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PJI after failed UKA best diagnosed with synovial fluid WBC test
The synovial fluid white blood cell count was the best single test for the diagnosis of deep periprosthetic joint infection in patients with failed unicompartmental knee arthroplasty, according this study.
“We found that the algorithm typically used for evaluation of a failed [total knee arthroplasty] TKA can be similarly useful for evaluation of the failed [unicompartmental knee arthroplasty] UKA,” the authors stated in the study.
In the retrospective review of 259 knees in 241 patients who had revision of a failed UKA, periprosthetic joint infection (PJI) was found in 10.8% of the patients reviewed. Researchers found that mean values for erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and synovial fluid white blood cell (WBC) count and differential were significantly higher among patients with PJI. The optimal cutoff values were 27 mm/h for the ESR, 14 mg/L for the CRP, 6200/mL for the synovial fluid WBC count and 60% polymorphonuclear cells for the differential.
Researchers found that the synovial fluid WBC count was the best test for diagnosing PJI in patients after a failed UKA. The next best test was the differential, followed by the ESR and the CRP, however they noted in the study that optimal synovial WBC counts for revised UKAs were somewhat higher than those use for TKA.
“Based on our findings, we recommend a preoperative erythrocyte sedimentation rate and C-reactive protein followed by an aspiration if abnormal,” the researchers stated. “The optimal cutoff values presented here should be validated by other studies to confirm our findings.”
Disclosure: The researchers reported no relevant financial disclosures.
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Schwartz AJ. J Arthroplasty. 2012;doi:10.1016/j.arth.2012.03.033.