The future of prosthetics is here thanks to Artificial Intelligence and bionic feedback

Research and development always have interesting and unique topics to explore. Unfortunately, it typically takes years before users get to benefit from the resulting new or updated products. That being said, there are many exciting advances in the field of prosthetics. The aim of prosthetics is always to replace the missing limbs to allow amputees to control the device more precisely, and to lead an active, self-determined life. REHACARE.com asked prosthetic manufacturers and experts about the latest medical and technical research in laboratories and discovered how prostheses quite literally learn from the user.

"A well-fitting prosthetic socket is the nuts and bolts of the prosthesis. In fact, it’s the most important item in the toolbox. If it has the perfect fit and doesn't hurt, you could attach a wooden leg underneath it and I could still walk with it," says Kim Cremer. The Communications and Social Media Manager at apt Prothesen knows what he's talking about. He has learned that "The way to the prosthetic limb with the best fit is not a sprint". The same applies to research, which has come a long way since offering wearers a wooden pegleg as an artificial limb. Manufacturers also continue to improve their devices and product selection. The latest research is exploring a promising alternative to prosthetic sockets.

In 1999, D.Eng. Hans Grundei was the first to insert an osseointegrated prosthetic implant into a young patient. The unique device eliminates the need for a prosthetic socket and is based on the ability of human bone cells to attach to a metal surface. Dr. Grundei used osseointegration to permanently anchor a stem to the residual femur bone to attach the implant – the so-called stem adapted Endo-Exo prosthesis care concept according to Dr. Grundei. Aside from providing greater stability and control, the advantages of this endo-stem include less pain or skin damage, which is a common occurrence where the stem joins the residual limb (stump). What’s more, the prosthetic implant feels more like a part of the person’s body. Since then, over 1,000 patients have received the treatment worldwide.

So-called Targeted Muscle Reinnervation (TMR) for the upper extremities is an approach that provides more intuitive control and a natural feel. Today’s myoelectric prostheses use the existing muscles in the residual limb, and work by tensing or relaxing the muscles. Two sensors embedded in the prosthetic socket measure these muscle activities and convert them into impulses that control the motors, which is followed by the movement.

TMR takes residual nerve endings from the stump and relocates them to muscles that are still intact – the chest muscles, for example. They subsequently assume the function of the muscles from which the nerves originally came. This allows amputees to move their prosthetic arm by simply thinking what movements they wish to accomplish as the nerves pass the signal on to the new targeted muscles to prompt them to contract. The muscle contraction enables more intuitive and natural control that is more precise. After TMR surgery, there are up to six electrodes compared to the usual two electrodes to control a myoelectric prosthesis. This also supports a more natural prosthesis control because it considerably increases the information density. This approach and the rerouting to new muscle targets can lead to a further reduction of phantom pain. However, patients need patience and perseverance as the entire TMR process from surgery to completion can take up to two years. The method is especially effective following an amputation of the upper arm. Combined with osseointegration, TMR could be the future of artificial limbs.

Today, the signal transmission from patient to the prosthetic limb has its limitations. At the same time, robotic limbs are already more advanced in function than the human body's own limbs. Osseointegration - combined with an optimized neural reconnection thanks to TMR - could solve these signal transmission issues.

Professor Oskar C. Aszmann has explored TMR since 2006. He is the Director of the Christian Doppler Laboratory for Restoration of Extremity Function and Rehabilitation and Deputy Director of the Department of Surgery, Division of Plastic & Reconstructive Surgery at the Medical University of Vienna. Last year, four test subjects received the world's first fully integrated ready-to-use bionic arm prosthesis. This "plug-and-play" state-of-the-art prosthetic uses osseointegration. Even the cables for signal transmission are included directly in the bone implant. The prosthesis allows for bidirectional communication, receiving signals from the body and giving feedback - in case of resistance changes, for example. This enables more precise control of the prosthetic device and feels more natural thanks to sensory feedback. "There is a clear goal: a prosthetic and orthotic medical device that the user ideally perceives 'as a real body part' – one that feels like an extension of your own body, one that the user calls 'a part of me'", explains Dr. Andreas Goppelt, Chief Technology Officer at Ottobock. The company has collaborated closely with Aszmann for the past 15 years. "In fact, 'prosthetics that can feel' are a fascinating topic that will shape the future," says Goppelt. But the key word here is "future". Aside from research, standardization is one of today’s goals to ensure that health insurance providers will pay for this particular care service in the future.

