Does Kinematic Alignment and Flexion of a Femoral Component Designed for Mechanical Alignment Reduce the Proximal and Lateral Reach of the Trochlea?

作者：Brar Abheetinder S; Howell Stephen M^*; Hull Maury L; Mahfouz Mohamed R

来源：Journal of Arthroplasty, 2016, 31(8): 1808-1813.

DOI：10.1016/j.arth.2016.01.040

• knee arthroplasty
• proximal and lateral reach of trochlea
• kinematic alignment
• flexion of femoral component
• trochlea

Background: Kinematically aligned total knee arthroplasty uses a femoral component designed for mechanical alignment (MA) and sets the component in more internal, valgus, and flexion rotation than MA. It is unknown how much kinematic alignment (KA) and flexion of the femoral component reduce the proximal and lateral reach of the trochlea; two reductions that could increase the risk of abnormal patella tracking.
Methods: We simulated MA and KA of the femoral component in 0 degrees of flexion on 20 3-dimensional bone models of normal femurs. The mechanically and kinematically aligned components were then aligned in 5 degrees, 10 degrees, and 15 degrees of flexion and downsized until the flange contacted the anterior femur. The reductions in the proximal and lateral reach from the proximal point of the trochlea of the MA component set in 0 degrees of flexion were computed.
Results: KA at 0 degrees of flexion did not reduce the proximal reach and reduced the lateral reach an average of 3 mm. Flexion of the MA and KA femoral component 5 degrees, 10 degrees, and 15 degrees reduced the proximal reach an average of 4 mm, 8 mm, and 12 mm, respectively (0.8 mm/degree of flexion), and reduced the lateral reach an average of 1 mm and 4 mm regardless of the degree of flexion, respectively.
Conclusion: Arthroplasty surgeons and biomechanical engineers striving to optimize patella tracking might consider developing surgical techniques to minimize flexion of the femoral component when performing KA and MA total knee arthroplasty to promote early patella engagement and consider designing a femoral component with a trochlea shaped specifically for KA.

• 出版日期2016-8