title: Cervical spine alignment in disc arthroplasty: should we change our perspective?
abstract: OBJECTIVE
  The alignment at the cervical spine has been considered a determinant of degeneration at the adjacent disc, but this issue in cervical disc replacement surgery is poorly explored and discussed in this patient population. The aim of this systematic review is to compare anterior cervical fusion and total disc replacement (TDR) in terms of preservation of the overall cervical alignment and complications.
  
  
  METHODS
  A systematic review of the current literature was performed, together with the evaluation of the methodological quality of all the retrieved studies.
  
  
  RESULTS
  In most of the retrieved studies, a tendency towards a more postoperative kyphotic alignment in TDR was reported. The reported mean complication rate was of 12.5 % (0-66.2 %). Complications associated with cervical prosthesis included heterotopic ossification, device migration, mechanical instability, failure, implant removal, reoperations and revision.
  
  
  CONCLUSIONS
  Even though cervical disc arthroplasty leads to similar outcomes compared to arthrodesis in the middle term follow-up, no evidence of superiority of cervical TDR is available up to date. We understand that the overall cervical alignment after TDR tends towards the loss of lordosis, but only longer follow-up can determine its influence on the clinical results.
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Campus Bio-Medico of Rome, Rome, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Di Martino
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Campus Bio-Medico of Rome, Rome, Italy.
authors.forename: Rocco
authors.initials: R
authors.lastname: Papalia
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Campus Bio-Medico of Rome, Rome, Italy.
authors.forename: Erika
authors.initials: E
authors.lastname: Albo
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Campus Bio-Medico of Rome, Rome, Italy.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Cortesi
authors.affiliation: Academic Neurosurgery, Department of Neuroscience, University of Padova, Padua, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Denaro
authors.affiliation: Department of Orthopaedics and Trauma Surgery, University Campus Bio-Medico of Rome, Rome, Italy. denaro@unicampus.it.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Denaro
mesh_terms: D002574:Cervical Vertebrae / Q000601:surgery*; D017586:Diskectomy; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000601:surgery*; D011183:Postoperative Complications; D013121:Spinal Curvatures / Q000209:etiology*; D013123:Spinal Fusion; D059145:Total Disc Replacement; D016896:Treatment Outcome
keywords: Cervical spine; Cervical spine arthroplasty; Sagittal alignment; Total disc replacement