The proportion of trabecular bone in human vertebrae

The proportion of trabecular bone in human cadaver vertebrae was assessed by anatomic dissection. Thirty-two whole thoracic and lumbar vertebrae were obtained from 10 normal human postmenopausal female cadavers, 14 from 4 normal adult human male cadavers of similar age, and 8 from one female osteoporotic cadaver. Each vertebra was opened by saw cuts and separated into four tissue types: (1) body trabecular bone and marrow; (2) body cortical bone; (3) vertebral arch trabecular bone and marrow; and (4) vertebral arch cortical bone. Calcium was determined in each tissue type for each vertebra by ashing and atomic absorption spectrophotometry. Trabeculae accounted for 24.4 +/- 4.5% of the total calcium in whole female vertebrae, and 18.8 +/- 4.4% in whole male vertebrae (p less than 0.001). The body averaged 41.8% trabecular bone in females and 33.5% in males. The arch averaged 9.7% trabecular bone in females and 4.9% in males. The proportion of trabecular bone in the whole vertebrae in the single osteoporotic spine was 28.5 +/- 3.2%, a value not significantly different from the trabecular fraction in normal females. These data indicate that whole human thoraco-lumbar vertebrae are composed of a substantially lower proportion of trabecular bone than is usually assumed, and they suggest that cortical and trabecular bone are eventually lost in equal proportion from the vertebrae during the development of spinal osteoporosis. These results are important for the interpretation of data from noninvasive bone measurement techniques that evaluate the spine, and they suggest that studies of this type are important for any site where noninvasive bone mass measurement is done.