Medacta GMK Sphere - Posterior Cut, Anterior Cut and Chamfers; Femoral Upsizing;Downsizing

GMK Sphere Calipered Kinematic Alignment Surgical Technique
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4.3 POSTERIOR CUT, ANTERIOR CUT AND
CHAMFERS
When the 4in1 cutting block has been stabilized via either
the posterior referencing pegs or posterior referencing pins,
perform the posterior condylar cut.
VERIFICATION CHECK
Using the dedicated caliper, check the thickness of the
resected medial and lateral posterior femoral bone and
cartilage (if present) resections. Measurement on the
unworn condyles should read 7.0 ± 0.5 mm. Worn condyles
should measure 5.0 ± 0.5 mm. These values equal the 8
mm thickness of the posterior condyles of the GMK Sphere
femoral component after compensating for the ~1 mm
kerf of the saw blade and 2 mm of cartilage wear when
present.
If needed, refine the cut through the slot of the 4in1 block.
In the rare event a 2 mm recut is necessary, reposition the
block using the posterior referencing pins.
If the posterior referencing pegs were used, position the
two central pins on the row of holes marked with a line.
Remove the cutting block, withdraw the two pegs and
reposition the pin holes just below the reference line.
If a 1 or 2 mm washer was used, place an angel wing
between the 4in1 block and the bone on the over-resected
condyle.
Perform the remaining femoral resections as follows:
•
Anterior cut
•
Posterior chamfer
•
Anterior chamfer
CAUTION
All femoral resections must be performed using a saw
blade 13 mm wide with a maximum thickness of 1.27 mm.
Remove the fixation pins, pegs and/or screws and then
remove the 4in1 block.
4.4 FEMORAL UPSIZING/DOWNSIZING
The difference between successive femoral sizes is 2 mm
in both anterior-posterior and medio-lateral dimensions.
Option 1: Posterior Pegs
Replace the 4in1 block with a more suitable size using the
posterior peg holes.
CAUTION
In the event downsizing is necessary, the anterior resection
level will move 2 mm posteriorly. Use an angel wing to
check this adjustment and ensure the downsized 4in1
block cuts will not result in anterior notching of the femur.
Option 2: Posterior Referencing Pins
If the 4in1 cutting block was positioned using the central
parallel pins, replace the cutting guide with the more
suitable size using the same row of pin holes.
CAUTION
In the event downsizing is necessary, the anterior resection
level will move 2 mm posteriorly. Use an angel wing to
check this adjustment and ensure the downsized 4in1
block anterior cut will not result in anterior notching of the
femur.