title: Biomechanical flexion-extension forces in normal canine lumbosacral cadaver specimens before and after dorsal laminectomy-discectomy and pedicle screw-rod fixation.
abstract: OBJECTIVE
  To determine biomechanical flexion-extension forces in cadaveric canine lumbosacral specimens, before and after dorsal laminectomy with partial discectomy, and after dorsal pedicle screw-rod fixation of L7 and S1.
  
  
  METHODS
  Biomechanical cadaver study.
  
  
  METHODS
  Cadaveric spine specimens without lumbosacral pathology from mature, intact Labrador retrievers (n=12).
  
  
  METHODS
  Lumbosacral spine segments were subjected to a constant bending moment from L6 to S1 in a hydraulic 4-point bending materials testing machine. Force and displacement were recorded during each loading cycle constituting 1 complete flexion-extension cycle of the spine. Each spine segment had 3 series of recordings of 5 loading cycles each: (1) intact spine, (2) after surgical destabilization by dorsal laminectomy and partial discectomy, and (3) after surgical stabilization using dorsal pedicle screw-rod fixation.
  
  
  RESULTS
  After dorsal laminectomy and partial discectomy, the neutral zone and range of motion were not different from those in the native spine specimen. After pedicle screw-rod fixation, the neutral zone and range of motion of the instrumented specimen significantly (P<.0001) decreased compared with the native specimen and the specimen after dorsal laminectomy.
  
  
  CONCLUSIONS
  Dorsal laminectomy and partial discectomy does not lead to significant spinal instability in flexion and extension whereas pedicle screw and rod fixation effectively stabilizes the lumbosacral spine.
  
  
  CONCLUSIONS
  Dorsal laminectomy and partial discectomy does not lead to significant spinal instability. Pedicle screw-rod fixation of L7 and S1 may be used to stabilize an unstable L7-S1 junction in dogs with degenerative lumbosacral stenosis.
authors: Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands. B.P.Meij@uu.nl
authors: Björn P
authors: BP
authors: Meij
authors: Niyada
authors: N
authors: Suwankong
authors: Albert J
authors: AJ
authors: Van der Veen
authors: Herman A W
authors: HA
authors: Hazewinkel
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D001696:Biomechanical Phenomena; D001863:Bone Screws / Q000662:veterinary*; D002102:Cadaver; D017586:Diskectomy / Q000379:methods / Q000662:veterinary; D004285:Dogs; D005260:Female; D016268:Internal Fixators / Q000662:veterinary; D007796:Laminectomy / Q000379:methods / Q000662:veterinary; D008161:Lumbosacral Region / Q000502:physiology / Q000601:surgery*; D008297:Male; D016059:Range of Motion, Articular; D012399:Rotation; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods / Q000662:veterinary*
chemical_list: D001672:Biocompatible Materials