Can Supine Magnetic Resonance Imaging Be an Alternative to Standing Lateral Radiographs for Evaluating Cervical Sagittal Alignment?

Abstract

Objective Recently, many studies have reported that cervical alignment is related to clinical outcomes. However, poor visibility of anatomical structures during X-ray (XR) imaging limits accurate measurements. In supine magnetic resonance (MR) imaging, the boundary of the anatomical structure is clear, but the correlation to XR images taken in a standing position is problematic. In this study, we evaluated the agreement of sagittal alignment parameters between MR and XR measurements. Methods We retrospectively reviewed 268 patients. Cervical sagittal parameters were measured using XR and MR images, and their relationships were evaluated using Pearson's correlation, paired t -tests, and 2-way random, single score intraclass correlation coefficient (ICCs) (2,1). Using simple linear regression analysis, MR results were converted to the expected value (MR-E). The subsequent comparison of MR-Es with XRs was used to examine whether MR-Es could replace XRs when the measurement difference was less than 2 mm or 2°. Results The correlation between the MR and XR measurements was high, but ICCs showed low reliability. All parameters were significantly different between XR and MR measurements in paired t -tests. Converting the MR values eliminated the t -test differences between MR-Es and XRs, but did not affect correlations and ICCs. The replacement ratio included the Cobb angle: 20.3%, T1: 27.1%, the sagittal vertical axis: 17.6%, C1–2: 29.7%, and C2: 16.0%. Conclusion These results indicate that supine MR measurements could not replace upright XR measurements.

Magnetic Resonance Imaging Is Inadequate to Assess Cervical Sagittal Alignment Parameters

“…Furthermore, a significant number of patients (50%) were excluded from our analysis because of poor visibility of the T1 superior endplate on lateral XR images; this is in line with similar studies and highlights a notable limitation of this imaging modality to fully assess cervical alignment. 11,12,14 Lastly, we attribute the differences of the cervical SVA and T1 tilt to the differences in imaging position-upright versus supine -however, there are several variables that are unaccounted for and may have influenced our findings. These include inconsistent head positioning, rotation, and differential observer experience with the imaging software.…”

“…[6][7][8] Efforts to address these shortcomings have been explored using the C7 vertebral body as a proxy for T1-based measurements, [8][9][10] as well as employing advanced imaging such as computed tomography and MRI to better visualize and quantify the parameters of interest. 2,[11][12][13][14] In this domain, findings and conclusions vary; some groups advocate for the utility of MRI as a surrogate for plain x-rays (XR), 11,13 while other groups determined that MRI measurements could not replace XR measurements. 2,12,14 In this context, we analyzed preoperative XR and MRI cervical sagittal parameters for patients undergoing posterior decompressive procedures for cervical spondylotic myelopathy.…”

Comparison of MRI and bolster hyperextension radiography in determining the flexibility of thoracic curves in Scheuermann kyphosis: a retrospective cross-sectional study

“…[15][16][17] However, a supine MRI has not always been suggested as an acceptable alternative to standing radiography. Bae et al 18 evaluated the agreement of the sagittal alignment parameters between MRI and standing radiographs in 268 patients. Although the correlation between MRI and radiography was high, the ICC demonstrated low reliability.…”

“…They concluded that supine MRI could not replace standing radiographic measurements. 18 It is acknowledged that the Cobb angle is different between the supine and standing positions because of the change of gravitational load on the spine. 19 This gravitational change is associated with almost 5 degrees of loss of the thoracic curve, 29 degrees of loss of the lumbar lordosis, and 20 degrees of loss of the sacral rotation after moving from a standing to a sitting position.…”

“…The replacement ratio was 20.3% for the Cobb angle, 27.1% for T1, 17.6% for the sagittal vertical axis, 29.7% for C1-2, and 16% for C2. They concluded that supine MRI could not replace standing radiographic measurements 18…”