Diagnostic Value of C-Reactive Protein and Serum White Blood Cell Count during Septic Two-Stage Revision of Total Knee Arthroplasties

Abstract

Aims and methods: In septic two-stage revision arthroplasty, the timing of reimplantation is crucial for therapeutic success. Recent studies have shown that singular values of C-reactive protein (CRP) and white blood cell count (WBC count) display weak diagnostic value in indicating whether periprosthetic joint infection (PJI) is controlled or not during two-stage revision surgery of knee arthroplasty. Therefore, in addition to the values of CRP and WBC, the course of CRP and WBC counts were compared between groups with and without later reinfection in 95 patients with two-stage revision (TSR) of infected total knee arthroplasties (TKA). Of these patients, 16 had a reinfection (16.84%).

Results: CRP values decreased significantly after the first stage of TSR in both the reinfection and no-reinfection groups. WBC count values decreased significantly in the no-reinfection group. Decrease in WBC count was not significant in the reinfection group. No significant difference could be found in either the CRP values or the WBC counts at the first stage of TSR, the second stage of TSR, or their difference between stages when comparing groups with and without reinfection. Area under the curve (AUC) values ranging between 0.631 and 0.435 showed poor diagnostic value for the calculated parameters. The courses of CRP over 14 days after the first stage of both groups were similar with near identical AUC.

Conclusions: CRP and WBC count as well as their course over 14 days postoperatively are not suitable for defining whether a PJI of the knee is under control or not.

Keywords: CRP; bone and joint infections; infection parameters; knee arthroplasty; orthopedic infections; periprosthetic joint infection; two-stage revision; white blood cell count.

Figure 1

Boxplots for C-reactive protein (CRP) values of the first stage of TSR and the second stage of TSR, grouped according to “no reinfection” and “reinfection”.

Figure 2

Boxplots for white blood cell count (WBC count) values of the first stage of TSR and the second stage of TSR, grouped according to “no reinfection” and “reinfection”.

Figure 3

Receiver operating characteristic curves for CRP values sampled prior to the second stage of TSR (CRP second stage) and ΔCRP (CRP second stage minus CRP first stage of TSR).

Figure 4

Receiver operating characteristic curves for WBC count values sampled prior to the second stage of TSR (WBC count second stage) and ΔWBC count (WBC count second stage minus WBC count first stage of TSR).

Figure 5

Area under the curve of mean CRP value for 14 days of follow-up after the first stage of TSR surgery of the “no reinfection” group (a), in green, and the “reinfection” group (b), in orange.