Increased mortality after total hip prosthetic joint infection is mainly caused by the comorbidities rather than the infection itself

BACKGROUND AND PURPOSE: Periprosthetic joint infection (PJI) is a feared complication of arthroplasty surgery. There is controversy as to whether PJI also correlates with increased mortality. Our aim was to investigate in a nationwide cohort if PJI is an independent risk factor for dying. PATIENTS AND METHODS: We performed a retrospective cohort study based on data from the Swedish Hip Arthroplasty Register (SHAR). All patients with a revision THA performed between 1998 and 2017 were included. The outcome is mortality; exposure is PJI according to SHAR. The control group was study participants who underwent aseptic revision. Confounders were age, sex, diagnosis, and comorbidity according to the Elixhauser index. The outcome was analyzed with a Cox proportional hazards model. RESULTS: 4,943 PJI revisions and 12,529 non-infected revisions were included in the analysis. The median followup time was 4.1 years. In the PJI group, 1,972 patients died and in the control group, 4,512. The incidence rate ratio was 1.19 (95% confidence interval [CI] 1.13–1.25), the crude hazard ratio (HR) 1.19 (CI 1.13–1.25), and the adjusted HR 1.05 (CI 0.99–1.12) for the exposed versus the unexposed group. The strongest confounder was comorbidity. CONCLUSION: The increased mortality risk after revision due to PJI is mainly caused by the comorbidity of the patient, rather than by the infection itself.