CA2471060C - Modular knee prosthesis - Google Patents

Abstract

A modular prosthetic knee system used to replace the natural knee. The system includes a femoral knee prosthesis and a tibial knee prosthesis. Both prostheses are formed of modular components that are connectable in-vivo to form the prosthetic knee system. The femoral knee prosthesis includes two separate components, a lateral condyle and medial condyle; and the tibial knee prosthesis includes a multiple separate components, a medial baseplate, a lateral baseplate, a medial insert, and a lateral insert. The medial and lateral baseplate are connectable to form a complete baseplate with the medial and lateral inserts connectable to the complete baseplate.

Description

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Monu~,~ ~E rROSs~s CRUSS RER:Et~ENCE TU RELATED AP~'LICATIONS
This applicarion is a continuation-inwpart of U,S: serial number 10!302,066 filed on November 22, 2002.
FII~:LD OR Tl~ ~IItYENTIO1~T
T~ presern invention relates to a modular knee prosthetic systean used to replace the natural knee and, more particularly, to a unicomparanezrtal and bicomparhnental modular knee system having various distal. posterior femoral components that are intercha'nge'able with each other and with various pat~ellar-femoral joint components.
BACKGItoUND OF THE »VENTT4N
In #~ee arthroplasty, portions of the natural louse joint are replaced with prosthetic knee components. Typically, these components include a tibia!
componelxt, a femoral component, and a patellar component. 'fhe femoral component generally includes a pair of spaced c~ndyles that articulate with the tI'bial component, The IS components are made ofntaterials that exhibit a low coe~~ci~t of friction they articulate against cxm another.
When the articulating ends of both the femur and tibia are replaced, the procedure is referred to as total knee replacement or Tlf~R. ll~uch et"fort has been devoted to performing a TKR that restores normal, pain-i~ee, functions ofthe lrnee in a short period of postopve time.
Several factors lead to icwg.~n success of TIC. One important ~a~Crc is soft-tissue balancing. 'The normal, non-diseased knee is c'onside'red properly balanced when the deflection between the medial and lateral condyles and fhe tibia!
plateau is equal throughout the entire range of motion, Ifthis balance is not achieved, abnormal knee acs occurs, and the TKR components and sunnealding ~ft fissure can expeclenee ea~ive forces even during normal range of motion. These excessive forces can further cause an abnormal gait, gain, and early failure of total knee replacements.

