Journal
SPINE JOURNAL
Volume 22, Issue 10, Pages 1642-1650Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.spinee.2022.05.008
Keywords
Bone microarchitecture; Osteopenia; QCT; Quantitative computed tomography; Spinal fusion; VBQ; Volumetric bone mineral density
Categories
Funding
- National Center For Advancing Translational Science of the National Institute of Health [UL1TR002384]
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This study demonstrates the association between VBQ score and trabecular microstructure determined by mu CT for the first time. Bone microstructure and VBQ score exhibit significant differences in patients with impaired vBMD. However, the predictive ability of the VBQ score for osteopenia/osteoporosis is moderate.
BACKGROUND CONTEXT: Osteoporosis is a risk factor for instrumentation failure in spine surgery. Bone strength is commonly assessed by bone mineral density (BMD) as a surrogate marker. However, BMD represents only a portion of bone strength and does not capture the qualitative dimensions of bone. Recently, the magnetic resonance imaging (MRI)-based vertebral bone quality (VBQ) score was introduced as a novel marker of bone quality. However, it is still unclear if the VBQ score correlates with in-vivo bone microstructure. PURPOSE: The aims of the study were (1) to demonstrate differences in MRI-based (VBQ) and in-vivo (microcomputed tomography; mCT) bone quality between osteopenic/osteoporotic and nor-mal bone, (2) to show the correlation between VBQ, bone microstructure and volumetric BMD (vBMD), and (3) to determine the predictive value of the VBQ score for the prevalence of osteope-nia/osteoporosis. STUDY DESIGN/SETTING: Retrospective cross-sectional study. PATIENT SMPLE: 267 patients who underwent posterior lumbar fusion surgery from 2014 to 2021 at a single academic institution. Bone biopsies were harvested intraoperatively in 118 patients.OUTCOME MEASURES: VBMD, VBQ score, and bone microstructure parameters derived from mu CT. METHODS: Quantitative computed tomography (QCT) measurements were performed at the lumbar spine and the L1/L2 average was used to categorize patients with a vBMD & LE;120mg/cm3 as osteopenic/osteoporotic. The VBQ score was determined by dividing the median signal intensity of the L1-L4 vertebrae by the signal intensity of the cerebrospinal fluid using sagittal T1-weighted MRI scans. Intraoperative bone biopsies from the posterior superior iliac spine were obtained and evaluated with mu CT. VBQ scores and mu CT parameters were compared between the normal and the osteopenic/osteoporotic group. Correlations between VBQ score, mu CT parameters and vBMD were assessed with Spearman's correlation (p). Receiver operating characteristic (ROC) analysis was performed to determine the VBQ score as a predictor for osteopenia/osteoporosis. Multiple lin-ear regression analysis with vBMD L1/L2 as outcome was used to identify independent predictors from VBQ, mu CT parameters and demographics. RESULTS: 267 patients (55.8% female, age 63.3 years, BMI 29.7 kg/m2; n=118 with bone biopsy) with a prevalence of osteopenia/osteoporosis of 65.2% were analyzed. In the osteopenic/osteoporotic group the VBQ score, structured model index (SMI), and trabecular separation (Tb.Sp) were significantly higher, whereas bone volume fraction (BV/TV), connectivity density (Conn.D) and trabecular number (Tb.N) were significantly lower. There were significant correlations between VBQ and mu CT parameters ranging from p=-.387 to p=0.314 as well as between vBMD and mu CT parameters ranging from p=-.425 to p=.421, and vBMD and VBQ (p=-.300, p <.001). ROC analysis discriminated osteopenia/osteoporosis with a sensitivity of 84.7% and a specificity of 40.6% at a VBQ score threshold value of 2.18. Age, BV/TV and trabecular thickness (Tb.Th), but not VBQ, were significant independent predictors for vBMD (corrected R2=0.434). CONCLUSIONS: This study demonstrated for the first time that the VBQ score is associated with trabecular microstructure determined by mu CT. The bone microstructure and VBQ score were significantly different in patients with impaired vBMD. However, the ability to predict osteopenia/ osteoporosis with the VBQ score was moderate. The VBQ score appears to reflect additional bone quality characteristics and might have a complementary role to vBMD. This enhances our under-standing of the biological background of the radiographic VBQ score and might be a take-off point to evaluate the clinical utility of it as non-invasive screening tool for bone quality. (C) 2022 Elsevier Inc. All rights reserved.
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