Prosthesis with composite component

ES 2 406 366 T3

DESCRIPTION

Composite component prosthesis

The present invention relates generally to an implantable knee prosthesis.

During the course of a patient's life, it may be necessary to perform a joint replacement procedure on the patient as a result of, for example, disease or trauma. The joint replacement procedure may involve the use of a prosthesis that is implanted in one or more of the patient's bones. In the case of a knee replacement procedure, a tibial tray is implanted in the patient's tibia. A support is then secured to the tibial tray. The surfaces of the condyle of a replacement femoral component bear against the tibial bearing.

One type of knee replacement is a fixed support knee replacement. As the name suggests, the bearing of a fixed bearing knee prosthesis does not move relative to the tibial tray. Fixed support designs are commonly used when the condition of the patient's soft tissues (ie, the knee ligaments) does not allow the use of a knee replacement that has mobile support.

In contrast, in a mobile type of knee prosthesis bearing, the bearing can be moved relative to the tibial tray. Mobile bearing knee prostheses include so-called rotary platform knee prostheses, in which the bearing can rotate about a longitudinal axis of the tibial tray.

Tibial trays are commonly made of a biocompatible metal, such as a cobalt chromium alloy, stainless steel, or a titanium alloy. The solid forms of these materials have a modulus of elasticity (Young's modulus) substantially greater than that of natural bone. For example, as disclosed in US-A-2009/192610, the cobalt-chromium alloy has been reported to have a modulus of elasticity of 220 GPa (gigapascals) and the 6A1 4V titanium alloy has been reported to have a modulus of elasticity of 110 GPa. This document also reports that the modulus of elasticity of cortical bone is 15 GPa and that the modulus of elasticity of trabecular bone is 0.1 GPa. When a tibial tray made of cobalt-chrome alloy or titanium alloy is mounted with a bearing made of, for example, ultra-high molecular weight polyethylene (UHMWPE), the total construction, including the tibial tray and bearing , may have effective stiffness that can result in non-optimal load transfer between the tibial implant construct and the underlying bone of the proximal tibia: A stress screen can occur in some areas of the proximal tibia, resulting in bone resorption and loosening of the implant.

For both fixed and mobile bearing knee prostheses, the tibial trays can be designed to be cemented into position on the patient's tibia or, alternatively, they can be designed to be fixed without cement. Cemented fixation is based on mechanical bonds between the tibial tray and the cement, as well as between the cement and the bone. Cementless implants generally have surface characteristics that promote bone ingrowth in the implant component, and rely on a substantial portion of this bone ingrowth for fixation.

The tibial components of both fixed and mobile bearing and cemented and cementless knee arthroplasty systems are commonly modular components, comprising a tibial tray and a polymeric bearing supported by the tibial tray. Tibial trays commonly include distally extending features, such as pins or stems. These extensions penetrate below the surface of the tibial plateau and stabilize the tibial tray component against movement. In cementless tibial implants, the outer surfaces of these extensions are typically porous to allow bone ingrowth. For example, in the Zimmer Trabecular Metal Monoblock Tibial Trays, the pins with flat distal surfaces and hexagonal axial surfaces are formed entirely of porous metal. In such trays, bone ingrowth is likely to occur along all surfaces of the spikes, including the distal surfaces.

Sometimes the primary knee replacement fails. Failure can be due to many causes, including wear, aseptic loosening, osteolysis, ligamentous instability, arthrofibrosis, and patellofemoral complications. When the failure is debilitating, revision surgery may be necessary. In a revision, the primary knee prosthesis (or portions of it) is removed and replaced with components from a revision prosthesis system.

When the tibial implant includes extensions (such as pins or stems) that extend into natural bone, a revision surgery usually requires a large resection of the bone in order to dislodge the extensions from the bone. This large resection not only complicates the surgery, but also requires the removal of more of the patient's natural bone than is desirable. This extra bone removal may further compromise the bone, increase the risk of bone pathology or abnormalities, or reduce the healthy bone available for revision implant fixation. In addition, the large resection usually means that a larger orthopedic implant is necessary to fill the gap and restore the joint component to its expected geometry.

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This difficulty in dislodging the tibial tray from the bone is compounded by the fact that the bone also grows into the distal surfaces of the extensions. Breaking these connections is problematic as these areas are not easily accessible from the tibial plateau.

US-A-2008/109081 discloses a knee prosthesis in which a tibial component has a lower portion that can be made of a metal or polyether ether ketone material, and an upper portion that can be made of a polyether ether ketone material. The lower portion has a pair of barbed peaks that extend downward to secure the tibial component to the tibia. The upper and lower plate portions are joined together by means of a flange in the upper portion which is received in a groove or track in the lower portion.

The invention provides a knee prosthesis as defined in claim 1.

The polymer portion of the composite component may comprise fiber reinforced PEEK.

The porous portion of the composite material component may have a greater porosity than that of the first component.

In a more detailed embodiment, the invention provides a knee prosthesis comprising a femoral component, a bearing, and a tibial tray. The femoral component has a medial condyle surface and a lateral condyle surface. The bearing has a distal surface and a proximal surface. The proximal surface includes (i) a medial bearing surface configured to articulate with the medial condyle surface of the femoral component, and (ii) a lateral bearing surface configured to articulate with the lateral condyle surface of the femoral component. Support is secured to the tibial tray. The tibial tray has a platform that has (i) a proximal surface, (ii) a distal surface opposite the proximal surface, and (iii) an extension that extends from the distal surface of the platform to a distal end along of an axis that intersects the distal surface. The extension has an axial length and an outer surface that includes a proximal outer surface adjacent the distal surface of the platform and a distal outer surface. The distal outer surface extends proximally from the distal end for at least part of the axial length of the extension. The tibial tray comprises a composite material that includes a solid polymer portion and a porous portion. The solid polymer portion of the tibial tray defines the proximal surface of the platform and abuts against the distal surface of the bearing. The polymer portion extends from the proximal surface of the platform into the extension and defines the distal outer surface of the extension. The solid polymer portion is secured to the porous portion of the tibial tray. The porous portion of the tibial tray has a higher porosity than the femoral component. The porous portion defines the distal surface of the platform.

Optionally, the porous portion defines the proximal outer surface of the extension.

Optionally, the distal outer surface of the extension is generally spheroidal.

Optionally, the polymer portion comprises fiber reinforced PEEK.

Optionally, the abutment comprises a different polymer material from the polymer portion of the tibial tray.

Optionally, the abutment comprises UHMWPE and the polymer portion of the tibial tray comprises fiber reinforced PEEK.

Optionally, the extension comprises a stem.

Optionally, the extension comprises a spike.

Optionally, the tibial tray includes a plurality of spaced pegs. In such embodiments, each pin can extend from the distal surface of the platform to a distal end along an axis that intersects the distal surface. Each of the pins may have an axial length and an outer surface that includes a proximal outer surface adjacent the distal surface of the platform and a distal outer surface that intersects the axis of the extension and is spaced from the platform. In such embodiments, the polymer portion can extend from the proximal surface of the platform into each post and can define the distal outer surface of each post. In such embodiments, the porous portion may extend from the distal surface of the platform in a distal direction and defines the proximal outer surface of each peg.

Optionally, the prosthesis is a fixed bearing prosthesis, and the distal surface of the bearing and the proximal surface of the tibial tray platform include complementary locking features. In such embodiments, the locking features of the proximal surface of the tibial tray platform may be formed in the polymer portion of the tibial tray platform.

The tibial tray component can be made by means of a procedure in which a porous base is provided. The base has a proximal surface, a distal surface, and an extension that extends distally from the proximal surface to a distal end. The extension has an opening at the distal end. The porous base has an interior surface that extends from the proximal surface to the opening at the distal end of the extension. A quantity of fiber reinforced PEEk material is provided. PEEK material

ES 2 406 366 T3 fiber-reinforced is molded to the porous base, so that the fiber-reinforced PEEK overlaps the proximal surface of the porous base and in this way, the fiber-reinforced PEEK material is molded to the surface inside the porous base and extends distally out of the opening at the distal end of the extension.

Optionally, the molding step comprises injection molding.

Optionally, the step of molding the fiber reinforced polyether ether ketone (PEEK) material to the porous base includes forming a locking mechanism in the polyether ether ketone (PEEK) material that is molded on the proximal surface of the base. porous.

Optionally, the method includes the step of placing a reinforcing plate on the porous base prior to molding the fiber-reinforced PEEK material to the porous base and wherein the step of molding the fiber-reinforced PEEK material to the porous base keeps the metal plate at the base.

The present invention addresses the need for a prosthesis with a modular implant component suitable for cementless fixation that can be more easily removed from bone in revision surgery to preserve native bone. The present invention also relates to the need for an implant with an effective stiffness less than that of an implant construction using tibial trays made of conventional solid titanium alloy and cobalt-chromium alloy. Examples of joint prostheses to which the invention is applicable include, for example, knee joint prostheses and ankle joint prostheses.

Embodiments of the invention are described below by way of example, with reference to the accompanying drawings, in which:

Figure 1 is an exploded perspective view of a fixed bearing knee prosthesis;

Figure 2 is a bottom perspective view of the support of the prosthesis of Figure 1;

Figure 3 is a perspective view of the tibial tray of the knee prosthesis of Figure 1;

Figure 4 is a bottom plan view of the tibial tray of the knee prosthesis of Figure 1;

Figure 5 is a cross-sectional view of the tibial tray of Figures 1 and 4, taken along line 5

- 5 of figure 4, as seen in the direction of the arrows;

Figure 6 is a perspective view of the porous portion of the tibial tray of the knee prosthesis of Figures 1, 4 and 5, shown as a preform prior to being molded to form the tibial tray illustrated in Figures 1, 4 and 5. Figures 1, 4 and 5;

Figure 7 is a bottom plan view of the porous preform of Figure 6;

Figure 8 is a cross-sectional view of the porous preform of Figures 6 and 7, taken along line 8-8 of Figure 7, as viewed in the direction of the arrows;

Figure 9 is a perspective view of an alternative embodiment of a preform;

Figure 10 is a bottom plan view of the preform of Figure 9;

Figure 11 is a cross-sectional view of the preform of Figures 9 and 10, taken along lines 11-11 of Figure 10, as viewed in the direction of the arrows;

Figure 12 is a cross-sectional view similar to Figure 5, showing a tibial tray made from the preform of Figures 9 to 11;

Figure 13 is a cross-sectional view similar to Figures 5 and 12, showing a tibial tray made with another embodiment of a blank;

Figure 14 is a schematic cross-sectional view of the interface of the porous portion and the polymer portion of the tibial tray;

Figure 15 is a cross-sectional view similar to Figures 5, 12 and 13, showing the tibial tray of Figures 1 and 3 to 5 assembled with a femoral component and a bearing;

Figure 16 is a cross-sectional view, similar to the view of Figure 5, of another embodiment of a tibial tray;

Figure 17 is a perspective view of the metal plate portion of the tibial tray of Figure 16;

Figure 18 is a bottom plan view of the metal plate of Figure 17;

Figure 19 is a perspective view of the porous portion of the tibial tray of Figure 16;

Figure 20 is a bottom plan view of the porous portion of the tibial tray of Figures 16 and 19, and Figure 21 is a cross-sectional view of the porous portion of the tibial tray of Figures 16, 19 and 20 , taken along line 22-22 of Figure 20, viewed in the direction of the arrows.

Terms representing anatomical landmarks, such as anterior, posterior, medial, lateral, superior, inferior, etc. they can be used throughout this specification in relation to both the orthopedic implants described herein and the natural anatomy of a patient. Such terms have well-understood meanings both in the study of anatomy and in the field of orthopedics. The use of these anatomical terms of reference in the specification is intended to be consistent with their well-understood meaning, unless otherwise indicated.

Referring to the drawings, Figure 1 shows a knee prosthesis 10 that includes a femoral component 12, a tibial tray 14, and a support 16. The knee prosthesis 10 is a fixed support knee prosthesis, which means that no movement is intended to occur between the tibial tray 14 and the bearing 16.

The femoral component 12 includes two condylar bearing surfaces: a medial condyle surface 18 and a lateral condyle surface 20. The femoral component 12 is configured to be implanted into a surgically prepared end of the patient's femur (not shown), and is configured to emulate the configuration of the patient's natural femoral condyles. In this manner, the lateral condyle surface 20 and the medial condyle surface 18 are configured (eg, curved) in a manner that mimics the condyles of the natural femur. The lateral condyle surface 20 and the medial condyle surface 18 are spaced from each other thus defining an intercondylar notch 22 between them. Intercondylar groove 22 defines a patella groove shaped to receive and abut against a patella implant component (not shown). The femoral component 12 of FIG. 1 is a cross retention component, although it should be understood that the principles of the present invention also apply cross elements that replace knee replacement systems. The femoral component 12 may include standard features of commercially available implants, such as those available from DePuy Orthopedics, Inc., of Warsaw, Indiana, as well as those available from other suppliers of knee replacement systems. The femoral component 12 may also include features disclosed in US-A-2010/036500, US-A-2009/032664, US-A-2009/0326667, US-A2009 / 326666, and US-A-2009/326665 .

The femoral component 12 can be constructed of a biocompatible metal, such as stainless steel, titanium, cobalt-chromium alloy, or titanium alloy, although other materials can also be used. The bone-engaging surfaces of these components may include pockets of cement to facilitate cementation of the component to the bone. The bone-engaging surfaces of the femoral component may alternatively be porous to promote bone ingrowth for permanent fixation.

As shown in Figure 1, bearing component 16 has a proximal articulation surface 17 and a distal mounting surface 19 opposite proximal articulation surface 17. Proximal articulation surface 17 of abutment 16 includes a bearing surface. medial 21 configured to articulate with the medial condyle 18 of the femoral component 12 and a lateral bearing surface 23 configured to articulate with the lateral condyle 20 of the femoral component 12. The bearing component 16 is modular, and is mounted with the tibial tray 14 intraoperatively and is secured thereto by means of a mechanical interlocking mechanism, as described in more detail below.

The tibial tray 14 includes a platform 24 having a proximal mounting surface 26 and a distal opposing surface 28 for bone engagement. The illustrated tibial tray 14 also includes a plurality of extensions 30, 32, 34, 36, 38 that extend distally from the bone-engaging distal surface 28 of the platform, to the distal ends 40, 42, 44, 46, 48 along axes 50, 52, 54, 56, 58 which intersect the distal surface 28 of platform 24. Each extension 30, 32, 34, 36, 38 has an axial length, shown, by example, like L1 and L2 in figure 5. Each extension 30, 32, 34, 36, 38 also has an outer surface comprising a proximal outer surface 60, 62, 64, 66, 68 adjacent to the distal surface 28 of the tibial platform 24 and a distal outer surface 70, 72 , 74, 76, 78 at the distal ends 40, 42, 44, 46, 48 of the extensions. The distal outer surfaces 70, 72, 74, 76, 78 of the extensions 30, 32, 34, 36, 38 extend proximally from the distal ends 40, 42, 44, 46, 48 of the extensions in at least part of the axial length of each extension 30, 32, 34, 36, 38. The outer distal surfaces 70, 72, 74, 76, 78 of the stem 30 and the pins 32, 34, 36, 38 are generally spheroid-shaped in the device shown in this drawing.

The tibial tray 14 is a composite of two materials, including a solid polymer portion 80 and a porous portion 82. As used herein, solid polymer is used to identify a material that lacks voids, which is substantially 100% of the theoretical density. As used herein, porous portion is used to identify a portion of the implant made of

ES 2 406 366 T3 a material that has voids and that has less than 100% of the theoretical density. As explained in more detail below, the porous portion may comprise a biocompatible metal or a biocompatible polymer.

Solid polymer portion 80 of tibial tray 14 defines proximal surface 26 of platform 24 and abuts against distal surface 19 of bearing component 16 when assembled. Solid polymer portion 80 extends from proximal surface 26 of the platform into each of extensions 30, 32, 34, 36, 38, and defines distal outer surfaces 70, 72, 74, 76, 78 of extensions 30, 32, 34, 36, 38.

Polymer portion 80 of tibial tray 14 is secured to porous portion 82, as described in more detail below.

The porous portion 82 of the tibial tray defines the bone-engaging distal surface 28 of the platform 24. This porous distal surface 28 faces the bone of the resected proximal surface of the tibial plateau, and defines a material that is conducive to ingrowth of the bone to allow for uncemented fixation of the tibial platform to the proximal tibia. As described in more detail below, porous portion 82 extends proximally from distal surface 28 and integrates with solid polymer portion 80 at a position between distal surface 28 and proximal surface 26 of platform 24.

A first example of the porous portion 82 of a tibial tray 14, prior to being molded into the solid polymer portion 80, is shown in Figures 6 to 8. This porous portion defines a base or preform 84 having a top surface 86 opposite to distal surface 28. The upper surface 86 is generally flat and flattened, and becomes the interface with the solid polymer portion 80 of the tray when the porous base or preform is molded with the polymer to make the tibial tray 14. The porous base or preform 84 it also defines the proximal outer surface 60, 62, 64, 66, 68 of each of the extensions 30, 32, 34, 36, 38. The proximal outer surfaces 60, 62, 64, 66, 68 extend distally outward from the bone-engaging distal surface 28 of the base or preform 84.

As shown in Figures 6 to 7, the upper surface 86 of the first porous base or preform 84 has a series of five holes or openings 90, 92, 94, 96, 98. These holes or openings correspond to extensions 30 , 32, 34, 36, 38.

Extensions 30, 32, 34, 36, 38 define a stem 30 and four spaced pins 32, 34, 36, 38. Stem 30 and pins 32, 34, 36, 38 are configured to be implanted into a surgically prepared end. of a patient's tibia (not shown).

Additional examples of porous metal preforms 84A, 84B are illustrated in Figures 9 to 13. In these examples, the base or preform has three holes or openings 90A, 90B, 92A, 92B, 96A, 96B. A tibial tray made with such a base or preform 84A, 84B, shown in Figures 12 and 13 at 14A and 14B, would have a stem 90A, 90B and two pins 92A, 92B, 96A, 96B. The number and shape of the extensions can be varied.

For the examples shown in Figures 9 to 13, the same reference numbers have been used as the parts corresponding to the first illustrated embodiment, followed by the letter A for the first alternative example of Figures 9 to 12 and with the letter B for the second alternative example of Fig. 13. In general, the description of the first embodiment applies to these alternative embodiments, except where distinctions are indicated.

As can be seen from a comparison of the preform 84 of the example of Figures 6 to 8 with the preform 84A of the embodiment of Figures 9 to 11, the porous preform or base need not include portions that extend distally beyond of the distal surface 28, 28A of the preform. A tibial tray formed with preform 84A of Figures 9-11 would have an appearance similar to tray 14A shown in Figure 12; In this example, porous portion 82A of tray 14A does not define any portion of extensions 30A, 32A, 34A, 36A, 38A, 40A; in contrast, the porous portion 82A defines a portion of the platform 28A of the tibial tray only. The total length of each of the extensions 30A, 32a, 34A, 36A, 38A, 40A in the example of Figure 12 comprises portions of the solid polymer portion 80A of the tibial tray 14A.

As can be seen from a comparison of trays 14A and 14B of Figures 12 and 13, not all extensions of the tibial tray have to be the same. In the example of Figure 13, the central stem extension 30B of tray 14B has a proximal outer surface 60b that is part of the porous portion 82B of tray 14B, with the distal outer surface 70B being part of the polymer portion 80B. from tray 14B; the outer surfaces of the other extensions 92B and 96B in the example of Figure 13 are part of the solid polymer portion of tray 14B along its entire exposed length.

In each of the embodiments shown in the drawings, at least part of each extension 30, 32, 34, 36, 38, 30A, 32A, 36A, 30B, 32B, 36B is defined by the solid polymer portion 80, 80A, 80B from tray 14, 14A, 14B. As shown in the cross sections of Figures 5, 12 and 13, the solid polymer portion 80, 80A, 80B extends through the cavity defined by the interior surfaces 100, 102, 104, 106, 108, 100A, 102A, 106A, 100B, 102B, 106B in each hole 90, 92, 94, 96, 98, 90A, 92A, 96A, 90B, 92B, 96B and extends to distal outer surface 40, 42, 44, 46, 48 , 40A, 42A, 46A, 40B, 42B, 46B of each extension 30, 32, 34, 36, 38, 30A, 32A, 36A, 30B, 32B, 36B.

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The solid polymer portions 80, 80A, 80B of the illustrated tibial trays 14, 14A, 14B may comprise a biostable and biocompatible polymer that is reinforced, such as fiber reinforced PEEK (polyether ether ketone). An example of a suitable material is PEEK reinforced with carbon fibers or with glass fibers. A commercially available carbon fiber reinforced PEEk material is available from Invibio Inc. of West Conshohocken, Pennsylvania and Invibio Limited Corporation of Lancashire, UK (www.invibio.com) under the trademark PEEK - OPTIMA. The carbon reinforced PEEK supplied by Invibio is available with different concentrations of carbon fiber and Invibio reports the different modulus of elasticity for the different concentrations: 20% by weight of carbon fiber having a modulus of elasticity or flexure of 15 GPa 30% by weight of carbon fiber having a modulus of elasticity or flexure of 19 GPA, and 60% by weight of carbon fiber having a modulus of elasticity or flexure of 50 GPa. It should be understood that the present invention is not limited to this particular PEEK material. Other materials that are or will be available are expected to be appropriate for use in implementing the invention. In addition, it is expected that other fibers can be used to reinforce the selected polymer, for example, the biocompatible polymer can be reinforced with hydroxyapatite (HA) filaments of various volume fractions, as described in US-A-2008 / 206297.

The porous portions 82, 82A, 82B of the tibial trays 14, 14A, 14B may comprise any commonly used biocompatible and biostable metal, such as stainless steel, titanium, and standard cobalt-chrome alloys and titanium alloys, or may comprise a polymer. biocompatible porous. Preferably, the porous portion 82, 82A, 82B has pores of such size, shape, and number that when the solid polymer portion 80, 80A, 80B of the tibial tray is molded into the porous portion 82, 82A, 82B, a intermediate tie layer between porous portion 82, 82A, 82B and polymer portion 80, 80A, 80B. An example of such a structure is shown in Figure 14; As shown in that drawing, there is a porous portion 82 that does not include any material from the solid polymeric portion 80, a solid polymeric portion 80 that does not include any material from the porous portion 82, and an intermediate portion 83 that includes material from both polymeric portion 80 as well as porous portion 82. In the intermediate portion 83, the polymeric material of the solid polymeric portion 80 and the skeleton of the porous portion 82 are sandwiched to mechanically bond the solid polymeric portion 80 to the porous portion 82. This same sandwich would also be present in the embodiments of the Figures 9 to 13.

Various types of porous structure can be used for the porous portions 82, 82A, 82B of the tibial trays 14, 14A, 14B. For example, a titanium metal foam can be used, such as the foams disclosed in US-A-2008/199720, US-A-2010/098574, US-A-2009/326674 and US-A-2009 / 292365. Other alternative materials are available. An example of a suitable alternative material is porous tantalum metal, disclosed, for example, in US-5282861 and US-A-2009/192610. Another example of an alternative is a solid metal body made of an implantable metal such as stainless steel, cobalt-chromium alloy, titanium, titanium alloy, or the like, and with a porous coating arranged on both the mating surface with the bone as on the surface that is applied to the polymer portion of the tibial tray. One type of porous coating that can be used as porous portions 82, 82A, 82B of tibial trays 14, 14A, 14B is that used in implant components that are available from DePuy Orthopedics Inc. of Warsaw, Indiana under the trademark Porocoat. Porous metal preform 84A can be manufactured using any of the processes described above or using other processes.

Porous biocompatible polymers are also available. For example, US-A-2008/206297 discloses porous biocompatible polymeric materials such as PEEk reinforced with hydroxyapatite fibers or filaments and the manufacturing processes of such materials. It is anticipated that such porous biocompatible polymers could be used for the porous portions 82, 82A, 82B of the tibial tray 14, 14A, 14B in place of metal.

Any biocompatible material that has a surface of sufficient porosity and adequate mechanical properties to form a mechanical bond with the solid polymer portion 80, 80A, 80B when molded together can be used as the porous portion 82, 82A, 82B of the tibial tray 14. , 14A, 14B.

It may be desirable to incorporate additional materials into the porous portion 82, 82A, 82B of the tibial tray 14, 14A, 14B. For example, to facilitate bone ingrowth, a calcium phosphate such as hydroxyapatite may be coated or deposited in the porous portion 82, 82A, 82B, with or without other bioactive agents.

If the porous portion 82, 82A, 82B of the tibial tray 14, 14A, 14B is made of a polymeric material, it may be desirable to provide additional reinforcement to the tray. One way to provide such additional reinforcement is illustrated in the embodiment of Figures 16 to 21. Figure 16 is similar to Figure 5, except that a reinforcing plate 200 is added to the composite construction. For the examples shown in Figures 16 to 21, the same reference numerals have been used for parts corresponding to the first illustrated embodiment, followed by the letter C. In general, the description of the first example applies to these examples. alternative, unless distinctions are indicated. Furthermore, it should be understood that the structures described below with respect to Figures 16 to 21 can also be applied to the examples illustrated in Figures 9 to 13.

The backing plate 200 in the example of Figures 16 to 21 is positioned between portions of a porous preform 82C and the solid polymer portion 80C of the tray 14C. As shown in Figures 17 and 18, the plate

ES 2 406 366 T3

200 It is contoured with a shape generally equal to that of the tibial tray platform and includes a plurality of holes or bores. A large central through hole 201 is sized, shaped, and positioned to correspond to hole 90C in porous polymer preform 84C shown in Figures 19 and 20. The backing plate 200 has four other spaced through holes 203, 205, 207, 209 that correspond in size, shape, and position to the holes 92C, 94C, 96C, 98C of the porous polymer preform 84C. The backing plate 200 also includes four spaced through holes 211, 213, 215, 217 sized, shaped, and positioned to fit over four raised supports 219, 221, 223, 225 that extend upwardly from the upper surface 86C of the preform. porous polymer 84C. It should be understood that the backing plate 200 is not necessarily drawn to scale; the thickness of plate 200 can be varied, along with the material, to achieve the desired properties for the entire tibial tray 14C. Plate 200 can be made of a metal, such as a standard cobalt-chromium alloy, stainless steel, or titanium alloy. Alternatively, plate 200 could comprise a biocompatible polymer, such as, for example, a fiber reinforced PEEK material or any other polymeric materials that have been described herein. For example, as explained above, since PEEK reinforced with carbon fibers is available in varying concentrations, one could select to make the reinforcing plate 200 with a PEEK with a concentration of carbon fibers and make the polymer portion. solid 80C with PEEK with another concentration of carbon fibers. The material and dimensions (eg, thickness) of the backing plate 200 can be varied to provide a desired effective stiffness for the entire tibial tray 14C.

All the examples of tibial trays 14, 14A, 14B and 14C described above are suitable to support the support 16.

In a preferred embodiment, the abutment 16 is formed of a polymeric material, but comprises a different polymeric material than is used for the polymer portion of the tibial tray. Suitable polymeric materials for support include ultra high molecular weight polyethylene (UHMWPE). The UHMWPE can comprise, for example, a cross-linked material. Techniques for crosslinking, cooling, or otherwise preparing UHMWPE are described in documents such as US-5728748, US-5879400, US-6017975, US-6242507, US-6316158, US-6228900, US-6245276 and US-6281264 The UHMWPE in the backing material can be treated to stabilize any free radicals present therein, such as by adding an antioxidant such as vitamin E. Techniques for stabilizing UHMWPE with antioxidants are described in, for example, US-A-2007/0293647 and US-A-2003/021216. It should be understood that the present invention is not limited to a particular UHMWPE material or UHMWPE material for backing 16. Other materials for backing 16 that are or will be available are expected to be useful in the invention.

Referring back to Figures 1-3, the first knee prosthesis is a fixed bearing prosthesis: bearing 16 is secured to tibial tray 14 by means of complementary locking features that eliminate or at least minimize any relative movement between support 16 and tibial tray 14 when these components are assembled.

As shown in Figure 2, the distal surface 19 of the abutment 16 includes a lateral pedestal 134 and a medial pedestal 138. The pedestals 134, 138 have posterior appendages 140 defined therein. A number of anterior appendices 142 are also defined on support 16.

