Osteoporotic fractures are a vital public health concern and create a great economic burden for our society. It is estimated that more than 2 million fractures occur in the United States at a cost of $17 billion each year. Deterioration of microarchitecture of trabecular bone is considered as a major contributor to bone fragility. Current clinical imaging modalities such as Dual-energy X-ray absorptiometry (DXA) are not able to describe bone microarchitecture due to their low resolution. The main objective of this study was to obtain the relationship between stochastic parameters calculated from bone mineral density (BMD) maps of DXA scans and the microarchitecture parameters measured from three dimensional (3D) images of human lumbar vertebrae acquired using a Micro-Computed Tomography (Micro-CT) scanner. Eighteen human lumbar vertebrae with intact posterior elements were scanned in the posterior-anterior projection using a DXA scanner. Stochastic parameters such as correlation length (L), sill variance (C) and nugget variance ( ) were calculated by fitting a theoretical model onto the experimental variogram of the BMD map of the human vertebrae. In addition, microarchitecture parameters such as bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), trabecular number (Tb.N), connectivity density (Conn.Dn), and bone surface-to-volume ratio (BS/BV) were measured from 3D images of the same human lumbar vertebrae. Significant correlations were observed between stochastic predictors and microarchitecture parameters of trabecular bone. Specifically, the sill variance was positively correlated with the bone volume fraction, trabecular thickness, trabecular number, connectivity density and negatively correlated with the bone surface to volume ratio and trabecular separation. This study demonstrates that stochastic assessment of the inhomogeneity of bone mineral density from routine clinical DXA scans of human lumbar vertebrae may have the potential to serve as a valuable clinical tool in enhancing the prediction of risks for osteoporotic fractures in the spine. The main advantage of using DXA scans is that it would be cost effective, since most hospitals already have DXA machines and there would be no need for purchasing new equipment.

Date of publication

Spring 3-23-2015

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