Morphometric dual-energy X-ray absorptiometry of the spine: Report of a large series and correlation with axial bone mineral density

We studied vertebral morphometry and its relation to bone mineral density (BMD) in normal Brazilian women (n = 605), All women (age 22-97 years) were ambulatory and healthy. A lateral spine scan was done for morphometric X-ray absorptiometry using an imaging densitometer, In 429 of these women, BMD of the spine and proximal femur also were measured using dual-energy X-ray absorptiometry, All women were white with mean (+/- 1 SD) age of 53.7 (+/- 9.5) years. About 21% of the women over 50 years had a T score for spine BMD lower than -2.5 SD, and 7% had a femoral neck BMD below this osteoporosis threshold. Vertebral heights (anterior, H-A; middle, H-M; and posterior, H-P) and ratios (H-A/H-P and H-M/H-P) were assessed. There was no systematic difference between younger (20-49 years) and older (50+ years) women in heights or ratios. The vertebral heights were normalized for those observed in each individual case for the L2-L4 sequence. This normalization was adequate for all vertebral heights; the Z score averaged about +0.1. The average Z score for H-A/H-P was +0.01, but that for the H-M/H-P was -0.72, indicating that the latter ratio might differ from the reference population used (white American and European women). We observed a small positive correlation between vertebral heights and spine or femur BMD, but this was due entirely to the influence of body size on BMD, On a group basis, the H-M/H-P, showed a significant association with axial BMD; the 1 SD difference between the lowest and highest quartile was associated with a difference of 8-15% (0.5-1.0 SD) in axial BMD.