Abstract: BACKGROUND: Postoperative delirium is one of the serious complications after total knee arthroplasty, usually occurring 1-5 days after surgery, with confusion and cognitive impairment as the main manifestations, which is not conducive to the recovery of joint function in elderly patients. At present, the risk factors affecting delirium after total knee arthroplasty in the elderly are not clear, and there is a lack of clinical prediction studies to directly present them for promotion and application.
OBJECTIVE: To explore the risk factors of delirium after total knee arthroplasty in elderly patients and establish a prediction model of nomogram. 
METHODS: Medical record data of 116 elderly patients receiving total knee arthroplasty treated in Ganzhou Hospital of Traditional Chinese Medicine, Jiangxi University of Chinese Medicine from January 2019 to December 2021 were retrospectively analyzed, of which 29 elderly patients with delirium after total knee arthroplasty were selected as the observation group, and the remaining 87 elderly patients without delirium after total knee arthroplasty were selected as the control group. Preoperative general clinical data, laboratory examination results, and surgical data were compared between the two groups. Multivariate Logistic regression analysis was used to analyze risk factors for delirium after total knee arthroplasty in elderly patients. The receiver operating characteristic curve was used to analyze the independent risk factors and obtain the best cut-off value. The nomogram model was constructed by R software. 
RESULTS AND CONCLUSION: (1) There were significant differences in age, cerebrovascular accident history, preoperative hospital stay, preoperative albumin, hemoglobin, American Society of Anesthesiologists classification, operation time, anesthesia time, and intraoperative blood transfusion volume between the two groups (P < 0.05). (2) Multivariate Logistic regression analysis showed that old age, long hospital stay before surgery, high American Society of Anesthesiologists classification grade, and long operation time were risk factors for postoperative delirium in elderly knee arthroplasty patients, while high albumin and high hemoglobin were protective factors for postoperative delirium in elderly knee arthroplasty patients. (3) The areas under the curve of age, preoperative hospital stay, albumin, hemoglobin, American Society of Anesthesiologists classification grade, and operation time were 0.784, 0.706, 0.853, 0.762, 0.617, and 0.542, respectively. The optimal cut-off values were 75 years, 7 days, 40 g/L, 125 g/L, 3 and 200 minutes, respectively. (4) After internal data for verification, the consistency index was 0.974. The actual curve of the model was in good agreement with the ideal curve. (5) These results indicate that this nomogram model based on old age, long hospital stay, high American Society of Anesthesiologists classification grade, low albumin, low hemoglobin, and long operation time has far-reaching clinical significance for early identification, early warning and diagnosis of delirium risk in elderly patients after total knee arthroplasty.

Key words: elderly patient, total knee arthroplasty, postoperative delirium, nomogram, prediction model