The Effect of Retained Hardware on Failure Among Prosthetic Joint Infections of the Knee in the Presence and Absence of Staphylococcus aureus

Abstract

Abstract Background The risk of failure associated with different surgical strategies for prosthetic joint infections (PJIs) among patients with and without Staphylococcus aureus is uncertain. The purpose of this study was to assess whether S. aureus modifies the association between retained hardware and failure following revision surgery for PJI of the knee. Methods This was a single-center retrospective cohort study of 106 first PJIs of the knee between 2016 and 2020 at a rural academic medical center. The exposure was retained hardware following revision surgery for PJI, and the outcomes were recurrent infection, any infection, and a composite outcome including any infection, unplanned revision, failure to undergo reimplantation, amputation, or death within 2 years of revision. We used negative binomial regression to quantify the association between the exposure and outcome and to assess the presence of S. aureus as an effect modifier. Results Retained hardware was significantly associated with failure when defined as recurrent infection among S. aureus PJI (adjusted risk difference [aRD], 0.38; 95% CI, 0.12–0.64) but not in the absence of S. aureus (aRD, −0.02; 95% CI, −0.17 to 0.13), and S. aureus was an effect modifier (Pinteraction = .01). Conclusions We report a significant association between the presence of retained hardware and recurrent infection among S. aureus PJI of the knee, but not for non–S. aureus PJI. This could help inform the surgical management of PJI of the knee in cases where the microbiology is known before surgery.