title: In vivo biostability of polymeric spine implants: retrieval analyses from a United States investigational device exemption study.
abstract: The Dynesys System for stabilizing the lumbar spine was first surgically implanted in Europe in 1994. In 2003, a prospective, randomized, investigational device exemption clinical trial of the system for non-fusion dynamic stabilization began. Polycarbonate urethane (PCU) and polyethylene terephthalate (PET) components explanted from four patients who had participated in the study were analyzed for biostability. Components had been implanted 9-19 months. The explanted components were visually inspected and digitally photographed. Scanning electron microscopy was used to analyze the surface of the spacers. The chemical and molecular properties of the retrieved spacers and cords were quantitatively compared with lot-matched, shelf-aged, components that had not been implanted using attenuated total reflection Fourier transform infrared (FTIR) and gel permeation chromatography (GPC). FTIR analyses suggested that the explanted spacers exhibited slight surface chemical changes but were chemically unchanged below the surface and in the center. New peaks that could be attributed to biodegradation of PCU were not observed. The spectral analyses for the cords revealed that the PET cords were chemically unchanged at both the surface and the interior. Peaks associated with the PET biodegradation were not detected. GPC results did not identify changes to the distributions of molecular weights that might be attributed to biodegradation of either PCU spacers or PET cords. The explanted condition of the retrieved components demonstrated the biostability of both PCU spacers and PET cords that had been in vivo for up to 19 months.
authors.affiliation: Zimmer Inc, 1800 West Center St, Warsaw, IN 4658, USA. ming.shen@zimmer.com
authors.forename: Ming
authors.initials: M
authors.lastname: Shen
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.forename: Petra
authors.initials: P
authors.lastname: Koettig
authors.forename: William C
authors.initials: WC
authors.lastname: Welch
authors.forename: John M
authors.initials: JM
authors.lastname: Dawson
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D011108:Polymers / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D019736:Prostheses and Implants; D013130:Spinal Stenosis / Q000601:surgery*; D014481:United States
chemical_list: D001672:Biocompatible Materials; D011108:Polymers; D011140:Polyurethanes