title: Magnesium alloys for temporary implants in osteosynthesis: in vivo studies of their degradation and interaction with bone.
abstract: This study investigates the bone and tissue response to degrading magnesium pin implants in the growing rat skeleton by continuous in vivo microfocus computed tomography (μCT) monitoring over the entire pin degradation period, with special focus on bone remodeling after implant dissolution. The influence of gas release on tissue performance upon degradation of the magnesium implant is also addressed. Two different magnesium alloys - one fast degrading (ZX50) and one slowly degrading (WZ21) - were used for evaluating the bone response in 32 male Sprague-Dawley rats. After femoral pin implantation μCTs were performed every 4 weeks over the 24 weeks of the study period. ZX50 pins exhibited early degradation and released large hydrogen gas volumes. While considerable callus formation occurred, the bone function was not permanently harmed and the bone recovered unexpectedly quickly after complete pin degradation. WZ21 pins kept their integrity for more than 4 weeks and showed good osteoconductive properties by enhancing bone accumulation at the pin surface. Despite excessive gas formation, the magnesium pins did not harm bone regeneration. At smaller degradation rates, gas evolution remained unproblematic and the magnesium implants showed good biocompatibility. Online μCT monitoring is shown to be suitable for evaluating materials degradation and bone response in vivo, providing continuous information on the implant and tissue performance in the same living animal.
authors: Department of Pediatric Orthopedics, Medical University Graz, 8036 Graz, Austria.
authors: Tanja
authors: T
authors: Kraus
authors: Stefan F
authors: SF
authors: Fischerauer
authors: Anja C
authors: AC
authors: Hänzi
authors: Peter J
authors: PJ
authors: Uggowitzer
authors: Jörg F
authors: JF
authors: Löffler
authors: Annelie M
authors: AM
authors: Weinberg
mesh_terms: D000497:Alloys; D000818:Animals; D001858:Bone Nails; D001861:Bone Regeneration; D005264:Femoral Fractures / Q000378:metabolism / Q000628:therapy*; D005269:Femur; D006859:Hydrogen / Q000378:metabolism; D008274:Magnesium; D008297:Male; D008422:Materials Testing; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D055114:X-Ray Microtomography; D015032:Zinc
chemical_list: D000497:Alloys; D006859:Hydrogen; D008274:Magnesium; D015032:Zinc