title: Hybrid surgery for multilevel cervical degenerative disc diseases: a systematic review of biomechanical and clinical evidence.
abstract: OBJECTIVE
  The optimal surgical technique for multilevel cervical degenerative disc diseases (DDD) remains controversial. Hybrid surgery (HS) incorporating anterior cervical discectomy and fusion (ACDF) and cervical disc replacement (CDR) is increasingly performed for cervical DDD. This study aims to evaluate the biomechanical and clinical evidence available for HS and to provide a systematic review of current understanding of HS.
  
  
  METHODS
  This systematic review was undertaken by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement. Multiple databases and online registers of clinical trials were searched up to February 2014. The biomechanical and clinical studies on HS for cervical DDD written in English were included. Two authors independently assessed methodological quality and extracted data.
  
  
  RESULTS
  Fifteen studies including eight biomechanical studies and seven clinical studies were indentified. The biomechanical studies showed that HS was benefit to motion preservation of the operative levels and revealed less adverse effect on adjacent segments. All clinical studies demonstrated improvement in validated functional scores after HS. Segment motion and immobilization were achieved at the arthroplasty level and arthrodesis level, respectively. Postoperative assessments and complication rate were similar or in favor of HS when comparing with ACDF or CDR. However, the overall quality of evidence for HS was low to very low.
  
  
  CONCLUSIONS
  There is a paucity of high quality evidence for HS. HS may be a safe and efficacious technique to benefit a select group of multilevel cervical DDD, which is needed to be confirmed by further prospective, randomized controlled trials.
authors.affiliation: Department of Orthopaedics, Navy General Hospital, Clinical School of Navy, Second Military Medical University, NO.6 Fucheng Road, Beijing, 100048, People's Republic of China.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Jia
authors.forename: Zhongjun
authors.initials: Z
authors.lastname: Mo
authors.forename: Fan
authors.initials: F
authors.lastname: Ding
authors.forename: Qing
authors.initials: Q
authors.lastname: He
authors.forename: Yubo
authors.initials: Y
authors.lastname: Fan
authors.forename: Dike
authors.initials: D
authors.lastname: Ruan
mesh_terms: D001178:Arthroplasty / Q000379:methods; D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae / Q000473:pathology* / Q000601:surgery*; D018849:Controlled Clinical Trials as Topic / Q000379:methods; D017586:Diskectomy / Q000379:methods; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000175:diagnosis* / Q000601:surgery*; D013122:Spinal Diseases / Q000175:diagnosis / Q000601:surgery; D013123:Spinal Fusion / Q000379:methods; D016896:Treatment Outcome