CA2225322A1

CA2225322A1 - Modular joint prosthesis stabilization and augmentation system

Info

Publication number: CA2225322A1
Application number: CA002225322A
Authority: CA
Inventors: Jason T. Gulbinas; John E. Slamin; Michael J. O'neil
Original assignee: Johnson and Johnson Professional Inc
Current assignee: Johnson and Johnson Professional Inc
Priority date: 1996-12-23
Filing date: 1997-12-19
Publication date: 1998-06-23
Also published as: US5766255A; EP0850606A3; DE69729058D1; EP0850606B1; JPH10309296A; DE69729058T2; EP0850606A2

Abstract

A modular joint prosthesis system includes an articulation component having a bone engaging surface and an opposed articulation surface. Fixation peg members and/or augmentation components are selectively attachable to the bone engaging surface of the articulation component. The articulation component may be a cruciate sacrificing femoral component of a knee prosthesis.

Description

MODULAR JOINT PROSTHESIS STARn.~7.~TION AND AUGMENTATION SYSTEM

CROSS REFERENCE TO RELATED APPLICATIONS

2 Not Applicable.

Not Applicable.

8 The invention relates to joint prosthçses having enh~nced stabillty and modularity.

Joint arthroplasty is a well known surgical procedure by which a ~licç~ed and/or11 damaged natural joint is replaced by a prosthelic joint. Joint arthroplasty is commonly 12 performed for knees, hips, elbows, and other joints. The h~alth and condition of the joint to 13 be replaced dictate the type of prosthesis that can suitably he used to replace the natural 14 joint. For ex~mrle, knee prosthçses, and particularly femoral co,l,~ollents of knee prostheses, are available in dirr~ei~t designs to meet the needs of varying patient con(lition~

17 Some femoral co",ponents for knee joint prosthçses are known as cnuciate ret~ining 18 femoral co,-,l)onents since they are useful as a prosthesis co,pollent where a patient's 19 cnuciate lig~mPnt~ are not s~r ficed during a knee arthroplasty procedure. This type of femoral co.,l~onent t,vpically has fixation pegs integrally mated upon the medial and lateral 21 distal flats of the superior surface of the prosth~ to stabilize the prosth~ upon mounting 22 to the femur. The cnuciate lig~m~n~ also contribute to the stabiiity of the artificial knee 23 joint.

Another type of femoral co",pollent for a knee joint prosthesis is known as a 26 cmci~ting ~çrificing femoral colll~onent. This type of prosthesi~ component is useful where 27 the patient's cruciate lig~m~ntc are non-functional or must be r~moved in the course of a 28 knee arthroplasty procedure. Cnuciate sacrificinp femoral components typically have an NUrTER, McCl~NNEN ~ FISH, I~ P
Telcphr~: ~617) 439-~mo F~e~mile: (617) g73 e,748 intercondylar notch formed on a superior, bone en~ging surface of the femor~l component.
2 This structure is in the form of a box, having substantially vertical medial, lateral, anterior 3 and posterior walls, and a subst~nti~lly horizontal superior wall. The intercondylar notch is 4 mounted within the patient's femur to stabilize the prosth~si~ Typically, an al,ellur~ is S formed in the superior wall of the intercondylar notch and it is useful to mate a femoral stem 6 to the femoral coll~nent. The femoral stem helps to anchor the femoral colllponent to a 7 patient's femur, and to contribute stability to the artificial joint.
9 Femoral component fiY~tion in cruciate substituting total knee repl~cçm~-nt surgery is somP-tim~s achieved through cement ~tt~rhmPnt of the femoral co,llponent to the ple~al~d 11 femur while stability is imparted to the femoral cG~Ilponent by the intercondylar notch, 12 femoral chamfer cuts, and the optional ~tt~shment of femoral stems or rods. It is sometimes 13 possible for cruciate substit~lting femoral components to loosen and thus contribute to the 14 need for total knee repl~rem~nt surgery and çnh~nce~ stabili7~tion of the prosthesis.
16 In some instances, due to disease or trauma, in~llfficient healthy bony mass exists at 17 the distal end of a bone (e.g., the femur) to which a joint prosthesis is to be secured. In 18 arthroplasty procedules, it is often n~eS~y to remove additional portions of bone (e.g., the 19 femur) in an asymmetrir~l manner, to ensure sufficient ~nchoring and proper fit for a prosthesis. In the example of knee joint arthroplasty, it is sometimes ne~s~ry to ~ngm~nt 21 the superior portion of the femoral component prosthesis to add additional thickn~s to the 22 prosthesi~ to colll~nsate for any removed bony tissue. The femoral colllponent can be 23 ~lugmPn~ by adding ~llgm~nting blocks of al ~lop-iate shapes and sizes to the superior 24 surface thereof. Various types of ~llgm~nt~tion blocks are known to those having ordill~y skill in the art. An eYemrl~ry augmçnt~tion system is disclosed in U.S. Patent No.
26 4,936,847 (~nginçlli).