As shown in Figures 1 and 3, a generally Y-shaped posterior reinforcement 144 defines part of the proximal surface 26 of the tibial tray 14. This posterior reinforcement 144 is formed in the polymer portion 80 of the tibial tray 14. In the first embodiment that has been described herein, the back brace 144 has a pair of arms 146, 148 that extend along a posterior section of the perimeter of the proximal surface 26 of the polymer portion 80 of the tray. Specifically, the lateral arm 148 of the posterior reinforcement 144 extends along the posterior edge 150 on the lateral side of the polymer portion 80, while the medial arm 146 of the posterior reinforcement 144 extends along the posterior edge 150 at the medial side of the polymer portion 80 in a direction away from the lateral arm 148. A third arm 152 of the posterior brace 144 extends in the anterior direction away from the intersection of the lateral arm 148 and the medial arm 146.

As shown in FIG. 1, back gusset 144 has a pair of cutouts 154, 156 defined therein. Specifically, lateral cutout 154 is defined on lateral arm 148 of posterior brace 144, medial cutout 156 being defined on medial arm 146 of posterior brace 144.

As also shown in Figures 1 and 3, an anterior reinforcement 164 with a general T-shape extends upwardly from the proximal surface 26 of the tibial tray 14. This anterior reinforcement 164 is formed in the polymer portion 80 of the tibial tray 14. In the first embodiment described herein, anterior brace 164 has a pair of arms 166, 168 that extend along an anterior section of the perimeter of proximal surface 26 of polymer portion 80 of the tray. Specifically, the lateral arm 166 of the anterior reinforcement 164 extends along the anterior edge 170 on the lateral side of the polymer portion 80, while the medial arm 168 of the anterior reinforcement 164 extends along the anterior edge 170 at the medial side of the polymer portion 80 in a direction away from the lateral arm 166. A

The third arm 172 of the anterior brace 164 extends posteriorly away from the intersection of the lateral arm 166 with the medial arm 168.

As shown in FIG. 3, front gusset 164 has a pair of cutouts 174, 176 defined therein. Specifically, lateral cutout 174 is defined on lateral arm 166 of anterior brace 164, medial cutout 176 being defined on medial arm 168 of anterior brace 164.

In the embodiment of Figures 1 and 3, the posterior bolster 144 of the tibial tray 14 is contiguous with the anterior bolster 164 of the tray. Specifically, the third arm 152 of the rear gusset 144 is contiguous with the third arm 172 of the front gusset 164. However, other embodiments are contemplated, including arrangements in which the gussets are not contiguous. Furthermore, the two stiffeners 144, 164 are described herein as being of similar height, although the stiffeners could be made having different heights.

The two stiffeners 144, 164 may be formed in the polymer material as part of a molding process when the solid polymer portion 80 is molded into the porous portion 82. Alternatively, stiffeners 144, 164 may be formed by machining the polymer portion 80 after molding the solid polymer portion and the porous portion together. The cutouts 154, 156, 174, 176 may be formed in the polymer portion 80 by molding, machining, or other suitable processes. Some combinations of molding and machining could also be used to form the stiffeners 144, 164 and the cutouts 154, 156, 174, 176.

To secure the tibial bearing 16 to the tibial tray 14, the posterior tabs 140 of the bearing 16 are positioned in the posterior cutouts 154, 156 of the tibial tray 14. The anterior portion of the tibial bearing 16 is then advanced downwardly toward the tibial tray 14 such that the anterior appendages 142 of the tibial bearing 16 are deflected by the anterior reinforcement 164 and then snapped into the anterior cutouts 174, 176 of the previous reinforcement, thus securing the support 16 to the tray 14.

As the anterior portion of the abutment 16 advances downward in this manner, the ribs 144, 164 of the tibial tray 14 are captured between the pedestals 134, 138 of the distal surface 19 of the abutment. Specifically, as shown in Figure 2, the distal surface 19 of the abutment 16 has a posterior recess 178 and an anterior recess 180 defined therein. The posterior recess 178 is configured to complement the shape of the posterior reinforcement 144 of the tibial tray 14. That is, when the abutment 16 is secured to the tibial tray 14, the side walls of the pedestals 134, 138 defining the posterior recess 178 come into contact with the edges of the posterior reinforcement 144. In the same way, the anterior recess 180 is configured to complement the shape of the anterior reinforcement 164 of the tibial tray 14, that is, when the abutment 16 is secured to the tibial tray 14, the side walls of the pedestals 134, 138 which defining the front recess 180 contact the edges of the front gusset 164. The dimensions of the recesses 178, 180 and the gussets 144, 164 are selected such that a relatively tight fit is achieved. In this way, the support 16 is fixed relative to the tibial tray 14. In particular, the configuration of the braces 144, 164 and of the pedestals 134, 138 formed on the distal surface 19 of the support 16 prevent movement of the support 16. relative to the tibial tray 14 in the anterior / posterior direction and in the medial / lateral direction. On the other hand, the posterior appendices positioned in the cutouts 154, 156 and the anterior appendices 142 positioned in the cutouts 174, 176 prevent lifting of the support 16 from the tibial tray 14. The micro-movement of rotation is reduced, if not prevented entirely, by the relatively tight fit of the braces 144, 164 of the tibial tray 14 in the recesses 178, 180 of the support 16, in particular along the third arm 152 of the rear brace 144 and / or the third arm 172 of front brace 164.

