Abstract: BACKGROUND: There are many studies on new fractures after percutaneous kyphoplasty, but less is reported on how to visualize the risk for clinical application.
OBJECTIVE: To investigate the risk factors for new vertebral compression fractures after percutaneous kyphoplasty for osteoporotic vertebral compression fractures and to establish a nomogram to predict the occurrence of postoperative new fractures.
METHODS: Totally 439 patients treated with percutaneous kyphoplasty for osteoporotic vertebral compression fractures admitted at the Affiliated Hospital of Xuzhou Medical University from December 2017 to June 2020 were enrolled, including 107 males and 332 females, aged (71.38±9.73) years. All patients were divided into a new fracture group and a non-fracture group according to the presence of new fractures within 1 year after surgery. Univariate and multivariate analyses were used to determine the risk factors for the occurrence of new fracture after surgery. Multiple interpolation of missing values was performed using the KNN method, and the samples were oversampled and equalized using the SMOTE method. The data were randomly divided into a training set (75%) and a testing set (25%). A nomogram predicting the risk of new fracture occurrence was created based on the results of multivariate analysis, and its performance was evaluated using receiver operating characteristic curve, calibration curve, and decision curve analysis. A web calculator was created to facilitate a more convenient interactive experience for clinicians.
RESULTS AND CONCLUSION: Univariate analysis showed significant differences (P < 0.05) between the two groups in T value, fracture history, cerebrovascular disease, injury time, and postoperative Cobb angle. Multivariate analysis showed that cerebrovascular disease [odds ratio (OR)=35.742, 95% confidence interval (CI) (9.377, 136.236),P=0.000], history of fracture [OR=11.546, 95% CI (5.420, 24.595), P=0.000], cemented intervertebral leakage [OR=2.817, 95% CI (1.109, 7.158), P=0.029] were the independent risk factors positively associated with new fractures. T value [OR=0.019, 95% CI (0.005, 0.076), P=0.000], and time to injury [OR=0.981, 95% CI (0.963, 0.999), P=0.041] were negatively associated with new fractures postoperatively. The area under the curve values of the nomogram were 0.927 [95% CI (0.864-0.989)] and 0.807 [95% CI (0.707-0.906)] in the training and test sets, respectively, and the calibration curves showed a high agreement between predicted and actual status with an area under the decision curve of 0.044 and 0.062, respectively. To conclude, low bone mineral density, cerebrovascular disease, fracture history, cemented intervertebral leakage, and short duration of injury are risk factors for new fractures after percutaneous kyphoplasty. 

Key words: osteoporosis, percutaneous kyphoplasty, vertebral compression fracture, nomogram, prediction model