New findings could improve implants

Magnesium and its alloys are increasingly being deployed in implants such as screws or plates in bone surgery. The advantage is that this light metal is bioresorbable, so there is no need for a second operation to remove the implant from the body. 

However, magnesium alone is too soft for surgical applications and requires alloying elements to strengthen it. These are generally rare-​earth elements such as yttrium or neodymium, which are foreign to the human body and can accumulate in organs during implant degradation, explains the Federal Institute of Technology in Zurich (ETH) in a statement. 

ETH researchers have now developed a new family of alloys that besides magnesium contain only the alloying elements zinc and calcium, which can also be resorbed by the human body. Currently, too little is known about the mechanisms via which these materials degrade in the body under so-​called physiological conditions, and research is required into how long such an implant will remain in the human body.

It is here that ETH researchers have made an important step: using analytical transmission electron microscopy (TEM), they monitored the dealloying mechanism that governs the precipitates’ dissolution in the magnesium matrix. Unlike earlier findings, they witnessed an ongoing change in the precipitates’ chemical composition, meaning that previous predictions regarding degradation times were mainly false. 

Thanks to the researchers’ findings, it is now possible to design magnesium alloys so that their degradation rate in the body can be better predicted and more precisely controlled, according to the statement. It is an important step towards tailoring magnesium alloys to different patients and medical applications.