Comparison of antero-posterior and lateral measurements of the vertebral mineral contents by dual-energy x-ray absorptiometry
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Bone mineral measurements of the 2nd and 3rd vertebrae were made using dual energy x-ray absorptiometry (DEXA) in both antero-posterior (AP) and lateral (Lat) projections in 49 women (Group I; 24 young controls, II; 11 elderly controls, III; 14 osteoporotics). The coefficients of variation of the AP and Lat measurements of BMC in 3 young women were 2.2% and 8.4% of the respective mean values. In Group I, BMCs obtained by the Lat measurement were 11.6±15.7% below BMCAP (p<0.05). In Group II and III, on the other hands, BMCLat was as low as below 34.2±11.9% (Group II) and 40.1±21.5% (Group III) of respective AP contents (p<0.01). This discrepancy between BM CLat and BMCAP in Group II and III could not be acounted by the measurement error of Lat determination alone. Furthermore, the difference of bone mineral density (BMD) between Group I and II (or III) appeared to be much more pronounced when compared by the data obtained from the Lat measurements than the comparison using BMDAP. Extra-skeltal calcification projected on the AP plane, including calcified aorta and ligaments, may attribute such a difference between AP and Lat measurements. Our observation indicated the possibility of an overestimation of BMC and BMD by the AP determination of the spine. Therfore, an improvement of the reproducibility to measure the spine by the Lat determination with DEXA is mandatory for the detection of subclinical osteoporosis.
Key WordsDual-energy X-ray absorptiometry Bone mineral content Antero-posterior measurement Lateral measurement
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