Osseointegration, the structural connection between bone and implant, was first attempted on rabbit bone by Per-Ingvar Brånemark in the 1950s. A little more than a decade later, Brånemark placed osseointegrated dental implants into the first human patient before using this technology on a transfemoral amputee. Coming full circle in the 1990s, Brånemark’s son, Rickard Brånemark, MD, PhD, of Sahlgrenska University Hospital in Gothenburg, Sweden, and colleagues continued to apply the technology to both transfemoral and upper-limb amputee patients. Since then, osseointegration has been adopted in Europe and is awaiting approval from the FDA.
In the first stage of the Swedish two-stage procedure, a threaded titanium implant is inserted into the marrow space of the bone of the residual limb. The implant becomes integrated into the bone over time. Approximately 6 months later, a titanium extension, known as the abutment, is attached to the fixture and brought out through the soft tissues and the skin. The prosthesis can then be directly attached to the abutment, eliminating the need for a socket, which can cause skin irritation and sweating. A strict rehabilitation program is required for both stages of the surgery for successful outcome, including gradual and progressive weight bearing on the prosthesis.
“I wouldn’t say all amputees need an osseointegrated prosthesis, but enough [patients get] so much benefit out of an osseointegrated prosthesis,” Horst H. Aschoff, MD, head of the department of plastic, hand and reconstructive surgery at SANA-Clinic in Lübeck, Germany, said. “We had a lot of patients who came out of a wheelchair back onto their feet, which is important. I think osseointegration will be one more part of the scenery in prosthetic equipment for those patients.”
Patients who benefit from osseointegration include those who have continuous socket problems and patients with short residual limbs, as well as non-dysvascular patients and patients who perform at low to medium activity levels who have tried all possible interface solutions. Patients with upper extremity amputations are also eligible for osseointegration.
“Patients with a residual humerus can do a lot more with motion and function than the suspension systems that wrap all the way around the chest and the back,” Roy D. Bloebaum, PhD, of the University of Utah Orthopedic Center, told O&P Business News. “It makes it easier for them to do more with their upper limbs than with the restrictions that come with the suspension systems.”
Pros, cons of osseointegration
Not all amputees are eligible to undergo the procedure due to contraindications. Dysvascular patients and patients who function well with a socket are not considered good candidates for osseointegration, as well as patients with medical conditions such as diabetes, peripheral vascular disease, hip contractures or excess weight. Even among individuals who are eligible for the surgery, there are many risks associated with the procedure, including infection, fractures, loosening of the implant and poor cosmesis due to permanent abutment. Patients are also required to undergo a long rehabilitation period (up to 18 months), treat the abutment skin area on a daily basis and are not allowed to perform high-impact activities, such as running or jumping, which may be disadvantageous depending on their daily lifestyle.
However, osseointegration also presents many advantages to patients. Patients will not sweat or experience skin irritations, pain, pressure or discomfort associated with a socket. The prosthesis is easy to don and doff and patients experience good suspension, no restriction of hip movement, comfort in the sitting position, a more natural sensation in the prosthetic limb and increased bone and muscle mass.
“[Patients who undergo osseointegration] report improved functionality. Clinical follow-ups of prosthetic users show improved quality of life compared to the situation before osseointegration,” Brånemark and colleagues reported. “Patients experience improved sensory feedback because of the phenomenon of osseoperception. New prosthetic technology includes different platforms, where osseointegration is one important part.”
Unsure if individuals would be willing to undergo osseointegration due to the risks, Bloebaum and colleagues surveyed 73 individuals with lower limb amputation at or above the transtibial level to determine perceptions and acceptance of osseointegration. The researchers sought to define osseointegration implantation selection criteria and barriers to patient acceptance of the procedure.
“It is expected that this information will facilitate the reduction of osseointegration procedure risks, the enhancement of potential benefits and the development of innovative rehabilitation strategies,” the researchers said in the study.
Despite the benefits, study results showed that 33% of participants would consider undergoing osseointegration while 42% would not and 25% were uncertain. Concerns that made individuals wary of the procedure included infection, potential activity limitations due to implant failure, long rehabilitation course and risk of a broken bone in the residual limb. Anticipation in improvements in prosthetic function, improved activity level, suspension system security, improved walking ability and ease of prosthetic attachment were considered advantages to the procedure.
Due to the risk factors associated with osseointegration, several researchers and prosthetists have been working on alternatives that, while similar to osseointegration, may reduce these risks.
In the United Kingdom, Gordon Blunn, PhD, of the Institute of Orthopaedics and Musculo-Skeletal Science, and colleagues have been using an implant they call intraosseous transcutaneous amputation prosthesis (ITAP) to achieve osseocutaneous integration, which was mimicked after the skin-bone interface around deer antlers.
According to Blunn and colleagues, “osseocutaneous integration differs from osseointegration because the aim is to create a stable interface among the implant, the bone and the soft tissues. This reduces the risk of soft tissue infection and troublesome discharges, which are problems encountered with current osseointegrated implants that focus largely on the bone-implant interface.”
A second alternative is being developed in Germany by Aschoff and colleagues called the Endo-Exo-Prosthesis, which was first implanted in a young motorbike rider in 1999 after a traumatic transfemoral amputation. Also known at the Integral Leg Prosthesis (ILP), the innovation is directly implanted in the remaining bone, securing a long-term and safe connection between patient and prosthesis and reducing the risk of fracture and infection.
The ILP is implanted in two steps, either with general or local anesthesia. In the first step, surgeons use old scars to open the skin and soft tissue covering the lower end of the remaining bone. Then the bone is uncovered and shortened before the implant stem is inserted into the bone. A drain is also put into the residuum and the soft tissue coat is closed again. About 6 weeks later, the second stage occurs, where a stoma is created using a core-cutter and the exo-module of the prosthesis is attached to the internal implant stem through a dual cone, serving as the bridging connector.
