• Tetsuo Hayashi, Jeffrey C Wang, Akinobu Suzuki, Shinji Takahashi, Trevor P Scott, Kevin Phan, Elizabeth L Lord, Monchai Ruangchainikom, Keiichiro Shiba, and Michael D Daubs.
• *Department of Orthopaedic Surgery, University of California at Los Angeles; and †Department of Orthopaedic Surgery, Japan Labour Health and Welfare Organization, Spinal Injuries Center, Fukuoka, Japan.
• Spine. 2014 May 1;39(10):812-9.

Study DesignRetrospective analysis of kinematic magnetic resonance (MR) images.ObjectiveTo elucidate the distribution and risk factors associated with missed dynamic stenosis in cervical spine.Summary Of Background DataMotion of the cervical spine is widely accepted to be associated with cervical spondylotic myelopathy; however, the distribution and the risk factors for dynamic spinal stenosis are not well understood.MethodsA total of 435 symptomatic patients (2610 cervical segments) obtained upright kinematic MR images in neutral, flexion, and extension postures. Spinal cord compression (SCC), spondylolisthesis, disc bulging, angular motion, translational motion, disc degeneration grade, Modic changes, segmental alignment, and developmental stenosis were all evaluated. Cervical segments C2-C3 to C7-T1 were divided into 2 groups, determined by the presence of SCC. After excluding segments with SCC in the neutral position, a multivariate logistic regression model was used to evaluate for associated risk factors of SCC in flexion and extension that were not present in the neutral position.ResultsSCC in neutral position was observed in 5.3% (139/2610) of segments. After excluding these segments, missed dynamic stenosis was found in 8.3% (204/2471) of segments in extension and 1.6% (40/2471) in flexion. Missed dynamic stenosis in both extension and flexion was most frequent at C5-C6. Multivariate logistic regression analysis for dynamic stenosis in extension revealed that disc bulge greater than 2.4 mm, angular motion greater than 4.8°, moderate and severe disc degeneration, segmental kyphosis, and developmental stenosis were significant risk factors. In flexion, significant risk factors were a disc bulge of 1.9 mm or greater, moderate to severe disc degeneration, and segmental kyphosis.ConclusionDynamic cord compression was most common at the C5-C6 segment. Cervical segments with greater disc bulge, more severe disc degeneration, greater angular motion, segmental kyphosis, and developmental stenosis may be at risk for missed dynamic stenosis.

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