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Soft~tissue balancing can be achieved in TKR if the components are correctly sized and properly placed. Itt order to achieve p?~cdtging a TKIt.
surgery, equal tibial-femoral flexion gaps and ex,#~nsi~ gaps must be achieved. The flexion gap is defined as the space been the posterior coranal out on the distal femur and transverse cut on the proximal ri'bia, while doe knee is in 9Q° of flexion.
The extension gap is defined as the space between the transverse hut on distal femur and the transverse proximal tibial cut while the knee is in complete exkension. Soft tissue balance occurs when stability is achieved in both flexion acrd extension.
fearing a TKR surgery, a series of surgical crnnpromi~s is often used to 1(f achieve a balance of flexion and exbensi~ fps. Blevarion of the joint line is one such compromise. An elevation of the joint line occurs when there is a change in distance from the original articular surface to the newly reconsh~ucted surface. This change in dista~e is typically measured as a vertical distance from a fixed point an the tibia.
Far several reasons, the joint line can become elevated. Ex~ssit~e medial ar lateral releases and insertion of tliicicer plastic inserts can cause the line to elevate.
Further, the joint line can become elevated when the ~ cx~mpa~t is undersized. Such an undersize cau. create a larger flexion gap than ion gyp.
To balance these gaps, mare bane may need to be rennoved from the distal femur;
and 2Q this additional bone loss raises the joint line.
Unfortuxaately, a change in the joint lime cats negatively affect a wide array of components and operations of the Imee, such as the func,~rions of the PCL, collateral ligaments, and patello-femoral joint mechanics. These problems can be avoided or minimized if elevation of the faint line is reduced or, better yet, elimi~t~.
~5 Another surgical compromise often occurs when soft tissue gaps are n~
balance when implam~ting a distal femoral knee esis. A healthy balance of tlu~e . gaps maintaia~s the natEUal kinematics of the patient. The compromise occurs when the operating surgeon must choose one of six or seven differently sired distal femur .
prostheses; and the siz~o of these prostheses may not exactly match the size of an ideal 30 prosthesis for the patient. For example, current anterior referencing methodology to achieve balanced flexion and extension gaps in most patients requires the surgeon to slightly alter the joint line. if an anterior referencing sizing guide falls between two sizes, the surgeon could be farted to choose a smaller size prosthesis so the flexion rox.~~a.c~ 2 ~ d gap is not overstuffed. A sanaIler prosthesis, in such an instance however, can consequently enlarge the fle~rion gap as much as 3.Smm to 4mm.
Another im~po~nt ithat corttri6utes to the long term success of total knee replacements is loading and kinematics of the patellar-femoral joint.
Complications associated with patella failures account far up to 30',/0 of TKit revision lures. Many of these complications occur because of improper ar unnatural loading or kinematics of the patehar-feanoral joint. For example, ovexstu~ng the patellar-femorrat ,joint is one major cause of improper soft tissue loading and kinematics. In this regard, many surgeons use posterior referencing instrumentation whey sizing and pn~ring the femur for impGtnt resurfacing. On the one hand, posterior referencing allows the surgeon to balance tire tibias-femoral flexion and extension gaps without necessarily changitrg the joint line, On the other hand though, the use of p~terior referencing increases the risk of notching the anterior cortex and overstuffing the pakellar.noral joint.
1 S In short, currec~t knee systems after require an unwanted surgical compromise, Such compromises can alter the natural joint line of the patient ar overstuff the patellar-femoral jointr UnforEunatety, these camprcanises also negatively acct the natural kinematics of the patient and can, for example, increase strain on the PAL end other tendons and ligaments, increase implant wear, and decrease implant function.
Patients may be more ldcely to experience pain, reduced fCmction, and more frequent revision surgeries.
Current knee systems have outer disadvantages as well. bistal femoral prostheses are simply too large to fit through small incisions that are wised riurmg a minimally invasive surgery ar MtS, lvtIS has many advuntag« over traditional surgical techniques since it provides shorter incisions, faster recovery times, and generally less pain for the patient. 'hhe surgical technique, though, has limitations. As noted, current td~ental distal femoral prostheses cannot fit through the small incision, usually three inches in length.. To date, MIS has been generally Iin~i~:d to unicondylar or uuicompartmeatal knee replacement prostheses that are much smaller in sine and able to fit through the incision.
It would be advautageaus to stave a modular knee prosthetic sysb~n that has advantages over prior knee prosthetic systems and techniques. Such a system would ror.~3a-cm g have greater modular versatility to accommodate different patient anatoln~~es and joint conditions whale maintaining a relatively low component <;ount.
SUl~Y OF TIEItE ~NTYUI'~
The present invention is directed toward a modular knee system having various distal posterior femoral components that are interchangeable with each other and with various patellar-femorat joint components. Preferably; the modular knee system has a variety of components that ana interchangeable and connectable to resurface the distal femur using either a unicompartmental femoral lines prosthesis ar a bicompartmental femoral knee prosthesis. These components include a medial distal posterior femorat component, a lateral distal posterior femoral component, a patellar-femoral joint component, and an interconnection mechanism to modularly connect the components together.
The knee system of the present invention allows for modularity between the distal posterior femoral components and the patellar-femoral joint components.
