title: Small intestinal submucosa for anular defect closure: long-term response in an in vivo sheep model.
abstract: METHODS
  After undergoing anulotomy, lumbar intervertebral discs from sheep were treated with small intestinal submucosa (SIS) and assessed functionally at 24 weeks after surgery.
  
  
  OBJECTIVE
  To determine the efficacy of an SIS-based patch and plug scaffold to facilitate anular defect closure and anular functional recovery after anulotomy and partial discectomy.
  
  
  BACKGROUND
  The incidence of reherniation following discectomy remains high and mechanical means of anular closure have met with limited success. SIS is a naturally occurring collagen-based material, which acts as a resorbable scaffold in vivo that promotes soft tissue regeneration.
  
  
  METHODS
  Twelve sheep underwent retroperitoneal exposure of the lumbar spine. Three levels were assigned to either: no additional procedure, box anulotomy alone, or box anulotomy followed by placement of an SIS "patch and plug" anchored by titanium bone screws. At 26 weeks after surgery, 18 motion segments underwent pressure-volume testing to assess the competency of the anulus. High resolution MRI images were taken of the remaining 18 segments. Undecalcified histology was conducted on all specimens.
  
  
  RESULTS
  Radiographs, MRI images, and histology indicate that there was an exuberant tissue response at SIS-treated levels. New tissue formation in SIS-treated specimens was integrated well with the native anulus, but did not resemble the organization of native anulus. The extent of anular closure was substantial enough to allow the disc a functional recovery to a mean 66% of its capacity to develop internal pressure. MRI images indicate that SIS-treated levels did not maintain signal intensity comparable to exposure-only (intact) levels, but SIS-treated discs were statistically significantly higher than anulotomy-only levels.
  
  
  CONCLUSIONS
  SIS-treated discs were better able to maintain hydration and resulted in a functional recovery relative to anulotomy alone levels. The SIS patch and plug reduced the cascade of functional degeneration that an intervertebral disc undergoes following anulotomy.
authors.affiliation: Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA. ledete@rpi.edu
authors.forename: Eric H
authors.initials: EH
authors.lastname: Ledet
authors.forename: Winston
authors.initials: W
authors.lastname: Jeshuran
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Glennon
authors.forename: Christopher
authors.initials: C
authors.lastname: Shaffrey
authors.forename: Patrick
authors.initials: P
authors.lastname: De Deyne
authors.forename: Cliff
authors.initials: C
authors.lastname: Belden
authors.forename: Bhaskar
authors.initials: B
authors.lastname: Kallakury
authors.forename: Allen L
authors.initials: AL
authors.lastname: Carl
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry / Q000627:therapeutic use; D001863:Bone Screws; D017586:Diskectomy / Q000295:instrumentation / Q000379:methods*; D007403:Intervertebral Disc / Q000187:drug effects / Q000601:surgery* / Q000648:ultrastructure; D007405:Intervertebral Disc Displacement / Q000601:surgery* / Q000628:therapy; D007413:Intestinal Mucosa / Q000737:chemistry / Q000637:transplantation*; D007421:Intestine, Small / Q000737:chemistry / Q000637:transplantation; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D008855:Microscopy, Electron, Scanning; D011859:Radiography; D012756:Sheep; D013552:Swine; D014025:Titanium
chemical_list: D001672:Biocompatible Materials; D014025:Titanium