
Zimmer MIS Multi-Reference 4-in-1 Femoral Instrumentation Surgical Technique
33
Step Eight
Perform a Trial Reduction
After preparing the tibia, select the
appropriate Pegged or Stemmed Tibial
Sizing Plate/Provisional that provides
the desired tibial coverage. Check the
size matching chart (for the style of
NexGen
Knee implant) for component
matching instructions.
Insert the Femoral Provisional, Patellar
Provisional, Tibial Sizing Plate/
Provisional, and Articular Surface
Provisional.
Flex and extend the knee with the
provisionals in place. Check the range
of motion and ligament stability.
Perform any necessary soft tissue
releases. With proper soft tissue
balancing complete the tibial
component tends to seat itself in
the position where it best articulates
with the femur (Fig. 8a)
NOTE:
During the trial reduction,
observe the relative position of the
Femoral Provisional on the tibial
Articular Surface Provisional by using
the lines on both provisionals. The
lines can be used to determine if
posterior rollback is occurring, whether
the PCL is functional, and if the femoral
component will contact the tibial
articular surface in the proper location.
If the PCL is properly balanced, the
Femoral Provisional should sit near
the anterior or center lines on the
tibial Articular Surface Provisional in
extension and near the posterior line
in flexion.
If the Femoral Provisional sits
posterior to the lines, the PCL may be
too tight or the articular surface may
be too thick. If the Femoral Provisional
sits anterior to the lines, the PCL may
be too loose.
After this self-centering process has
occurred, mark the position of the
component with methylene blue or
electrocautery (Fig. 8b). Then remove
the provisional components. The
Femoral Extractor can be used to
remove the Femoral Provisional.
Fig. 8a
Fig. 8b
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