title: Radiologic landmark accuracy for optimum coronal placement of total disc arthroplasty in the lumbar spine.
abstract: OBJECTIVE
  This study was performed to determine which of the radiographic markers visible on an anteroposterior (AP) radiograph of the spine-the vertebral body, the pedicles, and the spinous process-provided the most accurate guide to correctly placing an intervertebral disc replacement in the coronal midline.
  
  
  METHODS
  The coronal midline was defined as the perpendicular bisector of a line drawn between the midpoints of the two facet joints. Axial CT images were reconstructed from 35 abdominal and renal computed tomograms to compare how consistently the midpoints of the above structures fell on the coronal midline.
  
  
  RESULTS
  The mean distance (SD) from the vertebral body midpoint, the interpedicular midpoint, and the spinous process midpoint from the coronal midline, respectively, were 0.55 mm (SD 0.45 mm), 0.19 mm (SD 0.40 mm), and 1.30 mm (SD 1.30 mm). Sixteen percent of the distances from the coronal midline to the spinous process midpoint were greater than or equal to 3 mm compared with 0% of the distances to the interpedicular midpoint or the vertebral body midpoint.
  
  
  CONCLUSIONS
  We concluded that the interpedicular midpoint is the most accurate guide to the coronal midline. We recommend that this landmark be used in preference to the spinous processes or the midpoint of the vertebral bodies when placing the implant in intervertebral disc arthroplasty.
authors.affiliation: Department of Orthopaedic Surgery, Auckland Hospital, Auckland, New Zealand.
authors.forename: Dinshaw N
authors.initials: DN
authors.lastname: Mistry
authors.forename: Peter A
authors.initials: PA
authors.lastname: Robertson
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D007405:Intervertebral Disc Displacement / Q000000981:diagnostic imaging* / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019919:Prosthesis Implantation / Q000379:methods*; D011785:Quality Assurance, Health Care / Q000379:methods; D011856:Radiographic Image Enhancement / Q000379:methods*; D011877:Radionuclide Imaging; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome