Trabecular Bone Score and incident fragility fracture risk in adults with reduced kidney function

Background and objective

Trabecular bone score is a gray–level textural measure obtained from dual energy x-ray absorptiometry lumbar spine images that provides information independent of areal bone mineral density. The association between trabecular bone score and incident fractures in adults with reduced kidney function and whether this association differs from that of adults with normal kidney function are unknown.

Design, setting, participants, and measurements 

We included 1426 participants ages ≥40 years old (mean age of 67 years) in the community–based Canadian Multicentre Osteoporosis Study. We stratified participants at cohort entry (2005–2008) by eGFR (eGFR<60 ml/min per 1.73 m² [n=199; 72.4% stage 3a, 25.1% stage 3b, and 2.5% stage 4] versus ≥60 ml/min per 1.73 m² [n=1227]). Trabecular bone score was obtained from lumbar spine (L1–L4) dual energy x-ray absorptiometry images, with a lower trabecular bone score representing worse bone structure. Over an average of 4.7 years follow-up (maximum follow-up of 5 years), we documented incident fragility (low–trauma) fracture events (excluding craniofacial, foot, and hand sites). We used a modified Kaplan–Meier estimator to determine the 5-year probability of fracture. Cox proportional hazard regression per SD lower trabecular bone score expressed the gradient of fracture risk.

Results

Individuals with an eGFR<60 ml/min per 1.73 m² who had a trabecular bone score value below the median (<1.277) had a significantly higher 5-year fracture probability than those above the median (18.1% versus 6.2%; P=0.01). The association between trabecular bone score and fracture was independent of bone mineral density and other clinical risk factors in adults with reduced and normal kidney function (adjusted hazard ratio per SD lower trabecular bone score: eGFR<60 ml/min per 1.73 m²: adjusted hazard ratio, 1.62; 95% confidence interval, 1.04 to 2.51; eGFR≥60 ml/min per 1.73 m²: adjusted hazard ratio, 1.44; 95% confidence interval, 1.13 to 1.83).

Conclusions

Lower lumbar spine trabecular bone score is independently associated with a higher fracture risk in adults with reduced kidney function. Additional study is needed to examine the association between trabecular bone score and fractures in individuals with diagnosed CKD-mineral and bone disorder.