Bone Mass, Microstructure, and Strength Can Discriminate Vertebral Fracture in Patients on Long-Term Steroid Treatment

Context: Measurement of areal bone mineral density (aBMD) by dual-energy x-ray absorptiometry (DXA) was able to predict fracture risk. High-resolution peripheral quantitative computed tomography (HR-pQCT) yields additional information about volumetric bone mineral density (vBMD), microarchitecture, and strength that may increase our understanding of fracture susceptibility. Objective: To ascertain whether vBMD, microarchitecture, and estimated bone strength derived from HR-pQCT can discriminate vertebral fractures in patients with glucocorticoid-induced osteoporosis (GIOP) independent of aBMD. Design: A cross-sectional case-control study. Setting: Seven regional hospitals in Hong Kong. Patients: A total of 110 patients on long-term glucocorticoids with vertebral fracture, determined radiographically, and 110 patients on long-term glucocorticoids without fracture. Main Outcome Measures: We assessed vBMD, microarchitecture, and bone strength; aBMD; and fracture risk assessment tool (FRAX). Results: Patients with vertebral fracture had lower total vBMD and a thinner cortex at the distal tibia after adjustment for age, sex, and aBMD or FRAX. In the antiresorptive treatment-naive subgroup, patients with vertebral fracture also had lower total vBMD at both the distal radius and the tibia after adjustment for covariates. Lower total vBMD and a thinner cortex were also noticed in the nonosteoporotic or FRAX score of <10% subgroups with vertebral fracture and were also associated with increasing prevalence of vertebral fracture. Conclusion: Patients with GIOP and vertebral fracture have a significant reduction in total vBMD and cortical thinning independent of aBMD and FRAX. These changes may help identify high-risk patients in the subgroups currently considered to have low fracture risk as assessed by DXA or FRAX.