Progression of lumbar disc degeneration: A 14-year follow-up study examining Pfirrmann grading and its individual disc components.

Abstract

Background: Lumbar disc degeneration (LDD) is frequently evaluated using the Pfirrmann classification. While this composite grading system provides an overview of degeneration severity, it may oversimplify LDD by overlooking variability in individual disc components, reducing its effectiveness in longitudinal studies and constraining its applicability in artificial intelligence-based image analysis.

Purpose: To examine the 14-year progression of LDD using the Pfirrmann classification and its individual components, and to evaluate the potential of component-based analysis.

Material and methods: LDD was assessed using MRI in 19 males (95 discs) at ages 37 and 51 by two radiologists. Evaluations included Pfirrmann grading, quantitative nucleus pulposus (NP) signal intensity, and visual grading of NP inhomogeneity, annulus fibrosus (AF) border distinction, and disc height (DH). Analyses included longitudinal changes in LDD variables and correlations between Pfirrmann grading and disc components. To assess overall LDD, a summary score was calculated by summing individual disc grades.

Results: Pfirrmann grading correlated strongly with AF border distinction, moderately with NP signal intensity, and weakly with NP inhomogeneity and DH. Pfirrmann summary score (range 5-25) increased by 3 points over time. Variability was observed in the progression of individual disc component degeneration. While mean NP signal intensity significantly decreased, some discs exhibited increase.

Conclusion: This longitudinal study highlights complexity of LDD and variability in disc component changes. While Pfirrmann classification captures overall degeneration, its limitations in detecting subtle variations in disc components suggest a need for more detailed assessments to enhance diagnostic precision and support the development of automated analysis tools.