Trend of serum C-reactive protein is associated with treatment outcome of hip Periprosthetic joint infection undergoing two-stage exchange arthroplasty: a case control study.

Background: Serum C-reactive protein (CRP) trends are critical for monitoring patients' treatment response following a two-stage exchange arthroplasty for periprosthetic joint infection (PJI) of the hip. However, CRP trends are poorly described in the literature. The primary aim of this study was to identify the relationships between PJI treatment outcomes and our proposed CRP trend definitions, parameters, and microbiological data. The secondary aim was to investigate CRP trends after the occurrence of spacer-related complications.

Methods: We conducted a retrospective review of 74 patients treated with a two-stage exchange protocol for PJI in a tertiary referral joint center between 2014 and 2016. Patients with factors that may affect CRP levels (inflammatory arthritis, concomitant infections, liver and kidney diseases, and intensive care admissions) were excluded. CRP trends were categorized into five types and PJI treatment outcome was defined as "success" or "failure" according to the Delphi criteria.

Results: Treatment was successful in 67 patients and failed in 7 patients. Multivariate logistic regression analysis showed that type 5 CRP, defined as serum CRP fluctuation without normalization after first stage surgery (odds ratio [OR]: 17.4; 95% confidence interval [CI]: 2.3-129.7; p = 0.005), and methicillin-resistant Staphylococcus aureus (MRSA; OR: 14.5; 95% CI: 1.6-131.7; p = 0.018) were associated with treatment failure. Spacer-related complications occurred in 18 patients. Of these, 12 had elevated CRP levels at later follow-up, while six had no elevation in CRP levels.

Conclusions: We found that MRSA infection and type 5 CRP were associated with PJI treatment failure.