Osseointegration may present promising future for amputees
While patients with amputations are traditionally fitted with a socket that attaches the prosthetic to the limb, the socket may cause problems both functional and comfort levels.
“If you think about your thigh, for instance, it’s basically like an upside-down cone,” John A. Abraham, MD, chief of the Sarcoma Center of Excellence at Capital Health Medical Center and founder of orthopedic oncology at Rothman Orthopaedic Institute, told Healio. “You’re trying to get this plastic upside-down cone to stick, [and] the tendency is always going to be for it to slide off. So, then you have to have all different things that help try to hold it on and that often causes problems with skin and problems with pressure because you’re trying to force this socket to stay in one place it doesn’t want to stay.”
However, Abraham noted use of an osseointegrated implant can help eliminate the discomfort associated with the traditional prostheses that use a socket. One such implant is the Osseoanchored Protheses for the Rehabilitation of Amputees (OPRA) Implant System (Integrum AB), which was approved for use in transfemoral amputations in the United States by the FDA in December 2020.
“The term osseointegration means bone growing onto the surface of metal, and where that had been used in clinical medicine prior to this was mainly in dental implants,” Abraham said. “In dental implants, the same kind of rationale is used for connecting the implants to the bone just the way [the OPRA Implant] is connected to the bone for an amputation.”
Improvements, possible risks
In addition to eliminating the discomfort that patients with amputations can experience with a socket, Abraham noted the OPRA Implant System also provides functional improvements.
“The functional improvement is dramatic, especially in patients who are able to do a lot of rehab and build their muscles up and get the maximal functional benefit from it,” Abraham said.
But, like any procedure, use of the OPRA Implant System does not come without risks. Abraham noted one of the risks associated with osseointegration is the possibility of infection.
“So far, it seems like most of the infections are soft tissue related, not necessarily bone related, but you do need a patient who’s astute and who’s going to be able to pick up a problem and going to be able to tell you early if they see signs of infection,” Abraham said.
Currently in the early stages of being introduced to the market in the United States, Abraham noted surgeons working with the OPRA Implant System are carefully selecting patients based on their infection risk.
“We want to be careful and figure out what is the level at which a diabetic patient could get this [implant] or how far after chemotherapy can [a patient receive this implant],” Abraham said.
Other problems surgeons may encounter with the OPRA Implant System is the possibility of loosening and fracture, which Abraham noted are standard risks orthopedic surgeons face when implanting a piece of metal into a patient.
“Most of the surgeons are well-versed in how to deal with those [problems],” Abraham said. “But there are things we have to be aware of [and] there are things we have to look out for. This whole technique and this implant are early enough that we don’t have enough data to know, ‘What are the 10-year loosening rates?’ ‘What are the fracture rates when you’re putting these implants in?’”
Future of osseointegration
In the future, use of osseointegrated prostheses may change the way surgeons think about the connection between metal and bone, according to Abraham.
“For instance, there are technologies where you don’t have to rely on the biologic growth of bone on the surface, but it is the mechanical junction between the metal and the bone which causes the integration. We say it’s kind of a mechanical integration rather than a biologic integration,” Abraham said.
Another future that osseointegration presents is the possibility of creating a connection between the prosthesis and the brain by implanting electric cuffs onto the nerves that transmit electrical stimulation to the prosthesis, Abraham added.
“If I wanted to extend my knee, I think about extending my knee just like I would on my other leg and although the muscles are not directly pulling on anything, they’re sending a signal to a prosthesis and then the motor in the prosthesis drives that motion. You still made this connection between your brain and the prosthesis,” he said.
Abraham noted osseointegration in conjunction with techniques, such as targeted muscle reinnervation, can also decrease the nerve problems that patients with amputations may experience, such as neuromas, pressure on the nerves, phantom pain and phantom sensation.
“I think the future will be how to manage the interface, not only of the bone with the implant, but also the nerves with the implant,” Abraham said. “That’s going to be something that has dramatic impact for the future.”
Reference
- FDA approves prosthetic implant for above-the-knee amputations. https://www.fda.gov/news-events/press-announcements/fda-approves-prosthetic-implant-above-knee-amputations#:~:text=The%20U.S.%20Food%20and%20Drug,to%20have%20rehabilitation%20problems%20with%2C. Published Dec. 18, 2020. Accessed Jan. 24, 2022.
- Integrum AB granted PMA (premarket approval) by the FDA for the OPRA Implant System. https://integrum.se/press-release/?r=6482CF9C7BF93DF2&i=9. Published Dec. 18, 2020. Accessed Jan. 24, 2022.
Perspective
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While not without risk, there is tremendous potential in osseointegration. The benefits that osseointegration offers are already being seen by a growing number of amputees. I could not agree more with John A. Abraham, MD, when he commented that the “functional improvement is dramatic.” This is especially evident in those with high transfemoral amputations, bilateral amputations and those with or at risk for socket-related complications.
Osseointegration has allowed amputees that were, or would likely otherwise be, wheelchair bound due to difficulties and complications associated with prosthetic fitting to improve their quality of life by decreasing energy expenditure with ambulation, improving their overall walking ability and range of motion, not to mention improving their sitting comfort due to the lack of a socket.
While continued work is needed to minimize infection risk and implant-related complications, the future is here for the optimization of amputee outcomes.
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