Predictability of severity of disc degeneration and disc protrusion using horizontal displacement of cervical dynamic radiographs: A retrospective comparison study with MRI

The aim of this study is to investigate the usefulness of flexion-extension (dynamic) radiographs in evaluating the severity of disc degeneration and disc protrusion in cervical magnetic resonance image (MRI). Patients complaining of neck or arm pain with no prior surgical history and who had undergone both cervical MRI and dynamic radiographs were included in this study. The following patients were excluded: those who had any history of trauma, autoimmune disease such as rheumatoid arthritis or ankylosing spondylitis, prior cervical fracture or prior cervical spine surgery. Based on these criteria, 161 patients who visited our department for neck pain or upper extremity radicular symptoms were initially included retrospectively. Among them, 69 patients were excluded due to the lack of cervical MRI or dynamic radiographs. Therefore, a total of 92 patients were included for analysis in this study. The maximal diameter of disc protrusion in sagittal or axial MRI, the severity of cervical disc degeneration, and segmental horizontal displacement in dynamic cervical radiographs are the main outcome measurements. In the results of this study, the extension radiograph of C5/6 had the highest sensitivity (93.33%) and specificity (100%) in predicting cervical disc protrusion followed by C4/5 (sensitivity; 77.28%, specificity 92.86%) among the dynamic radiographs. Segmental horizontal displacement at the C3/4, C4/5, and C5/6 level in the neutral and extension radiographs had a significant correlation with the severity of cervical disc degeneration in MRI (P < .05). At the C6/7 level, however, only extension radiograph had a significant correlation with the severity of cervical disc degeneration in the MRI (P < .05). In conclusion, if MRI is not available in a primary clinical setting, dynamic cervical radiographs may be useful in predicting the severity of degenerative disc and disc protrusion in cervical MRI. Among the dynamic cervical radiographs, the extension radiograph was the most sensitive for predicting the severity of cervical disc degeneration and disc protrusion, especially at the C3/4, C4/5, C5/6, and C6/7 levels in MRI.