title: Preclinical evaluation of a poly (vinyl alcohol) hydrogel implant as a replacement for the nucleus pulposus.
abstract: METHODS
  An in vivo investigation into the safety of a novel hydrogel implant designed to replace the diseased nucleus pulposus.
  
  
  OBJECTIVE
  To determine the local and systemic safety of this new implant in a nonhuman primate model.
  
  
  BACKGROUND
  A poly (vinyl alcohol) (PVA) hydrogel has been developed as a prosthetic replacement for the diseased nucleus pulposus.
  
  
  METHODS
  PVA implants were inserted into discectomy defects created in the L3-L4 or L4-L5 intervertebral disc in 20 male baboons. Empty discectomy defects served as a surgical control in 8 additional animals. Routine follow-up evaluations included radiography, magnetic resonance imaging, gross pathology, and histopathology of both local and remote tissues.
  
  
  RESULTS
  Insertion of the PVA hydrogel from an anterior direction produced extrusions in 5 animals from the first series of 15 surgeries (33%). A modified surgical technique, involving an anterolateral rather than anterior approach, was used in 5 animals, but the extrusion rate remained high (20%). Despite these surgical complications, the PVA implants were well tolerated over 24 months in vivo, with no evidence of device-related pathology in the adjacent disc tissue, spinal cord, or remote tissues.
  
  
  CONCLUSIONS
  Implantation of the PVA implant for periods of up to 24 months produced no evidence of local or systemic toxicity. Additional studies are now needed to determine the efficacy of the device in its intended application.
authors.affiliation: Department of Orthopedic Surgery, SUNY Upstate Medical University, Syracuse, New York 13210, USA. allenm@mail.upstate.edu
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Allen
authors.forename: Joanne E
authors.initials: JE
authors.lastname: Schoonmaker
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Bauer
authors.forename: Philip F
authors.initials: PF
authors.lastname: Williams
authors.forename: Paul A
authors.initials: PA
authors.lastname: Higham
authors.forename: Hansen A
authors.initials: HA
authors.lastname: Yuan
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D017586:Diskectomy; D004867:Equipment Design; D020100:Hydrogels; D020007:Implants, Experimental; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000601:surgery* / Q000648:ultrastructure; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery* / Q000648:ultrastructure; D008279:Magnetic Resonance Imaging; D008297:Male; D008422:Materials Testing; D010215:Papio; D011142:Polyvinyl Alcohol; D011859:Radiography; D011897:Random Allocation; D013116:Spinal Cord / Q000648:ultrastructure
chemical_list: D001672:Biocompatible Materials; D020100:Hydrogels; D011142:Polyvinyl Alcohol