US20050283253A1 - Knee arthroplasty prosthesis and method - Google Patents

Abstract

A knee arthroplasty prosthesis includes a femoral component having multiple pieces with engagement means provided for engaging various pieces of the femoral component to one another following their insertion in the incised area of the femur. A tibial component includes multiple pieces designed for assembly following positioning in the incision. The tibial component includes a Morse taper cavity on one piece of the tibial component and a Morse taper extension on another member of the component for receipt therein.

Description

CROSS REFERENCE TO RELATED APPLICATION
• This application is based upon and claims priority under U.S. Provisional Application Ser. No. 60/358,174 filed Feb. 20, 2002.
BACKGROUND OF THE INVENTION
• In performing knee arthroplasty with conventional knee prostheses, it has been necessary to form large incisions in order to accommodate the preparation of the femur to receive the prosthesis and to accommodate the reception of a fairly large prosthesis into the incised femur for implantation on the prepared distal end of the femur. As is appreciated by those skilled in the art, it is desirable to minimize the size of any incision as the smaller the incision, the more rapidly the patient may recover. Prior art prostheses formed with a single piece metal component having both left and right condylar portions integral with the patellar flange area require large incisions in order to accommodate implantation in the prepared femur. In contrast, under the present invention, through the use of multiple pieces for the femoral component, it is possible to greatly reduce the size of any such incision, thereby reducing the amount of damage to soft tissue from any such arthroplasty and speeding the time of recovery. Similarly, it is desirable to minimize the size of any incision in the tibia during any implantation of the tibial component.
SUMMARY OF THE INVENTION
• The present invention is directed to a prosthesis for use in knee arthroplasty including total knee arthroplasty which is minimally invasive to the patient and to a method for performing surgery using such prosthesis including the femoral and tibial components thereof. Under the invention, the femoral component and, preferably, the tibial component are manufactured in at least two and possibly three or more pieces. However, it is possible that the tibial component could be a single piece, monoblock construction as well as modular multipiece construction. In both the single piece and multipiece construction, there is also provided a plastic articular surface insert piece. The pieces are designed to be assembled together following insertion into the knee. This allows total knee arthroplasty to be performed through very small incisions, as small as three inches, in each of the distal end of the femur and proximal end of the tibia. Following insertion, the pieces of the femoral component implanted at the distal end of the femur are joined together with a locking mechanism to form the modular femoral component and the pieces of the tibial component implanted at the proximal end of the tibia are assembled to form the modular tibial component.
• Femoral Component
• The femoral component may have three component pieces for a cruciate retaining design and two component pieces for a cruciate sacrificing design. It may be manufactured as two or three separate pieces or manufactured as a single unitary member which is subsequently cut or otherwise divided into two or three separate pieces. The pieces are provided with a locking joint for retaining the pieces together following insertion in distal end of the femur. The locking joint for the pieces is placed at the area of low patella/femoral contact, a low stress area of the femur. This corresponds to the anterior chamfer cut of a routine total knee arthroplasty and the area can be easily reinforced to accommodate the additional thickness of the locking joint. Various locking mechanisms may be employed for joining the pieces together including screws or a transverse locking pin which may be inserted from the medial side and/or lateral side. The locking mechanisms of whatever type lock the component pieces together into a solid assembled prosthesis. The prosthesis will be additionally reinforced by the underlying bone and/or cement fixation and will produce a durable construction. The patellar flange and the area of any joint between assembled components which may be contacted by the patella should be smoothed and, possibly, recessed to prevent premature wear of the patellar member as it tracks over the joint in the femoral component.
• Tibial Component
• The tibial component preferably has two pieces, namely, a tibial base and a tibial stem. It is also inserted in pieces from the side. It may also be a monoblock, one-piece tibial component with pegged or short stem fixation. The tibial base may have of a flat baseplate with anterior and posterior dovetails and may have a tapered transverse keel. The other piece of the tibial component is a modular stem which is inserted from the top after the baseplate is inserted. This design allows the components to be inserted through the minimal incision and still have long term stability. The stem is preferably fixed with a reverse Morse taper so that it can be driven through the baseplate like a spike.
• Patellar Component