The I S interchangeability of these components enables mixing and nmbching of multiple sues and thicknesses of all components. This interChangeability allows the surgeon to resurface the distal femur without overstutf'xng the patellar compartment or changing the natural iibial-femoral joint lice.
Cane advarnage of the present invention is that the modularity of components gives the surgeon more diversification when choosing sizes for the medial and lateral condyles. The deflection between these condyles and the ribial plateau, thus, can be more easily equalized thmagh~ut the range of motion. As such, the soft tissue can be more easily balanced.
Another important advantage of the present invention is that the various knee components are interchangeable and can be more correctly sized for an accwrate fit.
As such, more equal tibias-femoral flexion gaps and extension gaps can be achieved.
In partiauiar, excessive medial or lateral releases and insertion of thicker plastic inserts can be more easily avoided, Elevation of the joint line in these situations can be minimized or, better yet, avoided.
Further, modularity of the knee components enables a more natural balance between soft tissue gaps when implanting a distal femoral knee prosthesis. if, far example, different sizing occurs between the medial and lateral sides of the distal posterior components, differently sized dial past~ri~ femoral comb can be connected toge~er to accainmodate this variance of sizing. Thus, di~ently sired condyles may be implanted on the medial and lateral sidles to more closely replicate the natural anatomy of the patient. Further, a~tditional bone may be saved and not unnecessarily removed from the distal femur or from the tx'bia.
Since the present invention can more readily acxommodate various sixes during knee replacement surgery, the natural loc~.tion of the joint line can be maintained. Certain problems assoeiatcd whit altering the joint line can be avoided ~
The present modular knee system can also help achieve natural loading and kinematics of the patellarfemoral joint. Far example, the various sizes and interchangeability of knee campanents can enable more correctly nixed patellar-femoral joints. In some situations, overstuffing can be avoided.
As another important advantage, all of the individual components of the IS modular knee system of the present invention is small enough to be used during minimally invasive ~ ar 1HIS. Eaeh moduhur component can fit ~ a three inch incision. Even more importantly, the madular compon~ can be assemble<t after being inserted through the incision. Thus, the mode~lar knee system can be used with either unicomparimental, bicomparhnental, or tricompartmental preeedures (i.e., either unicondyIar, bicondylarr or tricompartmental knee replacements).
As yet even another advantage, the modularity of the present knee system reduces the overall number of individual components required in a knee product line.
This reduction has sigiuificmnt cost savings.
Acaordingty, the present invention comprises a, aombiarttion of f~ and advantages that overcome various problems, deficiencies, or shortcomings associated with prior devices. The various features and advantages of the invention will be readily apparent to those skilled in the art upon referring to the accompanying drawings and reading the following detailed description of the preferred emboduments of the invention.
BRIEF DF.SCRIPT~U1~TOF'I~E DRA.W'INGS
For a more detailed description of pref~ed ~bodiments of the present invention, reference will now he made to the accompanying drawings, wherein:
rorg r .. ~' ~ } ,' i Figure I illustrates a perspective view of two medial dist$1 posterior femoral ccnnof the present inveoticm.
Figure 2 illustrates a side view of the femoral components of Figure 1.
Figure 3 illustrates a perspective view a pateilar~femorat joint component of the present invention.
Figure '4 itlu~tes the condylar surface of the patellarfemoral joint component of Figure 3.
Figure 5 illustrates an exploded view of the two medial distal posterior fe~cnoral components of Figure I connecting to the patellar femoral joint component of Figure 3.
Figure 6 illustrates a pezspective view of a bicompartmental femoral knee with the two medial distal posterior femoral compozeents of Figure I connected to the patellar-f~noral joint component of Figure 3.
Figure 7 illustrates a single medial distal pos~arior femoral emnpanent.
Figure 8 iIlUStr&teS all exploded view of a uniaompartmental femoral knee with the single media.I distal posterior femoral component of Figure T and a single patellar-femoral joint component:
Figure 9 illtistxates a unicompartc~te~aI femoral knee with the medial distal posterior femoral component and the patellar-femoral joint component of Figure connected tog~her.
Figure 10 illustrates an e~cploded view of a first modular connection of a single mediat distal posterior femoral component connecting to a patellar-femoral component with dual condylar surfaces.
Figure I I illustrates a peis~ view of the cxmi~ of Figure 10 z5 Connected togexher.
Figure 12 illustrates as exploded view of a second modular caimeetian of a single m~iat distal posterior femoral component connecting to a pat~eliarfemoraI
component with duet condylar surfaces.
Figure 13 illustrates a perspective view of the components of Figure 1I
connected together.
Figure 14 illustrates a perspective view of a unicomparimental fennoral knee with the medial distal posterior femoral eamp~onent and the patellar.-femoral joint component connected to a tibial insert and tibial baseplate.
tor.a,3a-cte ~.~ i w Figure 1S illustrates a first exploded view of a five-piece femoral knee.
Figure 16 illustrates a second exploded view of the five..piece feraoral knee of Figure 1S.
Figure . 17 illustrates a perspective view of the 8ve-piece femoral knee of Figure 15 wherein the five components are co~mec~ed together to form a biocomparimental femoral knee.
Figure 18A illustrates a perspective view of a two-piecx bicampat~dmental fem~al knee prosthesis.
Figure 18B illustrates a perspective view of the two-piece bicompartmental I0 femoral k~e pris of Figure I8A.
Figure 18C illustrates another perspective view of the tovo-piece bicornpartmemal femornl k~e prosthesis of Figure 18A.
Figure 18D illustrates a perspective view of the femoral knee prosthesis of Figure I8A connected together.
Figure 19A ills a Active view of another embodiment of a two-pieae bicompartme~al femoral knee prosthesis.
Figure 19B illustrates anotl~ perspec~ve view of the tvwa~piece bicompartmontal femoral knee prosthesis of Figure I9A.
Figure 20A illustrates a perspective! view of a, complete knee prosthesis including a femoral knee prosthesis and a tibial knee prosthesis.
Figure 20B illustrates a side view of the knee prosthesis of Figure 20A.
Figure 20e illustrates another we view of the knee praskhesis of Figure 20A.
Figure 2QD ills anatber perspe~ve view of the knee prosthesis of Figure 20A:
Figure DOE ilk~sh~ates a perspective view of the assembled tibial insert.
Figure 21A illustrates a perspective view of another embodiment of a complete knee prosthesis including a femoral lrnee prosthesis and a tibial kaee prosthesis.
Figure 21B illustrates another perspective view of the knee prosthesis of Figure 21A.
romp m :: f D~T'A,ILED DESCRtPTIf?ht Figures I and 2 illustrate two separate distal posterior femoral componeerts generally at 14. Une componem is a raediai distal posterior femoral component (DPFC) 12, and a second component is a lateral DPFC I4. Both femoral components I2 and I4 have a smooth outer ~ndyiar sm~uCe I6 adapted to articulate with a tibial insert. Surface I6 is shaped as a partial femc~a! condyle that extends from a proximal pardon I8 to a distal portion 2U. A bone eng~ng surface 22 is appositely dispo~
firm the condylar 16. This ~ 22 includes sev~l flat, planar sections 24 that extend from the proximal I8 to the distal portion 2t). A stem 26 projects IO upwardly fiom the bone engaging surface 22. 'This stem 26 has a tapering cylindrical shape and is adapted to be inserted in t~ intramedullary canal of a femur.
The medial and lateral DPFC also includes a connector 28 located on alt enct surface 30 of the proximal portion 18. The connectors 28 are shaped as cylindrical, tapering recesses. These recesses extend into the body of tire femoral components.
Figures 3 and 4 illush~te a patellar-femoral joint component (PFJC) 40. The PFJC 40 has a smooth outer condylar surface 42 adapted to articulate with a tibial insert. Surface 42 is ~ as a partial femoral condyle that extends from a proximal portion 44 to a distal pardon 4b. A, bone engaging surface 48 is appositely disposed fi~om the condylar surface 42. This surface 48 includes several flat, plemar sections 50 #hat ex~xid from the proximal portion 44 to the distal portion 46.
The ~PFJC 4U also includes a connection mechanism 54 located on an end su~rfaee 56 of the pmxlmal portion 44. The connection mechanism 54 is shaped as two separate, spaced ions having a cylindrical, taping body. The proj~i~
extends outwardly firm the body of the PFJC.
Tanning also bo figure S and 6, cotmection mecluinism 54 of the PFIC 40 is adapted to engage and connect with the connects 28 an bath the medial T~PFC 12 and lateral DPFC I4. Specifically, the prajecticms of the coon mechanism 54 slideably press-fit to look into the recesses of the connectors 28. This connection may utilize a Morse taper fit.
(3ne skilled in the art will appreciate that many di~rent means exist for connecting the distal posterior femoral components 10 to the PFJC 40, In this regard, the cotmectors 28 could be configured as tapering nnale projections while the rot.a3acte g connection mechanism is configured as a tapering recess ~ to receive the projections. Other connec~ons e~tist as well. For example; the ion mechanism could be configured t4 snapingiy engage the connectors or cx~nfigured as a bayonet type, connection. Further, the connectioa between the connection mechanism S 5~ and the connectors Z~ could be permanent or removeably connected.
It is important to note that when the medial DPFC I2 and the lateral DPFC 1.4 connect to the PFJC 40, these components form a complete, full femoral lmee prosthesis 60 (see Figure 6). This prosthesis b0 functions as a traditional oae-piece bicompat~tmer~tal femoral prosthesis. As s~h, the p~rstbesis~ G0 may be used as a biccnnpartmental femoral prosthesis for total knee replacements. The important adva~age of the present invention, though, is that the prosthesis 60 is composed of several modular pieces. Specifically, the prosthesis is composed of three separate, interconnectable pieces, namely a medial DPFC i2, a lateral DPFC I4, and a PFJC
40.
As noted, the distal pasberior fe~norai component's have a partial condylar sur~Ce lb, and the PFJC 40 has a partial condylar surface 42. When these components are cvnne~d together to form the femoral lknee prosthesis 60, the the surfaces Ib and 4~ join and form a full condylar surface 62. Tl~is surface 62 exi~ds from the distal portion 20 of the distal posterior femoral components to the distal portion 46 of the PFJC. Preferably, this surface C2 is ron~tinuous and seamless at the junction or unicm 66 fi~om surface Ib to stu~ace 42. No bumps, ridges, seams, imde~tions, channcis, or the lice should exist at the jtmctzarr bb where the surfaces meet.
Figures ? - 9 illustrate cme of the modular -pxaperties of the invention.
Figure 7 shows a single distal posterior femoral component 80. DPFC 80 is similarly configured to the distal posterior femoral compone~s shaven in Figures 1 and 2. This component 80 may be shaped for use as a medial I3PFC, lateral DPFC, or generic and useable for both medial and lattecrnl indications.
Figure 8 shows a patellar-ii~no~ joimt componenfi 9Q that is similarly configured to the PFJC 40 shown in figures 3 and ~. 4ne important ex~tiomis the PFTC 90 is vot shaped for bicom~frnental use but for unicompartm~tal use. More specifically, the PFJC 90 has a single smooth outer condylar strx~ace 32 adapted to articulate with a tibial insert. gurface 9~ is shaped as a partial single femoral condyle rom3acm g .i~ 1,~1 that extends from a proximal portion 94 to a distal portion 96. A bone engaging surface 98 is oppositely disposed from die condylar stnrface 92. This surface includes several flat, Planar seettons 100 that extend firm the proximal portion 94 to the distal portion 96. The PFJC 90 also includes a ion mectanis~n 102 located on as end surface 144 of the proximal portion 94. The connection mechanism 102 is shaped as a single projection having a cylindrical, tapearing body. This pmjcction extends outwardly from the body of the PFJC and is adapted to fit into a connector 106 shap0d as a recess on the DPFC 80. The ~ectiori between the DPFC 80 and PFJC ~ are similar to the connections did in connection with Figures 1-6; one difference is the connection in Figures '7 - 9 uses a single connection mechanism or P~J~tion and a single connector or recess.
As shown in Figures 7 -- 9 then, one advantage of the present invention that the DPFC 80 and the PFJC 94 connect to >orrn a complete femoral tc~e prosthesis 1 I0 (see Figure 9). This prostbesis 1 i0 functions as a traditional one-Iriece uaicampartmentai femoral prosthesis. One important advantage of the present ~v~~on is that the unicomparhmental prosthesis 1 I0 is composed of several modular pieces. Specifically, the pmsthasis is composed of tvvo separate, interconnectable pieces, ~mely a DPFC 80 aml a PFJC 90.
Figures I0 -13 show more examples of the diversification of modularity of the present invention. These figures show a DPFC 120 that is canneotable to a PFJC
122.
The DPFC 120 is similar to the distal posterior femoral components shown in Figures 1 and 2, and PFJC 122 is similar to the patellar-femoral joint co~apanent shown in Figures 3 and 4. In Figures 10 and 1 I dough, the PFJC I22 connects to a single DPFC 120 on the medial side. By contrast, in Figures 12 and 13, the FFJC i22 2S connects to a singly DPFC 120 on the lateral side.
Figure 14 shows one example how the modular connponents of the present inv~tion can be utilized. Here, a DFFC 130 at~d a PFJC 132 are connected together to form a unicoznparlrnental i~moral prosthesis 134. This prosthesis 134 has an extended or enlarg~l stem 136, but otherwise is generally similar to the unicampardmental prosthesis 110 shown in Figure 9.
As shown in Figure 14, the unicampartmental femoral prosthesis I34 has a bone engaging ~ 140 with a porous or Cancellous-St<uctiued Titanium (CSTi) coating to enhance bone engagement. An cuter articulating condylar surface I42 ~''~ ' ~ ~i abuts against a tibial insert 144. This insert i44 is ccnmec~ed to a tibial bas~late 146 having a base -portion 148 and ~ screw or stem ISO extending downwardly from the base portion. The ~i~ial insert 144 and baseplate i46 are known to those skilled in the. art and may be similar, for exaraple, to those sold by Centerpulse Orthopedics Tnc. of Austin, Texas.
Figures 15 -17 show yet more examples of the diversiiTication of modularity of the present invention. Here, a complete femoral knee prosthesis i 60 is shown.
This prosthesis 160 includes a single PFJC I62 and two DFFC 164 and functions as a traditional bicompartmeutal prosthesis as shown and described in $gure 6. As one I O important differ ence, each DPFC 164 is formed &am two separate oomponemts, namely a top half 166 and a bottom half 168: When the top half i66 and m half 168 are aannected, they function as tf~e DPFC d~ in Figures 1 and 2. Here though, each top half 166 includes a connector 1T~; and each bottom half includes a connector l?2. The connectors 1'~0 and 1~2 are shown as recesses and projections;
1S respectively, and slideably press-fit together to farm single distal posterior femoral components.
As discussed in connection with connection mechanism 54 of PFJC 4U and connectors 28 of DPFC 12 and 14 in Figures S and 6, the connectors 17(1 and i92 may have various configurations known to those sIGilIed in the art to a.~hieve a permanent 20 or removable connection between the top half 166 and bottom half i68. Fsach articulating componem may attach to a third body connection piece that would bridge the annponents.
One important advanmge of die present inv~on is that ati of the individual, ~e distal pasbexior fe~mocal components and the patteU~arf~noretl joint 2S components are adapted to bQ use ~ minnmaily invasive surgery (MIS) t~niques.
MIS is Intended to allow far the maximum preservation of bone stpck, restoration of kinematics, minimal disturbance of the patellar tendon, and rapid rehabilitation postoperatively. During an MIS kaee surgery, a 1 ~!x to 3 inch incision is made. The DPFC and PFJC are small enough to fit through this incision. Thus, these 3U components can be Ft through the incision and then assembled to ford a uniconapartmental femoral knee, bicampartmental femoral knee, or hybrid of these two (the various embodiments being shown in Figures 1-1?~.
~°La~a-crn 11 Another advantage of the present invention is the distal posterior femoral acnnpo~nents can be made to be Completely interchangeable. Thus, no need exists for separate mediaUlateral or lei~lrlght components. FurEher the DPFC and PFJC can be made to have various sizes and thicknesses to accommodate various patient needs.
S The components can even be coated w~ CSTi or other coatings known to those skilled in the art to enhance bone growth or cement retention.
As another adva~ge, the total modular design of the present inventiou~, in addition to being compatible with MiS, allows the surgeon to resurface only the anatomy that requires resurfacing. Thus, the surgeon can assemble a femoral knee prosthesis to better fit the needs of the individual patient and minimize or elimin$te ssary bone cuts.
Further yet, modularity of the present invention can also save the manufacturer tt~nendous inventory costs, especially if existing ~entation can be used The charts below summarize one potential manufacturing cost savings. The chart on the Left shows a typical number of c~nents for a non modular femoral knee system.
The clxar~t on the right shows a typical numher of ccxnponents utilizing the modular components of the present invention. As shown, an inventory can be reduced by appmoxiinately 4I components.
The number of components 'The number of for a coanponents coatplete global knee sysbam: of a c~plet~e global I4 primary posterior stabilize "modular" knee f~ left system:

and right l4 primary cruciate retain ~ Unicomponeuts for left and right 7 Asian/High Flex Uni 10 primary posterior stabilize Components components for Asian (high~ 3 patellar-femoral flex) joint market for right components for left 10 primary cruciate retainModularity 3 patellar femoral components joing for Asian (high flex) market components for for right ri~

7 Unicomponems 6 patellar-femoral joint components Total= 61 co~pOm nests ( Total = 20 zo More advantages of the present invention are listed below and are explained in the Summary section:
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Full modularity between anterior and distal and posterior femoral components eliminates the need for the surgeon to compromise the patient's nafiral gait.
The system provides the surgeon with flex~'bility and control in implant sizing, Multiple distal and posterior compcments allow multiple ethnic anatomies to be replicated with one knee system. For instance, Asian patients may requ#te longer posterior condyles to replicate their ~ anatomy. The option of attaching an Asian unicondyIar component to a F'F3C will allow the surgeon to convert the prosthesis to allow frn high flexion.
A stand-alone patella femoral component would allow tlu~ PFJC to be incluc~d in the same system as flow ~ knee.
A stand-alone distal/posierior component can be used as an MIS
unicompartmecttal prosthesis. Thus the surgeon cmn make the intraoperative choice of unicompartmental or bicompartmental prot~ure.
A stand alone Asian distaUposterior component would allow a unicompartmentaI or bicomparmental procedure that would closely replicate the _ ~$;~ Amy.
Posterior femoral components of two different thickness options may be implanted on the medial and lateral candyles. This option will allow the surgeon to correctly replicate the natural patient anatomy.
An attachment or connection feature and mechanism between the anterior FF3C attd the distal components: The attachment allows a surgeon to convert a uaico~mp~artmeut~al knee to a primary knee by simply attaching the anterior component to the existung distaUposterior compo~t(s~. The_ at~c~hmeatt ~ would also allow the surgeon to convert a FF3C ~ a total knee re~placeaaent witho~rt revising the PFJC.
Figures 18A - 18C show ano~~ embodiment of the invention. A
bicompartmental femoral knee prosthesis 200 comprises two separate and modular components, a lateral fecn~oral knee condyle 202 and a medial femoral knee condyle 204. Both femoral componez~ 202 and 204 have a smooth outer condylar surface 206A and 2068, respectively, adapted to articulate with a fx'bial insert. Each surface 20b is shaped as~ a curved femoral condyle that extends from a pmxi~mal portion 208 to a distal portion 210. A bone engaging surface 2I2 is oppositely disposed from the condylar surface 206. This surface 212 includes several flat, planar sections 214 that rom3a-c~ 13 _ ~,~ ~ f r., extend from the proximal portion 20$ to the distal portion 2i0. An optional stem (such as stem 26 shown Figure i) can be formed to each condyle for insertion in the intramedullary canal of a feraur.
The medial and lateral condyles also include a connection or locking mechanism 218 located .on a side surface 220A and 2208, respectively. This locking mechanism includes a male component 222 and a female component ?,24. The male component is shaped as a rectangular protrusion that extends outwardly from side surface 220A. The female component is shaped as a rectangular recess that extends into side surface 220B. These components are shaped to lockinglY engage in a More i0 taper c~n~ction.
Looking to Figure i 8D, when the medial and lateral femoral knee condytes connect together, these two components form a complete, full femoral knee prosthesis 230. This prosthesis functions as a Traditional one-gie~ bicompaMmentai femoral prosthesis and includes a foil outer condylar surface 232. adapted to articulate with a tibial insert a~ natural patella or patellar prosthesis. The prosthesis may be used as a bicompartznental feraaral prosthesis for total lmee replacements.
Looking to Figures l8rr and 18D, preferably the pews~esis is 'dwided across a sagital plane or medial-lateral plane 234 (shown in Figure l8fC). This plane splits the prosthesis into two separate and distinct halves, the lateral condyle 202 and medial condyle 204. Once condyles 202 and 204 are connected, surface 23x is cantlnuous.
As shown m Figure 18D, this surface 232 is preferably seamless at the junction or union where eondyle 202 connects to condyle 204. No bumps, ridges, sums, indentations, channels, or the like should exist at the juuc~on where surfaces and 206B meet.
Figures 19A and 19B show another embodiment of the invention. A
bieompatrmental femoral knee prosthesis 300 irises two separate and modular components, a lateral femoral knee condyle 302 and a medial femoral knee co~rdyle 304. Both femoral components 302 and 304 have a smooth outer condylar surface 306A and 306B, respectively, adapted to articulate with a 1x'bial insert. Each surface 306 is shaped as a curved femoral c~yle that extends fronn a proximal portion to a distal portion 310. A bone engaging surface 3i2 is oppositely disposed from the condylar surface 306. This surface 312 includes several flat, planar sections 3I4 that extend from the proximal portion 308 to the distal portion 310. An optional stem coms4-ce~ i4 ')-.~
(such as stem 26 shown Figure 1) can be formed to each amdyie fcs' ikon in the intramedullary tonal of a femur:
The medial and lateral condyles also include a connection or looking mec3.1$ located. on a side surface 320A and. 324 B, respectively. This tacking mechanism includes a male component 322 and a female component 324. The male component is shaped as a rectangular ~ot<usion that extends outwardly from side surface 320A. The female component is shaped as a rectangular recess that extends into side surface 3208. These components are std to lockingly engage in a Morse taper connection.
When the medial and lateral femoral trnee condyles of Figures 19A and 198 connect together, these two components form a complete;, full femoral knee prosthesis (identical to the prosthesis 230 shown in Figure 18D). This prosthesis functions as a traditional one-piece bic~mp~tnentai femoral prosthesis and includes a full outer c~ndyiar surface ~ to articulate with a tibial inssert and natural ~teiia, or patellar IS prosthesis, The prosthesis may be used as a bicompartmentat femoral prosthesis for total knee replacements.
As shown in Figure 198, the prosthesis 304 is divided across two diff~nt planes, medial-lateral plane 334 and an anterior~osterior plane 336. Tlxese planes split the prosthesis into two separate and distinct halves, the lateral cx~ndyle 302 and medial condyle 304. Further, the planes da not equally split the prosthesis;
two condyles have di~'erent shapes. The lateral condyle 302 has an enlarged patellar-f~noral joint section 340 that forms a portion_ of the prosthetic troehlear groove adapted to articulate with a natural or prosthetic patella. Section 340 h~ a somewhat regular shape that ext~ds beyo~ the medial-lateral plane 334 and above the anor posterior phtne 33f.
Once condyles 302 and 304 are connected, pleeferably they farm a continuous and seamless junction or union where the eondyles connect. No bumps, ridges, seams, indentations, channels, or the tike should exist at the junction where stufaces 30GA and 3068 meet.
One skilled in the art will appreciate that many different means exist far connecting the lateral and medial fexporal knee condyles of Figures 18 and 19.
In this regard, the locking mechanism 218 (Figures I8A -18 C) and 318 (Figures IgA and 198) could be configured as other ty~s of tapered locking or press-fit lions.
r°i.~~a.c~ 15 'The male and female components could be shaped as cylindrical proje~:ons and recesses, respectively. Further, the locking mechanism could be cotrf~gured to use a bayonet type connection or configured to snappingly engage each other.
Further, the connection between tt~se two condyles can be permanent or removeable. Further yet, multiple locking mism can be employed. mechanisms can be positioned along the side surface or elsewhere on the femoral condyles.
Figures 20A - 20D illustrate a prosthetic knee system or a complete knee prosthesis 440 adapted to be used far total knee arthraplasty. System 400 includes two main components, a tbmoral knee psis 4p2 and a tibial l~nee prosthesis 404.
The femoral knee prosthesis 402 comprises two separate and modular components, a lateral femoral knee candyle 406 and a medial femoral knee condyle 408. These components are identical to the eondyles 202 and 204 discussed in connection with Figures 18A -18D, and reference should be made to those figures far a description Of condyles 406 and 408.
1 S The tibial knee prosthesis 404 includes two separate and modular cxxmpanents, a ti'vial insert 420 and a tibiat baseplate 422. The tt'bial baseplate 4~2 8enerally has an elliptical or oval shape and comprises a lateral component 430 and a medial component 432. These two components generally have a half moon shape with rounded ends 436 and planar surfaces 438 and 440. Surface 438 is oppositely disposed from surface 440 and is adapted to engage a planar bone surface of the natural tibia. Surface 440 is adapted to engage and connect to the tt'bial insert 420 and includes a wall or shoulder 441 that extends around the outer perimeter.
Cylindrical bores 443 extend tbraugh the tibial baseplate and are adapted to receive Abone screws far fastening the baseplate to tibial bone.
The medial and lateral components also include a connection or locking mechanism 442 located on side surfaces 444A arid 444B. This locking mechanism includes a malt component 446 and a female component 448. The mate component is shaped as a rectangular protrusion that extends outwardly from side surface 444B.
Tile femate component as shaped as a t~ecta~tgular recess that extends unto side surface 444A. These components are shaped to lackingly engage in a Morse taper cannoction to connect the components together.
When the lateral component 430 and medial caixtpone~ 432 connecx together, these two components foam a complete and assembled tibial baseplate. In this assembled state, the hbial baseplate functions as a t~raditio~l One-piece, mtegrall f formed tx'bial ts~seplatte. The assembled baseplate may be used as a biccs~apa~nental tt'bial baseplate for total knee replacements.
'The tibiat insert 4~0 generally has an eltiptic~l or oval s4ape ~1 comprises a lateral component 450 and a medial component 452, These two components generally hav~e~ a hatf~moon shape with rounded ends 456 and are complementary to the shapes of the lateral component 430 and medial component 432, respectively.
Both components 430 and 45Z have a smooth outer condylar surface 460A and 4608, respectively, adapted to articulate with the condylar surfaces of candyles 406 and 4Q8.
1(? A generally planar surface 4tr4 is oppositeiy disposed from the condylar surface and is adapted to engage and connect to surface 440 of the dbial baseplate.
A ledge 468 extends around the outer perimet~.~r and is adapted to engage shoulder 441 when tibial insert 420 and tibial baseplate 422 are connected together.
The tibial insert and baseplate can connect together in a variety of ways.
Ledge 468 i 5 can snappingly engage into shoulder 441 m firmly r~onnect the tibial insext and _ . p~~. Further, these two components can he adapted to connect permanently ar removeably.
When the lateral componern 450 and medial component 452 connect togother, these two components farm a complete, assembled tibial insect. In this assembled 20 state, the tibial insect functions as a traditional one-piece, integrally fo~tned tibial insert. The assembled insert may be used as a bicomparbtnental ti'bial insert for total knee replacements.
As shown in Figure 2flE, once the lateral component 450 and medial component 452 are connected, preferably they form a continuous and seamless 25 junction or union where the condyles connect. hTo bumps, ridges, seams, indentations, channels, or the like should exist at the junction where surfaces 406A
and 4068 m~;t (Figure 20D). This may have various configurations known to those skilled in the art to achieve a smooth permanent or removeable connection.
Such examples include, but are not limited to, Blling the transit~ont with ~s such as a 30 biologic hydrogel or design~tn~ and manufacturing to precise tolerances to trunixni~e the egects of transition seams.
As shown in Figure 2UD, the prosthetic knee system 400 (including the femoral knee prosthesis 402, tibial insert 420, and tibial baseplate 422) is divided toca.3acc~ 17 across a single mediallateral plane 480. This planes splits the prosthesis into two separate and distinct halves that are generally equal in size and shape on the medial and lateral sides.
Figures 21A and 21B illustrate a prosthetic knee system or a complete knee prosthesis 500 adapted to be used for total knee arthraplasly. System 500 includes two main ca~ponents, a femoral knee prosthesis S02 and a tibial lame prosthesis 504.
The femoral knee prosthesis 502 comprises two separate and modular componea~ts, a lateral femoral. knee condyle 506 and a medial femoral knee condyle 508.
'these components are identical to the condyles 302 and 304 discussed in connection wig Figures 19A and 19B, and reference should be made to those figures for a description of condyles 506 and 508. The tibial knee prosthesis 504 includes two scparata and modular compouems; a 1x'bial insert 520 and a tibial date 522. These c~noponents are identical to the tibial insert 420 and tibial basepiate 422 did in connection with Figures 20A - 20E, and refereance should be to arose figures for a description of tibial insert 520 and tx'bial baseplate 522.
One skilled in the art will appr~iate cat many different means exist for connecting the Iaterat and medial components of the tibias knee prosthesis of Figures and 21. Ia this regard, the locking mechanism could be ~afigured as other types of tapered locking or press-ft connections. The male and female compone~s could 20 be shaped as cylindrical projections and recess, respectively. Further, the locking mechanism could be oanfigured to use a bayonet type connection or red to ~~~Y en8~e e~h other. Further, the connection between these two condyles can be permanent or removeable. Further yet, multiple locking mechanism can be employed. These mechanisms can be positioned along the side surface or elsewhere on the femoral condyles.
one important advantage of the present invention is that all of the medial and lateral components in the prosthetic knee systems 400 and 5~ of Figures 20 acct 21 are composed of modular components. All of these individual, ~ components ire ~ to be used in minimally invasive surgery (M1S) techniques. MiS is intended to allow for the maximum preservation of bone stock, restoration of kinematics, minimal disturbance of the patellar t~don, and rapid rehabilitation postoperatively. During an M1S knee surgery, a 1 '/a to~ 3 inch incision is made. The individual, separate components are small enough to fit through ibis incision.
Thus, ioia~d.crr 18 .. ~ ~ ~.~ ' Jt these components can be fit tbrou~h the incision and then assembled irnvivo to form the prosthetic knee system.
During a traditional kaee replacement surgery, the patella is evert~d in order to place the femotai and tibial comp. One important advantage of the pre~nt invemion is that all of the medial and lateral components in the prosthetic knee systems 400 and S00 of Figures 20 and 2I can be placed witha~t evertiag the patella.
Specif tally, a small MiS incision is made on the lateral side of the knee, and a small IIrQS incision is made on the medial sick of the knee. The la~rat components aoe inserted through the lateral MiS incision, and the medial components are inserted IO through the medial lldES incision. The media! and Ia~teral crnmponents am thin assembled together in-viva. Since the independent, separate components are small and as~mbled in viva, the nahnsl patella ofthe patient is not required to be evertetl.
Figures 20 and 2l show the tibial knee prosthesis having a medial and lateral tl'biat insert and a medial and lateral tc'bia! baseplate. These compon~s cwt be I S assembled in various ways to form the ri'bial knee prosthesis. As one example, the ta~ral tibial inset and lateral tibial baseglate can be separately positioned through the lateral MIS incision. Once positioned in the lateral compartment of the knee, these two components cam be cotutected toge#her ba foam the lateral portion of the t~'bial knee prosthesis. Next, the medial tibial insert and medial tibial baseplate can be 20 separately positioned through itie medial MIS i~ision. Once positioned in the medial compartment of the knee, these two components can be comWd together to form tIm medial portion of tibial knee prosthesis. The lateral portion of ~ fbiat .twee prosthesis and the medial portion of the tibial knee prosthesis can then ~e connected is viva to form the a~mptete and assembled tibial knee prosthesis.
25 As another example, some of the components of the tibia! knee prosthesis can be prerassearbled before inserting them through the MIS incision.
Specifically, the lateral tibia! insert and lateral. tibia! baseplate can be connected together outside Of the pat~ic~tt to farm the lateral portion of the tibial knee prosthesis. This lateral assembly can then be positioned through the lateral IvIIS in~3sia~. Likewise, the medial tibia!
30 insert and nnediat tibial baseplate can be connected together outside of the patient to form the medial portion of the tibiaI knee prosthesis. This medial assembly can then be positioned through the medial MIS incision. Once the medial and lateral IUI~434«CIP 19 .<'~
assemblies are through the MIS incision, these assemblies can be connected to form the complete and assembled tibial knee prosthesis.
While preferred embodiments of this invent have been shown and described, modifications thereof cau be made by one skilled in the art without departing from the spirit or teaching of this inv~tion. '1"h~ embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the system, app~tratas, and oaethods are possible and are within the scope of the inventions claimed below Accordingly; the scope of prateet;:on is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope la of which shaft incluc~ all equivalen#s of the subject matter of the claims.
rot.~~a.cte 2t?

Claims (20)

1. A prosthetic knee system, comprising:
a femoral knee prosthesis formed of two separate components, a lateral condyle and a medial condyle, wherein the lateral and medial condyles are assembled in-vivo;
a tibial knee insert formed of two separate components, a lateral insert adapted to articulate with the lateral condyle and a medial insert adapted to articulate with the medial condyle; and a tibial baseplate formed of two separate components, a lateral baseplate component and a medial baseplate component, wherein the lateral insert connects to the lateral baseplate component, the medial insert connects to the medial baseplate component, and the lateral baseplate component connects in-vivo to the medial baseplate component.

2. The prosthetic knee system of claim 1 wherein a femoral locking mechanism connects the lateral condyle to the medial condyle.

3. The prosthetic knee system of claim 2 wherein a tibial locking mechanism connects the lateral baseplate component to the medial baseplate component.

4. The prosthetic knee system of claim 3 wherein the tibial and femoral locking mechanisms include a male protrusion and a female recess.

5. The prosthetic knee system of claim 4 wherein the tibial and femoral locking mechanisms form a Morse taper connection.

6. The prosthetic knee system of claim 1 wherein the lateral and medial inserts include a recess adapted to engage a shoulder on the lateral and medial baseplate components.

7. The prosthetic knee system of claim 6 wherein lateral insert is connected in-vivo to the lateral baseplate component, and the medial insert is connected in-vivo to the medial baseplate component.

8. A modular prosthetic knee system, comprising:
a femoral knee prosthesis formed of two separate and different components connectable together, a lateral condyle and a medial condyle, wherein the lateral and medial condyles are connected together in-vivo;
a tibial knee insert formed of two separate components, a lateral insert having an articulation surface adapted to articulate with the lateral condyle and a medial insert having an articulation surface adapted to articulate with the medial condyle; and a tibial baseplate formed of two separate components connectable together, a lateral baseplate component and a medial baseplate component, the lateral insert being connected to the lateral baseplate component, and the medial insert being connected to the medial baseplate component, wherein the lateral and medial baseplate components are connected together in-vivo.

9. The prosthetic knee system of claim 8 wherein the lateral and medial condyles connect at a first junction along a medial-lateral plane.

10. The prosthetic knee system of claim 9 wherein the lateral and medial condyles connect at a second junction along an anterior-posterior plane.

11. The prosthetic knee system of claim 10 wherein the first and second junctions form a seamless interface.

12. The prosthetic knee system of claim 8 wherein the lateral and medial inserts connect at a junction along a medial-lateral plane.

13. The prosthetic knee system of claim 12 wherein the junction forms a seamless interface.

14. The prosthetic knee system of claim 8 wherein the tibial knee insert and tibial baseplate are divided along a medial-lateral plane.

15. The prosthetic knee system of claim 14 wherein the lateral and medial inserts have a half-moon shape and connect together to form a substantially oval shape.

16. A modular prosthetic knee system implantable in a knee using minimally invasive surgery, the prosthetic knee system comprising:
a femoral knee prosthesis formed of a lateral condyle and a medial condyle, wherein the lateral and medial condyles are separate components that are connected together in-vivo; and a tibial knee prosthesis having two separate components including a lateral insert and baseplate and a medial insert and baseplate, the tibial knee prosthesis having an articulation surface for articulating with the lateral and medial condyles of the femoral knee prosthesis, wherein lateral insert and baseplate are inserted through a lateral incision in the knee and the medial insert and baseplate are inserted through a medial incision in the knee, the lateral insert and baseplate being connectable in-vivo to the medial insert and baseplate.

17. The modular prosthetic knee system of claim 16 wherein the tibial knee prosthesis is divided along a medial-lateral plane to form the two separate components, the lateral insert and baseplate and the medial insert and baseplate.

18. The modular prosthetic knee system of claim 17 wherein the femoral knee prosthesis is divided along the medial-lateral plane to form the two separate components, the lateral condyle and the medial condyle.

19. The modular prosthetic knee system of claim of claim 16 wherein the tibial knee prosthesis has a substantially oval shape.

20. The modular prosthetic knee system of claim 19 wherein the lateral insert and baseplate have a half-moon shape, and the medial insert and baseplate have a half-moon shape.