Відео

BRILLIANT

Thank you very much. Very useful in visualizing various axes

nice study. What is the computational platform that was used in this study?

VIRTUAL CONSTRAINT TESTING METHODS Surgically positioned components settle in a natural manner under compressive force. The femoral component is rotated and settles into various flexion angles of interest, that serve as starting points for later testing. The extents of constraint are explored, and the middle position between them is selected as the starting point for subsequent constraint testing. The arrows at the top indicate the restraint of the femoral component, red is locked and green moves freely in the inferior-superior and varus-valgus directions, for all tests. The arrows at the bottom indicate the restraint of the tibial insert, red is locked, green moves freely and yellow is the direction that it is being driven in.

THE INFLUENCE OF MECHANICAL VERSUS KINEMATIC ALIGNMENT ON KNEE DESIGN PERFORMANCE DURING WALKING GAIT We utilized KneeSIM, a computational kinematic knee simulation software to evaluate the long term outcomes of Stryker Triathlon CR components during the activity of walking gait. KneeSIM results in measurements of component motions and patella tracking that are associated with patient satisfaction, and contact forces and articular wear paths that are associated with implant longevity. Two surgical procedures were followed, the classic Mechanical Alignment and the more recently performed Kinematic Alignment. Mechanical alignment, on the left, places the components perpendicular to the vertical mechanical axis while kinematic alignment, on the right, places the components parallel to the transverse flexion extension axis which follows the inclination of the natural joint line in the AP view. These two approaches result in different bone resections, placing the TKA components in two different orientations, mechanical aligned in blue, kinematically aligned in orange. Two different KneeSIM models were created, one for each case. Different reference axes are used in mechanical versus kinematic alignment. A vertical midplane axis perpendicular to the floor is moved to coincide with the geometric center of the ankle joint. The mechanical axis is typically three degrees from the vertical axis. The mechanical axis is difficult to directly visualize in the surgical theater, however, there are many methods of indirectly determining its location. One of these, the transepicondylar axis, determines the placement of saw guides that create bone resection planes that are perpendicular to the mechanical axis. Kinematic alignment seeks to restore the joint line to the individual patient’s pre-diseased state, referencing the flexion-extension axis. This imaginary line passes through the geometric centers of each posterior femoral condyle. Equal resection, allowing for cartilage wear and saw kerf, of the distal femur and posterior condyles ensure that the resection surfaces are parallel to the flexion-extension axis. When the thickness of the implanted femoral component matches the resected bone fragments, the patient’s estimated healthy cartilaginous surface anatomy would be restored. The proximal tibial bone is resected to restore the individual patient’s original varus and posterior slope. The axial rotation of the tibial component aims to closely match the axial rotation of the femoral component. The kinematic alignment flexion-extension reference axis and bone resection planes (in orange) may be compared to those of the classic mechanical alignment surgical procedure (in blue). AP views and axial views are provided for clarity. On average, the kinematically aligned femoral component is 6 degrees more flexed, 3 degrees more valgus and 4 degrees more internally rotated than the mechanically aligned femoral component. The kinematically aligned tibial insert closely followed the femoral component, 3 degrees more varus and 4 degrees more internally rotated. There were minimal differences between the mechanical and kinematic aligned results of both femoral and patellar component motions, contact articulations and forces. Average absolute differences over the stance phase of walking gait were less than 2 mm, 2 degrees and 200 Newtons for all results recorded. Tibial-femoral articulations had different loading profiles across the medial and lateral compartments during stance, however, no clear trend was discernible between the surgical procedures. The motion of the kinematic aligned femoral component (in orange) can be observed during walking gait. The orange jack is rigidly attached to it, allowing a simplified representation of its motion for easier comparison to the mechanically aligned femoral component jack (in blue). The progression of tibial-femoral contact areas in both the medial and lateral compartments can also be compared, kinematic alignment in orange, mechanical alignment in blue. No functional difference was found between mechanical and kinematic alignment surgical procedures during the walking gait cycle with Triathlon CR TKA components. Other product designs that are asymmetrical, single radius or offer greater articular conformity than the Triathlon CR design may yield different results.