DURACON® TOTAL KNEE SYSTEM |
Monogram® Knee Instruments*
following surgeons have contributed extensively to surgical
techniques associated with Duracon prostheses and Monogram
S. Borden, MD
of Adult Reconstructive Surgery
Cleveland Clinic Foundation, Cleveland, OH
T. Habermarin, MD
Department of Orthopaedic Surgery
Albert Einstein College of Medicine
Montefiore Medical Center
Albert Einstein College of Medicine, Bronx, NY
K. Hedley, MD, FRCS
Department of Orthopaedic Surgery
St. Luke's Medical Center, Phoenix, AZ
S. Hungerford, M.D.
Division of Arthritis Surgery
Professor of Orthopaedic Surgery
Johns Hopkins University, Baltimore, MD
Chief of Orthopaedic Surgery
Good Samaritan Hospital Baltimore, MD
A. Krackow, M.D.
of Orthopaedic Surgery
State University of New York at Buffalo
Department of Orthopaedic Surgery
Buffalo General Hospital, Buffalo, NY
publication sets forth procedural highlights for using Howmedica
devices and instruments. It offers guidance that you should
heed, but, as with any such technical guide, each surgeon
must consider the particular needs of each patient and make
appropriate adjustments when and as required. The surgeon
can refer to other Duracon publications for a more detailed
description of the surgical technique. Some of these references
Tibial Components Using Monogram Total Knee Instruments.
Duracon Primary Femoral and Patellar Components (with Stabilizer
Box Option) Using Monogram Total Knee Instruments.
Patent Nos, 4,550,448; 4,646,729; 4,653,488; 4,668,290; 4,714,468;
4,787,383; 4,825,857; 4,834,756; 4,944,756; 5,035,71)0; 5,192,324;
5,441,537; 5,541947; and US Design Patent Not. 273,894-95;
274,(NU-95; 274,161-62. Other Parents Pending.
goal of the Duracon® Total Knee System is to enhance durability
and minimize polyethylene wear through articular conformity
and balanced patellofemoral tracking. By increasing the conformity
and contact between femorotibial and patellofemoral articulating
surfaces, point contact stresses generally associated with
accelerated wear are reduced. And by achieving balanced, stable
anatomic tracking and normalized quadriceps and patellar tendon
tension, stresses that may also lead to accelerated wear are
implant design is critical, it is widely established that
instrumentation plays an important role in the success of
knee arthroplasty. To this end, Howmedica has developed the
Monogram® Knee Instrument System.
Monogram Knee Instruments are a hallmark series of instruments
which allow surgeons to customize total knee surgery to
Monogram Knee Instruments and the design of the Duracon
components work together to assure compatibility and ease
of transition throughout the range of total knee arthroplasty
cases: primary, stabilizer, and revision.
Monogram Knee Instruments promote accuracy efficiency, and
following pages present highlights of the Duracon surgical
technique, incorporating the Monogram instrumentation and
the Duracon components.
| FEMORAL PREPARATION |
of the Central Drill Hole
intercondylar drill guide and stepped drill are used to make
the initial intercondylar hole in the distal femur for the
distal femoral alignment guide and intramedullary rod (Figure
1). The hole should be placed approximately 0.5cm to 1cm
anterior to the origin of the posterior cruciate ligament.
the Distal Femoral Alignment Guide
intramedullary bushing is set for right or left knee at the
preoperatively determined valgus position. The locking knob
is tightened. The IM rod is slid into the bushing, and the
assembly is placed on the distal femur.
axial alignment tower and long alignment pin are attached
to the guide, and used to verify the position of the distal
femoral alignment guide relative to flexion/extension, varus/valgus,
and rotation (Figure 2).
the Cutting Jig
cutting jig is positioned on the distal alignment guide at
the 10mm resection level for most sizes. The cutting jig should
be set at the 12mm mark for the XL and XXL components. The
jig is secured with two 1/8" drill pins through the holes
marked "STD" (Figure 3).
distal femoral cutting jig permits +2mm incremental
adjustment. It has additional sets of drill holes for smaller
bones. It also provides a drill hole marked "X"
into which a drill pin can be placed to stabilize the jig
distal femoral cut can be made on the surface of the open
cutting jig or, alternatively, through the slots of the slotted
cutting jig (Figure 5).
confirming correct medial/lateral and rotational orientation
of the femoral positioning jig, the fixation pins are impacted
a neutral femoral cut, the neutral drill guide bushing is
inserted into the femoral positioning jig, and the 3/16"
holes drilled with a stepped drill (Figure 7a).
a 3° externally rotated femoral cut, the 3° drill
guide bushing is placed into the femoral positioning jig with
the word "left" or "right" indicating
the operative limb, facing the surgeon (Figure 7b).
femoral marking stylus placed on the femoral positioning jig
references the prominent aspect of the anterior cortex.
edge of the marking stylus identifies the appropriate size
of the femoral component. In this example, a medium component
is indicated (Figure 8).
the marking stylus indicator points to a scribe line, the
next larger block should be used to avoid notching the anterior
The marking stylus should only be used in anatomic
alignment, not with classical alignment.
determine the final component sizing, use the femoral
reference gauge. The gauge is placed in the two 3/16"
fixation holes previously made. Slide the femoral
sizing indicator or a .050" thick blade through
the slot(s) to choose the best femoral component size
and Chamfer Bone Cuts
All cuts made with the slotted blocks are done with a
.050" Howmedica sawblade. The block handles can be removed.
