The sample size will be calculated based on the incidence of postoperative delirium. Based on existing literature, the estimated incidence of postoperative delirium following TJA is around 10%. Using this estimate, a minimum sample size of 150 patients will be needed to detect the incidence with a precision of 5% and power of 80%. The sample size of 200 patients is needed to measure incidence to account for attrition.