• A standard conforming dome configuration patellar component is utilized, with the main difference being its method of insertion. It may be inserted without everting the patella. This is accomplished with the use of special instrumentation.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective view of one embodiment of femoral component showing the medial condyle as a separate piece from the remainder of the femoral component.
• FIG. 2 is a perspective view of a second embodiment of femoral component showing the lateral condyle as a separate piece from the remainder of the femoral component.
• FIG. 2A is a sectional view showing a patellar member engaged to the articulating surface of the patellar femoral flange piece.
• FIG. 3 is a perspective view of another embodiment of femoral component showing both the medial condyle and the lateral condyle as separate pieces from the patellar femoral flange piece of the femoral component.
• FIG. 4 is a perspective view showing the patellar femoral flange piece ofFIG. 3 taken from a different angle.
• FIG. 5 is a perspective view of an embodiment of femoral component showing the patellar femoral flange piece as a separate piece from the remainder of the femoral component.
• FIG. 6 is a front view of the embodiment of the femoral component ofFIG. 5.
• FIG. 7 is a side view of the embodiment of the femoral component ofFIG. 5.
• FIG. 8 is a sectional view taken through line8-8 ofFIG. 6.
• FIG. 9 is a sectional view taken through line9-9 ofFIG. 6.
• FIGS. 10 and 11 are perspective views of other embodiments of the femoral component showing the patellar femoral flange piece as a separate piece from the remainder of the femoral component.
• FIG. 11A is a view similar toFIG. 9 for the embodiment ofFIG. 11.
• FIG. 11B is a sectional view throughline11B-11B ofFIG. 11A.
• FIG. 12 is a perspective view of another embodiment of femoral component showing the patellar femoral flange piece as a separate piece from the remainder of the femoral component and showing one form of design for connecting the patellar femoral flange piece to the remainder of the femoral component.
• FIG. 13 is an enlarged view of the circled portion ofFIG. 12.
• FIG. 14 is a perspective view of an embodiment of femoral component showing the lateral condyle as a separate piece from the remainder of the femoral component.
• FIG. 15 is an enlarged view of the circled portion ofFIG. 14.
• FIG. 16 is a perspective view of another embodiment of femoral component showing the patellar femoral flange piece as a separate piece from the remainder of the femoral component.
• FIG. 17 is an enlarged view of the circled portion ofFIG. 16.
• FIG. 18 is a perspective view of the tibial component showing the stem portion thereof as a separate piece from the base.
• FIG. 18A is a view similar toFIG. 18 with the added feature of a stem extension as part of the tibial component.
• FIG. 19 is a sectional view of another embodiment of tibial component showing the stem portion thereof as a separate piece from the base.
• FIG. 20 is a perspective view of another embodiment of tibial component showing the stem portion thereof as a separate piece from the base.
• FIG. 21 is a side view of the tibial component ofFIG. 20 showing its implantation in the proximal end of a prepared tibia.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
• Referring toFIG. 1, there is shown one embodiment of femoral component generally designated by the numeral10. The femoral component includes afirst piece12 having apatellar flange portion14 and an integral, unitarylateral condyle portion16 extending therefrom. A prior art femoral component would also have an integral, unitary medial condyle on the opposite side from thelateral condyle portion16. Under the present invention, there is provided, as a separate piece, amedial condyle piece18 intended to be assembled to thefirst piece12 following implantation of both thefirst piece12 and themedial condyle piece18 in the patient. The assembly mechanism or locking joint for securing themedial condyle piece18 to thefirst piece12 will be hereinafter described.
• As shown inFIG. 1, themedial condyle piece18 is provided with arecess15 for receiving bone cement and a pair of fixation pins17. Thefirst piece12 may also be provided with one or more recesses and fixation pins. If it is desired to have a prosthesis for implantation without bone cement, the recesses such as therecess15 can be replaced by one of several types of porous surfaces well known in the art for bone in-growth.
• Referring toFIG. 2, there is shown a second embodiment of afemoral component20 having afirst piece22 with a patellarfemoral flange portion24 and an integral, unitarymedial condyle portion26. The second component of this embodiment is alateral condyle piece28 which may be joined with thefirst piece22 following implantation of both thefirst piece22 and thelateral condyle piece28 in the femur of the patient.
• FIG. 2A shows a sectional view of patellar member P in contact with the articulating surface of the patellarfemoral flange portion24.
• FIG. 3 shows yet another embodiment of a three-piecefemoral component30. Under this embodiment, there is provided a patellarfemoral flange piece32, asecond piece34 which is a medial condyle piece and athird piece36 which is a lateral condyle piece assuming, of course, implantation in the right knee of a patient. If thefemoral component30 were implanted in the left knee of a patient, thesecond piece34 would be the lateral condyle piece and thethird piece36 would be the medial condyle piece. Each of thesecond piece34 and thethird piece36 are joined to the patellarfemoral flange piece32 following insertion in the patient's femur by use of a locking joint to be hereinafter described.
