JP2008541851A - Artificial knee joint with ceramic tibial components - Google Patents

Abstract

The improved knee prosthesis includes a ceramic tibial component for articulation with the femoral surface of a natural or artificial joint (with surface replacement). The ceramic tibial component is carried in the form of a ceramic monoblock adapted to be fixed relative to the patient's tibia, or alternatively by a tibial base plate member adapted to be fixed relative to the tibia. Supplied in the form of ceramic bearing insert parts. In either form, the ceramic tibial component includes at least one upwardly concave articulating surface for movably supporting engagement by a generally convex or condylar shaped femoral articulating surface. Is included. Ceramic tibial parts offer long service life and improved wear resistance.

Description

  The present invention relates generally to improved knee prostheses, and more particularly to an improved tibial component made from a relatively hard and relatively high strength ceramic material. The ceramic tibial component generally includes at least one articulating surface that is configured to directly support and engage with an associated femoral joint surface having a generally convex or condylar shape. Ceramic tibial components are designed to be ultra-low wear over a long service life, which also eliminates the problems of conventional polymer-based bearing inserts and the associated detrimental wear debris.

  A knee prosthesis typically includes a tibial component that is adapted to be secured to the upper end of the patient's tibia that has been appropriately resected. Such tibial components are typically formed from biocompatible metallic materials such as cobalt chrome, titanium, stainless steel, or polymer based materials. Thus, the tibial component defines a pair of upwardly directed generally concave bearing seats for articulating with a corresponding pair of generally convex or condylar shaped articular surfaces at the lower end of the patient's femur. Providing a strong and durable prosthetic base structure that supports polymer-based bearing inserts. These femoral articular surfaces can be defined by natural femoral surfaces or joint condylar surfaces on a reconstructed femoral component or a femoral component of a prosthetic joint that is secured to the patient's femur. Such femoral components are typically made from biocompatible metallic materials such as cobalt chrome, titanium, stainless steel, zirconium, zirconium oxide, and ceramic materials such as alumina, zirconia and zirconia reinforced alumina (ZTA). .

  Polymer-based bearing inserts are typically formed from high-density or ultra-high molecular weight polyethylene (PE) materials that have been shown in a variety of specific configurations to provide a smooth, relatively low wear joint to the femoral surface. Is done. However, clinical studies have shown that polymer bearing inserts can generate and release large amounts of wear debris over time, and that bone degeneration is due at least in part to the presence of such polymer-based wear debris. Has been shown to be an essential contributor to implant failure. More specifically, according to such studies, PE wear debris released around the implant tissue induces adverse biological reactions, including foreign body giant cell and macrophage cell reactions, and ultimately, along with harmful bone resorption, Has been shown to cause loosening and failure of prosthetic implants. As a result, improvements with alternative artificial joint structures have been proposed, such as the use of highly cross-linked polyethylene materials for polymer-based bearing inserts. Other alternative prosthetic joints have also been proposed in which polymer-based bearing inserts and associated wear debris are removed by using double rigid parts such as ceramic on ceramic or metal on metal. Knee joint pairs are limited to metal-on-polymer or ceramic-on-polymer.

  In general, ceramic prosthetic knee joint components are expected to be used in ceramic-on-ceramic or ceramic-on-metal articulation interfaces to completely eliminate polymer-based bearing inserts. Such artificial joint structures, when formed with good surface finish and conformal surface shape, have relatively low friction compared to ceramic-polymer or metal-polymer articulation interfaces. A coefficient was shown, resulting in a significant reduction in component wear. However, a major limitation of the use of ceramic components, particularly alumina-based ceramic materials, is the unacceptably high rate of brittle fracture that occurs from months to years after post-operative screening. In this regard, ceramic materials are generally less durable and are therefore susceptible to brittle fracture.

U.S. Patent No. 6,099,077 discloses an improved ceramic material for joint prostheses such as artificial knee joints, and a ceramic-on-ceramic or ceramic-on-metal articulation interface is disclosed. Improved ceramic materials include doped silicon nitride (Si ₃ N ₄ ), which has relatively high hardness, tensile strength, elastic modulus, lubricity and fracture toughness. Specifically, the improved doped silicon nitride ceramic has a flexural strength greater than about 700 megapascals (MPa) and a fracture toughness greater than about 7 megapascal root meters (MPam ^0.5 ). This high strength and toughness doped silicon nitride ceramic dramatically reduces the risk of brittle fracture and achieves ultra low wear over a long service life.

