title: Biomechanical analysis of anterior versus posterior instrumentation following a thoracolumbar corpectomy: Laboratory investigation.
abstract: OBJECTIVE
  The objective of this study was to evaluate the biomechanical properties of lateral instrumentation compared with short- and long-segment pedicle screw constructs following an L-1 corpectomy and reconstruction with an expandable cage.
  
  
  METHODS
  Eight human cadaveric T10-L4 spines underwent an L-1 corpectomy followed by placement of an expandable cage. The spines then underwent placement of lateral instrumentation consisting of 4 monoaxial screws and 2 rods with 2 cross-connectors, short-segment pedicle screw fixation involving 1 level above and below the corpectomy, and long-segment pedicle screw fixation (2 levels above and below). The order of instrumentation was randomized in the 8 specimens. Testing was conducted for each fixation technique. The spines were tested with a pure moment of 6 Nm in all 6 degrees of freedom (flexion, extension, right and left lateral bending, and right and left axial rotation).
  
  
  RESULTS
  In flexion, extension, and left/right lateral bending, posterior long-segment instrumentation had significantly less motion compared with the intact state. Additionally, posterior long-segment instrumentation was significantly more rigid than short-segment and lateral instrumentation in flexion, extension, and left/right lateral bending. In axial rotation, the posterior long-segment construct as well as lateral instrumentation were not significantly more rigid than the intact state. The posterior long-segment construct was the most rigid in all 6 degrees of freedom.
  
  
  CONCLUSIONS
  In the setting of highly unstable fractures requiring anterior reconstruction, and involving all 3 columns, long-segment posterior pedicle screw constructs are the most rigid.
authors.affiliation: Departments of 1 Neurosurgery.
authors.forename: Stephanus V
authors.initials: SV
authors.lastname: Viljoen
authors.forename: Nicole A
authors.initials: NA
authors.lastname: DeVries Watson
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Grosland
authors.forename: James
authors.initials: J
authors.lastname: Torner
authors.forename: Brian
authors.initials: B
authors.lastname: Dalm
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Hitchon
mesh_terms: D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D012399:Rotation; D013123:Spinal Fusion / Q000295:instrumentation*; D013314:Stress, Mechanical; D013904:Thoracic Vertebrae / Q000601:surgery*
keywords: anterior instrumentation; biomechanics; posterior instrumentation; thoracic; thoracolumbar corpectomy