Bone breakthrough may lead to aerospace advances


CHRISTOPHER HERNANDEZ:
So in this study, we’re trying to understand
how the structure of bone influences how it breaks. For the last 30 years or so,
we’ve known that how dense a bone is determines how
strong and how stiff it is. But in this study, we
weren’t looking at how strong and stiff the bone is. We were looking at how well
it resists cyclic loading. You can imagine
that every year, you put hundreds of
thousands or millions of cycles of loading
on your bone. So hip fractures
and wrist fractures are common
osteoporosis-related fractures, but they’re always
associated with a fall. In the spine, though, most
of the time, the patient doesn’t know what happened
that caused the bone to break. And so we think it’s because
the bones in your spine are breaking due
to cyclic loading. And if you go back
for the last 25 years, everybody said it’s all about
the struts in the bone that are pointing in
the same direction that you’re loading
it, and that’s what determines how strong
and how stiff the bone is. And what’s novel about what we
found in this study is that it wasn’t we’re those struts
that are pointing vertically, resisting load, that was
important for cyclic loading. It was these thin,
small struts that are pointing sideways that
was really, really important. So one of the ways we
made this discovery is we had a lot of bone specimens. And we saw a trend in
human-bone specimens relating fatigue loading
to these sideways struts. But to really prove it,
we used a 3D printer to make models where
we had modified just those sideways struts. And we proved that if we make
very, very small adjustments to those sideways
struts, we can increase the number of cycles the bone
can take by 10 to 100 times. And so what we’ve shown is that
this aspect of microstructure where you put those struts
and how thick they are can have an extremely large
effect on how many cycles the material can take
before it breaks. And in the aerospace
industry, that’s extremely important because
they’re large, durable devices. You’re very, very interested
in how many cycles to failure that material can take.

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