title: A new concept for implant fixation: bone-to-bone biologic fixation.
abstract: Many attempts have been made to reduce complications of bone implant, such as pedicle screw loosening. To address this problem, the authors suggest a new concept of bone-to-bone biologic fixation using recombinant human bone morphogenetic protein-2 (rhBMP-2)-loaded cannulated pedicle screws. Recombinant human bone morphogenetic protein-2 is an osteoinductive cytokine. Four types of titanium pedicle screws were tested (uncannulated, cannulated with no loading, beta-tricalcium phosphate (TCP)-loaded, and TCP/BMP2 loaded) using 16 miniature pigs. Radiological evaluation was conducted to assess the fusion and loosening of pedicle screws. Twelve weeks after implantation, peak torsional extraction torque was measured, and the pedicle screw and bone interface was evaluated by micro-computed tomography (µCT) and histologic examination. The mean value of the radiological score was significantly greater in the TCP/BMP2 loaded group at 12 weeks post-operation compared to those in the other groups. CT images showed distinct bone formation surrounding TCP/BMP2 loaded cannulated pedicle screws compared to the other groups. Mean extraction torsional peak torque at 12 weeks postoperative was more than 10-fold higher in the TCP/BMP2 loaded pedicle screw group than in the other groups. Bone surface and bone volume, as quantitated through µCT, were higher in the TCP/BMP2 loaded group. Histologic examination revealed bone-to-bone fixation at the interface of pedicle screws and pre-existing bone. Bone-to-bone biologic fixation through the holes of TCP/BMP2 loaded pedicle screws significantly increased fixation strength and represents a novel method that can be applied to osteoporotic or tumour spine surgeries.
authors.affiliation: Department of Orthopaedic Surgery, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Chonbuk National University Medical School, 634-18 Keumam-dong, Jeonju-shi, Chonbuk-do, South Korea.osdr2815@naver.com.
authors.forename: D-Y
authors.initials: DY
authors.lastname: Kim
authors.forename: J-R
authors.initials: JR
authors.lastname: Kim
authors.forename: K Y
authors.initials: KY
authors.lastname: Jang
authors.forename: K-B
authors.initials: KB
authors.lastname: Lee
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000502:physiology / Q000601:surgery*; D002130:Calcium Phosphates / Q000494:pharmacology; D005260:Female; D006801:Humans; D019637:Orthopedic Procedures / Q000295:instrumentation* / Q000379:methods; D016348:Osseointegration / Q000187:drug effects; D065289:Pedicle Screws; D011994:Recombinant Proteins / Q000494:pharmacology; D013552:Swine; D013556:Swine, Miniature; D013997:Time Factors; D014025:Titanium; D019415:Torque; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D055114:X-Ray Microtomography
chemical_list: D055396:Bone Morphogenetic Protein 2; D002130:Calcium Phosphates; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C485817:beta-tricalcium phosphate; C499469:recombinant human bone morphogenetic protein-2; D014025:Titanium