title: Quantitative dual-energy CT for phantomless evaluation of cancellous bone mineral density of the vertebral pedicle: correlation with pedicle screw pull-out strength.
abstract: OBJECTIVE
  To evaluate quantitative dual-energy computed tomography (DECT) for phantomless analysis of cancellous bone mineral density (BMD) of vertebral pedicles and to assess the correlation with pedicle screw pull-out strength.
  
  
  METHODS
  Twenty-nine thoracic and lumbar vertebrae from cadaver specimens were examined with DECT. Using dedicated post-processing software, a pedicle screw vector was mapped (R1, intrapedicular segment of the pedicle vector; R2, intermediate segment; R3, intracorporal segment; global, all segments) and BMD was calculated. To invasively evaluate pedicle stability, pedicle screws were drilled through both pedicles and left pedicle screw pull-out strength was measured. Resulting values were correlated using the paired t test and Pearson's linear correlation.
  
  
  RESULTS
  Average pedicle screw vector BMD (R1, 0.232 g/cm(3); R2, 0.166 g/cm(3); R3, 0.173 g/cm(3); global, 0.236 g/cm(3)) showed significant differences between R1-R2 (P < 0.002) and R1-R3 (P < 0.034) segments while comparison of R2-R3 did not reach significance (P > 0.668). Average screw pull-out strength (639.2 N) showed a far stronger correlation with R1 (r = 0.80; P < 0.0001) than global BMD (r = 0.42; P = 0.025), R2 (r = 0.37; P = 0.048) and R3 (r = -0.33; P = 0.078) segments.
  
  
  CONCLUSIONS
  Quantitative DECT allows for phantomless BMD assessment of the vertebral pedicle. BMD of the intrapedicular segment shows a significantly stronger correlation with pedicle screw pull-out strength than other segments.
  
  
  CONCLUSIONS
  • Quantitative dual-energy CT enables evaluation of pedicle bone mineral density. • Intrapedicular segments show significant differences regarding bone mineral density. • Pedicle screw pull-out strength correlated strongest with R1 values. • Dual-energy CT may improve preoperative assessment before transpedicular screw fixation.
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany, docwichmann@gmail.com.
authors.forename: Julian L
authors.initials: JL
authors.lastname: Wichmann
authors.forename: Christian
authors.initials: C
authors.lastname: Booz
authors.forename: Stefan
authors.initials: S
authors.lastname: Wesarg
authors.forename: Ralf W
authors.initials: RW
authors.lastname: Bauer
authors.forename: J Matthias
authors.initials: JM
authors.lastname: Kerl
authors.forename: Sebastian
authors.initials: S
authors.lastname: Fischer
authors.forename: Thomas
authors.initials: T
authors.lastname: Lehnert
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Vogl
authors.forename: M Fawad
authors.initials: MF
authors.lastname: Khan
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Kafchitsas
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000368:Aged; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology*; D002102:Cadaver; D016022:Case-Control Studies; D020878:Device Removal; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D065289:Pedicle Screws; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology*; D014057:Tomography, X-Ray Computed / Q000379:methods