The relationship between height, shape and histological changes in early degeneration of the lower lumbar discs.

The influence of aging and early degenerative changes on intervertebral disc height is controversial. It has been claimed that with aging, narrowing of the disc is inevitable, but this is not confirmed by some published radiological investigations. The present study analysed the height and shape of intervertebral discs from subjects younger than 40 years, and correlated the findings with histological alterations, which were assessed using a grading system. Discs from the L4/5 level (n = 13) and the L5/S1 level (n = 10) were included. Degenerative changes tended to increase with age, specifically at the L4/5 level. There was a weak trend towards decreased disc height with increasing degenerative changes, but no significant correlation could be found. Disc shape was more convex in the frontal than the sagittal plane. It is concluded that early histological changes do not significantly influence intervertebral disc height. More pronounced loss of disc height may be seen in advanced degenerative changes or in elderly subjects.