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How Biodegradable Magnesium Alloys Help Fix Broken Bones

Materials: Analysis of clinical samples reveals the chemistry behind an alloy’s healing potential

by Matt Davenport
January 11, 2016 | A version of this story appeared in Volume 94, Issue 2

A series of X-rays shows a magnesium screw biodegrade.
Credit: Proc. Natl. Acad. Sci. USA
A biodegradable magnesium alloy screw in a person’s wrist, shown after implantation, after six months, and after a year (left to right), slowly disappears. The bright object above is a conventional stainless steel pin.

Metal corrosion is usually a bad thing, but in some instances it can be beneficial, even therapeutic. For example, scientists have been developing biodegradable metal alloys that appear to promote healing when used as replacements for conventional noncorrosive metal pins and screws used to fix broken bones. A team of South Korean and Canadian researchers has now shown how magnesium screws laced with calcium and zinc—elements known to promote bone health—help heal small fractures in hands and wrists (Proc. Natl. Acad. Sci. USA 2016, DOI: 10.1073/pnas.1518238113). Using a variety of techniques, including fluorescence microscopy and energy-dispersive X-ray spectroscopy, the team tracked the water-driven degradation of screws inside patients at Ajou University Hospital for several months. A by-product of this degradation, magnesium hydroxide, spurs calcium phosphate formation near the screw. This activity, in turn, helps induce bone growth, says team member Hyung-Seop Han of the Korea Institute of Science & Technology. The screws, which were approved by the Korea Food & Drug Administration in April, help fractures heal completely in about a year, he adds.


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