Influence of dynamic neck motion on the clinical usefulness of multi-positional MRI in cervical degenerative spondylosis

Purpose: The purpose of this study was to find out additional indications for multi-positional MRI in cervical degenerative spondylosis (CDS) patients. Material and methods: A total of 63 patients with cervical spondylotic myelopathy that underwent multi-positional MRI and X-ray were included. Muhle’s grade, C2-7 angle, and C7 slope were measured. Patients were assigned to the stenosis group (Group S) when Muhle’s grades were increased by more than two or maximum grade was reached. Other patients were assigned to the maintenance group (Group M). Receiver operating characteristic (ROC) analysis was performed. Statistical significance was accepted for p values of < 0.05. Results: A total of 24 patients were assigned to the S group and 39 patients to the M group. Mean C2-7 angle difference in extension (eC27A) between S and M groups was 10.97° (p = 0.002). The mean inter-group difference between C2-7 angle in extension and neutral positions (e-nC27A) was 14.39° (p = 0.000). Mean C7 slope difference in neutral position was − 6.53° (p = 0.002). Based on areas under ROC curves (AUCs), e-nC27A, eC27A, and negative C7 slope had AUCs of 0.934 (95% CI 0.876–0.992), 0.752 (95% CI 0.624–0.880), and 0.720 (95% CI 0.588–0.851), respectively. The optimal cutoff value of e-nC27A was 15.4 degrees, which had a diagnostic accuracy of 88.9%. Conclusion: Multi-positional MRI helps to find dynamic cord compressive lesion in CDS patients. The higher eC27A, e-nC27A values and smaller C7 slope were found to increase the likelihood of cervical dynamic stenosis. Among other factors, we recommend multi-positional MRI before surgery especially when a patient’s e-nC27A is > 15.4 degrees. Level of evidence I: Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.