Osteoporotic Fracture Risk Predicted by Vertebral Trabecular Attenuation on Routine CT

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Multivariate analysis demonstrated a persistent modest effect of L<sub>1</sub> attenuation on fracture-free survival.
Multivariate analysis demonstrated a persistent modest effect of L1 attenuation on fracture-free survival.

Decreased L1 vertebral trabecular attenuation of ≤90 Hounsfield units (HU) measured on routine body computed tomography (CT) scans could identify risk for future osteoporotic fractures in older adults, according to a retrospective study published in the Journal of Bone and Mineral Research.

A total of 1966 consecutive older adults underwent chest or abdominal CT over the course of 1 year for a variety of indications. Investigators retrospectively evaluated the utility of measuring trabecular attenuation of the first lumbar vertebra to determine whether this measure predicted the risk for future fractures at varying skeletal sites. Data on the incidence of fracture were obtained from each patient's electronic health record and were categorized according to the International Classification of Diseases (ICD)-9 codes for vertebral, hip, and extremity fractures.

In the final analysis, 507 patients were eligible for analysis and were followed for a median of 5.8 years (interquartile range 2.1 to 11.0 years) after the CT scan. Investigators found that L1 attenuation values ≤90 HU were associated with reduced fracture-free survival during long-term follow-up (P <.001 by log-rank test). A multivariate analysis that adjusted for age, sex, prior fracture, bisphosphonate use, cancer history, chronic kidney disease, ethanol abuse, glucocorticoid use, tobacco use, and a history of rheumatoid arthritis found a persistent association between L1 attenuation and fracture-free survival (hazard ratio [HR], 0.63 per 10-unit increase; 95% CI, 0.47-0.85).

The retrospective design of the study population likely introduced heterogeneity with regard to clinical fracture risk factors, which potentially limits the findings. There may have also been significant variation in scanner acquisition parameters among CT operators, which limit the study's generalizability.

Investigators noted that automation of attenuation measurement could be scaled to a larger population level and “would likely increase the precision of attenuation measurements and reliability of monitoring bone mineral density changes over time.”

Reference

Lee SJ, Graffy PM, Zea RD, Ziemlewicz TJ, Pickhardt PJ. Future osteoporotic fracture risk related to lumbar vertebral trabecular attenuation measured at routine body CT [published online February 5, 2018]. J Bone Miner Res. doi:10.1002/jbmr.3383

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