28 The stability of cruciate substituting femoral colllponents can be reduced with the 29 in~t~ tion of ~ngmçnt~tion colllponer ts, some of which can approach the height of the intercondylar notch. Since these prostheses rely largely on the intercondylar notch for secure NUTTER, McCLENNEN ~ FISH. I~P
Telq~: /61n ~34 ~~
F~ e: (61n97~9748 -2-engagement within the femur, any relative decrease in the height of the intercondylar notch 2 above the medial and lateral distal flats can decrease the stability of the femoral component.

4 Many existing knee prosthesis designs do not offer the ability to selectively enh~nce ~rosthesis stability of the femoral component. ProsthPcic stability can be a problem of 6 particular concern in revision cruciate subalilulinP femoral components that require 7 ~n~m~nt~tion systems. It would thus be desirable to offer improved joint prostheses 8 co,l,ponents which offer surgeons increased versatility to achieve prosthesis stability.
SUMMARY OF THE INVENTION
11 The present invention relates to modul~r joint prosthçses that offer a~1~eo1-s enh~nc~d 12 versatility to achieve prosthecic co",ponent stability. In particular, the prosth~cic system of 13 the invention enables surgeons to selectively add fixation stabilizing members and/or 14 allgm~nt~tion co~lponents. While the invention is applicable to a variety of jcint prosthP-cic co",l~nents in which stabilization is il"poll~nt and allgment~tion is sometimes ne~çs~ry, the 16 invention is described herein with respect to femoral components of knee prostheses 18 The invention comprices a modular joint prosthecic that incl~ldes an articul~tiorl 19 co--,ponent, such as a femoral co---ponent of a knee prosth~sis, having a first, bone~-ng~ging surface and a second, artiClll~tioll surface. At least one secu.e--.ent cavity is formed in the 21 first surface, and most preferably a secu~.nent cavity is formed on each of the medial and 22 lateral distal flats of the femoral co---ponent. The system also includes at least one elong~te 23 fixation peg member, each of which is selectively mateable to the securement cavity in the 24 first surface to provide enhanced prothesis stability. The fixation pegs each have distal and proximal ends and include an axial bore which may include int~rn~l fiY~tion structures such 26 as int~ l threads. The system also includes a collet member for each fixation peg, and 27 each collet member has two or more expandable elements that are able to selectively engage 28 - the sidewalls of one of the securement cavities. A bore preferably extends through the 29 collet, and at least a proximal portion of the bore may include fixation structures such as internal threads. One or more expansion pins are also provided and each has a distal end 31 that is ~ ç to expand the collet and a proximal end which may include a structure, such as NUrTI~ McClENNEN h FlS4 LLP
T.~: (617) 439~
F~ccimilc: (617) g73-g748 external threads, which f~cilit~tPs mating within the bores of the fixation peg mPmher and ~e 2 collet member.

4 In use, the fixation peg is positionP~ over a securement cavity and the eYp~n~ion elemPnt of the collet is disposed within the cavity. The expansion pin is then inserted within 6 the collet and the fixation peg to positively engage the peg and to expand the expandable 7 elemPnt~ of the collet such that they engage the walls of the cavity to secure the peg to the 8 prosth One or more augmentation blocks, of desired shapes and sizes, may be provided to fit l l between the first surface of the femoral component and the fixation pegs such that the 12 ~ gmPnt~tion block and the fixation pegs are together selectively affixed to the articulation 13 component. This system is particularly useful with cruciate substitllting femoral components 14 of knee joint prosthesis to provide added prosthesis stability.
16 In one embodiment the collet members are separate from the fixation pegs and the 17 eYp~n~ion pins engage both the collet and the fixation peg. In another embodiment the collet 18 mlombPrs are integral with and are formed on a distal end of the fixation pegs.

BRIEF DESCRIPTION OF THE DRAWINGS
21 Figure 1 is an isometric view of a knee joint prosthesis femoral col"ponent having a 22 modular stabilizing peg according to the present invention.
23 Figure 2A is a sectional view of the prosthe~i~ shown in Figure 1.
24 Figure 2B is a sectional view of the prosthe~is shown in Figure 1, illustrating the collet in a non-eYp~n~e~i co~ ition.
26 Figure 3 is a s~ction~l view of an ~ltPrn~tive prosthesis syseem, similar to that shown 27 in Figure 2A, but also including an augment~tiol- block.
28 Figure 4 is an exploded view of the prosthe~is shown in Figure 3.
29 Figure SA is a bottom view of a fixation peg useful with the prosth~ shown in Figure 1.
31 Figure SB is a sectional view of the collet shown in Figure SA.

I~UI~ER, Mc~:LENNEN ~ FISH. LLP
Tcl~e: ~61~ aoo F~iile: (6l J) 973-97~8 CA 0222~322 1997-12-19 Figure 6 is a top view of an ~llgm~nt~tion block of the type shown in Figure 4.
2 Figure 7 is an isometric view of an alternative modular ~ugment~tion and stabilizing 3 prosthecic system according to the present invention.
4 Figure 8A is a sectiol-~l view of the prosth~sic system of Figure 7.
Figure 8B is a sectional view of the prosth~sis system of Figure 7, illustrating the 6 collet in a non-e~p~ndçd cQn-iiSiom 7 Figure 9 is an exploded view of the prosthçci.c system of Figure 8B.
8 Figure 10A is a side view of the collet useful with the invention shown in Figure 7.
9 Figure 10B is a bottom view of the collet shown in Figure 10A.
Figure 10C is a sectional view of the collet shown in Figure 10A.
11 Figure l l is a side view of an expansion pin useful with the invention shown in 12 Figure 7.

