title: Incision of the anulus fibrosus induces nerve root morphologic, vascular, and functional changes. An experimental study.
abstract: METHODS
  The effects on nerve root structure, vasculature, and function after incision of the adjacent disc was studied in a dog model.
  
  
  OBJECTIVE
  To see if only incision of the disc per se is sufficient for inducing similar changes.
  
  
  BACKGROUND
  It is well known that nucleus pulposus will induce nerve root structural and functional changes in experimental situations. In these previous studies, relatively large amounts of nucleus pulposus were applied.
  
  
  METHODS
  The left L7 nerve root was exposed and mobilized in 10 dogs. In five dogs, the adjacent L6-L7 disc was incised, and in five other dogs, the disc was not incised. After 7 days, nerve conduction velocity was recorded, and specimens were obtained for histologic evaluation.
  
  
  RESULTS
  The nerve conduction velocity was significantly lower in the incision group (13 +/- 14 m/sec) compared with the nonincision group (73 +/- 5 m/sec). Structural changes of the axons were more pronounced in the incision group, however, the degree and distribution was too limited to fully account for the neurophysiologic reactions observed. There aims were obvious signs of capillary stasis with an increased number and diameter of the intraneural capillaries in the incision group.
  
  
  CONCLUSIONS
  The present study indicated that incision of the anulus fibrosus is sufficient to induce significant morphologic and functional changes and that vascular mechanisms may be of importance for the observed changes. These experimental data suggest that leakage of nucleus pulposus material from anular tears, with injury to adjacent nerve roots, might be one pathophysiologic mechanism in patients with low back pain and sciatica but with no radiologic or surgical evidence of disc herniation.
authors.affiliation: Department of Orthopaedic Surgery, Fukushima Medical College, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kayama
authors.forename: S
authors.initials: S
authors.lastname: Konno
authors.forename: K
authors.initials: K
authors.lastname: Olmarker
authors.forename: S
authors.initials: S
authors.lastname: Yabuki
authors.forename: S
authors.initials: S
authors.lastname: Kikuchi
mesh_terms: D000818:Animals; D004285:Dogs; D009431:Neural Conduction; D013126:Spinal Nerve Roots / Q000098:blood supply / Q000293:injuries / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery*