Glass, Plastic Mix Mends Bones

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Years ago I was hit by a motorbike and ended up with a compound fracture of the lower bones of my leg (the tibia and fibula, for aficionados). In order to hold the bones of my leg together as it healed, doctors drove spikes akin to 10-penny nails through my shin and heel and then covered my leg in a cast. I also had to have pins in my right arm to keep the elbow intact. The implants had to be removed, which meant another trip to the surgeon.

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Reducing the number of surgeries would have been welcome, and recently scientists have been working to make implants that can hold bones together and then dissolve when the implants aren’t needed anymore. That’s where a composite of polymer and glass (called “bioglass”) comes in. The idea is to give bones a scaffold to grow on so they can heal properly. As the bones heal, the polymer dissolves. Polymers aren’t stiff and strong enough to hold bone together, and so scientists added glass particles, which gives the polymer extra strength.

The only problem is that to make the implants, the plastic and glass particle mix has to be heat-treated. At higher temperatures the glass particles react with the polymer, making chemicals that you don’t want inside your body.

Jose Ramon Sarasua and Aitor Larrañaga, researchers in the materials engineering department of the University of the Basque Country, have proposed a way around this problem: treat the glass particles with a plasma, an ionized gas that alters the chemistry of the particles’ surface.

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The result is better thermal stability for the implant material — meaning it can be heat-treated like other plastics, and still be safe for use in the body.

Sarasua told Discovery News that the implant his team designed isn’t meant for breaks bigger than an inch or so, at least not yet. And it is designed for situations in which the bones might not heal well. It would, however, be an alternative to the steel pins that often have to be employed now, and reduce the number of surgeries patients with big breaks have to go through.

I’d certainly have said yes to that.

The results were published in the journal Polymer Degradation and Stability.

Top Photo: The implants made of biodegradable polymers. Credit: University of the Basque Country