Preclinical evaluation of a poly (vinyl alcohol) hydrogel implant as a replacement for the nucleus pulposus.
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.
Allen
Matthew J
MJ
Department of Orthopedic Surgery, SUNY Upstate Medical University, Syracuse, New York 13210, USA. allenm@mail.upstate.edu
Schoonmaker
Joanne E
JE
Bauer
Thomas W
TW
Williams
Philip F
PF
Higham
Paul A
PA
Yuan
Hansen A
HA
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
D001672:Biocompatible Materials; D020100:Hydrogels; D011142:Polyvinyl Alcohol