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.