The invention provides a joint prosthesis system 10 that offers enhanced intraoperative 16 versatility and modularity to improve femoral cGI~Iponent fi~tion and stability. The 17 invention is particularly applicable to cruciate substituting femoral components. For 18 illustrative purposes, the present invention is described with reference to an anticipated use 19 with a femoral co",ponent of a knee joint prosthecic. It is understood, however, that the invention can be adapted for use with a variety of joint prostheses. A particular advantage of 21 the present invention, which lends itself to use with various types of joint prosthesec, is the 22 ease with which fixation elementc and ~lgmPnt~tion pieces can be secured to a prosthesis.

24 As noted above, and as illustrated in Figures 1 through 6, the invention is particularly applicable to use with cruciate substituting femoral col--ponents. Figure 1 illustrates the 26 prosth~.sic system 10 of the invention in which a cruciate substituting femoral cGI~ponent 12 27 has an intercondylar notch 13, ~nterior and posterior portions 14, 16 and condyles 18, 20.
28 Each condyle includes an inferior articul~tion surface 22 and an opposed supérior bone 29 eng~ging surface 24. Figures 2A and 2B illlictr~te that the lateral distal flat 30 inr.ludes a securement cavity 32, and a similar cavitj ~not shown) is formed in the medial distal flat 28.

~UI~ER, McCLENNEN ~ FISH. IlJ' -rc~e: (61n 439-~00 rK~imilc: (6ln 97}9741 5 Fixation pegs 26 are selectively mounted within securement cavities 32 upon the medial and 2 lateral distal flats 28, 30 of superior surface 24, on opposite sides of intercondylar notch 13.

4 As illustrated in Figures 2A through 4, the system includes modular, selectively mountable fixation pegs 26. The fixation pegs 26 are substantially elongate members having 6 a peg body 33 with proximal and distal ends 34, 36. Preferably, a bore 52 eYten~s between 7 the proximal and distal ends of the fixation peg. Further, an expansion collet 38 is integral 8 with and is disposed distally of the distal end 36 of peg body 33. The system also int~ludes a 9 supply of eYp~ncion pins 40 having a proximal end 42, including external threads 44, and a distal, collet exr~n-ling end 46. Although the illustrated expansion pins include external 11 threads, it is understood that alternative surface features may exist on the expansion pins, 12 instead of threads, to perrnit positive engagement with the bore 52 of the fixation peg 26.

14 As noted above, the modnl~rity of the fixation pegs is an i~ ollant feature of the invention. Since fixation pegs need not be inct~llçd on all cruciate c~crifi~ing femoral 16 cGponents, the modularity offered by this invention gives the a.ll~eon the option to attach 17 fixation pegs to a prosthçci~ to be implanted.

19 Fixation pegs can be selectively mounted upon a prosthesis by simply placing the 20 exr~ncion collet end 38 of peg 26 within one of the s~~ent cavities. Thefe~lel, set 21 screw 40 is inserted within the ~lu~ al end 34 of the fixation peg and into bore 52. In an 22 emboaiment in which a threaded exr~n~ion pin is utili7f~d, the eYp~nsion pin is advanced 23 within the bore and eYt~rn~l threads on the screw mate with complPment~ry threads in the 24 bore. Further adv~ncement of the expansion pin causes the distal end of the ~Yp~n~ion pin to expand collet 38 so that the collet interferingly engages the walls of cavity 32 to secure the 26 fiY~tion peg to the prosthe~

28 The overall length of the fLxation pegs can vary depending upon the anatomical 29 requirements of a patient, the ~imPncionS of prostheses col--ponents, and whether the peg is to be used with or without any augm~nt~tion block. Generally, the overall length ûf the peg 31 can be frorn 2 to 60 millimeters, and more preferably from about 10 to 50 millimeters. The l~'U~, ~ ~1 . . e~ FISH, llP
Te~: (617)~39-2000 F~imi~: (617) g73-9748 -6-length of the collet end 38 of peg 26 should be such that it is slightly less than the depth of 2 cavity 32, allowing distal base 48 of peg 26 to rest on superior surface 24 of the femoral 3 col~lponent. The length of the collet is generally about 2 mm to 20 mm. Further, the 4 fixation peg preferably decreases in di~m~t~r from distal end 36 to proximal end 34. The S di~metpr at base 48 is about 4 mm to 10 mm, while the diameter ac proximal end 34 is about 6 2 mm to 8 mm. External surface features S0, such as axial grooves, axial ribs, annular 7 grooves or annular ribs, can be formed in the external surface of the peg to enhance fiY~tion 8 of the prostlle~i~ within bone.

