After a decade of working with amputees in Haiti, Joe Mahon, CP, often thought about how amputees could benefit if they could adjust their own prosthesis. However, he didn’t know how to make this idea a reality until he went skiing with his wife in 2009.
“I was waiting for her to adjust her snowboard boot, and I sat there and watched her use the Boa dial to loosen and tighten it,” Mahon, the chief executive officer of Revolimb, told O&P Business News. “And it occurred to me that this might be the way to [create an adjustable prosthesis].”
That night, Mahon used a razor to disassemble his wife’s boot and examine the Boa closure system that controlled the boot’s fit. Boa technology, which is used in snowboard boots, sneakers and other athletic gear, utilizes a system of reels and steel laces that are controlled through a dial located on the outside of the shoe.
Once Mahon had figured out how the system worked, he began experimenting with ways to incorporate this technology into a prosthetic socket.
Images: Joe Mahon
“It took us a couple of years of testing to fine tune the design and figure out if we should bolt the pieces onto the limb or laminate them into the limb,” Mahon said. “But we finally decided that laminating the Boa system into the composite was the most efficient way to build the limb and probably the most durable.”
Mahon originally worked with active amputee athletes and veterans to test his prototypes.
“They decided that they also wanted the adjustable limb as their everyday leg, which is when we decided that there might be more applications then just developing nations or athletes,” Mahon said. “This could be used for just about anybody.”
Once Mahon settled on a prototype, Revofit, he approached Boa about the possibility of a partnership, which they accepted.
“We partnered with Boa and are using their dials,” Mahon said. “But we modify them and add our lamination pieces, guide tubes, filament and a few other pieces to complete the actual kit.”
The Revofit socket uses a wiring system that is connected to a series of adjustable panels inside of the socket. A dial on the outside of the socket controls the wiring system and allows the wearer to manage the fit and compression level.
“The patient releases the dial, which opens the panels up, slides the socket onto the limb, locks themselves in, and then can slowly increase compression onto the limb until they feel that it is adequate for them,” Mahon said. “There is also expansion. If a patient has a hard time getting a limb on when they are swollen, they can just release the Boa mechanism and the panels adjust outward.”
The Revofit socket allows for quick modifications, particularly for patients who experience frequent changes in limb volume.
“There’s the soft tissue areas of the limb that you can increase compression on, which allows for the bony, sensitive areas to not have any compression,” Mahon said. “And unlike wearing a sock, which can increase compression about the entire limb, the adjustable panels pinpoint the areas that can take that compression.”
The Revofit is fit like a typical prosthesis. After a check socket has been made and fitted, Mahon waits several hours for the patient’s volume in the residual limb to change. Based on the volume change, Mahon places pads on different areas of the limb that need compression and then transfers this information to the laminated socket.
“The adjustable panels are customized for each person,” Mahon said.
Areas are then cut out of the socket and replaced with panels lined with foam or gel padding, which are controlled by the dial. The amount of compression is controlled by the thickness and durometer of the pads, and the socket can include multiple dials to control different areas and create a multi-zone adjustable socket. The Revofit is also compatible with most suspension systems.
“We don’t want to dictate what can and can’t be used with the system,” Mahon said. “We just want to make it available for everybody, and let them decide what is applicable for their patients.”
The Revofit is available for upper and lower prostheses of all levels.
“For the upper extremity myoelectric prostheses, we made the electrode panels adjustable,” Mahon said. “A problem we have seen with myoelectrics is that patients start losing contact with the electrodes, which results in false signals and erratic control. So being able to increase compression and maintain contact with the skin results in better control and less fatigue.”
To date, Mahon said the Revofit has delivered many benefits to wearers, including increased socket comfort, better fit, less limb levering, decreased muscle cramping, decreased sock usage, decreases in secondary complications, increased socket ventilation and improved gait and movement. And the dial is accessible through clothing, so the wearer can more easily adjust the fit.
“The patient feedback has been great, which is why we want to get it out,” Mahon said. “And it’s not just beneficial for athletes. Someone might want to release the compression when they sit, and they can just reach down and disengage the system for a more comfortable fit while they’re sitting without taking the leg off.”
This technology can also potentially reduce the amount of office visits a patient will require.
“Since the patient can control the compression and comfort levels depending on the activity, we think it will decrease patient visits for the minor adjustments that often happen,” Mahon said. “Of course, we still want the patients to come in for maintenance and their regularly scheduled visits, but in terms of day-to-day adjustments, it’s in the patient’s hands.”
Currently, the Revofit is being distributed by Revolimb, but they have plans to expand distribution in 2013. A licensing module will be available online and can be completed for $100 per facility. Once a facility is licensed, it can purchase the Revofit lamination kits, which range from $75 to $150, and the facility will be able to fabricate the prostheses onsite. There is also a central fabrication facility in Salt Lake City that will fabricate devices if a facility prefers not to complete the licensing process.
“We want to get it out into the prosthetic market in 2013,” Mahon said. “We want facilities to be able to build their own devices and give them the foundation and education to do this.”
Mahon also hopes to make this technology available to amputees in developing countries who have limited access to prosthetists.
“It would be a great benefit for amputees in developing countries to have the ability to adjust their own socket as they change throughout the days, months or years,” Mahon said. “There is unlimited potential, and we’re excited to see what designs prosthetists create for their patients.” — by Megan Gilbride
Disclosure: Mahon is the chief executive officer at Revolimb and the developer of the Revofit.