US20030009230A1 - Surface sterilizable joint replacement prosthesis component with insert - Google Patents

Abstract

A joint prosthesis (10) including a first component (12)for cooperation with a first long bone (14) and a second component (16) for cooperation with a second long bone (20) is provided. The joint prosthesis (10) also includes a bearing component (222) positionable between the first component (12) and the second component (16) and cooperable with the first (12) and second (16) components. The bearing component (222) has a reinforcing component (236) having a first end (286) and a second end (294) and a polymeric material (207). The polymeric material (207) surrounds at least 99% of the surface area of the reinforcing component (236) and is molded to the reinforcing component (236) so that the material may be sterilized by a predominately surface sterilizing technology. The bearing component (222) defines a first peripheral region (271) and a second peripheral region (282). The first peripheral region (271) is adjacent to the first end (286) of the reinforcing component (236) and the second peripheral region (282) is adjacent the second end (244) of the reinforcing component (236). The first peripheral region (271) is cooperable with said first component (12) and the second peripheral region (282) is cooperable with the second component (16).

Description

CROSS REFERENCE TO U.S. PROVISIONAL PATENT APPLICATION
• This application is a Utility Application based upon U.S. Provisional Patent Application, Serial No. 60/302,115 filed Jun. 30, 2001, entitled SURFACE STERILIZABLE JOINT REPLACEMENT PROSTHESIS COMPONENT WITH INSERT.[0001]
CROSS-REFERENCE TO RELATED APPLICATIONS
• Cross reference is made to the following applications:[0002]
• DEP 677 titled “JOINT PROSTHESIS MOLDING METHOD AND DIE FOR PREFORMING THE SAME” and DEP 676 titled “JOINT REPLACEMENT PROSTHESIS COMPONENT WITH NON LINEAR INSERT” filed concurrently herewith which are incorporated herein by reference.[0003]
TECHNICAL FIELD OF THE INVENTION
• The present invention relates generally to the field of orthopaedics, and more particularly, to an implant for use in joint arthroplasty.[0004]
BACKGROUND OF THE INVENTION
• The invention relates to joint prostheses. More particularly, the invention is directed to tibial components of knee joint prostheses that can be configured to be either rotatable or non-rotatable.[0005]
• Joint replacement surgery is quite common and it enables many individuals to function normally when otherwise it would not be possible to do so. Artificial joints usually comprise metallic, ceramic and/or plastic components that are fixed to existing bone.[0006]
• Knee arthroplasty is a well known surgical procedure by which a diseased and/or damaged natural knee joint is replaced with a prosthetic knee joint. A typical knee prostheses include a femoral component, a patella component, a tibial tray or plateau, and a tibial bearing insert. The femoral component generally includes a pair of laterally spaced apart condylar portions, the distal surfaces of which articulate with complementary condylar elements formed in a tibial bearing insert.[0007]
• The tibial plateau is mounted within the tibia of a patient. Typically, the tibial bearing insert, which is usually made of ultra high molecular weight polyethylene (UHMWPE), is mounted upon the superior surface of the tibial plateau. The geometry and structure of the tibial bearing insert varies depending upon the needs and joint condition of a patient. Some tibial bearing inserts are designed to be used with joint prostheses that are implanted during procedures that retain one or both of the cruciate ligaments. Others are implanted after removal of one or both of the cruciate ligaments, and are thus structured to compensate for the loss of these ligaments. Yet other tibial bearing inserts are used with prostheses that provide enhanced stabilization to the knee joint.[0008]
• Recent total knee prostheses have been designed which allow for increased freedom of rotation between the femur and the tibia. To allow for this rotational motion, tibial bearing inserts have been designed which allow for rotation of the insert on the tibial tray or plateau. Typically the tibia bearing inserts have a central stem which rotationally engages centrally in the tibial stem of the tibial tray implant, thereby providing for the rotational motion. Typically, there are no rotational constraints between the tibial tray implant and the tibial bearing insert. Frequently, during total knee arthroplasty, the posterior cruciate ligaments are sacrificed and a substitute for the posterior cruciate ligaments is required. Orthopaedic implants for total knee arthroplasty have been developed which provide for the substitution of the posterior cruciate ligament. Examples of such implants include the PFC Sigma RP as described in U.S. Pat. No. 4,298,992 incorporated herein by reference, and the LCS Complete total knee prosthesis, both of which are sold by DePuy Orthopaedics, Inc., Warsaw, Ind.[0009]
• These total knee prostheses are designed with tibial components and femoral components which have in conjunction with their articulating surface, a spine and cam mechanism, which is used as a posterior cruciate substituting feature when the posterior cruciate of the knee is sacrificed.[0010]
• Such total knee replacement prostheses, which include a spine and cam mechanism, typically contain tibial bearing components manufactured from suitable plastic, usually UHMWPE. One such construction use for a class of total knee replacement prosthesis, which are known as constrained prosthesis, often incorporate metal reinforcement rods in the construction of the plastic bearing component. The bearing insert is constructed so that the metal rod lies within the bearing, and thus provides additional support for the central spine element of the bearing. Such components are typically manufactured by machining or molding the bearing component, drilling a central hole, and press fitting the reinforcing metal rod. An example of such a component is described in U.S. Pat. No. 5,007,933 to Sidebotham et al. hereby incorporated in its entirety by reference.[0011]
• In order to allow for desired kinematics of the knee during a full range of motion, the spine and cam mechanism on the tibial bearing insert may be placed in a suitable position, preferably anterior to the center line of the insert in the anterior/posterior direction. Designs of tibial inserts are available to help reconstruct knees where the stabilizing soft tissue compromises have been made or occurred due to various reasons. In such cases, the tibial bearing inserts are required to experience greater loads in the anterior/posterior and the medial/lateral directions. The constrained inserts may be reinforced with a metal rod, as mentioned earlier, to help distribute the loads experienced by the spine of the polyethylene tibial bearing.[0012]
• Total knee joint prostheses have been designed with the spine and cam mechanism on the tibial bearing insert placed in a position that the central axis of the distal stem portion of the insert that engages the tibial tray, and the axis of the superior spine portion that engages the cam of the femoral component, are not necessarily collinear.[0013]
• Unfortunately, this design does not allow for a straight rod, commonly employed for reinforcement of tibial bearing inserts, to be used.[0014]
• It should be appreciated that a first rod could be inserted inside the spine, and a second rod could be inserted in the stem of the tibial tray portion of the bearing insert. However, the load on the first rod would be transferred through the polymer portion of the insert to the second rod. The polymer strength would then limit the load carrying capacity of this configuration. Such a configuration may not provide the required strength to sufficiently support and reinforce the spine.[0015]
• The present invention is directed to providing a tibial bearing insert with sufficient strength at the spine to withstand the loads of the knee prosthesis in the anterior/posterior and medial/lateral direction, while preserving bearing wear resistance when the central axis of the distal stem of the insert and the axis of the superior spine are not necessarily co-linear.[0016]
SUMMARY OF THE INVENTION
• The present invention is directed to an improved joint prosthesis for total knee replacement which includes a spine and cam mechanism. The cam mechanism being on the femoral component and the spine being on the bearing component. The mechanism is capable of withstanding the greater loads experienced in the anterior/posterior and medial/lateral direction caused by the substitution of the cam and spine for the posterior cruciate ligament which may be sacrificed during total knee arthroplasty while preserving bearing wear resistance.[0017]
