There are few things as traumatic or life-changing as losing a limb, especially when that limb is an arm or hand. Apart from our intelligence, humans have become amazing tool users thanks largely to our upright walking habits and fine motor skills.
You don’t really realize how much your hands do for you until you lose one; when even tying your own shoes becomes a serious challenge. So it’s no wonder that for thousands of years humans have created prosthetic limbs to return some of the functionality lost when a hand or arm is gone forever.
Tis’ But a Scratch
For most of history leading up to the Renaissance, upper-body prostheses were either very basic hooks or purely cosmetic. It wasn’t until after the Dark Ages that scientists and artisans began making prosthetics that could be both functional and attractive. There are records from the 1500s indicating sophisticated iron hands that could be set to various grips with the remaining hand. The prosthesis could also be moved with a set of springs and leather straps. In Asia there are records from the 1500s of prosthetics advanced enough so that a person could do things like open a purse or sign their name.
The mechanical complexity of prosthetic limbs has increased steadily over the years and today lower-body prostheses are mechanically so advanced that they can completely restore natural gait – well enough to fool onlookers into believing a leg is natural.
Power to the People
Today we have so much more to build prosthetics with than just springs and levers. We have small yet powerful batteries, tiny motors, advanced microprocessors, and a whole host of other technologies that promise the possibility of a robotic prosthesis that will meet or even exceed the abilities of a natural limb.
A lot of time and money has gone into creating ever more sophisticated arms for amputees. Unsurprisingly, much of that funding comes from military sources. After all, once you’ve spent hundreds of thousands of dollars training a soldier, it would be a waste to lose all that skill thanks to a missing limb.
It’s not just the military that’s doing their part for amputees either, there are many independent groups who are working on different approaches to solve the problem. New manufacturing technologies such as 3D-printing are also driving down the cost of prototyping, making it possible to provide customized limbs at a much lower cost.
I guess you could say there’s a bit of an arms race going on.
The Best of the Best Prosthetics
Here I want to highlight three of the most impressive prosthetic limb projects out there. These are the arms I think hold the greatest promise and will lay the groundwork for true restorative prosthetics; perhaps something so advanced that you’ll end up even better off than before.
The DARPA Luke Arm
DARPA is an organization that we have to thank for many modern technologies, not least of which is the very internet you’re reading this on right now. A few years ago DARPA put out a set of requirements for a prosthetic arm that would allow veterans who had lost their natural limbs to get back as much of what they lost as possible. Of course, the idea was always to make the technology available to everyone – in fact the product will be sold to the public as well.
Picking up this challenge was famed inventor Dean Kamen. That’s a name you probably know in relation to the Segway, which Dean invented. The prosthetic limb he proposed was called the “Luke”. The name comes from Luke Skywalker, a character from the Star Wars movies. In The Empire Strikes Back, Luke loses his hand and part of his forearm. He receives a replacement that’s indistinguishable from a human one.
That’s the ultimate design goal for the Luke arm, although DEKA and DARPA have a long way to go before they hit the Star Wars standard.
Technologically, the Luke arm is really state of the art when it comes to powered arm prostheses. The system is incredibly modular and can be configured to replace the arm from the shoulder, the elbow, or just the wrist and hand. In terms of control options I don’t think there’s a more flexible solution out there. There are input systems that make use of wireless sensors, often fitted to the tops of shoes. Various pressure sensors, transducers, and other similar devices can be used to control the arm. There are also projects to directly connect the Luke arm to the nervous system, and even an option to use the off-the-shelf myo gesture control band.
There’s a lot more to say about the DEKA Luke arm, but that could literally take up an entire book. The project to allow arms like these to actually let you feel is the most mind-blowing.
The Bebionic Hand
Although the DEKA arm will be available for sale to the public, it’s going to be insanely expensive at first. Which is where the Bebionic hand comes in. Although the Bebionic is not nearly as sophisticated or advanced as the DEKA-DARPA Luke arm, it’s probably the most advanced arm you can actually hope to afford. While the Luke has been in development, this hand has been helping amputees all over the world improve their quality of life.
