Objective: To develop a predictive model based on preoperative quadriceps ultrasound measurements to determine frailty status in elderly patients undergoing abdominal surgery. Methods: The clinical data of 148 elderly patients who underwent abdominal surgery from July 2018 to June 2022 were retrospectively analyzed. The patients were assessed for frailty using the Fried Frailty Phenotype Assessment Scale after operation and divided into a no-frailty group (n=89) and a frailty group (n=59). The differences in the patient's clinical data, perioperative indexes, and imaging indexes were compared. The risk factors affecting the frailty status of elderly patients undergoing abdominal surgery were analyzed by logistic regression. The efficacy of the prediction model was evaluated by receiver operating characteristic (ROC) curve, with model validity confirmed through calibration curves and decision curve analysis (DCA). Results: The proportion of patients with age ≥80 and BMI ≥23 kg/m 2 in the frailty group was significantly higher than that in the no-frailty group (both P<0.01). The operation duration and postoperative hospital stay in the frail group were significantly longer the non-frail group, and the complication rate within postoperative 7 days was significantly higher than that in the non-frail group (all P<0.05). The cross-sectional area of rectus femoris muscle, vastus medialis muscle thickness, vastus intermedius muscle thickness, rectus femoris muscle thickness, and lateral femoris muscle thickness were significantly less in the frail group than those of the no-frail group (all P<0.001). Multifactorial logistic regression analysis showed that BMI, surgical duration, vastus medialis muscle thickness, vastus intermedius muscle thickness, rectus femoris muscle thickness, and lateral femoral muscle thickness were independent risk factors affecting frailty status in elderly patients undergoing abdominal surgery (all P<0.05). The predictive model demonstrated high accuracy with an AUC of 0.926. Conclusion: BMI and thickness of all quadriceps muscle components were significant factors affecting the frailty status of elderly patients undergoing abdominal surgery. In addition, the developed model, with excellent accuracy, offers a potential tool for preoperative risk assessment in this patient population.