In addition, U.S. Patent No. 6,057,031 discloses an improved ceramic material for use in bone grafting, in which the ceramic material is a first and second region of relatively low porosity and high porosity. And mimics the structural properties of the patient's natural bone by mimicking the structure of natural cortical and cancellous bone, respectively. Preferred ceramic materials disclosed have a flexural strength greater than about 500 megapascals (MPa) and a fracture toughness greater than about 5 megapascal root meters (MPam ^0.5 ). In use, a relatively low porosity region of ceramic material provides high structural strength and bondability, while a high porosity region is suitable for bone ingrowth and provides a firm and stable implant fixation To achieve.

The present invention includes an improved knee prosthesis in which a particularly load-bearing tibial component is made from an improved high strength and high toughness ceramic material as disclosed in US Pat. It is.
US Pat. No. 6,881,229 US Pat. No. 6,846,327

  In accordance with the present invention, the improved knee prosthesis is made of a relatively high strength and tough ceramic material and is generally convex or condylar defined by the prosthetic femoral joint component or the patient's natural bone. A force-resistant tibial component is defined that defines an articulating surface of the femur in the form of and at least one articulating surface to be articulated to ultra low wear. The ceramic tibial component is made of a tibial bearing insert component that is made to be fixed directly to the patient's tibia, or alternatively is carried by a tibial baseplate member adapted to be fixed to the tibia. It is a shape.

In one form, the ceramic tibial component may be a relative one, such as doped silicon nitride (Si ₃ N ₄ ) disclosed in US Pat. No. 6,881,229, incorporated herein by reference. A monoblock structure defining at least one and preferably a pair of generally concave articulating surfaces or bearing sheets formed of a ceramic material having high hardness and high fracture toughness. This high-strength and high-toughness doped silicon nitride ceramic is articulated to the femoral joint surface of prosthetic materials, such as biocompatible metals or ceramics, or articulated to the natural femur In some cases, the risk of brittle fracture is dramatically reduced and ultra-low wear over a long service life is achieved. The tibial ceramic monoblock structure includes a firm ingrowth fixation to the natural tibia, such as the porous ceramic disclosed in US Pat. No. 6,846,327, also incorporated herein by reference. And a lower region defined by a ceramic porous bone ingrowth surface. Another form is the attachment of parts to the natural tibia by cementation. The porous structure allows for the bite of the bone. Further alternative methods for cementation do not include a porous section, can be replaced with a slot or pocket that accepts cement, and may or may not include an undercut feature for tensile strength .

  In one alternative preferred form of the invention, the ceramic tibial component includes a tibial bearing insert made from a ceramic material (described above) having relatively high hardness and high fracture toughness. The ceramic tibial bearing insert is configured to be fixedly or partially movably mounted on a tibial baseplate member adapted to be fixed to the patient's tibia. The tibial baseplate member is preferably a ceramic material such as that described above, a bearing platform defined by a relatively hard and tough ceramic, and an underside defined by a ceramic porous bone ingrowth surface. It can be formed by combining with the area. Alternatively, the tibial baseplate member may be made from a biocompatible metal. In one form, the tibial bearing insert may include a central upright stabilizer post of the general type described in US Pat. No. 5,116,375.

  In another alternative form, the ceramic tibial component includes an upwardly shown articular surface made of a ceramic material (described above) having a relatively high hardness and high fracture toughness, along with the upper end of the patient's tibia. A meniscal bearing insert that defines a lower region defined by a porous bone ingrowth surface of ceramic suitable for ingrowth or bone cement fixation with a region prepared in the part may be included . A hard, strong articulating surface is typically a shallow, upwardly concave bearing for articulating with a convex or condylar shaped femoral articulating surface defined by the femoral prosthetic component or the patient's natural bone A sheet is defined.

  In each of the foregoing embodiments of the present invention, the ceramic tibial component of the knee prosthesis allows for the removal of polymer-based bearing inserts, thereby eliminating post-operative problems associated with polymer-based wear particles and debris. Is also possible. In addition, ceramic tibial components provide ultra-low wear over a long service life without substantially causing the brittle fracture problems normally associated with ceramic prosthetic joint tissue.

  Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

  As shown in the exemplary drawings, the improved knee prosthesis, generally designated as reference numeral 10 in FIGS. 1-4 in one preferred form, includes a relative for secure fixation to a patient's bone. Included is a tibial component 12 made from a relatively hard and high strength ceramic material that may also include a porous ceramic bone ingrowth surface 14 (FIG. 3). The ceramic tibial component 12 articulates with a femoral prosthesis 16 (FIGS. 1 and 4) that can be made from a rigid and high strength material, such as a suitable, preferably identical ceramic material or a biocompatible metallic material. Or to articulate with the patient's natural femoral surface. The resulting ceramic-on-ceramic, or ceramic-on-metal, or ceramic-on-bone articulation interface has ultra-low wear over a long service life, eliminating the problems of conventional polymer-based bearing inserts and the associated wear debris Also possible.

  1 and 4 show a knee prosthesis 10 that includes a ceramic tibial component 12 and an associated femoral component 16 for repairing or replacing the surface of a natural anatomical joint of a human knee joint. . In this regard, the ceramic tibial component 12 includes a monoblock structure having a size and shape that can be fitted and secured to the upper end of the resected tibia 18 (FIG. 4), while the femoral component 16 includes It has a size and a shape that can be similarly fitted into the lower end of the resected femur 20 and firmly fixed. Generally, the tibial component 12 defines an upwardly shown platform 22 that is contoured to form a pair of upwardly indicated generally concave bearing seats 24 and 26 that are laterally spaced. The bearing seats 24, 26 are shallow concavely shaped for engaging and integrally sliding and rotationally joining thereto with generally convex medial and lateral condyles 28 and 30 formed on the femoral component 16, respectively. An articulating surface is defined.

  By making the joint surfaces or bearing sheets 24, 26 on the tibial component 12 from a selected ceramic material with high bending strength and high fracture toughness, the resulting joint interface with the femoral condyle surface is Beneficially exhibits very low wear over its useful life. Importantly, according to the present invention, a high-density or high molecular weight polyethylene (PE) bearing insert, etc. that is normally mounted between the tibial component 12 and the femoral condyle tissue to help smooth joining between these components, etc. Conventional polymer-based bearing inserts can be removed. In this regard, clinical studies have shown that premature artificial joint failure is associated with the generation and accumulation of polymer-based wear debris associated with such polymer-based bearing inserts. In addition, the use of polymer-based inserts inherently increases the overall length of the prosthesis structure, thus limiting its use to larger bone patients who can accept larger sized prostheses. End up.

  1-4, the ceramic tibial component 12 includes an upper platform 22 that is contoured to define concave bearing seats 24, 26 and a further downwardly extending fixation post 32. As shown in FIG. Including, shown as a single or substantially monoblock form. The fixation post 32 has a non-circular cross-sectional shape, such as a radial wing structure as shown, for receipt of inset within the resected upper end (FIG. 4) of the patient's tibia 18. Preferably it is formed. In addition, the lower surface of the upper platform 22 has a ceramic porous bone ingrowth surface coating or lining 14. It will be appreciated by those skilled in the art that other structural fixation elements such as pegs that may or may not be centrally located can also be used, as well as other fixation techniques such as cementing the artificial joint-bone interface. Can be used.

Suitable ceramic materials used to make the ceramic tibial component 12 of the present invention include the relative ones described in detail in US Pat. No. 6,881,229, specifically incorporated herein by reference. Highly bending strength and high fracture toughness ceramic materials such as doped silicon nitride (Si ₃ N ₄ ) with particularly high hardness, tensile strength, elastic modulus, lubricity and fracture toughness are included. This doped silicon nitride ceramic material has a relatively high bending strength above about 700 megapascals (MPa) and a relatively high fracture toughness above about 7 megapascal root meters (MPam ^0.5 ). This high strength and toughness doped silicon nitride ceramic dramatically reduces the risk of brittle fracture and achieves ultra low wear over a long service life.

  This high strength and high toughness ceramic material is used to form the base of the ceramic tibial component 12. In this regard, such a substrate structure has a relatively low porosity, and thus is generally consistent with the characteristics of natural cortical bone covered with smooth and smooth articular cartilage, and generally mimics this. Has density and high structural integrity. FIG. 3 further illustrates a relatively large or highly porous, ceramic porous bone ingrowth surface formed under the tibial platform 22 that generally matches and mimics the characteristics of natural cortical bone. A coating or lining 14 is shown. As a result, this high porosity surface coating or lining 14 provides an effective bone ingrowth surface to achieve a firm and stable bone ingrowth fixation of the ceramic tibial component 12 to the patient's tibia 18. I will provide a.

