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Biomedical Engineering Trust I

Biomedical Engineering Corp.

Biomedical Engineering Trust

Frederick F Buechel

Michael J Pappas

Paul A Witte

The tibial component of a prosthetic ankle joint including a tibial component, a talar component, and an intermediate sliding plastic bearing, with the tibial component including a depending peripheral wall that surrounds and is spaced from the plastic bearing and is intended to reduce rubbing of the plastic bearing against tissue which would produce wear particles that lead to the formation of bone cysts. The depending peripheral wall of the tibial component is intended to reduce such possible abrasions by at least partially shielding the plastic bearing from the surrounding tissue.

Ankle prosthesis including tibial component having peripheral wall for preventing the formation of bone cysts

A tibia fixturing device comprises a metal tray formed with annularly spaced recesses in its underside at a depth of at least about 1.5 mm and from which a stem depends for axial insertion into a tibia conical cavity. The stem has a circular cylindrical portion proximal the tray and a conical portion distal the tray. Fins radially extend from the stem cylindrical portion and penetrate the tibia to provide some torsional resistance. Axially extending channels are formed about the stem periphery which channels have bottom surfaces parallel to the stem axis to provide further torsional resistance. The channels are arranged to not interlock with the cement in the axial direction to permit the cement to separate first from the device during axial removal of the device from the bone. The fins have inclined edges distal the tray and inclined radial outer edges to align and center the stem to the bone cavity edge. Cement in the tray recesses bonds the tray to a tibia resected surface to provide major torsional resistance of the tray about the cavity longitudinal axis.

Prosthesis fixturing device

A prosthetic system is provided for secure mounting of a prosthetic component to a bone, and particularly to a bone that may be diseased, damaged or deteriorated. The prosthetic system includes a plurality of screws that are mounted to healthy bone stock. Each screw includes a threaded portion extending from one end and a non-threaded portion extending from the opposed end. The non-threaded portion includes a discontinuous surface configuration thereon. Ends of the screws are positioned to support the prosthetic component. The bone cement is then disposed between the prosthetic component and the bone and in surrounding relationship to portions of the screws that project from the bone. The cement surrounds and attaches to the protrusions on the screws so that the screws and the cement reinforce one another in response to loads imposed thereon during use of the prosthesis.

Orthopedic prosthesis employing bone screws and cement

A prosthesis is provided having at least a smooth non-articulating load bearing surface disposed adjacent a bone. The prosthesis includes a substrate formed from a metallic alloy. At least the regions of the substrate defining the load bearing surface are coated with a biologically inert abrasion resistant material harder than the substrate for preventing leaching of ions from the substrate into adjacent body tissue and for preventing wear. The coating may be titanium nitride or zirconium or other such material exhibiting biological inertness and acceptable hardness. The coating preferably defines a thickness of 8-10 microns.

Prosthesis with biologically inert wear resistant surface

A femoral component with a femoral stabilizing implanted rod has condylar surfaces of different radii which mate with a thermoplastic 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 thermoplastic 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. In a second embodiment, a projection on the tibial component mates in a recess in the bearing for controlling and limiting the amount of axial rotation of the femoral component relative to the tibial component as a function of the extent of flexion in a knee joint.

Hinged knee prosthesis with condylar bearing

A joint prosthesis having a femoral element, a tibial element and a bearing for articulation therebetween is disclosed to further include an intermediate element. The intermediate element permits rotation of the bearing with respect to the tibial element and longitudinal translation of the bearing with respect to the intermediate element. Transverse translation of the bearing with respect to the intermediate element is precluded. In an alternative embodiment, the longitudinal translation may be limited either in the anterior or posterior direction.

Rotational and translational bearing combination in biological joint

An acetabular reamer is provided with a shaft having opposed front and rear ends. A mounting cap is securely connected to the front end of the shaft and includes a skirt having an interior surface spaced radially outwardly from the shaft and an opposed non-cylindrical exterior surface. At least one aperture extends through the skirt. A locking spring is disposed adjacent the interior surface of the skirt and includes a locking detent extending through the aperture in the skirt. The spring can be deflected radially inwardly to bring the detent into alignment with the exterior surface of the skirt. A reamer head is mountable over the mounting cap such that the rear wall of the reamer head deflects the spring radially inwardly during mounting and unmounting. In the fully mounted condition of the reamer head, the locking detent of the spring engages an inwardly facing surface of the rear wall of the reamer head. The.degree. acetabular reamer further includes a sleeve slidably and rotatably disposed around the shaft. The forward end of the sleeve can be gravitationally advanced into the annular space between the shaft and the skirt to prevent the inward deflection of the spring. Thus, the sleeve and the spring cooperate to prevent unintentional separation of the reamer head from the mounting cap.

Acetabular reamer

A multi-component hip joint prosthesis is provided comprising an acetabular cup and a plastic bearing liner, each of which defines a segmented open shell with an inferior segment thereof removed to provide enhanced flexibility. The enhanced flexibility substantially facilitates the assembly and disassembly of the components. The liner and the cup are retained in their assembled condition by interengagement between a plurality of ridges and at least one groove on the respective components. The plurality of independent ridges enhances the flexibility of the ridges, thereby further minimizing the assembly forces required. Interengageable keys and keyways on the respective components may be provided to prevent relative rotation therebetween. The cup may comprise a removable tab to facilitate the insertion of a tool between the cup and the liner for prying the liner from the cup if necessary.

Multi-component prosthesis with increased wall flexibility and segmented

A prosthetic joint includes a first bearing element which is attached to a first bone and has a substantially flat bearing surface. A second element having a bearing surface is attached to a second bone. A bearing is disposed between the first and second elements. The bearing has a central axis and is defined by a first surface and a second surface. The first surface is substantially flat and is at least partially in contact with the first flat surface of the first element. At least a portion of the second surface is in contact with the surface of the second element. The area of the planform of the first surface of the bearing is smaller than, and dissimilar in shape from, the area of the planform defined by the second surface of the bearing.

Compound shape rotating bearing

A multi-component hip joint prosthesis is provided comprising an acetabular cup and a plastic bearing liner, each of which defines a segmented open shell with an inferior segment thereof removed to provide enhanced flexibility. The enhanced flexibility substantially facilitates the assembly and disassembly of the components. The liner and the cup are retained in their assembled condition by interengagement between a plurality of ridges and at least one groove on the respective components. The plurality of independent ridges enhances the flexibility of the ridges, thereby further mimimizing the assembly forces required. Interengageable keys and keyways on the respective components may be provided to prevent relative rotation therebetween. The cup may comprise a removable tab to facilitate the insertion of a tool between the cup and the liner for prying the liner from the cup if necessary.

A modular stem type prosthesis is provided which includes a stem and an extension which are connected to one another with a slip fit interconnection that minimizes surface tensile forces in regions of the prosthesis adjacent the interface between the stem and the extension. Engagement between the stem and the extension is provided by deflectable end portions of one component of the prosthesis which are engaged in a mating deformation in the other component. The mating structures may define an interfitting ridge and groove. Micromotion between the respective parts may be prevents by a screw which may be tapered to achieve a lock fit. The extension may be of any selected length and any selected diameter in accordance with the needs of the patient.

Prosthetic device with modular stem

An improved stem-type prosthesis, including a head, stem and neck providing reduced bending and shear loading of the neck thereby allowing the use of a smaller neck to improve the range of motion between the prosthesis and an acetabular cavity and to allow the use of a more complete spherical head thereby improving wear and separation resistance of the prosthesis from other components such as from an acetabular component.

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South Orange, NJ, United States of America

Frederick F Buechel