Periprosthetic Joint Infection (PJI)
Periprosthetic joint infection (infection of an artificial hip or knee joint) is the most feared complication of joint replacement surgery. PJI causes profound pain, implant failure, and significant morbidity, and its treatment is far more complex and demanding than the original joint replacement. Accurate, timely diagnosis and selection of the appropriate treatment strategy, from antibiotics and irrigation to full implant exchange, are critical to achieving the best possible outcome. At Maryland Orthopedic Specialists, our Adult Reconstruction team follows evidence-based diagnostic and treatment protocols drawn from leading international consensus guidelines to manage both acute and chronic periprosthetic joint infections.
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What is periprosthetic joint infection (pji)?
A periprosthetic joint infection occurs when bacteria or other microorganisms colonize the surface of a joint replacement implant. Biofilm formation (a protective matrix the organisms construct on the implant) makes these infections notoriously resistant to antibiotics alone and immune system clearance.
A periprosthetic joint infection occurs when bacteria or other microorganisms colonize the surface of a joint replacement implant. Biofilm formation (a protective matrix the organisms construct on the implant) makes these infections notoriously resistant to antibiotics alone and immune system clearance. The most common organisms are coagulase-negative Staphylococcus (including S. epidermidis) and Staphylococcus aureus, accounting for approximately 50–60% of cases. Gram-negative organisms and polymicrobial infections are less common but more challenging.
PJI is classified by timing and mechanism:
- Acute post-operative (Type I): Within the first 3–4 weeks after surgery; often from direct contamination at the time of surgery.
- Acute hematogenous (Type II): Sudden seeding of an otherwise well-functioning implant from a distant bacteremic source (dental procedure, urinary tract infection, skin infection); can occur years after implantation.
- Chronic / Late (Type III): Presents > 3–4 weeks post-operatively with gradual, indolent infection; often low-virulence organisms forming an established biofilm.
The overall incidence of PJI after primary total knee replacement is approximately 1–2% and 1% after primary total hip replacement.
Symptoms — do you recognize these?
- Acute PJI: Fever, erythema (redness), warmth, and swelling around the joint; increasing pain; wound drainage; or dehiscence (wound opening)
- Chronic PJI: Persistent or worsening pain after a pain-free interval; the patient may describe the joint never feeling right since surgery; stiffness; subtle swelling
- Hematogenous PJI: Sudden onset of severe pain and swelling in a previously well-functioning joint, sometimes following a dental or other invasive procedure
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How we diagnose it
The International Consensus Meeting (ICM) and the Musculoskeletal Infection Society (MSIS) have established validated diagnostic criteria. Workup includes:
Serum (blood) markers:
- Erythrocyte sedimentation rate (ESR): Elevated in PJI; non-specific but sensitive.
- C-reactive protein (CRP): The most useful single serum marker; elevated in >90% of confirmed PJI cases.
- D-dimer: Emerging as an adjunctive marker with high sensitivity.
- Interleukin-6 (IL-6): Highly sensitive but less widely available.
Joint aspiration (synovial fluid analysis):
- Synovial white blood cell (WBC) count: Elevated cell counts (> 3,000 cells/μL for TKA, > 3,000 cells/μL for THA at chronic timepoints; higher thresholds used acutely) are highly suggestive of PJI.
- Polymorphonuclear (PMN) differential: > 80% PMNs strongly correlated with infection.
- Alpha-defensin: A synovial fluid biomarker with high sensitivity and specificity for PJI; available as laboratory assay or lateral flow test.
- Leukocyte esterase strip: Rapid, inexpensive point-of-care test.
- Culture: Identifies the organism and guides antibiotic selection. Requires 14-day hold for fastidious organisms.
Imaging:
- Plain X-rays may show loosening, periosteal reaction, or implant failure but cannot confirm infection.
- Nuclear medicine studies (technetium bone scan, labeled leukocyte scan) have adjunctive utility in equivocal cases.
Intra-operative criteria:
- Histological analysis of peri-implant tissue (> 5 PMNs per high-power field)
- Positive cultures from multiple intraoperative specimens
The ICM-defined PJI diagnosis requires meeting specific thresholds across these criteria; no single test is diagnostic.
Treatment options
Treatment of PJI depends on the timing and chronicity of infection, organism characteristics, implant fixation, and the patient's overall medical condition.
DAIR (Debridement, Antibiotics, and Implant Retention)
DAIR is appropriate for acute PJI (both early post-operative and acute hematogenous) when symptoms have been present for fewer than 3 to 4 weeks (before mature biofilm forms), the implant is well-fixed, the infecting organism is known and susceptible, and soft tissues are adequate. The procedure involves surgical debridement of all infected and necrotic tissue, exchange of all modular components (polyethylene tibial insert, femoral head), thorough joint irrigation, and a course of pathogen-directed IV followed by oral antibiotics, typically 6 to 12 weeks, sometimes followed by prolonged suppression. Success rates for well-selected acute PJI cases are 70 to 80%.
Suppressive Antibiotics
Chronic oral antibiotic suppression (indefinite low-dose antibiotics to control rather than eradicate infection) is reserved for patients who cannot tolerate revision surgery due to medical comorbidities, or as an adjunct after failed two-stage exchange. This is not a curative approach.
Revision Hip Arthroplasty
Surgical revision of a failed hip replacement, addressing worn components, loosening, instability, or periprosthetic infection. Requires specialized revision implant systems and reconstruction techniques beyond primary replacement.
Click for more Surgical ProcedureRevision Total Knee Replacement
Complex re-operation to address worn, loose, unstable, or infected knee replacement components. Requires modular augments, intramedullary stems, and increased constraint levels matched to the degree of bone and ligament deficiency.
Click for moreRecovery & rehabilitation
Recovery from PJI treatment is more prolonged than primary joint replacement:
- After DAIR: Several weeks of IV antibiotics followed by oral antibiotics; gradual return to weight-bearing as wounds and tissues recover.
- After Stage 1 (spacer): Protected weight-bearing with antibiotic spacer in place; significant functional limitation; ~3 months before Stage 2.
- After Stage 2 (reimplantation): Recovery mirrors primary joint replacement but is often slower due to prior scarring, muscle atrophy, and bone changes; 6–12 months to maximum function.
Risk factors for PJI include obesity, diabetes, immunosuppression, prior knee or hip surgery, malnutrition, and smoking. Optimization of these factors before primary surgery is the most effective prevention strategy.
Frequently Asked Questions
Can PJI be prevented?
Is PJI always apparent immediately after surgery?
What if the infection can't be eradicated?
Do I need to tell my dentist I have a joint replacement?
How is periprosthetic joint infection treated, and will I need my implant removed?
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References
- Parvizi J, Gehrke T, Chen AF. Proceedings of the International Consensus on Periprosthetic Joint Infection. Bone Joint J. 2013;95-B(11):1450–1452. https://doi.org/10.1302/0301-620X.95B11.33135
- Zmistowski B, Karam JA, Durinka JB, Casper DS, Parvizi J. Periprosthetic joint infection increases the risk of one-year mortality. J Bone Joint Surg Am. 2013;95(24):2177–2184. https://doi.org/10.2106/JBJS.L.00789
- Osmon DR, Berbari EF, Berendt AR, et al. Diagnosis and management of prosthetic joint infection: clinical practice guidelines by the Infectious Diseases Society of America. Clin Infect Dis. 2013;56(1):e1–e25. https://doi.org/10.1093/cid/cis803
- Deirmengian C, Kardos K, Kilmartin P, Cameron A, Schiller K, Parvizi J. Diagnosing periprosthetic joint infection: has the era of the biomarker arrived? Clin Orthop Relat Res. 2014;472(11):3254–3262. https://doi.org/10.1007/s11999-014-3543-8
- Gehrke T, Alijanipour P, Parvizi J. The management of an infected total knee arthroplasty. Bone Joint J. 2015;97-B(10 Suppl A):20–29. https://doi.org/10.1302/0301-620X.97B10.36475
- American Academy of Orthopaedic Surgeons. Periprosthetic Joint Infection. OrthoInfo. https://orthoinfo.aaos.org/en/diseases--conditions/periprosthetic-joint-infection/