Risk factors and predictive model for prolonged length of stay after spinal tuberculosis lesion removal and bone graft fusion with internal fixation

English Keywords:Spinal tuberculosis  Spinal fusion  Length of stay  Risk factors  Nomogram

English Abstract:

  【Abstract】 Objectives: To analyze the risk factors for prolonged length of stay(LOS) after lesion removal and bone graft fusion internal fixation in patients with spinal tuberculosis, and to develop and validate a predictive model. Methods: The clinical data of 152 patients with spinal tuberculosis who underwent lesion removal and bone grafting and fusion internal fixation at Honghui Hospital affiliated to Xi′an Jiaotong University from February 2016 to December 2020 were retrospectively analyzed. The patients were divided into the prolonged LOS(PLOS) group and normal LOS(NLOS) group according to whether their postoperative LOS exceeded the postoperative LOS of the 75th percentile of the overall study cohort. Univariate analyses were performed for gender, age, hypertension, diabetes, paraplegia, anticoagulation history, tuberculosis resistance, preoperative anti-tuberculosis time, blood transfusion, surgical site, surgical approach, number of fused vertebrae, operative time, intraoperative blood loss(IBL), postoperative complications, blood transfusion cost, hospital cost, C-reactive protein(CRP), erythrocyte sedimentation rate(ESR), albumin(ALB), blood routine, and coagulation function in both groups. Based on Lasso regression, the risk factors significantly associated with postoperative LOS prolongation in spinal tuberculosis were selected and incorporated into a multivariate logistic regression analysis, and thereby a prediction model was established based on the results of multivariate logistic regression analysis. The model was visualized by plotting a nomogram as a means of predicting the probability of risk for prolongation of LOS after spinal tuberculosis surgery. Internal validation of the model was performed using extended Bootstrap, where receiver operating characteristic(ROC) curves, calibration curves and decision curve analysis(DCA) were plotted to verify the discrimination, accuracy and clinical applicability. Results: The 152 patients enrolled in the study had a median LOS of 10d, and the 75% LOS was 14d. There were 96 patients in the PLOS group and 56 in the NLOS group. Univariate analysis showed that the differences in age, hypertension, diabetes, anticoagulation history, tuberculosis resistance, preoperative anti-tuberculosis time, surgical site, surgical approach, surgical time, IBL, postoperative complications, CRP, ESR, preoperative ALB, blood routine, and coagulation function were not statistically significant between the two groups(P>0.05), while the differences in gender, paraplegia, blood transfusion, number of fused vertebrae, blood transfusion cost, and hospitalization cost were statistically significant(P<0.05). The operative time, IBL, preoperative Hb, and preoperative ALB were divided according to the Yoden index of ROC as the dividing point, and the cut-off value of operative time was 198(min), the cut-off value of IBL was 1000(mL), the cut-off value of preoperative Hb was 118(g/L), and the cut-off value of preoperative ALB was 38.8(g/L). Through Lasso regression model, the risk factors closely related to the prolongation of LOS after spinal tuberculosis were female, blood transfusion, the number of fused vertebrae≥3, operative time≥198min and IBL≥1000mL, preoperative Hb <118g/L and preoperative ALB <38.8g/L. Multivariate logistic regression analysis showed that female, number of fused vertebrae≥3, operative time≥198min and IBL≥1000mL were the risk factors for postoperative LOS prolongation in patients with spinal tuberculosis(P<0.05). A visual nomogram model for logistic regression was constructed, and the predictors included female, number of fused vertebrae, operative time, and IBL. A Bootstrap self-sampling of 1,000 times was performed to complete the internal validation of the model, with a C-index value of 0.882 and an area under the curve(AUC) of ROC of 0.884(95% CI: 0.782 to 0.985). The calibration curve showed that the apparent curve of the model fitted well with the curve after deviation correction. The DCA curve showed that the threshold range of 0.2 to 0.9 had the greatest clinical benefit. Conclusions: Female, number of fused vertebrae≥3, operative time≥198min and IBL≥1000mL are the main risk factors for prolonged LOS after lesion removal and bone graft fusion with internal fixation in patients with spinal tuberculosis, and the predictive model based on the above risk factors can help physicians to make clinical decisions and optimize the perioperative management.