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Periprosthetic joint infection (PJI)
Periprosthetic infection is a biofilm infection on the implant; diagnosis rests on joint aspiration and inflammatory markers before any antibiotic, and treatment depends on duration and implant stability: debridement with implant retention, or one-stage or two-stage exchange.
Why it matters in the exam
The typical stem describes a hip or knee replacement that has hurt for months after surgery with a mildly raised CRP, or a red swollen joint with fever. Telling apart early infection (in the first weeks after surgery), delayed low-grade infection (months to two years, usually less virulent organisms such as coagulase-negative staphylococci) and late haematogenous infection (a blood-borne source years after surgery) decides treatment. Under the international consensus definition, two major criteria are each enough for diagnosis: a sinus tract communicating with the prosthesis, or two positive cultures of the same organism. Minor criteria include serum CRP, sedimentation rate and D-dimer, synovial white cell count and neutrophil percentage, leukocyte esterase, alpha-defensin, histology and pus at surgery. The most important principle: do not give blind antibiotics before aspiration and cultures, and where possible stop antibiotics about two weeks before aspiration. In the shoulder, Cutibacterium acnes causes low-grade infection and needs prolonged culture incubation. Acute infection with a stable implant is treated with debridement, antibiotics and implant retention (DAIR) with exchange of the modular parts; chronic infection needs exchange, in one stage or in two stages with an antibiotic spacer. Rifampicin is usually added for staphylococcal infection around an implant because of its activity against biofilm. Prevention includes treating active infections before surgery, prophylactic antibiotics before the incision and strict sterility in theatre.
Key points
- A biofilm infection on the implant.
- Joint aspiration and cultures before any antibiotic.
- Major criterion: a sinus tract or two positive cultures of the same organism.
- Acute infection with a stable implant — DAIR; chronic — exchange.
- Rifampicin against biofilm in staphylococcal infection.
Summary table
| Type of infection | Time from surgery or symptoms | Usual treatment |
|---|---|---|
| Early postoperative | First weeks after surgery | Debridement, antibiotics and implant retention (DAIR) with exchange of modular parts |
| Acute haematogenous | Symptoms for less than 3 weeks with a stable implant | DAIR if the implant is stable and tissues are good |
| Chronic or low-grade | Months to two years, persistent pain | One-stage or two-stage exchange |
| Loose implant or sinus tract | Any time | Exchange; DAIR is not suitable |
| Patient unfit for surgery | Any time | Long-term suppressive antibiotics |
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Sources
- International Consensus Meeting on Musculoskeletal Infection (ICM), 2018 — Definition of Periprosthetic Joint Infection
- IDSA Clinical Practice Guideline, 2013 — Diagnosis and Management of Prosthetic Joint Infection
- AAOS Clinical Practice Guideline, 2019 — Diagnosis and Prevention of Periprosthetic Joint Infections
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.