• The spine on the tibial bearing insert, according to the present invention, is placed anterior to the centerline of the insert in the anterior/posterior direction. Therefore, the distal stem portion of the insert which engages the tibial tray and the superior spine portion which engages the cam of the femoral component are not in the same plane. The tibial bearing insert of the present invention thus includes a rod placed internal to the tibial bearing insert which includes an offset feature.[0018]
• The knee prosthesis of the present invention thus includes a first polymeric component and a reinforcing component including a first portion on a first center line and a second portion on a second center line such that the first portion may engage the tibial tray and the second portion may be cooperating with the cam mechanism in the femoral component of the knee prosthesis.[0019]
• According to one embodiment of the present invention, there is provided a joint prosthesis including a first component for cooperation with a first long bone and a second component for cooperation with a second long bone. The joint prosthesis also includes a bearing component positionable between the first component and the second component and cooperable with the first and second components. The bearing component has a reinforcing component having a first end and a second end and a polymeric material. The polymeric material surrounds at least 99% of the surface area of the first component and is molded to the first component so that the material may be sterilized by a predominately surface sterilizing technology. The bearing component defines a first peripheral region and a second peripheral region. The first peripheral region is adjacent to the first end of the reinforcing component and the second peripheral region is adjacent the second end of the reinforcing component. The first peripheral region is cooperable with said first component and the second peripheral region is cooperable with the second component.[0020]
• According to another embodiment of the present invention, there is provided a knee prosthesis including a femoral component for attachment to a femur and a tibial tray for attachment to a tibia. The knee prosthesis also includes a bearing component positionable between the femoral component and the tibial tray for cooperation with the femoral component and the tibial tray. The bearing component includes a reinforcing component with a first end and a second end. The bearing component also includes a polymeric material. The polymeric material surrounds at least 99% of the surface area of the reinforcing component and is and molded to the reinforcing component, so that the material may be sterilized by a predominately surface sterilizing technology. The bearing component defines a first peripheral region and a second peripheral region. The first peripheral region is adjacent to the first end of the reinforcing component and the second peripheral region is adjacent to the second end of the reinforcing component. The first peripheral region is cooperable with the femoral component and the second peripheral region is cooperable with the tibial tray.[0021]
• According to yet another embodiment of the present invention, there is provided a bearing component. The bearing component is for use in knee joint arthroplasty. The bearing component is positionable between a femoral component and a tibial tray for cooperation with the femoral component and said tibial tray, the bearing component including a reinforcing component having a first end and a second end. The bearing component also includes a polymeric material surrounding at least 99% of the surface area of the reinforcing component, so that the material may be sterilized by a predominately surface sterilizing technology. The bearing component defines a first peripheral region and a second peripheral region. The first peripheral region is adjacent the first end of the reinforcing component and the second peripheral region is adjacent the second end of the reinforcing component. The first peripheral region is cooperable with the femoral component and the second peripheral region is cooperable with the tibial tray.[0022]
• According to another embodiment of the present invention, there is provided a method of manufacturing a polymeric bearing component for use in joint arthroplasty and for cooperation with a first joint component and a second joint component. The method includes the steps of providing a reinforcing support having a first end and a second end thereof and providing a molding die adapted for manufacturing the bearing component for use in joint arthroplasty and having a first mold portion and a second mold portion. The first mold portion is adapted to provide a first surface to cooperate with the first joint component and the second mold portion and is adapted to provide a second surface to cooperate with the second joint component. The method also includes the steps of providing a positioning member for cooperation with the reinforcing support and molding die and positioning the support in a desired position within the molding die. One of the first end and at the second end is located in the first mold portion. The method further includes the steps of maintaining the position of the support with the positioning member in intimate contact with the support and adding moldable polymeric material into the molding die. The method also includes the steps of substantially surrounding the support with the moldable material, heating and pressurizing the mold, and permitting the moldable material to cool to form the bearing component and during the cooling and forming of the moldable material, removing the positioning member from the support while maintaining a lower amount of one of heat and pressure on the mold and allowing the polymeric material to replace the space occupied by the positioning member The method also includes the step of removing the component from the molding die.[0023]
• If a total knee prosthesis requires removal from the patient and replacement with a new prosthesis, such replacement prosthesis typically engages further into the medullary canals of the femur and tibia. Such prostheses are called revision prosthesis. During the prosthesis replacement, cruciate ligaments are much more often sacrificed than in an initial or primary total knee arthroplasty. Currently, no revision tibial bearing inserts with rotational features include a spine which centerline is not aligned with the center of the distal stem portion of the insert which rotationally engages the tibial tray.[0024]
• Attempts have been made to reinforce polyethylene bearings. One such attempt is that as shown in U.S. Pat. No. 5,989,472 Ashby et al, incorporated herein by reference. The polyethylene bearing in Ashby includes a reinforcement feature for bone attachment. The reinforcement feature is to assist in eliminating motion between the polyethylene and the metal backing.[0025]
• Another attempt at reinforcing a polyethylene bearing is described in U.S. Pat. No. 4,997,445 to Hodoreck incorporated herein by reference. This patent describes a metal backed prosthesis implant with enhanced bonding of polyethylene to the metal base.[0026]
• Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions and claims.[0027]
BRIEF DESCRIPTION OF THE DRAWINGS
• For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in connection with the accompanying drawings, in which:[0028]
• FIG. 1 is a perspective view of the knee system including the bearing component of the present invention showing the femoral component and the tibial tray component with the tibial bearing showing the knee system in extension;[0029]
• FIG. 2 is an elevation view from the anterior of FIG. 1;[0030]
• FIG. 3 is a side view of the assembly shown in FIGS. 1 and 2;[0031]
• FIG. 4 is an exploded side view showing the plastic bearing component partially removed from the tibial tray or plateau;[0032]
• FIG. 5 is an elevation view from the posterior of FIG. 1;[0033]
• FIG. 6 is an exploded elevation view from the anterior showing the plastic bearing component partially removed from the tibial tray or plateau;[0034]
• FIG. 7 is an exploded perspective view showing the plastic bearing component partially removed from the tibial tray or plateau;[0035]
• FIG. 8 is a fully exploded side view showing the plastic bearing component removed from the tibial;[0036]
• FIG. 9 is a fully exploded elevation view from the anterior showing the plastic bearing component removed from the tibial;[0037]
• FIG. 10 is a plan view of a reinforcing rod for use with the bearing component for an embodiment of the prosthesis of the present invention;[0038]
• FIG. 10A is a view of the reinforcing rod of FIG. 10 along the[0039]line10A-10A in the direction of the arrows;
• FIG. 11 is a plan view of the reinforcing rod of FIG. 10 located in a molding die for use in manufacturing the bearing component for the prosthesis of the present invention;[0040]
• FIG. 12 is a plan view of the reinforcing rod of FIG. 10 located in a molding die shown partially in cross section for use in manufacturing the bearing component for the prosthesis of the present invention showing the molding die in greater detail;[0041]
• FIG. 13 is a bottom view of the molding die of FIG. 12;[0042]
• FIG. 14 is a plan view of the bearing component made from the reinforcing rod of FIG. 10 utilizing the molding die of FIG. 12;[0043]
• FIG. 15 is a plan view of a reinforcing rod for use with the bearing component for another embodiment of the prosthesis of the present invention;[0044]
• FIG. 15A is a view of the reinforcing rod of FIG. 10 along the[0045]line15A-15A in the direction of the arrows;
• FIG. 16 is a plan view of the reinforcing rod of FIG. 15 located in a molding die for use in manufacturing the bearing component for the prosthesis of the present invention;[0046]
• FIG. 17 is a plan view of the reinforcing rod of FIG. 15 located in a molding die shown partially in cross section for use in manufacturing the bearing component for the prosthesis of the present invention showing the molding die in greater detail;[0047]
• FIG. 18 is a bottom view of the molding die of FIG. 16;[0048]
• FIG. 19 is a plan view of the bearing component made from the reinforcing rod of FIG. 15 utilizing the molding die of FIG. 16;[0049]
• FIG. 20 is a process flow chart for a method of manufacturing the prosthesis component of FIG. 21;[0050]
• FIG. 21 is a side view of the assembly shown in FIGS. 1 and 2 showing the assembly in flexion;[0051]
• FIG. 22 is a perspective view of the knee system of FIG. 1 including the bearing component of the present invention showing the femoral component and the tibial component with the tibial bearing showing the knee system in flexion;[0052]
• FIG. 23 is an elevation view from the anterior side of the assembly shown in FIGS. 1 and 2 showing the assembly in flexion; and[0053]
• FIG. 24 is an elevation view from the posterior side of the assembly shown in FIGS. 1 and 2 showing the assembly in flexion.[0054]
DETAILED DESCRIPTION OF THE INVENTION
• Embodiments of the present invention and the advantages thereof are best understood by referring to the following descriptions and drawings, wherein like numerals are used for like and corresponding parts of the drawings.[0055]
• According to the present invention and referring now to FIG. 8, a joint prosthesis in the form of[0056]knee prosthesis10 as shown. Theknee prosthesis10 includes a femoral component or firstjoint component12 for attachment to femur or firstlong bone14. Theprosthesis10 further includes a tibial tray or secondjoint component16 for attachment to tibia or secondlong bone20. Thefemoral component12 and thetibial component16 are shown in greater detail in FIGS.1-9 and21-24. Thefemoral component12 and thetibial component16 are made of any suitable durable material which are biologically compatible with the human anatomy. Thefemoral component12 and thetibial component16 may, for example, be made of a metal alloy, for example, cobalt-chromium-molybdenum, a titanium and its alloys, or be made of stainless steel.
• The[0057]knee prosthesis10 further includes abearing component222. Thebearing component222 is positionable between thefemoral component12 and thetibial tray16. Thebearing component222 cooperates with thefemoral component12 and thetibial tray16 to provide for the kinematics of the knee prosthesis.
• The prosthesis, as shown in FIGS.[0058]1-9 and21-24, are commonly referred to as a mobile bearing prosthesis or a mobile bearing knee. Such mobile bearing knees have been provided by DePuy Orthopaedics, Inc. under the trade name LCS since about 1977. Mobile bearing knees of this type are different than fixed bearing knees in that thetibial component20 and thebearing component222 may be physically separated from each other. The bearing component is also allowed to have rotational freedom about the tibial tray component. The use of mobile bearing knees may require that the patient have satisfactory cruciate collateral ligaments and tendons necessary to maintain the proper relationship of the femoral component to the bearing component. In those cases where the cruciate ligaments are either severely damaged or have been sacrificed or removed during a knee surgery, provisions must be made within the prosthesis to constrain the femoral component with respect to the tibial tray.
• Referring now to FIGS. 21 and 22, one solution to restraining the[0059]femoral component12 with respect to thetibial tray16 is by the use of a mechanism in the form of aspine24 located on thebearing component222 which mates withcam26 located onfemoral component12. As shown in FIGS. 21 and 22, to provide medial/lateral support for theknee prosthesis10 preferably thefemoral component12 includesfemoral face30 which cooperate with spine faces32 on thespine24. The spine faces32 define a spine width SW which is related to the femoral width CW defined by femoral faces32. The relation behind SW & CW define the level of constraint in the prosthesis in the medial-lateral direction.
• Referring now to FIG. 8, to provide anterior support the[0060]spine24 includes acam cooperating face34 with which thespine cooperating face35 of thecam26 cooperates (see FIG. 21). It should be appreciated that for patients in which the posterior cruciate is severely damaged or missing the forces on thespine24 both anterior/posterior and medial/lateral can be quite severe.
• Preferably, and as shown in FIG. 8, the[0061]bearing component222 is made of a polymeric material, for example, polyethylene. Preferably, thebearing component222 is made of UHMWPE. Thebearing component222 may be further processed to improve the wear properties ofcontact surface40 of the bearing component. Thecontact surface40 is the surface that is in contact with the laterally spaced condylarouter periphery42 of thefemoral component12. Methods of improving the wear properties of UHMWPE include a process known as Gamma Vacuum Foil (GVF) as disclosed in U.S. Pat. No. 5,577,368 to Hamilton, et al, and a process known as the Marathon® process as disclosed in U.S. Pat. No. 6,017,975 and U.S. Pat. No. 6,242,507 to Saum et al and in U.S. Pat. No. 6,228,900 to McKellop et al. These patents are incorporated herein by reference.
• Referring again to FIG. 8 and according to the present invention, the[0062]bearing component222 of theprosthesis10 includes a first component or reinforcingcomponent236. The reinforcingcomponent236 serves to strengthen thebearing component222 so that thespine24 may withstand the forces that are present in the spine of theknee prosthesis10 when the posterior cruciate and collateral ligaments cannot support the knee properly.
• Since the[0063]bearing component222 is preferably made of a polymer and since the reinforcingcomponent236 is to strengthen thebearing component222, the reinforcingcomponent236 is preferably made of a higher strength material than polymer, preferably a material with a higher modulus of elasticity. For example, the reinforcingcomponent236 may be made of a metal that is a material compatible with the human anatomy, for example, stainless steel, a titanium and its alloys or a cobalt-chromium-molybdenum alloy.
• Applicants have found that desired kinematics of the knee during a full range of motion may require that an optimum design of the components that comprise a knee prosthesis, for example, those of FIG. 8, may include a[0064]tibial tray16 having acentral pivot axis44 which is not coincident withcenter line46 of thespine24 of thebearing component222. Since theprosthesis10 including thebearing component222 will be implanted into the human body, it is essential that theprosthesis10 including thebearing component222, be sterilized. Several effective methods of sterilization are possible for theprosthesis10 including thebearing component222.
• For example, the[0065]bearing component222 may alternatively be sterilized by subjecting thebearing component222 to gamma irradiation. The subjection of thebearing component222 to gamma irradiation may lead to the presence of free radicals within the polymer or polyethylene with which thebearing component222 is typically manufactured. The presence of free radicals within thebearing component222 may lead to early degradation of thebearing component222 through an oxidation process.
• To minimize the negative effect of the free radicals generated from gamma sterilization, the[0066]bearing component222 preferably is barrier packaged in vacuum or inert gas to keep the oxygen out and also to trap hydrogen gas inside the package. Such treatment precludes early oxidation of the bearing material and sufficient sterilization for thebearing component222.
• According to the present invention, a preferred method of sterilization is gas plasma sterilization. Gas plasma sterilization is predominantly a surface sterilizing technology. Gas plasma sterilization has limited ability to sterilize internal surfaces which have limited exposure to the outer surfaces of the component.[0067]