  As will be appreciated by those skilled in the art, the specific material used for the bone ingrowth surface coating or lining 14 can vary, but suitable porous materials include ceramic porous ingrowth surface materials. included. In this regard, US Pat. No. 6,846,327, incorporated herein by reference, has relatively high bending strength and relatively high toughness, and natural cortical and cancellous bone. Disclosed is a ceramic bone graft component that defines first and second regions of relatively low porosity and high porosity that mimic structure, respectively. These regions of different porosity may be created singly or may be integrated into a common or monolithic ceramic part with a variable porosity gradient. In a preferred form, the ceramic tibial component 12 has a porosity gradient in the range of about 2% to about 80% by volume, and the porosity in the high porosity region is about 30% to about 80%. % By volume, and the overall pore size ranges from about 50 microns to about 1,000 microns. In use, the relatively low porosity region of the ceramic material provides a dense and hard tissue with high structural strength and bonding, while the high porosity or low density region is within the bone. Suitable for rapid growth and achieves a stable and stable implant fixation.

US Pat. No. 6,846,327 describes yttria stabilized zirconia (yttria about 2.5 to about 5 mol% in zirconia) or ceria stabilized with about 10 volume% to about 20 volume% zirconia component. Suitable alumina-zirconia ceramic materials of zirconia (about 2.5 to about 15 mole percent ceria in zirconia) zirconia phase are disclosed. The resulting ceramic material has a highly desirable combination of high bending strength (greater than about 500 MPa) and high fracture toughness (greater than about 5 MPam ^0.5 ). The stronger and stronger silicon nitride (Si ₃ N ₄ ) ceramic described in US Pat. No. 6,881,229 is preferred, but in the present invention such alumina is used in the ceramic tibilar component cup 12. -Zirconia based ceramic material may be used.

Thus, in a preferred form, the ceramic tibial component 12 is made of a desired high strength and high strength, such as the doped silicon nitride (Si ₃ N ₄ ) material described in US Pat. No. 6,881,229 cited above. Mainly made from ceramic materials with toughness and relatively low porosity. The ceramic tibial component 12 is formed from a high porosity ceramic material, preferably as described in US Pat. No. 6,846,327, which extends over a substantial extent below the upper platform 22. Also included is a relatively high porosity bone ingrowth surface 14. This relatively high porosity bone ingrowth surface 14 is preferably formed integrally with a low porosity substrate, although it will be appreciated by those skilled in the art that It may be added separately as a surface coating or lining.

  The femoral component 16 shown in FIGS. 1 and 4 is made of a ceramic material that, in the most preferred shape, is compatible with the material of the ceramic tibial component. In this regard, suitable materials for the femoral component 16 include equivalent or identical high strength, high strength corresponding to the ceramic tibial component 12, as disclosed in US Pat. No. 6,881,229. Tough materials are included. Alternatively, the femoral component 16 may preferably be made from a biocompatible metallic material such as the cobalt chrome alloy disclosed in US Pat. No. 6,881,229 cited above, Other biocompatible metals may be used. In either configuration, the femoral component 16 defines downwardly convex articular condyles 28, 30 that form an articulating surface for engaging the bearing sheets 24, 26 on the tibial component 12. In addition, the upper side of femoral component 16 (both ceramic and metallic) includes one or more upstanding fixation posts 34 and / or one or more regions or coatings 36 that carry a porous bone ingrowth surface. sell. In the ceramic embodiment, the femoral component 16 has high strength and toughness defining the articular condyles 28, 30 as described in the aforementioned US Pat. No. 6,846,327. A monoblock or substantially a single structure may be included that includes both a low porosity substrate and one or more high porosity regions defining a bone ingrowth surface or surface 36. Alternatively, it will be appreciated by those skilled in the art that in a partial knee prosthesis where the tibial component engages and couples to the natural condylar tissue at the lower end of the patient's femur, the ceramic tibia Part 12 may be used.

  Figures 5-13 illustrate yet another preferred form of the ceramic tibial component of the present invention. For convenience and simplicity of description, the components shown in FIGS. 5-13 that correspond in structure and / or function to those shown and described in FIGS. 1-4 will be referred to by the same reference number multiplied by 100. Identified.