While the Luke arm has all sorts of interface options, even experimental direct nerve connections, the Bebionic is plainly a myoelectric device. What does that mean? It means that it measures electrical signals from residual muscles and interprets them into hand movements. That’s helped by the fact that many of the muscles that actually operate the fingers are in the forearm.
Before I describe what it is the Bebionic can actually do, keep in mind what the price difference is between this and the Luke arm. There’s actually no official pricing for the Luke, but estimates put it at a cool 100,000 dollars. It’s not clear of that’s for the hand or the whole modular arm.
The Bebionic, on the other hand (pun intended), comes in at a much more reasonable $11,000. That still seems like a lot, but it’s in line with the price of unpowered prostheses and is a number that would make most medical insurance companies much happier.
The Bebionic has individual motors for each finger and constant digital monitoring of their position make for a strikingly lifelike grip. Although you only have to “think” to open or close the hand’s grip, the actual grip pattern needs to be selected manually. There are 14 of these patterns that can make the hand do things like hold car keys or work a computer mouse. It only takes a second or two to prepare the hand for a particular job.
One of the things that really sets the Bebionic apart from older myoelectric limbs is the fact that its speed is proportional. This means that you can handle things like eggs or other fragile objects without crushing them like an out-of-control Terminator.
It’s not just a “dumb” hand either. It can wirelessly talk to software that lets you customize a whole bunch of things to suit your own style and preferences. More than that, it can actually detect when something is going to slip out of the hand, and adjust accordingly.
One of the issues that female amputees face is that limbs are sized for men; this makes them painful and uncomfortable to use. The DEKA arm I discussed above takes this into account also and is made of very light materials, but the Bebionic actually comes in two different versions. The Bebionic “Small” is sized for the ladies and provides all of the same features, just in a world-first, small form factor. Actress Angel Giuffria was the first person to officially receive one.
The Limbitless Arms
Just a few years ago, basic myoelectric arms and hands were revolutionary and outlandishly expensive. Today simple myoelectrics are much more affordable, but they are still not exactly cheap.
Even more problematic is the issue of prostheses for children. On the way to adulthood a child will need their prosthetic arm resized several times. That can drive the cost up to unreachable heights. This means many people have to wait until adulthood before getting a more advanced, and expensive, arm. The non-profit organization Limbitless has been creating solutions for this problem for quite a while. They leverage cheap off-the-shelf electronics and 3D-printing technology to create child-friendly arms.
Cheap as Chips
One of the myoelectric models costs only $350 and is the result of a university project to help a 6-year-old boy get an affordable prosthesis. Best of all, the group released their design so anyone with access to a 3D printer could make their own. There are also body-powered models that are given away for free, since printing the plastic parts is so inexpensive.
The project got a lot of great PR in 2015 when actor Robert Downey Jr. handed over to a young man a special Limbitless arm styled to look like the gauntlet from Iron Man, a film in which he starred.
The video got over 10 million views (and counting).
The Limbitless is not amazing because it does a lot of new things. In fact, it basically does what traditional myoelectric hands have done from the start – open and close. It’s revolutionary because it can do it for less money than ever before and democratizes powered prostheses. Even better, people are free to volunteer in various ways.
The quality of the arms means that they will last for a few years at a time, but even if individual parts break they can be remade and replaced very quickly. If you exclude the initial personal design and electronics, printing a new arm only costs $70. The internal components can be moved from smaller frames to larger frames as the child grows.
The initial creation of the arm is pretty fast too. The Limbitless team estimates that it takes 4-6 weeks to create a hand and 8-12 weeks to create an arm. The pricey part is getting the residual limb measured and then having a socket made.
Armed and Dangerous
There are many more amazing prosthetic arm and hand projects that I could talk about, but each of these three is the most amazing in its own way. If the connection between man and machine can be perfected it would be a ground-shaking achievement. There are even projects that seek to attach artificial limbs directly to the bone, and at least one Luke arm has been successfully attached in this way.
There is little doubt that artificial limbs such as this will eventually match the performance of healthy limbs. In some ways they are already outperforming our natural parts. Just ask any myoelectric hand owner who loves to show off the 360-degree rotation of their limb. It seems inevitable that one day these limbs will be better than what we’re born with. Which leaves an interesting question: Would YOU choose to trade in your limbs for artificial ones?