Relationship between cervical curvature and spinal cord drift distance after laminectomy via lateral mass screw fixation and its effect on clinical efficacy

Background: Laminectomy with lateral mass screw fixation (LCS) is considered an effective surgical procedure for cervical spondylotic myelopathy. However, varying degrees of loss of the cervical curvature were noted in some patients postoperatively. The aim of this study was to observe the relationship between cervical curvature and spinal drift distance after LCS and to determine its effect on neurological function, axial symptoms, and C5 palsy. Methods: A total of 117 consecutive cervical spondylotic myelopathy patients with normal cervical curvature underwent LCS from April 2015 to May 2017 in our institution. Of these patients, 90 patients who accepted to undergo an integrated follow-up were enrolled in this study. The patients were divided into 3 groups based on their postoperative cervical curvature. In group A (28 patients), the cervical curvature became straight postoperatively (0 degrees <= cervical spine angle <= 5 degrees); in group B (36 patients), the cervical curvature decreased (5 degrees<cervical spine angle <= 16.5 degrees); and in group C (26 patients), the cervical curvature remained normal (cervical spine angle>16.5 degrees). Spinal drift distance, neurological recovery, axial symptoms, and C5 palsy in the patients were recorded and analyzed. Results: Postoperative measurements showed that there was no significant difference in laminectomy width between the groups (P > .05). The cervical spine angle was 2.7 degrees +/- 0.5 degrees in group A, 11.2 degrees +/- 2.6 degrees in group B, and 20.8 degrees +/- 4.1 degrees in group C (P < .05), while the spinal drift distance was 1.2 +/- 0.2 mm, 1.8 +/- 0.4 mm, and 3.0 +/- 0.5 mm, respectively (P < .05). The postoperative Japanese Orthopedic Association score was significantly increased in all groups (P < .05), and there was no significant difference between the groups at different time points (P > .05). However, significant differences were noted between the groups in axial symptoms (P < .05), which were analyzed via the visual analog scale score. The occurrence of C5 palsy in groups A, B, and C was 7.1% (2/28), 8.3% (3/36), and 11.5% (3/26), respectively (P > .05). Conclusion: In LCS, the cervical curvature should be maintained at the normal angle to obtain a good spinal cord drift distance and a lower incidence of axial symptoms.