title: Computed tomography assessment of the accuracy of in vivo placement of artificial discs in the lumbar spine including radiographic and clinical consequences.
abstract: METHODS
  Prospective cohort study of 52 patients who had undergone artificial lumbar disc replacement.
  
  
  OBJECTIVE
  To evaluate the implantation accuracy of prosthesis positioning, subsequent facet joint changes and prosthesis migration, and the clinical consequences of implant position.
  
  
  BACKGROUND
  Accuracy of spinal prosthesis implantation has not been evaluated rigorously, especially with a mini-incision approach. It is unknown if the inexact placement of a mobile device in the spine has any biomechanical, radiographic, or clinical repercussions.
  
  
  METHODS
  A total of 52 consecutive patients were treated using standard methods of disc implantation with an intervertebral prosthesis. Computed tomography scans were performed within 3 days and again at 6 to 24 months. An independent radiologist analyzed the images for prosthesis position, rotation, migration, and facet changes. Results were compared with clinical outcome, measured by the Visual Analog Scale and Oswestry Disability Index.
  
  
  RESULTS
  Deviation of the prosthesis from the center position was under 1.2 mm, and rotation off of midline was under 12 degrees. Follow-up CT scans showed no migration or facet changes. Regression analysis showed no correlation of prosthesis position with clinical outcome.
  
  
  CONCLUSIONS
  Current prosthetic disc implantation methods, with minimally invasive access techniques, are relatively accurate. Although there can be deviation of the prosthesis from ideal placement, no repercussions were attributable.
authors.affiliation: Spine Institute at St. John's Hospital, Santa Monica, CA, USA.
authors.forename: Vikas V
authors.initials: VV
authors.lastname: Patel
authors.forename: Carol
authors.initials: C
authors.lastname: Andrews
authors.forename: Ben B
authors.initials: BB
authors.lastname: Pradhan
authors.forename: Hyun W
authors.initials: HW
authors.lastname: Bae
authors.forename: Linda E A
authors.initials: LE
authors.lastname: Kanim
authors.forename: Michael A
authors.initials: MA
authors.lastname: Kropf
authors.forename: Rick B
authors.initials: RB
authors.lastname: Delamarter
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005500:Follow-Up Studies; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000601:surgery; D007405:Intervertebral Disc Displacement / Q000000981:diagnostic imaging* / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery*; D011446:Prospective Studies; D019919:Prosthesis Implantation / Q000295:instrumentation* / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods*