title: Long-term study of high-strength hydroxyapatite/poly(L-lactide) composite rods for the internal fixation of bone fractures: a 2-4-year follow-up study in rabbits.
abstract: Biodegradation of hydroxyapatite (HA)/poly(L-lactide)(PLLA) composite bone implant rods was studied with the use of two types of HA particles as reinforcing fillers: uncalcined HA (u-HA) or calcined HA (c-HA). Composite rods of u-HA/PLLA and c-HA/PLLA containing 30 or 40% (w/w) HA were implanted in the distal femur of 21 rabbits, and specimens were examined by light microscopy, scanning-electron microscopy (SEM), and transmission-electron microscopy (TEM) 2-4 years later. For u-HA/PLLA, trabecular bone bonding directly onto the rod was maintained for up to 2 years. By 3 years, surface collapse had begun, and the implants were shrinking. By 4 years, they had shrunk further, with complete bone encapsulation. The u-HA particles were small and needle shaped in the peripheries, and TEM confirmed their resorption. The cross-sectional area after 4 years decreased by 23.3+/-8.4%. The mean ratio of bony ingrowth to the initial cross-sectional area around the shrunken rods was 6.7+/-1.3 %. The viscosity molecular weight of PLLA reduced from 2 x 10(5) to less than 1 x 10(3). Thus, most of the PLLA had released from the rods. The c-HA/PLLA implants also showed good osteoconductivity, but shrinkage and infiltration of histiocytes were less. No osteolytic or osteoarthritic changes were found.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, Shogoin-kawahara-cho 54, Sakyo-ku, Kyoto 606-8507, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Ishii
authors.forename: Jiro
authors.initials: J
authors.lastname: Tamura
authors.forename: Taizo
authors.initials: T
authors.lastname: Furukawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakamura
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Matsusue
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Shikinami
authors.forename: Masaki
authors.initials: M
authors.lastname: Okuno
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D001672:Biocompatible Materials / Q000378:metabolism*; D005269:Femur / Q000000981:diagnostic imaging / Q000378:metabolism / Q000601:surgery / Q000648:ultrastructure; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006882:Hydroxyapatites / Q000378:metabolism*; D016268:Internal Fixators; D008297:Male; D016348:Osseointegration; D011091:Polyesters / Q000378:metabolism*; D011817:Rabbits; D011859:Radiography
chemical_list: D001672:Biocompatible Materials; D006882:Hydroxyapatites; D011091:Polyesters; C033616:poly(lactide)