title: Sacral fixation technique in lumbosacral fusion.
abstract: METHODS
  Servohydraulic load displacement testing was used to study the biomechanical properties of sacral fixation in human cadaveric specimens.
  
  
  OBJECTIVE
  To evaluate a modification of standard sacral fixation that uses the first dorsal sacral foramina as an adjunct location for the placement of a sacral hook in addition to S1 pedicle screws.
  
  
  BACKGROUND
  The stiffness or rigidity of an instrumentation construct governs the amount of relative movement allowed between motion segments undergoing fusion. This property provides the greatest influence over the mechanical conditions necessary for fusion to occur.
  
  
  METHODS
  Sixteen human cadaveric specimens were divided into two groups with similar bone density assessed by quantitative computed tomography scan. All were instrumented with pedicle screws at L4 and S1. One group also had downgoing offset hooks in the first sacral foramina distracted against the S1 pedicle screw. Instron servohydraulic testing was performed in anterior compressive flexion, and load displacement curves were recorded.
  
  
  RESULTS
  The bending stiffness of the specimens instrumented with screw and hook was significantly higher than in those instrumented with pedicle screws alone. The ultimate strength and energy absorbed did not differ between the two groups.
  
  
  CONCLUSIONS
  The addition of sacral foraminal hooks to standard pedicle screw instrumentation constructs across the lumbosacral junction provides more rigid stabilization of the lumbosacral motion segment in this model.
authors.affiliation: Division of Orthopaedic Surgery, Medical College of Georgia, Augusta, USA.
authors.forename: D O
authors.initials: DO
authors.lastname: Stovall
authors.forename: J A
authors.initials: JA
authors.lastname: Goodrich
authors.forename: D
authors.initials: D
authors.lastname: Lundy
authors.forename: S C
authors.initials: SC
authors.lastname: Standard
authors.forename: C
authors.initials: C
authors.lastname: Joe
authors.forename: C D
authors.initials: CD
authors.lastname: Preston
mesh_terms: D015519:Bone Density; D002102:Cadaver; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000378:metabolism / Q000601:surgery*; D008297:Male; D008422:Materials Testing; D009984:Orthopedic Fixation Devices; D013123:Spinal Fusion / Q000379:methods*