S1 Vertebral Bone Quality Score Independently Predicts Proximal Junctional Kyphosis After Posterior Hemivertebra Resection With Transpedicular Instrumentation.

Abstract

Objective: Proximal junctional kyphosis (PJK) is a prevalent postoperative complication after posterior hemivertebra (HV) resection. Previous research has demonstrated a strong correlation between the development of PJK and reduced bone mineral density. The vertebral bone quality (VBQ) score, derived from magnetic resonance imaging, is considered a predictive and evaluative tool for bone mineral density. However, obtaining accurate magnetic resonance imaging signal intensity at the L1-L4 vertebrae is challenging in patients with HV. Consequently, a novel S1 VBQ score has been proposed, which exhibits high accuracy. This study aimed to evaluate the efficacy of S1 VBQ scores in predicting the incidence of PJK in these patients.

Methods: We conducted a retrospective analysis of patients diagnosed with HV who underwent posterior HV resection with transpedicular instrumentation at our department from 2010 to 2020. Comprehensive demographic and radiographic data were collected. To identify potential preoperative risk factors for the incidence of PJK, we utilized the least absolute shrinkage and selection operator method. Subsequently, a multivariate logistic regression model was constructed to evaluate the risk factors identified through the least absolute shrinkage and selection operator analysis. Cutoff values were determined through receiver operating characteristic analysis to assess the predictive value of the S1 VBQ score for PJK.

Results: A total of 88 patients met the inclusion criteria, with 14 patients (15.9%) developing PJK. Five potential risk factors were selected, including S1 VBQ scores, Risser sign, thoracic kyphosis, pelvic tilt, and proximal junctional angle. The multivariate logistic regression model demonstrated that the S1 VBQ score is an independent risk factor for predicting PJK. The area under the receiver operating characteristic curve (area under the curve) for S1 VBQ scores was 0.770 with an optimal threshold of 2.793 (sensitivity: 78.6%, specificity: 67.6%).

Conclusion: A higher S1 VBQ score is an independent risk factor for PJK, with a diagnostic accuracy of 77%. The S1 VBQ threshold of 2.793 was found to be effective in identifying PJK.

Level of evidence: Level III.