Bionic Prosthetics

For someone who has lost an extremity, any kind of prosthetic limb can make a huge difference — but having a bionic device fitted, giving the user an intuitive function, can be transformational.

Bionic prostheses are the pinnacle of the technological development of prosthetics. These are ultra-functional devices that allow, as far as possible, to restore the fine motility of hands and natural gait to a person. Previously, in one of the issues of Digital Health Interviews, we had the opportunity to speak to Dhruv Agrawal — CEO of Aether Biomedical, a rehabilitation robotics startup focused on building bionic limbs for upper limb amputees. It was founded on the premise of creating healthcare technology and robotics based on human-centered design. A culture focused on building the next generation of bionic devices, utilizing advanced bio-signal processing and software integration. Read more about how prosthetics can improve life and what changes in this technology await us in the near future in our material.

What Are Bionic Prosthetics?

Bionic prostheses are made for arms (elbows, hands, fingers) and legs (knee joints, ankle joints). A hand prosthesis can include one or two bionic elements: an elbow, and a hand with movable fingers. In amputations above the ankle, bionic nodes of the tibial joint are placed. They can perform up/down foot movements. If amputations are above the knee, a bionic knee joint can be fitted. In such cases, a bionic node is not made instead of the tibia joint in the prosthesis.

How Do Bionic Prosthetics Work?

To put it simply, bionic prostheses work from stump muscle signals. How does this happen? Sensors are installed in the stump receiver of the prosthesis where the signals from the muscles are the strongest. A person tenses the desired muscle on the stump, and the sensors respond to this impulse. The processor “decodes” the received signal through a special program, which records how many muscles presses correspond to which gesture. After that, the prosthesis performs a certain movement: it bends the knee, turns the hand, or squeezes the fingers.

In the bionic brush, each finger has a separate motor. Depending on the sequence of impulses, sequence, and strength, the fingers form a certain gesture.

Bionic prostheses are sensitive to external factors, such as water and dust. It always comes with a unique cover. It is not possible to use the prosthesis without it (such cases are not guaranteed).

What Can Be Done with Bionic Hand Prosthetics?

The bionic hand prosthesis restores mobility and fine motor skills. With its help, a person can pick up small objects, do manual work (handmade, write or cook), and take care of himself. The bionic elbow can bend or unbend the arm. The wrist (depending on the model) is capable of performing up to 36 gestures, combining impulses from only two muscles. Some models of bionic hand nodes can make turns and partial bends inward or outward.

Such prostheses are not recommended for heavy physical work or weight lifting of more than 60 kilograms. This can damage the mechanism or injure the stump. The bionic wrist has a compression force of 95 kilograms, but it is not designed for rough types of work. For example, difficult repairs, and work with a perforator are not desirable with these prostheses. There is a special nozzle for this.

Some bionic prostheses allow the removal of the mobile brush and screw a hook or other attachment into the same attachment. The hook has a large compression force and is designed for force actions.

What Can Be Done with Bionic Leg Prosthetics?

A bionic leg prosthesis can provide maximum (for a prosthesis) movement control. Thanks to the bionic ankle joint, the foot can bend up/down like a healthy leg. This helps the person feel safer and better control the prosthesis when they go up or down stairs or walk on uneven surfaces. The bionic knee can bend and extend.

The use of a bionic prosthesis makes it possible to make a person’s gait more natural. This reduces discomfort. A person gets less tired, and the lower backload is distributed evenly.

Wearing a bionic prosthesis reduces the risk of injury and occurrence of secondary injuries: scoliosis and other disorders of the spine and posture.

Pros of Bionic Prosthetics

A bionic prosthesis has the highest level of functionality. Hand prostheses give a person the ability not only to pick up an object but also to restore fine motor skills: fasten a button or pick up a pen. They are more convenient in everyday life.

Bionic leg prostheses make full-fledged walking possible. They allow you to preserve the movement that is characteristic of a person. With such prostheses, it is easier to overcome stairs and curbs.

On average, the lifetime of a bionic prosthesis is 4-5 years. It can be extended by sparing use. However, there is a risk that the prosthesis may become morally obsolete. Manufacturers give a 2-year warranty, each subsequent one can be purchased additionally.

A bionic prosthesis is, first of all, comfort in use and a technological solution to the problem.

Mobile Apps for Bionics

Prosthetic mobile apps allow clinicians to adjust their clients’ prostheses while on the move. These applications do not store PII (Personal Information) or PHI (Protected Health Information), they only use non-confidential data such as the reference, and alphanumeric serial number of the prosthetic limb components.

So, what features are possible in such applications?

• The ability to change or adjust prostheses’ settings remotely. This point is quite problematic for most companies providing bionic services: in order to better personalize the prosthesis, each time patient needs to personally contact the prosthetics center, which may be inconvenient due to the distance from the place of living. The special mobile app allows specialists to correct faults remotely;

• Creating lists of repetitive movements customized according to a person’s daily needs;

• A health check of the hand to make sure the prosthesis is functioning properly;

• A doctor’s review of the patient’s real-time muscle signals;

• Firmware updates as they become available

The development of programs, created as an accompaniment to prostheses, definitely helps their users achieve a better quality of life.

AI & Intuitive Control of Protheses

With developments along this topic, it seemed like the future of this technology depended on robotic advancements. Now the narrative shifted to focus on how reasonably artificial intelligence can be developed for prostheses. Indeed, AI could shape this field’s future very well.

The basis of incorporating AI in robotic prostheses is that the algorithm interprets nerve signals from the patient’s muscles which will allow for the prosthesis to be controlled more precisely. The study published in Science Translational Medicine by a team from the University of Michigan documents a new method to incorporate the technology with more types of prostheses.

Their new technique, based on regenerative peripheral nerve interface (RPNI), has surgeons use a small piece of muscle and wrap it around the end of the amputated nerve to produce amplified signals. Computational scientists on the team then apply machine learning algorithms to turn the signals into fine movements in a prosthetic. Participants were even able to use this smart prosthetic on their first try, Chestek added. They were able to perform fine motor controls such as picking up small toy blocks, making a fist, and pinching fingers together.

In November 2022, the Ukrainian startup Esper Bionics appeared on the cover of Time magazine. The publication included it in the list of the 200 best inventions for 2022. The company’s prosthesis has 24 sensors that capture and process muscle activity and brain impulses to activate the action in the hand. The developers claim that the exchange of information between the device and the human brain occurs through the brain-computer interface.

The hardware is supported by its own software. Esper Control is a non-invasive sensor system for reading muscle activity and transmitting brain signals, and Esper Platform is a cloud platform that uses machine learning algorithms to personalize robot arm control.

Thanks to digital signal processing data are transmitted to the cloud. Over time, the prosthesis begins to “understand” the frequently repeated algorithms of human movements and learns to anticipate them.

Of course, the system isn’t perfect. The researchers point to various kinds of fine motor control that are still difficult to achieve, such as wrist extension, wrist supination, and applied force estimation. Some of these movements will require additional implanted electrode sensors. A shorter reaction time would be appreciated by most users. And implanted electrodes always run the risk of being disturbed and requiring re-implantation.

For now, this AI approach is a useful step forward in the technology for amputees and an exciting avenue for future work.

Summing Up

Without any doubt, there’s a promise for amputees with advances in robotics, machine learning, and prosthetics. These developments we hear of are incremental changes that will add up to improve future artificial limbs; improvements that will turn them into truly artificially intelligent ones.