• All three of the pieces of the femoral component may be provided withfixation pins37 and recesses35 if intended for use with bone cement or a porous surface if intended for non-cemented implantation.
• FIG. 4 is a perspective view of the patellar femoral flange piece ofFIG. 3 taken from a different angle.
• Thefemoral components10,20 and30 ofFIGS. 1 through 3 could be used for implantation in either knee. The foregoing description for each of thefemoral components10,20 and30 is based on the assumption of implantation in the right knee. If they were used for implantation in the left knee, the pieces identified by thenumerals18 and34 would be lateral condyle pieces, the pieces identified by thenumerals28 and36 would be medial condyle pieces, the portion identified by the numeral16 would be a medial condyle portion and the portion identified by the numeral26 would be a lateral condyle portion.
• Referring toFIGS. 5, 6,7,8 and9, there is shown an embodiment offemoral component40 having two pieces, namely, a patellarfemoral flange piece41 and acondylar piece42. The patellarfemoral flange piece41 has apatellar engaging surface43 shaped to allow anatomical tracking of a natural or prosthetic patella P. As shown inFIG. 5, the patellarfemoral flange piece41 has a superiorbone engaging surface46 and apatellar engaging surface43 defining a portion of an inferior articulating surface. The patellarfemoral flange piece41 extends from aninferior end45 to aleading end48 which is contoured to engage thecondylar piece42. Thecondylar piece42 includes afirst condylar portion50 and asecond condylar portion52 and extends from anengagement end54 contoured to receive theleading end48 of thepatellar flange41 to aposterior end55. As will be appreciated by those skilled in the art, thefemoral component40 could be used for implantation in either a right knee or left knee and the first and second condylar portions will be either lateral or medial facing depending upon the knee in which thefemoral component40 is implanted.
• Thecondylar piece42 has a superior bone engaging surface with a series ofbone engaging flats60,61,62 and63 disposed at varying angles consistent with cuts made in preparing the distal end of the femur to receive thecondylar piece42. If desired, the superiorbone engaging surface46 of thepatellar flange piece41 and the superiorbone engaging surfaces60,61,62 and63 of thecondylar piece42 may be formed with recesses for receiving bone cement or porous surfaces for bone ingrowth and may also be provided with fixation pins.
• Thecondylar piece42 in the embodiment ofFIGS. 5-9 is formed as a single unitary piece for implantation. As such, thefirst condylar portion50 and thesecond condylar portion52 are joined together with aposterior cam56 which may be formed integral with or welded or otherwise joined to the first and secondcondylar portions50,52. Theengagement end54 of thecondylar piece42 also has the first and secondcondylar portions50,52 joined together by a laterally extendingcross member57. As will be appreciated by those skilled in the art, the use of theposterior cam56 will result in sacrificing of the posterior cruciate ligament. As will be appreciated, in those cases where it may be necessary to sacrifice the posterior cruciate ligament for other reasons, the feature of having both aposterior cam56 and across member57 for joining the first and secondcondylar pieces50,52 will provide great rigidity to thecondylar piece42.
• As can be seen inFIGS. 5, 7 and9, thecross member57 has a superiorbone engaging surface57A and amedial surface57B approximately midway between the superiorbone engaging surface57A and the articulatingsurfaces51 and53 of thefirst condylar portion50 andsecond condylar portion52, respectively. On the posterior side of thecross member57 is aposterior wall surface57C extending between the superiorbone engaging surface57A and thesurface57B. Opposite theposterior surface57C is afourth surface57D which will engage a corresponding surface to be described of the patellarfemoral flange piece41.
• The engagement ends54 for each of the first and secondcondylar portions50,52 each follows a curved path defined bysidewall engagement surface54A as shown inFIGS. 5 and 6. Each of the curvedengagement wall surfaces54A extends to the general area defined by theposterior wall surface57C ofcross member57. (SeeFIG. 5). The positioning of the joint defined by thesurfaces54A of thecondylar piece42 and the mating surfaces of the patellarfemoral flange piece41 is important and should be in the vicinity of the normal femoral tide mark which is a low stress area of contact by sliding engagement of the patella. By providing the joint in this area, the prosthesis has great ability to function as desired with no separation of the patellarfemoral flange piece41 from thecondylar piece42 following implantation. The normal femoral tide mark corresponds to the area of the inferior chamfer cut of a routine total knee arthroplasty.