A given design of a fixed bearing knee prosthesis is typically commercially available in a variety of different sizes, particularly in a variety of different widths. This is done to accommodate the many variations in size and anatomy of patients in a population. However, the configuration of the fixed knee prosthesis 10 of the present disclosure allows a high degree of flexibility with regard to the size of the tibial tray 14 and the support 16. Each of the individual trays 14 having a size (eg, width) which is different from the other trays 14 in the group, the basic configuration of the rear gusset 144 and front gusset 164 remain the same throughout the range of trays 14 of different sizes. Specifically, the location of the cutouts 154, 156 defined in the back reinforcement 144, respectively, remains the same throughout the range of trays 14 of different sizes. Although the rear cutouts 154, 156 remain in the same location throughout the range of trays 14 of different sizes, the width of the arms 146, 148 varies to accommodate the overall width of a given tray 14. In a similar manner, the location of the cutouts 174, 176 defined in the anterior reinforcement 164, respectively, remains the same throughout the range of trays 14 of different sizes, although the width of the arms 166, 168 varies to accommodate the total width of a given tray 14. The size and configuration of the third arms 152, 172 of the rear brace 144 and the front brace 164, respectively, remain unchanged throughout the range of different sized trays 14.

The supports 16 of different sizes can also be configured in this way. In particular, a plurality of supports 16 can be designed with each of said plurality of supports 16 having a different size, in particular a different width. However, each of the cited abutments 16 of different sizes may include mating features that are commonly sized and commonly located with the commonly sized and commonly located features of the tibial tray 14 that has been described.

ES 2 406 366 T3 above. In particular, each of the supports 16 in a range of differently sized supports may include a rear recess 178 and a front recess 180 that is positioned and dimensioned to fit snugly against the edges of the rear gusset 144 and front gusset 164, respectively. , from each of the tibial trays 14 in the entire range of trays 14 of different sizes.

The posterior appendages 140 are commonly dimensioned and commonly located throughout the range of supports 16 of different sizes in order to be positioned in the respective posterior cutouts 154, 156 of each of the tibial trays 14 throughout the range of trays 14. of different sizes. Similarly, the anterior appendages 142 are commonly sized and commonly located throughout the range of supports 16 of different sizes in order to be positioned in the respective anterior cutouts 174, 176 of each of the tibial trays 14 of the entire range of 14 trays of different sizes.

It should be appreciated from the foregoing explanation that the general configuration of the braces 144, 164 (including contiguous variations thereof) is the same throughout the range of tibial trays 14 of different sizes. In the same way, the general configuration of the recesses 178, 180 (including contiguous variations thereof) and the general configuration of the tabs 140, 142 are the same throughout the range of supports 16 of different sizes. In this manner, a number of supports 16 of different sizes can be attached to a given tibial tray 14. This provides the orthopedic surgeon with greater flexibility in being able to match the knee prosthesis 10 to the anatomy of a particular patient.

Other configurations of back gusset 144 and front gusset 164, as well as other configurations of locking mechanisms, are also contemplated. The details of the locking mechanisms for tibial trays and bearings for fixed bearing applications are disclosed in US-7628818 and US-A-2009/0082873.

To fabricate the tibial tray 14, 14A, 14B, 14C, the porous base or preform 84, 84A, 84B, 84C is first fabricated, using any suitable method, eg, as described above. The preform 84, 84A, 84B, 84C can be placed in a suitable molding apparatus and the material for the solid polymer portion 80, 80A, 80B, 80C (such as fiber-reinforced PEEK) is then molded onto the preform. For example, injection molding can be used.

During the molding process, some of the polymer flows over proximal surface 86, 86A, 86B of the porous base or preform 84, 84A, 84B and into holes 90, 92, 94, 96, 98, 90A, 92A, 94A , 96A, 98A, 90B, 92B, 94B, 96B, 98B of the preform. In the case of the first examples, the polymer flows through the holes and in the channels defined by the interior surfaces 100, 102, 104, 106, 108 of the extensions 30, 32, 34, 36, 38, and out of the holes 110, 112, 114, 116, 118 in the distal ends of the porous portions of the extensions to form the polymeric distal ends 40, 42, 44, 46, 48 and the distal outer surfaces 70, 72, 74, 76, 78 of extensions 30, 32, 34, 36, 38. In the case of the fourth example, during the molding process the polymer flows over the upper surface of the metal plate 200 and through the through holes of the plate 201, 203, 205, 207, 209 and into the through holes 90C, 92C, 94C, 96C, 98C of the porous preform 84C and exits the holes at the distal ends of the porous portions of the extensions to form the polymeric distal ends 40C, 42C, 44C, 46C, 46D, 46E and the distal outer surfaces of extensions 30C, 32C, 34C, 34D, 34E. As will be explained in more detail below, during the molding process, the polymer also flows through the through holes 211, 213, 215, 217 of the plate 200 and into the pores of the porous polymer of the four raised supports 219 , 221, 223, 225.

Along the interfaces of the polymer and the porous preform, some of the polymer flows into some of the pores of the preform 84, 84A, 84B, producing a structure such as that shown schematically in Figure 14, in FIG. that a region is formed with interspersed polymer and porous material to bond the polymer portion 80 to the porous base or preform 84. In the case of the fourth embodiment, the polymer will flow into the pores of the supports 219, 221, 223, 225 and will be interleaved as shown in figure 14 to join the two polymer portions 80C, 82C one to the other. , with the reinforcing plate 200 held therebetween. It should be understood that the use of the four porous supports 219, 221, 223, 225 represents a method of bonding the solid polymer portion 80C to the porous polymer portion 82C; For example, different numbers, sizes, and shapes of areas can be used on plate 200 that allow interleaving of the two polymers.

As noted above, locking features (such as reinforcement 144 and cutouts 154, 156, 174, 176) can be molded and / or machined or otherwise finished to form mounting surface 26, 26A, 26B, 26C of the tibial tray 14, 14A, 14B, 14C.

The cost of producing such a tibial tray is expected to be lower than the cost of producing a comparable size tibial tray made entirely of metal.

The composite tibial tray 14, 14A, 14B, 14C manufactured in this manner can be expected to have advantageous properties. For example, such a tibial tray is expected to have an effective stiffness (the stiffness of the composite construction that includes both the porous portion 82 and the polymer portion 80) less than that of a tibial tray in size and shape. similar made exclusively from standard biocompatible metal alloys. With such effective stiffness, it is envisaged that the tibial tray of the present

The invention provides optimal load transfer to underlying bone to minimize or prevent stress shielding and resulting bone loss.

