biomet assent
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The Ascent™ Total Knee System is taking total knee replacement to new heights by
building on over twenty years of clinical experience. One thing has become clear in
total knee replacement: surgeons need and want several choices for their patients.
Surgeon choice is critical and may be the most important factor in long-term patient
satisfaction. Biomet responded to this need by combining its clinical experience,
extensive engineering resources, and the clinical experience of Rick Bassett, M.D.
and Michael Jacobs, M.D. The combination of these resources provides Biomet’s
surgeon customers with a clinically proven, user friendly system: the culmination of
experience from the most responsive company in orthopaedics. The goals of the
Ascent™ Knee System are to:
• Incorporate design features of proven Biomet knee designs
• Consistently restore function, stability and durability to the knee, thereby
meeting the needs of total knee patients today and tomorrow
• Provide instrumentation that allows reproducible results and offers the ability to
choose the level of constraint intraoperatively
• Develop new technology to further enhance total knee replacement into the
twenty-first century
The porous coated devices depicted in this brochure are marketed for use with bone cement
in the United States.
The Ascent™ system was designed in conjunction with Rick Bassett, M.D., Valley Baptist Hospital,
Harlingen, Texas; and Michael Jacobs, M.D., Good Samaritan Hospital, Baltimore, Maryland.
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Primary Cruciate Retaining Femorals
Retinacular Relief
On both the medial and lateral sides of the anterior flange, the Ascent™ femoral
component has the added benefit of retinacular relief. Retinacular relief is achieved
by streamlining the anterior sides of the component. The retinaculum must travel
over the sides of the femoral component for the patella to sit within the femoral
groove. By reducing the distance the retinaculum has to travel, the Ascent™
minimizes the need for lateral releases.
Swept-Back Femoral Design
The swept-back design of the component offers
tremendous advantages to both the quadriceps
mechanism and the patella. Several authors
maintain that “less boxy” designs provide a
smoother transition for the patellar
component as the knee goes into
flexion.1 The ease of transition may
result in fewer patellar clunks, less
patellar wear, and a reduction in soft
tissue impingement.
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Deep Patellar Groove
Much has been said about the design of a femoral
component and its effects on patellar perfor-
mance. The Ascent™ femoral component
maintains a deep patellar groove. A deep patellar
groove coupled with a true dome patellar
articulation helps decrease stresses on the patella
by improving patellar tracking, and dispersing
stress over a large contact area.
Optimal Range of Motion
By design, the Ascent™ knee specifically addresses range of motion. The Ascent™
knee offers a tighter posterior proximal radius, this allows easier rollback and provides
up to an additional 10 degrees of flexion.2
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(Amount of Bone Removed)
Cruciate Substituting Femorals
Posterior Stabilized Constrainable Femurs
The Ascent™ Posterior Stabilized System offers a
tremendous amount of intraoperative flexibility.
This system allows the surgeon to progress from a
posterior stabilized to a constrained device
simply by changing the tibial bearing. The
surgeon is not required to make any additional
bone resection when converting to the
constrained bearing.
Box Volume
The Ascent™ open and closed box P/S femoral components have a significantly
smaller box volume in comparison to other competitive designs, minimizing bone
removal (Figure 1). The polyethylene P/S tibial spine does not protrude above the
top of the open P/S box. Many competitive designs use what appears to be a very
small P/S femoral box. However, significant amounts of bone must be removed to
accommodate the tibial spine.
Figure 1
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Stability
In cruciate sacrificing knees, the height required
for the P/S Femoral Cam to jump over the P/S Post
is referred to as the “hop height.” The Ascent™
knee has a hop height of 18.5mm at 90 degrees
of flexion. A notable feature for the Ascent™
knee is that it maintains its hop height at deep
flexion angles where dislocations occur (Figure 2).5
Interchangeability
The condylar radius makes the Ascent™
posterior stabilized design fully interchangeable.
All posterior stabilized femoral components
articulate with all posterior stabilized tibial
components, providing full flexibility and
optimal bone coverage.
All posterior stabilized femoral components interchange withall posterior stabilized tibial components.
Figure 2
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Tibial Trays
Biomet’s tibial plate coverage is designed to
accommodate a wide range of bone sizes based on
the work of Mensch and Amstutz. The geometry
of the nine sizes utilizes the best available bone
on the tibial plateau, while offering uniform
distribution of tibio-femoral forces.
Plate Options
Primary tibial trays are made from both titanium and cobalt chrome alloys. Titanium
baseplates come either with an Interlok® finish or a titanium porous plasma sprayed.
Porous plasma sprayed baseplates accept up to four 6.5mm cancellous bone screws.
Both the porous and stemmed tibial plates can be used with block or wedge aug-
ments. All augments are fixed to the baseplates via screws. Cobalt chrome baseplate
options come in either fixed I-beam or fixed cruciate fin with an Interlok® finish.