• The patellar femoral flangepiece leading end48 has a pair of curved engagement surfaces64 following a contour for mating engagement with therespective surfaces54A of thecondylar piece42. Centrally positioned between the curved engagement surfaces64 is acentral wall surface65 which, when the patellarfemoral flange piece41 is engaged to thecondylar piece42, lies in substantially the same plane as thesurface57C ofcross member57. (SeeFIG. 9). Thecentral wall surface65 extends superiorly from thepatellar engaging surface43 to aledge66 intended to rest upon thesurface57B ofcross member57. Theledge66 extends away from thecentral wall surface65 to acentral engagement surface67 which is intended to engage thesurface57D ofcross member57. Abone engaging surface68 extends from thecentral engagement surface67 toward theanterior end45.
• As shown inFIGS. 6, 7 and9, thecondylar piece42 may be secured to the patellarfemoral flange piece41 by means ofscrews68 extending throughapertures69 extending throughengagement end area54 of the respective first and secondcondylar portions50 and52, through theengagement end surfaces54A and into aligned threadedapertures71 extending inwardly from the curved engagement surfaces64 of the patellarfemoral flange piece41.
• Referring toFIG. 8, there is shown the articulating surface defined by thepatellar engaging surface43 of the patellarfemoral flange piece41 and the articulating surface59 of thecondylar piece42 in the area of the joint defined by themating surface54A of thecondylar piece42 andsurface64 of the patellarfemoral flange piece41. As can be seen inFIG. 8, therespective surfaces43 and59 are recessed slightly at such joint to provide aslight dip73 so that any movement of the patellar member P over such joint will leave a slight gap between the surface of the patellar member P and thesurfaces43 and59 at thedip73.
• The presence of the gap and thedip73 has a two-fold advantage. It reduces the amount of stress in that area of the joint defined by the mating surfaces54A and64 at thesurfaces43 and59. Additionally, if there is a slight mismating of the patellarfemoral flange piece41 relative to thecondylar piece42 such that one of thesurfaces43 or59 were slightly high or lower than intended for precise fixation, the presence of thedip73 will serve to prevent the patellar member P from contacting and being subjected to premature wear by a sharp corner of the higher piece.
• Referring toFIG. 10, there is shown a further embodiment similar to that ofFIGS. 5 through 9 but one in which there is provided acondylar piece42A having thefirst condylar portion50A is joined to thesecond condylar portion52A only by aposterior cam56A. Under this embodiment, the patellarfemoral flange piece41A has acentral wall surface65A centrally positioned between curved engagement surfaces64A. Thecentral wall surface65A extends throughout the thickness of the patellarfemoral flange piece41A. Therefore, there is no ledge similar to theledge66 shown inFIG. 5. All other features of the embodiment ofFIG. 10 are similar to corresponding features of the embodiment ofFIGS. 5, 6,7,8 and9.
• Referring toFIGS. 11, 11A and11B, there is shown a further embodiment offemoral component40B similar to that ofFIGS. 5 through 9 but one in which there is provided acondylar piece42B having thefirst condylar portion50B joined to thesecond condylar portion52B only by across member57B and a modified connector means for fastening thecondylar piece42B to the patellarfemoral flange piece41B.
• Thecross member57B is provided with anextension130 extending superiorly (i.e., downwardly as viewed inFIGS. 11 and 11A) from thecross member57B. Both thecross member57B and theextension130 are provided with acommon dovetail slot132. Theextension130 is an integral unitary part of thecross member57B and, in cross section, has a generally semicircular cross sectional configuration with the side facing the patellarfemoral flange piece41B having a pair of flat faces on opposite sides of thedovetail slot132.
• The patellarfemoral flange piece41B, has a configuration similar to that of the patellarfemoral flange piece41 as shown inFIG. 5, including acentral wall surface65B extending from apatellar engaging surface43B, aledge66B and acentral engagement surface67B. Abone engaging surface68B extends from thecentral engagement surface67B toward theanterior end45B. Extending superiorly from thebone engaging surface68B is anextension134 having adovetail136 sized to be snugly received in thedovetail slot132 of theextension130 with conforming mating surfaces. Thedovetail136 anddovetail slot132 could have other crossectional configurations from that shown inFIGS. 11, 11A and11B such as circular or rectangular. As will be appreciated and as can be seen fromFIGS. 11A and 11B, thedovetail136 is an integral unitary part of theextension134; however, it extends outwardly from thesurface67B and upwardly from thesurface68B to join withsurface66B.
• Therespective extensions130 of thecondylar piece42B and134 of the patellarfemoral flange piece41B, when joined together with thedovetail136 positioned in thedovetail slot132 will cooperate to define a substantially cylindrical configuration; however, if desired, a different configuration, such as square, rectangular or rounded, could be utilized.
• Preparatory to implantation of thecondylar member42B and patellarfemoral flange piece41B, an aperture is drilled or otherwise formed in the femur of sufficient size to receive theextensions130 and134.
• Following positioning of thecondylar piece42B in the prepared femur with itsextension130 positioned in the prepared bone cavity, the patellarfemoral flange piece41B is moved therein, thedovetail136 is aligned with thedovetail slot132 and the patellarfemoral flange piece41B is moved toward the prepared femur with thedovetail136 sliding through thedovetail slot132 until thesurface66B of the patellarfemoral flange piece41B contacts the anterior surface ofcross member57B. Desirably, bone cement will be positioned in the prepared aperture of the femur to engage the adjoinedextensions130 and134.
