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Online ISSN 1827-1707
ADVANCES IN KNEE SURGERY LIGAMENT
Martucci E. A., Trisolino G., Bracci G., Gozzi E.
Sezione di Chirurgia Ricostruttiva Articolare di Anca e Ginocchio, Istituto Ortopedico Rizzoli, Bologna, Italia
The clinical outcome and survival of a prosthetic implant depends on several factors, such as surgical technique, materials’ quality and design of articular surfaces. The latter is specifically related to recent insights regarding articular kinematics. These showed that medial and lateral femoro-tibial compartments have a considerably different articular geometry. This leads to a flexion-extension movement (occurring about the trans-epicondylar axis) that is accompanied by a rotation around the vertical axis passing through the center of the medial tibial plate (tibial internal rotation) and a femoral condyle roll-back which is more prominent in the lateral compartment. It means that a medial-pivot mechanism is occurring, i.e., the convergence on the medial half of the knee between the lines connecting the medial and lateral condyle contact positions. A total knee arthroplasty that favors the medial-pivot mechanism must have an asymmetric surface of the tibial insert, so that the medial plate presents a high congruence with the femoral condyle to guarantee stability. On the contrary, the lateral plate must have a radius bigger than that of the lateral condyle to facilitate posterior roll-back and allow rotation movements between the components