  FIGS. 5-6 define a pair of substantially concave bearing seats 124 and 126 shown upward and include an upper ceramic bearing insert 40 adapted to be assembled with the lower tibial baseplate member 42. A modified ceramic tibial component 112 is shown. In this embodiment of the invention, the lower base plate member 42 defines at its upper end a tibial platform 122 coupled with a downwardly projecting fixation post 132. Further, the lower surface of the tibial platform 122 may include a porous bone ingrowth surface or coating 114 similar to that shown and described in FIG. The upper side of the platform 122 is an undercut 46 for receiving and engaging a locking rib 48 formed on the bearing insert 40 to engage and maintain the bearing insert 40 assembled with the base plate member 42 (FIG. 6) is surrounded by a low upright peripheral rim 44 that includes the front and rear sides of the platform 122.

  In one preferred form, the ceramic bearing insert 40 is a related ceramic or metal femoral component (not shown in FIGS. 5-6) or the natural femur 20 (also shown in FIGS. 5-6). Made from a selected high strength and toughness ceramic material that provides ultra-low wear and long service life when joined together. Again, suitable ceramic materials are disclosed in US Pat. No. 6,881,229. The associated base plate member 42 is made of a biocompatible metal suitable for snap-fit engagement of the ceramic rib 48 on the bearing insert 40 with the undercut rim 44 on the base plate member 42. Alternatively, if necessary, the bearing insert 40 and base plate member 42 may be made of the same or compatible ceramic material and the snap-fit ribs 48 may be made of a suitable deformable material and mounted on the bearing insert 40.

  FIG. 7 corresponds to the bearing insert 40 shown and described in FIGS. 5-6, but with an upright central stabilizer projecting short upwards from a generally central position between the two concave bearing seats 124, 126. FIG. A modified bearing insert 140 is shown that further includes a post 50. This stabilizer post 50 is a reconstructed knee, especially when used in combination with a femoral component of the type described in the drawings in US Pat. No. 5,116,375, incorporated herein by reference. Provides further stabilization of the joint. A pair of lower snap-fit ribs 148 are provided for mounting the modified bearing insert 140 on the tibial baseplate member 42 (FIGS. 5-6). Those skilled in the art will appreciate that the stabilizer post 50 shown in FIG. 7 may be incorporated into the monoblock tibial component 12 of FIGS. 1-4 or any of the various embodiments disclosed herein. As long as it is taken in.

  FIGS. 8-10 illustrate yet another embodiment of the present invention in which an upper ceramic bearing insert 240 is assembled with a lower tibial baseplate member 242. In this version of the invention, the upper bearing insert 240 further includes a central bearing post 52 formed to define a generally concave bearing seat 224, 226 shown upward and extending downward. The bearing post 52 is formed in the center of the lower base plate member 242 and is sized to be slip-fit received in an upwardly open bore 54 extending downward into the fixed post 232. The tibial platform 222 may be carried on the upper end of the base plate member 242 and include a porous bone ingrowth surface 214 on the lower surface.

  The tibial baseplate member 242 is secured to the upper end of the patient's resected tibia 18 (FIG. 10). The bearing insert 240 is assembled with the base plate member 242 by slidingly receiving the bearing post 52 in the open bore 54. In this position, the platform 222 provides a stable support to the generally flat lower surface of the bearing insert 240 so that the bearing insert 240 rotates about the central axis of the bearing post 52 during knee joint joints. It becomes possible to do. In this regard, FIGS. 9-10 illustrate the femoral component 16 articulated with a bearing insert 240 supported on the platform 222 of the lower base plate member 242.

  FIG. 11 shows a modification of the embodiment shown in FIGS. 8-10 in which the rotational support of the upper bearing insert 340 is a short peg of the lower tibial baseplate member 342 that includes the central fixation post 332 upright from the center of the platform 322. It has been replaced with a shallow bore 352 formed on the underside of the bearing insert 340 for receiving a slip fit. FIG. 12 shows a further variation of the embodiment of FIG. 11 in which the shallow bore formed under the upper bearing insert 440 includes an elongated slot 452 in the anterior-posterior or anterior-posterior direction. The slot 452 is adapted to receive an upstanding peg 352 on the lower tibial baseplate member 342 of the type shown and described in FIG. FIG. 13 shows an elongated head 62 for the key 60 to fit into the slot 452 and a cylindrical shape for fitting into the open bore 54 of the lower tibial baseplate 242 of the type shown and described in FIGS. FIG. 13 shows a further variation of FIG.

