The 5-item Modified Frailty Index is a Predictor of Pulmonary Complications in Total Knee Arthroplasty

Background: The rate of Total Knee Arthroplasty (TKA) is increasing globally due to an aging population. Identifying which patients are at higher risk of complications, particularly pulmonary complications, will help in proper patient selection and reduced morbidity. Methods: This is a retrospective cohort study using data from the American College of Surgeons - National Surgical Quality Improvement Program (ACS-NSQIP) in the years 2018-2022. The pulomnary outocmes studied inlcuded: postoperative ventilator dependence, reintubation, pneumonia. In addition to individual variables, the Modified 5 item Frailty Index (mFI-5) was also studied as a potential predictor. Results: From the NSQIP database, de-identified information for N = 308,109 TKA patients (60.7% female; median age 68) was included in the study. 121 patients (0.039%) exhibited postoperative ventilator dependence >48 hours. 295 patients (0.096%) required unplanned intubation. 714 patients (0.23%) suffered from postoperative pneumonia. Univariate analysis showed that statistically significant relationships existed between postoperative ventilator dependence, reintubation, pneumonia and the variables of mFI-5, age, ASA class, smoking habits, sex, preoperative steroid use, type of anesthesia used, and BMI. Multivariate logistic regression controlling for confounders demonstrated statistically significant increases in the rates of ventilator dependence, unplanned intubation, and pneumonia with increasing mFI-5 levels: 0-1 (p = 0.0012), 1-2 (p < 0.0001), 2-3 (p < 0.0001), and 3-4 (p = 0.0126). The R2 for postoperative ventilator dependence was 4.3%, 5.3% for unplanned intubation, and 5.9% for pneumonia. Conclusions: The mFI-5 is a concise and effective tool for identifying the patients who would be at high risk for postoperative pulmonary complications, and can serve to provide appropriate patient centered information and perhaps lead to better planning and outcomes. There is a potential for reducing pulmonary complications of TKA when patients are appropriately stratified.