Structured Oral Examination: Infected TKA Case Questions
Key Takeaway
We review everything you need to understand about Structured Oral Examination: Infected TKA Case Questions. An **oralexamination question infected** total knee arthroplasty (TKA) presents with increasing pain, stiffness, and recurrent swelling. Diagnosing this involves a detailed history, clinical examination, and key investigations. Initial tests include routine blood work like CRP and ESR; IL-6 assays offer higher sensitivity. Further steps may involve radioisotope bone scans, alignment checks, and joint aspiration to confirm the infection.
A 72-year-old patient presents with a chronically painful, stiff total knee arthroplasty (TKA) 8 years post-index procedure. Plain radiographs demonstrate subtle lucency around the tibial component. You suspect a low-grade periprosthetic joint infection (PJI). You perform a partial resection of the lateral aspect of the synovial lining for histopathological analysis. Looking at this histology, how do you interpret these findings in the context of a suspected PJI?
Candidate: "I am looking for evidence of acute inflammation, specifically polymorphonuclear leukocytes. According to the MSIS criteria, if I see more than 5 neutrophils per high-power field (HPF) in at least 5 separate high-power fields, that is diagnostic of a periprosthetic joint infection."
Candidates often fail to specify the "high-power field" requirement or the number of fields needed (the "5-5" rule). Failing to mention that this is a gold-standard adjunct to synovial fluid analysis—especially in cases where cultures are negative—is also a missed opportunity to show senior-level reasoning.
A high-scoring answer defines the histopathology criteria clearly: "The presence of >5 neutrophils per high-power field (HPF) in at least 5 high-power fields is a major criterion for PJI diagnosis. This is an essential investigation, particularly in 'culture-negative' scenarios or low-virulence infections like C. acnes, where synovial fluid analysis might be misleading. I would correlate these findings with my preoperative systemic inflammatory markers (ESR/CRP) and synovial fluid analysis to reach a definitive diagnosis before planning a two-stage revision."