• Referring toFIGS. 12 and 13, there is shown an embodiment of a two-piecefemoral component74 with afirst piece75 of a patellar flange area having apatella engagement surface76 and asecond piece77 having amedial condyle portion78 and alateral condyle portion79 formed as an integral unitary piece. Thesecond piece77 has a series offlats96,97,98,99 for engagement with a prepared distal end of a femur.
• Thefirst piece75 has anabutment wall81 extending from thepatella engagement surface76 and positioned to engage acorresponding abutment wall82 of thesecond piece77. The line of juncture between theabutment wall81 of thefirst piece75 and theabutment wall82 of thesecond piece77 is in the area of low patella/femoral contact which is a low stress area of the femur. Theabutment wall81 extends only partially through the thickness of thefirst piece75. Theabutment wall81 joins with asecond wall83 disposed substantially at right angles thereto (SeeFIG. 13). Thesecond wall83 extends to anend wall84. Extending outwardly from theend wall84 toward the plane defined by theabutment wall81 is aledge85 having anupper surface86 with a tongue or dovetail87 projecting upwardly therefrom. Thetongue87 andupper surface86 extend throughout the breadth of thefirst piece75. Thetongue87 is provided with a pair of reverse taper surfaces88 which flare outwardly from one another in a direction away from theupper surface86.
• Extending outwardly from theabutment wall82 of thesecond piece77 is aninsert ledge90 having an upper surface for mating engagement with thesecond wall83 of thefirst piece75. The lower portion of theinsert ledge90 opposite the upper surface has formed therein adovetail groove92 extending the full breadth of thesecond piece77 and sized to receive thetongue87 of thefirst piece75. As can be seen fromFIG. 13, when thefirst piece75 andsecond piece77 are joined together, there will remain agap93 between theend wall84 of thefirst piece75 and the end of theinsert ledge90 of thesecond piece77. In order to prevent the engagedfirst piece75 andsecond piece77 from moving laterally relative to one another, there is provided a taperedpin94 which may be driven into thegap93 to function as a wedge putting thetongue87 into compression in thedovetail groove92 formed in the lower surface of theinsert ledge90.
• Referring toFIGS. 14 and 15, there is provided another embodiment ofprosthesis100 with afirst piece101 having both apatellar flange area102 and an integral, unitarylateral condyle portion103. Theprosthesis100 also has asecond piece104 which is a medial condyle piece. Thefirst piece101 has afirst abutment wall105 extending generally laterally and asecond abutment wall106 extending generally longitudinally with acurved wall section107 joining thefirst abutment wall105 and thesecond abutment wall106. Protruding outwardly from thesecond abutment wall106 is aprojection110 having sidewalls111 (only one of which is shown) tapering inwardly toward one another as they extend outwardly from thesecond abutment wall106 and endwalls112 tapering inwardly toward one another as they extend outwardly from thesecond abutment wall106. The taperingsidewalls111 and endwalls112 are joined by anouter wall113 substantially parallel with thesecond abutment wall106. Theprojection110 is integral and unitary with the remainder of thefirst piece101 and may be formed by a milling process, for example. A threadedaperture114 extends through theprojection110 from theouter wall113 and, preferably, extends into the adjacent portion of thefirst piece101.
• Thesecond piece104 has afirst abutment wall115 positioned to engage thefirst abutment wall105 of thefirst piece101, asecond abutment wall116 positioned and sized to engage thesecond abutment wall106 of thefirst piece101 and a curved wall117 for engagement with thecurved wall107 of thefirst piece101. Formed in thesecond wall116 is arecess118 contoured to snuggly receive theprojection110 of thefirst piece101. A laterally extendingpassageway108 extends through thesecond piece104 in alignment with the threadedaperture114 of thefirst piece101 when thesecond piece104 is engaged thereto.
• In order to join thesecond piece104 to thefirst piece101 there is provided anelongated screw120 having a threadedsection121 for mating with the threads of the threadedaperture114 of thefirst piece101. Thescrew120 has acylindrical section122 of larger diameter than the threadedsection121 and sized to be snugly received in thepassageway108 of the second piece. Thescrew120 has anenlarged head123 sized to fit in a countersunk area of thepassageway108 at the outer edge of thesecond piece104.
• Referring toFIGS. 16 and 17, there is shown a two-piecefemoral component140 including afirst piece141 having both alateral condyle142 and amedial condyle143 formed as part of an integral, unitary piece. Thesecond piece144 defines a patellar flange area of thefemoral component140. Thesecond piece144 has a contouredabutment wall145 including a firstflat surface145A extending inwardly from the lateral side, a secondflat surface145B extending inwardly from the medial side of thesecond piece144 and a recess defined by first andsecond side walls145C and abottom wall145D. The sidewalls145C taper inwardly toward one another as they extend from their respectiveflat surfaces145A and145B to the bottom145D. Preferably, thebottom wall145D is curved; however, it could be flat.
