Does the tibial cut affect patellofemoral knee kinematics and pressure distribution in total knee arthroplasty with constitutional varus-alignment?
ESSKA Academy. Faschingbauer M. 11/09/19; 286391 Topic: G4 - Tricompartmental (Simple) arthroplasty
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Does the tibial cut affect patellofemoral knee kinematics and pressure distribution in total knee arthroplasty with constitutional varus-alignment?

EKA Free Papers

Topic: TKA

Faschingbauer M.1, Dürselen L.2, Seitz A.2, Hacker S.2, Reichel H.1
1University of Ulm, Orthopedic Surgery, Ulm, Germany, 2University of Ulm, Institute of Orthopedic Research and Biomechanics, Centre for Trauma Research Ulm, Ulm, Germany

Aims: In the current literature, there is some evidence that patients with constitutional varus-alignment treated with kinematic total knee arthroplasty (kTKA) show better outcome scores. The underlying kinematic changes are not yet described. The present study aimed to compare the effects of different tibial cuts, as used in kinematic alignment, on patellofemoral knee kinematics and pressure distribution, and to compare them with the natural knee joint, which has a constitutional varus-alignment.
Materials and methods: Seven cadaveric knee joints with constitutional varus-alignment were examined in the native state after implantation of a 0° Tibia-Cut cruciate retaining (CR)-TKA, 3° tibial cut CR-TKA, and 6° tibial cut CR-TKA in an established knee joint simulator. In a flexion movement, up to 100°, the effects on the patella-rotation, on the patellofemoral pressure conditions and the patellofemoral length ratios were determined. Also, the natural knee joint and the different tibial cuts in CR-TKAs were compared using Student´s t-tests.
Results: In the patellofemoral joint, the CR-TKA with the varus cut of 6° shows the highest similarity to the natural knee joint in the varus constitution. In contrast, the CR-TKA with varus-cut 0° disclosed the highest differences in the patellar kinematics.
The smallest difference to the natural knee joint concerning the patellar rotation shows the CR-TKA with a tibial cut of 6° (mean 0.4°), the most significant difference is found within the CR-TKA with 0° tibial cut (mean 1.7°).
Concerning patellofemoral pressure, the varus cut 6° is most similar to the natural knee joint and shows a mean difference of 3 MPa. The largest difference to the natural knee joint is indicated by the varus cut 0° with an average of 17.7 MPa (mean difference 8.1 MPa).
TKAs with 3° and 6° tibial cuts show a medialization of the patella, whereby the varus cut 6° has the highest values with a medialization of 4.5 mm at 90° flexion.
Conclusions: The improved outcome parameters in the kinematic alignment (up to 6 ° tibial cut) described in the literature could be based on similar kinematics in the patellofemoral joint. From a biomechanical point of view, however, the changed load distributions (as well as the probably associated wear problems and aseptic loosening tendencies) in the femorotibial joint continue to be taken into account and to be observed in long-term studies.
Does the tibial cut affect patellofemoral knee kinematics and pressure distribution in total knee arthroplasty with constitutional varus-alignment?

EKA Free Papers

Topic: TKA

Faschingbauer M.1, Dürselen L.2, Seitz A.2, Hacker S.2, Reichel H.1
1University of Ulm, Orthopedic Surgery, Ulm, Germany, 2University of Ulm, Institute of Orthopedic Research and Biomechanics, Centre for Trauma Research Ulm, Ulm, Germany

Aims: In the current literature, there is some evidence that patients with constitutional varus-alignment treated with kinematic total knee arthroplasty (kTKA) show better outcome scores. The underlying kinematic changes are not yet described. The present study aimed to compare the effects of different tibial cuts, as used in kinematic alignment, on patellofemoral knee kinematics and pressure distribution, and to compare them with the natural knee joint, which has a constitutional varus-alignment.
Materials and methods: Seven cadaveric knee joints with constitutional varus-alignment were examined in the native state after implantation of a 0° Tibia-Cut cruciate retaining (CR)-TKA, 3° tibial cut CR-TKA, and 6° tibial cut CR-TKA in an established knee joint simulator. In a flexion movement, up to 100°, the effects on the patella-rotation, on the patellofemoral pressure conditions and the patellofemoral length ratios were determined. Also, the natural knee joint and the different tibial cuts in CR-TKAs were compared using Student´s t-tests.
Results: In the patellofemoral joint, the CR-TKA with the varus cut of 6° shows the highest similarity to the natural knee joint in the varus constitution. In contrast, the CR-TKA with varus-cut 0° disclosed the highest differences in the patellar kinematics.
The smallest difference to the natural knee joint concerning the patellar rotation shows the CR-TKA with a tibial cut of 6° (mean 0.4°), the most significant difference is found within the CR-TKA with 0° tibial cut (mean 1.7°).
Concerning patellofemoral pressure, the varus cut 6° is most similar to the natural knee joint and shows a mean difference of 3 MPa. The largest difference to the natural knee joint is indicated by the varus cut 0° with an average of 17.7 MPa (mean difference 8.1 MPa).
TKAs with 3° and 6° tibial cuts show a medialization of the patella, whereby the varus cut 6° has the highest values with a medialization of 4.5 mm at 90° flexion.
Conclusions: The improved outcome parameters in the kinematic alignment (up to 6 ° tibial cut) described in the literature could be based on similar kinematics in the patellofemoral joint. From a biomechanical point of view, however, the changed load distributions (as well as the probably associated wear problems and aseptic loosening tendencies) in the femorotibial joint continue to be taken into account and to be observed in long-term studies.
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