Assessing Foraminal Stenosis in the Cervical Spine: A Comparison of Three-Dimensional Computed Tomographic Surface Reconstruction to Two-Dimensional Modalities

Abstract

Study Design:Retrospective radiographic study.Objective:The optimal radiographic modality for assessing cervical foraminal stenosis is unclear. Determination on conventional axial cuts is made difficult due in part to the complex, oblique orientation of the cervical neuroforamen. The utility of 3-dimensonal (3D) computed tomography (CT) reconstruction in improving neuroforaminal assessment is not well understood. The objective of this study is to determine inter-rater variability in grading cervical foraminal stenosis using 3 different CT imaging modalities: 3D CT surface reconstructions (3DSR), 2D sagittal oblique multiplanar reformations (2D-SOMPR), and conventional 2D axial CT imaging.Methods:Pretreatment CT scans of 25 patients undergoing surgery for cervical spondylotic radiculopathy were analyzed at 2 levels: C5-C6 and C6-C7. Simple interrater agreement and kappa-Fleiss coefficients were calculated for each imaging modality and stenosis grade. Image reviewers (attending spine surgeon, attending neuroradiologist, spine fellow) interpreted each CT scan in 3 different formats: axial, 2D-SOMPR, and 3DSR. Four cervical foramina at 2 spinal levels were graded as normal (no stenosis), mild (≤25% stenosis), moderate (25%-50% stenosis), or severe (>50% stenosis).Results:Across all imaging modalities, interrater reliability was fair when grading foraminal stenosis (κ < 0.4). Agreement was lowest for the axial images (κ = 0.119) and highest for the 3D CT reconstructions (κ = 0.334). 2D-SOMPR images also led to improved interrater reliability when compared with axial images (κ = 0.255).Conclusion:Grading cervical foraminal stenosis using conventional axial CT imaging is difficult with low interrater reliability. CT modalities that provide a circumferential view of the cervical foramen, such as 2D-SOMPR and 3D CT reconstruction, had higher rates of interobserver reliability in grading foraminal stenosis than conventional axial cuts, with 3D having the highest. As these 3D reconstructions can be obtained at no additional cost or radiation exposure over a conventional CT scan, and because they can provide useful information in determining levels being considered for surgical decompression, we recommend they be utilized when evaluating cervical foramina.

An anatomical study of the spinous process of the seventh cervical vertebrae based on the three‑dimensional computed tomography reconstruction

“…Only a few reports have assessed the inter-individual variation of C7-SP. In the present study, the anatomic characteristics of the C7-SP were preliminarily measured based on 3D computed tomography (CT) reconstruction, an imaging tool that has been validated in a variety of applications for the practice of spine surgery ( 14 ). The objective of the present study was to explore the anatomical features of C7-SP, which may facilitate the diagnosis and treatment of conditions involving the cervical spine.…”

Posterior endoscopic cervical foramiotomy and discectomy: clinical and radiological computer tomography evaluation on the bony effect of decompression with 2 years follow-up

“…Determination on conventional axial cuts were made difficult due in part to the complex, oblique orientation of the cervical neuroforamen. Using 3D CT reconstruction, we increased the reliability of measurement of foraminal stenosis as compared to conventional axial CT imaging [29].…”

Magnetic resonance imaging in the evaluation of cervical foraminal stenosis: comparison of 3D T2 SPACE with sagittal oblique 2D T2 TSE

“…Foraminal stenosis was graded on a 5-point scale as proposed by Park et al 3,4). Time needed to complete the grading was recorded (including the reformatting process for 3D T2w SPACE).…”

“…While standard examination planes-mostly sagittal and axial-allow for evaluation of both spinal canal contents and neural foramina in the lumbar spine, visualization of the cervical neural foramina and their contents is rendered more difficult by their oblique orientation, with angles of about 45° to the sagittal and 10-15° (inferiorly) to the axial plane [2]. This has led to the use of oblique projections for radiographic evaluation [3], oblique reconstructions of CT acquisitions [4], and oblique sagittal MRI sequences (mostly T2w) angled about 45° [2,[5][6][7] for a better, in-plane representation of the foramina. Oblique (or "angled") sagittal T2w sequences have been shown to be more accurate in the evaluation of the cervical neural foramina than "conventional" sagittal and axial sequences [2,[6][7][8], and their use may alter surgical recommendations [9].…”