[Appropriateness and limitations of bone mineral measurements by DXA (dual energy x-ray absorptiometry) in the elderly--comparison with x-ray findings]

Abstract

A group of 674 (266 males and 410 females) elderly living in a rural community of Nangai Village, Akita Prefecture, were subjects of bone mineral measurements in the lumbar spine and three areas of proximal femur (femoral neck; FN, trochanter; TR and Ward's triangle; WD). Measurement was by dual energy x-ray absorptiometry (DXA) set in a mobile van during mass health examination. The purpose of this study was to verify the appropriateness and imitations in the bone mineral measurements by DXA in elderly who have other aging related abnormal calcifications such as osteophytosis in the lumbar spine and calcification of the abdominal aorta, all of which may have an influence on the 'true' value of bone mineral density (BMD) particularly in the lumbar region. The results were as follows: 1) Subjects who were not capable of being measured by DXA tended to be older and reported experiencing pain and who scored low in TMIG index of competence compared to measurable subjects. 2) BMD of 2nd-4th lumbar spine with antero-posterior projection (AP) did not show simple age-declines that are seen in younger generations. In contrast, BMDs of proximal femur show linear aging declines. 3) Analysis of the association between BMDs and osteophytosis by spondylosis deformans in the lumbar spine and calcification of the abdominal aorta in front of the lumbar spine showed that AP-BMD had a strong correlation with the grade of both spinal osteophytosis and aortic calcification. On the other hand, BMDs of proximal femur showed no significant associations with these abnormal calcifications. 4) In this context, in order to evaluate the 'true' BMD in the elderly, BMDs in the proximal femur are a more appropriate indicator than AP-BMD which may be easily contaminated by other aging-related calcification in and around the lumbar region.