- See:
- Internal Rotation of Knee Joint:
- Rotation of Tibial Component:
- Correct Rotation:
- as a general rule, the tibial componenet should be aligned such that it points to the medial third of the tibial tubercle;
- correct rotational positioning of tibial component is best achieved by by aligning intercondylar eminennce of tibial component w/ tibial
crest in the saggital plane;
- in making tibial cuts, care must be exercised when using such system because of the asymmetry of the plateaus;
- AP length of the medial condyle is considerably larger;
- Tendency for Internal Rotation:
- tendency to internally rotate tibial cut is present in many systems becuase of laterally dislocated extensor mechanism & physical
retraction by assistant tends to externally rotate flexed tibia;
- internal rotation of cut is be avoided particularly in systems that incorporate a significant Posterior Slope, because this will produce a
lateral tilt;
- jig systems fitted to anterior surface of proximal tibia will have tendency to align in excessive internal rotation because of everted patella
tendon laterally;
- 2 mechanisms can be used to avoid this tendency to internal rotation;
- look down on tibial plateau and cutting jig w/ knee in flexion;
- face of jig should be parallel to the plane of femoral condyles;
- Effect on Patella:
- internal Rotation of tibial component is a common error, & causes lateral displacement of tibial tubercle, which increases Q angle and
increases the risk of patellar instability & dislocation;
- medially rotated tibial & femoral components have a high incidence of assoc postop patellar dislocation