Quantitative assessment of cervical disc degeneration using disc signal intensity index

The assessment of disc degeneration remains a significant challenge in clinical research. Pfirrmann grade is a frequently used classification for lumbar disc degeneration on MRI. However, there has been no gold standard for cervical spine disc degeneration. Recently, we introduced the Disc Signal Intensity Index (DSI2) as a quantitative disc assessment for the lumbar spine, which is easily measurable in the cervical spine.

The aim of this study was to apply DSI2 in the cervical intervertebral disc and investigate the factors associated with the cervical disc degeneration.

Cross-sectional study using retrospectively collected data.

Cervical MRIs from a database of patients undergoing ACDF between 2015 and 2018 were retrospectively reviewed.

Demographic variables included age, sex, body mass index (BMI), race, smoking status, and comorbidities such as diabetes, chronic kidney disease, and coronary artery disease.

DSI2 measurements were performed on midsagittal T2-weighted MRI images by determining the intensity within regions of interest (ROI). One ROI was set in the cerebrospinal fluid (CSF) and three ROIs were set per disc at the anterior, middle, and posterior third. The mean of the three measurements per disc was then divided by that of the CSF to calculate the DSI2 score. Multivariable linear regression analyses with mixed model were conducted to determine the potential contributing factors for disc degeneration.

A total of 149 patients and 770 discs were included in the final analysis. Ninety-three patients (37.6%) were female and the mean (SD) age was 55.6 (11.7) years. The distribution of DSI2 scores among the different Pfirrmann grades was as follows: Grade 1: 0.259±NA; Grade 2: 0.226±0.090; Grade 3: 0.175±0.070; Grade 4: 0.136±0.060; Grade 5: 0.131±0.050. Multivariable linear mixed-effect regression analysis, setting with DSI2 as the objective variable, demonstrated that age (β=-0.130, p<.05), BMI (β=-2.06, p<.05), Modic changes (Type1 β= -2.70, p<.01) were independent contributors to disc degeneration. The segments C4/5 and C7/T1 were less prone to disc degeneration (C4/5: β=1.37, p<.001; C7/T1: β=2.63, p<.001) and the history of diabetes (β=5.31, p<.01) was associated with high DSI2.(p<.01).

The present study provides valuable insights for identifying risk factors in degenerative cervical conditions utilizing the DSI2. The DSI2 method emerges as a promising alternative for future disc research, excelling in the detection of subtle progressions of degeneration and distinguishing itself from the subjective Pfirrmann grading system.