• Therefore, and according to the present invention, there is the need for a bearing component designed to be amenable to gas plasma sterilization and yet have the reinforced spine necessary for use of a constrained mobile bearing knee prosthesis for use with patients having compromised or sacrificed cruciate ligaments.[0068]
• According to the present invention and now referring to FIGS. 15 through 19, an embodiment of the present invention is shown as bearing[0069]component222.
• Referring now to FIG. 19, the[0070]bearing component222 of the present invention is shown in greater detail. Thebearing component222 is a component that may be molded as a net shaped molding including a reinforcing component or reinforcingrod236 to provide sufficient strength for thespine224 and the distal stem. The reinforcing rod includes afirst end286 and an opposedsecond end294. Thebearing component222 is designed to not include bearing component openings in the polyethylene portion of the bearing component to expose the reinforcing rod to atmosphere. The technology that permits this configuration will be described in greater detail herein.
• By providing the[0071]bearing component222 with no external exposure to the reinforcing rod, thebearing component222 may be gas plasma sterilized. By gas plasma sterilizing thebearing component222, thebearing component222 may be sterilized without providing free radicals which could lead to oxidative degradation of the bearing material.
• Referring now to FIG. 19 and according to the present invention, the[0072]bearing component222 of theprosthesis10 includes the reinforcingcomponent236 which is designed to accommodate the fact thatcenterline44 of the central pivot stem of the tibial tray16 (see FIG. 8) and is offset fromcenterline46 of thespine24.
• Thus, as shown in FIG. 19, the reinforcing[0073]component236 is designed with afirst centerline250 which is not coincident withsecond centerline252. As shown in FIGS. 8 and 10, thefirst centerline250 of the reinforcingcomponent236 is coincident with central pivot stemcenterline44 oftibial tray16. Similarly thesecond centerline252 of the reinforcingcomponent236 is coincident with thecenterline46 of thespine24.
• Continuing to refer to FIG. 19, the reinforcing[0074]component236 includes afirst portion254 which defines thefirst centerline250 thereof. The reinforcingcomponent236 further includes asecond portion256 thereof which-defines-thesecond centerline252 thereof. Thefirst centerline250 and thesecond centerline252 are non-coincidental.
• As shown in FIG. 19, the[0075]first centerline250 may be parallel and spaced from thesecond centerline252. It should be appreciated, however, that thefirst centerline250 and thesecond centerline252 may, in fact, be skewed or converging or diverging. As shown in FIG. 19, however, thefirst centerline250 and thesecond centerline252 are separated and offset a distance COO which is similar to the offset SOO between the centerline of46 ofspine24 and thecenterline44 of the tibial tray16 (see FIG. 8).
• As shown in FIG. 19, the reinforcing[0076]component236 includes a connectingportion260 positioned betweenfirst portion254 andsecond portion256. The connectingportion260 may have any suitable shape but preferably for strength and simplicity the connectingportion260 is an arcuate portion. In such a configuration, the shape of the connectingportion260 is defined by a pair of radii, RR1 and RR2 which may, for example, be similar.
• While it should be appreciated that the reinforcing[0077]component236 may have any suitable shape capable of providing for support with a pair of offset centerlines, it should be appreciated that for simplicity, and as shown in FIG. 15A, the reinforcingcomponent236 may have a uniform cross section. For example, the cross section of the reinforcing component may be square, triangular, hexagonal or as shown in FIG. 15A, may be circular. A circular cross section may provide for optimum bending strength in a variety of directions for a given weight or size of the reinforcingcomponent236.
• The reinforcing[0078]component236 may be hollow or as shown in FIG. 18, may be made of a generally solid material. Due to space constraints, the reinforcingcomponent236 may be solid as shown in FIG. 18.
• As can be readably apparent by FIGS. 15 and 19, in particular, the[0079]bearing component222 including the reinforcingcomponent236 may be made by a number of methods but cannot simply and easily be made by first making thebearing component222 and then preparing an opening or conduit for installing the reinforcingcomponent236 therein. Therefore, typical methods of providing a reinforcing rod to abearing component222 in the form of drilling a hole in thebearing component222 and inserting a straight cylindrical rod therein is not possible.
• Referring now to FIG. 19, the reinforcing component or reinforcing[0080]rod236 is shown in greater detail. Thebearing component222 includes the reinforcingrod236 which is placed into a mold and the polymeric material is molded around the reinforcingrod236. Thus, thebearing component222 requires that the mold provide provisions for the proper placement of the reinforcingrod236 within the molding die. Therefore, and as shown in FIG. 19, the reinforcingrod236 includes an orientation andlocation feature202 which provides both orientation and location. The location andorientation feature202, as shown in FIG.15, include a first recess or throughhole204 and a second recess or throughhole206.
• Preferably, the[0081]first recess204 and thesecond recess206 are small. The first recess andsecond recess204 and206 in the reinforcingrod236 are preferably both located on the same portion of the rod. By placing the recesses on the same portion, for examplesecond portion256, the recesses may be both positioned in the base orbottom mold266 of the die262 (see FIG. 17) to assist in the proper operation of the invention. The value of having the recesses on the same end of the rod will be described in greater detail herein.
• Referring now to FIG. 17, a[0082]molding die262 is shown for molding thebearing component222. Molding die262 is utilized in the direct compression molding process. Thebearing component222 is molded in the molding die262 in reverse or upside down order to provide for the positioning of therecesses204 and206 in the base orbottom mold266.
• The advantage of positioning the location and orientation features[0083]202 in the base orbottom mold266 will be described in greater detail later.
• As shown in FIG. 17, the molding die[0084]262 includes base orbottom mold266. Thebottom mold266 is utilized to formbottom bearing surface280 and rotating shaft or secondperipheral region282 of thebearing component222. Extending upwardly from thebottom mold266 is the body orside mold272. Theside mold272 is utilized to formcurved profile274 of thebearing component222. Slidably positioned within theside mold272 is plunger ortop mold270. The plunger ortop mold270 is utilized to form articular surface or firstperipheral region271 of thebearing component222. Themolds270,272 and266 serve to provide an inner formingsurface264 which conforms to the outer periphery of thebearing component222 with provisions for accommodating the shrinkage dimensions that are well known in the art.
• The inner forming[0085]surface264 defines aninternal cavity208.
• The reinforcing[0086]rod236 needs to be properly positioned within thecavity208 of the molding die262. Preferably, thus, the molding die262 includes apositioner284 for proper repositioning of the reinforcingrod236 within thecavity208 of the molding die262. For example and as shown in FIG. 17, thepositioner284 is in the form of afirst pin290 and asecond pin292. Thepins290 and292 cooperate withfirst recess204 andsecond recess206 of the reinforcing rod236 (see FIG. 19).
• Preferably, and according to the present invention, the[0087]pins290 and292 have a very small dimension with respect to the reinforcingrod236. For example, if, as shown in FIG. 17, thepins290 and292 are cylindrical, thepins290 and292 may have a diameter D which is much smaller than diameter DD of thesecond portion256 of the reinforcingrod236. For example for a reinforcingrod236 having a diameter DD of, for example, approximately 10 millimeters. The corresponding diameter D of thepins290 and292 may be, for example, 0.5 to 2.0 millimeters.
• It is preferred to have the[0088]pins290 and292 made of materials that have a high melting point in order to resist the heat and pressure experienced in the mold during the molding process. Pins may be made of metals, ceramics or pyrolytic carbons. The molding process for the molding die262 to mold thebearing component222 as shown in FIG. 17 includes first separating thetop mold270 from thebottom mold266 and addingpowder207 similar topowder112 of the process as described for the molding die62 of FIG. 12. After the requiredpowder207 is added, thetop mold270 is placed within theside mold272 and lowered in the direction of thebottom mold266 until themolds266,270 and272 formingsurface264 correspond to the periphery of thebearing component222.
