Stryker Orthopaedics would like to thank
Dr. Masini for his help in developing the
Scorpio Trial Cutting Guide.
Michael A. Masini, MD
Ann Arbor Bone and Joint Surgery
St. Joseph Mercy Hospital
Ann Arbor, MI
Clinical Instructor in Orthopaedic Surgery
University of Michigan
Ann Arbor, MI
Introduction
This surgical protocol is a supplement
to the Scorpio Total Stabilizer Revision
Knee System Surgical Protocol
(Lit No. LSTS/ST).
The Scorpio Trial Cutting Guide is an
intramedullary based instrumentation
system focused on the restoration of the
joint line and proper flexion-extension
gap assessment.
1
Tibial and Femoral Canal Preparation
Scorpio Trial Cutting Guide
Tibial Preparation
Prepare the tibia following the Scorpio
Total Stabilizer Revision Knee System
Surgical Protocol (Lit. No. LSTS/ST, pages
1- 5). If an offset is needed, use the tibial
offset reamer to prepare for the tibial
offset. Insert the assembled trial into the
tibia (Figure 1 and Figure 2).
Note: The Scorpio Trial Cutting
Guide (TCG) is designed for use
with its own mating tibial insert
trial. The trial insert does not have
a post to allow for more accurate
assessment of the ligaments
during surgery.
Femoral Canal Preparation
Prepare the femoral canal to accept a
stem as described in the Scorpio Total
Stabilizer Revision Knee System Surgical
Protocol (Lit. No. LSTS/ST, page 5). If an
offset is needed, use the femoral offset
reamer to prepare for the femoral offset
(Lit. No. LSTS/ST, page 9) (Figure 3).
Figure 1Tibial Canal PreparationFigure 2Tibial Trial Assembly and
Insertion
Femoral Offset Reamer
8200-0095
Reamer Depth Stop
8200-0047 80mm stem with offset
8200-0048 155mm stem with offset
The Scorpio Trial Cutting Guide (TCG)
can be assembled for either a left or right
knee. Assemble the offset adapter into the
housing of the TCG so the offset adapter
is pointing to the appropriate left or right
orientation (Figure 4).
Figure 4Trial Cutting Guide in “Right” Orientation
Assemble the trial cutting guide, offset
adapter, and appropriate size trial stem
as shown (Figure 5).
A neutral offset adapter may be used
initially to construct the trial cutting
guide assembly until the need for a
femoral offset is determined.
First, assemble the trial stem to the offset
adapter, then assemble the offset adapter
into the Trial Cutting Guide housing and
secure the anterior set screw. Once “finger
tight” pressure is achieved, rotate
counterclockwise 1/2 turn to allow the
offset adapter to rotate freely. The anterior
set screw will be fully secured after the
appropriate offset and rotation is
determined (Figure 6).
Note: Rotating counterclockwise
1/2 turn will allow the offset
adapter to rotate freely without
disassembling from the Trial
Cutting Guide housing. Rotating
counterclockwise more than 1/2
turn will cause the offset adapter
to fall out of the Trial Cutting Guide
housing.
Note: Femoral chamfer cuts cannot
be made with the TCG. However, if
bone loss is minimal and it is
determined that chamfer cuts are
required, the Scorpio Total
Stabilizer (TS) All-In-One Cutting
Block may be used to make
chamfer cuts (Lit. No. LSTS/ST,
Page 8).
Joint Line Restoration
Insert the TCG into the femoral canal
(Figure 7) and align the TCG medial
epicondyle (ME) scribe line reference mark
with the medial epicondyle (Figure 8). The
ME scribe line is 28mm from the distal
surface of the TCG. When the ME scribe
line is in line with the medial epicondyle,
the distal surface of the TCG will be
approximately located at the joint line.
(The joint line can also be estimated
using pre-operative radiographs and
anatomic landmarks.)
Figure 7TCG Femoral Canal
Insertion
ME Scribe
Medial
Figure 8Joint Line Restoration to
Medial Epicondyle
Place an initial fixation pin in the middle
of the medial slot on the TCG (Figure 9and Figure 10). Pinning the medial slot
will fix the proximal/distal position while
allowing for slight internal and external
rotation of the TCG.
There are several ways to determine the
proper femoral offset required.
1) Start with a neutral offset and measure
or estimate the distance from the
inferior surface of the anterior flange
of the TCG to the anterior femur
(Figure 11) or,
2) Line up the femoral sizing “C” templates
with the trial stem and measure or
estimate the distance from the anterior
femur to the inferior surface of the
anterior flange of the TCG.
Note: A 4mm offset is typical for
many revision scenarios, and if an
A/P offset is not necessary, the
offset adapter may be used to
displace the femur medially or
laterally.
Note: When adjusting the offset of
the TCG, the entire offset adapter
and stem construct will be rotating.
To adjust the offset, insert the hex driver
into the distal face of the offset adapter
and rotate (Figure 12). After final offset
position has been determined, tighten the
anterior set screw to secure the offset
position on the TCG (Figure 6, page 4).
