Impact of Frailty on Outcomes of Total Joint Replacement and Differentiating the Impaction of Comorbidity and Frailty

Background: Frailty is a reduced capacity to recover from a physiologically stressful event. It is well established that preoperative frailty is associated with poor postoperative outcomes, Comorbidity often overlap with frailty in the patients and the known risk factors for frailty. No large-scale studies have explored the extent to which frailty impacts outcomes among TJA and it is also unclear the contributions of frailty and its interactions with comorbidity following anesthesia and TJA. Methods: Discharge data of 2,029,843 patients who underwent TJA between 2005 and 2014 from the National Inpatient Sample (NIS) database was analyzed using cross-tabulations and multivariate regression modeling. Frailty was defined based on frailty-defining diagnosis clusters from the Johns Hopkins Adjusted Clinical Groups frailty-defining diagnosis indicator.Results：Among patients who underwent total joint replacement surgery, 50,385 (2.5%) were identified as frail. Frailty was highly associated with older age, especially those over the age of 80 years, female, black race, a high Charlson comorbidity index (CCI) of ≥3, emergency/urgent admission and teaching hospital. Frailty had a better predictive effect on in-hospital death and acute surgical complications, while comorbidity was associated with greater odds of acute medical complications. Notably, frailty did not show an enhancement of the predictive power of the Charlson comorbidity score for postoperative complications or in-hospital death. Furthermore, frailty was a good predictor for increased LOS and increased hospitalization costs. There was a synergistic interaction effect between frailty and Charlson comorbidity score on the OR for LOS and hospitalization costs. Conclusion: Frailty independently predicted postoperative surgical and medical complications. Frailty also had a synergistic interaction with comorbidity for patients who are preparing to undergo TJA.