• Towards the end of the compression molding cycle when the UHMWPE material has almost assumed full density and completely fills the mold the[0089]pins290 and292 are withdrawn from the cavity preferably in a direction normal to thecenterlines250 and252 of the reinforcingrod236. For example, as shown in FIG. 17, the first pin moves from a position as shown in solid to the position shown in phantom. As thefirst pin290 andsecond pin292 are retracted to the position in phantom, asmall pin cavity238 is left behind where thepin290 was withdrawn from. Since the compression cycle has not ended, the melted polymer still under pressure quickly fills thepin cavity238 thereby eliminating thepin cavity238.
• Since the[0090]powder207 within themold cavity208 has obtained a high viscosity at the point in the compression molding cycle when the UHMWPE material has assumed full density and completely fills the mold, the reinforcingrod236 remains in its previous position even after thepins290 and292 have been fully retracted and no longer support therod236.
• Preferably, and as shown in FIG. 17, the[0091]pins290 and292 are preferably spaced apart along second centerline250 a distance P of, for example, twice the distance DD of the diameter of therod236. The larger the dimension P, the greater the stability and accuracy of the positioning of therod236 within the molding die262.
• Preferably, and as shown in FIG. 17, the[0092]pins290 and292 are positioned perpendicularly to thesecond centerline250 and preferably at an angle with respect to each other, preferably at 90 degrees or perpendicular to each other. Such positioning optimizes the effectiveness of thepins290 and292 to properly position the reinforcingrod236 in more than 3 degrees of freedom. After appropriate cooling, the plunger ortop mold270 is opened and the completedbearing component222 is removed from the molding die262.
• It should be appreciated that other approaches may be taken to position the reinforcing[0093]rod236 within the molding die262 and yet provide for a complete encapsulation of the reinforcing rod with the polyethylene. For example, thepins290 and292 may be made of a polyethylene identical to that of thepowder207. Thepins290 and292 may then be left fully extended and not retracted. Thepins290 and292 then would melt and form with thepowder207, and yet have sufficient strength early on in the forming process to properly locate therod236 within the molding die262 until the polyethylene becomes sufficiently viscous to support the rod.
• Other approaches for properly supporting the rod yet allowing for complete encapsulation of polyethylene around the[0094]rod236 may fall within the scope of the present invention.
• According to the present invention and now referring to FIGS. 10 through 14, another embodiment of the present invention is shown as bearing[0095]component22.
• Referring to FIG. 8 it should be appreciated that the bearing[0096]component22 of FIG. 10 may be substituted for thebearing component222 for theprosthesis10. The bearingcomponent22 is made of similar materials and has similar strength and load carrying capacity of bearingcomponent222 as well as similar contour dimensions such that bearingcomponent22 can readily replacebearing component222 in theprosthesis10.
• Referring now to FIG. 10 an alternate embodiment of the bearing component of the present invention is shown as the bearing[0097]component22 which may alternatively be used inprosthesis10.Bearing component22 includes the reinforcingcomponent36 which is designed to accommodate the fact thatcenterline44 of the central pivot stem of thetibial tray16 is offset fromcenterline46 of the spine24 (see FIG. 8). Thus as shown in FIG. 10, the reinforcingcomponent36 is designed with afirst centerline50 which is not coincident withsecond centerline52. As shown in FIGS. 8 and 10, thefirst centerline50 of the reinforcingcomponent36 is coincident with central pivot stemcenterline44 oftibial tray16. Similarly thesecond centerline52 of the reinforcingcomponent36 is coincident with thecenterline46 of thespine24.
• Continuing to refer to FIG. 10, the reinforcing[0098]component36 includes afirst portion54 which defines thefirst centerline50 thereof. The reinforcingcomponent36 further includes asecond portion56 thereof which defines thesecond centerline52 thereof. Thefirst centerline50 and thesecond centerline52 are non-coincidental.
• As shown in FIG. 10, the[0099]first centerline50 may be parallel and spaced from thesecond centerline52. It should be appreciated, however, that thefirst centerline50 and thesecond centerline52 may, in fact, be skewed or converging or diverging. As shown in FIG. 10, however, thefirst centerline50 and thesecond centerline52 are separated and offset a distance CO which is similar to the offset SO between the centerline of46 ofspine24 and thecenterline44 of the tibial tray16 (see FIG. 8).
• As shown in FIG. 10, the reinforcing[0100]component36 includes a connectingportion60 positioned betweenfirst portion54 andsecond portion56. The connectingportion60 may have any suitable shape but preferably for strength and simplicity the connectingportion60 is an arcuate portion. In such a configuration, the shape of the connectingportion60 is defined by a pair of radii, R1 and R2 which may, for example, be similar.
• While it should be appreciated that the reinforcing[0101]component36 may have any suitable shape capable of providing for support with a pair of offset centerlines, it should be appreciated that for simplicity, and as shown in FIG. 10A, the reinforcingcomponent36 may have a uniform cross section. For example, the cross section of the reinforcing component may be square, triangular, hexagonal or as shown in FIG. 10A may be circular. A circular cross section may provide for optimum bending strength in a variety of directions for a given weight or size of the reinforcingcomponent36.
• The reinforcing[0102]component36 may be hollow, or as shown in FIG. 10A may be made of a generally solid material. Due to space constraints the reinforcingcomponent36 may be solid as shown in FIG. 10A.
• As can be readably apparent by the FIGS. 8 and 10, in particular, the bearing[0103]component22, including the reinforcingcomponent36, may be made by a number of methods but cannot simply and easily be made by first making the bearingcomponent22 and then preparing an opening or conduit for installing the reinforcingcomponent36 therein. Therefore, typical methods of providing a reinforcing rod to abearing component22 in the form of drilling a hole in thebearing component22 and inserting a straight cylindrical rod therein is not possible.
• Therefore, referring to FIGS. 11, 12 and[0104]13, the bearingcomponent22 is preferably made by a molding process for example a compression molding process or any molding process by which the polymeric material may be processed.
• Referring to FIGS. 11, 12 and[0105]13, the bearingcomponent22 is preferably made in molding die62. While the bearingcomponent22 may be manufactured utilizing any suitable molding technique preferably and as shown in FIG. 12, the molding die62 is for use with direct compression molding. Plastic powder is placed into the molding die62, the die is closed and pressure is applied to compress, heat, and cause flow of the plastic to be conformed to the cavity shape.
• The molding die[0106]62 is made in a shape including an inner formingsurface64 which is made in the shape of the final finished bearingcomponent22. Preferably, the inner formingsurface64 is sized to allow for appropriate shrinking dimensions as is known in the art.
• The molding die is made in several pieces. Typically, a base or[0107]bottom mold66 is utilized to formarticular surface70 of the bearingcomponent22. The molding die62 also includes a body orside mold72. Thebody72 is utilized to form the curved lateral surfaces74 of the bearingcomponent22. Also the molding die62 further includes aplunger assembly76. Theplunger assembly76 is utilized to formbottom bearing surface80 and therotating shaft82. One mold may be used to obtain varying thickness of the bearingcomponent22.
• In order to manufacture the bearing[0108]component22 according to the present invention, the molding die62 is modified to support reinforcingcomponent36 in the form of, for example, a reinforcing rod.
• Preferably, and as shown in FIG. 12, reinforcing rod or[0109]component36 is position spaced from the inner formingsurface64. Preferably, and as shown in FIG. 12, the reinforcingrod36 is kept spaced from the inner formingsurface64 by use of asupport feature84 as initially designed to provide the offset between the spine and distal stem of the bearingcomponent22. Thesupport feature84 is utilized to space, support or position the reinforcingrod36 within the molding die62. The positioner orsupport feature84 may support or secure the reinforcingcomponent36 at any suitable position on the reinforcingcomponent36. For simplicity, and as shown in FIG. 12, thepositioner84 may be located onfirst end86 of the reinforcingrod36.
