Comparison of Cervical Sagittal Parameters Between Radiographs and Magnetic Resonance Images in Patients With Cervical Spondylotic Myelopathy

STUDY DESIGN: Observational study OBJECTIVE: As an important consideration of surgery, cervical sagittal balance is believed to be better assessed using standing radiograph than supine magnetic resonance imaging (MRI). However, few studies have researched this. Our study aimed to observe the correlations and differences in cervical sagittal parameters between radiograph and MRI in patients with cervical spondylotic myelopathy (CSM), and evaluate whether the change of position affects them. METHODS: We analyzed 84 patients, measuring Cobb angle (CA), T1 slope (T1S), neck tilt (NT), and thoracic inlet angle (TIA). Inter- and intra-parameter analyses were performed to identify any difference between standing radiograph and supine MRI. Statistical correlations and differences between the parameters were compared. RESULTS: There were excellent inter-observer agreement for each parameter (interclass correlation coefficient >.75), and significant differences were observed in each parameter between radiograph and magnetic resonance imaging (P < .05). Strong correlations were noted between the same parameters in radiograph and MRI. Cobb angle, T1S, and neck tilt were significantly correlated with thoracic inlet angle on both radiograph and MRI, and CA was significantly correlated with T1S on both radiograph and MRI (r: −1.0 to −.5 or .5 to 1.0). CONCLUSION: Supine MRI obviously underestimated the value of CA, T1S, and TIA. Therefore, standing cervical radiographs should be obtained in CSM patients to assess and determine surgical strategy, not only supine MRI. Moreover, we observed that NT and TIA were not constant morphological parameters.