Measurement of C-reactive protein (CRP) levels as a screening test for acute periprosthetic joint infection has high sensitivity and low specificity. We performed the present study to analyze the causes of elevated CRP levels in the early postoperative period after primary total knee arthroplasty (TKA). This study is intended to help the postoperative care of patients through understanding the factors associated with postoperative elevation of CRP.
The records for 627 patients who underwent primary TKA between January 2005 and May 2013 were examined. We excluded 50 patients for whom TKA with inflammatory arthritis or revision TKA was performed. We measured serial CRP levels during the 4-week early postoperative period in all included cases to find the cases that showed a CRP pattern of elevation–depression–elevation (a bimodal pattern). We analyzed the causes of re-elevated CRP levels in patients with a bimodal pattern of CRP change.
Of the 577 included patients, 76 showed bimodal CRP elevation patterns. Eighteen elevations were caused by postoperative infections (periprosthetic infection), 10 by cardiovascular problems, 11 by gastrointestinal problems, 12 by urologic problems, 10 by respiratory problems, and 15 had unknown origins.
Our study shows that elevated CRP levels after TKA can have various causes. Although there may be other causes for an elevated CRP, it is essential to perform a work-up for prosthetic joint infections. In addition, there seems to be a need to evaluate noninfectious causes and infection of other sites, in addition to periprosthetic infection.