Figure SA is a bottom view of fixation pin 26, illustrating the eYp~n~ion collet 38.
11 The collet 38 is preferably slotted, with two perpendicular slots 35 formed therein that 12 separate the collet into four substantially triangular shaped wedges 37. Although not 13 illustrated, an interior portion of collet 38 is angled inwardly to enable the intern~l geometry 14 of the collet to cooperate with the distal end 46 of expansion pin 40 to cause wedges 37 to expand and to sepaldle from one another when the distal end of the expansion pin is forced 16 into engagement with the corresponding intçrn~l surfaces of the wedges.

18 It is understood that it is not neces~ry that the collet have two slots disposed therein 19 to form four subst~nti~lly triangular wedges 37. It will be readily ap~arent to one having ordinary skill in the art that the collet may have one or more slots disposed therein.

22 Figure SB is a sectional view of peg 26, showing a bore 52 that eYtrnd~ the length of 23 the body 33 of peg 26. Bore 52 preferably includes internal threads 54 that are able to mate 24 with complement~ry external threads 44 of expansion pin 40. Although bore 52 includes threads 54 in an illustrated embodim~nt, it is understood that other structures may be formed-26 within bore 52 to f~rilit~te engagement with complern~nt~ry external structures on eYp~n~ion 27 pin 40.

29 FYp~n~ion pins 40 are of a length sufficient to enable them to fit within peg 26 to the extent n~e~ry to expand collet 38. The expansion pin inrludes a proxiln~l end 42, having 31 extern~l threads 44 that are mateable with int~ l threads 54 of bore S,, and a distal end 46.

;UI~ER~ McCLENNEN h FIS4 llP
(61n 43~
lc (61n ~9748 7 The proximal end of the expansion pin may include a structure or mech~nicm, such as a hex 2 head 45, that coo~ldtes with an inct~ tion tool to enable it to be advanced into bore 52.
3 Distal end 46 preferably has a geometry that will cause exp~ncion of the distal stem of the 4 collet. The distal end 46 of pin 40 can include a radius tip 56, a dogged end (not shown) or S similar geollleLI;cs.

7 Although the exr~nsion pins 40 are describe~ as being threaded members that 8 threadingly engages intern~l threads 54 within bore 52, it is understood that other h~tioll 9 structures and techniques may be utilized to ~in~ the exp~ncion pins within the bore 52 and to expand collet 38. As noted above, internal structures may be formed within bore 52 11 that accommodate complemP-nt~ry surface features on expansion pin 40 to enable me~h~nica 12 engagement of the coll,ponents.

14 In another embodiment, illust~tPA in Figures 3 and 4, the modular system 10 of the invention may also include an allgmPnt~tion block 58 that is secured on superior surface 24 16 of femoral col,lponent 12, between the femoral co"l~onent 12 and the fixation peg 26.
17 ~ gment~tion blocks of various designs are well known in the art and are commonly used to 18 f~ilit~te proper seating of prosthPcic co"~ponents within a patient when insllffiçiPnt bony 19 mass exists in certain areas of the patient's bone upon which the prosth~Psis is to be mounted.
21 The aug~nPnt~tion block 58 illustr~ted in Figures 3, 4 an~ 6 is adapted to mount on 22 the superior surface 24, on either the medial or lateral distal flats 28, 30 of a femoral 23 co,nponent 12 of an artificial knee joint. Block 58 may be adapted for use in either left or 24 right side knee prostheses. An augmPnting block suitable for a left side prosthPcic can mount upon either the medial or lateral inferior con(~ylar surfaces, and an augmPnting block suitable 26 for a right side prosthesis can mount upon either the medial or lateral inferior condylar 27 sllrf~çes of the prosthe-~i~. As illustrated, block 58 has a first (distal) surface 60 and a 28 second (proximal) surface 62 and an aperture 61 extPntling between--these surf~c~s. A
29 recessed area 63 may surround the aperture 61. The area of the proximal surface 62 preferable is greater than the area of the distal ~urface 60 in order for the block to conform 31 to the geometry of the inner condylar surface of a knee joint femoral co"~l,onent.

~Ui~, MeClENNEN ~IL FISH. IlP -r.kphn.: ~617)439~
r~ ~b: 16l7)973-97ql 2 ~u~mpnting block 58 has two opposed, canted surf~es 64, 66 that can be either 3 posterior or ~ntPrior s~ ~s ~epPntling upon whether the ~llgmPnt~tion block is mounted on 4 the medial or lateral side, or on a left or right side prosthesis. Preferably, surf~ces 64, 66 S are canted as such that each surface slopes inwardly from the l,io~ al surface 62 to the 6 distal surface 60 as shown in Figures 4 and 6. The angle of the canted surfaces 64, 66 can 7 vary as will be appreciated by those having ordinary skill in the art. Preferably, the angle of 8 surf~cçs 64, 66 coll~s~onds to the angle of the anterior and posterior chamfers 68, 70 of the 9 femoral co~ll~nent to enable proper seating of the augmPnting block 58 within a femoral co.llpol-ent.

12 Augmenting block 58 further includes surfaces 72, 74 which correspond to either 13 medial or lateral facing surfaces, depending upon whether the ~ugme-l~tiQn block 58 is used 14 on the lateral or medial side of a prosthesis, or in a left or right side prosthesi~. Side surfaces 72, 74 preferably are subst~nti~lly vertical and extend at a right angle to the plane of 16 the proximal or distal surfaces 62, 60.

