Acute Hematogenous Periprosthetic Knee Infection: DAIR or Resection?

Debridement, antibiotics, and implant retention (DAIR) with exchange of modular components.

Favorable features, each of which is independently required for DAIR to have a reasonable chance:

• Acute symptom duration of 12 days (<3 weeks is the usual cut-off) - this is a hematogenous infection in a chronically well-functioning implant, not an early postoperative one with an immature biofilm.
• Well-fixed implant on radiographs with no osteolysis or loosening; implant retention is only defensible if the components are solidly ingrown.
• No sinus tract, no abscess with soft-tissue compromise, no sepsis.
• Mono-microbial gram-positive cocci are likely a susceptible staphylococcus or streptococcus, which responds to biofilm-active therapy.

Technique matters: thorough synovectomy and open debridement, exchange of the polyethylene insert (and any modular parts), copious lavage, and 5–6 tissue cultures. Hold antibiotics until cultures are taken unless he becomes septic. The patient's CKD mandates renal dosing and rifampin interacts with many drugs - this is an infectious-disease co-managed case. Quinolone-rifampin combinations for susceptible staphylococci have the best DAIR data, given for weeks after intravenous therapy.

Pivots to resection (or to a two-stage exchange):

• Symptom duration beyond 3–4 weeks; a sinus tract; chronic radiographic loosening or osteolysis.
• Resistant organisms: MRSA, vancomycin-resistant enterococcus, fungi, or multi-drug-resistant gram-negatives - DAIR failure rates climb steeply.
• Positive blood cultures with sepsis or endocarditis, an immunocompromised host, or extensive soft-tissue compromise.
• Inability to take biofilm-active oral antibiotics, or a patient who cannot tolerate a second operation if DAIR fails.

Counseling: even in ideal candidates, DAIR fails in roughly one in five to one in three, and failure often declares itself months later, not weeks. If DAIR fails, he faces a two-stage exchange anyway, with worse bone stock and greater soft-tissue compromise, so this is not a "free first try." Chronic oral suppression is an option only if resection is not feasible and the organism is susceptible - it controls, but does not cure, and carries toxicity and resistance risk. He should understand the plan is conditional on intraoperative findings and final cultures, and that keeping the knee is a probability, not a promise.

Convert to a resection arthroplasty and staged reimplantation.

• A loose component with intramedullary purulence means the biofilm involves the fixation interface and canal - DAIR cannot sterilize this. Remove all components and all cement, debride necrotic bone and soft tissue, and take multiple cultures, sending tissue rather than swabs.
• Insert an antibiotic-loaded cement spacer. An articulating spacer maintains soft-tissue tension and function, which eases reimplantation, but a static spacer is preferred when there is massive bone loss, ligamentous destruction, poor soft-tissue coverage, or an unreliable patient. Choose antibiotics with the infectious-disease team and confirm they are heat-stable and release adequately.
• Six weeks of organism-specific intravenous therapy, with a two-week antibiotic-free interval before reimplantation cultures.
• Reimplant when the wound is dry, CRP and ESR have normalized, synovial fluid at reaspiration is acellular, and cultures are negative. Depending on host and soft tissue, the reconstruction may need a more constrained or hinged implant, and he must be warned that the chance of a functioning, infection-free knee is now lower than with an uncomplicated primary, and that arthrodesis or amputation remain fall-backs.