Lending a Hand: the future of Prosthetics

by Futurist Kit Worzel

Two hundred years ago, a significant injury to an extremity meant you would lose it, and have to deal with a rudimentary prosthetic. Fifty years ago, the same injury might not cost you the limb, but if it did, you at least had the option of a prosthetic that gave back some functionality, and was designed with comfort in mind. Twenty years ago, the first microprocessor controlled prosthetic, the Intelligent Prosthesis knee, was developed and aided people to walk with a much more normal gait. Today, we have a wide variety of prostheses, ranging from tens to hundreds of thousands of dollars for the absolute top of the line models with microprocessors, programmed movements and even neural interfaces, to fifty dollar models made with 3-D printers that can be assembled, unskilled, in under three hours. I plan on showing you where we are now, and giving you insight not only to where we will be twenty years from now, but how it will affect those of us who don’t need replacement limbs.

Oscar Pistorius is a remarkable man. I’m not endorsing his recent actions, but he will be remembered for his run in the 2012 Olympic games, where Pistorius became the first amputee to not only run in the Olympics, but to qualify for the semi-finals. Keep in mind he’s been a double amputee since before he was a year old, so he probably never walked without mechanical aide. But just as remarkable as his determination in his sport is the technology that enabled him to run. In the lead-in to the 2012 Olympics, there was significant controversy as to whether or not to allow him to compete, because his running blades might have given him an unfair advantage. That was the moment when prosthesis first surpassed human limits, when they allowed a person to perform at a higher level than human. Now, the controversy around the blades was shut down, and while he performed well, he didn’t win, but he still showed that a man without legs below the knee could compete at an Olympic level, better than all but a tiny fraction of humanity. True, he is a world-class athlete without the blades, but it’s still a remarkable achievement in technology.

Running blades, for all the science involved, are essentially simple tools. Impeccably well designed, but still, all they do is propel someone faster. For an example of something sophisticated, let’s look to Claudia Mitchell. Claudia Mitchell lost her left arm in a motorcycle accident, and has volunteered with the Rehabilitation Institute of Chicago (RIC) to be the first woman, and the fourth person, to have a neural interface with a bionic arm. The arm has been wired to nerves in her chest that once were attached to her missing limb, and she can control the hand and arm much like a real one. There is a learning curve, and she misses her sense of touch, but this is an amazing leap. 

The arms produced by RIC are amazing, but not the best in the world. At least, not according to DARPA, who is funding several such projects. That award goes to the Luke arm created by DEKA in New Hampshire, led by Dean Kamen. Named after the protagonist from “Star Wars” who had his hand chopped off, the Luke arm not only has an electromyogram (EGM) electrode interface, but also force sensors to control grip. But DEKA decided that wasn’t enough, so they also included toe switches in the users shoes that wirelessly transmit signals, allowing for control of multiple joints simultaneously. This bionic arm passed FDA approval in May, and is currently the most sophisticated prosthetic in the world.

The Luke arm may be the most sophisticated bionic, but it doesn’t have the most sophisticated interface. That honor goes to Hector, the robot arm wired into the brain of Jan Scheuermann, a woman with spinocerebellar degeneration, a disease that has left her paralyzed below the neck for the past decade. Hector, her robot arm, is wired into the part of her motor cortex that controlled her right arm via a pair of tiny 96 pin electrodes. It took her three months to learn how to use the arm, but now she is capable of feeding herself, and can use the arm reflexively. Unfortunately, the arm lacks force feedback, so she doesn’t know how hard she is gripping something, and it requires a bulky set-up that can’t be removed from the lab at the University of Pittsburg Medical Center.

If you’re looking for something still reasonably high-tech that doesn’t require a massive support infrastructure, then i-Limb might be the choice for you. These bionic hands sync to your smartphone, and have 24 programmable grips and gestures available through their app.  Unlike the preceding two arms, they are readily commercially available, and apparently easy to use and set up. It’s not cheap, but it’s easier than getting into a DARPA test program, which is where the preceding limbs were invented.

