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The Future of Prosthetics and Artificial Intelligence (AI)

April 19, 2024
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Written by Lee Martyniak, Chartered Legal Executive, 

The history of prosthetics 

Prosthetics have been around for thousands of years, as humans have sought to replace parts of the body which have unfortunately been lost due to amputation.  

Prosthetics began as very basic additions to enable the human body to function. In more recent times, they have become more and more advanced. 

The oldest known prosthetic was an artificial toe from Ancient Egypt, known as the Greville Chester Great Toe. This was made of wood and leather. The big toe is very important for balance, but it is thought that this particular toe was more as a result of cultural importance and the wearing of sandals. 

One of the earliest examples of a prosthetic hand was in 77AD when the Roman General, Marcus Sergius lost his right hand. As a soldier he needed to be able to hold a sword and a shield. His hand was replaced with a right hand of iron tied to his arm and he continued in battle. Iron hands continued to be commonly used up until the Middle Ages. Not just a creation for pirate stories, hook hands and wooden legs were also common. However, prosthetics were unfortunately generally only for the wealthy and the poor often went without. Then came hinged joints which allowed arms and legs to bend but by and large, progression in prosthetics has been extremely slow until fairly recent history.  

In the 1970s, Ysidro Martinez made a breakthrough with regards to leg prostheses. He produced the first leg which didn’t try to replicate the motions of the human body. As a result, he was able to reduce friction and relieve pressure for amputees. 

Modern day prosthetics 

In the early 1990s Blatchford developed a leg which had a computer which improved the symmetry of the user’s gait with a wide range of walking speeds. This allowed amputees to walk more confidently and also in a more energy efficient way. 

Over the last 10 years, artificial limbs have generally become more comfortable, user friendly and lifelike. An essential aspect of the prosthesis is the quality of the interface between the amputee’s stump and the prosthesis. The socket determines how comfortable it is when being worn and the person’s ability to control the limb. Over recent years the connection between the stump and the socket has improved greatly. 

Future advancements are likely to depend on the demands of the user, advancements in engineering and funding. The advancements over the last 10 to 20 years have been driven to a large extent by the amputee’s demands. At the present time, a person with a mid-calf amputation with a modern prosthesis, should be able to engage in most daily activities as well as sports. 

Now, sensors in the ankle and shin can monitor the position of the leg continuously whilst the amputee is walking. Microprocessors inside the knee pick up the data and the hydraulic resistance is adjusted, altering the knee stiffness throughout the movement. This makes it so much easier for amputees to walk on uneven, sloping ground or negotiate stairs. Unfortunately, these types of prosthetics cost around four times as much as a prosthetic with a mechanical knee, which means it could be too expensive for many people. 

The role of Artificial Intelligence (AI) in prosthetics 

We are currently at the stage where AI is quickly making its way into our everyday lives, whether it be how we shop or how we choose to listen to music. It is an extremely exciting time for technological advancement. But how does AI work in relation to prosthetics? 

AI is now also reducing the gap between a biological limb and a prosthetic one. This gap will reduce further in the coming years as technology advances further. 

Modern day prosthetics are now simpler and lighter thanks to advancements in technology. They are also much more customisable. Myoelectric prostheses are one of the most common types of these modern limbs and they rely on electromyography (EMG) signals from the residual limb muscles for control. The clever way in which this is done is by putting sensors on the skin of the muscles on the residual limb. When a person contracts the muscles, the movement is converted to electric signals which send commands to control the movement of the prosthesis. 

With regards to a leg prosthesis, the leg uses sensors on the residual hip muscle to determine the user’s intended movement and then uses AI to bend the prosthetic knee and adjust the swing duration accordingly. The leg can also adapt to a user’s specific stride patter leading to easier and more natural movement. 

What can we expect for the future of prosthetics? 

Will we ever reach a point where there will be no substantial difference between a biological limb and a prosthetic limb? Currently we are quite some way off this. Modern prosthetics still have speed delays, limited dexterity, and functionality, making their operation clumsier than a biological limb. Users of myoelectric limbs can often find them difficult to control and this remains challenging.  

A peripheral nerve interface is a more efficient replacement for EMG controlled limbs. Instead of relying on EMG sensors which are placed over the skin of the residual limb, this control method relies on implanted electrodes to read signals directly from the nerves. Researchers from the University of Minnesota have developed a new cutting-edge way to decode the signals using an AI system. In order to train the AI system, the user wears a data glove on their existing hand and the performs repeated hand movement on this arm and the amputated arm. As this is done the data glove records the intended movement while the peripheral nerve interface records nerve signals on the missing arm. 

In this way, the AI system learns to recognise the patterns of nerve signals and relate them to specific hand movements. The AI decoder can recognise and make several movements at the same time such as pinching which involves movement of the thumb and forefinger.   

In terms of future technological developments, it is believed that fully sensory feedback is a possibility which will enable users to feel the object they are holding or touching. Research is already underway to look at the best ways to connect prosthetics with the somatosensory system. It seems there are very exciting times ahead in this area over the next decade. 

Sources: 
The evolution of functional hand replacement: From iron prostheses to hand transplantation – PMC (nih.gov)  
National library of medicine   
https://www.Bionicsinstitute.org 
https://www.Frontiersin.org 
https://www.wevolver.com 

 

 

 

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