- See:
-
TKR Menu
-
Distal Femoral Resection:
-
Femoral IM Alignment Rod:
-
Distal Femoral Sizing Guide (and
rotational alignment)
-
Anterior, Posterior, and Chamfer Cuts;
- Design Considerations:
- left & right vs universal designs, & contact area w/ patellar & tibial components;
-
depth of the patellofemoral groove:
- adequate depth of the patellofemoral groove to provide patellar stability w/o compromise of the
integrity of prosthesis or removal of excessive bone stock is important;
- raising the lateral wall of the patellar flange surface controls patellar tracking, but lowering of the medial side does not
prevent lateral subluxation, and therefore there is no mechanical advantage to lowering of the medial patellar flange;
-
proximal extent of anterior flange:
- adequate proximal extension of anterior flange minimizes chance that patella will ride off flange proximally in full extension;
- contact area of femoral condyles with the patella and the tibial plateaus;
- point and line contact suggest excessive contact stress, which may lead to excessive wear of tibial and patellar components;
-
coronal plane alignment: (see
distal femoral resection)
- in the coronal plane, the normal femoral condylar surface is oriented perpendicular to the hip-ankle axis (defined as the line joining
center of the hip and the center of the ankle joint (
anatomic axis of femur);
- however, the hip-ankle axis is not practicle, because of problem finding the center of the femoral head;
- appropriate axial alignment is assured by both intra & extramedullary guides;
- long cassette, single leg stance,
mechanical axis x-ray of leg allows
measurement of difference between anatomic & mechanical axis of femur;
- this measurement may be "dialed" into distal femoral cutting jig (which is located in the medullary canal), so distal femoral cut
may be made at right angles to the neutral
mechanical axis;
- Press Fit Condylar Design:
- femoral component of a total knee is subject to almost entirely to compressive stresses;
- consequently there have been very few reports of failure of the femoral component;
- optimum choice of materal relates therefore not to its strength, but rather to its ability to resist corrosion;
- fixation of femoral component has not been major problem w/ cemented or pressfit TKA, but load transfer can be an issue w/ pressfit component;
Determining the rotational alignment of the femoral component in total knee arthroplasty using the epicondylar axis.
The effect of femoral component position on the kinematics of total knee arthroplasty.
