Changes in the sagittal spinal alignment of the elderly without vertebral fractures: a minimum 10-year longitudinal study.

Background: Thoracic hyperkyphosis, or loss of lumbar lordosis, is often equated with osteoporosis because vertebral fractures are assumed to be a major causative factor. However, recent evidence suggests that up to one-half of the patients with hyperkyphosis have no evidence of underlying vertebral fracture. The shape characteristics of the intervertebral discs and their role in determining kyphotic curvature have been investigated. The spinal sagittal parameters and segmental disc angles of elderly subjects were examined during a longitudinal follow-up.

Methods: A total of 53 subjects (20 men, 33 women) without vertebral fractures during a more than 10-year follow-up were included in this study, undergoing standing lateral radiographs of the spine using 36-inch film at baseline and final follow-up. The mean age of the subjects was 63 years (range 50-77 years) at baseline and 75 years (range 62-88 years) at follow-up; and the mean follow-up period was 11 years 11 months.

Results: The lumbar lordosis and the sacral inclination angle decreased and the C7-plumbline distance increased with age. Among a total of 664 discs, 70 discs (10.5%) showed anterior wedging over 5 degrees at follow-up. In contrast, 39 discs (5.9%) showed posterior wedging over 5 degrees . The subjects had only discs with anterior wedging, decreased total lumbar lordosis, and the C7 plumbline displaced anteriorly. However, when the subjects had discs with posterior wedging, the C7 plumbline and sagittal spinal balance tended to be maintained. This compensatory mechanism was seen in younger subjects.

Conclusions: A decrease in the total lumbar lordosis and the sacral inclination angle occurred with age. Increasing age correlated with a more forward sagittal vertical axis, depending on a decrease in the total lumbar lordosis. The cause of loss of lumbar lordosis in the subjects without vertebral fracture was anterior wedging of the segmental discs. Posterior wedging of the thoracic and lumbar segmental discs then could occur, compensating for the loss of lumbar lordosis.