Utilizing prosthetic technology to improve quality of life: an interview with Ranu Jung and James Abbas

Abstract

In this interview, we spoke with Ranu and James at SfN Neuroscience (19–23 October 2019, Chicago, IL, USA) to discover more about their collaboration on a clinical trial aiming to improve the lives of American veterans and service members who have lost limbs. The clinical trial involves the adaptive neural systems neural-enabled prosthetic hand system [1,2].

To start, please could you tell me a little bit about your backgrounds in the field of bioelectronic medicine and how you started working together?

Jimmy Abbas

I am based at Arizona State University (AZ, USA) in the School of Biological and Health Systems Engineering. I also direct the Center for Adaptive Neural Systems there. My background is in the field of neural engineering and rehabilitation and much of my research has been directed at developing electrical stimulation technologies for use by people with spinal cord injury. Over the last several years I have been looking at stimulating peripheral nerves to restore sensation to amputees.

Ranu Jung

I am a biomedical engineer, located in Florida International University (Miami, FL, USA). I head the Biomedical Engineering department there, and I work with a large team of researchers, students and engineers in my laboratory, all working in the field of neural engineering and bioelectronics. In terms of how we started working together, I used to work in the preclinical space with animal models, computational modeling and also some neurostimulation work, while Jimmy was working with people with disabilities and with neuro electrical stimulation. We were colleagues in Biomedical Engineering at the University of Kentucky at the time and with our complementary strengths we thought that it would be a great opportunity if we could work together. It would let us follow the whole pathway, all the way from idea to delivery, we could do the computational modeling and preclinical models, then, as Jimmy had the expertise in working with people this could give us an opportunity to translate our ideas to a clinical level.

You have recently received a US Army grant for use in a clinical trial to improve the quality of life of veterans who have lost their limbs. Could you just give me a brief overview of this clinical trial and the motivations behind it?

Ranu Jung

We have previously developed technology for mapping task-related sensory information from prosthetic hands to stimulation commands and then to an implanted neurostimulator. When the electrical stimulation happens, the individual with the amputation senses it and they may perceive it as a hand opening or closing or tighter grip force. This technology was developed with the support of NIH. We then also got funding from the Defense Advanced Research Project to start a clinical trial on it. The Army opportunity now allows us to expand on this project. It will allow us to work with the Walter Reed National Military Medical Center (Bethesda, MD, USA) so that we can take the technology directly to service members and veterans who have a need for it. This process has to go through approvals both from Institutional Review Boards and from the US FDA before the expansion of the trial can occur.

It will allow us to develop the ability to work with different prosthetic hands that have been sensorized and our hope is that we would also be able to use this system for bilateral amputees. We are very thankful for this opportunity to use neurotechnology for the restoration of sensation to people who have lost their limbs. Our hope is that this is going to ultimately improve their quality of life.

Jimmy Abbas

In terms of the kinds of things we are assessing, one is that we need to understand what happens to the percept and so what is the patient feeling as we change the stimulation parameters? What does the person feel with different settings? Then, we need to make a decision as to which ones are going to be most useful on a daily basis. We also want to try to understand what kind of percepts are possible with this technology and how the person can learn to interpret them differently. We are also assessing how well can an individual take this information and incorporate it into actually doing something with the hand. Does it really help when they are using their prosthetic hand? We have some very fundamental tasks, such as asking them to squeeze an object to a certain level, but then we are also looking at more functional things in the laboratory tests, like how easy is it for an individual to pick up objects with the prosthesis.

What is the level of patient participation in the study?

Ranu Jung

The initial study takes place for over two years; the implant is designed to be a lifetime implant. For the first several months the participants would come for quite a few intense studies in the lab. During this time, we are effectively fitting the system to the person. After that, somewhere around 3–4 months, they are allowed to take the system home and use it in day-to-day life. However, they would come back to the laboratory setting on a regular basis and then with more and more infrequent visits over a two year period.

The goal is really that they should be able to take it home and that this is something that becomes available commercially. You would go to your clinic, the prosthetist will fit you with the prosthetic system and perhaps it may be that the prosthetist will also fit you with the simulation system and then you would go home and you have to come back for regular checkups and regular adjustments of the system.

You are using an adaptive neural systems neural-enabled prosthetic hand in the trial. Could you tell me a bit about the components of the prosthetic hand and how they work together, as well as how they interact with the patient?