Stem Options
The modular primary tray provides for the intraoperative selection of the stem to
match the specific needs of the patient. The combination of a Morse-type taper and
screw fixation helps maintain a solid connection between the stem and plate.
Various primary stem options meet specific patient needs.
Tibial augmentation blocks and wedges are available for theporous and stemmed trays. Canal filling and long stemextensions are available for the stemmed tray.
Based on the work of Mensch andAmstutz, a broad range of tibial sizescovers virtually any requirement.
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Compressive Locking Mechanism
Since 1989, Biomet’s locking bar has been clinically utilized and confirmed as a truly
reliable locking mechanism. Unlike snap-in designs, Biomet’s system features a
unique slide-in bar that compresses the polyethylene within the locking mechanism,
and reduces micromotion between the plate and polyethylene. Maximum polyethyl-
ene thickness is maintained at the periphery due to intercondylar placement of the
locking mechanism.Locking bar generates a compressivepolyethylene fit onto the tibial plate while
obtaining consistent bearing edge thickness.
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ArCom® Polyethylene
Wear
Knee wear is predominantly a fatigue mecha-
nism, which may lead to delamination and
pitting of the bearing surface. Direct compression
molded devices using 1900H raw polyethylene
have demonstrated clinically superior resistance
to this type of breakdown.1 With traditional
machining, stresses are created near the surface
of the component. The cutting tool shears the
polyethylene and pulls the material apart,
creating a region of residual stress. The residual
stress may sensitize the material to localized
breakdown and oxidation. Oxidation may
negatively impact the fatigue characteristics of
Argon Packaged: Compression Molded
+ =
+ =
Extruded Bar Stock Machining Oxidized Cross-Section
1900H Resin Direct Molding Non-Oxidized Cross-Section
the polyethylene, causing delamination. Since delamination is a major concern in
total knees, Biomet has made the commitment to direct compression mold the
Ascent™ tibial bearings to minimize the potential for wear and oxidative breakdown.
ArCom® polyethylene is tailored to address the specific wear mechanisms found in
total knee replacement.
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Controlling oxidation is an important aspect in theperformance of tibial bearings. Machining operations are amajor source of stress and need to be considered to controloxidation before sterilization. Ascent™ tibial bearings aredirect molded out of 1900H Resin to minimize the potentialfor wear and oxidation breakdown.4
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Revision
The Ascent™ Knee System addresses the
complex bone defects that revision cases often
present. With various modular options, the surgeon
has the ability to customize the implant to fit
patient needs. Multiple stem lengths and diameters,
along with femoral condylar augmentation and
tibial wedges, are available—maximizing the
ability to address bone defects. The intraopera-
tive flexibility is enhanced with the option of a
posterior stabilized or constrained bearing
depending on collateral deficiency. Additionally,
the surgeon is able to choose either a five or
seven degree femoral valgus angle for correct
placement within the femoral canal.
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Instrumentation
Precise, simple instrumentation enables the
surgeon to achieve optimal component position.
Optimal component position establishes balance
and appropriate tension which subsequently
improves function and increases longevity. The
Ascent™ instrumentation enhances function
and longevity through design, accuracy and
simplicity. This user-friendly instrumentation also
provides the flexibility to change from a cruciate
retaining to a posterior stabilized or constrained
knee within a single integrated system. The
instrumentation is easily understood by the scrub
team and central supply. Efficient and user
friendly, Ascent™ instrumentation prevents
confusion and serves to decrease operative time.
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The Family
AGC®•Maxim®•FINN®•Ascent™
THE COMPLETE KNEE SYSTEM
Finn®
Knee
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P.O. Box 587, Warsaw, IN 46581-0587 • 219.267.6639 • ©1999 Biomet, Inc. All Rights ReservedWeb site: http://www.biomet.com • eMail: [email protected]
Form No. Y-BMT-631/103199/M
References
1
Beadling, Lee; “Direct-Molded Components Shown to Resist Oxidation,” Orthopaedics Today,Vol. 17, No. 4, April 1997 [Citing Furman B., Li S., and Ritter M.].
2Basset, Rick W.; “Results of 1,000 Performance Knees—Cementless Versus Cemented Fixation,” Journal of Arthroplasty , pp. 409–413 Vol. 13, No. 4, 1998.
3Data on file at Biomet.
4Data on file at Biomet.
5Robinson, R.P., M.D.; Striplin, D.B., M.D.; “Posterior Dislocation of the Insall/Burstein IIPosterior Stabilized Total Knee Prosthesis,” The American Journal of Knee Surgery, pp. 79–83 Vol.5, No. 2, Spring 1992.
ArCom®, Ascent™, Finn®, Interlok® and T-1™ are trademarks of Biomet, Inc.