Compact and trabecular components of the spine using quantitative computed tomography.

A computer algorithm was employed to quantify separately cortical and trabecular bone mineral density (BMD) from single energy computed tomography (CT) scans of 139 vertebrae (L1-L3) of 50 normal female subjects. In addition, the trabecular-to-integral and cortical-to-integral mass ratios were determined using digital image segmentation techniques. They showed that for the central 8-mm vertebral slice, the mass of integral bone consists of about one-fifth trabecular and four-fifth cortical bone. The trabecular-to-integral volume ratios were 0.37 +/- 0.08 and 0.63 +/- 0.08, respectively. Based on cross-sectional data from this subject group, the average annual loss was -2.21 +/- 0.15 mg/cm3 or -1.84 +/- 0.12% for trabecular bone, -3.15 +/- 0.25 mg/cm3 or -1.01 +/- 0.08% for cortical bone, and -2.60 +/- 0.20 mg/cm3 or -1.09 +/- 0.09% for the integral bone. The proportions of the age-related loss of BMD from the integral bone which originated from trabecular and cortical bone were 29.5 and 70.5%, respectively.