The Present and Future of Osseointegration

As more people with amputations choose osseointegration (OI), prosthetists across the country are learning how to support this patient base. About 2,000 patients across the world have undergone the procedure to have titanium implanted inside their bones to connect to their prostheses. About 500 of those patients have received the Osseoanchored Prostheses for the Rehabilitation of Amputees (OPRA) Implant System, the only US Food and Drug (FDA)-Approved osseointegration solution in the United States. Those numbers are expected to grow as more patients learn about OI and the technology is opened up to different types of patients, including those with transhumeral amputations or missing fingers or thumbs. The experts warn that the procedure is not for everyone, and it can be risky, but it can also make a huge difference for patients who will never be comfortable in a socket, such as those with burns, skin grafts, or short residual limbs. Jason W. Stoneback, MD, director of the Limb Restoration Program at the University of Colorado (UC) School of Medicine and UCHealth Colorado, has seen patients marvel at the ability to walk with a cup of coffee or hold a child’s hand while crossing the street. One patient told him that when they had a traditional lower-limb socket, they would only go grocery shopping if they could find a close spot in the lot. “Now they just pull into the lot and walk in,” he says. “That’s a big deal.” Currently, there are two main types of implants. The screw-type is similar to dental versions where the titanium implant is shaped like a screw and twisted into the bone. These implants require two surgical procedures. In December 2020, the FDA approved the OPRA device for transfemoral patients who have rehabilitation problems or cannot use a traditional socket. The other type, the press-fit implant, is similar to the metal rods used in hip replacements. The rods do not have screw threads and are inserted into the bone by wedging the implant into the intramedullary canal. Depending on patient anatomy and other parameters, it can require one or two surgical procedures and tends to have a shorter recovery time than the screw-type. This type of implant is only available in the United States as a custom implant or under various FDA investigational or humanitarian device exemption pathways. Pros and Cons The benefits of OI are numerous and can be life changing, the experts say. First and foremost, they say, it means a life without sockets and the challenges they can present. “The benefits…are significant when comparing OI to a well-fitted socket, and overwhelming when compared to one that is poorly fitting,” says Chris Hoyt, director of OI at Rise Prosthetics, Colorado. “Perspiration, friction, and sitting comfort cannot be resolved with a well-designed socket.” Common socket issues such as putting on the device and volume fluctuation don’t exist with OI, he adds. “Unparalleled control of the residual limb and terminal device, repeatability in donning, unrestricted range of motion, and the elimination of volume fluctuation issues attract many amputees looking to improve their quality of life,” Hoyt says. Without a socket in the way, OI patients have been shown to have a better, anatomically correct gait, Stoneback says. “From our research lab, we know the patients’ gait and their skeletal alignment is normalized,” he says. “They can walk with a more normal gait and move their joints as they were originally intended, which we think will lead to potentially better joint preservation.” Stoneback’s research team is currently studying this potential joint preservation and whether it may lead to decreased cases of arthritis. Another benefit of OI is improved proprioception. Since the device has a direct connection to the body, the patient can better feel the ground and be more stable. “They have the ability to feel through the limb and can feel how much pressure they are putting on their limb,” Stoneback says. “They can tell if the position of their foot is in front of them or in back, like you can with a sound limb with your eyes closed.” Even little improvements can make a big difference says Michael Andrew Jenks, CPO, senior clinical manager at Medical Centers Orthotics and Prosthetics, North Carolina. “One of the most common and immediate feedback they give me is how happy they are to be able to sit on a toilet seat without damaging it,” he says. “It’s funny to think about, but really what’s happening is they are sitting down and using the toilet in a way that’s intended.” While OI experts are excited about the technology, they also warn that it can come with significant complications. Patients and their healthcare teams should carefully discern whether it’s the right choice, Stoneback says. “It’s not a panacea where if you get this everything will be fine,” he says. “There are risks.” The most common complication is infection. A 2017 study in Clinical Orthopaedics and Related Research found that 20 percent of patients developed bone infections, some so severe that they required the removal of the implant. 1 Skin infections, which can be treated with antibiotics, are also common. Other complications can include a fracture of the femur, a loosening of the implant, nerve pain, and changes in soft tissue that require surgical refashioning. Even with the complications, Jenks says that he’s seen patients who had to have their devices removed and were anxious to get them back once the infection cleared. “The ones I’ve talked to said it was horrible to go through, but they wanted to go back to it because of the freedom they felt.” Ideal OI Patients Due to the complications, the experts say if a patient can be successful in a socket, then they should probably continue using one. Hoyt says that some patients who request OI often just need a better socket. He suggests patients try out a different prosthetist before they pursue OI. “We’re seeing patients run toward osseointegration because they don’t know any better,” he says. “If they could find a talented prosthetist who understands socket design, then they could live a full and productive life without osseointegration.” That said, there are some patients who will never be comfortable in a socket. These include patients with a short residual limb, skin grafts, or burns. For those patients, the benefits may outweigh the risks, Stoneback says. “If you are able to wear a socket and are doing what you need with minimal problems, then you should think about staying in your socket,” he says. “If you are unable to live your best life in a socket, then you should look into it.” However, there are more criteria for considering OI than socket discomfort. Certain comorbidities can exclude patients from the procedure. Two large groups of patients with amputations—those with poorly controlled diabetes and vascular conditions—are considered unsuitable candidates for OI. Patients