• The[0110]positioner84 may include a sole positioning member which interacts withfirst end86 of the reinforcingrod36. If the positioner is located only on one end and the rod is held at that one end, that portion of the die including the positioner either at the base orbottom mold66 or the plunger ortop mold76 must provide rigid temporary attachment of the reinforcingrod36 to thepositioner84.
• While the present invention may be practiced utilizing a sole positioner located on one end of the reinforcing[0111]rod36 such a configuration may have some problems in that the tolerance between the positioner and the reinforcing rod may be such that the accuracy of the position of the reinforcingrod36 within the molding die62 may not be sufficiently accurate resulting in the misposition of the reinforcingrod36 within the finished reinforcingcomponent36. Misposition may occur either in the anterior-posterior or medial-lateral direction. Additionally, the reinforcingpin36 may be rotationally mispositioned with respect to the superior spine and distal stem.
• Preferably, and as shown in FIG. 12, the[0112]positioner84 is in the form of afirst positioner90 located at thefirst end86 of the reinforcingrod36 and asecond positioner92 located atsecond end94 of the reinforcingrod36. If the reinforcingrod36 is held at both thefirst end86 and thesecond end94 of therod36, then one end, for example, end86 must be a rigid temporary attachment and the other end, for example,second end94 orsecond positioner92 must be a sliding temporary attachment. A sliding temporary attachment is necessary as the two ends of the molding die approach and separate from each other during each molding cycle. Additionally, the sliding temporary attachment may provide for rotational alignment to obtain the optimal position of the reinforcingcomponent36 in the spine by allowing equal polymeric material around the reinforcingcomponent36.
• To improve the accuracy of the positioning of the reinforcing[0113]rod36 within the molding die62, optionally, the molding die may include anorientation feature100 to optimally angularly orient the reinforcingrod36 with respect to the inner formingsurface64 and eventually the reinforcingcomponent36. Theorientation feature100 may, for example, be included with thepositioners90 and92 and may, as shown in FIG. 12, be in the form of flat102 located on thesecond positioner92. As shown in FIG. 12, theorientation feature100 is in the form of six equally spaced flats, three of which are shown. Therefore thepositioner84 and the orientation features are in the form of a hexagonal rod. An additional flat may help better fine tune the position of the reinforcing element with respect to the mold components.
• Referring again to FIG. 10, preferably, and as shown in FIG. 10, the reinforcing[0114]rod36 includes positioning features in the form of, for example,first recess104 which is located onfirst end86 of therod36 andsecond recess106 which is located onsecond end94 of therod36. Thefirst recess104 matingly receives thefirst positioner90 while thesecond recess106 receives the second positioner92 (see FIG. 11). Preferably, and as shown in FIG. 10, thesecond recess106 includes a recess flat110 which mate with flat102 onsecond positioner92.
• Referring now to FIG. 14, the bearing[0115]component22 is shown having been molded on the molding die62 (see FIG. 12). In order that thefirst positioner90 and thesecond positioner92 may be removed from thecavity114 and from the bearingcomponent22 when it is removed from thecavity114 of the molding die62, the bearingcomponent22 includes a firstbearing component opening120 located in line and above thefirst recess104 of the reinforcingrod36. Likewise, the bearingcomponent22 further includes a secondbearing component opening122 extending outwardly from thesecond recess106 of the reinforcingrod36. Thefirst bearing component120 and the secondbearing component opening122 provide for access to the reinforcingrod36 from the outside of the bearingcomponent22.
• Referring again to FIG. 12,[0116]plastic powder112 is added in the proper amount intocavity114 of the molding die62. The molding die62 is closed by the positioning of the plunger assembly ortop mold76 over the body orside mold72 of the molding die62.
• The[0117]bearing component22 is fully formed by subjecting the molding die62 to the well known conditions of pressure and temperature required to consolidate thepowder112. After appropriate cooling, the molding die62 is opened by the removal of the plunger assembly ortop mold76 from the body orside mold72. The bearingcomponent22 including the reinforcingrod36 is then removed from thecavity114 of the molding die62. After proper cleaning an additional reinforcement rod andadditional powder112 is added to thecavity114 and the process is repeated in order to obtain a second bearing component.
• Referring now to FIG. 14, the bearing[0118]component22 of the present invention includes firstbearing component opening120 and secondbearing component opening122 which expose thebearing component22 to access the reinforcingrod36. The reinforcing rod thus has internal surfaces which have limited exposure or connection to the outside surfaces of the bearingcomponent22.
• Therefore, because the reinforcing rod,[0119]36 is exposed to the surface of the component via theholes120 and122 through which it was inserted or by the method of holding the post using the mold which holds the post during the molding process, the bearingcomponent22 is not amenable to sterilization by techniques which are predominantly surface sterilizing technology, for example, gas plasma sterilization.
• In order to utilize the[0120]bearing component22 with gas plasma sterilization, steps can be taken to fill theholes120 and122 with polyethylene plugs or thepositioners90 and92 can be made of polyethylene and not retracted once the bearing22 is removed from the die62 (see FIG. 12).
• Referring now to FIG. 20, a process for molding a bearing component with a reinforcing rod is described more fully.[0121]First step120 of the process described in FIG. 20 is the step of providing a component of a durable material. The durable material may, for example, be in the form of cobalt chrome alloy, stainless steel or titanium and its alloys. The component may be in the form of, for example, an elongated member, for example, a rod. The rod as described in the present invention is in the form of a bent rod or a rod having two substantially linear portions with the portions being skewed or non-linear with respect to each other.
• [0122]Second step122 of the process, as described in FIG. 20, is the step of providing a molding die adapted for manufacturing a component for use in total joint arthroplasty.
• [0123]Third step124 in the process is the step of placing the reinforcing component into the molding die in the desired position.Fourth step126 of the process is placing moldable material powder into the molding die.Fifth step130 in the process for making a bearing component is the step of substantially surrounding the component with moldable material.Sixth step131 of the process is the step of heating and pressurizing the mold, thus the moldable material.Seventh step132 of the process is the step of permitting the moldable material to cool to form the component and theeighth step134 of the process is the step of removing the component from the molding die.
• By utilizing the non-linear reinforcement component of the present invention, a knee may be provided with improved load carrying capacity in the anterior-posterior and medial-lateral directions for the spine and cam mechanism in situations in which the center line of the insert which engages the tibial tray and the superior spine portion which engage the cam of the femoral component are not in the same plane. In such situations where these planes are different, the kinematics of the knee may be improved.[0124]
• By providing a tibial bearing insert with an insert that has most of its entire periphery encapsulated in polyethylene, a tibial bearing insert can be made that has improved strength and can be gas plasma sterilized.[0125]
• By providing a non-linear re-inforcing component to the tibial bearing insert, the non-linear support rod may be properly positioned within the tibial bearing insert to optimize the load transfer mechanism through the spine.[0126]
• By providing a tibial bearing insert including a nonlinear support including an orientation feature, the support rod may be adjusted with respect to the tibial bearing insert during the manufacturing of the tibial bearing insert.[0127]
• Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.[0128]

