Over 13 months we prospectively monitored C-Reactive Protein (CRP) to assess surgical site infection (SSI) in 148 patients undergoing hip arthroplasty, including 34 hemiprostheses for femoral neck fracture, 35 hemiprostheses for osteosynthesis failure, 17 primary total hip arthroplasties (THAs) and 62 revisions of hemi-arthroplasty or THA. Ten patients who had probably had interaction with CRP were included.

In four out of seven patients with SSI, CRP values peaked three days after the operation, compared to eight out of 131 without SSI (p =0.0001). This gives a 60% sensitivity for detecting SSI by the CRP curve, with a specificity of 94%. The positive predictive value was 33%, and the negative predictive value 98%.

Previous studies have established the normal CRP curve after major joint replacement surgery. This study shows that a peak in CRP after day three may indicate SSI, or point to other deep infections such as pneumonia.