Evaluation of human cartilage endplate composition using MRI: spatial variation, association with adjacent disc degeneration, and in vivo repeatability.

Cartilage endplate (CEP) biochemical composition may influence disc degeneration and regeneration. However, evaluating CEP composition in patients remains a challenge. We used T2* mapping from ultrashort echo-time (UTE) MRI, which is sensitive to CEP hydration, to investigate spatial variations in CEP T2* values and to determine how CEP T2* values correlate with adjacent disc degeneration. Thirteen human cadavers (56.4±12.7 years) and seven volunteers (36.9±10.9 years) underwent 3T MRI, including UTE and T1ρ mapping sequences. Spatial mappings of T2* values in L4-S1 CEPs were generated from UTE images and compared between sub-regions. In the abutting discs, mean T1ρ values in the nucleus pulposus were compared between CEPs with high vs. low T2* values. To assess in vivo repeatability, precision errors in mean T2* values and intra-class correlation coefficients (ICC) were measured from repeat scans. Results showed that CEP T2* values were highest centrally and lowest posteriorly. In the youngest individuals (<50 years), who had mild-to-moderately degenerated Pfirrmann grade II-III discs, low CEP T2* values associated with severer disc degeneration: T1ρ values were 26.7% lower in subjects with low CEP T2* values (p=0.025). In older individuals, CEP T2* values did not associate with disc degeneration (p=0.39-0.62). Precision errors in T2* ranged from 1.7-2.6 ms, and reliability was good-to-excellent (ICC=0.89-0.94). These findings suggest that deficits in CEP composition, as indicated by low T2* values, associate with severer disc degeneration during the mild-to-moderate stages. Measuring CEP T2* values with UTE MRI may clarify the role of CEP composition in patients with mild-to-moderate disc degeneration. This article is protected by copyright. All rights reserved.