  In these versions, FIG. 11 shows that if the peg 354 is rotatably fitted in the bore 352, the bearing insert 340 can be rotationally displaced relative to the base plate member 342, but the peg 354 is press-fitted into the bore 352. If so, relative movement between the assembled parts is prevented. In FIG. 12, the assembled parts allow for a combined rotation and / or anterior-posterior movement of the bearing insert 440 relative to the tibial baseplate member 342. Finally, the key 60 of FIG. 13 effectively prevents relative movement of the slotted bearing insert of FIG. 12 when the key body 64 is press-fitted into the bore 54 of the base plate member 242 of FIGS. To do. Alternatively, when the key body 64 is rotationally mounted in the bore 54 of the base plate member, a combination of rotation and translation between the assembled parts is possible.

  In each of the embodiments shown in FIGS. 8-13, the bearing insert is a high, which provides ultra-low wear and long service life when articulated with an associated ceramic or metal femoral component or natural femur 20. It is suitably formed from a strong and tough ceramic material. Again, suitable ceramic materials include those disclosed in US Pat. No. 6,881,229. The associated base plate member is preferably made from the same or equivalent ceramic material, or a suitable biocompatible metallic material. In either ceramic or metal form, the platform 22, 122, 322 defined by the base plate member preferably includes a porous bone ingrowth surface formed on the underside. In the ceramic form, suitable base plate member structures include a low porosity region defining a structural load-bearing substrate, as described in US Pat. No. 6,846,327, cited above, and A dual porous ceramic material is included having a high porosity region defining an integral bone ingrowth surface.

  FIGS. 14-17 illustrate another alternative preferred form of the present invention in which a modified ceramic tibial component 512 is provided in the form of a prosthetic meniscal bearing. This meniscal bearing 512 is sized to be secured to the upper end region of the appropriately prepared and / or resected tibia 18 and, as shown in FIGS. It defines an upwardly shown, preferably shallow, concave bearing seat 524 for articulating with adjacent femoral condylar surfaces, such as joining. However, it should be appreciated that the meniscal bearing component 512 may be used for joining with a prosthetic femoral joint 16 of the type shown and described in FIGS. The lower surface of the meniscal bearing component 512 includes a porous bone ingrowth surface or coating 514 (FIG. 17) for ingrowth-fixation to the prepared tibia 18. 14-15 illustrate a single meniscal bearing component 512, but it will be appreciated that to articulate with a pair of condyles 528 and 530, or corresponding condylar surfaces on an artificial femoral joint, respectively. A pair of such bearing components may be provided having an appropriate size, shape, and thickness.

  The meniscal bearing part 512 and in particular the bearing seat 522 are made from a selected high strength and tough ceramic material suitable for ultra-low wear and long service life. Again, suitable ceramic materials are disclosed in US Pat. No. 6,881,229. The lower bone ingrowth surface 514 of the bearing component 512 is suitable as an integral part, but for ingrowth fixation to the patient's bone, as disclosed in US Pat. No. 6,846,327. It is preferably formed with a high porosity.

  Various further modifications and improvements on the knee prosthesis of the present invention will be apparent to those skilled in the art. For example, if a ceramic articulating surface is specified, those skilled in the art will appreciate that such a ceramic surface may include a surface portion of a monolithic ceramic structure or have a ceramic coating. A ceramic coating supported on a non-ceramic substrate, such as a composite structure in the form of a metal substrate, may be included. An example of such a composite structure includes a metal alloy substrate having an integral ceramic articulating surface, such as an implantable material sold under the name Oxinium from Smith & Nephew of Memphis, Tennessee. Accordingly, no limitation to the invention is intended by the foregoing description and accompanying drawings, except as described in the appended claims.

  The accompanying drawings illustrate the present invention.

