98. Preoperative MRI-based vertebral bone quality (VBQ) score assessment in patients undergoing lumbar spinal fusion

BACKGROUND CONTEXT The importance of bone quality assessment in spine surgery is well recognized. The current gold standard for assessing bone mineral density is dual-energy X-ray absorptiometry (DEXA), however the majority of patients undergoing spinal fusion do not have preoperatively available DEXA data. Furthermore, DEXA has been shown to overestimate BMD in patients with spinal degenerative disease and obesity. Consequently, alternative radiographic measurements using data routinely gathered during preoperative evaluation of spine patients have been explored for the evaluation of bone quality and fracture risk. Opportunistic quantitative computed tomography and more recently the MRI-based vertebral bone quality (VBQ) score both have been shown to correlate with DEXA T-scores and predict osteoporotic fractures. However, to date the correlation between those two modalities has not been studied. PURPOSE The objective of this study was to assess whether the recently described novel VBQ score can predict the prevalence of QCT based osteopenia/osteoporosis and to evaluate the correlation between VBQ and spine QCT BMD measurements. STUDY DESIGN/SETTING Retrospective study of lumbar spinal fusion patients from a single, academic institution. PATIENT SAMPLE Patients undergoing lumbar spinal fusion from 2014-2019 with available preoperative CT and T1-weighted MRIs of the lumbar spine. OUTCOME MEASURES VBQ correlation to BMD. METHODS For BMD assessment, asynchronous quantitative computed tomography (QCT) measurements of L1-L2 were performed. An elliptical region of interest was placed anteriorly in the trabecular bone at mid-vertebral height and displaced from the vertebral cortex. The average BMD of L1-L2 was calculated and patients were categorized as either normal BMD (>120 mg/cm3) or osteopenic/osteoporotic ( RESULTS A total of 198 patients (53% female) were included in the study. The mean age was 62 years and the mean BMI was 28.2 kg/m2. The inter-observer reliability of the VBQ measurements was excellent (ICC of 0.90; 95% confidence interval: 0.82, 0.95). When comparing the patients with normal QCT BMD to those with osteopenia/osteoporosis, no significant differences existed in terms of sex, race, and BMI. However, the patients with osteopenia/osteoporosis were significantly older compared to the patients with normal BMD (64.9 vs 56.7 years, p CONCLUSIONS We found that the VBQ score significantly differentiates patients with normal BMD vs osteopenic/osteoporotic BMD based on QCT. However, the correlation between both modalities was only moderate suggesting VBQ might not measure bone density only. Due to the fact that QCT and more recently VBQ scores have both been shown to predict osteoporotic fractures, the weak correlation of the two modalities suggests that VBQ might not solely be a measurement of bone density, but rather bone quality. Since the two modalities seem to reflect different properties of bone, VBQ may be an interesting adjunct to clinically performed bone density measurements, rather than a substitution. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.