title: The Clinical and Radiological Effect of Abnormal Axis after Cervical Arthroplasty.
abstract: OBJECTIVE
  The clinical outcomes according to the radiological results after cervical total disc replacement (TDR) are not well established. Here, the authors reviewed the clinical results according to the asymmetry in radiographs.
  
  
  METHODS
  This retrospective analysis included patients after TDR (Mobi-C® disc) with at least 12 months follow up, and the clinical and radiological data were obtained preoperatively and postoperatively for 12 months. Clinical outcome measures numerical rating scale (NRS) score for neck pain, visual analog scale (VAS) for arm pain, and the Oswestry disability index (ODI) value. The asymmetries of TDRs were evaluated on the anterior-posterior (AP) and the lateral radiographs, and the radiographic adjacent segment degenerations were evaluated for 12 months.
  
  
  RESULTS
  A total of 24 patients (one level cervical TDR; 10 male and 14 female; aged 41.50±8.35 years) were included in this study. The clinical results including NRS for neck pain, VAS for arm pain, and ODIs were similar between the normal and asymmetrized TDRs in AP and lateral radiographs. The radiographic adjacent segment degenerations were significantly increased in deviated TDRs (AP>10 mm asymmetry and lateral>10 mm asymmetry).
  
  
  CONCLUSIONS
  Asymmetrical location of TDR is not related to the clinical outcomes, but related to the risk of radiographic adjacent disc segment degeneration.
authors.affiliation: Department of Neurosurgery, Inha University College of Medicine, Incheon, Korea.
authors.forename: Hyun Jun
authors.initials: HJ
authors.lastname: Jang
authors.affiliation: Department of Neurosurgery, Teun Teun Research Institute, Seoul, Korea.
authors.forename: Chang Hyun
authors.initials: CH
authors.lastname: Oh
authors.affiliation: Department of Neurosurgery, Inha University College of Medicine, Incheon, Korea.
authors.forename: Seung Hwan
authors.initials: SH
authors.lastname: Yoon
authors.affiliation: Department of Neurosurgery, Inha University College of Medicine, Incheon, Korea.
authors.forename: Ji Yong
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, Inha University College of Medicine, Incheon, Korea.
authors.forename: Hyeong Chun
authors.initials: HC
authors.lastname: Park
authors.affiliation: Mechanical Engineering, Kyung Hee University, Seoul, Korea.
authors.forename: Yoon Hyuk
authors.initials: YH
authors.lastname: Kim
keywords: Cervical arthroplasty; Fusion; Malposition; Mobi-c; Total disc replacement