The intervertebral disc, the endplates and the vertebral bone marrow as a unit in the process of degeneration

Abstract

OBJECTIVES The association of disc degeneration (DD) and vertebral endplate degeneration (EPD) is still not well understood. This study aimed to find segmental predictive risk factors for DD and EPD and to illuminate associations of the disc, endplate and bone marrow changes in the process of degeneration. METHODS After institutional review board approval, 450 lumbar levels, followed up with MRI for at least 4 years, were retrospectively graded for DD according to Pfirrmann (PFG), for EPD according to the endplate score (EPS) and according to the presence, extension and type of Modic changes (MC). Clustered logistic regression and multivariate analysis was applied in nested, matched case-control subgroups to evaluate potential local risk factors for progression. RESULTS An EPS score of  ≥4 was identified as an independent risk factor for progression of DD (OR = 2.32, 95%CI:1.07-5.01,p = 0.03) and MC (OR = 5.49,95%CI:2.30-13.10,p < 0.001). Progression of DD was significantly accompanied by progression or evolution of MC (OR = 12.25,95%CI:1.49-100.6,p = 0.02) and with progression of EPS (OR = 1.71, 95%CI:1.00-1.05, p = 0.01). Once advanced DD has occurred, it becomes a risk factor for progression in EPS (OR = 2.24,95%CI:1.23-4.12,p < 0.01). CONCLUSIONS The degenerative processes in the disc, endplate and bone marrow are highly associated. An EPS ≥ 4 is an independent risk factor for DD and MC progression in a population with low back pain. KEY POINTS • The degenerative processes in the disc, endplate and bone marrow are associated. • An endplate score ≥4 is a risk factor for DD and MC progression. • Modic changes are last to occur in the development of segmental intervertebral degeneration. • A new segmental grading system is suggested.