• Thefirst piece141 is provided with anabutment wall146 having a contour to be snuggly engaged to theabutment wall145 of thesecond piece144. As such, theabutment wall146 includes atongue147 contoured to fit snuggly in the groove defined by sidewalls145C andbottom wall145D of thesecond piece144. Thetongue147 is defined by sidewalls146C,146C and anend wall146D contoured to snuggly engaged thewall145D forming the bottom of the groove of thesecond piece144. Thewalls146C,146C taper inwardly toward one another as they extend toward thewall146D and snuggly engage the taperedsidewalls145C of thesecond piece144.
• Thesecond piece144 has formed therein afirst passageway148A which extends inwardly from the lateral edge and is substantially parallel to the firstflat surface145A and asecond passageway148B which extends inwardly from the medial edge and is substantially parallel to the secondflat surface145B. Apassageway149 is formed in thetongue147 in a position to be aligned with thepassageways148A and148B when thefirst piece141 is engaged to thesecond piece144, with thetongue147 fitting in the groove. Apin150 may be inserted through thepassageway148B, thepassageway149 and thepassageway148A to secure thefirst piece141 to thesecond piece144. Thepin150 could be cylindrical and press fit into therespective passageways148A,148B and149 assuming the passageways were cylindrical or could be tapered assuming such passageways had the appropriate taper. Additionally, one of the passageways,passageway148A, for example, could be threaded, in which case thepin150 would have a threaded end for engagement therewith.
• In each of the embodiments, the respective lines of juncture between abutting walls of the assembled pieces have been selected to be located generally in the area of the normal femoral tidemark which is a low stress area.
• Referring now toFIG. 18, there is shown a tibial component generally designated by the numeral161. Thetibial component161 includes atibial base162 and atibial stem163. Thetibial base162 has aninferior surface164 intended to engage the prepared proximal end of the tibia of the patient and a superior surface (not shown) to which may be affixed a plastic insert contoured to be engaged by the condylar portions of a femoral component. The plastic insert may have one of a number of well known mechanisms for being attached to thetibial base162 such as a dove tail locking mechanism, for example. The plastic insert may be inserted either laterally or proximally depending on the specific design of the tibial base and the condition of the patient as determined by the surgeon. Extending distally from theinferior surface164 is abase extension165 having a generally cylindrical shape but with a pair of fixation wings orfins166 extending outwardly from the cylindrical portion of thebase extension165. Aplatform167 is raised from theinferior surface164 and follows a contour encircling thebase extension165 including thewings166. Thewings166 function as fixation fins for maintaining thetibial base162 in a fixed rotational position when implanted on the prepared proximal end of the tibia. Thetibial base162 is provided with anotch168 to accommodate the posterior cruciate ligament and a plurality ofapertures169 for receiving screws for engagement to an augmentation block, if one is needed, or for securing thetibial base162 to the proximal end of a prepared tibia.
• Thetibial base162 has acentral passageway170 extending from thesuperior surface164 and through the cylindrical portion of thebase extension165. That portion of thecentral passageway170 in thebase extension165 has wall surface which flares outwardly frusto conically and defines aMorse taper cavity295 as it approaches the end of thebase extension165. A recess defining anotch240 is formed in the end of thebase extension165. That portion of the passageway adjacent the superior surface has a diameter sized to receive ascrew158 and acountersunk area297 to receive the enlarged head ofsuch screw158.
• Thetibial stem163 is provided with a pair of wings orfixation fins171 which, when thetibial stem163 is engaged to theextension165, will be aligned with and forming extensions of the respective wings orfins166 of thetibial base162. Thetibial stem163 is provided with aMorse taper extension298 sized to be snugly received in theMorse taper cavity295 of thetibial base162. Ashoulder262 extends outwardly from theMorse taper extension298. A raised tab242 extends proximally from theshoulder202 and is sized to fit snugly in thenotch210 and, when so positioned, assures alignment of thefixation fins171 of thetibial stem163 with thefins166 of thetibial base162.
• A threadedpassageway172 is formed in theMorse taper extension298 and is aligned with thecentral passageway170 when thetibial stem163 is engaged to theextension165. Thetibial stem163 is supported on thetibial base162 by thescrew158 extending through thecentral passageway170 of thetibial base162 and engaged to the threadedpassageway172. Aplug244 is engaged in the distal end of thetibial stem163 to prevent blood or other contaminates from entering the threadedpassageway172. Theplug244 may be secured to thetibial stem163 by means of a threaded extension engaging the threadedpassageway172.
