title: Mechanical properties and in vivo performance of load-bearing fiber-reinforced composite intramedullary nails with improved torsional strength.
abstract: Fiber-reinforced composites (FRC) could be feasible materials for fracture fixation devices if the mechanical properties of the composites are congruent with the local structural properties of bone. In a recently developed FRC implant, bisphenol A dimethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA) resin was reinforced with unidirectional E-glass fibers. The addition of a braided glass fiber sleeving to the unidirectional fibers increased the torsional strength (99.5MPa) of the FRC implants at the expense of the flexural strength (602.0MPa). The flexural modulus was 15.3GPa. Two types of FRC intramedullary nails were prepared; first type was FRC as such, second type was FRC with a surface layer of bioactive glass (BG) granules. Experimental oblong subtrochanteric defect was created in 14 rabbits. The defect, which reduced the torsional strength of the bones by 66%, was fixed with an FRC intramedullary nail of either type. The contralateral intact femur served as the control. This model simulated surgical stabilization of bone metastasis. After 12 weeks of follow-up, the femurs were harvested and analyzed by torsional testing, micro-CT and hard tissue histology. Healed undisplaced peri-implant fractures were noticed in half of the animals irrespective of the type of FRC implant. Torsional testing showed no significant differences between the implantation groups. The torsional strength of the bones stabilized by either type of FRC implant was 83% of that of the contralateral femurs. In histological analysis, no implant debris and no adverse tissue reactions were observed. While the mechanical properties of the modified FRCs were suboptimal, the FRC intramedullary nails supported the femurs without structural failure, even in the cases of peri-implant fractures.
authors.affiliation: Orthopaedic Research Unit, Department of Orthopedic Surgery and Traumatology, University of Turku and University Central Hospital, FI-20520 Turku, Finland; Turku Clinical Biomaterials Centre - TCBC, Department of Biomaterials Science, Institute of Dentistry, University of Turku, FI-20520 Turku, Finland.
authors.forename: N
authors.initials: N
authors.lastname: Moritz
authors.affiliation: Orthopaedic Research Unit, Department of Orthopedic Surgery and Traumatology, University of Turku and University Central Hospital, FI-20520 Turku, Finland.
authors.forename: N
authors.initials: N
authors.lastname: Strandberg
authors.affiliation: Orthopaedic Research Unit, Department of Orthopedic Surgery and Traumatology, University of Turku and University Central Hospital, FI-20520 Turku, Finland.
authors.forename: D S
authors.initials: DS
authors.lastname: Zhao
authors.affiliation: Turku Clinical Biomaterials Centre - TCBC, Department of Biomaterials Science, Institute of Dentistry, University of Turku, FI-20520 Turku, Finland.
authors.forename: R
authors.initials: R
authors.lastname: Mattila
authors.affiliation: INGEO Snc., Varallo Pombia, NO, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Paracchini
authors.affiliation: Turku Clinical Biomaterials Centre - TCBC, Department of Biomaterials Science, Institute of Dentistry, University of Turku, FI-20520 Turku, Finland.
authors.forename: P K
authors.initials: PK
authors.lastname: Vallittu
authors.affiliation: Orthopaedic Research Unit, Department of Orthopedic Surgery and Traumatology, University of Turku and University Central Hospital, FI-20520 Turku, Finland. Electronic address: hannu.aro@utu.fi.
authors.forename: H T
authors.initials: HT
authors.lastname: Aro
mesh_terms: D000818:Animals; D001559:Benzhydryl Compounds / Q000737:chemistry*; D001858:Bone Nails; D005269:Femur / Q000000981:diagnostic imaging / Q000502:physiology; D008297:Male; D008422:Materials Testing; D055595:Mechanical Phenomena; D008689:Methacrylates / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011109:Polymethacrylic Acids / Q000737:chemistry*; D011817:Rabbits; D013329:Structure-Activity Relationship; D016474:Weight-Bearing; D055114:X-Ray Microtomography; D000098826:Bisphenol A Compounds
chemical_list: D001559:Benzhydryl Compounds; D008689:Methacrylates; D011092:Polyethylene Glycols; D011109:Polymethacrylic Acids; C020946:triethylene glycol dimethacrylate; C002462:4,4'-isopropylidenediphenol dimethacrylate; D000098826:Bisphenol A Compounds
keywords: Fiber-reinforced composites; Implant; Intramedullary nail; Mechanical testing; Orthopedic surgery