This article will appear in the upcoming April print issue of Surgical Products.
Curiosity got the best of U.S. Marine Staff Sgt. James Sides.
When approached with the opportunity to serve as the first test recipient of a new, innovative, and potentially beneficial implantable myoelectric sensor (IMES) system for long-term use of prosthetics, Sides knew it was a chance not to be missed.
Sides was injured in action when an improvised explosive device detonated underneath him on July 15, 2012. He was on his second tour of duty in Afghanistan. The explosion caused him to lose both his right hand and the vision in his left eye. Doctors determined the best course of action for his recovery involved taking half of his right forearm and fitting him for a prosthetic. It proved to be a less-than-ideal solution for Sides. He struggled to adapt to the prosthetic and was not thrilled with its performance as he attempted even the simplest of everyday tasks and activities.
Months passed, and in early 2013, the Alfred Mann Foundation was in need of a handful of individuals to receive, test, and provide feedback on an experimental system designed to be the first minimally-invasive, intuitive, multi-channel control system for prosthetics. The foundation found its first willing and able subject in Sides.
“Being the first guy, I felt not like it was my duty, but it was an honor to be a part of it,” he says. “I wanted to be the guy to help progress prosthetics, not just for disabled vets but for others.”
The potential of the IMES system was immediately evident to Sides. Doctors expressed excitement and optimism that it had the potential to help him perform his day-to-day activities with greater ease and more effectiveness. The chance to improve his quality of life ultimately convinced Sides to pursue the unique opportunity.
As a test subject, Sides was told the system would allow him to intuitively operate three different prosthetic movements simultaneously: opening and closing his hand, rotating his wrist, and moving his thumb. More importantly, these three key movements would combine to allow SSgt. Sides to have better control over his prosthetic than he would get from more commonly-used body-powered prosthetics or motorized prosthetics. The IMES system was also designed to address many of the shortcomings of current myoelectric control systems. In some respects, their function is limited because muscle signals are detected by electrodes placed on the surface of the skin – sweat, movement between the electrode and the skin, and limited access to only large muscles close to the surface of the skin. These limitations make control non-intuitive, inconsistent, and unreliable. Not so with the IMES system and its ability to allow Sides to operate three prosthetic movements at the same time.
“The advantage of simultaneity is that the prosthetic operates more like a natural hand than a linear, robotic limb,” says David Hankin, Chief Executive Officer of the Alfred Mann Foundation.
How It Works
The IMES system works by utilizing electro-chemical signals in the body that occur when a muscle contracts. Tiny IMES implants about 16 millimeters long and two millimeters wide are surgically placed into the residual muscles in the patient’s amputated limb. They serve to detect movements in portions of the limb that no longer exist. The electro-chemical signals are then captured and wirelessly transmitted from the implants to a decoder box designed to serve as an electronic “brain.” The IMES system also connects the brain to the artificial limb, allowing brain signals to control the prosthesis.
Once aware of how the system worked, Sides agreed to take part in a two-year study and underwent surgery at Walter Reed National Medical Military Center in Bethesda, MD in June of 2013.
Dr. Patricia McKay, orthopedic surgeon and Assistant Dean for Clinical Sciences at the Uniformed Services University of the Health Sciences, operated on Sides at Walter Reed. According to Dr. McKay, the procedure was a fairly straightforward one with minimal risks for post-surgical complications.
Dr. McKay says the surgical team acquired useful knowledge and additional confidence prior to the procedure on Sides by practicing on a cadaveric arm.
“What we found is that in a normal arm, the muscles are all exactly where they were expected to be,” she says, adding that the practice included placing implants in the cadaveric arm. “But in somebody who has had an amputation, the trauma that led to the amputation distorts the normal anatomy.”
To make matters worse, there are times where the amputee’s muscles have been wrapped around a bone in ways that make it fairly difficult for surgeons to identify them. As a result, in the case of Sides, it was determined the best strategy for procedural success was to ensure he was awake during the surgery. This allowed him to move certain muscles during the procedure, which helped doctors properly identify them.
“If we didn’t have him awake, there would be a small risk that we could have the device in a muscle he didn’t have good control over,” she says.
The procedure was a success and Sides fared well during his two-week post-surgical recovery. Dr. McKay says she was amazed by the results of the implementation of the system.
“This technology gives the patient a much more intuitive control of the limb and a lot more options for how to use the hand,” she says. “It’s a lot more functional.”
Three patients have been implanted and are testing the IMES system. However, what’s more notable – and exciting – is that all three patients have reported satisfaction with the system’s functionality.
According to Hankin, there is good reason to believe the IMES system could be made available to the public in the not-to-distant future.
“We are exploring collaborative relationships with the developer/manufacturers of many different robotic limbs so that when the system does hit the market, the systems will be compatible without the need to tackle difficult integration issues that we are undertaking now,” he says.
As of press time, Sides is faring well and plans to retire from the Marine Corps at the end of March and return to California to pursue a degree in geology at a local community college.
He says he’s appreciative of the opportunity to test the system, but he doesn’t think he’ll fully recognize its benefits until the trial is complete
“I don’t think it’s really going to hit me until they take it away that I’m going to realize how big of a deal it was to move myself whenever I wanted to and to have simultaneous movement,” says Sides. “I think that’s going to be the two biggest things I’m going to miss with this.”
Sides is also adamant that the system is reaching its potential as a viable option for amputees.
“They say this the way it’s going to go, and I hope so,” he continues. “Right now it is the best thing they’ve come up with.”
Dr. McKay agrees.
“I think it’s really the next step in the myoelectric type of prosthesis,” she says. “It gives us the potential to add a lot more functions to that limb in terms of what actions the patient can control.”
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