Predictive Value of the Preoperative Screw Trajectory-to-Vertebral Body Hounsfield Unit Ratio and the Combined Model Incorporating MRI-Based Pedicle Bone Quality Score for Pedicle Screw Loosening After Pedicle Screw Fixation

Study DesignRetrospective cohort study.ObjectivesThis study introduced the screw trajectory-to-vertebral body Hounsfield unit (HU) ratio as a novel parameter, evaluated its predictive value with the pedicle bone quality (PBQ) score for postoperative pedicle screw loosening, and develop a nomogram for risk prediction.MethodsRetrospective analysis included 313 patients undergoing pedicle screw fixation (2022-2024). Screw loosening was defined as a ≥1.0-mm radiolucent zone or double-halo sign on postoperative computed tomography (CT) or radiographs. Preoperative CT and magnetic resonance imaging (MRI) were used to calculate the HU ratio and PBQ score. Candidate predictors were selected based on univariable screening and clinical relevance; multivariable logistic regression was used to develop the prediction model and nomogram. Model performance was evaluated by area under the curve (AUC), Hosmer-Lemeshow test, and bootstrap validation. A sensitivity analysis was performed by additionally including 43 scoliosis patients (n = 356).ResultsAt 12 months follow-up, the loosening rate was 14.3% (45/313) in the patients. Independent risk factors included higher PBQ score, lower HU ratio, older age, and higher Goutallier grade. The nomogram showed excellent discrimination (apparent AUC = 0.904, 95% confidence interval [CI]: 0.856-0.953; optimism-corrected AUC = 0.883) and acceptable calibration (Hosmer-Lemeshow <i>P</i> = .393). At the optimal cutoff (predicted probability ≥0.212), sensitivity was 80.0% and specificity 88.1%. In sensitivity analysis, construct-related factors (fusion length and terminal fusion segment) became statistically significant, while overall model performance remained comparable.ConclusionsThe HU ratio is an independent predictor of postoperative pedicle screw loosening and complements the PBQ score.