title: Quantitative prediction of spinal cord drift after cervical laminectomy and arthrodesis.
abstract: METHODS
  Retrospective review of radiographic parameters.
  
  
  OBJECTIVE
  To identify preoperative radiographic parameters that may be quantitatively predictive of postoperative spinal cord drift after cervical laminectomy and arthrodesis.
  
  
  BACKGROUND
  Cervical laminectomy and arthrodesis can be an effective method to treat anterior compressions of the spinal cord if there is a sufficient posterior spinal cord drift after surgery. Preoperative cervical alignment has shown some correlations to the degree of spinal cord shift, but whether this and other preoperative radiographic parameters can be used to quantitatively predict the amount of spinal cord drift is unclear.
  
  
  METHODS
  Preoperative and postoperative radiographs (radiographs, MRIs, and CT) of patients who had cervical laminectomy and arthrodesis were reviewed retrospectively. Various radiographic parameters, including sagittal alignment, longitudinal distance index, space available for the spinal cord at cephalad or caudad levels, and distance from apex of the lordosis to the C2-C7 vertical line were measured. In the first cohort of patients, these parameters were correlated with mean postoperative spinal cord shift to identify any relationships. In the second cohort of patients, the identified association was used on preoperative imaging studies to attempt quantitative prediction of the postoperative spinal cord shift.
  
  
  RESULTS
  Space available for the spinal cord at the level immediately cephalad to the laminectomized segments had high correlations (R = 0.94) to the postoperative spinal cord shift. This association was used to quantitatively predict postoperative spinal cord shift within 11% +/- 6% of the measured value. If 4 mm of mean postoperative spinal cord shift is desired, the ratio to the available space and anterior posterior diameter of the spinal cord should be approximately 2.0.
  
  
  CONCLUSIONS
  Relative stenosis at the level directly cephalad to the laminectomized level can affect the degree of postoperative spinal cord shift. Preoperative axial imaging studies should be closely scrutinized to ensure that adequate space is available at the cephalad adjacent level to allow sufficient cord shift after decompressive laminectomy and arthrodesis.
authors.affiliation: University of Pittsburgh Medical Center, Pittsburgh, PA, USA. joonyunglee@hotmail.com
authors.forename: Joon Y
authors.initials: JY
authors.lastname: Lee
authors.forename: Ashwini
authors.initials: A
authors.lastname: Sharan
authors.forename: Eli M
authors.initials: EM
authors.lastname: Baron
authors.forename: Moe R
authors.initials: MR
authors.lastname: Lim
authors.forename: Eric
authors.initials: E
authors.lastname: Grossman
authors.forename: Todd J
authors.initials: TJ
authors.lastname: Albert
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Vaccaro
authors.forename: Alan S
authors.initials: AS
authors.lastname: Hilibrand
mesh_terms: D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery*; D015331:Cohort Studies; D019299:Decompression, Surgical; D006801:Humans; D007796:Laminectomy; D008279:Magnetic Resonance Imaging; D009192:Myelography; D011184:Postoperative Period; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013116:Spinal Cord / Q000000981:diagnostic imaging* / Q000473:pathology*; D013123:Spinal Fusion; D014057:Tomography, X-Ray Computed