18 As illustrated in Figure 3 augm~nt~tit)n block 58 is adapted to mount on a prosthe~i~
19 component, such as the medial or lateral distal flats 28, 30, such that the distal surface 60 of block 58 contacts the superior surface 24 of femoral component 12. The distal end of 21 expansion collet 38 of fixation peg 26 preferably extends through aperture 61 and beyond the 22 distal surface 60 of block 58 by a ~ tance sufficient to enable collet 38 to fit within a 23 securc~lle~t cavity 32 disposed in a surface of the femoral component to be ~lgm~ntçd The 24 frictional andJor m~xh~nic~l engagement of the collet with cavity 32 enables the ~ Alion system to be secured to an a~propliate surface of the femoral component. The ~ t~nce by 26 which distal stem extends beyond the distal surface of the block can vary depen-ling upon the 27 lequil~lllents of a given application. Typically, this distance is about 0.155 to 0.175 inch 28 and most preferably about 0.165 inch.- One of ordinary sl~ll in the art will apl)l~iate that 29 the length of the distal s~em should not be so great that its distal end contacts the bottom of cavity 32.

~IT~R, McCLeNNEN ~ FISU, LLP
(61n~
~-~: (61n sn 9748 _9_ As noted above, an expansion pin 40 çontrols the eyp~ncion (and, optionally, the2 contraction) of the distal stem of collet 58. In one embodiment, where the eyp~ncion pin is a 3 threaded screw, tightPning of the screw expands the distal stem of the collet, while loosening 4 screw enables a once expanded collet to contract. When collet 38 is in a non-expanded condition there is little or no frictional andlor m~rh~nical engagement be~ween collet 38 and 6 securement cavity 32; the ~ mPnt~tion block can be freely removed and inserted into 7 s~u.clllent cavity 32 in this condition. Conversely, when the collet 38 is in the eYr~nded 8 condition, as shown in Figure 3, suffiçiPnt frictional and/or mech~nic~l engagement exists 9 between the collet 38 and the walls of the s~;ulcl-~ent cavity 32 to enable the ~--gment~tion block and the fixation peg to be held firmly on the prosthecic component.

12 As noted above, the invention described above can be used with or without 13 ~ ment~tion blocks. Further, because the fixation pegs are not perm~nçntly installed upon 14 the prosthlo-cis~ they can be selectively affixed to the prosthesis at the option of the s.lr~eon.
16 The ~~im~ncic)ns of the various co~"ponents of system 10 can vary. It is il"~-~lt, 17 however, that the relative tlimenciol~C of the components be such that collet 38, in the non-18 eYr~nd~ condition shown in Figure 2B, be able to fit within the scculelllent cavity (and, 19 where applicable through ~ugmet-t~tion block ape-lu-c 61) without excess friction or inle.relc~nce. Upon expansion of the collet, as shown in Figure 2A, the outer walls of 21 wedges 37 should firmly engage the inner walls of se.;~lre,nent cavity 32 to prevent 22 dislodgement or movement of the fLlcation peg. The preferred tensile ~tta~hment force of the 23 collet to the prosthesis should be in the range of about 50 to 500 kg. The rlimencion~ of 24 these colllpollents will vary depen~ing upon the requirements of a given application, and one of ordin~y skill in the art can readily deterrnine the a~p~up-iate relative dimensions.
26 Generally, the ~ meter of the collet in the non-eYp~nded condition is al,pro~imateiy 0.240 to 27 0.260 inch, and preferably it is about 0.250 inch. The ~i~met~r of the collet in the eYr~nd~
28 condition preferably is about 0.010 to 0.020 inch greater than the rli~meter in the non-29 eYr~nded condition. The di~met~r of the secu-c-~-ent cavity 32 is suffi~i~nt to yiel~ a secure ~0 in~lÇ~;rence fit between the collet and the cavity when the collet is expanded. rreferably, the 3] cavity has a ~ mPter of about 0.26 inch + 0.10 inch. The depth of the mou:1tin~g cavity ~ M~lENt~N h FJ5~L llP
,l.pl~ ~61n439-~
61n g~9748 CA 0222~322 1997-12-19 can vary, as will be understood by those of ordinaly skill in the art, but preferably the depth 2 is about 0.18 to 0.26 inch. As noted above, the collet 38 should not engage the bottom wall 3 of cavity 32.
Another embodiment, illustrated in Figures 7 through 11, provides an ~ltern~tive6 fixation technique for the modular prosthesis system 100 of the invention. In this 7 embodiment, the collet is not integral with the fixation peg, but the same modular fiY~tion 8 options exist. That is, fiy~tion pegs can be mounted directly upon the superior surface of a 9 joint prothesis, without an ~ugm~nt~tion block, or an ~llgm~nt~tion block can be disposed between the fiY~tion peg and the prosthesis.

