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Rickard Brånemark, MD, PhD, founder and board member of Integrum AB, shared his ideas about current research concerning upper-limb osseointegration and the progress of his own clinical trials with the new e-OPRA method.
We continue that conversation here:
What are the challenges that must be overcome to pronounce your current research completed, safely approved, and ready to apply to patients worldwide? Is it the e-OPRA system described on the Integrum website?
Brånemark: There are a number of challenges to bring this to patients worldwide. Especially if we look into the US where the current OPRA system is not approved for upper-extremity amputations. In Europe it is approved, so there it can be used for transhumeral amputations. Of course, the safety needs to be verified according to regulatory rules like the [US Food and Drug Administration] and the [European Union Medical Device Regulation]. But we also need to verify that this is actually useful for the patient with an amputation. I think that the study I mentioned previously with Shirley Ryan AbilityLab will be a very important study to hopefully verify that with a smart implant utilizing the OPRA and e-OPRA combined system, we will be able to deliver much more functionality, robustness, and what we talk about a lot: improved embodiment for a patient who lost an arm or leg.
Can your current research also be applied to benefit people with transradial amputations? Is that part of the current e-OPRA research program, or might we expect to see that be addressed in the future?
Brånemark: We have been doing some limited research on below-elbow amputees, and we will continue to work on that even though the first priority is transhumeral amputees. Regarding transradial amputations, I feel in many instances a socket is a very valuable alternative. Shorter residual limbs, where it is difficult to get the retention without compromising the range of motion of the proximal elbow joint, is where osseointegration can be considered—maybe in combination with e-OPRA and implanted electrodes to utilize the remaining muscles or in cases we have also done regenerative peripheral nerve interface (RPNIs) and targeted muscle reinnervation (TMRs) proximal to the elbow joint and put wires there to improve the functionality. On the above-elbow amputation level it is typically very challenging to get a socket to fully utilize the remaining part of the body. That raises bigger challenges with retention, and especially if you have a somewhat shorter remaining humerus, you might need to go up and restrict the range of motion of the shoulder joint maybe even with a harness. There I feel that osseointegration is more strongly indicated.
Others have noted that some researchers are combining upper-limb osseointegration with other amputation-enhancing surgeries (TMR, RPNI). From your perspective, what may be gained/lost in function as they attempt to balance these additives to the OI program?
Brånemark: The more complicated you make a system, there is an increased likelihood that the robustness will be diminished. But these are not very complicated systems and control systems like Coapt are already very robust and working well. So that’s why I think that the add-ons that we can deliver with implanted electrodes in combination with TMR and RPNI procedures as well as AMIs (agonist-antagonist myoneural interfaces) are the way to go, and today that will be the best we can offer for amputees. And it will not only add what we call a new function; we can add sensory feedback with different modalities using nerve cuff electrodes. But we can also use RPNI in new ways, maybe even together with TMR or AMIs to give the person with an amputation some sensory feedback. And all of this will most likely lead not only to improved function but also will improve embodiment so that you no longer feel that the artificial prosthesis is something that is not a part of your body. It’s becoming more and more a part of your body.
Some claim that the most advanced system for transhumeral amputation is osseointegration combined with TMR, and then decoded via machine learning or pattern recognition provided by Coapt or similar system—and that such combinations are being delivered in Australia, ahead of research in the US and elsewhere. Can you address this, and share what the risks and challenges might be along the way to making such combinations more widely available globally?
Brånemark: I’m quite sure that our group in Sweden is the world leader in this area, and we have also done extensive research on the lower extremity together with MIT and Brigham in Boston. We have, for instance, used osseointegration with TMR for well over ten years, combined with the e-OPRA. To my knowledge, no such trials have been done in Australia. When it comes to using Coapt or a similar system via skin electrodes, I think this has been done globally in many instances. The problem with skin electrodes is that the robustness of the signal and the precision to pick up tiny weak signals is rather poor, so you cannot use the more sophisticated reconstructive surgical techniques like AMIs and RPNI. TMR might be possible but it’s still a challenge to correctly detect different signals. It is also true that at Walter Reed they have done several OPRA implantations combined with TMR dating back to 2018, I believe.
The possibility of including fiber optic cables in future osseointegrated upper-limb prosthetic systems has been raised. What is your opinion about the feasibility of this approach?
Brånemark: Of course, fiber optic cables can transfer a lot of information which is good. In principle, we can use fiber optic cables with the e-OPRA upgrade to the OPRA system. We need to develop certain techniques to increase what we call the bandwidth. There are also other possibilities with fiber optic cables going directly through the skin, but of course cables going through the skin present certain challenges.
What might readers of The O&P EDGE need to know about the direction upper-limb osseointegration is taking, and its potential evolution in the future?
Brånemark: Regarding what we will be able to do together with osseointegration and different wired or wireless systems—I think the sky is the limit. We should be able to do a very sophisticated, robust system, and of course I’m a proponent of the wired system because a wired system is more robust than a wireless system. Everyone working with Wi-Fi knows that. It’s also true that if you’re in an environment with a lot of electromagnetic interference, e.g., working with power tools, etc., then the wired solution is much more stable. So, I think the best and strongest and most robust system for the future will be a combination of wired interfaces into the body combined with these sophisticated reconstructive surgeries we’ve been talking about, TMR, RPNIs, AMIs, etc. That will also require that we all help to develop better and more sophisticated robust prostheses—not only with motor function, but also with more advanced sensory feedback.
Judith Philipps Otto is a freelance writer who has assisted with marketing and public relations for various clients in the O&P profession. She has been a newspaper writer and editor and has won national and international awards as a broadcast writer-producer.
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