Monogram® Instruments provide three options for making
the final femoral preparation.
A - Ceramic Blocks
ceramic cutting blocks are designed to reduce blade-to-block
contact area. The combination of ceramic rails and reduced
contact area minimizes heat generation,+ provides
for extremely accurate cutting, and offers the potential for
reduced intraoperative wear debris. These blocks are available
in both open and slotted styles.
the impactor in place, impact the ceramic femoral cutting
block #1 into the previously made holes in the distal femur.
The impactor is removed and the sawblade is guided along the
rails of ceramic cutting block #1 to complete the anterior
chamfer cut and the resection of the posterior condyles (Figure
on file at Howmedica Osteonics.
femoral cutting block #2 is impacted onto the cut
femur. The previous cuts are visually checked for
accuracy. The anterior resection is made first on
block #2. The posterior chamfer is then resected (Figure
OPTION B - ABCTM
ABCTM cutting blocks and corresponding
chamfer blocks provide a unique method for making the four final
femoral cuts, utilizing surface blocks or "captures."
The blocks can be used with or without the capture mechanism.
(Capture mechanisms are not shown above.)
chamfer cutting block is used first. The A/P block is used next.
Both blocks are impacted into the holes previously made on the
distal femur before making the appropriate cuts (Figure 12).
are also available.
C - 4-in-1 Blocks
slotted 4-in-1 blocks provide a quick, guided mechanism
through which all four cuts can be made. The 4-in-1 block
is impacted into the previously made holes on the distal femur.
Drill pins can be used for additional stability. The cutting
sequence begins with the A/P cuts. The chamfer cuts are made
last (Figure 13).
a Duracon Stabilizer is to be used, the surgical technique
is identical to that of the primary component with the following
simple, final bone preparation steps. Place the appropriate
sized box guide on the distal femur in the previously prepared
holes. Use a 1/4" or 1/2" osteotome or .050"
Howmedica sawblade to make the initial square cut. Then use
the box chisel to finish the preparation (Figure 14).
using a Modular Stabilizer component, the stepped drill
finishes the distal holes to make room for the screws on the
modular box (Figure 15).
the Tibial Alignment Jig
are two options for the tibia: extramedullary referencing
alignment and intramedullary alignment.
A - Extramedullary Referencing
proximal tibial cutting assembly has two parts: the ankle
clamp and the proximal alignment guide. These are assembled
first (Figure 18). Then the tibial cutting jig is positioned
over the thin section of the proximal guide assembly shaft
slid proximally, and locked into position (Figure 16).
system offers a O° and a 2.5° tibial cutting jig.
If a 3° externally rotated femoral cut was made, the O°
tibial cutting jig should be used; or, if the neutral femoral
cut was made, the 2.5° tibial cutting jig should be used.
cutting jig, available in left and right configurations, is
designed to avoid soft tissue impingement (Figure 17).
long fixation pin of the proximal alignment guide is partially
seated in the proximal tibia to stabilize the assembly.
I extension alignment is correct when the long axis of the
assembly parallels the midcoronal plane of the tibia. Flexion
I extension alignment can be further confirmed by seeing that
the long axis of the assembly is parallel to the fibula. Distal
locking knob "A" is then tightened (Figure 18).
flexion/extension alignment defined, rotational alignment
is now established. Rotate the entire assembly so that a 1/8"
drill pin placed in the medial anterior pin hole of the ankle
clamp is parallel to the plane of the malleoli, oriented 25°
to the coronal plane (Figure 19).
offset can be adjusted using distal locking knob "B"
(Figure 20). The assembly is slid medially until the
jig shaft intersects the center of the tibia.
triaxial alignment is achieved, fully tighten the midshaft
locking knob. Fix the whole assembly in place by striking
the proxirnal end of the alignment rod with a mallet securing
the two fixation pins.