But if you don’t have the $40,000 that an I-Limb starts at, there is still hope. Project Daniel is a maker-community group based in south Sudan, where local people are trained to make simple prosthetic limbs from 3-D printers for under $50. The plans are available online, so all you need is access to a 3-D printer, and you can build your own in about three hours (not including print time). This came about because of one young man in Sudan, called Daniel, who has both arms blown off during the war there. Local press grabbed his story, and it came to the attention of the creative geniuses at Not Impossible. They crowdsourced the problem of not only how to give this young man a prosthetic arm, but how to supply them to the entire region. And once the design was completed, Mick Ebeling made the trip to Sudan to set up what is believed to the be the world’s first 3-D printing prosthetic lab and training facility. We have to remember that the future is not just shiny glass and electronics. Sometimes, it’s bringing better quality of life to people far away.

The last bionic that I’ll mention for now is neither a limb nor an implant. It’s an exoframe, a powered frame that allows people to walk. Unlike the exoframe used by Ripley in the movie Aliens, this frame doesn’t lift heavy loads, or fight vicious xenomorphs. It allows people with lower-body paralysis to walk. A powered frame attaches to the body with Velcro straps, and the arms hold onto a pair of crutches, while the battery is on the back, supported by the device itself. As a replacement for a wheelchair, it’s incredibly innovative and freeing, but there are issues that are holding them back. First off, with a price tag of $130,000, they have to convince insurance agencies that it’s a medical necessity, or be restricted to the 1%. Secondly, many people in wheelchairs distain it for the slow speed, particularly in a time where wheelchair ramps and accessibility is at an all-time high. Lastly, it’s bulky and noticeable. All of this fades into the background for the testers, who are elated to be able to stand and walk again. EKSO , the company behind the frame, are aiming to slim it down enough so you could sit in business class wearing it. 

These technologies are amazing, but where will we be in twenty years? Let’s look at the obvious. Battery technology is improving massively. There is a serious push across several industries to get better batteries, not only longer lasting, but faster charging, smaller, and cooler. This will allow better life and smaller power sources for all of these devices (save Project Daniel, which is non-powered). Secondly, we have a better understanding of how the body and limbs work now, so we can build and engineer limbs that interface better with our bodies. And computing power is also increasing, giving us more options to integrate into limbs. Instead of 24, like the i-Limb, why not 240, or 24,000?

Prosthetic arms in 2034 will be fully integrated. The site of the injury will have a cap on the end, the flesh side connecting to nerves and keeping the muscles there healthy, while the other side will interface directly with the bionic. The arm will attach to and cover the cap, sticking to the limb with a combination of suction and non-irritating electrical adhesive, that can be turned off to remove it. The limb itself is a more powerful computer than either the one I am writing this on, or the one you are reading this with. It can accurately interpret the signals from the biological nerves in the arm through the cap, and translate them into accurate movements. The arm is as articulated as a flesh and blood arm, with silent servos moving the elbow, wrist and finger joints. Through a human kinetics study conducted in 2018, each possible movement of a standard arm (not including unusual characteristics such as being double jointed) was catalogued, and have been fed into the processor in this bionic. The covering of this particular model happens to be lime green today, changeable with the touch of a button, and able to upload different patterns, but a completely realistic covering is available, down to freckles, arm hair and warmth. While full feeling is still impossible, tiny electrodes embedded in the fingertips give greater than 80% of normal sensation, and the optional programming even allows the arm to feel an itch at random intervals. About the only thing the arm can’t do is heavy lifting, and that’s more a design of the socket, rather than the arm itself. For lifting anything greater than 15 kg, or about 30 lbs, a shoulder strap should be attached so the socket doesn’t come loose. 

Exoframes are no longer used for mobility enhancement, but instead for heavy labor. People with spinal injuries that can’t be regenerated have a cybernetic bypass installed, connecting the severed or damaged nerves to the healthy part of the spine. It takes a few months of physiotherapy to get used to, but at least one competition dancer has had the operation, and she still makes the finals. 

In fact, the best thing about these bionics are that they are only noticeable if you want them to be. Many people fail to realize that one of their co-workers has a bionic arm or leg, so natural and smooth have the movements become. 

But what good is this for the vast majority of the population who aren’t paralyzed, or not missing limbs? I’ll take that up in my next blog.