Association between intervertebral disc degeneration and endplate perfusion studied by DCE-MRI.

PURPOSE: The goal of this study was to study the association between solute transport mechanisms in cartilaginous disc endplates and the degeneration of intervertebral discs. Intervertebral disc degeneration is a multi-factorial process. It is suspected that poor nutrient delivery to discs might be a factor leading to degeneration. Several studies suggest that defects in disc endplates could lead to poor transport of nutrients. An imaging technique assessing endplate perfusion could be a valuable tool in investigating disc degeneration. There is currently no universally accepted technique assessing endplate perfusion in vivo. METHODS: Nine adult patients exhibiting varying levels of intervertebral disc degeneration were included. MRI was used to study the association between blood perfusion in 90 lumbar disc endplates and disc degeneration in 45 lumbar discs. Solute transport mechanism through endplates was assessed indirectly by dynamic contrast enhanced (DCE) MRI. T2-weighted MRI was used for conventional Pfirrmann classification. RESULTS: A positive association was observed between Pfirrmann grades and endplate DCE-MRI enhancement. A differential enhancement between cranial and caudal endplates was also observed, which increased with Pfirrmann grades. This differential enhancement was also dependent on the lumbar level. CONCLUSIONS: Increased MRI signal enhancement in the cartilaginous endplates of degenerated discs might indicate damage to the subchondral bone of the vertebral bodies. The endplate enhancement characteristic could aid in understanding the pathophysiology of disc degeneration and planning treatment more effectively.

Intervertebral disc height loss demonstrates the threshold of major pathological changes during degeneration.

PURPOSE: Quantitative MRI techniques were utilized to study intervertebral disc degeneration. Main focus was to develop a novel approach to quantify disc height loss associated with disc degeneration. Currently there is no universally accepted metric of degeneration based on measurement of disc height. Such quantitative imaging methods would complement qualitative visual assessment methods currently used and offer a valuable diagnostic tool. METHODS: 51 adult participants took part in this MRI study. T2 weighted images were used to obtain disc height index (DHI) and also a semi-quantitative metric based on relative voxel intensities. For DHI, each disc was given a score based on standard deviations from the mean DHI of healthy discs. Diffusion Weighted MRI was used to assess morphological changes in the nucleus pulposus. Conventional Pfirrmann classification was used as the gold standard to assess these quantitative approaches. RESULTS: At deviations of up to 1.5σ below normative disc height, levels of apparent diffusion coefficient (ADC) and normalized T2 intensity were maintained. Once disc compression reached 1.5σ, there was a massive drop in ADC and normalized T2 intensity. Pfirrmann degeneration scores also increased after the 1.5σ mark. CONCLUSIONS: This study provides new, unbiased quantitative imaging tools to assess disc degeneration. We observed that these quantitative MRI measures indicate a threshold beyond which major pathological changes take place concurrently. Combined information from DHI, ADC and T2 images construct a set of novel biomarkers that could be used to identify degenerating discs that are approaching the threshold and possibly intervene before major pathologic changes occur.