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If you wanted a replacement arm or hand, the main options were a ‘cosmetic’ plastic limb with practically none of the hand’s functionality, or a mechanical hook mounted on a socket and operated by often uncomfortable straps around the body.
Now, however, there is a rapidly growing selection of shapes, sizes, colours and functionalities. The most advanced read nerve signals and translate them into movement, a field that is rapidly improving thanks to advanced computing techniques. A recent study from the University of Michigan, for example, used machine learning to boost the amplitude of nerve signals being received by implanted electrodes, giving amputees instantaneous control of a prosthetic hand.
Printing progress
Although such techniques hold huge promise for the future, the technology currently making the biggest contribution to accessible prosthetics is 3D printing. Combined with 3D scanning and an ‘outside the box’ approach to functionality, the technique is giving amputees devices that are perfectly suited for their needs.
Customisation and rapid build time mean it is easier for children to have multiple prosthetics as they grow up, and personalised aesthetics with inspiring designs help them quickly get used to their new arms. The small-scale manufacturing method is much more affordable than previous options, creating prosthetics costing in the order of hundreds – rather than thousands – of pounds.
3D printing also opens up prosthetic limb creation to online collaboration. The e-Nable community, for example, includes volunteers around the world who build free printed hands and arms for those who need them. Made up of engineers, medical professionals, other experts and people with a personal interest, the group collaborates to improve open-sourced printable designs. e-Nable members have reportedly built 7,000 devices for people in more than 100 countries.
The manufacturing technique is even making bionic technology accessible. The Hero Arm from Open Bionics is the first medically certified 3D-printed bionic arm. The battery-powered device uses sensors to detect internal muscle movements and control the hand, which is capable of lifting up to 8kg. Thanks to 3D printing and scanning, each one is custom built, providing the perfect fit with breathable and dynamic sockets.
‘Printed bone’
After revolutionising the accessibility of comfortable and practical prosthetics, 3D printing could now be utilised for even more advanced technology inside the body. Millions of people need bone-tissue reconstruction surgery every year owing to congenital bone defects, diseases or accidents. Patients receive harvested bone or titanium implants, neither of which are ideal solutions. Instead, Particle3D in Denmark hopes to provide a more efficient and cheaper alternative – ‘printed bone’.
The company uses a degradable ‘bio-ink’ of tricalcium phosphate and fatty acids that occur naturally in the body to build bone-like implants. The bio-ink is heated and extruded from a syringe onto a cooler stage before solidifying. The fatty acids are then burnt away and the powders fuse together to form contaminant-free and mechanically strong implants.
The technique lets the team replicate the natural porosity of bone and will enable them to precisely match patients’ anatomy when used surgically. Substances such as antibiotics could even be added to the implants for controlled release.
The porosity and natural materials even allow for bone ingrowth into the implants. Ultimately, the company says the biomaterials will degrade over time and “simultaneously remodel” into living bone.
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