The utility of MRI-based S1 vertebral bone quality score in assessing bone mineral density for adolescent idiopathic scoliosis.

BACKGROUND

Several studies have confirmed that magnetic resonance imaging (MRI) vertebral bone quality (VBQ) score can be used as a tool for opportunistic osteoporosis screening. However, obtaining the original VBQ score for patients with adolescent idiopathic scoliosis (AIS) can be challenging, especially in cases of severe scoliosis, and its stability may be affected. We aimed to assess the diagnostic potential of the VBQ method based on T1-weighted MRI of the first sacral vertebra (S1) in assessing bone mineral density (BMD) for patients with AIS.

METHODS

A total of 137 patients with AIS were retrospectively enrolled in the study. The S1 VBQ score and S1 Hounsfield units (HU) were measured based on MRI and computed tomography (CT), respectively. The S1 VBQ score was calculated based on the T1-weighted signal intensity of the S1 vertebra. Univariate analysis was performed to compare the differences between the normal-BMD cohort (QCT Z-score >-2.0) and low-BMD cohort (QCT Z-score ≤-2.0). Pearson correlation analysis was applied to determine the associations among S1 VBQ, S1 HU, and QCT Z-score. Independent factors associated with low BMD were determined through multivariate logistic regression. A receiver operating characteristic analysis was performed to assess the diagnostic performance of S1 VBQ in assessing low BMD.

RESULTS

Among the included patients, there were 93 in the normal-BMD group and 44 in the low-BMD group. A significantly higher S1 VBQ score was found in the low-BMD cohort than in the normal-BMD cohort (P<0.001). There was a moderate correlation of S1 VBQ with QCT Z-score (r=-0.450; P<0.001) and S1 HU (r=-0.405; P<0.001). The S1 HU had a strong correlation with the QCT Z-score (r=0.671; P<0.001). The multivariate logistic regression analysis revealed that the S1 VBQ score was independently correlated with low BMD [odds ratio =3.394; 95% confidence interval (CI): 1.498-7.689; P=0.003]. An S1 VBQ score threshold of 3.2 yielded 86.4% sensitivity, 74.2% specificity, and an area under the curve of 0.836 in identifying low BMD.

CONCLUSIONS

The MRI-S1 VBQ score provides a novel means for assessing BMD in patients with AIS. It could serve as a tool for the opportunistic screening of low BMD before spinal surgery.