Comparative Study of Two-Level Hybrid Surgery (Cervical Artificial Disc with Cage) with Two-Level Anterior Cervical Interbody Fusion for Multi-level Cervical Degenerative Disease

ABSTRACT

INTRODUCTION: Cervical anterior interbody fusion may be considered to be the gold standard for treatment of symptomatic cervical degenerative disc disease. However, this method leads to degenerative changes at the levels adjacent to the fused segments. On the other hand, multilevel cervical artificial disc replacement is another treatment for cervical degenerative disease, but the effectiveness and stability of artificial disc has not been proven yet. The purpose of this study is to compare the two-level hybrid surgery (Cervical disc prosthesis replacement at one level, and interbody fusion with cage at the other level) with the classical two-level interbody fusion in relation to the clinical outcomes and effects on the adjacent segment levels. METHOD: 27 patients with two-level cervical degenerative disease were enrolled and assigned to each study group. Radiologic analysis was used to measure the range of movement (ROM) of cervical spine, functional spinal unit (FSU) and adjacent segment levels at 2 months postoperatively and follow-up period (Mean follow-up period was 9.3(+/-4.1) month). Furthermore, clinical outcomes were analyzed by using visual analogue scale (VAS) and Odom..s criteria. RESULT: Out of 27 patients, 14 patients received hybrid surgery (group A) and 13 patients received two-level interbody fusion using a cage with bone graft (group B). Both groups showed significant improvement in symptoms and the VAS scores after operation (group A from 8.2 to 2.4, group B from 8.0 to 3.2). In group A, ROM of C2-7 decreased at 2 month postoperatively, but it was restored to nearly preoperative state during follow-up period. ROM of C2-7 in group B also showed similar changes, and there were no statistically significant difference between two groups (group A pre-operation 44.3degrees, 2 months after operation 29.0degrees and last follow-up 41.6degrees, group B pre-operation 46.8degrees, 2 months after operation 26.3degrees and last follow-up 37.4degrees). In both upper and lower segments, ROM of group B was significantly increased during follow-up period, compared with ROM of group A. This reflected that adjacent segments in group B received more stress due to bone fusion of functional spinal unit. CONCLUSION: The hybrid surgery was somewhat effective in two-level cervical degenerative disease. ROM analysis of adjacent segments in hybrid surgery group suggested that this group received less stress at adjacent segments, compared with two-level anterior cervical fusion group. Further follow-up study is required to assess long-term outcomes of the hybrid surgery and its influence on adjacent levels.