B - Intramedullary Referencing
5/16" hole is drilled in the location determined by the
preoperative X-rays (Figure 21).
pass the N rod into the canal, clearing the canal. Remove the
rod then reinsert it into the body of the N alignment jig. The
assembly is then inserted into the canal and the N rod is passed
into the canal until the isthmus is engaged (Figure 22).
the body of the IM jig resting on the proximal tibia, proper
rotational alignment is achieved by rotating the instrument
about the IM rod so that the tibial tubercle appears slightly
lateral to the vertical mounting bar. The headed nail is impacted,
fixing rotational alignment (Figure 23).
the appropriate tibial cutting jig (left or right) onto the
mounting bar, and lightly tighten the locking knob on the
face of the cutting jig. Attach the alignment handle to the
cutting jig, and slide a long alignment pin through the neutral
tibial "NT" alignment hole. When varus/valgus alignment
is correct the pin should be centered over the ankle.
varus/valgus adjustment is needed, locking knob "1"
is loosened. The mounting bar is pulled toward the surgeon,
and the jig is rotated until proper varus/valgus orientation
is achieved (Figure 24). Once the alignment pin is
centered over the ankle, the locking knob is securely tightened.
additional posterior slope is required (keeping in mind that
all tibial cutting jigs incorporate a 3° posterior slope),
loosen locking knob "2" and set the appropriate
level of slope. Once the correct slope is attained, securely
tighten locking knob "2" to set the final position
of the jig (Figure 25).
the Depth of the Tibial Cut
following applies to both extramedullary and intramedullary
tibial marking stylus attaches to the tibial cutting jig,
with the "9mm" end referencing the lowest level
of the rnidplateau on the unaffected compartment
(Figure 26). 9mm of bone will be resected. Altematively
if the 0mm end of the tibial marking stylus is used, the amount
of bone resected will be in line with the tip of the stylus.
1/8" drill pins are placed into the "N" [neutral]
holes, fixing the level of the tibial cutting jig. The extramedullary
ankle clamp and proximal alignment guide or the IM rod and
the intramedullary alignment jig are removed, leaving the
cuffing jig in place. If additional stability of the jig is
required, utilize the oblique "X" hole.
the Proximal Tibia
of the proximal tibia is now completed (Figure 27).
The pin puller is then used to remove the tibial cutting jig.
the appropriate size tibial template, and lock it onto the
tibial alignment handle. The short posterior tabs on the tibial
template help stabilize the template at the posterior cortical
surface (Figure 28).
alignment handle verifies rotational, varus/valgus, and flexion/extension
alignment (Figure 29). Rotational alignment is correct
when the drill bit placed in a hole from the previous step
parallels the handle (Figure 30). Varus/valgus and
flexion/extension alignment are verified with a long alignrnent
are located on the anterior face and the posterior surface
of the template. Headed nails or drills through these holes
may be used to temporarily fix the template.
proximal tibial template accepts the trial inserts for an
open trial reduction. The alignment handle may be left in
place and utilized for an open trial reduction, or the handle
may be removed to allow the template to serve as a trial for
a closed trial reduction. Trial baseplates are also available
when the scenario dictates their use.
the knee in 90° of flexion, the appropriate tibial trial
insert is carefully inserted into the proximal
tibial template. Forcing the trial spacer into place can cause
it to break. The trial femoral component is carefully impacted
onto the distal femur
the femoral trial component fully seated, the knee is carefully
extended, noting medial and lateral stability as well as overall
alignment in the A/P and M/L planes (Figure 31).
trial reduction has been completed, the femoral prosthesis
finishing holes are drilled through the trial component with
a 5/16" stepped drill (Figure 32).
Trials are available for add-on components (Wedges, Stem Extenders,
etc.), if required.
are several types of Duracon® femoral components:
Monolithic: Beaded and Non-Beaded
(pegs): Beaded and Non-Beaded
Stabilizer: Beaded and Non-Beaded
and Stem Extenders are also available for use with the appropriate
metal-backed and all-plastic Asymmetric resurfacing patellae
are part of the Duracon System. An all-plastic Symmetric Patella
for resurfacing and insetting applications is also available.
A bone-sparing Inset Patella without pegs is an additional
option (used with the Patellar Milling Instrumentation).
are two metal Baseplate designs: Universal and Cruciform.
Both designs have beaded and non-beaded styles.
of the A/P Lipped and Condylar styles work with both the Universal
and Cruciform Baseplates. The Stabilizer Inserts are used
only with the Universal Baseplate. An all-plastic Symmetric
Tibial Component is included in the system.
Extenders and Tibial Wedges are also available. Stem Extenders
work only with the Universal Baseplates.
bone screws can be used with the Universal Baseplate.
FINAL BONE PREPARATION
stem punch guide is placed in the corresponding locking holes
in the tibial template (Figure 33a). Attach the stem
punch to the sliding hammer assembly. The stem punch fits
into the cutout on the guide.
insertion/impaction, the stem punch must be maintained perpendicular
to the resected surface. Slowly impact the stem punch to allow
expansion of the bone (Figure 33b).
