Correlation of radiographic and MRI parameters to morphometrical and biochemical assessment of intervertebral disc degeneration

Degenerative disc disease (DDD) is a common finding in MRI scans and X-rays. However, their correlation to morphological and biochemical changes is not well established. In this study, radiological and MRI parameters of DDD were assessed and compared with morphological and biochemical findings of disc degeneration. Thirty-nine human lumbar discs (L1–S1), age 19–86 years, were harvested from eight cadavers. Within 48 h postmortem, MRIs in various spin-echo sequences and biplanar radiographs of intact spines were obtained. Individual discs with endplates were then sectioned in the mid-sagittal plane and graded according to the morphological appearance. Samples from the nucleus of each disc were harvested for biochemical analysis including water and proteoglycan contents. On MRIs, T2-signal intensity, Modic changes, disc extension beyond the interspace (DEBIT), nucleus pulposus shape, annular tears, osteophytes and endplate integrity were graded. On radiographs, an independent observer classified the parameters disc height, endplate sclerosis, osteophytes, Schmorls nodes, intradiscal calcifications and endplate shape. General linear-regression models were used for statistical analysis. Backward elimination with a 10% significance cut-off level was used to identify the most significant parameters, which then were summed to create composite scores for radiography, MRI and the combination of both methods. The grading was performed by three observers, and a reliability analysis using Cronbachs alpha model was used to control interobserver agreement. The three radiographic parameters height-loss, osteophytes and intradiscal calcifications correlated significantly with the morphological degree of degeneration (p