Trabecular rod buckling index in thoraco-lumbar vertebral bonedagger.

The need for improved mechanistic understanding of cancellous bone failure is at the core of important clinical problems such as osteoporosis, as well as basic biological issues such as bone formation and adaptation. Three-dimensional (3D) anaglyphs were produced from 15 T12 and L1 vertebral bodies, which encompass the adult life span in both sexes. The anaglyphs were viewed with red-green stereo glasses, using an image analyzer, and trabecular thickness and trabecular length were measured. From biomechanical principles, the strength of individual trabeculae can be estimated from measurement of trabecular rod thickness and trabecular rod length as the load to buckling index. The distribution of the load to buckling index was best described by a log normal curve. Trabecular rod thickness, trabecular rod length, and load to buckling index for males were consistently greater than for females. With aging, trabecular rod thickness, and the load to buckling index decrease for males while trabecular rod length increases for females. In this study, the load to buckling index for thoraco-lumbar vertebral trabecular rods potentially quantifies a greater risk of vertebral fracture for females. Decreased trabecular rod thickness or increased trabecular rod length result in the strength of trabeculae shifting closer to a putative fracture threshold. The corollary being that there is a reduced safety margin for resistance to mechanical loads for the vertebral bodies. The 3D anaglyph technique for measuring trabecular dimensions provides an accurate and precise methodology by which these morphological studies can be undertaken.