Dynamic cervical implant in treating cervical degenerative disc disease: a systematic review and meta-analysis

To systematically compare the safety and efficacy of dynamic cervical implant (DCI) with anterior cervical discectomy and fusion (ACDF) and cervical total disc replacement (CTDR) in treating cervical degenerative disc disease (CDDD). Electronic searches were conducted using PubMed, Embase, CBM, CNKI, VIP, and Wan Fang database (update to October 19, 2016). The relevant published literatures were screened by two independent reviewers according to the inclusion criteria. No language restriction was applied. Two prospective and four retrospective studies were enrolled with a total of 491 patients. No statistical difference was observed with regard to operative time, intraoperative blood loss and Japanese Orthopedic Association (JOA) score between DCI and ACDF group or DCI and CTDR group. No statistical difference was identified between DCI and ACDF group in Visual Analog Score (VAS) for neck and arm and between DCI and CTDR group in Neck Disability Index (NDI). Compared with ACDF group, DCI group presented higher treated segmental ROM, lower cephalad segmental ROM and caudal segmental ROM, but equal in overall range of motion (ROM). No significant difference in cephalad, treated and caudal segmental ROM was seen between DCI group and CTDR group. Based on our study, the limited evidence indicated that DCI is as effective and safe as ACDF and CTDR for patients with CDDD. DCI may maintain the ROM of treated segment and delay the occurrence of adjacent segment disease. However, insufficient evidence supports that DCI may decrease the stress of facet joints.