Mixed Signals: How Coapt, Myo, and Subcutaneous Wiring Animate OI Upper Limbs

Since the amazing intricacies of osseointegrated (OI) upper limbs are often lost in shorthand engineering explanations of how and why they work, we asked an expert, Levi Hargrove, PhD, P. Eng, Shirley Ryan AbilityLab, to add clarity. Q: For years we’ve been hearing and talking about myoelectric upper-limb prostheses. Are OI upper limbs also myoelectric prostheses, but ones that receive and recognize activation signals differently? A: Yes. “Myo” means muscle; “myoelectric” describes any artificial arm that’s controlled with muscle signals. Q: So how do those muscle signals bridge the gap between the residual limb and the prosthetic limb, conveying the message to move as desired? Is this where Coapt performs its magic of myoelectric pattern recognition? A: When people contract their muscles, they generate a very tiny amount of electricity—we all do whenever we contract our muscles. Coapt puts electrodes over the top of the muscle. The electrodes serve as microphones that can detect those electrical signals; then they use computer algorithms to determine how the person was trying to move their limb, just by listening to the muscle contractions. Coapt has a specialized AI algorithm that listens to those muscle contractions and says, “Based on this pattern of muscle activation, I know that the person wanted to move the prosthesis in this way.” Q: Does the OI connection make a difference in that signal, or the pattern’s reception or recognition? A: Someone who had osseointegration, where the arm is implanted in their bone (their humerus), has a nice solid connection. That allows the muscle signals to be picked up either from the skin’s surface or, in the case of e-OPRA, with a wire that goes inside of the body through the e-OPRA connection. Once those muscle signals—usually eight or ten of them—are all measured together, the Coapt AI algorithm decodes it and tells the prosthesis how the person wants to move it. So that movement happens instantaneously: the person just thinks about moving their arm, their muscles contract, the algorithm predicts what the person wanted to do and then tells the prosthesis to move that way. Q: Does it make a difference whether the signal comes through the skin’s surface or subcutaneously—directly from the electrode’s contact with the muscle via the e-OPRA conduit? A: Subcutaneously, from inside the body, would be like having a conversation with someone in the same room, versus having that conversation through a wall, where you might have to hear it muffled—because the intervening skin muffles those electrical signals. By measuring subcutaneously you’d get a nice clear picture of what the muscle is trying to tell you from inside the body, where the signals originate. It’s a much easier way to communicate more information, where even whispers could be understood. Q: Is there any health risk from inserting wires, or concerns about the wires deteriorating inside the body? A: While wired is always a concern, surgeons have decades of experience putting wires inside of the body now, primarily through pacemakers, so the technology has improved. The engineering field has developed better materials, and we have better ways of placing the wires inside of the body. There’s always a minor concern, but the wires are definitely much more reliable than they might have been 30 or 40 years ago, because the whole implantable medical field has continued to evolve with better materials and more precise surgical implantation techniques. 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.

Mixed Signals: How Coapt, Myo, and Subcutaneous Wiring Animate OI Upper Limbs

To Infinity and Beyond? Imagineering the Future of OI

In Memoriam: Verne Bintz

In Memoriam: Verne Bintz

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Mixed Signals: How Coapt, Myo, and Subcutaneous Wiring Animate OI Upper Limbs

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To Infinity and Beyond? Imagineering the Future of OI

In Memoriam: Verne Bintz

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