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Magnetic Resonance Classification System of Cervical Intervertebral Disk Degeneration: Its Validity and Meaning
Akinobu Suzuki1, Michael D Daubs, Tetsuo Hayashi
1*Department of Orthopaedic Surgery, University of California at Los Angeles, Los Angeles, CA †Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka, Japan.
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 κ-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.
Insights
This study introduces a new MRI-based grading system for cervical disk degeneration, demonstrating high reliability and validity. The system tracks the chronological order of degeneration, correlating with age and functional changes.
Area of Science:
- Radiology and Imaging
- Spine Degenerative Diseases
- Biomedical Engineering
Background:
- Cervical disk degeneration assessment via MRI lacks standardized, reliable grading systems.
- Existing methods suffer from subjectivity and unclear algorithms, hindering consistent evaluation.
Purpose of the Study:
- To develop and validate a novel, objective grading system for cervical disk degeneration using kinetic MRI (kMRI).
- To establish the reliability and clinical validity of the new grading system.
Main Methods:
- Retrospective analysis of kMRIs from 300 cervical intervertebral disks.
- Development of a 4-grade (0-III) classification system based on nucleus color, structure, disk bulge, and height.
- Assessment of intraobserver and interobserver reliability, followed by validation using 2802 disks to correlate with age and function.
Main Results:
- A distinct chronological order of MRI-detectable degeneration was identified: nucleus intensity changes, nucleus-annulus distinction loss, disk bulge, and height reduction.
- The developed grading system demonstrated high intraobserver (κ=0.96) and interobserver (κ=0.90) reliability.
- Degeneration severity correlated with patient age (R=0.467) and significantly impacted spinal motion and space available for the cord.
Conclusions:
- A new, reliable, and valid MRI-based grading system for cervical disk degeneration has been successfully developed.
- The system provides an objective and reproducible method for assessing degeneration, offering clinical significance.
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