Normative Data and Reproducibility for Vertebral Bone Quality Score in Serial Lumbar Spine Magnetic Resonance Imaging

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The vertebral bone quality (VBQ) score can independently predict fragility fractures and is useful for osteoporosis screening. It is derived by taking the ratio of the median L1-L4 signal intensity (SI) and L3 cerebral spinal fluid SI on opportunistic T1 weighted (fat sensitive) magnetic resonance imaging (MRI) scans. Higher VBQ score indicates more fat and less bone suggesting osteoporosis. Normative data has not been described. The purpose of this study was to determine whether VBQ score increased with age and remained consistent across serial MRI studies. This retrospective study evaluated 107 lumbar spine patients, age 20-69, who received two T1-weighted MRI within three months of each other between January 2011 and December 2021. Patients were divided into cohorts by decade of life. Patients with prior vertebral fracture, spinal metastasis, instrumentation at two or more levels, and MRI scans with spin sequences outside the optimal range for bone marrow analysis (TR=400-850, TE=8-20) were excluded. Regression analysis was performed to determine correlation of VBQ score with age. Interclass correlation (ICC) was calculated to determine reproducibility between VBQ scores derived from separate MRI scans. 53 males and 54 females were included in the study. 90% were Caucasian. The mean VBQ scores for the first and second set of MRI scans were 2.39±0.74 and 2.30±0.88, 2.68±0.57 and 2.54±0.74, 2.56±0.63 and 2.70±0.69, 2.99±0.72 and 2.77±0.89, 3.27±0.57 and 3.21±0.60 for the age ranges of 20-29, 30-39, 40-49, 50-59, 60-69, respectively. Among males, age positively correlated with VBQ scores measured from the first (r=0.361, p=0.008) and second (r=0.286, p=0.038) MRI scans. Among females, age likewise positively correlated with VBQ scores measured from the first (r=0.395, p=0.003) and second (r=0.398, p=0.003) MRI scans. For the entire cohort, the ICC=0.749. VBQ score is positively correlated with age. The majority of patients age > 50 had VBQ > 3.00, further supporting this threshold as a diagnostic cutoff for potential osteoporosis and additional bone health evaluation. Reproducibility of the VBQ score across serial MRI is good, which supports the possible usefulness of the VBQ score in the pre-operative evaluation of spine surgical patients.