MRI-based grading systems for assessing lumbar disc degeneration: a scoping review

Background Context: An array of different MRI (magnetic resonance imaging) based grading systems is used to measure disc degeneration (DD) in the lumbar spine. It is currently unclear which grading systems are most commonly used to assess lumbar DD and how these grading systems are applied and reported. 

Purpose: The aim of this scoping review was to describe different MRI-based grading systems for DD in the lumbar spine and report which grading systems have been assessed for measurement properties such as reliability, validity, and sensitivity to change. 

Study Design/Setting: Scoping review. 

Methods: A search was conducted in EMBASE, Medline, and CINAHL for studies related to MRI-based grading systems for DD in the lumbar spine, conducted in living humans. Data were extracted from each study, including the description of the grading system, which levels of the lumbar spine were graded, who graded the degeneration, how the degeneration was scored for analysis, and whether measurement properties such as reliability, validity, and sensitivity to change were assessed. 

Results: The search identified 569 studies that graded DD. Ninety-three different grading systems were identified, including 63 subjective systems, 25 quantitative systems, and 5 that were unspecified. The Pfirrmann method was used in over 50% of all reports. A range of grading components was used to measure DD, with disc signal intensity (DSI), disc height (DH), and the assessment of the distinctiveness between the annulus and nucleus being most common. Sensitivity to change was rarely assessed. 

Conclusion: A large number of DD grading systems were identified in this review, many of which were infrequently used. Variability in methods of assessing DD on MRI and how the MRI data is synthesized may influence reported associations between DD and low back pain (LBP).