Doctors differentiate between a unicondylar and a bicondylar sled prosthesis of the knee joint. A unicondylar sled prosthesis is a partial replacement of the knee joint, while a bicondylar sled prosthesis is a complete surface replacement of the knee joint. The unilateral sled prosthesis has several advantages over the bicondylar sled prosthesis. Here you will find further information and selected sled prosthesis specialists and centers.
The first attempts at knee joint endoprosthetics go back to the Berlin surgeon Gluck in 1890. The implant at that time was a hinged joint made of ivory and anchored using nickel-plated screws and a plaster-colophony putty. A total of 14 patients developed septic conditions (inflammation and poisoning).
The unilateral sled prosthesis was created for the treatment of monocompartmental medial or lateral knee osteoarthritis. In 1952, McKeever and Alliot developed a unicondylar tibial plateau prosthesis made of metal with a tibial anchoring groove.
In 1954, McIntosh from Toronto created an implant made of Vitallium, which was available in various thicknesses. Here, too, only the tibial defect was replaced. The main problem was the implant's tendency to dislocate.
In 1968, Gunston introduced a two-component sled prosthesis (metal-plastic), the Polycentric Knee. In this low-friction sled prosthesis, a semi-circular metal disk was implanted in the area of the femoral condyle. It moved in a correspondingly shaped tibial polyethylene block. It was anchored using bone cement. However, the results were unsatisfactory.
The principle of splint guidance was abandoned by the further development of Englbrecht in 1969. He developed a metal slide that was implanted in the area of the femoral condyle. The carriage had a point contact on a tibial polyethylene block.
This was a model with three degrees of freedom without constraint and with minimal positive locking of the contact surfaces. As the tibial component was only available in one size and thickness, extensive tibial bone resection was often necessary. This led to an accumulation of stress fractures.
This weakness of the first model of the St. George prosthesis was partially compensated for by a further development by Marmor in 1972. He developed a modular system with a true polycentric design and different tibial implants. Due to the material, problems arose primarily with the thinner tibial implants.
In the years that followed, the St. George and Marble prostheses underwent constant further development.
Knee pain, caused by osteoarthritis for example, affects many people in old age. A knee endoprosthesis is often necessary © Prostock-studio | AdobeStock
There are currently a large number of different unicondylar prosthesis models on the arthroplasty market. With one exception, the Oxford knee, the femoral bearing surface corresponds to an idealized condylar shape.
There are somedifferences in the
Unicompartmental knee joint replacement has the advantage over bicondylar replacement that
The disadvantage is a more demanding surgical technique, which may be associated with a higher revision rate.
The unicondylar sled prosthesis is considered a reliable treatment option for medial or lateral knee osteoarthritis.
Due to continuous improvements in materials and surgical techniques, prostheses are being retained in the body for longer and longer. For this reason, the indication for implanting a unicondylar sled prosthesis is also increasingly being discussed for young patients.
In addition to technical improvements, the surgeon's routine has a decisive effect on the result. There is a flat learning curve here. This is due, among other things, to the limited overview during implantation, which is usually minimally invasive.
Most of the sled prostheses used today have the following characteristics:
Anchoring is generally performed femorally using one or more pegs. Depending on the implant, cemented or cementless implantation is used. There are also cemented and cementless tibial variants.
The metal-back implants also generally require an anchoring fin. Pure polyethylene components, on the other hand, are cemented in using the so-called onlay technique.
In terms of the material used, the greatest advances in development have been in the areas of
processing and sterilization of polyethylene.
A unicondylar sled prosthesis is indicated in the case of
is indicated. The ligamentous apparatus must be intact.
Contraindications for the implantation of a unicondylar sled prosthesis are
After removal of the drainage, patients are allowed to bear weight postoperatively up to the pain threshold. They receive physiotherapy and an electric motorized splint (CPM).
Depending on their age and general condition, patients can walk without crutches after 2 to 4 weeks.
The advantages of minimally invasive implantation of a unicondylar knee joint replacement are that there is no disruption of the extensor mechanism. Postoperative pain is reduced, as are the formation of adhesions and the infection rate. With improved cosmetics, the range of motion is also better than with the conventional procedure.
The disadvantages are the possible misalignment of the components and the demanding surgical technique. These disadvantages can be offset by the use of a navigation system and robotics, which have been available to us for some time.
Contraindications for the implantation of a uniknee are
Further advantages of unicompartmental knee joint replacement compared to bicondylar replacement are
Patients with unicompartmental knee replacement have lower perioperative morbidity and improved mobility compared to patients who have undergone bicondylar prosthesis implantation.
Based on our mid-term results, it can be concluded that the use of the ligament tensioner results in stable knee joints in flexion and extension with correct alignment. The joint plane is restored and the surgical technique is reliable.
Due to the anatomical design of the prosthesis and the minimally invasive implantation, postoperative morbidity is lower. Only time will tell whether this surgical procedure is also suitable for younger and active patients.
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