with poorly controlled diabetes tend to be more prone to infections. Vascular conditions may result in poor blood flow to the limb, which can impact the bone ingrowth and risk for infection. Stoneback says researchers are studying how these patients may be future candidates for OI. Erik Schaffer, CP, president and owner of A Step Ahead Prosthetics, New York, also warns that smokers should not get the implant. Smoke around an open wound will cause infections and keep the surgical wound from healing, he says. Along with physical health, patients should also be mentally prepared before they undergo the OI surgery. The most successful patients are those who understand the risks and are prepared to do whatever they need to stave off infections. “It takes a commitment of the patient to be successful with it,” Jenks says. “It’s not a lighthearted decision. They have to be willing to follow the hygiene protocols and follow the instructions.” Schaffer says that he has seen patients who have gotten the OI surgery in haste and later regretted the decision because they were not mentally prepared for the implant. He says patients should be fully informed of the procedure and learn about all the risks. “There are people who are miserable and can’t wear a socket and they will do anything,” he says. “We just have to make sure they are the right candidate.” The Right Alignment and Components Even though OI patients do not have to worry about socket fit, using the right components and finding the correct alignment is as important as ever, though there are some changes. “With the elimination of the socket, the OI prosthetist now can focus on optimizing prosthetic componentry to attenuate ground reaction forces while obtaining anatomical height and alignment,” Hoyt says. “Although the net result is identical, understanding that we are no longer spatially positioning a socket above lower-extremity components, but rather aligning the knee and foot beneath the implant is a new concept for many prosthetists.” Although patients with OI tend to have greater stability because of their ability to feel the ground through osseoperception, that increased sensitivity can also present an additional challenge, Jenks says. “With my above-the-knee OI patients, I’ve had to spend more time with alignment,” he says. “The OI patients will seek out optimal alignment that a traditional socket patient might not feel as acutely. You have to take more time and listen to a patient’s feedback and then translate it into what feels best.” Hoyt says that he has had OI patients who are uncomfortable with the new sensations. “Many patients who have undergone osseointegration report heightened awareness of their surroundings via sensory feedback or osseoperception, through their bone-anchored prosthesis,” he says. “This can be beneficial for many to prevent stumbles/falls, however, can sometimes be unsettling if [they are] hyperaware of every click, clunk, or vibration.” Hoyt says that hypersensitivity usually goes away in about six months as patients get used to their implants. Stoneback warns that prosthetists who work with OI patients should be experienced and be ready to work closely with the healthcare team including surgeons and physical therapists. “Transtibial osseointegration needs to be done by an experienced team,” he says. “It’s not just ‘hey you got this surgery and you are good to go.’ It’s a surgery, and it’s balancing and alignment. If you have a brand-new set of tires on your car and you don’t align them, they don’t work well and won’t last long. There are all sorts of things that go into this and having an experienced prosthetist is important.” Reimbursement As with many new technologies in O&P, reimbursement for OI componentry can be a challenge. Hoyt says that prosthetists working with OI patients are facing similar challenges experienced in early 2000s, when microprocessor knees were novel. “It will take time and education to demonstrate to some third-party payers the many benefits osseointegration offers,” he says. “To be pioneering in osseointegration also requires us to be pioneers in reimbursement.” Jenks says that it has helped that he works closely with the whole healthcare team, and they present a united, evidence-based approach to the insurance companies. “You have to roll up your sleeves and go to battle with them,” he says. At times, the reimbursement decisions do not seem to make sense, Hoyt says. For instance, he has seen cases where insurance will cover the osseointegration surgery but not the connector to the prosthesis. “We believe that once the asked-for osseointegration surgery has been approved and paid for, there should be no need to deny the connector,” he says. “The patient can’t ambulate without it.” Hoyt says patients must also be educated that connectors will need to be replaced throughout their lifetime, and regular maintenance is required. What’s Next Experts in the field of OI say they are excited about what the future has in store for patients. The next big step may be in the upper limbs. Myoelectric arms, which tend to be too heavy for a traditional socket, can be supported when used with transhumeral OI, Stoneback says. That implant, combined with technology that allows the device to be integrated with implanted nerve electrodes, also allows the patient to actively move their device. Hoyt says this will be a huge benefit to patients. “Although we have not fit upper-extremity osseointegration clients to date within our center, this will be a game changer for residual limb control, and a significant improvement in function as well as usage,” he says. Jenks says that OI has also started to be used to replace fingers and thumbs. That direct connection to the bone is giving patients much more functionality, he says. Schaffer likens the coming changes to the 70s television show The Six Million Dollar Man , whose protagonist has body parts made of bionic implants. “We’re there with neurobionics,” he says. “It’s insane and it’s exciting to be happening in my lifetime.” Even with these exciting advances, the experts say that there is still a lot of work to do for their patients with sockets. “There have been 2,000 amputees who have undergone OI in the world,” Hoyt says. “That means 99.9 percent of the amputees in the world must still wear sockets. We must continue to focus on improving socket designs to optimize comfort and function, while understanding how to care for those that have undergone osseointegration.” Maria St. Louis-Sanchez can be contacted at msantray@yahoo.com. Reference Tillander, J., K. Hagberg, and O. Berlin, et al. 2017. Osteomyelitis risk in patients with transfemoral amputations treated with osseointegration prostheses. Clinical Orthopaedics and Related Research 475(12):3100-8. Photographs courtesy of Erik Schaffer, A Step Ahead Prosthetics.

The Present and Future of Osseointegration

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