UNICAP knee mini-prosthesis: lighter, less invasive
For cases of early partial knee osteoarthritis, in young or old, but active patients, there is a new solution, less invasive than traditional knee prostheses or half-prostheses.
The function of UNICAP is to replace only the bearing surfaces of the knee, without affecting its overall architecture or its dynamics.
This prosthesis consists of 2 parts: the femoral implant, which is a polished steel pad fixed in the femur by a titanium screw, and the tibial implant, made of polyethylene (a kind of plastic), cemented in a tibial pocket.
For beginning wear of the internal (medial) compartment of the knee, the most frequently affected, one can thus choose to resurface only the femoral side, or also the tibial side.
The operation is done minimally invasively: first an arthroscopy is carried out, in order to properly inspect the articular surfaces, and to clean any remains of torn menisci. We can then decide whether to replace the femur only, or the femur and the tibia. In addition to the small arthroscopic "holes", a 3-4 cm incision is made.
Rehabilitation is done in full load from the first day, the mobilization of the knee in flexion and extension also starts on the first day with the help of a physiotherapist, and continues until good joint function is obtained, generally 3 to 4 weeks.
Example 1: 61-year-old man, mainly femoral wear:
Images in MRI before the operation:
above: X-ray images after the operation: on the left, we see the femoral "pad" from the front; on the right, we see it in profile, and we will notice the titanium screw which anchors the polished steel surface in the bone.
Example 2: 45-year-old man, wear on both sides of the joint.
MRI image before operation:
X-rays after the operation: the femoral pad is clearly visible; the tibial knob stands out less well, because it is transparent to X-rays.
The lifespan of these prostheses depends on the use made of them: it is better to avoid impact sports (running, football). In some patients this prosthesis may represent a definitive solution. In most cases however, it is a rather temporary solution, which makes it possible to "gain years" while waiting for a more radical solution such as a total knee prosthesis.