Predicting 5-Year Mortality After Prosthetic Joint Infection Using a 30-Item Accumulated Frailty Index in a 13,371-Patient Multicenter Cohort

Background Prosthetic joint infection (PJI) involves a significant mortality risk, with 26-30% of patients dying within 5 years. Current risk assessment tools offer limited prognostic accuracy for PJI patients. This study aimed to develop a prognostic model for 5-year all-cause mortality after PJI using age and frailty assessments. Methods We conducted a retrospective cohort study using TriNetX electronic health record data from 13,371 PJI patients diagnosed before 2021. We developed a 30-item Accumulated Frailty Index (AFI-Core30) that incorporates comorbidities, physiologic deficits, medications, and functional status. Generalized additive modeling was used to predict 5-year mortality, with 80% of data allocated for training and 20% for validation. Model performance was assessed using discrimination metrics and calibration techniques. Results The mean patient age was 63.1 ± 11.4 years, with an overall 5-year mortality rate of 13.1%. Both AFI-Core30 and age independently predicted mortality (odds ratio per 0.1 AFI increase=1.84, 95% confidence interval: 1.74-1.95, P < .001; odds ratio per 10-year increase in age=1.65, 95% confidence interval: 1.56-1.74, P < .001). The model demonstrated good discrimination (validation area under the receiver operating characteristic curve 0.712) and excellent calibration (Brier score 0.103). Mortality risk ranged from 2.6% in young, nonfrail patients to 50.4% in older, frail individuals. Conclusions This validated prognostic model offers the first large-scale, frailty-based tool for predicting mortality in PJI patients. The framework allows for evidence-based risk assessment and personalized treatment planning, shifting PJI prognostication from subjective judgment to objective risk measurement for better clinical decision-making.