The latest prosthetic options have improved as users benefit from artificial intelligence (AI): enter MyoPlus pattern recognition from Ottobock. The system autonomously recognizes the movement pattern for a specific grip and performs it automatically. Thanks to pattern recognition, users no longer must contract their muscles or take manual action to switch back and forth between functions of their artificial body part. Electrodes in the prosthesis measure the movement patterns of muscles for specific motions and assign them to certain hand movements or grips such as reaching for the water bottle. The next time the amputee reaches for the water bottle, the prosthesis recognizes the associated movement pattern and automatically performs the correct grip or wrist rotation. An app allows users to visualize the movement patterns and embark on more targeted training. The muscle movements for specific grips are very similar with little variation. The more articulate the movement is, the greater the precision of the prosthesis control device becomes.

Due to the key function they are designed to replace and the complexity of the human hand, the technology of prosthetic hands is very intricate in efforts to replicate hand functionality as accurately as possible. Manufacturers like Össur make continuous improvements and big investments in development to bring ever-better prosthetic devices to market.

According to the company, the i-Limb® Quantum is the most versatile myoelectric hand currently available on the market. The device features five independently motorized fingers and powered thumb rotation that facilitates maximum movement. This is especially beneficial when it comes to holding eating utensils, or doing any activity that requires more dexterity, coordination, and finesse. The i-Limb® Quantum has 36 different grip options for (nearly) any daily activity. Muscle control allows users to not only activate the different grips but also determine the grip strength that should be applied to an object. What’s more, the prosthetic device also has gesture control, which enables wearers to change grips with a simple gesture. Users can also customize grips via an app.

Thanks to sensors, lower limb prosthetics recognize both the user’s intent and depth perception via muscle activity. Microprocessors facilitate direction changes in real time and adjustments to changing terrains and surfaces such as slopes or stairs. Apps also play a role in this setting as they allow users to switch back and forth between modes to meet their everyday needs. Jogging, cycling, or swimming are no longer an issue with these innovative tools.

Güngör Kara, Chief Digital Officer (CDO) of Ottobock is certain that "digital solutions will increasingly take center stage - guided, measured, controlled, and autonomously optimized by artificial intelligence. This creates new opportunities for improvement in prosthetic comfort and care for users. This is clearly an accelerating trend. In the coming years, we will see a gradual holistic integration of more and more AI solutions."

High-tech prosthetics are no longer just accessible to top athletes or Paralympians. People with low levels of physical activity can also enjoy modern technology that enables them to walk securely and with as much confidence as possible. Examples include the Kenevo prosthetic knee by Ottobock or the RHEO KNEE® XC from Össur. Both adapt to the wearer’s specific needs and abilities - whether the amputee still needs to learn how to use the prosthetic device during rehabilitation or whether the person becomes less mobile as he/she gets older. There is a reason the Icelandic company advocates "Life Without Limitations". Its mission is to find the best solution for every mobility level.

"The latest prosthetic technologies we use today provide much better support than prostheses in the past and make the wearer’s life easier," attests Tobias Werner, a certified orthopedic technician at apt Prothesen. "What has not changed is the need for wearers to know how the prosthesis works and to learn how to control it." The right rehabilitation program and open communication between wearers and technicians and the responsible physicians and physical therapists are crucial in this setting. After all, the high-tech product might not be the right choice for everyone. Ideally, users should leverage the expertise of their healthcare team, but keep in mind that ultimately only they know the real challenges they must be able to face in everyday life. Ultimately, the wearer is the one who must master these tasks. Communication is key to ensure that the amputee receives the prosthesis that best fits his/her unique needs. Werner agrees and confirms that "the more information technicians get, the more they can utilize their skill and expertise to achieve the best result for the individual wearer." That is why the way to the prosthetic limb with the best fit is not a sprint and also hinges on great teamwork. Technology alone is not the solution for everything.