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The prosthetic hand: The problem and design

A case study of the prosthetic hand. Watch Gordon Wallace discuss the medical need/problem and the material selection.
Let us remember that the four critical steps in a 3D printing project involve defining the need, creating the design, selecting the material, and selecting the best approach for 3D printing.
I’d like to introduce you to a colleague of mine, Professor Peter Choong from Saint Vincent’s Hospital in Melbourne. Peter, can you tell us about the need for advanced prosthetics. The area which I work in deals with people who for, some unfortunate reason, whether by injury or by tumours, lose part of their limbs. And these parts of the limbs may involve joints, or muscles, or the entire bone section itself. The role of prosthesis really are to rebuild the gaps created by these injuries or growth. And with the advancing science, we can now look at different ways of shaping bones and joints ideally to match the patient’s.
There’s been a lot of talk in the 3D printing world around developing 3D printed prosthetic hands. Do you see a real opportunity to meet a clinical need there? Absolutely. We have many people who suffer accidents in the workplace or in arenas of war, for example. And for them, the capacity to rebuild them with a limb that is able to function, to allow grasp, pointing, allow them to pick things up, would be a tremendous boon for them, which otherwise which they would lose the use of one half of this function. And is the advent of 3D printing and the fact that it’s moving into the clinical environment really giving confidence that we can deliver prosthetics like that?
Well, 3D printing is upon us. We see it every day. And it really has matured and become far more sophisticated than we initially thought. What this means is it provides us with an opportunity not only to be very specific of how we can build something, but it allows us to make what we’re trying to build as close to the real thing as is possible. And I think, as 3D printing continues to evolve, of course, the hands will become more and more sophisticated, and that’s something that we can talk about later on. Absolutely.
Not only can we build the parts to make a hand, we can build the connections that we need to hook what is an artificial and manufactured item with the person’s own nerves and muscles and bone.
So having identified the need in prosthetics, the next critical step is to consider design. And the clinician, of course, is very much involved in that design process. Peter, how would that evolve in terms of an application involving prosthetics? Form follows function, and it’s really important to know which part of the limb is affected, because every part of the limb has its own job to do. So for example, we need strength in the bones of the forearm or the digits of the hand, but we need flexibility in the joints. We need power in whatever artificial muscle we’re trying to create to drive the function of grasp or holding. So each person will also differ from the next.
And so we have to cater to people’s inherent strengths, the specific functions that they’ve lost from which we’re trying to build. This is a very important step because this is where clinicians and scientists come together to translate what knowledge we have of the basic science of what we’re trying to do with the actual needs of the patient, as well as how it is implanted into patients. If I can give an example, syncing or matching up artificial 3D printed bone with the patient’s own bone has to first to be secured against the patient’s own bone to allow the patient’s bone to grow into the device and hold onto it.
How you actually design that will depend on where the surgeon makes their cut. Where the surgeon makes their cut depends on how strong or how large the implant might be. So immediately you can see how there needs to be a very close cooperation between the design side and the implantation side, between research, researcher, and clinician. And so the ability to personalise using 3D printing is a very powerful element. It brings new dimensions to the whole area of prosthetic design.
How technology has changed

Historical background

To appreciate how far the technology has advanced we must consider the ancient Egyptians. In ancient Egypt, people with missing body parts were terrified their disability would carry over to the next world. They would be entombed with artificial replacement parts to ensure their body was restored as whole in the afterlife.
According to the amputee-coalition, one of the oldest artificial legs on record dates back to approximately 300 B.C. This ‘prosthetic’ was found to be made of a combination of bronze, iron and wood.
In modern times, in the United States alone, there are over two million people currently alive who have lost a limb. Work accidents, war injuries, and illness tend to be the biggest contributors these statistics. Over recent years, 3D printing has offered an lighter, robust solution to producing usable prosthetics.

Conversation starter

  • See if you can find some more historical developments that have helped bring us to our current developments.
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Bioprinting: 3D Printing Body Parts

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