Typically, a plurality of such different sized tibial trays would be included in a kit, along with a plurality of sizes of femoral components and rests. The surgeon or OR staff would then select the appropriate size of the tibial tray and support and mount them on a frame such as that shown in Figure 15. This set can be performed either before or after the tibial tray 14, 14A, 14B, 14C is implanted in the prepared tibia. When mounted in this manner, the distal mounting surface 19 of the abutment 16 contacts and abuts against the proximal mounting surface 26, 26A, 26B, 26C of the tibial tray 14, 14A, 14B, 14C. A suitable femoral component 12 is implanted, and articulated with bearing 16 as shown in Figure 15. In particular, the tibial tray 14, 14A, 14B, 14C is suitable for cementless implantation.

After implantation, it is anticipated that the bone will grow into the porous portion 82, 82A, 82B, 82C of the tibial tray 14, 14A, 14B, 14C. However, bone will not grow into the exposed solid polymer portion 80, 80A, 80B, 80C of the tibial tray 14, 14A, 14B, 14C. Therefore, it is anticipated that there will be bone ingrowth on the distal surface 28, 28A, 28B, 28C of the tibial platform 24, 24A, 24B, 24C. Furthermore, for the first illustrated embodiment, bone ingrowth is also anticipated at the outer proximal surfaces 60, 62, 64, 66, 68 of extensions 30, 32, 34, 36, 38 adjacent to the distal surface 28 of the tibial platform 24. A similar result is expected on the outer surfaces 60C, 62C, 66C of the extensions 30C, 32C, 36C and on the distal surface 28C shown in Figure 16. Radial pressure along proximal outer surfaces 60, 62, 64, 66, 68, 60C, 62C, 66C is expected to be uniform, to stimulate bone ingrowth in all directions on the stem and pins 30 , 32, 34, 36, 38, 30C, 32C, 36C. However, bone will not grow on the exposed polymer portions of the distal outer surfaces 70, 72, 74, 76, 78, 70C, 72C, 76C at the distal ends 40, 42, 44, 46, 48, 40C, 42c , 46C of extensions 30, 32, 34, 36, 38, 30C, 32C, 36C. Therefore, bone ingrowth should occur at the proximal end of the tibial tray, but not at the distal end. Furthermore, in each illustrated embodiment, the interfaces of the porous portion 82, 82A, 82B, 82C of the tray 14, 14A, 14B, 14C and the bone are all easily accessible from the tibial plateau.

The central stem 30, 30A, 30B, 30C is expected to provide stability against lifting of the tibial tray. The pins 32, 34, 36, 38, 32A, 36A, 32B, 36B, 32C, 36C surrounding the central stem 30, 30A, 30B, 30C are expected to reduce shear and micromotion proximally, especially after the bony inner growth.

If it becomes necessary to remove the tibial tray 14, 14A, 14B, 14C, the surgeon can cut along the distal surface 28, 28A, 28B, 28C of the platform 24, 24A, 24B, 24C of the tibial tray to cut the connection between the patient's bone and the platform 24A, 24B, 24C of the tibial tray 24. If the porous portion 82, 82A, 82B, 82C of the tibial tray 14, 14A, 14B, 14C is made of a material such as a metallic or polymer foam, the surgeon can also cut through all the extensions 30, 32 , 34, 36, 38, 30A, 32A, 36A, 30B, 32B, 36B, 30C, 32C, 36C at the junctions of the extensions and the distal surface 28, 28A, 28B, 28C of the tibial platform 24, 24A, 24B , 24C and easily remove the tibial platform 24, 24A, 24B, 24C. If the tibial tray 14, 14A, 14B, 14C is similar to the illustrated first and fourth embodiments, the surgeon can then cut around the outer perimeter of each extension 30, 32, 34, 36, 38, 30C, 32C, 36C to cut the connection between the bone and the porous proximal outer surfaces 60, 62, 64, 66, 68, 60C, 62C, 66C of the extensions 30, 32, 34, 36, 38, 30C, 32C, 36C. Each extension can then be easily removed. Notably, since bone ingrowth has not occurred at the distal ends of the extensions, the amount of bone that needs to be resected must be substantially less compared to a system using fully porous stems and pins.

Thus, the present invention provides a knee prosthesis with a modular tibial implant component suitable for cementless fixation. The tibial implant component can be easily removed from the bone in revision surgery to preserve native bone. The tibial implant may also have a lower modulus of elasticity than conventional solid titanium and cobalt-chromium alloy trays.

Implant components discussed above may have surfaces that do not contact bone or other portion of the implant component. For example, in the embodiments of Figures 1, 3, 5, 12, 13 and 16, the peripheral surface 250, 250A, 250B, 250C of the tibial tray 14, 14A, 14B, 14C extends between the surface 28, 28A , 28B, 28C for engagement with bone and proximal mounting surface 26, 26A, 26B, 26C. To avoid soft tissue irritation, this peripheral surface 250, 250A and 250B in the embodiments of Figures 1, 3, 5, 12 and 13 is part of the solid polymer portion 80, 80A, 80B of the tibial tray 14 , 14A, 14B, whereby the soft tissues are not irritated by contact with the porous portion 82, 82A, 82B of the tibial tray 14, 14A, 14B. In the embodiment of Figure 16, the porous portion 82C has reduced outer dimensions compared to the solid polymer portion 80C to avoid contact with soft tissue. Essentially, a substantial portion of the porous portion 82C fits into a pocket on the solid polymer portion 80C, while a portion of the porous portion 82C is lifted to thereby ensure that the surface 28C fully engages and transfers the load to the underlying bone.