12 Figure 7 illustrates a cruciate substituting femoral cou~onent 102 that includes an 13 intercondylar notch 104, an inferior surface 106 having condyles 108, 110 and a superior 14 bone eng~ing surface 112 having la~eral and medial distal flats. For purposes of illustration, the prosthesis depicted in Figure 7 is ~s~med to be a left knee femoral 16 component having ~nterior 118 and posterior 120 surfaces. Further, Figure 7 illusLl~tes an 17 ~llgm~nt~tion block 122 and fixation peg 124 mounted on lateral distal flat 116. It is 18 understood that the fixation peg 124 can be mounted directly upon the medial or lateral distal 19 flats without an ~lgm~nt~tion block.
21 Figures 8A through 11 illustrate the various components of system 100. These 22 components include fixation pegs 124, one or more optional augment~tion blocks 122, one or 23 more collets 126 and one or more ~p~r.~;cn pins 128. Further, as noted above with respect 24 to Figures 1 through 6, the femoral colll~nent 102 includes at least one sec~le-llent cavity 130. Preferably, one securelllent cavity is mounted on each of the medial and lateral distal 26 flats of the femoral component.

28 Fixation peg 124 is an elongate member having proximal and distal ends 132, 134.
29 The distal end 134 of the peg includes a base 136 which surrounds an opening 138 of an int~rn~l bore 140 which extends within the peg. Tnt~rn~l threads 141 (or other int~rn~l 31 fixation structures) preferably are present within the bore and may extend the entire length of Ul'rER. McCUENNEN ~ F1511, llP
61~) 439~
(617) 97}9?48 CA 0222~322 1997-12-19 the bore or, ~ltçrn~tively, threads be present only in sçle~te~ regions of the bore. Although 2 the proximal end 132 of peg 126 is shown to include a closed top 142, the top may 3 ~ltern~tively be open. The base 136 abuts the proximal surface 144 of ~llgmPnt~tiorl block 4 122. Alternatively, if no ~ugmPnt~tiQn block is used, base 136 will abut the superior surface S 112 of femoral co~,-~nent 102.

7 Fixation peg 124 is of a construction similar to that described above with respect to 8 Figures 1 through 6, except that it does not include an integral distal collet. Fixation peg 9 124 thus may include external surface features 146 and may have a larger ~ P~ at distal end 134 than at proximal end 132.

12 As shown in Figures 9 and 11, expansion pin 128 is an elongate member that has 13 distal 148 and proximal 150 ends. The expansion pin is intended to expand collet 128, by 14 action of its distal end 148, while its proximal end 150 engages both a proximal end 152 of the collet and the fixation peg. Although various structures can enable the PYp~nci~n pin to 16 expand the collet and to engage the collet and the fixation peg, a p~efel.ed embodiment is 17 described below.

19 The proximal end 150 of the expansion pin 128 preferably incl~ldes eytprn~l threads 154. Preferably, the threads 154 extend over a ~list~nce of about 2 to 20 mm. The distal 21 end 148 of the collet is non-threaded and preferably has a diameter that is slightly less than 22 the ~i~metPr of proximal end 150. The distal tip 153 of expansion pin 128 has a geometry 23 that will cause eYr~n~ion of the collet, such as a radius tip point 155, a dogged end (not 24 shown), or similar ~eomçtniP~s. Preferably, the head 151 of the eYp~nsion pin 128 is a hex head.

27 Collet 126 has a proximal end of 152, including collar 156 and a distal, collet 28 eYr~n~ing end 158. The collar 156 can mount within a recessed area surrounding cavity 29 130. ~lt~Prn~tively, if an augmPnt~tion block 122 is used, the collar 156 will be seated in a recessed area 159 surroul~ding aperture 160 on a proximal surface 144 of block 122. The 31 collar 156 and the recessed area can be-of virtually any corresponding shapes including, for ~ER, McCl~NNEN ~ FISH. IlJ' ~ 617) 439 ~imile: (617) 913~

example, circular and D-shaped. A D-shaped collar, which includes a flat end 169, or 2 another irregularly shaped collar, can be useful to prevent any unwanted rotation of the collet 3 within the securement cavity 130 or aperture 160.

As illustrated in Figure 10C, collet 126 preferably includes internal threads 164 6 within proximal region 152. These threads are complementary to threads 154 of expansion 7 pin 128 such that a lower (distal) portion of threads 154 mate with threads 164 to m~int~in 8 the expansion pin in a desired position with the collet. The distal end of the collet is 9 preferably slotted and is of a structure as described above for collet 38 illustrated in Figures 1 through 6.

12 As noted above, Figures 7 through 9 illustrate an augmentation block 122 used with 13 system 100. It is understood that the use of ~llgmçntation block 122 is optional. If the 14 ~ugmPnt~tion block 122 is not to be used, the fixation peg 124 is mounted directly to the superior surface 112 of femoral component 102.

17 The ~imPncions of the various co~ponPnt~ described above can vary depPn-ling upon 18 the size and type of prostheses which they are used. One of ordilla~y skill in the art can 19 readily de~ ,ine the apl)ropl;ate tlimPnsions.
21 System 100 can be utilized as follows. If a surgeon determines that it is desirable to 22 mount fixation pegs 124 upon prosthesis 102, set screw 128 is advanced within collet, 23 without eYp~n-ling the collet, until threads 154 and 164 mate. The collet is then position 2~ within se~ r~l"ent cavity 130 and the set screw is tightPne~ until the collet eYr~n~s to the extent that it m~int~in~ good purchase upon the inner walls of the securement cavity !30.
26 The torque needed to effect such expansion generally is about 20 to 40 inch-pounds, and 27 more preferably about 30 inch-pounds. Thereafter, the fixation peg is threaded upon 28 expansion pin 128 such that threads 154 mate with internal threads 141 of fixation peg 124.
29 Prcferably the length of the extPrn~l threads 154 that remain exposed once the expansion pin is deployed to expand the collet is about 6 to 12 mm.

-,TrER, McCLl:~lNEN ~ FISIL llP
~: (610 ~39~
(617) ~9748 -13-A similar procedure is utilized for an embodiment in which an ~ugm~nt~tion block2 122 is to be used. In such embodiment collet 126 may be predisposed within apellule 160 of 3 ~ mPnt~tion block 122. Once the ~lgm~nt~tion block is plo~lly positioned on femor~l 4 col,lyonent 102, ~Yp~n~ion pin 128 is advanced within the collet c~l-cin~ the collet to expand and to secure the allgment~tion block to the femoral co-l~ponent. Next, the fixation peg can 6 be threaded upon the proximal end of the expansion pin.

8 The illustrated embodiments of system 100 include int~rn~l threads within the collet 9 126 and fixation peg 124, and ext~rn~l threads on eYp~n~ion pin 128. It is understood that other structures can be used, instead of threads, to f~ilit~te joinder of the set screw to both 11 the collet and the fixation peg.

13 The prostheses col"ponents of the invention can be made from a variety of 14 biocompatible materials having high strenglh, durability and re~ictance to wear debris.
Fx~mI)les of such materials include metal alloys such as a cobalt chromium alloys, tit~nillm 16 alloys, st~inl~ss steel, ceramics and other m~teri~l$, includin~ polymers, that are well known 17 for use in the m~mlf~ture of implantable bone prostheses. A ~refe.led m~tPri~l for the 18 prostheses colnponents is a cobalt chromium alloy such as ASTM F-75.

The collet components preferably are made from a m~lle~hle metal or metal alloy to 21 reduce the risk of tensile failure as a result of collet expansion. Where such m~t~ri~l~ are 22 used to form a threaded component, the m~teri~l~ should be able to deform (but not fail) 23 when subjected to a torque of about 20 to 65 in-lbs, and more preferably about 25-35 in-lbs.
24 A ~lefel,cd m~J~ri~l is a wrought cobalt chromium alloy such as ASTM F-90.
26 The set screw preferably is made from a metal or metal alloy that has a higher 27 modulus and a greater hardness than does the collet. Such properties ensure that the collet 28 (and not the expansion pin) will deform when subjected to torque and/or axial load. A
29 yrerell~d m~teri~l from which the expansion pin can be manufactured is wrought cobalt chlull~ m alloy such as ASTM F-1537 (formerly known zs AST~ F-799).

TrER, McCLENNEN IL FISH, LLP
.q~ (61n~3~
~imik: ~6lns7}n~s The tensile securement values of the fixation pegs and/or ~u~ment~tion blocks to the 2 femoral components preferably are in the range of about 50 to 500 kg. This secure fit 3 ensures that the ~lrol,-.ance of the prosthesis CGIl-pollent is not co,l.~romised. Moreover, 4 the modular fixation peg and ~-lgm~nt~tion system of the invention can be easily ~ttac~ed within a femoral component of a knee joint prosthesis.
7 The foregoing description of the illustrative embodiment of the invention is presented 8 to indicate the range of constructions to which the invention applies. Variations in the 9 physical archi~tllre and dim~n~ions of the invention will be ayp~r~nt to those having ordinary skill in the art based upon the disclosure herein, and such variations are considered 11 to be within the scope of the invention in which patient rights are asserted, as set forth in the 12 claims appended hereto. All publications and references cited herein are expressly 13 incol~,ol~ted herein by reference in their entirety.

cp~: (61J) ~39-2000 6 1 7) 97}9748 - 1 5 -

Claims

1. A modular knee joint prosthesis system, comprising a femoral component having a superior bone engaging surface and an inferior articulation surface, the superior surface including at least one securement cavity, each of the securement cavities being defined by a sidewall and a bottom wall;

at least one substantially elongate fixation peg member, each fixation peg member being selectively matable, via a collet member, with one of the securement cavities of the superior surface of the femoral component, each fixation peg member having a distal end, a proximal bone engaging end and an internal bore;

at least one collet member matable with a distal end of the fixation peg member, each collet member having an expandable distal end adapted to fit within and selectively engage the sidewall of one of the securement cavities and a proximal end including an internal bore; and an expansion pin element having a proximal end including an external structure matable with the internal bore of the fixation peg member and the internal bore of the collet member, and a distal end capable of selectively expanding the collet such that the collet engages the sidewalls of the securement cavity.

2. The system of claim 1 wherein the internal bore of the fixation peg member includes an internally threaded portion.

3. The system of claim 2 wherein the internal bore of the collet member includesan internally threaded portion.

4. The system of claim 3 wherein the external structure of the expansion pin element comprises an external threaded region.

5. The system of claim 1 wherein the collet member is integral with the elongatefixation pegs and forms a distal end thereof.

