• Joint Aspiration (Arthrocentesis): Considered the gold standard.
  • Synovial Fluid Analysis: Includes cell count (high leukocyte count and neutrophil percentage are highly suggestive of PJI), glucose levels (low), and protein levels (high).
  • Microbiological Culture: Critical for identifying the causative organism and guiding antibiotic therapy. Extended incubation times are often necessary.
• Imaging Studies:
  • X-rays: May show periosteal reaction, osteolysis, or loosening of the prosthesis, but are often non-specific.
  • Magnetic Resonance Imaging (MRI) and Computed Tomography (CT): Can provide more detail on soft tissue involvement and bone changes.
  • Nuclear Medicine Scans (e.g., Technetium-99m bone scan, Gallium scan, Indium-111 labeled leukocyte scan): Can help differentiate infection from aseptic loosening but have limitations.
• Histological Examination: Analysis of periprosthetic tissue biopsies for inflammatory cells.
• Molecular Diagnostics: PCR-based methods for rapid pathogen identification.

Treatment Strategies

Treatment for PJI is complex and typically involves a multidisciplinary team including orthopedic surgeons, infectious disease specialists, and rehabilitation therapists. The primary goals are to eradicate the infection, preserve or restore joint function, and alleviate pain.

Treatment Options:

• Surgical Intervention: The cornerstone of PJI management.
  • Debridement, Antibiotics, and Implant Retention (DAIR): Suitable for acute infections, stable implants, and sensitive organisms. Involves surgical washout and removal of infected tissue while retaining the implant.
  • One-Stage Exchange Arthroplasty: The infected implant is removed, the joint is thoroughly debrided, and a new implant is inserted in the same surgery. Best for certain organisms and well-defined cases.
  • Two-Stage Exchange Arthroplasty: The most common and often most successful approach. The infected implant is removed, and an antibiotic-impregnated spacer is placed. After a period of intravenous antibiotics (typically 6-12 weeks) and resolution of infection markers, a second surgery is performed to implant a new prosthesis.
  • Resection Arthroplasty (Girdlestone procedure for hip): Removal of the implant without replacement, leading to a flail joint but clearing the infection. Used for severe, recalcitrant infections.
  • Arthrodesis: Fusion of the joint, eliminating motion but eradicating infection.
  • Amputation: A last resort for uncontrolled, life-threatening infections.
• Antibiotic Therapy: Essential to eradicate the bacteria.
  • Systemic Antibiotics: Administered intravenously, often for an extended period (weeks to months), followed by oral antibiotics. Selection is based on culture results and antibiotic sensitivity.
  • Local Antibiotics: Often incorporated into bone cement or spacers during surgery to deliver high concentrations directly to the infected site.

Prevention of PJI

Prevention is paramount due to the significant challenges of treating PJI. A multi-faceted approach involving pre-operative, intra-operative, and post-operative strategies is employed.

Key Preventive Measures:

• Pre-operative Optimization:
  • Patient Education: Informing patients about risks and post-operative care.
  • Control of Comorbidities: Optimizing blood sugar in diabetics, managing nutritional status, cessation of smoking.
  • Eradication of Remote Infections: Treating dental issues, skin infections, or urinary tract infections before surgery.
  • Pre-operative Skin Preparation: Using antiseptic washes.
• Intra-operative Measures:
  • Strict Aseptic Technique: Meticulous sterile practices by the surgical team.
  • Operating Room Environment: Use of laminar flow ventilation, reduced traffic.
  • Antibiotic Prophylaxis: Administration of intravenous antibiotics shortly before incision.
  • Minimal Tissue Trauma: Careful surgical technique to preserve tissue viability.
  • Antibiotic-Impregnated Bone Cement: For certain joint replacements.
• Post-operative Measures:
  • Appropriate Wound Care: Keeping the incision clean and dry.
  • Prompt Recognition and Treatment of Superficial Infections: To prevent progression to deep PJI.
  • Avoidance of Elective Procedures: Patients with joint replacements should take antibiotic prophylaxis for procedures that could cause bacteremia (e.g., dental work, colonoscopy), though this remains a debated topic for routine dental care.

Prognosis and Long-Term Outlook

The prognosis for PJI depends on several factors, including the patient's overall health, the virulence of the infecting organism, the duration of the infection, and the effectiveness of treatment. While treatment can be successful, PJI often leads to:

• Multiple Surgeries: Patients often undergo several operations.
• Prolonged Hospital Stays: Due to complex surgical procedures and extended intravenous antibiotic courses.
• Functional Limitations: Even after successful treatment, some degree of joint stiffness, pain, or reduced range of motion may persist.
• Increased Healthcare Costs: PJI imposes a significant economic burden.
• Impact on Quality of Life: Chronic pain, disability, and the emotional toll of repeated treatments can significantly affect a patient's well-being.

Early diagnosis and aggressive, appropriate treatment are critical to improving outcomes for individuals suffering from Periprosthetic Joint Infection.