In suspected periprosthetic joint infection, which tests and steps form the core diagnostic approach?

• A. Elevated ESR/CRP; synovial fluid analysis with culture; imaging; treat with antibiotics and consider staged revision if infection confirmed
• B. Joint aspiration is contraindicated
• C. ESR/CRP are unhelpful
• D. Only imaging is necessary

Answer: (D)

Diagnosing suspected prosthetic joint infection relies on an integrated assessment rather than a single test. Imaging can reveal prosthesis loosening, fluid pockets, or bone loss, but it cannot independently confirm infection because many non-infectious processes can mimic these findings.

The key steps use objective markers and direct sampling. Start with inflammatory markers like ESR and CRP to screen for an inflammatory process. Next, obtain joint fluid through aspiration and perform synovial fluid analysis, including cell count with differential, Gram stain, and cultures. A high synovial leukocyte count with a neutrophil predominance, plus positive cultures, strongly supports infection. Cultures from synovial fluid and from periprosthetic tissues obtained during surgery are crucial for confirming the diagnosis and choosing appropriate antibiotics. If infection is confirmed, treatment decisions (such as staged revision) follow based on organism and patient factors. Imaging is valuable as an adjunct to assess the extent of involvement but cannot replace the combined laboratory and microbiological workup.