Comparison of Radiography with Computed Tomography and Magnetic Resonance Imaging in the Measurement of Cervical Lordosis

Background and Objectives: The assessment of cervical lordosis is essential for surgical planning and outcome prediction in patients with cervical spine pathology. This study aims to evaluate the accuracy of cervical lordosis measurements obtained on supine CT and MRI relative to standing lateral radiographs. Materials and Methods: In this retrospective review, 108 patients who underwent standing lateral radiographs, supine CT, and MRI within a 30-day period were identified. C2–C7 Cobb angles were measured on each modality. Using upright radiographs as the reference standard, the predictive capability of both supine CT and supine MRI in classifying kyphotic versus non-kyphotic alignment was calculated. Results: Standing radiographs demonstrated significantly greater lordosis than supine imaging, with mean paired differences of 6.2° versus CT and 5.0° versus MRI (both p < 0.001); however, strong correlations were observed (with CT: r = 0.75; with MRI: r = 0.72; both p < 0.001). Further, CT-based measurements predicted X-ray Cobb angles with an R2 value of 0.57 (estimated X-ray Cobb angle = 8.24 + 0.74 × (CT Cobb angle), β = 0.74, p < 0.001). MRI-based measurements yielded an R2 of 0.51 (estimated X-ray Cobb angle = 7.59 + 0.71 × (MRI Cobb angle), β = 0.71, p < 0.001). At threshold ≥ 0°, CT achieved a 100% NPV for excluding kyphosis on upright radiographs. MRI achieved an NPV of 100% when the Cobb angle was >1.20°. Conclusions: Supine CT and MRI systematically underestimate cervical lordosis but demonstrate strong predictive correlation with standing radiographs and reliably exclude true kyphotic alignment, with each achieving near-perfect NPV at defined thresholds. In cases where standing radiographs are unavailable or nondiagnostic, supine imaging modalities such as CT and/or MRI, where the cervical region appears nonkyphotic, can safely rule out cervical kyphosis and inform surgical planning; however, in cases where the cervical region appears kyphotic on CT and/or MRI, standing radiographs remain essential for accurate assessment.