All around the world, millions of people live with disability. But for many of them technology can offer a better future. One of the most visible ways in which technology can improve people’s lives is through prosthetic limbs. This field is just one exciting example of how mechanical engineering, computer and medical science can come together to deliver incredible medical advances. There is still a lot of work to be done, however, and the world needs ambitious, passionate and dedicated young scientists and engineers to help make the dream of a world without disability a reality.
In the United States alone, each year, 185,000 people have a limb amputated. There can be many reasons why someone loses a limb, including vascular disease, cancer and birth defects, as well as more obvious causes like road traffic accidents and violence. Amputees are most common in conflict zones and countries with a large number of landmines and unexploded ordinance: there are an estimated 110 million land-mines in 64 countries, causing 800 deaths and thousands of life-changing injuries each month. At least 30,000 Syrians have lost limbs in the country’s civil war since 2011 in this decade’s bloodiest conflict.
While the materials used in traditional prosthetics have improved steadily in recent years, none of these come close to restoring the body function of a human limb. However, through a combination of robotics, software and neuroscience, researchers are bringing us closer to a future without disability, bringing hope to millions.
Mechanical arms which could flex and grip objects have been around for some years now, however, they are still very limited in what they can do, and, controlled manually, don’t come anything close to replacing a human limb. For a prosthetic limb to be truly life-like in the way it’s controlled and functions, researchers need to find a way of making artificial limbs which respond to the human nervous system; or, to put it another way, are controlled by the mind, just like the person’s original limb.
The John Hopkins Applied Physics Laboratory (JHAPL) has been conducting some of the most advanced prosthetics research in the world, funded by the US government’s Defence Advanced Research Projects Agency (DARPA). Johnny Matheny, who lost his left arm to cancer in 2008, became the first person ever to have a prosthesis grafted directly to his skeleton. You can see his arm in action in this incredible video. However, Johnny Matheny isn’t the only test subject: Les Baugh, who lost both arms at the shoulder as a teenager, is helping researchers design full-arm prosthetic limbs, also controlled by his brain via his remaining muscle nerves, as seen here.
However, being able to articulate an artificial limb with the human mind is only half the story. To be a real replacement for a human limb, the user also needs to be able to feel. Scientists are now working on achieving just that, allowing people to feel pressure, texture and temperature with their robotic limbs. The first steps towards this have already been taken elsewhere: In 2014, European scientists announced they had wired pressure sensors in an artificial hand to sensory nerves in Danish amputee Dennis Sørensen’s upper arm, allowing him to feel whether objects are hard or soft.
These limbs function via a sophisticated combination of neuroscience, surgery, software and robotics. At the JHAPL, surgeons had to rearrange the nerves in the end of Johnny’s arm, and these were then mapped to specific functions in the prosthetic limb. Sensors strapped over Johnny’s upper arm detect the electrical activity generated by his nerve-endings and communicate these via Bluetooth with the limb, allowing it to react and for Johnny to control it. Johnny’s arm already has pressure and temperature sensors, but he’ll require further surgery to allow the limb to feedback to him. The researchers at the JHAPL are also working to improve sensory implants so they can replace these Bluetooth sensor bands. Once developed, tiny sensors will be able to be implanted directly into the muscles to allow greater dexterity and a finer level of control. Elsewhere, researchers have been developing mind controlled leg prosthetics too. In 2012, Zac Vawter climbed all 103 flights of stairs in Chicago’s Willis Tower using a mind-controlled prosthetic leg.
By being able to link technology to the human nervous system, scientists may be able to develop mobility devices for even more profoundly disabled people. Robotic exoskeletons are currently being developed for a range of applications, one of which is to help people with spinal injuries walk. While some of these, like SuitX’s ‘Phoenix’ robotic legs are only able to be controlled with buttons on the system’s associated crutches, researchers are working on developing exoskeletons which people with lower body paralysis can move with their minds. Perhaps with advances in neurologically linked robotics, one day even the completely paralysed will be able to move fully again with the assistance of a full-body exoskeleton.
These advanced prosthetics are still experimental, and they stay in the lab when their test-subjects go home. Even when these technologies do become commercial available, which is still years away, there can be little doubt that their cost will be well beyond the reach of many ordinary people, particularly in developing countries, for decades. Fortunately, however, even regular prosthetics today represent a huge improvement over those available throughout the 20th century, and new technologies are making prosthetic limbs cheaper and more readily available so that they can transform many more lives.
The World Health Organisation estimates about 30 million people in the world need prosthetic limbs or other mobility devices, but less than 20% have access to them. However, 3D printing is starting to allow bespoke prosthetics to be produced quicker and at less cost for people in developing countries. Although the technology still has some way to go, it could allow the limited number of prosthetic specialists in poor countries to be able to help patient’s much quicker, ultimately allowing more people to get the limbs that they need.
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