title: Changes in neuroforaminal height with 2 level axial presacral lumbar interbody fusion at L4-S1.
abstract: BACKGROUND
  The objective was to examine the changes in neuroforaminal height at L4-L5 and L5-S1 after insertion and graduated foraminal distraction using the 2 level transsacral implant in a cadaveric model.
  
  
  METHODS
  Discectomy and transsacral instrumentation was performed in six fresh human cadavers at L4-S1. The neuroforaminal height was measured at L4-L5 and L5-S1 before and after insertion of the implant and then at each stage of manual distraction.
  
  
  RESULTS
  Mean L4-5 neuroforaminal height increased from 18.2 ± 3.1mm to 20.3± 2.9mm (11%) on the left and from 18.8±2.8mm to 20.6± 2.3mm (12%) on the right (P<0.05). Mean L5-S1 neuroforaminal height increased from 15.7±3.0mm to 18.4 ±2.8mm (17%) on the left and from 15.6 ±2.1mm to 18.3 ±1.8mm (17%) on the right (P<0.05). When the neuroforaminal height was plotted against amount of rotation of the screw driver it was found that the neuroforaminal height at L5-S1 increased by 1mm on average for every complete revolution of the screw driver. At least 2 full rotations of the screw driver were achieved in all cadavers.
  
  
  CONCLUSIONS
  The transsacral screw construct distracted the disc space and neuroforaminal height in a cadaveric spine model without soft tissue envelope. During the initial process, manual control of disc space distraction predictably correlated with the increase in the neuroforaminal height to a maximum. However, further research is needed to look at variables affecting disc space pliability, implant subsidence, in vivo application, and clinical benefit of this procedure.
authors.affiliation: Orthopedic Surgery, SUNY Upstate Medical University.
authors.forename: Satyajit
authors.initials: S
authors.lastname: Marawar
authors.affiliation: Orthopedic Surgery, SUNY Upstate Medical University.
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Ordway
authors.affiliation: Orthopedic Surgery, SUNY Upstate Medical University.
authors.forename: Jin
authors.initials: J
authors.lastname: Jung
authors.affiliation: Orthopedic Surgery, SUNY Upstate Medical University.
authors.forename: Mike
authors.initials: M
authors.lastname: Sun
keywords: AxiaLIF; Lumbar; decompression; discectomy; spinal fusion