Reference data of vertebral morphometry by X-ray absorptiometry (MXA) in Argentine women

Anterior, middle, and posterior heights and A/P and M/P ratios were determi ned from T5 to L4 in 111 normal Caucasian Argentine women from 20 to 70 yea rs of age using dual energy X-ray absorptiometry (DXA) densitometry (Expert XL). Scanning time was less than 1 minute and the semiautomatic analysis r equires similar to 5 minutes. The precision error for the measurements rang ed from 2.2% to 4.6%. The absolute precision error for heights was 0.6 mm. The vertebral bodies tended to be significantly larger in younger women tha n older women, especially for anterior and middle heights and the A/P and M /P ratios of the midthoracic vertebrae (T6-T10). There were no significant differences between pre- and postmenopausal women in the lumbar vertebral h eights. It does not appear that this was a cohort effect because stature wa s identical in both age groups, and there was no age difference in posterio r height. The Expert-XL software normalized the vertebral height based on t he average height of the L2-L4 segment in order to minimize the influence o f interindividual variation of body size. The average Z-scores for vertebra l heights and ratios provided by the software were close to zero indicating that the normalization procedure appropriately corrected for smaller statu re in Argentine women. Consequently, the reference values for morphometry X -ray absorptiometry (MXA) were appropriate for our population. In summary, we found that (1) in "normal" women the anterior heights of the thoracic ve rtebrae (and therefore the A/P ratio) were higher in premenopausal than in postmenopausal women; and (2) the normalization approach corrected for diff erences of vertebral height and allowed utilization of the manufacturers so ftware in our population.