I have come across a lot of news lately on the various options there are for those people who are missing one or both of their hands. Most readers of this blog already appreciate what hands can do. But when I listen to the stories from people who, through surgery or prosthetic device, having regained manual function, the appreciation is tremendously elevated.
The simplest choice is a passive device which can appear remarkably lifelike, matching the skin tone and contours of the natural limb, while still providing some important functional abilities, such as pushing, balancing and supporting.
The next level of complexity uses technology similar to what was developed in the early twentieth century. Due to their reliability, durability, and relatively low cost, body powered devices are the most popular prostheses. They are controlled by a harness that captures an unrelated movement of the user’s body, such as a shrugging of the shoulders, and transfers this movement through a cable system to either a hand or hook.
Next in line are myoelectric prosthetics which use battery and electronic motors to function. It is custom made to fit and attach to the remaining limb. Once it is attached, the prosthetic uses electronic sensors to detect minute muscle, nerve, and EMG activity. The myoelectric artificial limb does not require any unwieldy straps or harnesses to function but the disadvantages are currently their weight and cost.
New social and technological developments are becoming part of this world as well. The Open Prosthetics Project is website initiative dedicated to the development and sharing of new prosthetic technology, funded and kept alive by the prosthetic community itself. Their motto is “Prosthetics shouldn’t cost an arm and a leg” (very clever!). There is a range of discussions from the practical to opinions on legal and financial issues and the validity of claims from various prosthetic manufacturers. I am slowly learning how the complex abilities of the natural hand are very hard to replicate.
3D printers are playing a role in prosthetic development. In 2011 Richard in South Africa had an accident where he cut off his fingers on his right hand. Straight out of hospital, Richard set to work in researching and developing a finger replacement for himself. While surfing the internet he discovered Ivan who had created a giant mechanical prop hand. Even though Ivan lived in Bellingham, Washington he was genuinely enthusiastic to join the project. Each owned a 3d printer so they could prototype the ideas they shared. Initially the final parts were made of CNC machined aluminum but now they can use the plastic shapes made from the 3d printers. They came up with a design that helped Richard along with others who heard of their work. To support what they were doing MakerBot donated two Replicator 2 3D printers. Learn more about their involvement on the MakerBot blog. The company Robohand, the fruition of their initial collaboration, has helped over 200 people.
Marine Corps Staff Sgt. James Sides is the first person to test a prosthetic robotic hand actuated by electrodes implanted in his forearm. The implantable myoelectric sensor system, or IMES, was developed by the California-based Alfred E. Mann Foundation with support from the Department of Defense. An recent article by the American Forces Press Service tells you more about about this project and other initiatives coming from military agencies. What was interesting to me was that Sides’ prosthetic uses six of the eight electrodes, and in the future they could tap into the extra two if they had a hand that would allow more activities, such as bending the wrist back and forth. There is still the need and potential for more development in the future.
Myoelectric prosthetics inevitably with become lighter, cheaper and more capable over time. Even now there are sensors built into the hand that can control the motors to handle even the most delicate of objects. As far as feedback to the brain through the nerves … well don’t get your hopes up. Wait a minute … maybe it is possible if you follow the work of a number of European researchers. This article and video done by The Telegraph gives a good overview. It is revolutionary that they were able to connect to nerve endings in this subject’s body. These are nerves that have been inactive for nine years since this 36-year-old amputee lost his left hand in an accident. It is exciting but the scientists say that development of a fully functional “bionic hand” is still some years away.
Gerwin Smit was a PhD fellow at a university in the Netherlands who wanted to take development in another direction. He learned more than 30% of people who get fitted for a prosthesis eventually stop using it. In some cases it is because of the weight or the effort to overcome friction inherent in devices that use cables. His idea was to make it much lighter with no motors or batteries and to eliminate the need of cables. Gerwin looked at airplanes and cars that use hydraulic cylinders for their brakes. Watch the TEDx talk and you will be impressed at what he came up with. On June 11, 2013, he was awarded a PhD at TU Delft for his work on the subject. I hope he can bring the idea out of the university setting and into the real world.
Hand transplantation takes us away completely from the prosthetic world. The first hand transplant to achieve prolonged success was directed by a team at the University of Louisville in 1999. The Louisville group went on to perform the first five hand transplants in the United States. As of March 2011, there have been a total of 70 hands transplanted on 52 patients around the world. There still remains problems of drug-related side effects, uncertain long-term outcome, the high costs of surgery, rehabilitation and immunosuppression. The woman is the picture had a double hand transplantation in September 2011. There were serious complications at first but over time her body adjusted. In this Jan, 2013 story done by ABC News it notes that Lindsay Ess has at least two more years of daily therapy ahead of her, but she said her situation has inspired her to want to help others with disabilities, including wounded veterans.
I have been hearing a number of testimonials from recipients of a prosthetic or of a transplantation. There is a common feeling of joy at finally accomplishing those tasks that we take for granted. To be honest I don’t often think how lucky I am when I brush my teeth or tie my laces. But I do think sometimes how nice it is to find time for tinkering down in the basement. So maybe that is where I will go right now.