Claims (32)

What is claimed is:

1. A joint prosthesis, comprising:

a first component for cooperation with a first long bone;

a second component for cooperation with a second long bone; and

a bearing component positionable between said first component and said second component and cooperable therewith, said bearing component including a reinforcing component having a first end and a second end thereof and a polymeric material surrounding at least 99% of the surface area of the reinforcing component and molded thereto, so that the material may be sterilized by a predominately surface sterilizing technology, said bearing component defining a first peripheral region thereof and a second peripheral region thereof, the first peripheral region being adjacent the first end of the reinforcing component and the second peripheral region being adjacent the second end of the reinforcing component, the first peripheral region being cooperable with said first component and the second peripheral region being cooperable with said second component.

2. The joint prosthesis ofclaim 1, wherein the predominately surface sterilizing technology comprises a gas plasma spray process.

3. The joint prosthesis ofclaim 1, wherein said polymeric material extends normally from the surface of said reinforcing component a distance of at least 5 millimeters.

4. The joint prosthesis ofclaim 1, wherein said polymeric material surrounds the reinforcing component on at least 99.5% of the surface area of the reinforcing component.

5. The joint prosthesis ofclaim 1, wherein the reinforcing component comprises:

a first portion defining a first centerline thereof; and

a second portion defining a second centerline thereof, said first centerline and said second centerline being non-coincidental.

