Growth in the medical device industry has hit an all-time high in recent years, with predictions of the market topping $398 billion this year and strong predictions through 2023. Within this market, the global implant sector is worth $200 million and 20% of all adults are now estimated to have received surgical implants.

Magnesium alloys, commonly used in aerospace, performance cars, and nuclear industries, are now being used in medical devices, as research has proven that magnesium demonstrates biosafety and biocompatibility. New development has also found magnesium to be osteoconductive – promoting bone growth – and combined with its strength has been used successfully in veterinary applications to treat beagle tibia fractures. Magnesium alloys also have been developed for CE Marked cardiovascular scaffold implants.

How advantageous is magnesium for the medical device market and what are its properties?

Proven medical device material
Figure 1: The corrosion of the magnesium implant throughout six weeks as it resorbs to its original form, as indicated by similarities to the control. After six weeks, the polymer implant is still visible.

Bioresorbable materials, such as polymers and magnesium alloys, resorb at a steady rate and can achieve optimum healing within the body. The comparatively low strength of polymers limits their use as load bearing medical devices and can subject components to their yield, fracture, wear, and fatigue resistance limits. In addition, polymers can take longer than other bioresorbable materials to degrade. This is longer than the desired timeframe for medical applications.

Magnesium biocompatibility allows the body to remove magnesium corrosion products. Studies examining blood of magnesium implant subjects show resorption causes only slight changes to implant composition, without showing any disorder to the liver or kidneys. An essential trace element within the human body, magnesium has a role in more than 325 enzymatic processes, and the adult body typically contains approximately 25g of magnesium.

Challenges with magnesium have included rapid degradation, with the material resorbing too quickly under physiological conditions. However, advancements allow the degradation rate to be tailored to suit each medical device’s need. Technology company Magnesium Elektron has worked on developing alloys which ensure stable corrosion rates.

Medical magnesium

Magnesium alloys are used for medical implants, such as vascular stents, and are being evaluated for use in bone repair applications, replacing titanium or stainless steel devices. However, these are permanent implants that do not degrade but often require costly, stressful removal once the injury is healed. Orthopedic screws also require strong bone integration, and unlike titanium, magnesium’s corroding surface allows bone to integrate into the implant as it resorbs.

Figure 1 (page 19) shows that during a 6-week experiment, the magnesium implant resorbed and the bone returned to the same state as the control, degrading within the human body and matching resorption kinetics during the healing period. In comparison, a polymer implant is still visible after six weeks.

Studies using SynerMag, an alloy from Magnesium Elektron, were conducted within beagle tibia fractures. All polymer implants broke within the specified timeframe. But only one of the 24 SynerMag magnesium screws broke, and all remained tight.

As a flexible material, magnesium can also be used for wires in medical applications. Working similarly to plates and screws, and keeping their shape during implantation, are fiber-mesh for reinforcing bone filling cements and mesh for stents (see sidebar).

Conclusion

Magnesium alloys have been used in many applications within the medical device market and offer a custom solution to the challenges often encountered. Demonstrating biosafety and biocompatibility, the required bone compatibility, and strength to be used within the body, magnesium can also be designed to resorb at the correct rate for each individual need, rendering it suitable for multiple applications.

Magnesium Elektron
www.magnesium-elektron.com

About the author: Paul Lyon is programs technology manager at Magnesium Elektron. For additional information please contact Dr. Robert Thornton at +44 (0)161.911.1355.