Ranu Jung

You can think of it as having three components. The first one is the prosthetic hand itself. It is a commercial prosthetic hand that has been modified, in that there are sensors embedded into the hand itself. There’s a sensor which is telling you about the aperture of the hand, that is, how much is the hand open. Another sensor is telling you how much force is applied on the thumb (but it could be for any of the prosthetic hand fingers). So, now you have got a prosthetic hand that is sensorized and the next thing we have to do is to connect a prosthetic frame. The prosthetic frame is just like any regular prosthetic frame that a person might use to control myoelectric prosthetic hands for muscle control. However, there is a slight difference in the frame, in that we have made a little gap for the implant-hand interface, a little box containing the electronics that collect information from the sensors in the prosthetic hand to determine the stimulation map. There is also a little window for the user to be able to select different stimulation programs and adjust the intensity of the stimulation signal. The frame also houses the battery that powers the prosthetic hand; the same battery is used to power these electronics.

Now you come to the implant. The implant is a neurostimulator that is connected to very fine wires which form the electrodes that go inside the nerves. This neurostimulator is implanted inside the upper arm. There is an antenna on it so that it can communicate with the implant–hand interface which also has an antenna. These can then communicate wirelessly across the skin. And how do they stay together? There is a small magnet on the external antenna and another embedded in the internal antenna. So, across the skin when the external antenna is aligned with the internal antenna they just hold together via the magnets.

So, that together forms the whole system. The sensorized prosthetic hand, the implant–hand interface, where the smart algorithms work, and that communicates wirelessly with the implanted neurostimulator which has got the fine wire electrodes that go inside the nerves.

The study plans to recruit six individuals with amputation on one side at the level of the forearm and two individuals with amputation on both arms. Please, could you give the reasoning behind this reason?

Jimmy Abbas

For anyone that has lost a hand, getting the sensation back, we believe that being able to feel what the prosthetic is feeling would be highly valuable. For somebody who has lost one hand, they stand a lot to benefit from a prosthetic device, and this is the population we’ve been working with. But if you think about someone who has lost both hands and they don’t have the option of using their other hand for tasks, there are probably many more benefits. In the general population, there are fewer people who have lost both hands and are in need of such a device. We are also working with a population of war fighters and veterans and in this group there are instances that, due to the circumstances, they have lost both hands. It’s a little bit more common in that population than in the general civilian population to have bilateral amputation.

There is known to be a high incidence rate of patient dissatisfaction with current prosthetic limb technologies – do you have any theories for the reason behind this?

Jimmy Abbas

Unfortunately, there are a number of factors that might contribute to somebody not using an upper limb prosthesis. Some are due to the comfort of the socket for example, but one of the major factors that has been identified is that people feel a lack of sensation and a sort of disconnect from the limb. They are using their hand, but they don't have a sensation of what they are doing. They have to pay so much visual attention to it that it becomes unnatural to use. Now we know that the sensation is very important when we are using our biological hands to manipulate objects and to do tasks. So, one of the main motivating factors for this clinical trial was to allow people to use their prosthetic hand in a more intuitive manner and in a way that is more effective.

Ranu Jung

The sensation may also help them embody the prosthetic hand, so that their body eventually recognizes the limb. Our study with the first person who has had this implant reflects how perception of the end of his phantom limb has changed. Often, after an amputation, the phantom hand is drawn in, to the end of the residual limb. We observed in our study participant that the stimulation and sensory feedback has led to a reversal of this inward telescoping and pushed the phantom hand back out closer to a normal arm’s length. There is also the factor of improved body image which might all help in the overall well-being of a person.

Please could you tell me about how affordable the neural-enabled prosthetic hand will be to patients?

Ranu Jung

Unfortunately, we don’t have an answer for that yet but the thing to keep in mind is that there is already a wide range of costs for myoelectric prosthetic hands. There are some that are very high end with lots of capabilities or different features and these are much more expensive than the ones that at the lower end. At this time, sensorization of prosthetic hands is still in the early stages of development and not many companies are working on it. But, as time goes by, and if more companies choose to sensorize their prosthetic hands, we would expect to see the costs come down. The cost of putting sensors in is not going to be that tremendous and the sensors themselves don’t cost much. There is of course the other part of the prosthetic fitting, we expect that that will remain more or less the same cost as it is now.

Finally, there is the neural implant. In terms of neural stimulators, whether it is for stimulation of the vagus nerve or you are talking about systems for deep brain stimulation or other organ systems. The market for these is expanding so the cost of implantable neurostimulators is likely going to go down. So currently, it would be expensive, but our hope is that it would go down in the future. Also, the question is whether the cost is reimbursable and in different markets in different countries it will vary. If it becomes a reimbursable technology, then that would be the most beneficial for the users.

Finally, where do you see the future of this technology heading?

Jimmy Abbas

These electrodes and the simulation system, especially the implanted components and the way they have access to the nerves and can communicate with the external components, has potential for use in a number of other applications. There is a lot of interest in stimulating nerves in the body to affect organs other than muscles. This whole field of bioelectronic technology has good potential to give very high specificity as to which neurons are being activated. If we can demonstrate that this kind of technology can work and is reliable over the long term, then putting these electrodes in other nerves for other medical purposes becomes that much more promising.