smith&nephew RT-PLUS Surgical Technique page 43

Patellar Preparation
The leg is extended. Soft tissue on the posterior surface of the patella is exposed preserving
the ligaments.
If the posterior surface of the patella is not replaced, the patella is freed from osteo-
phytes and denerved.
After placing the patellar cutting guide on the patellar clamp with the ratchet, grasp the
patella with the clamp. The patellar thickness can be read from the mm scale on the handle.
Adjust the patella osteotomy insert (mm scale) to the height to be resected and resect the
patella with the oscillating saw (1 mm saw blade with unset teeth).
Note
When resecting, ensure that the saw blade does not wander, e.g., due to sclerotic bone sectors.
Positioning the patella clamp and
patella resection
The patellar instruments permit the use of
the "onlay" technique, in which 10 mm of the
bone are resected and replaced by a 10 mm
thick patellar implant (if an 8 mm thick patel-
lar implant is planned, resect just 8 mm ac-
cordingly).
An alternative option is the "inlay" technique,
in which the implant is partially countersunk
(3 mm to 5 mm). Here, the patella is only
resected approx. 7 mm to 5 mm below the
ridge. The thickness of the residual bony pa-
tella should not be less than 12 mm. See also
the "Milling" section on page 42.
Patellar size determination
Determine patellar size using the patellar
sizer. Supplied sizes are Ø 26, Ø 29, Ø 32
and Ø 35 mm. Note that the patellar compo-
nent is implanted with a slight medial offset,
thus matching the position of the natural
patellar ridge. Small implant sizes are recom-
mended for small patella to enable this offset
to be reproduced.
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