Obesity Limits Utility of Vertebral Bone Quality Score for Opportunistic Osteopenia/Osteoporosis Screening in Cervical Surgery Patients.

Abstract

Study design: Comparative study.

Objective: The vertebral bone quality (VBQ) score is a validated opportunistic screening tool for bone mineral density (BMD). Obesity, often associated with hyperlipidemia and fat infiltration, may result in lower VBQ-derived BMD. However, studies have shown that dual-energy x-ray absorptiometry (DXA)-derived BMD tends to increase in obesity. Given this paradox, the aim of this study was to evaluate the effect of obesity on the utility of VBQ in opportunistic osteopenia/osteoporosis screening.

Methods: A total of 310 consecutive patients with degenerative cervical myelopathy were included. Body mass index (BMI) classified patients into underweight/normal, overweight, and obesity groups. Pearson's correlation assessed the associations of BMI with VBQ score, Hounsfield unit (HU) values, and T-score. The utility of VBQ score and HU values to discriminate normal BMD from osteopenia/osteoporosis was analyzed using receiver operating characteristic curve analysis and area under the curve (AUC).

Results: BMI was associated with lower VBQ score and higher T-score, but not with HU values. The correlation between VBQ score and T-score decreased with increasing BMI, eventually becoming nonsignificant in the obesity group (r = 0.241, P = .082). The VBQ score was not effective in identifying osteopenia/osteoporosis in the obese group (AUC = 0.59, P = .282). Compared with VBQ score, HU values were effective in several BMI subgroups (AUC = 0.75 to 0.88, P < .001).

Conclusion: The Cervical VBQ score is no longer a reliable indicator of DXA-derived BMD in obese patients. Even when the VBQ-derived BMD appears normal, it should not be solely relied upon to preclude further DXA evaluation.