• FIG. 18A shows an embodiment similar toFIG. 18 but in which there is provided astem extension250 but not a plug such as theplug244 ofFIG. 18. Thestem extension250 is provided with aMorse taper252 at itsproximal end253. A threadedrecess254 extends distally from the proximal end and has a size smaller than the threadedpassageway172. A threadedscrew258 sized to engage the threadedrecess254 secures thestem extension250 and thetibial stem163 to thetibial base162. The threadedscrew258 is small enough to pass through the threadedpassageway172 without engaging its threads.
• The distal end of thetibial stem163 has acavity260 tapering outwardly in a distal direction and defining a Morse taper sized to snuggly receive theMorse taper252 of thestem extension250. Twogrooves270 are formed in thetibial stem163, on opposite sides, distally spaced from theshoulder262. The purpose of thegrooves270 is to permit engagement and support for the tibial stem during implantation as will be discussed hereinafter.
• Referring toFIG. 19, there is a shown in section a modified embodiment oftibial component200. Under this embodiment there is provided atibial base202, atibial stem204 and aplastic insert206 for engagement with thetibial base202. The tibial base, as shown inFIG. 19, has a raisedwall208 and a flatsuperior surface210. Thetibial base202 has aninferior surface212 intended to engage the prepared proximal end of the tibia of the patient. A centrally positionedshort extension213 extends from theinferior surface212.
• Extending through thetibial base202 including theextension213 is apassageway214. That portion of thepassageway214 adjacent theinferior surface210 is enlarged from the remainder of the passageway and is provided with inwardly facingthreads215 in the area adjacent theinferior surface210. That portion of thepassageway214 extending away from thethreads215 is tapered to define aMorse taper cavity216 throughout the remainder of the thickness of thetibial base202 including thestem213.
• Thetibial stem204 is provided with an enlarged threadedflange220 sized to engage thethreads215 of thetibial base202. Extending from theflange220 is aMorse taper extension222 sized and contoured to be snuggly received in theMorse taper cavity216. Extending inwardly from theinferior surface210 is a cavity defined by a series offlats224 which cooperate to define a hexagon or other conveniently shaped cavity for receipt of a tool for engagement therein for threading the threadedflange220 into thethreads215.
• Extending from the cavity defined by theflats224 is a threadedaperture225. Extending distally from theMorse taper extension222 is a reduced sizecylindrical extension227.
• Theplastic insert206 has molded therein ametal insert230 having anenlarged flange232 to ensure its firm engagement to theinsert206. Theinsert206 is provided with apassageway234 sized to receive ascrew236 including itsenlarged head238. Themetal insert230 is provided with apassageway240 sized to receive the threaded portion of thescrew236 but smaller than theenlarged head238. Following engagement of thetibial stem204 to thetibial base202, theplastic insert206 is positioned on theinferior surface210 within the upwardly extendingwall208. Thescrew236 is then engaged to the threadedaperture225 to secure theplastic insert206 thereto.
• In the surgical procedure for implanting thetibial component200, the proximal end of the tibia is prepared by cutting a flat surface to receive theinferior surface212 of thetibial base202 and a cavity is drilled in the intramedullary canal of the tibia to receive thestem204. Thetibial base202 is positioned on the prepared flat surface with theextension213 positioned in the cavity. Thetibial stem204 is then positioned in thepassageway214 with thecylindrical extension227 passing through theMorse taper cavity216 and into the cavity of the intramedullary canal. Using a tool engaged to theflats224, the stem is threadedly engaged to thethreads215 and the base202 to cause theMorse taper extension222 to firmly engage theMorse taper cavity216. As may be seen inFIG. 19, thetibial stem204 is so contoured relative to thetibial base202, that agap229 will remain between the distal side of theflange220 and the surface of thetibial base202 extending radially outwardly from theMorse taper cavity216. This ensures that theMorse taper extension222 will firmly engage theMorse taper cavity216 upon threaded engagement of the threadedflange220 to thethreads215.
• Referring now toFIGS. 20 and 21, there is shown another embodiment oftibial component180 along with atool195 for use in implanting such tibial component in the proximal end of a prepared tibia T. Thetibial component180 includes atibial base181, atibial stem182 and aplastic insert179 engaged to thetibial base181. Thetibial base181 has aninferior surface183 intended to engage the prepared proximal end of the tibia T and asuperior surface184 to which may be affixed aplastic insert179 contoured to be engaged by a femoral component. Thetibial base181 has raisedareas185 along the anterior and posterior edges. Each of the raised areas is provided with an undercutwall surface186 defining grooves for receiving and retaining theplastic insert179.
• Extending distally from theinferior surface183 is anextension187. Thetibial base181 has acentral passageway188 extending from thesuperior surface184 and through theextension187. Theextension187 and thepassageway188 may be disposed at an angle of up to 100 relative to a line perpendicular to thesuperior surface184 in order to accommodate the anatomy of the patient.
