The role of three-dimensional trabecular microstructure in the pathogenesis of vertebral compression fractures.

We compared indices of three-dimensional microstructure of iliac trabecular bone between 26 patients with vertebral compression fractures due to postmenopausal osteoporosis and 24 control subjects without vertebral fracture, who were matched for age, sex, race, menopausal status, and several densitometric and histologic indices of both cortical and trabecular bone mass. The patients with fracture had a significantly lower mean value (1.03 +/- 0.15 vs. 1.26 +/- 0.26; P less than 0.005) for indirectly calculated mean trabecular plate density, an index of the number and connectivity of structural elements, and as a necessary corollary, a significantly higher mean value for the mean thickness of structural elements. Plate density was more than one standard deviation below the age-adjusted mean value for normal postmenopausal white females in 19 (73%) of the fracture cases and in only 5 (21%) of the nonfracture cases (P less than 0.001). We conclude that the biomechanical competence of trabecular bone is dependent not only on the absolute amount of bone present but also on the trabecular microstructure.