Rationale for Processing of a Mg-Zn-Ca Alloy by Equal-Channel Angular Pressing for Use in Biodegradable Implants for Osteoreconstruction

Abstract

Widespread use of Mg-Zn-Ca alloys in clinical orthopedic practice requires improvement of their mechanical properties—in particular, ductility—and enhancement of their bioactivity for accelerated osteoreconstruction. The alloy was studied in two structural states: after homogenization and after equal-channel angular pressing. Immersion and potentiodynamic polarization tests showed that the corrosion rate of the alloy was not increased by deformation. The mass loss in vivo was also statistically insignificant. Furthermore, it was found that deformation did not compromise the biocompatibility of the alloy and did not have any significant effect on cell adhesion and proliferation. However, an extract of the alloy promoted the alkaline phosphatase activity of human mesenchymal stromal cells, which indicates osteogenic stimulation of cells. The osteoinduction of the deformed alloy significantly exceeded that of the homogenized one. Based on the results of this work, it can be concluded that the alloy Mg-1%Zn-0.3%Ca modified by equal-channel angular pressing is a promising candidate for the manufacture of biodegradable orthopedic implants since it stimulates osteogenic differentiation and has greater ductility, which provides it with a competitive advantage in comparison with the homogenized state.

In vitro and in vivo degradation behavior of Mg-0.45Zn-0.45Ca (ZX00) screws for orthopedic applications

“…Previous in vivo studies have revealed that hydrogen gas evolution is primarily found adjacent to Mg–Zn–Ca implants investigated [ 17 , 32 , 39 , 43 , 44 , 148 , 149 ]. Although the composition and volume of the released gas during ZX00 alloy degradation were not investigated in this study, our μCT and histology findings after 6 weeks of implantation revealed numerous gas voids mainly in the intramedullary cavity.…”

Monitoring Dynamic Recrystallisation in Bioresorbable Alloy Mg-1Zn-0.2Ca by Means of an In Situ Acoustic Emission Technique

“…A popular Mg-Zn-Ca alloying system [ 13 , 43 , 44 ] was chosen for the present study. After appropriate thermomechanical treatment, alloys of this kind have an excellent balance between mechanical and corrosion properties [ 45 , 46 , 47 , 48 , 49 ]. The alloy was cast from commercially pure components, and the chemical composition of the alloy-Mg-0.85Zn-0.15Ca-0.012 Zr (all in wt.%) was determined by the optical emission spectrometer ARL 4460 OES (ThermoFisher Scientific, Waltham, MA, USA).…”

An Overview on the Effect of Severe Plastic Deformation on the Performance of Magnesium for Biomedical Applications

“…One of the major concerns regarding the degradation of magnesium in biological applications is the accumulation of hydrogen gas, which is a by-product of corrosion. However, only one of the studies, in which the implants from an Mg–Zn–Ca alloy were inserted subcutaneously, reported the formation of gas under the skin [ 82 ]. A good biological response including bone formation around the implant was observed in pure magnesium and Mg–Ca and Mg–Sr alloys processed via ECAP [ 58 ] and via HPT [ 90 ].…”

“… Corrosion rate reported in samples of magnesium processed via ECAP [ 52 , 55 , 56 , 57 , 58 , 59 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 69 , 71 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 82 , 83 , 84 , 85 , 86 , 87 ] and HPT [ 19 , 88 , 90 , 91 , 92 , 93 , 94 , 95 , 97 , 98 , 99 , 100 ] plotted as a function of the grain size. …”

“… Corrosion rate vs. flow stress of magnesium and its alloys before and after SPD processing. Data from the literature [ 19 , 57 , 58 , 59 , 64 , 66 , 70 , 72 , 76 , 77 , 78 , 79 , 80 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 90 , 91 , 92 , 94 , 100 ]. …”