In Vivo Performance and Structural Relaxation of Biodegradable Bone Implants Made from Mg-Zn-Ca Bulk Metallic Glasses

A study of Mg-based bulk metallic glasses (BMGs) as biodegradable bone implants is presented. The implantation site can affect performance, so the BMGs were evaluated in vivo in rat femurs using mu-CT scans at various times for more than 90 days. Estimates of H2 evolution correlate well with previous in vitro studies and boneimplant contact is similar to that for Ti pins. One potential drawback of Mg-based BMGs in this application is embrittlement due to structural relaxation. Here, relaxation at 20 and 37?degrees C is examined, and an increase in the characteristic relaxation time, from 10 to 30 days at 20?degrees C, is observed as Zn increases from 29 to 32?at.%, correlating with dramatically reduced hydrogen evolution.