Most patients who suffer a leg amputation above the knee and are fortunate enough to get a prosthetic lower leg usually use traditional “socket” hardware to attach it to their upper thigh. The prosthetic itself must fit snugly over the stump and is then held in place by suction or a suspension mechanism system. This approach often causes blisters and infections due to rubbing and poor fits. It can also be difficult for patients to walk on it naturally due to pressure.
An alternative method to socket attachments has recently been tested at Radboud University in the Netherlands, though it’s been around for more than 30 years. Known as osseointegration, it is a more invasive process that involves anchoring a 14-cm steel rod in the femur (thigh bone). After a few weeks of healing, the pin grows into the bone and an adapter is attached. It protrudes a few centimeters through the skin via a stoma, a surgically created re-usable hole through the skin. Patients attach their prosthetic to the attachment using a simple coupling.
Some patients have minor problems with the stoma, mainly infections, but they can usually be treated with simple measures. And the implanted connection permanently improves the patient’s mobility and quality of life.
Bone-anchored prostheses offer a number of important advantages. In a five-year study of 42 patients at Radboud University, 77% endured infections, but they were mostly superficial and ceased after the first two years. Most of the infections (95%) were mild to moderate and did not require surgical treatment. About a third of the patents had irritation around the stoma where the pin protrudes through the skin. They underwent minor surgery to re-shape the soft tissue.
On the positive side, patients increased the number of hours per week they could use their prosthesis, going from an average of 56 hr. with socket prosthetics to 101 hr. with the bone-anchored alternative. The bone-anchored prosthetic also improved health-related quality of life (HRQoL). On a 100-point scale, the average score increased from 33 to 75.
Other benefits include more natural and stable control of the prosthesis; better walking and sitting; and avoidance of the many problems associated with the sleeve prosthesis, such as blisters. The next steps in clinical research, according to the doctors who did this study, should be to look at improving the stoma.