FIG. 1 is an exploded perspective view of an exemplary knee prosthesis including a ceramic tibial component in accordance with one preferred form of the present invention. FIG. 2 is a top view of a ceramic tibial component, generally taken along line 2-2 of FIG. FIG. 3 is a bottom view of the ceramic tibial component, generally taken along line 3-3 of FIG. FIG. 4 is a side view of the knee prosthesis of FIGS. 1-3, as assembled, with the patient's femur and tibia shown in dotted lines. FIG. 5 is an exploded perspective view of one preferred alternative form of the present invention including a ceramic tibial bearing insert adapted to be assembled with a tibial base member. 6 is a side view of the tibial bearing component and base member of FIG. 5 in an assembled state. FIG. 7 is a perspective view of an alternative form of ceramic tibial bearing component. FIG. 8 is an exploded perspective view showing a further preferred alternative form of the present invention including a ceramic tibial bearing component adapted to be assembled with a tibial baseplate member. FIG. 9 is a perspective view showing the assembled tibial bearing component and base plate member of FIG. 8 in an assembled state, and further assembled with the femoral component of an artificial knee joint. FIG. 10 is a side view of the knee prosthesis of FIG. FIG. 11 is an exploded perspective view showing one preferred alternative form of the tibial bearing component and base plate member of FIGS. FIG. 12 is another perspective view showing another preferred alternative form of the tibial bearing component and base plate member of FIGS. 8-10. FIG. 13 is a further perspective view showing yet another preferred form of the tibial bearing component and base plate member of FIGS. FIG. 14 is an exploded perspective view showing a ceramic meniscal bearing component suitable for tibial fixation and inserted between a patient's femur and tibia. FIG. 15 is a perspective view of a ceramic meniscal bearing component assembled between a patient's femur and tibia. FIG. 16 is a top view of the meniscal bearing component, generally taken at line 16-16 of FIG. FIG. 17 is a bottom view of the meniscal bearing component, generally taken at line 17-17 of FIG.

Claims (40)

