2004 Young investigator award winner : vertebral endplate marrow contact channel occlusions and intervertebral disc degeneration

Study Design. Intervertebral disc degeneration was evaluated by morphologic appearance, magnetic resonance imaging, and by biochemical matrix composition. Caliber and distribution of openings of the adjacent vertebral osseous endplates were measured. Objectives. Correlation between occlusion of vertebral endplate openings and intervertebral disc degeneration was quantified. Summary of Background Data. Calcifications of vertebral endplates with disease and age have suggested insufficient nutrition as a mechanism for intervertebral disc degeneration. It has been proposed that occlusion of endplate openings, which contain vascular sources for the disc, may limit the transport of nutrients, leading to disc degeneration. Methods. Fresh magnetic resonance images from 39 human lumbar discs were scored. Sectioned discs with endplates were morphologically graded. Samples of nuclear and anular regions were evaluated for proteoglycan and collagen contents. Backlight microscopic images of 4 endplate regions were obtained, and caliber and distribution of endplate openings for each disc were measured. Analysis of variance regression models were used to assess correlation between endplate openings and disc degeneration. Results. The decrease in opening density significantly correlated to morphologic degeneration grade, best for openings with 20 to 50 ìm equivalent diameter and in the nuclear region. Although the density of 20 to 50 ìm openings also significantly indirectly correlated to age, it was not as strong as the correlation to degeneration grade. Opening density was also significantly correlated to proteoglycan content in all regions. However, all other biochemical parameters as well as the T2 intensity score showed only weak or no correlation to opening density. Conclusions. A high indirect correlation between the density of openings in the osseous endplate (particularly of the size of the capillary buds) and the morphologicdegeneration grade of the disc support the hypothesis that occlusion of these openings may deprive the cells of nutrients, leading to insufficient maintenance of the extracellular matrix and disc degeneration