| BUECHEL-PAPPAS™
KNEE REPLACEMENT SYSTEM - PRIMARY |
Total
Knee |
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Total
knee arthroplasty represents a major advance in the management
of severe, crippling arthritis of any kind. Both cemented
and non-cemented implants have been developed in the New Jersey
Low-Contact-Stress Buechel-Pappas Knee System of components.
The current
B-P knee is a refinement of the original LCS knee, sold by
DePuy orthopaedics, developed by Drs. Buechel and Pappas more
than a quarter of a century ago. During the last twenty years
Drs. Buechel and Pappas have been refining the design based
on experience with the LCS. Although, DePuy has adopted most
of these refinements, the B-P knee contains additional refinements.
The primary difference between the current DePuy "Complete"
LCS and the B-P knee is the use of titanium alloy coated with
a wear and scratch resistant, ceramic, UltaCoat® titanium
nitride for all the metal components of the B-P knee. DePuy
also sells titanium alloy knees with UltraCoat, under license
from Drs. Buechel and Pappas, as a premium knee. However,
this coating is the standard at Endotec.
The superior
engagement of the B-P tibial bearing with the femoral component
makes the use of a posterior stabilized (PS) device unnecessary.
Thus, since PS devices are characterized by highly excessive
post against cam stresses, lack of axial rotation, failure
in providing full flexion and other problems such devices
are also undesirable. Please refer to ‘Evaluation of
Posterior Stabilized Knee’ paper in the ‘References’
section.
This
system, coupled with the revision knee system, contains a
wide variety of components allowing optimal treatment of a
wide range of pathologies.
Basic
Implant Concepts
- Duplication
of tibiofemoral and patellofemoral motion patterns.
- Maximal
area contact of metal to polyethylene bearings to decrease
contact stresses and improve wear properties.
- Metallic
anchoring components for better load transfer characteristics,
improved cement bed protection and substrate use in biologic
fixation surfaces. Components with both porous-coated Biocoat®
and textured (for cemented use only) fixation surfaces are
available. All UHMWPe patellar and tibial components are
also available for low demand patients.
Primary
Component Description
1.
TRICOMPARTMENTAL FEMORAL COMPONENT (left and right)
The Femoral Component is designed to replace the complex geometry
of the femoral articular surface while maintaining an anatomical
valgus angle. The radii of curvature decrease from anterior
to posterior in a coordinated fashion to provide full flexion
while maintaining excellent bearing congruity with the tibial
component. Its geometry also congruently accommodates varus-valgus
and rotary motions as well as providing congruent contact
for the patellar components or the natural patella. The B-P
femoral component has a 20° greater fully congruent tibiofemoral
range of motion than the current LCS device. Full patellofemoral
contact is retained for an additional 20° as well. Further,
improved articulating surface accuracy and fit improve the
congruity of the articulating surfaces in the B-P component.
2.
ROTATING PATELLAR COMPONENT
The Rotating Patella Component consists of a rotating patella
bearing mounted on a metallic anchoring plate. The bearing
congruently matches the spherical anterior flange segments
and sulcus of the femoral component. This component provides
axial rotation to allow for variations in anatomical rotation
as well as surgical misalignment. The metallic anchoring plate
is used to protect the prosthesis-cement and prosthesis-bone
interfaces.
3.
UHMWPe PATELLAR COMPONENT
This component provides fully congruent contact on its lateral
facet except near full extension where contact pressures are
low. The medial facet, which sees much lower loading, is in
line contact with the femoral component. Thus stresses in
this device rival those of the rotating bearing patellar component.
4.
TIBIAL BEARING
This component is used in the absence of viable cruciate ligaments
to provide functional stability by use of proper tension control
of the surrounding soft tissues of the knee. Limited axial
rotation with excellent bearing congruity and superior dislocation
resistance is provided. These bearings come in a variety of
thicknesses to allow flexibility in bone resection of the
tibia, to correct gross deformities, and can be extremely
useful in revision arthroplasties. A modular bearing with
a removable stem is available to ease bearing replacement
with the metallic components in situ.
5.
TIBIAL COMPONENT
This plateau has an axial rotation stop and is intended for
use with the Rotating Platform Bearing. In cases where there
are insufficiencies of the soft tissue structures this stop
provides resistance against spinout subluxation. This stop
does not engage the bearing unless spinout is induced. If
this occurs spin is limited so that normal compression of
the joint results in self reduction of the bearing to a normal
orientation.
6.
UHMWPe TIBIAL COMPONENT
This all poly device is available for low demand patients.
This device, although inferior to its mobile bearing counterpart,
is nevertheless superior to other fixed bearing tibial articulating
surfaces now in use with regard to providing lower contact
stresses.
7.
REVISION COMPONENTS
Modular, extended length, intramedullary stems are also available
with Modular Femoral and Tibial Components to provide additional
fixation in cases where bone stock is poor. Please refer to
the “Revision Knee System” in the ‘Products’
menu and the “Revision Knee System Surgical Procedure"
in the ‘Surgeons’ menu for details.
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