If an offset is required, record the final
position of the offset by reading the
location of the hash mark on the offset
adapter relative to the clock face on the
TCG. The clock recording will be
required when assembling the implant. If
an offset is not required, use the 0 adapter
(Figure 13).
Note: The numerical clock on the
TCG is a mirror image of the clock
face markings on the femoral trial
and final implant (Figure 14 and
Figure 14a).
Figure 13Offset ReadingFigure 14Trial Cutting Guide and
Implant/Trial Clock Face
Figure 14AEnlarged View of Clock
Face (0=Posterior Offset)
Femoral Sizing Template
8200-0096 #3/5
8200-0097 #7/9
8200-0098 #11/13
6
Trial Cutting Guide Orientation (continued)
Scorpio Trial Cutting Guide
Preliminary Trial Assessment
With the joint line restored and the
appropriate offset determined, a
preliminary trial assessment should be
conducted with the trial tibial
components in place (Figure 15).
Select the appropriate trial tibial insert
and place it onto the trial tibia. Select the
insert that provides varus/valgus stability
in full extension (Figure 16).
Figure 15Preliminary Trial Assessment
Figure 16Varus/Valgus Stability Check at Full Extension
7
Trial Cutting Guide Orientation (continued)
Scorpio Trial Cutting Guide
Rotation
With the knee flexed at 90°, appropriate
external rotation can be set by
positioning the TCG on the tibial trial
insert so that it is seated with no
varus/valgus tilt. The transepicondylar
axis or Whiteside’s axis can be used to
estimate rotation as well.
A second headless fixation pin should
then be placed in the TCG’s anterior pin
hole to fix the TCG position once
rotation has been established (Figure 17).
Place as many pins as necessary to
securely fix the TCG on the distal femur.
Note: Headless pins may now be
replaced with short headed fixation
pins to facilitate joint reduction.
Note: The TCG trial inserts do not
have a post. This allows for a more
accurate assessment of the
ligaments during trialing.
Figure 17Second Fixation Pin – Rotation
Headed Fixation Pin
7650-1136 1” Headed Pin
7650-1137 3” Headed Pin
8
Trial Cutting Guide Orientation (continued)
Scorpio Trial Cutting Guide
Trial Assessment
Once the TCG is fixed to the femur, a
trial reduction may be conducted. Reduce
the extensor mechanism and patella. The
inferior pole of the patella should rest
approximately 14mm above the joint line
with the knee in 90° of flexion unless
patella baja or patella alta was present
pre-operatively. Tracking of the patella
can then be assessed (Figure 18).
Note: A suture or towel clip may be
used to facilitate reduction and
trial assessment (Figure 19).
It should be noted that the flexion gap
often feels “too loose” in the revision
situation even when the appropriately
sized femoral implant is positioned at the
joint line. Using the TCG gives the
surgeon the unique opportunity to upsize
the femoral component and offset the
next size femur to selectively fill the
flexion gap that feels “too loose.”
However, if upsizing results in poor
tracking and “overstuffing of the joint”,
the surgeon need only return to the
previous size TCG and offset.
Note: A full evaluation of stability
and range of motion can be
performed before making any
resections on the distal femur.
Adjustment of the implant position
and size is possible before making
any femoral bone cuts.
Figure 18Preliminary Trial Reduction
Suture
Figure 19Preliminary Trial Reduction With Suture
9
Femoral bone Cuts
Scorpio Trial Cutting Guide
Note: A Stryker 152 saw blade
(narrow-thick) or a reciprocating
saw blade are recommended for
augment cuts and the box cut.
Augment Cuts
With the TCG properly positioned,
visually determine the appropriate
posterior and distal resections required
(Figure 20 and Figure 21). A blade
runner may be used to assess the level of
resection if necessary. The appropriate cut
is selected by resting the blade on the
surface of the TCG apertures that will
provide a clean up cut.
Note: If an augment cannot
effectively “fill the gap,” i.e.,
deficiencies greater than 15mm
distally or 10mm posteriorly, a
bone graft may be required
(Figure 22).
When making the box cut, cut along the
outer sides of the box guide and cut
completely through the femur (Figure 23and Figure 24). The posterior portion of
the proximal box cannot be completed
due to the presence of the stem. Complete
the proximal posterior box cut after the
TCG has been removed using the initial
resection as the guide.
Note: The sides of the box may be
completed with a distal approach
(Figure 25) in addition to the
anterior approach.
A final trial assessment should be
conducted with the Scorpio TS trial
femoral components to verify the
accuracy of the cuts and that the offset
has been properly recreated (Figure 26).
See the Scorpio Total Revision Knee
System Surgical Protocol (Lit. No.
LSTS/ST, page 10) for details on trial
assembly and trial reduction.
A surgeon must always rely on his or her own professional clinical judgment when deciding whether to use a particular
product when treating a particular patient. Stryker does not dispense medical advice and recommends that surgeons be
trained in the use of any particular product before using it in surgery.
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trademarks or service marks: Scorpio, Stryker. All other trademarks are trademarks of their respective owners or holders.