“The main difference between the Endo-Exo-prosthesis and Brånemark’s system lies in the surface of the implant,” Aschoff said. “Brånemark’s screw allows an attached growth of the bone against the metal, while the EE consists of a three dimensional structured surface where an interconnective bone growth leads to a comparable expanded contact between metal and bone that hinders the occurrence of a connective tissue interface. A consecutive difference is the much earlier termination of the second-step operation.”
According to the ILP website, since the stem is directly anchored to the bone, patients will experience enhanced mobility in the hip joint, more effective use of the remaining muscles within the pelvis, the thigh and knee, a more effective load transmission to the exoprosthesis, more comfort when sitting and a wider range of motion and free movement. The ILP also requires less energy consumption during ambulation and feels lighter in weight. It has also been shown that the ILP requires less energy consumption during ambulation.
Patients still need to keep the stoma area and exo-modules clean by washing with soap and water at least twice daily. Excessive rotational movement of the prosthesis should be avoided. A shear pin at the inner part of the dual cone adaptor is designed to break off and prevents the bone from taking up too much load and fracturing if excessive force is applied.
Finally, patients have the option to receive similar benefits of osseointegration without the surgery with the High Fidelity Interface. Created by Randall Alley, BSc, CP, chief executive officer of Biodesigns Inc., the High Fidelity Interface works with upper and lower limb prostheses, with all myoelectric, body-powered or hybrid control systems, as well as any type of suspension system and is effective when applied to orthotic devices.
“[While osseointegration] is a practical consideration, the HiFi Interface with its osseosynchronization technology achieves nearly all the benefits of osseointegration with none of the complications currently associated with osseointegration. In addition, it has no known contraindications,” Alley told O&P Business News. “The rise of osseointegration and the HiFi is in large part due to the complications of traditional sockets, which I agree have many inherent problems. The results with the HiFi have been so good that I think it is common sense to ensure all non-surgical options have been tried prior to undergoing invasive surgery.”
Unlike the traditional cylinder sockets, the High Fidelity Interface has a clover leaf shaped socket that stabilizes the patient’s bone and makes the prosthesis feel more attached. The High Fidelity Interface also can be used by any amputee, whether they have a low or high activity level or other health issues, and is advantageous to patients in the United States, where osseointegration is not an approved procedure yet.
“I want osseointegration to succeed, but I don’t want people to continue to use the same excuse that sockets haven’t changed since the 1600s,” Alley said. “The main thing is, prior to having invasive surgery, [practitioners and surgeons need to] make sure patients know what all the alternatives are.”
Although osseointegration eliminates the need for a socket, it does not mean that prosthetists will be out of a job.
“[Osseointegration] doesn’t eliminate the prosthetist at all,” Bloebaum said. “First, the prosthetist will be challenged to be more creative to make the devices lighter yet more functional. Secondly, there are going to be a lot of people who should be in a socket if they’re comfortable with it and [the socket will] probably be the first line of treatment for patients, especially if they have the long length of their limbs.”
At the 2011 MyoElectric Controls/Powered Prosthetics Symposium in Fredericton, New Brunswick, Canada, Brånemark and colleagues, Stewe Jönsson, CPO, and Kerstin Caine-Winterberger, OT, presented a paper that discussed the prosthetist’s role in osseointegration. Brånemark and colleagues believe the prosthetist should take an active role in the osseointegration process. Prosthetists should supply the patient with an adequate prosthetic construction that guarantees the patient’s safety and never use an experimental construction that can risk the implant.
“In the case of osseointegration, the suspension/fixation is already ensured. The bone-anchored prosthesis always fits. It is attached correctly and is firmly held in place by the titanium implant,” the researchers wrote. “This eliminates all socket and harness related problems such as heat, sweating, chafing or discomfort. Change of the residual limb volume is not an issue and the prosthetist can spend more focus on the prosthetic function and component technology.”
Prosthetists also need to give the patient correct and relevant information on when they should and should not use a prosthesis, as well as follow prosthetic and rehabilitation protocols, including checkups. Most importantly, the prosthetist needs to listen to the patient. In the end, the addition of osseointegration as an option for amputees will provide another learning opportunity for prosthetists, no matter how long they have been in the industry.
“All levels of prosthetists and orthotists should be aware of osseointegration because they’re going to be the referral source and probably the source for referrals to surgeons or centers that are performing the osseointegration,” Bloebaum said.
Although some prosthetists may be eager to understand the workings of osseointegration, it does not mean that all prosthetists will be onboard with the technique.
“I think most prosthetists will be reluctant because they will feel threatened by it, but there will also be prosthetists who are on the cutting edge. There are some prosthetists who are aligning themselves with osseointegration, but it’s a small segment,” Alley said. “My advice would be to find your niche. [Osseointegration] is not going to take over the world yet. It is still going to be a limited application, but if you want to be a part of the cutting edge of things then it would be nice to start learning and reading more about osseointegration and how a prosthetist’s role is going to change based on the adoption of this technique.” — by Casey TingleA note from the editors: This story is an overview of the potential of osseointegration and some alternatives in O&P practice. It is not intended to be a comprehensive list of osseointegration or related procedures industry-wide.
Disclosure: Alley is the inventor of the High Fidelity Interface. Blunn is the co-inventor of ITAP. Brånemark has stock interest with Integrum, an implant system developer. Aschoff, Bloebaum, Caine-Winterberger and Jönsson have no relevant financial disclosures.