Osseointegration is a direct structural and functional connection between living bone and the surface of a load carrying implant. This implant is inserted into the bone during a surgical operation.
In simple words, it is a metal rod which has a very reliable direct connection with the bone.
Over the recovery period, bone grows onto implant increasing the strength and reliability of the connection.
Once this connection is reliable enough to load through, a prosthesis can be designed and fitted to the implant by your prosthetist.
In a traditional socket prosthesis, the artificial limb uses the surface of the stump as a connection. This connection can be very firm and controlled but will still have some movement between the underlying skeleton and the prosthetic socket.
You can experience this by gripping your arm and turning your wrist. No matter how hard you grip, your bones will still move under the skin and muscle.
An osseointegrated prosthesis has a direct connection to the skeleton which means that there is no movement between the prosthesis and the bone. This direct connection allows the user greater control over the prosthetic limb and provides a very simple and reliable fixation.
Due to this direct connection, a prosthetic socket is not required. By removing the socket, the skin and soft tissue are not subjected to the traditional forces experienced in a socket prosthesis.
As a result of this, the skin has a much lower risk of getting rubbed or over pressed by the prosthesis. With the skin uncovered, there are less issues with sweat retention and overheating of the limb. In addition, the donning process is also very simple.
The photo above demonstrates the process of connecting the prosthesis to the implant. In this situation, the patient is using an Alen key to secure the connection between the stump and the artificial leg. There a visible silicon umbrella which protects the stoma around the implant from getting damaged.
The photo above demonstrates a patient walking on an osseointegrated prosthesis.
The photo above demonstrates the range of motion of the artificial limb. It is visable that the prosthetic knee is only “naturally limited” by the human body rather than by a rigid socket.
When walking on a prosthetic limb, there are a lot of forces acting through the socket. In a socket prosthesis, all of these forces are partially absorbed by the soft tissue of the stump. This dulls the sensation of what surface they are walking on and how the mechanical parts of the prosthesis are working.
In an osseointegrated prosthesis, the direct connection to the bone heightens all of these sensations which can be uncomfortable if the incorrect componetry is used.
The most common forces that can cause discomfort and need to be accomodated for are vertical shock, rotation and, in above knee patients, terminal impact (caused by prosthetic knee).
To compensate vertical shock and rotation, torque and shock adaptors can be installed. Additionally, an appropriately designed modern foot can further reduce these forces.
Terminal impact is when the knee comes to a sudden stop with a visible and perceivable impact when fully straightening as it swings through.
To prevent uncomfortable terminal impact sensations, an appropriate knee unit with a hydraulic control specifically designed to prevent this impact is required.
The photo above demonstrates a prosthetic setup for an above knee osseointegrated prosthesis.
In the photo you can see an energy storing carbon fiber foot with a high range of motion, a shock and torque absorbing adapter and a prosthetic knee with hydraulic control to eliminate terminal impact.
If the forces acting on the prostheses get exessivly high and potentially dangerous for the patient, there is a safety device installed in the prostheses that will disconect it from the body and prevent serious injury.
Points to consider
When deciding on whither osseointegration is suitable or not, there are several considerations to keep in mind.
* Osseointegration is a surgical operation and it is important to discuss the risks with the surgical team.
* As there is a metal abutment protruding through the skin, there will be a permanent stoma on the stump which can increase the risk of infection. Because of this opening between the outside environment and your stump, a special cleaning regime is required to ensure proper hygiene of the stoma.
* Currently osseointegration is expensive. The specific cost and funding options are constantly changing and vary depending on individual cases.
Osseointegration is a very modern approach to prosthetics and has shown rapid development over a short period of time. For further information on your situation in relation to osseointegration, consult your GP and prosthetist. As a constantly evolving field of surgery and prosthetics we will continue to update ArtLimb with the most relevent information.
At the instance of our reader, we are publishing some more general views of the transfemoral stump.