Assessment of biomechanical stability and formulation of a statistical model on magnesium based composite in two different milieus

Abstract

Magnesium (Mg) based temporary implants are an appealing new solution to counter the problems associated with the currently available temporary orthopaedic implants, used in fracture fixing. To make the extensive use of Mg-based implants in-vivo, mechanical integrity in the physiological environment is a prerequisite. This study presents an insight into the biomechanical stability of Mg-3Zn/HA (0, 5, and 15 wt % of HA) composites in two different milieus (simulated body fluid (SBF) and serum contained SBF (m-SBF)). After 14 days of static immersion in SBF, ~65% mechanical strength was compromised in the case of 15 wt % HA reinforcement. However, the degradation rate was slowed down by ~35% with the addition of 15 wt % HA in Mg-3Zn. Mg-3Zn/HA composite, when soaked in both fluids, was found to induce apatite layer formation on the surfaces for several days. However, in the case of m-SBF immersion, 15 wt % HA facilitated less precipitation of apatite growth when compared to SBF immersion. Nevertheless, m-SBF immersed 15 wt % HA composite facilitated better corrosion resistance and excellent mechanical stability after 14 days of immersion. The approach thereby assists in establishing an effective mechanism between the degradation and mechanical stability in in-vitro immersion. In addition, this study has also developed a semi-empirical model for prediction of the compressive strength of these composites as a function of the number of days of immersion and the content of hydroxyapatite (HA). This semi-empirical model will help in predicting the biomechanical stability for long-term in-vitro exposures, which might be of use in evaluating the effect of the in-vivo environment. - Mg/HA composites were fabricated by SPS and tested for static immersion in two different physiological environment. - 15HA showed slower degradation rate and effective mechanical integrity (65%) after 14 days soaking in modified-SBF. - Apatite formation could not retain the mechanical integrity of the composites immersed in SBF. - To predict the accurate mechanical integrity of composites for longer duration, a semi-empirical model was developed.