Morphological changes of lumbar vertebral bodies and intervertebral discs associated with decrease in bone mineral density of the spine: a cross-sectional study in elderly subjects.

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

To investigate changes in the morphology of the lumbar vertebrae and intervertebral discs associated with osteoporosis of the spine in elderly subjects.

SUMMARY OF BACKGROUND DATA

Osteoporosis is a common condition that primarily affects the elderly with significant impact on quality of life. How exactly osteopenia and osteoporosis influence vertebral and intervertebral disc morphology remains unknown and needs exploration.

METHODS

A total of 395 community-dwelling ambulatory adults from 67 to 89 years of age were studied. The lumbar bone mineral density (BMD) was measured by dual-energy x-ray absorptiometry. T2-weighted sagittal images of the lumbar spine were obtained using a 1.5-T magnet. For each subject, the anterior height (Ha), middle height (Hm), posterior height (Hp), and anterior-posterior (AP) dimension of the 5 lumbar vertebrae (L1-L5) and 6 intervertebral discs (T12-L1 to L5-S1) were measured. To minimize the age effect, volume of these vertebrae and discs was measured in subgroups of 47 men (mean age = 74 yr, range: 73-75 yr) and 67 women (mean age = 72 yr, range: 71-73 yr). Continuous variables were examined by analysis of covariance after adjustment of height and age.

RESULTS

There was no significant age difference between the groups of normal BMD, osteopenia, and osteoporosis. For the vertebral bodies, lower BMD was associated with a decrease of Ha, Hm, and Hp but not AP in both sexes, leading to an increased biconcavity index. For the discs, lower BMD was associated with a decrease of Ha and Hp, as well as AP, and an increase in Hm in both men and women. The disc biconvexity index was increased. Lower BMD is associated with an overall decrease in both vertebral volume and disc volume.

CONCLUSION

Lower BMD is associated with a decreasing trend in both lumbar vertebral and disc volumes in elderly subjects but an increase in the Hm of the intervertebral discs.