• Thetibial stem182 is provided with arecess190 sized and positioned to become an extension of thepassageway188 of thetibial base181. Therecess190 may be threaded for engagement by a threadedscrew196 extending through theplastic insert179 and its articular surface and through thepassageway188 to join thetibial stem182 to thetibial base181. As shown inFIG. 21, thedistal end188A of thepassageway188 may be tapered to define a Morse taper cavity. Thetibial stem182 is also provided, at its proximal end, with aMorse taper extension197 sized to snugly engage the Morse taper cavity at thedistal end188A of thepassageway188. Thetibial stem182 is also provided with a plurality of outwardly facinggrooves189 to assist in fixation.
• In preparing the proximal end of the tibia T to receive thetibial component180, the proximal end T1 of the tibia is cut to form substantially a flat surface. A cavity T2 is formed to receive thetibial stem182. Since the cavity T2 may be oversized, thetibial stem182 is provided with anannular groove198 sized to receive thetines195A of thetool195. As can be seen inFIG. 21, with thetines195A engaged in thegroove198, thetool195 can support thetibial stem182 at the proper location relative to the prepared proximal end T1 of the tibia T until such time as thescrew196 is engaged in the threadedrecess190 to support such tibial stem182 on thetibial base181.
• In implanting thetibial stem163 of the embodiment ofFIGS. 18 and 18A, a tool similar to thetool195 may be used to engage thegrooves270 to support thestem163 until it is engaged by thescrew158 or258.
• In each of the embodiments ofFIGS. 18, 18A,19,20 and21, it is preferred that the surface of the tibial base which is to be contacted by a plastic insert be polished to a high degree, on the order of four (4) rms or less, to prevent premature wear on the surface of the plastic insert engaged to the tibial base.
• Description of Surgical Procedure
• A medial parapatellar incision is made from the superior pole of the patella to the tibial tuberosity. Medial parapatellar arthrotomy is made from the inferior edge of the vastus medial is to the tibial tuberosity. A subvastus or mid vastus arthrotomy may be utilized, based upon patient anatomy or surgeon experience.
• The knee is place in extension and the patella excised without eversion, using a patellar clamp inserted into the prepatellar bursa, to prevent damage to the anterior skin.
• An extramedullary tibial alignment guide is placed along the medial or lateral half of the tibia and secured with fixation pins. An extrameduallary alignment guide of the type disclosed in application Ser. No. 09/973,584 filed Oct. 9, 2001, assigned to the assignee of the present invention and incorporated herein by reference, is fixed to the femur after performing the extramedullary alignment procedure, and the distal femoral cut is made at the appropriate depth and angle of the implant, nominally 6° valgus and 10-12 mm depth of cut. As an alternative, an intramedullar alignment guide system could be used. This cut is taken all the way across both distal femoral condyles, rather than being unicondylar in nature. This cut is made at 90° to the femoral shaft.
• The tibial component is implanted first. The fixation surface is coated with cement, and the modular tibial stem is driven through the reverse Morse taper to lock the tibial stem to the bone.
• The anterior flange component is then implanted, followed by the lateral then medial condyles. Once all pieces are loosely assembled inside the knee and proper alignment is assured, the locking pin is inserted from the side and rigidly fixes the components together. Final impaction is then accomplished.
• Lastly, the patella is cemented in place.
• After all cement has hardened and excess is removed, the final poly slides in from the side, and is secured with an AP locking clip or screw, which also helps lock the modular stem in place.
• Routine closure is performed, and rapid rehab program initiated.
• The above detailed description of the present invention is given for explanatory purposes. It will be apparent to those skilled in the art that numerous changes and modifications can be made without departing from the scope of the invention.

Claims (5)

1-51. (canceled)

52. A method of performing knee arthroplasty comprising the steps of

(a) providing a multi-piece femoral component, said femoral component including (i) a first piece extending from an anterior end to an engagement surface and having a patellar femoral flange portion including an articulating surface and an opposed superior bone engaging surface, (ii) a second piece defining at least one condylar portion extending from a posterior end to an abutment surface and having an inferior surface and an opposed superior bone engaging surface, and (iii) means for securing said first piece and said second piece together;

(b) preparing the distal end of a femur to receive said first piece and said second piece;

(c) positioning one of said first piece or said second piece on said prepared femur distal end;

(d) thereafter positioning the other of said first piece or said second piece on said prepared femur distal end with said engagement surface and said abutment surface in contact with one another and cooperating to define a joint; and

(e) securing said first piece and said second piece together.

53. The method ofclaim 52 wherein step (e) is performed simultaneously with step (d).

54. The method ofclaim 52 wherein step (e) is performed following step (d).

55-62. (canceled)

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