Future Osteoporotic Fracture Risk Related to Lumbar Vertebral Trabecular Attenuation Measured at Routine Body CT

Abstract

We sought to determine if vertebral trabecular attenuation values measured on routine body computed tomography (CT) scans obtained for a variety of unrelated indications can predict future osteoporotic fractures at multiple skeletal sites. For this Health Insurance Portability and Accountability Act (HIPAA)-compliant and Institutional Review Board (IRB)-approved retrospective cohort study, trabecular attenuation of the first lumbar vertebra was measured in 1966 consecutive older adults who underwent chest and/or abdominal CT at a single institution over the course of 1 year. New pathologic fragility fractures that occurred after a patient's CT study date were identified through an electronic health record database query using International Classification of Diseases (ICD)-9 codes for vertebral, hip, and extremity fractures. Univariate and multivariate Cox proportional hazards regression were performed to determine the effect of L trabecular attenuation on fracture-free survival. Age at CT, sex, and presence of a prior fragility fracture were included as confounders in multivariate survival analysis. Model discriminative capability was assessed through calculation of an optimism-corrected concordance index. A total of 507 patients (mean age 73.4 ± 6.3 years; 277 women, 230 men) were included in the final analysis. The median post-CT follow-up interval was 5.8 years (interquartile range 2.1-11.0 years). Univariate analysis showed that L attenuation values ≤90 Hounsfield units (HU) are significantly associated with decreased fracture-free survival (p < 0.001 by log-rank test). After adjusting for age, sex, prior fracture, glucocorticoid use, bisphosphonate use, chronic kidney disease, tobacco use, ethanol abuse, cancer history, and rheumatoid arthritis history, multivariate analysis demonstrated a persistent modest effect of L attenuation on fracture-free survival (hazard ratio [HR] = 0.63 per 10-unit increase; 95% confidence interval [CI] 0.47-0.85). The model concordance index was 0.700. Ten-year probabilities for major osteoporosis-related fractures straddled the treatment threshold for most subcohorts over the observed L HU range. In conclusion, for patients undergoing body CT scanning for any indication, L vertebral trabecular attenuation is a simple measure that, when ≤90 HU, identifies patients with a significant decrease in fracture-free survival. © 2018 American Society for Bone and Mineral Research.

Does Nonenhanced CT-based Quantification of Abdominal Aortic Calcification Outperform the Framingham Risk Score in Predicting Cardiovascular Events in Asymptomatic Adults?

“…At all time points assessed, AAC was a better predictor of cardiovascular events than was FRS, as of opportunistic screening that adds potential value to the examination, without the need for additional patient time or radiation dose. Bone mineral density assessment for osteoporosis is another key emerging opportunistic screening add-on using abdominal CT (32)(33)(34); other examples include screening for abdominal aortic aneurysms, hepatic steatosis and iron overload, sarcopenia, and visceral fat (35)(36)(37)(38). Although these secondary or incidental screening opportunities have received the most attention in CT colonography (39,40), much greater impact and benefit could be derived from applying this to other clinical indications for abdominal CT, given the much larger volume of routine studies being performed (41).…”

The Value of Quantitative Musculoskeletal Imaging

“…32,36 Various attenuation thresholds can be used along the receiver operating characteristics curve, providing either more sensitive or more specific assessment, but the 90 HU threshold (at 120 kV) yields the best performance for both prevalent and future fractures. 37,38 In practice, osteoporosis should generally be suspected for L1 attenuation values < 100 HU, whereas 150 HU is a useful threshold for likely osteopenia.…”

<p>Dorsal and ventral thoracic 12 vertebra body height is associated with incident lumbar vertebral fracture in postmenopausal osteoporotic women</p>

“…According to the WHO, osteoporosis is defined as a BMD value of -2.5 below the mean value, measured at the femoral neck, total hip, or the lumbar spine (L1-L4). 1,33 The WHO suggests use of the fracture risk assessment tool (FRAX), without or with BMD measurement, to predict 10 years probabilities of major osteoporotic fractures and hip fractures. 22 However, discrepancies between actual LVF occurrences and risk predicted by DXA and FRAX exist.…”

“…LVF is the most common osteoporotic fracture. [1][2][3][4][5] The ability to predict risk factors for LVF is crucial because of the negative consequences of LVF that include chronic back pain, related functional disability, kyphosis, and height loss, all of which have major impacts on a patient's quality-of-life; as well as the associated increases in morbidity and mortalitiy. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Analysis of bone mineral density (BMD) using dual-energy X-ray absorptiometry (DEXA) is the most commonly used index of bone power, and a low BMD is the most important risk factor for LVF prediction.…”