GENDER DIFFERENCES IN VERTEBRAL SIZES IN ADULTS - BIOMECHANICAL IMPLICATIONS

PURPOSE: To determine if vertebral bone densities or vertebral body sizes contribute to gender differences in vertebral bone mass in adults. MATERLALS AND METHODS: 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. RESULTS: Neither cancellous nor cortical vertebral bone densities differed in healthy adults. Vertebral bodies in women had lower cross-sectional areas (8.22 cm(2) +/- 1.09 [standard deviation] versus 10.98 cm(2) +/- 1.25, P <.001) and volumes (22.42 cm(3) +/- 2.40 versus 30.86 cm(3) +/- 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. CONCLUSION: Smaller vertebral bodies in women confer biomechanical disadvantages that may contribute to more vertebral fractures in elderly women.