6. The joint prosthesis ofclaim 5, wherein the second centerline is parallel and spaced from the first centerline.

7. The joint prosthesis ofclaim 1, wherein said polymeric material comprises crosslinked ultra high molecular weight polyethylene

8. The joint prosthesis ofclaim 1, wherein the reinforcing component defines a holding feature thereon for holding the reinforcing component when placing the polymeric material onto the reinforcing component.

9. The joint prosthesis ofclaim 5, wherein the reinforcing component defines an orientation feature thereon for orienting the reinforcing component with respect to at least one of the first centerline and the second centerline when placing the polymeric material onto the reinforcing component.

10. The joint prosthesis ofclaim 5, wherein the reinforcing component defines a first recess on the first portion and a second recess on the second portion, the first recess and the second recess adaptable for holding the reinforcing component when placing the polymeric material onto the reinforcing component.

11. The joint prosthesis ofclaim 10, wherein the first recess and the second recess are oriented substantially concentric with at least one of the first centerline and the second centerline.

12. The joint prosthesis ofclaim 5, wherein said reinforcing component defines a first recess and a second recess on the first portion, the first recess and the second recess adaptable for holding the reinforcing component when placing the polymeric material onto the reinforcing component.

13. The joint prosthesis ofclaim 12, wherein the first recess and the second recess are oriented substantially perpendicular to the first centerline and the second centerline.

14. A knee prosthesis, comprising:

a femoral component for attachment to a femur;

a tibial tray for attachment to a tibia;

a bearing component positionable between said femoral component and said tibial tray for cooperation with said femoral component and said tibial tray, said bearing component including a reinforcing component having a first end and a second end thereof and a polymeric material, the polymeric material surrounding at least 99% of the surface area of the reinforcing component and molded thereto, so that the material may be sterilized by a predominately surface sterilizing technology, said bearing component defining a first peripheral region thereof and a second peripheral region thereof, the first peripheral region being adjacent the first end of the reinforcing component and the second peripheral region being adjacent the second end of the reinforcing component, the first peripheral region being cooperable with the femoral component and the second peripheral region being cooperable with the tibial tray.

15. The knee prosthesis ofclaim 14, wherein the predominately surface sterilizing technology comprises a gas plasma spray process.

16. The knee prosthesis ofclaim 14, wherein said polymeric material extends normally from the surface of the reinforcing component a distance of at least 5 millimeters.

17. The knee prosthesis ofclaim 14, wherein said polymeric material surrounds the reinforcing component on at least 99.5% of the surface area of the reinforcing component.

18. The knee prosthesis ofclaim 14, wherein the reinforcing component comprises:

a first portion defining a first centerline thereof; and

a second portion defining a second centerline thereof, the first centerline and the second centerline being non-coincidental.

19. The knee prosthesis ofclaim 18, wherein the second centerline is parallel and spaced from the first centerline.

20. The knee prosthesis ofclaim 14, wherein the polymeric material comprises crosslinked ultra high molecular weight polyethylene.

21. The knee prosthesis ofclaim 14, wherein the reinforcing component defines a holding feature thereon for holding the reinforcing component when placing the polymeric material onto the reinforcing component.

22. The knee prosthesis ofclaim 18, wherein the reinforcing component defines an orientation feature thereon for orienting the reinforcing component with respect to at least one of the first centerline and the second centerline when placing the polymeric material onto the reinforcing component.

23. The knee prosthesis ofclaim 18, wherein the reinforcing component defines a first recess on the first portion and a second recess on the second portion, the first recess and the second recess adaptable for holding the reinforcing component when placing the polymeric material onto the reinforcing component.

24. A bearing component for use in knee joint arthroplasty, said bearing component being positionable between a femoral component and a tibial tray for cooperation with the femoral component and the tibial tray, said bearing component comprising:

a reinforcing component having a first end and a second end thereof; and

a polymeric material, the polymeric material surrounding at least 99% of the surface area of the reinforcing component, so that the material may be sterilized by a predominately surface sterilizing technology, said bearing component defining a first peripheral region thereof and a second peripheral region thereof, the first peripheral region being adjacent the first end of the reinforcing component and the second peripheral region being adjacent the second end of the reinforcing component, the first peripheral region being cooperable with the femoral component and the second peripheral region being cooperable with the tibial tray.

25. The bearing component ofclaim 24, wherein the predominately surface sterilizing technology comprises a gas plasma spray process.

26. The bearing component ofclaim 24, wherein said polymeric material surrounds said reinforcing component on at least 99.5% of the surface area of said reinforcing component.

27. The bearing component ofclaim 24, wherein said reinforcing component comprises:

a first portion defining a first centerline thereof; and

a second portion defining a second centerline thereof, the first centerline and the second centerline being non-coincidental.

28. The bearing component ofclaim 24, wherein said polymeric material comprises crosslinked ultra high molecular weight polyethylene.

29. The bearing component ofclaim 24, wherein said reinforcing component defines a holding feature thereon for holding said reinforcing component when placing said polymeric material onto said reinforcing component.

30. The bearing component ofclaim 27, wherein said reinforcing component defines a orientation feature thereon for orienting said reinforcing component with respect to at least one of first centerline and second centerline when placing said polymeric material onto said reinforcing component.

31. The bearing component ofclaim 27, wherein said reinforcing component defines a first recess on the first portion and a second recess on the second portion, the first recess and the second recess adaptable for holding said reinforcing component when placing said polymeric material onto said reinforcing component.

32. A method of manufacturing a polymeric bearing component for use in joint arthroplasty and for cooperation with a first joint component and a second joint component, comprising the steps of:

providing a reinforcing support having a first end and a second end thereof;

providing a molding die adapted for manufacturing the bearing component for use in joint arthroplasty and having a first mold portion and a second mold portion thereof, the first mold portion adapted to provide a first surface and cooperation with the first joint component and the second mold portion adapted to provide a second surface for cooperation with the second joint component;

providing a positioning member for cooperation with the reinforcing support and molding die;

positioning the support in a desired position within the molding die, with one of the first end and at the second end located in the first mold portion;

maintaining the position of the support with the positioning member in intimate contact with the support;

adding moldable polymeric material into the molding die;

substantially surrounding the support with the moldable material;

heating and pressurizing the mold;

permitting the moldable material to cool to form the bearing component and during the cooling and forming of the moldable material removing the positioning member from the support while maintaining a lower amount of one of heat and pressure on the mold and allowing the polymeric material to replace the space occupied by the positioning member; and

removing the component from the molding die.

Images