Abstract: BACKGROUND: Previous studies have reported that anterior cervical hybrid surgery (Hybrid surgery) combined with partial artificial discs and fusion prostheses can obtain satisfactory early and mid-term clinical results, but for different prostheses, its application and clinical efficacy are still unclear.  
OBJECTIVE: To compare the clinical and radiological outcomes of treating two-level cervical spondylosis using Mobi-C combined with ROI-C in a hybrid surgery with anterior cervical discectomy and fusion and ROI-C alone.
METHODS:  Ninety-one patients with contiguous two-level cervical degenerative disc diseases, who were treated at Third Department of Orthopedics, Dongzhimen Hospital from March 2015 to May 2016 and received at least 4 years of effective follow-up, were included in this study. Among them, 48 cases underwent anterior cervical hybrid surgery as hybrid group; and 43 cases underwent anterior cervical discectomy and fusion as anterior cervical discectomy and fusion group. The following indicators were compared between the two groups. Clinical outcomes included visual analogue scales score for neck and upper limb pain, modified Japanese orthopaedic association, Neck disability index, patient satisfaction at preoperatively, 2 weeks postoperatively and the last follow-up. Radiological outcomes included C2-C7 range of motion, Mobi-C index level range of motion, range of motion at superior adjacent level, range of motion at inferior adjacent level, curvature of the operated levels, subsidence rate and fusion rate at ROI-C index levels preoperatively, 1 month postoperatively and the last follow-up.  
RESULTS AND CONCLUSION: (1) Clinical outcomes: At the last follow-up, scores of the two groups were significantly improved compared with preoperatively (P < 0.05), but the differences between groups were not significant (P > 0.05). (2) Radiological outcomes: At the last follow-up, the C2-C7 global range of motion in the hybrid group was significantly larger than that in the anterior cervical discectomy and fusion group [(40.84±15.19)° vs. (30.78±12.10)°, P < 0.05]. The curvature of the operated levels in both groups was improved significantly after surgery (P < 0.05), but there was no significant difference between the two groups (P > 0.05). There was no significant difference in range of motion of adjacent segments between the two groups (P > 0.05). The subsidence rates of ROI-C fusion were 26.09% and 36.00% in the hybrid group and anterior cervical discectomy and fusion group, respectively; and no significant difference was found between the two groups (P > 0.05). (3) It is indicated that Mobi-C combined with ROI-C is a safe and effective method for the treatment of contiguous double-level cervical spondylosis. It is not inferior to that of anterior cervical discectomy and fusion in the middle-stage clinical treatment, and it has certain advantages for retaining cervical movement. Bone resorption may be an integral component in the early stage of bony fusion in the ROI-C cage index level.

Key words: anterior cervical hybrid surgery, anterior cervical discectomy and fusion, Mobi-C artificial disc, ROI-C fusion cage, cervical spondylosis, double-level