As humans evolved to stand upright, so too did our skeleton. Over millennia, our knee, hip and shoulder joints changed shape to accommodate the redistribution of weight. But those past changes are the primary reason we experience joint pain today. And although orthopedic doctors have treatments and surgical procedures to address some of those problems, they haven't been able to anticipate how those joints will likely change in the future.
Now, Paul Monk, an orthopedic doctor at Oxford University, and his team have built computer models to predict how those joints will change in the future. The models are being used to not only create a 3D visualization of the very joints surgeons are often called upon to repair but to print 3D models of them.
The ability to glance into the future of the human skeleton is more than a theoretical exercise. It could advance orthopedic therapies and create new treatments or surgical procedures to address the adaptions.
"These models provide valuable insights into what might change over the coming millennia," Monk told Seeker. "They will also help define surgical treatments and physiotherapy modalities."
Monk and his colleagues developed the models by collecting CT scans of bones collected by the Natural History Museum in London and Oxford as well as those from the Smithsonian Institute in Washington, D.C. They analyzed not just bones from humans and early humans, but also from primates and dinosaurs. In all, they scanned 224 bone specimens, spanning 350 million years.
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They built the computer models to map the evolution of the bones by incorporating fundamental principals of Darwinian theory as well as Wolff's law, which was developed by the German anatomist and surgeon Julius Wolff. The law states that bones will adapt in response to the load put on them.
"Following evolutionary theory, we inherit an anatomical template from our ancestor and adjust it slightly," Monk said.
Over time, thinner parts of these bones have thickened, leaving less room for ligaments and nerves to pass across joints. It is that crowding that often leads to pain. And, all things remaining the same, it is likely to continue and get worse.
"The species that survive are those that are best adapted to their environment," Monk said. (deleted sentence) And anticipating those adaptions could just give our species the edge to survive another millennia.
They found that the modern design of joint replacements won't work in the future.
"We have performed virtual surgery on the models," Monk said. "And it is clear that certain urgent changes are required to make the designs reflect the anatomical design constraints which are evolving now and will be particularly important in the not too distant future."
Examining the role of evolution on medical treatments also raises, for Monk, the reciprocal question. Does the medical treatment affect evolution?
"The species that survive are those that are best adapted to their environment," Monk said. "So the current joint shapes are those that are best adapted."
And anticipating those adaptions could just give our species the edge to survive another millennia.
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