Assessment of the Risk Factors Related to the Length of Hospital Stay and Postoperative Complications in Patients Undergoing Primary Total Knee Arthroplasty.

 To assess the risk factors involving longer hospital stays and early postoperative complications (first 30 days after surgery) in patients undergoing total knee arthroplasty (TKA).  A cross-sectional study was conducted with collection of data of patients who underwent TKA in a private hospital between 2015 and 2019. The following data were collected: age, gender, body mass index, and clinical comorbidities. We also collected intraoperative data such as the grade on the classification of the American Society of Anesthesiologists (ASA), the duration of the surgery, the length of stay, the postoperative complications, and readmission within 30 days. Statistical models were used to investigate the possible risk factors associated with longer hospital stays and postoperative complications.  There was evidence of an increase in the length of hospital stay in older patients, with higher grades on the ASA classification or who suffered postoperative complications. For each increase in 1 year of age, we expect the length of stay to be multiplied by 1.008 (95% confidence interval [95%CI]: 1.004 to 1.012;  < 0,001). In patients who were ASA grade III, the time is expected to be multiplied by 1.297 (95%CI: 1.083 to 1.554;  = 0,005) when compared with grade-I patients. In patients who suffered postoperative complications, the time is expected to be multiplied by 1.505 (95%CI: 1.332 to 1.700;  < 0.001) compared with patients without complications.  The present study demonstrated that, in patients who underwent primary TKA, preoperative characteristics such as older age and ASA grade ≥ III, as well as the development of postoperative complications, independently predict the increase in the length of hospital stay.