Gender differences in vertebral sizes in adults: biomechanical implications.

Abstract

To determine if vertebral bone densities or vertebral body sizes contribute to gender differences in vertebral bone mass in adults. Cancellous and cortical bone densities and dimensions of three lumbar vertebrae in 25 women and 18 men were measured with quantitative computed tomography (CT) and statistically analyzed. Neither cancellous nor cortical vertebral bone densities differed in healthy adults. Vertebral bodies in women had lower cross-sectional areas (8.22 cm2 +/- 1.09 [standard deviation] versus 10.98 cm2 +/- 1.25, P < .001) and volumes (22.42 cm3 +/- 2.40 versus 30.86 cm3 +/- 2.6, P < .001). These differences also were evident in men and women matched for age, weight, vertebral bone density, and vertebral body height. Overall cross-sectional areas of vertebral bodies are 25% smaller in women than men. Vertebral bone densities do not differ between sexes. Estimates of mechanical stress within vertebral bodies are 30%-40% higher in women than men for equivalent applied loads. Smaller vertebral bodies in women confer biomechanical disadvantages that may contribute to more vertebral fractures in elderly women.