Magnetic Resonance Classification System of Cervical Intervertebral Disk Degeneration Its Validity and Meaning

Study Design: Retrospective analysis of kinetic magnetic resonance images (kMRIs). Objective: (1) To analyze the changes seen on MRI related to disk degeneration and to develop a new grading system for cervical disk degeneration. (2) To evaluate the reliability and validity of the grading system. Summary of Background Data: Few have studied the relationship between changes seen on MRI with cervical disk degeneration and the chronological order of disk degeneration. A few grading systems for cervical disk degeneration have been reported; however, there have been problems related to subjectivity and lack of a clear, reliable algorithm. Methods: A total of 300 cervical intervertebral disks were graded for nucleus color, structure, disk bulge, and disk height. On the basis of the analysis, a new grading system consisting of 4 grades (grade 0-III) and algorithm were developed. Intraobserver and interobserver reliabilities were assessed. A total of 2802 intervertebral disks were then evaluated using the grading system to correlate disk degeneration grades with patient age and function and to evaluate the validity of the new system. Results: On the basis of cross-table analysis, disk degeneration presents in the following order: (1) decrease and/or change of nucleus intensity; (2) loss of distinction between nucleus and annulus; (3) positive disk bulge; and (4) disk height decrease. The k-coefficients for intraobserver and interobserver agreements were 0.96 and 0.90, respectively. Severe disk degeneration is most common at C5/C6 followed by C6/C7 and C4/C5, and total disk degeneration grade is correlated with age (R= 0.467). There was a decrease of angular motion in grades I-III and an increase in translational motion and decrease of space available for the cord in grades II-III. Conclusions: We developed a new classification system of cervical disk degeneration based on analysis of the changes seen on MRI. Reliability tests indicated high reproducibility of this system, and further analysis confirmed its validity and clinical significance.