Cortical and trabecular bone mineral mass in the radius and ulna

Sites in the distal radius used in the absorptiometric method of bone mineral mass measurement are often assumed to be predominantly trabecular bone. In order to determine the proportion of trabecular and cortical bone at these sites, we ashed and weighed the cortical and trabecular bone from 2-mm thick sections spaced approximately 2.5 mm apart in the most distal 12 cm of radii and ulnae from four women aged 21, 43, 63, and 85 years. The proportion of trabecular bone was found to change rapidly as a function of position in the bone metaphyses, but remained relatively constant as a function of age. In the diaphyses, the proportion of trabecular bone remained relatively constant as a function of position but increased with age. Contrary to the assumption that distal measurement sites are predominantly trabecular bone, we found that trabecular bone varied between 10 percent and 50 percent of the total, depending on the exact location of the site