Patent Application
20050043807
1. Field of the Invention
The invention pertains to prosthetic knees and more particularly to a two-thirds prosthetic knee, having a single condyle in a prosthetic patello-femoral joint.
2. Description of Related Art
The distribution of articular cartilage damage in the osteoarthritic knee is variable. It may involve one, two or all three compartments of the knee. Although unicompartmental tibio-femoral and unicompartmental patello-femoral partial knee replacements are available, combinations of two compartment replacements are not.
With increasing pressure towards minimally invasive surgery the concept of only replacing the diseased compartments is attractive. Accordingly there is a need for combinations of either the patellofemoral and medial tibiofemoral joint or patellofemoral and lateral patelofemoral joints respectively.
It is an object of the invention to provide a device comprising a prosthetic femoral component having a single condyle and a trochlear groove for the patella.
Methods of surgical implantation of this device are disclosed.
For a more complete understanding of the present invention and for further advantages thereof, reference is now made to the following Description of the Preferred Embodiments taken in conjunction with the accompanying Drawings in which:
As shown in
The present invention is depicted by way of example in
Aspects of the invention are based on the premise that there are distinct benefits obtained if only diseased compartments are replaced. A patient that receives a prosthetic of the type depicted in
The principle of closely matching surgery to preoperative MRI mapping of articular cartilage damage is a principle of surgical planning for the two-thirds knee.
MRI evaluation cannot only evaluate the distribution of cartilage damage, but also size match the native tibial and femoral components to prosthetic implants. The femoral and tibial orientation, in terms of rotation and joint line level and slope and the orientation of the patellar centrum can be calculated using CT scanning. Following thorough clinical evaluation imaging and preoperative planning, a minimally invasive surgical approach may be considered and the smaller size of both femoral and tibial components will facilitate this. An antero-medial or antero-lateral approach may be used to match the tibio-femoral compartment to be replaced.
Following incision and capsulotomy some ligament balancing may be done before the tibial cut. For example the deep medial collateral ligament may be released if the medial compartment is to be replaced or the ilio-tibial band if the lateral compartment is to be replaced. The tibial cut should preferably be done first with standard extramedullary jigging or by computer assisted navigation if preferred. This will facilitate the first, distal femoral cut. Bone from the two aforementioned cuts is removed to permit closed cuts or reaming with an angled guarded saw or reamer over customized jigs. With bone removed following the single tibial and femoral cuts there is more space to perform an accurate patellar preparation.
Although the components may be cemented or uncemented, it is preferred that cement be used. The two-thirds knee obviates the problem of cement retrieval from remote parts of the prosthesis, a current problem in minimally invasive total knee replacement.
Care must be exercised to ensure a smooth transition between the retained femoral condyle and the prosthesis. Kinematic evaluation may be done following implantation.
While the present invention has been described with reference to particular details of construction, methods and procedures, these should be understood to be provided by way of teaching examples and not as limitations to the scope or spirit of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003904379 | Aug 2003 | AU | national |
