- 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, becuase
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;
