Biomedical Magnesium Alloys: A Review of Material Properties, Surface Modifications and Potential as a Biodegradable Orthopaedic Implant

Abstract

Magnesium and magnesium based alloys are lightweight metallic materials that are extremely biocompatib le and have similar mechanical properties to natural bone. These materials have the potential to function as an osteoconductive and biodegradable substitute in load bearing applicat ions in the field of hard t issue engineering. However, the effects of corrosion and degradation in the physiological environ ment of the body has prevented their wide spread applicat ion to date. The aim o f this review is to examine the properties, chemical stability, degradation in situ and methods of improving the corrosion resistance of magnesium and its alloys for potential application in the orthopaedic field. To be an effective imp lant, the surface and sub-surface properties of the material needs to be carefully selected so that the degradation kinetics of the implant can be efficiently controlled. Several surface modification techniques are presented and their effectiveness in reducing the corrosion rate and methods of controlling the degradation period are discussed. Ideally, balancing the gradual loss of material and mechanical strength during degradation, with the increasing strength and stability of the newly forming bone tissue is the ultimate goal. If this goal can be achieved, then orthopaedic implants manufactured fro m magnesium based alloys have the potential to deliver successful clinical outcomes without the need for revision surgery.

Expandable Mg-based Helical Stent Assessment using Static, Dynamic, and Porcine Ex Vivo Models

“…However, this process is complex and it can increase fabrication costs. Given the Mg-based metals’ mechanical properties for pure magnesium: (density of 1.74 gcm −3 ; elastic modulus of 45 GPa; compressive yield strength (0.2% CYS); ultimate compressive strength of 87 ± 4 MPa and 240 ± 9 MPa; tensile yield strength (0.2% YS) and ultimate tensile strength of 125 ± 9 MPa and 169 ± 11 MPa 15–17 ), the conventional manufacturing approach of laser engraved Mg tubbing suffers from considerable limitations. The intrinsic low ductility of bioresorbable metals, which need to balloon-expand without losing mechanical strength, brings another limitation 17 .…”

Building towards a standardised approach to biocorrosion studies: a review of factors influencing Mg corrosion in vitro pertinent to in vivo corrosion

“…These are different to traditional metallic biomaterials, which are dominated by corrosion resistant metals such as titanium, cobalt-chromium alloys and stainless steel [2]. The key application for biodegradable metals is for temporary medical implants and devices [3][4][5][6][7]. Biodegradable metals corrode and disappear after implantation.…”

Osseoconductive and Corrosion-Inhibiting Plasma-Sprayed Calcium Phosphate Coatings for Metallic Medical Implants

“…The favorable mechanical properties of Mg alloy include a high stiffness-to-mass ratio ((9 − 26) × 10 6 m 2 ·s −2 ) and, in particular, an elastic modulus (17 GPa in shear, 45 GPa in tension) in the range of that of cortical bone GPa in tension). This suggests the eventual emergence of a novel biomaterial able to mitigate or even alleviate stress shielding [14] (see Section 5.2) caused by elastic property mismatch between implant and bone. Hence, effort is being expended on designing implant materials with a modulus that approaches that of bone.…”