Trabecular bone score and vertebral fracture assessment in patients with fragility fractures

Background Trabecular bone score (TBS), vertebral fracture assessment (VFA) and bone mineral density (BMD) affords information of bone strength and fracture risk. Further understanding of the contribution of each of them in post-fracture risk assessment is of interest to improve identification of individuals at high risk of subsequent fractures and to set screening strategies for fracture patients. In patients with recent fragility fractures, we studied risk factors for fracture, TBS, prevalence of semiquantitatively assessed vertebral fractures (SQ1-SQ3 fractures) using VFA and assessed BMD using dual energy x-ray absorptiometry. The objectives were to explore i) the clinical characteristics, prevalence of low TBS and SQ1-SQ3 fractures in patients with fractures, ii) the differences between the sexes and between patients with and without vertebral fractures, iii) the risk factors for fractures including TBS, proportion of SQ1-SQ3 fractures and BMD in patients with different types of fragility fractures, iv) the differences between patients with central and peripheral fractures and v) the determinants of TBS and SQ1-SQ3 fractures and the interaction between these. Methods This cross-sectional study included a total of 839 women and men above 50 years of age who recently had sustained a fragility fracture. A total of 771 had TBS calculated, 679 had VFA performed, 804 had BMD of the total hip, femoral neck and/or spine, and 696 had responded to a questionnaire about risk factors for fracture. Paper I included all these patients. Of these, 495 women and 119 men who all had valid measurement of TBS, VFA and BMD of the femoral neck, total hip and lumbar spine were included in paper II. Paper III included 496 women who all had responded to a questionnaire about risk factors for fracture, had valid measurements of TBS and BMD of femoral neck and/or lumbar spine and 423 had VFA performed. Results Paper I: The mean age of the patients was 65.8 years and 80.5% were women. The prevalence of low TBS (≤ 1.23) was 34.0% and 34.8% had SQ1-SQ3 fractures. The proportion of patients with osteoporosis (BMD T-score ≤ -2.5) at the femoral neck was 13.8% and the skeletal site with lowest BMD T-score 27.4%. Women exhibited lower mean TBS and lower BMD at all sites than men. Patients with SQ1-SQ3 fractures were older, had lower TBS and lower BMD at all sites than those without SQ1-SQ3 fractures (all p < 0.05). Paper II: Patients with centrally sited fractures exhibited lower mean TBS and a higher proportion of both SQ1-SQ3 fractures, SQ2-SQ3 fractures and SQ3 fractures and lower BMD of the femoral neck, total hip and lumbar spine than patients with peripherally sited fractures (all p < 0.05). Paper III: Higher age, a history of parental hip fracture and daily alcohol intake were associated with lower TBS. Higher BMD of the femoral neck and lumbar spine were associated with higher TBS. Age and prior fragility fractures were positively associated with SQ1-SQ3 fractures, while lumbar spine BMD was negatively associated with SQ1-SQ3 fractures. No association between TBS and SQ1-SQ3 fractures was found. Conclusions More than half of the patients with fragility fractures had SQ1-SQ3 fractures, low TBS or both. Patients with central fragility fractures exhibited lower TBS, a higher prevalence of SQ1-SQ3 fractures and lower femoral neck BMD than patients with peripheral fractures. This suggests that patients with central fragility fractures have a higher risk of subsequent fractures and should get the highest priority in secondary fracture prevention. No association between TBS and SQ1-SQ3 fractures was found; hence they may act as independent risk factors, justifying the use of both in post-fracture risk assessment