Buechel-Pappas™ Hinge Knee System

Buechel-Pappas™
Hinge Knee System

• Primary load bearing of the B-P Hinge Knee is carried by the tibiofemoral articulating surfaces and not by the hinge element as it is in other hinge knee designs.
• This allows for the use of a relatively small hinge which needs only to resist shear forces and not the much greater compression forces.
• The tibiofemoral articulating surfaces of this knee are fully congruent in all phases of flexion resulting in very low contact stress for all activities.

• Pappas recognized a need for a condylar bearing hinge knee prosthesis utilizing the bearing arrangement.
• In this combination the bearing arrangement is used to transfer most of the loading from the femur to the tibial through the condylar surfaces of the femoral and tibial components.
• The hinge, in contrast to the prior art devices, is used only for knee stabilization rather than load transfer.
• This allows the use of relatively small hinge elements producing a lighter weight device which requires significantly less removal of bone than typical hinge load bearing knee replacements.
• Minimizing bone removal is desirable since implant fixation is often improved where more bone is retained.

• A femoral component with a femoral stabilizing implanted rod has condylar surfaces of different radii which mate with a UHMWPE bearing.
• A mating tibial platform is stabilized in the tibia with a rod, the bearing translating on the platform in the posterior-anterior directions in response to knee flexion and extension.
• The bearing bears the full extension load on congruent articulating contact regions with the condylar surfaces and lesser flexion loads via incongruent articulating contact.
• A hinge assembly is pinned to the femoral condylar component through a head having a depending shaft fixed to a UHMWPE tapered bearing axially floating and rotatably movable in a tibia platform component mating cavity.
• The head passes through the bearing and stops the bearing translations at extreme posterior and anterior positions.

Features and Benefits

• Hinge Knee Implant has Hinge Knee Femoral component assembly with the carriage shaft locked into the femoral component, Hinge Knee Tibial platform, Stem, screw and wedges.
• Hinge Knee Implants are available in sizes 2, 3 & 4.
• Rotating Hinge allows axial rotation reducing the stresses at the Bone-Cement-Implant interface.
• The use of a small hinge reduces the necessary bone resection to less than that associated with most Posterior Stabilized designs.
• A stem may also be used to traverse shaft fractures.
• Availability of metallic augments to compensate for bone loss.
• A series of such augments is provided for both femoral and tibial augmentation.
• To minimize the risk of metal to metal rubbing these augments are intended only for use only with cement which acts to separate the metallic elements

• Distal, Posterior and Tibial wedges options are available
• Metallic augments to compensate for bone loss.
• A series of such augments is provided for both femoral and tibial augmentation.
• Distal Femoral augments are available in six sizes two thicknesses (5 and 10mm).
• Posterior Femoral augments are available in six sizes, three thicknesses (5, 10, and 15mm).
• Tibial augments are available in six sizes, three thicknesses (5, 10 and 15mm).

Instrumentation

• The additional instrumentation required to implant the Hinge components is minimal, consisting only of a box osteotome for each femoral size to prepare the cavity for the hinge pin.
• Minimal additional instrumentation is associated with the implantation of the B-P revision components.
• This simplicity of instrumentation reduces cost and complexity of revision and salvage surgery, a situation where such reduction is badly needed.