The earliest known examples of a human prosthesis found to date is two artificial toes dating back to Ancient Egypt (before 600BC). Since then, archeologists have found a wealth of historical prostheses, ranging from the famous Roman Capula Leg to Gotz von Berlichingen’s Iron arm. The archeological evidence shows that prosthetic limbs have been designed and used continuously across the 6000 years of recorded history. The most iconic prosthesis of them all to my own mind, is the prosthetic hook. Featured in movie classics like Captain Hook, the prosthetic hook was a revolutionary prosthesis. But in the 109 years since its invention, how far has the industry developed and what are the options for the limb difference community today?
The split-hook design, first patented by David W. Dorrance in 1912, the hook enabled amputees to hold and squeeze objects between the split hooks (Bowers). Coupled with the invention of the Bowden cable, this gave rise to body-powered prostheses. A body-powered prosthesis allowed the user to operate the terminal device – in this case a two-pronged hook – mechanically and independently, by changing the tension in a cable via shoulder and body movements (Zuo and Olson, 2014). The prosthetic hook is still an option offered to this day and continues to offer those with limb differences robust and relatively affordable, body-powered functions. Rapid advances in technology and robotics however, have drastically increased the functionality options available in modern prostheses options.
Here at Open Bionics, we use modern technology to develop clinically approved medical devices. Our first product is the life-changing Hero Arm, which uses myoelectric sensors to detect underlying muscular contractions generated from specific muscle groups in the residual limb. These are then amplified and converted into intuitive and proportional bionic hand movements, a far cry from the simple pulley systems of the original prosthetic hook. This system allows the user to control grip strength and finger movement to complete everyday tasks independently.
Myoelectrics allows the user to control the prosthesis without using their remaining limb, making the completion of tasks requiring two hands infinitely easier. Progress in robotics, programming and the miniaturisation of technology allows for more data to be stored in a smaller space. The Hero Arm, for example, has a number of preset hand movements built in and can swap seamlessly between them. Depending on the task at hand (pun intended) the user wants to complete, the functionality of the Hero Arm can be tailored to individual tasks by choosing the right grip type for the job. Instead of having one tool for the job and working around it like the hook, modern prosthetic arms offer a number of different tools and functions to help support the user in their activity.
The Hero Arm represents a paradigm shift away from purely functional prosthetic design. Whereas the design of the prosthetic hook is solely dominated by the function it needs to carry out, the Hero Arm gives the user control of not only its vastly superior functionality, but the way it looks and how it makes people feel.
Technology and manufacturing techniques have also come a long way since the beginning of the 20th century. 3D printing plays a large role in the look and feel of modern prostheses options. Here at Open Bionics, we use 3D printing to print parts of the Hero Arm. It makes the bionic arm more lightweight than the prosthetic hook, and let’s be honest, it looks super cool!
Another important factor – 3D printing techniques make prosthetic limbs like the Hero Arm much more financially accessible due to the lower production costs and parts can easily be replicated to create much more customisable options for a prosthesis.
It’s not only about the prosthesis itself, 3D scanning has been a major part of making the process of getting a prosthesis you want quicker and more repeatable. 3D scanning means that prosthetists can quickly create accurate computer models of the user’s residual limb and design the prosthesis to fit perfectly. Generally, the user’s residual limb interfaces with a socket. The socket is what keeps the prosthetic limb on the arm and in the case of myoelectric prosthesis, it’s where the muscle signals are read. At Open Bionics, we have developed 3D printable sockets successfully combining 3D printing and scanning to reduce the fitting time, manufacturing time and overall costs for our users. The result of this is that users as young as eight years old have been able to access viable prosthetic limbs.
Previous prostheses, the hook included, have been predominantly designed with ‘function over form’ in mind. This is completely understandable of course, the main priority of any prosthesis is to perform as intended, rather than to look good. The hook, for example, does not replicate the aesthetics of the human hand, but has been designed to fit its particular purpose, i.e., picking up objects. But considering the technological advancements discussed previously, there is more and more scope for taking into account the ‘form’ of a modern prosthesis.
I have described how myoelectrics replicates the movement of human limbs through electrical signals from the user’s muscles. What this also means is that the terminal device of a prosthesis can look and move like the limb it replaces. This helps modern prosthesis feel and move like a normal limb, but why does it need to look like one? Some prosthetics companies choose to use muted skin tones to try and hide the prosthetic limb away, but at Open Bionics, we’ve taken a different approach. We embrace differences. The Hero Arm is designed to stand out. Using 3D printed technology, we can print interchangeable covers in a variety of amazing colours and textures and even ones designed to replicate your favourite film and video game characters. This gives the user control of their prosthesis – they can make it look however they want and show off their personality through the colour combinations and designs.
The Hero Arm represents a paradigm shift away from purely functional prosthesis design. Whereas the design of the prosthetic hook is solely dominated by the function it needs to carry out, the Hero Arm gives the user control of not only its vastly superior functionality, but the way it looks and how it makes people feel. What modern prostheses have done is allow the user to fit in, but what the Hero Arm does is help them to stand out. From what I have seen at Open Bionics, people are embracing this change of perspective.
My job at Open Bionics is to build ‘Special Covers’ (this is what we call the Iron Man, BB8, R2-D2, Frozen, DesuDeus Ex, Metal Gear Solid and Handala covers). In this role, I see first-hand how important bionic prostheses can be. When I meet our users, it is always amazing to see their enthusiasm for these covers and for how much choice the Hero Arm gives them. From the conversations I have had with our Bionic Squad, and the amazing videos I’ve seen of satisfied customers using their new bionic arms, it seems to me like there is a change of perspective when it comes to the prosthetics industry. In my opinion, this change is that people no longer see prosthetic arms as merely tools, they see them as extensions of their personalities and a way to celebrate their differences.
Looking back at the historical records of prostheses, it’s clear that they have, and continue, to play a major role in changing lives. The prosthetic hook has been a key player in this, giving users the ability to complete everyday tasks and using the concept of a body-powered limb to increase functionality and give users independence. These tools were perfect for the job, and still have an important role to play, but with the technological advancements, the limb difference community can now have more options. Daniel Melville, one of our Bionic Squad members said it best:
“When I wear the Hero Arm I feel damn awesome because peoples eyes light up when they see the arm and they come over to talk to me, to ask me how cool it looks and about how it works, which of course I oblige with a great big smile on my face.”
A prosthesis is no longer just a tool, it’s a conversation starter, a fashion statement, a way to express yourself, and yes a fully functioning arm. In every way the prosthetics industry has come a long way from the prosthetic hook, and everyone here at Open Bionics is excited to go even further.
Author – Christian Leggatt, Production Technician at Open Bionics