External Validation Demonstrates Limited Clinical Utility of a Preoperative Prognostic Calculator for Periprosthetic Joint Infection

Abstract Background Preoperative calculation of treatment failure risk in patients undergoing surgery for periprosthetic joint infection (PJI) is imperative to allow for medical optimization and targeted prevention. A preoperative prognostic model for PJI treatment failure was previously developed and this study sought to externally validate the model. Methods A retrospective review was performed of 380 PJIs treated at two institutions. The model was used to calculate the risk of treatment failure, and receiver operating characteristic curves were generated to calculate the area under the curve (AUC) for each institution. Results When applying this model to Institution 1, an AUC of 0.795 (95% confidence interval [CI]: 0.693-0.897) was found, while Institution 2 had an AUC of 0.592 (95% CI: 0.502-0.683). Comparing all institutions in which the model had been applied to, we found Institution 2 represented a significantly sicker population and different infection profile. Conclusions In this cohort study, we externally validated the prior published model for Institution 1. However, Institution 2 had a decreased AUC using the prior model and represented a sicker and less homogenous cohort compared to Institution 1. When matching for chronicity of the infection, the AUC of the model was not affected. This study highlights the impact of comorbidities and their distributions on PJI prognosis and brings to question the clinical utility of the algorithm which requires further external validation.