Abstract: Objective To establish and test a 3-year prognosis model for elderly intertrochanteric fractures after intramedullary nail fixation.Methods A total of 205 elderly patients with intertrochoteric fracture of femur who underwent intramedullary nail fixation in our hospital from April 2019 to April 2021 were selected for observation study,followed up for 3 years after surgery,according to the Harris score, they were divided into the good group and the poor group.Univariate analysis was conducted to investigate the influencing factors of disease prognosis in the two groups 3 years after surgery.After the variables were screened by LASSO regression and cross-validation method,the independent influencing factors of the 3-year postoperative prognosis were analyzed by multi-factor Logistic-regression,and the prediction model of the nomogram was built,and the model was evaluated and validated.Results Among 205 elderly patients with intertrochanteric fractures of the femur who underwent intramedullary nailing fixation,201 were followed up for 3 years.Among them,148 patients had a Harris score of ≥70 points,while 53 patients had a score of <70 points.Univariate analysis results showed that the poor group had a higher proportion of patients with age,stroke,osteoporosis,Evans-Jensen type Ⅲ and Ⅳ fractures,poor intraoperative reduction,and a tip-apex distance of ≥30 mm compared to the good group,and had a lower lateral wall thickness than the good group,the difference was statistically significant (P < 0.05).LASSO regression analysis and cross-validation were used to screen variables.Multivariate Logistic regression analysis showed that stroke (OR=2.127,95%CI:1.478-3.061) and fracture Evans-Jensen classification Ⅲ (OR=1.149,95%CI:1.105-1.195) and type Ⅳ (OR=1.187,95%CI:1.143-1.233),intraoperative reduction was not good (OR=3.290,95%CI:2.319-4.668),apex distance ≥30mm (OR=1.413,95%CI:1.066-1.874) was an independent associated risk factor for disease outcome 3 years after surgery,the external wall thickness (OR=0.600,95%CI:0.4280.841) was an independent correlated risk factor for 3-year prognosis (P < 0.05).Based on the results of multiple factors,a nomogram prediction model was drawn,and the results showed that the model had certain predictive value for the disease outcome three years after surgery.The evaluation and verification results showed that when the threshold probability was 0-96%,the model had good clinical applicability and positive clinical net benefit.Conclusion Stroke,fracture Evans-Jensen classification Ⅲ and Ⅳ,poor intraoperative reduction,apical distance ≥30 mm,and lateral wall thickness are independent and relevant factors for 3-year prognosis of senile intertrochanteric fractures after intramedullary nail fixation.The establishment of a nematographic model has good predictive value for postoperative long-term prognosis and positive clinical net benefit.It can be used as an effective model to predict the long-term prognosis of postoperative disease.

Key words: old age, intertrochanteric fracture of femur, intramedullary nail fixation, postoperative prognosis, influencing factors, nomogram model, forecast