title: Early clinical and radiographical results of keel-less and shallow keel cervical disc replacement.
abstract: BACKGROUND
  Cervical disc replacements has been shown to be as effective as fusions in the treatment of radiculopathy or myelopathy due to disc prolapse. Newer implants were designed to reduce the difficulty of end-plate preparation. Since 2010, the authors have started using Discocerv (Alphatec Spine, Carlsbad, USA) a keel-less implant and Activ-C (B. Braun, Sheffield, UK), a shallow keel implant.
  
  
  OBJECTIVE
  The aim of this study was to compare the duration of surgery between cervical disc replacement and anterior cervical discectomy and fusion, and also to evaluate the functional outcome, complications, and radiographic outcome of cervical disc replacement.
  
  
  RESULTS
  Fifty patients were included (20 disc replacement and 30 fusion). This was a single surgeon retrospective study, with all surgery performed by the senior author (RT). The mean operation duration for single-level disc replacement was 2.6 h, and for single-level fusion was 2.4 h (P = 0.4684). For 2-levels surgery, the result was 3.5 h for 2-level hybrid surgery (one level disc replacement and one level fusion) and 3.4 h for fusion (P = 0.4489). Disc replacement resulted in preservation of an average of 67% of the angle of motion at the sagittal plane (FFflexion-extension). The average range of motion after disc replacement was 6.1°. The median clinical follow-up duration was 2 years (average 1.8 years). There was no incidence of major complications or significant neurovascular injury in this series of patients. A significant improvement in short form-36 scores was seen as early as 3 months postoperative (from 58 preoperative to 92 at 3 months). The improvement was sustained up to the fourth year of follow-up.
  
  
  CONCLUSIONS
  Cervical arthroplasty with keel-less and shallow keel implants are safe and relatively easy to perform. The surgical time for disc replacement is not significantly longer than standard fusion surgery. There is reasonably good preservation of motion. The short-term functional improvement is good, and we await further long-term outcome results. The authors felt that cervical disc replacement will have an important role in the treatment of cervical degenerative disc disease in the future.
authors.affiliation: Department of Neurosurgery, National Neuroscience Institute, 11 Jalan Tan Tock Seng, 308433 Singapore.
authors.forename: Ji Min
authors.initials: JM
authors.lastname: Ling
authors.affiliation: Department of Neurosurgery, National Neuroscience Institute, 11 Jalan Tan Tock Seng, 308433 Singapore ; Department of Neurosurgery, Singapore General Hospital, Academia, Level 5, 169865 Singapore ; Spine Neuro Specialist Centre, Gleneagles Medical Centre, 258499 Singapore.
authors.forename: Rajendra
authors.initials: R
authors.lastname: Tiruchelvarayan
keywords: Activ-C; Discocerv; cervical arthroplasty; cervical disc replacement; motion preservation