6. The system of claim 4 wherein the collet member is separate from the filtration peg member, and wherein the collet member includes an expandable distal end formed by two or more expandable wedge-like members each separated by a slot; and a collar at a proximal end thereof.

7. The system of claim 6 wherein the collar of the collet member seats upon the securement cavity with the distal end of the collet member extending therein such that the expansion pin element is threadingly engaged within the internally threaded region of the axial bore of the collet member and the internally threaded region of the fixation peg member.

8. The system of claim 7 further comprising at least one augmentation block having first and second opposed surfaces and an aperture extending therebetween, the first surface being mountable upon a portion of the superior surface of the femoral component and the aperture being dimensioned to receive the distal end of the collet member such that the augmentation block and the fixation peg member are together selectively matable with the articulation component.

9. The system of claim 8 wherein the articulation component is a femoral component of a knee joint prosthesis.

10. The system of claim 8 wherein in the femoral component is a cruciate substituting femoral component including an intercondylar notch formed on the superior surface thereof.

11. The system of claim 10 wherein one of the securement cavities is formed on each of a medial distal flat and a lateral distal flat of the femoral component.

12. The system of claim 4 wherein the fixation pegs members have a length in therange of 2 to 60 mm.

13. The system of claim 6 wherein the fixation peg members decrease in diameter from an end adjacent one of the superior surface of the augmentation block and the superior surface of the articulation component to the proximal end thereof.

14. The system of claim 13 wherein the fixation peg members include external surface features.

15. The system of claim 14 wherein the external surface features are selected from the group consisting of axial ribs, axial grooves, annular ribs and annular grooves.

16. The system of claim 4 wherein the collet member has two or more wedge-shaped structures at a distal end thereof.

17. The system of claim 13 wherein the bore formed in the fixation peg member extends from an opening in the distal end to a closed proximal end.

18. A modular joint prosthesis system, comprising:
an articulation component having a first, bone engaging surface and a second, articulation surface, the first surface including at least one securement cavity, each of the securement cavities being defined by a sidewall and a bottom wall;

at least one substantially elongate fixation peg member, each fixation peg member being selectively matable within one of the securement cavities on the first surface of the articulation component and each fixation peg member having a distal end including an expandable collet that is engagable with the circular sidewall of one of the securement cavities, a proximal bone engaging end and an axial bore extending between the distal and proximal ends of the fixation peg member; and an expansion pin element having a proximal end including at least one external structure matable within the axial bore of the fixation peg member, the expansion pin element further including a distal end capable of selectively expanding the collet such that the collet engages the sidewalls of the securement cavity.

19. The system of claim 18 wherein the axial bore of the fixation peg member includes an internally threaded region.

20. The system of claim 19 wherein the external structure of the expansion pin element comprises a threaded region.

21. The system of claim 20 further comprising at least one augmentation block having first and second opposed surfaces and an aperture extending therebetween, the first surface of the augmentation block being mountable upon the first surface of the articulation component, and the aperture being dimensioned to receive expandable collet portion of the fixation peg member such that the augmentation block and the fixation peg are together selectively matable with the augmentation component.

22. The system of claim 21 wherein the articulation component is a femoral component of a knee joint prosthesis.

23. The system of claim 21 wherein the femoral component is a cruciate substituting femoral component including an intercondylar notch formed on the first surface thereof.

24. The system of claim 22 wherein a securement cavity is formed on each of the medial distal flat and the lateral distal flat of the femoral component.

25. The system of claim 20 wherein each fixation peg member has a length in the range of 2 to 60 mm.

26. The system of claim 25 wherein each fixation peg member decreases in diameter from the distal to the proximal end thereof.

27. The system of claim 25 wherein each fixation peg member includes external surface features.

28. The system of claim 26 wherein the external surface features are selected from the group consisting of axial ribs, axial grooves, annular ribs and annular grooves.

29. The system of claim 20 wherein the collet has two or more wedge-shaped structures at a distal end thereof.

30. A modular joint prosthesis system, comprising:
an articulation component having a first, bone engaging surface and a second, articulation surface and at least one securement cavity formed in the first surface, wherein each of the securement cavities is defined by a sidewall and a bottom wall;
at least one substantially elongate fixation peg member, each fixation peg member being selectively matable with one of the securement cavities on the first surface of the articulation component, each fixation peg member having a distal end, a proximal bone engaging end and an axial bore formed therein, the axial bore including internal threads;
a collet member having a distal end including two or more expandable wedge elements that are able to selectively engage the sidewalls of one of the securement cavities and a bore extending therethrough, at least a proximal portion of the bore including an internally threaded portion; and an expansion pin element having a distal end able to expand the distal end of the collet member and a proximal end including external threads, the expansion pin element being insertable within the axial bore of the fixation peg and the collet member such that the external threads of the expansion pin element mate with the internal threads of the fixation peg and the internally threaded portion of the collet member.

31. The system of claim 30 wherein the collet member is integral with the distalend of the fixation peg member,

32. The system of claim 30 further comprising an augmentation block having a first surface mountable upon a portion of the first surface of the articulation component, a second opposed surface and an aperture extending between the first and second surfaces.