title: In vivo study of magnesium plate and screw degradation and bone fracture healing.
abstract: Each year, millions of Americans suffer bone fractures, often requiring internal fixation. Current devices, like plates and screws, are made with permanent metals or resorbable polymers. Permanent metals provide strength and biocompatibility, but cause long-term complications and may require removal. Resorbable polymers reduce long-term complications, but are unsuitable for many load-bearing applications. To mitigate complications, degradable magnesium (Mg) alloys are being developed for craniofacial and orthopedic applications. Their combination of strength and degradation make them ideal for bone fixation. Previously, we conducted a pilot study comparing Mg and titanium devices with a rabbit ulna fracture model. We observed Mg device degradation, with uninhibited healing. Interestingly, we observed bone formation around degrading Mg, but not titanium, devices. These results highlighted the potential for these fixation devices. To better assess their efficacy, we conducted a more thorough study assessing 99.9% Mg devices in a similar rabbit ulna fracture model. Device degradation, fracture healing, and bone formation were evaluated using microcomputed tomography, histology and biomechanical tests. We observed device degradation throughout, and calculated a corrosion rate of 0.40±0.04mm/year after 8 weeks. In addition, we observed fracture healing by 8 weeks, and maturation after 16 weeks. In accordance with our pilot study, we observed bone formation surrounding Mg devices, with complete overgrowth by 16 weeks. Bend tests revealed no difference in flexural load of healed ulnae with Mg devices compared to intact ulnae. These data suggest that Mg devices provide stabilization to facilitate healing, while degrading and stimulating new bone formation.
authors.affiliation: The Center for Craniofacial Regeneration, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; The McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Amy
authors.initials: A
authors.lastname: Chaya
authors.affiliation: The Center for Craniofacial Regeneration, University of Pittsburgh, Pittsburgh, PA, USA; Department of Oral Biology, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Sayuri
authors.initials: S
authors.lastname: Yoshizawa
authors.affiliation: The Center for Craniofacial Regeneration, University of Pittsburgh, Pittsburgh, PA, USA; Department of Oral Biology, University of Pittsburgh, Pittsburgh, PA, USA; The McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Kostas
authors.initials: K
authors.lastname: Verdelis
authors.affiliation: The Center for Craniofacial Regeneration, University of Pittsburgh, Pittsburgh, PA, USA; Department of Oral Biology, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Nicole
authors.initials: N
authors.lastname: Myers
authors.affiliation: The Center for Craniofacial Regeneration, University of Pittsburgh, Pittsburgh, PA, USA; The McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA; Department of Oral and Maxillofacial Surgery, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Costello
authors.affiliation: The Center for Craniofacial Regeneration, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; The McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Da-Tren
authors.initials: DT
authors.lastname: Chou
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Siladitya
authors.initials: S
authors.lastname: Pal
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Spandan
authors.initials: S
authors.lastname: Maiti
authors.affiliation: The Center for Craniofacial Regeneration, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Oral Biology, University of Pittsburgh, Pittsburgh, PA, USA; The McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Prashant N
authors.initials: PN
authors.lastname: Kumta
authors.affiliation: The Center for Craniofacial Regeneration, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Oral Biology, University of Pittsburgh, Pittsburgh, PA, USA; The McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA. Electronic address: csfeir@pitt.edu.
authors.forename: Charles
authors.initials: C
authors.lastname: Sfeir
mesh_terms: D000818:Animals; D001846:Bone Development / Q000187:drug effects; D001860:Bone Plates; D001863:Bone Screws; D017102:Fracture Healing / Q000187:drug effects*; D008274:Magnesium / Q000494:pharmacology*; D008422:Materials Testing; D011817:Rabbits; D014457:Ulna / Q000000981:diagnostic imaging / Q000187:drug effects / Q000473:pathology; D014458:Ulna Fractures / Q000000981:diagnostic imaging / Q000473:pathology*; D055114:X-Ray Microtomography
chemical_list: D008274:Magnesium
keywords: Fixation devices; Fracture fixation; Magnesium; MicroCT