title: Loss of mechanical properties in vivo and bone-implant interface strength of AZ31B magnesium alloy screws with Si-containing coating.
abstract: In this study the loss of mechanical properties and the interface strength of coated AZ31B magnesium alloy (a magnesium-aluminum alloy) screws with surrounding host tissues were investigated and compared with non-coated AZ31B, degradable polymer and biostable titanium alloy screws in a rabbit animal model after 1, 4, 12 and 21weeks of implantation. The interface strength was evaluated in terms of the extraction torque required to back out the screws. The loss of mechanical properties over time was indicated by one-point bending load loss of the screws after these were extracted at different times. AZ31B samples with a silicon-containing coating had a decreased degradation rate and improved biological properties. The extraction torque of Ti6Al4V, poly-l-lactide (PLLA) and coated AZ31B increased significantly from 1week to 4weeks post-implantation, indicating a rapid osteosynthesis process over 3weeks. The extraction torque of coated AZ31B increased with implantation time, and was higher than that of PLLA after 4weeks of implantation, equalling that of Ti6Al4V at 12weeks and was higher at 21weeks. The bending loads of non-coated AZ31B and PLLA screws degraded sharply after implantation, and that of coated AZ31B degraded more slowly. The biodegradation mechanism, the coating to control the degradation rate and the bioactivity of magnesium alloys influencing the mechanical properties loss over time and bone-implant interface strength are discussed in this study and it is concluded that a suitable degradation rate will result in an improvement in the mechanical performance of magnesium alloys, making them more suitable for clinical application.
authors.affiliation: Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, People's Republic of China. Electronic address: lltan@imr.ac.cn.
authors.forename: Lili
authors.initials: L
authors.lastname: Tan
authors.affiliation: Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, People's Republic of China; School of Stomatology, China Medical University, Shenyang 110002, People's Republic of China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, People's Republic of China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Lin
authors.affiliation: Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, People's Republic of China.
authors.forename: Peng
authors.initials: P
authors.lastname: Wan
authors.affiliation: School of Stomatology, China Medical University, Shenyang 110002, People's Republic of China.
authors.forename: Guangdao
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Department of Orthopaedics, General Hospital of the People's Liberation Army, Beijing 100853, People's Republic of China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, People's Republic of China. Electronic address: kyang@imr.ac.cn.
authors.forename: Ke
authors.initials: K
authors.lastname: Yang
mesh_terms: D000497:Alloys / Q000494:pharmacology*; D000818:Animals; D001863:Bone Screws; D001842:Bone and Bones / Q000187:drug effects / Q000502:physiology*; D020099:Coated Materials, Biocompatible / Q000494:pharmacology*; D003343:Corrosion; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000494:pharmacology*; D055595:Mechanical Phenomena; D056951:Photoelectron Spectroscopy; D019736:Prostheses and Implants; D019919:Prosthesis Implantation; D011817:Rabbits; D012825:Silicon / Q000494:pharmacology*; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D019415:Torque
chemical_list: D000497:Alloys; D020099:Coated Materials, Biocompatible; C586533:Mg-Al-Zn-Mn-Si-Cu alloy; D008274:Magnesium; D012825:Silicon
keywords: Bone–implant interface strength; Magnesium alloy; Mechanical properties loss; Si-containing coating