Universal stem punch plunger is inserted into the hole of
the stem punch. Impaction of the plunger creates a bone plug
at the stem tip (Figure 34).
Cruciform template, punch guide, and stem punch are used as
described in "Universal Baseplate" (Figure 35).
(The Cruciform Instruments are not the same catalog numbers
as the Universal Instruments.)
Cruciform Baseplate has no stem plug plunger.
A/P Lipped All-Plastic Tibial Component
tibia must first be prepared to accept the Universal Baseplate
(Figures 33a, 33b, and 34) prior to preparation for
the All-Plastic Component.
all-polyethylene stem compactor is used to enlarge the cutout
for the stem (Figure 36). Alignment perpendicular to
the cut tibia must be maintained. This provides space for
a cement mantle around the stem.
Stem Extenders Optional)
stem reamer guide is placed onto the Universal tibial template
after preparation for the primary stem. The distal locking
knob is tightened, securing the assembly (Figure 37).
the reamer guide assembly to the tibial template, and ream
with the bushing in place to the proper depth (Figure 38).
a situation calls for a Stem Extender, especially the
155mm length, it is recommended to use only the neutral
(0°) tibial cutting jig.
Tibial Bone Wedges (Optional)
wedge drill guide is attached by tightening the locking
knob to the anterior face of the tibial template.
Two 1/8" drill bits are placed through the guide.
The tibial wedge cutting jig is then placed on the
1/8" drill bits.
tibial wedge cutting jig allows accurate defect resection
to provide full bony contact for the configured component
tibial wedge cutting jig offers four options: a 12°
or 24° angled wedge resection, and a 5mm or 10mm
flat wedge resection (Figure 40).
Patellar Milling Instruments are
also available. Please refer to surgical technique
#6640-1-125. The following technique refers only
to resurfacing preparation
all osteophytes and synovial insertions around the
patella, and measure thickness using a caliper. After
determining the depth of the cut with a caliper, affix
the stylus in the appropriate slot to the patellar
resection guide, and capture the patella between the
jaws of the saw guide. Using a .050" Howmedica
sawblade, resect the patella (Figure 41).
the chosen patellar drill guide over the patella with
the handle perpendicular to the trochlear groove.
Drill three fixation holes with the appropriate stepped
drill (Figure 42).
of the Metal Tibial Component
utilized, Stem Extenders are screwed and tightened
on the Baseplate with the wrench instruments and are
torqued to 60-80in/lb; Wedges are cemented to the
the "feet" of the tibial impactor under
the posterior lip of the component.
the wing nut clockwise to secure the anterior lock.
the driver to impact the component. Ensure that the
undersurface of the component always remains
parallel to the cut surface of the tibia during insertion
implanting the baseplate with 6.2mm cancellous screws,
use a 1/8" drill bit and drill guide to create
the pilot holes (Figure 44a). Insert four screws
of a preoperatively determined length (Figure 44b).
Clear excess cement.
of the Plastic Insert
Once assembled onto the Baseplate,
the insert cannot be removed and reassembled. One-time
use only! To properly assemble the Tibial Insert to
the Baseplate, the Insert must be slid
fully posterior into the two posterior pockets of
the Baseplate before attempting to snap
down the anterior portion of the Insert (Figure
the Insert is slid fully posterior, snap down the
anterior locking tab by applying thumb pressure, or
by light impaction with the tibial insert impactor
(Figure 45b). Make certain that pressure is
applied in a distal-posterior direction. Once properly
assembled to the Baseplate, the Insert should not
be removed and reseated.
using the Stabilizer Insert, the locking screw must
be tightened to 60-80in-lb of torque after the plastic
insert has been snapped into the baseplate.
and hand tighten the screw using the adaptor handle
and the 4mm locking screw adaptor (Figure 46a).
Final tightening torque can be applied two ways: when
using the T-handled torque wrench (Figure 46b),
torque is applied in a clockwise direction until a
definitive drop in resistance is felt signifying the
pre-set torque level has been reached (between 60
and 80in-lb). When using the Cantilever torque wrench
(Figure 46c), apply tightening torque until
the indicator reads between 60 and 80in-lb. The baseplate
counter-wrench should be used with both methods to
apply an opposing force during tightening.
to tighten locking screw to 60-80in-lb may result
in screw loosening.
of the All-Plastic Tibial Component
the designated impactor to seat the All-Plastic Tibial
Component (Figure 47).
of the Femoral Component
Spacers, Stabilizer Boxes, and/or Stem Extenders are
secured with fixation pegs or screws.
using Modular Femoral Components, prior to implantation,
the modular fixation pegs or screws must be tightened
to the recommended torque of 60in-lb minimum
to 80in-lb maximum.
femoral impactor guides the femoral component and
ensures proper placement (Figure 48).