Aging changes in lumbar discs and vertebrae and their interaction: a 15-year follow-up study

Background context: Many studies have focused on either the intervertebral disc as a culprit in back pain problems, or the vertebral body, but very few studies have examined both structures and their relationship.

Purpose: To measure the concordant changes in morphology of the discs and vertebrae during 5-, 10-, and 15-year follow-ups.

Study design: Longitudinal study.

Patient sample: Among a general population sample of 232 men that had been scanned in 1992-1993, 105 men were reexamined in 1997-1998 and 2007-2008. Mean age at the 15-year follow-up was 63 years. A confirmatory sample with 10 years follow-up was also included.

Methods: Scanners (1.5 Tesla) with surface coils were used at baseline and follow-up. Image analyzing software was used to measure distances and areas of interest of midsagittal and midaxial spine images.

Results: The disc heights decreased at 5 years by 3.4% (0.4 mm) and 3.3% (0.4 mm) and at 15 years by 8.7% (1.0 mm) and 11.3% (1.3 mm) in the upper and lower discs, respectively (p<.001). Although not clear after 5 years, vertebra heights increased in mean by 3.1% (0.8 mm) in the upper lumbar levels and by 4.7% (1.1 mm) in the lower vertebrae after 15 years (p<.001). Vertebra height increases were associated with disc narrowing (p=.001). The mean annual shortening of the lumbar spine L1-S1 block was 0.13 mm/y, which was in line with the mean standing height that decreased little (174.7 cm at baseline and 174.4 cm at the follow-up).

Conclusions: Discs and vertebrae degenerate or remodel in concert: decreases in disc height appear to be compensated, in part, by accompanying increases in adjacent vertebra heights. The mechanism behind this novel finding and its implications require further study.