Quantitative Disk and Metabolic Bone PET-MRI for Understanding Disk-Endplate Crosstalk in Degeneration of the Lumbar Spine.

OBJECTIVES

The aim of this investigation was to explore the association between disk degeneration, quantified by Pfirrmann grades and T1rho as a marker of hydration, and bone remodeling in the vertebral endplate quantified by Na[18F]F uptake on PET.

METHODS

Subjects for this exploratory, post hoc analysis were selected from a prospective observational study on low back pain. Subjects received simultaneous Na[18F]F-PET and spinal MRI (including T1rho mapping) in a hybrid scanner system. Tracer uptake (SUVmax) was quantified per endplate, and quantitative disk metrics were measured for annulus fibrosus and nucleus pulposus separately. Disk degeneration (Pfirrman grade) and endplate lesions (Modic changes) were assessed by a radiologist. Linear mixed models were used to investigate the association between quantitative disk and metabolic endplate metrics, adjusting for age, sex, body mass index, as well as Pfirrmann grade and Modic changes.

RESULTS

Eighty-six endplates from 9 patients (6 women) with median age 58 years (IQR: 53-72) were included. We found a positive association between annular T1rho and endplate Na[18F]F uptake (β = 0.088; 95% CI 0.018-0.159). The association was amplified by the presence of Modic changes (interaction p = 0.001).

CONCLUSION

Our findings indicate that bone remodeling of vertebral endplates is not associated with disk dehydration, and thus more likely a result of biological disk-endplate crosstalk than a sign of increased mechanical load.