One way of fixing a prosthesis to the body is to use an osseointegrated bone-anchor. This is a relatively new way of fixing a prosthesis.
Osseointegration is when certain materials are accepted by the bone as part of itself rather than as a foreign body. Once integrated, the implant will not easily loosen and can then be used as a permanent anchorage point fixed in the bone. Only titanium or titanium-containing alloys can be integrated into the bone in this way. The prosthesis can then be fixed to the anchorage point (for example, by using a magnet).
At the Royal Free Hospital, we routinely insert bone-anchors for prosthetic fingers, eyes, noses and ears. However, although the surgery to insert the bone-anchor is fully funded, we are not always able to fund the cost of the prosthesis that is attached to the bone-anchor.
The use of bone anchors to treat major limb amputees (either upper or lower) is currently not funded by the NHS. However, NHS England is continuing to monitor the data on outcomes from all the types of implants in current use and has indicated that this policy may change in the future.
What disadvantages are there with bone-anchored implants?
Patients need to undergo further surgery (sometimes more than one procedure) to insert a bone-anchor after their initial surgery to remove the diseased part (eg after amputation of a limb). Many patients will have already endured multiple, painful, surgical procedures and may be reluctant to undergo more surgical procedures to insert a bone-anchor, despite its advantages.
There is also a risk of infection in the skin around the implant and in the bone. In most cases, patients only experience minor infections which can be easily treated with oral antibiotics. However, in rare cases, the infections can become more persistent and severe. If this happens it may be necessary to remove the bone-anchor altogether to allow the infection to clear.
Patients must put up with a change in the long-term appearance of the treated part to accept the presence of a piece of metal permanently protruding from the skin. Some patients find it very difficult to adjust to this change in their appearance, but most accept it as the price they must pay to achieve their reconstructive goals.