| BUECHEL-PAPPAS™
KNEE REPLACEMENT SYSTEM - REVISION |
Modular
Knee |
 |
In pathology
where there is grossly deficient bone stock the Buechel -
Pappas Knee Replacement System contains modular revision components
which provide stem fixation to augment the usual compressive
surface fixation. A stem may also be used to traverse shaft
fractures. The stems used are those of the B-P Hip replacement
system and are available in diameters ranging from 10 through
20mm in 1mm increments, and lengths of 25 to 200mm in 25m
increments. The connection is reliable, convenient and free
of micro-motion.
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 and
textured (for cemented use only) fixation surfaces are available.
Revision
Component Description
1.
MODULAR 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 either
tibial component. Its geometry also congruently accommodates
varus-valgus and rotary motions. It accepts a large variety
of diameters and lengths of extension stems. This component
accepts the modular stems of the B-P Hip System.
2.
PATELLAR COMPONENT
The Patella Component consists of a 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, three peg, anchoring plate is
used to protect the prosthesis-cement and prosthesis-bone
interfaces. It also functions as a substrate for porous-coating.
3.
UHMWPe PATELLAR COMPONENT
This component provides fully congruent contact on its lateral
face except near full extension where contact pressures are
low. The medial face, 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.
MODULAR TIBIAL COMPONENT
This tibial component accepts the same extension stems that
are used with the MODULAR TRICOMPARTMENTAL FEMORAL COMPONENT.
This plateau has an axial rotation stop and is intended to
limit bearing rotation. 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.
MODULAR STEMS
The stems used are those of the B-P Hip replacement system
and are available in diameters ranging from 10 through 20mm
in 1mm increments and lengths of 25 to 200mm in 25mm increments.
The connection is reliable, convenient and free of micro-motion.
7.
REBAR® SCREWS
These are used to support the implants during the healing
of bone grafts used to support the implants, or if cement
is used, to support the implants before and during cementation.
The knurled regions of the screws enhance their integration
into the bone or cement mass used to support the implants.
These screws are available in lengths of 20, 25, 38 and 50mm.
8.
INSTRUMENTATION AND TRIALS
The primary instruments and trials as well as available hip
stem reamers in one mm increments are used in the implantation
of the revision components. There are a few specialized revision
instruments. These are shown in the “Revision Knee Surgical
Procedure’ section in the ‘Surgeons’ menu.
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