A tibial component having a size and shape suitable for in-fixation to a patient's prepared upper tibia, the tibial component being a generally convex articulation formed on a mating femoral component A tibial component defining at least one upwardly directed bearing seat forming an articulating surface having a size and shape for articulating with the surface;
The bearing sheet is formed of a ceramic material having a relatively high bending strength and a relatively high fracture toughness due to ultra-low wear when articulated with the articulating surface of the femoral component after implantation. An artificial knee joint including an articulating surface. The ceramic material according to claim 1, wherein the ceramic material has a relatively high bending strength above about 500 megapascals (MPa) and a relatively high fracture toughness above about 5 megapascals root meters (MPam ^0.5 ). The described knee prosthesis. 2. The ceramic material of claim 1, wherein the ceramic material has a relatively high flexural strength above about 700 megapascals (MPa) and a relatively high fracture toughness above about 7 megapascal root meters (MPam ^0.5 ). The described knee prosthesis.   The knee prosthesis of claim 3, wherein the ceramic material comprises doped silicon nitride.   The knee prosthesis of claim 1, further comprising a porous bone ingrowth surface on the underside of the tibial component for fixation of the tibia component with a prepared patient tibia.   6. The knee prosthesis of claim 5, wherein the bone ingrowth surface comprises a ceramic bone ingrowth surface.   A ceramic material having a variable porosity gradient defining the at least one bearing seat and a relatively high porosity defining the ceramic bone ingrowth surface; The artificial knee joint according to claim 6, further comprising a porous second region, wherein the first and second regions are integrally formed.   The ceramic material has a porosity gradient in the range of about 2% to about 80% by volume, and the high porosity region has a porosity in the range of about 30% to about 80% by volume; The artificial knee joint according to claim 7.   9. The knee prosthesis of claim 8, wherein the ceramic material has pores ranging from about 50 microns to about 1,000 microns in pore size.   The knee prosthesis of claim 1, wherein the generally convex articulating surface on the mating prosthetic femoral joint includes a natural femur or a femoral condyle defined by an artificial femoral joint.   11. The knee prosthesis of claim 10, wherein the convex articulating surface of the artificial femoral joint is formed from a material selected from the group consisting essentially of a ceramic material and a biocompatible metallic material.   11. The knee prosthesis of claim 10, wherein the articulating surfaces of the prosthetic femoral joint and the tibial component are formed from the same ceramic material.   The knee prosthesis of claim 1, wherein the tibial component has a monoblock ceramic structure.   The tibial component includes a bearing insert mounted on a tibial baseplate member, the at least one bearing seat is formed on the bearing insert, and the tibial baseplate member is a patient prepared tibial upper end. The knee prosthesis of claim 1 adapted to be fitted and secured.   The knee prosthesis of claim 14, wherein the bearing insert is movably mounted on the tibial baseplate member.   The knee prosthesis of claim 14, wherein the bearing insert is snapped onto the tibial baseplate member.   15. The knee prosthesis of claim 14, wherein the tibial baseplate member is formed from a material substantially selected from the group consisting of ceramic materials and biocompatible metallic materials and combinations thereof.   The tibial baseplate member defines a structurally resistant and relatively low porosity first region and a relatively high porosity second region defining the bone ingrowth surface. 18. The knee prosthesis of claim 17, comprising a ceramic material having a porosity gradient, wherein the first and second regions are integrally formed.   15. The knee prosthesis of claim 14, wherein the articulating surfaces of the bearing insert and the tibial baseplate member are formed from the same ceramic material.   The knee prosthesis of claim 1, wherein the at least one bearing seat includes a pair of laterally spaced generally upwardly concave bearing seats.   21. The knee prosthesis of claim 20, wherein the tibial component further includes a stabilizer post that projects upwardly from a position generally provided between the pair of bearing seats.   The knee prosthesis of claim 1, wherein the tibial component comprises a meniscal bearing insert. A knee prosthesis having a tibial component having a lower surface that includes means for inset and securing to a patient's prepared upper tibial portion, the tibial component being formed over a mating femoral component Further defining at least one upwardly directed bearing seat that forms an articulating surface having a size and shape for articulating with a generally convex articulating surface;
The tibial component is formed from a ceramic monoblock material having relatively high flexural strength and relatively high fracture toughness due to ultra-low wear when articulated with the articulating surface of the femoral component after implantation. Has been an artificial knee joint.   24. The knee prosthesis of claim 23, wherein the ceramic material comprises doped silicon nitride.   24. The knee prosthesis of claim 23, wherein the fixation means includes a porous bone ingrowth surface on the lower surface of the tibial component.   The ceramic monoblock material has a variable porosity gradient defining a relatively low porosity first region in the at least one bearing seat, and a relatively high bone defining a bone ingrowth surface of the ceramic. 26. The knee prosthesis of claim 25, having a porosity second region, wherein the first and second regions are integrally formed.   24. The knee prosthesis of claim 23, wherein the at least one bearing seat includes a pair of laterally spaced generally concave bearing seats.   24. The knee prosthesis of claim 23, wherein the tibial component comprises a meniscal bearing insert. A tibial baseplate member having a lower surface that includes means for snapping into a patient's prepared upper tibia upper end;
A tibial bearing insert carried by the base plate member, the tibial bearing insert being sized and shaped for articulation with a generally convex articulating surface formed on a mating femoral component. A tibial bearing insert that defines at least one upwardly directed bearing seat that forms an articulating surface having:
The ceramic with relatively high bending strength and relatively high fracture toughness because the articulating surface of the tibial bearing insert is ultra-low wear when articulated with the articulating surface of the femoral component after implantation Artificial knee joint made of material.   30. The knee prosthesis of claim 29, wherein the ceramic material comprises doped silicon nitride.   30. The knee prosthesis of claim 29, wherein the fixation means comprises a porous bone ingrowth surface of the lower surface of the tibial baseplate member.   30. The knee prosthesis of claim 29, wherein the tibial baseplate member is formed of a material selected from the group consisting essentially only of a ceramic material and a biocompatible metallic material.   The variable perforation wherein the tibial baseplate member defines a structurally resistant and relatively low porosity first region and a relatively high porosity second region defining the bone ingrowth surface 35. The knee prosthesis of claim 32, comprising a ceramic material having a rate gradient, wherein the first and second regions are integrally formed.   30. The knee prosthesis of claim 29, wherein the articulating surfaces of the tibial bearing insert and the tibial baseplate member are formed from the same ceramic material.   30. The knee prosthesis of claim 29, wherein the at least one bearing seat includes a pair of laterally spaced upward concave bearing seats.   30. The knee prosthesis of claim 29, wherein the tibial bearing insert is movably mounted on the tibial baseplate member.   30. The knee prosthesis of claim 29, wherein the tibial bearing insert is snapped onto the tibial baseplate member.   30. The knee prosthesis of claim 29, wherein the tibial bearing insert and the tibial baseplate member jointly define interengaging posts and bores to allow relative rotational movement therebetween.   30. The prosthesis of claim 29, wherein the tibial bearing component and the tibial base plate member jointly define an interengaging post and an elongate slot in the front and back, allowing relative rotational and sliding motions therebetween. Knee joint.   One of the tibial bearing part and the tibial base plate member has an elongated slot formed in the anterior poster, and the other of the tibial bearing part and the tibial base plate member has a bore formed therein. 30. The knee prosthesis of claim 29, further comprising a key having an elongated head inset therein and a generally cylindrical body inset in the bore.

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