Abstract
Low bone mineral density (BMD) is a strong risk factor for vertebral fracture risk in osteoporosis. However, many fractures occur in people with moderately decreased or normal BMD. Our aim was to assess the contributions of trabecular microarchitecture and its heterogeneity to the mechanical behavior of human lumbar vertebrae. Twenty-one human L3 vertebrae were analyzed for BMD by dual-energy X-ray absorptiometry (DXA) and microarchitecture by high-resolution peripheral quantitative computed tomography (HR-pQCT) and then tested in axial compression. Microarchitecture heterogeneity was assessed using two vertically oriented virtual biopsies—one anterior (Ant) and one posterior (Post)—each divided into three zones (superior, middle, and inferior) and using the whole vertebral trabecular volume for the intraindividual distribution of trabecular separation (Tb.Sp*SD). Heterogeneity parameters were defined as (1) ratios of anterior to posterior microarchitectural parameters and (2) the coefficient of variation of microarchitectural parameters from the superior, middle, and inferior zones. BMD alone explained up to 44% of the variability in vertebral mechanical behavior, bone volume fraction (BV/TV) up to 53%, and trabecular architecture up to 66%. Importantly, bone mass (BMD or BV/TV) in combination with microarchitecture and its heterogeneity improved the prediction of vertebral mechanical behavior, together explaining up to 86% of the variability in vertebral failure load. In conclusion, our data indicate that regional variation of microarchitecture assessment expressed by heterogeneity parameters may enhance prediction of vertebral fracture risk. © 2010 American Society for Bone and Mineral Research.
Highlights
The risk of osteoporotic fracture is greater at skeletal sites where trabecular bone is predominant
Previous in vitro studies have demonstrated that the addition of trabecular microarchitecture to bone mineral density (BMD) improves the prediction of both trabecular bone mechanical behavior and vertebral strength.[3,4,5,6,7] using either histomorphometric methods or peripheral quantitative computed tomography or high-resolution peripheral quantitative computed tomography (HR-pQCT), previous studies have assessed the spatial variation of trabecular microarchitecture in vertebral bodies and shown that the structurally weak regions are located in the superior and anterior regions of the vertebral body.[8,9,10,11] Correlations between vertebral strength and trabecular microarchitecture parameters
The aim of this study was to determine the contribution of trabecular microarchitecture and its heterogeneity to the mechanical behavior of human lumbar vertebrae
Summary
The risk of osteoporotic fracture is greater at skeletal sites where trabecular bone is predominant (ie, femoral neck, vertebrae, and distal radius). Previous in vitro studies have demonstrated that the addition of trabecular microarchitecture to BMD improves the prediction of both trabecular bone mechanical behavior and vertebral strength.[3,4,5,6,7] using either histomorphometric methods or peripheral quantitative computed tomography (pQCT) or high-resolution peripheral quantitative computed tomography (HR-pQCT), previous studies have assessed the spatial variation of trabecular microarchitecture in vertebral bodies and shown that the structurally weak regions are located in the superior and anterior regions of the vertebral body.[8,9,10,11] Correlations between vertebral strength and trabecular microarchitecture parameters. Several clinical studies have shown that assessment of the intraindividual distribution of trabecular separation (Tb.SpÃSD) at the peripheral skeletal sites by HR-pQCT or MRI is useful for discrimination of previously fractured versus nonfractured controls,(13–17) but alternate parameters of heterogeneity have not been studied, nor have measurements of Tb.SpÃSD been performed directly on whole vertebrae.
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