Abstract: BACKGROUND: The impact of anterior cervical surgery on the sagittal balance parameters of the cervical spine is gradually being paid attention to. Currently, there is a lack of clear and feasible clinical guidelines for the selection of surgical methods for two-level cervical spondylosis, aiming to find the most suitable fixation method that is more beneficial for this type of patient.
OBJECTIVE: To compare the effects of different fusion devices for anterior cervical decompression on the changes of cervical sagittal parameters after surgery for adjacent two-level cervical spondylotic myelopathy. 
METHODS: A total of 44 patients with adjacent two-level cervical spondylotic myelopathy underwent anterior cervical discectomy and fusion from March 2018 to September 2020 in Liaocheng People’s Hospital were retrospectively analyzed in the study, and they were divided into zero-p group (23 cases) and cage group (21 cases). All patients underwent anteroposterior X-ray, three-dimensional CT reconstruction and MRI examination before operation. At the last follow-up, the anteroposterior X-ray films of cervical spine were taken. The sagittal balance parameters of the cervical spine were measured before and after surgery, including cervical lordotic angle (C2-7 Cobb), C2-C7 sagittal vertical axis, segmented lordotic angle and T1 slope. The surgical time, intraoperative bleeding, last follow-up intervertebral fusion, and postoperative swallowing disorders were recorded, and Japanese Orthopaedic Association score on the patient was evaluated before and after surgery. The changes in cervical sagittal parameters before and after surgery were calculated and their differences were compared between the two groups.
RESULTS AND CONCLUSION: (1) Both groups of patients successfully completed the surgery and received follow-up. The zero-p group had shorter surgical time and less intraoperative bleeding compared to the cage group, but the difference was not statistically significant (P > 0.05). (2) The incidence rate of postoperative swallowing disorders in the cage group (7/21, 33%) was higher than that in the zero-p group (3/23, 13%), and the difference was statistically significant (P < 0.05). (3) At the last follow-up, the clinical efficacy of the two groups was the same; all patients had bone fusion. Comparison within the group showed that the sagittal parameters of the cervical spine in both groups improved compared to before surgery (P < 0.05). There was no statistically significant difference in sagittal parameters between groups (P > 0.05), and there was no statistically significant difference in changes in C2-C7 sagittal vertical axis, C2-7 Cobb angle, and T1 slope between the two groups (P > 0.05). However, the segmented lordotic angle changes in the zero-p group were smaller than those in the cage group, and the difference was statistically significant (P < 0.05). (4) It is indicated that the use of zero-p and titanium plate combined with cage during anterior cervical discectomy and fusion surgery can effectively improve cervical sagittal balance. Titanium plate combined with cage intervertebral fusion can better reconstruct the patient’s cervical lordosis and curvature. The selection of fusion devices should also comprehensively consider the occurrence of surgical complications.

Key words: cervical spondylotic myelopathy, anterior cervical discectomy and fusion, interbody fusion, zero-p, titanium plate, cervical sagittal parameter