Note: Descriptions are shown in the official language in which they were submitted.
13U(~:llA
ZMOll9 ~ Y~ THETIC l P~ RAPPED POROUS SURFAC8
¦ BACKGROUND OF THE INVENTION
The present invention relates to a prosthetic implant
device and more particularly to xuch implants including porous
surfaces thereon. This invention is particularly suitable for
use as a femoral component for ~ hip prosthesis, although is not
limited thereto.
¦ Heretofore, various types of porous surfaces have been
incorporated into prosthetic implants. Such porous implants are
often implanted without the use of any type of bone cement
material so that the porous surface will be in direct contact
with the bone surface. After a period of time, bony ingrowth
occurs in and around the porous sur~ace to ~ologically affix or
~urther secure the implant in th~ bono. Alternatively, an
implant ha~ing a porous surface ~a~ b~ implanted with bone
cement, such that the penetration of the bone ce~ent into the
porous sur~ace of the prosthesis will enhance the ~i~ation oi.'
the prosthesis. ~ ~ ~
The following U.S. paten~s disclos~ prosthe~ic i~pl~nts
which include various types of porous suraces
: ~ '
U.S. Patent 3,906,550 to Rostoker et al. discloses a porous
~iber metal structure adapted for attachment to a prosthesis.
The ~iber metal ~aterial is molded directly into the desired
precise sh~pe using dies and punches.
~: :
U.S. Patent 4,479,271 to Bolesky e~ al. discloses a
p~osthes includlne porous surfaces ~hlch are al50 either
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molded and compressed dlrectly lnto shape or compressed and cut ¦
directly into shape.
Il I
IU.S. Patent 4,536,894 to Galante et al. discloses a ¦
: pros~hesis including porous surfaces in which the porous ¦
surfaces are porous pads which are compressed and cut directly
to the desired shape and then adhered to substantially ~lat
surfaces.
I
U.S. Patent 4,570,271 to Sump discloses a prosthesis with a
porous surface in which the porous coating is preformed directly
into the desired shape which corresponds to the preselec~ed
surface of the prosthesis. The preform porous coating is then
overlaid onto the preselected surface, compressed, and heated to
adhere the preform to the prosthesis. The preform may be
produced by conventional multi-layer knitting, braiding,
winding, weaving, or other continuous wire processes.
U.S. Patent 4 9 58g,883 to Kenna discloses a prosthesis
including a porous surface in which the porous coating is
compr~sed of spherical particles which appear ~o have been
directly bonded to the prosthesis stem.
: ~ l U.S. Patent 4,636,219 to Pra~t e~ al. discloses ia
prosthesis including a porous sur~ace comprised of a layered
metal mesh structure. The mesh may be bonded to a thin
su~strate (on the ord~r o 0~010 to 0.012 inch) whlch thin
substrate can ~hen be cut or ormed and applied to the body of a
prosthesis on a flat surface as in Fig. 3 of Pratt et al. or
contoured into spec~fic shapes by processes such as creep
~formine.
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U.S. Patent 4,660,755 to Farling et al. discloses a method
for constructing a surgical implant in which a porous layer is
~bonded to a substrate in the absence of a furnace, the bonding
~¦occurring via an electrode.
U.K. Patent Application GB2059267A to Ducheyne discloses a
type of porous metal wire mesh suitable for use on a prosthesis,
U.K. Paten~ Application GB2142~30A to Brown et al.
discloses a prosthetic implant having a porous surface provided
by a perforated micro-contoured sheet.
U.~. Patent Application GB2153233A to Lee et al. disclsses
a prosthetic implant which utilizes wed~es to wedge between the
bone cavity wall and the prostbesis stem in which the wedges may
Include a porous surface.
European Patent Application ~P0178650A2 to Ducheyne
¦discloses a porous flexible metal fiber material for
implantation in con~unction with a prosthesis in which one or
more l~yers of:the porous sheet material are pressed aga.inst the
bone~ surface wlth a 18yer of bone eement then betwe~n the
: implant and the po~ous sheet material.
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OBJECTS AND SU~MARY OF THE IN ~NTION
::
: : A pr~nciple ob~ect of this invention is to provide a
:prosthetic implant which lncludes a porous pad separate from ~he
prosthesis stem which ls adapt~d for wrapping around the stem
¦~for attachmen thereto.
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Another object of the invention is to provide a prosthetic
implant which includes a porous pad separate from the fixation
~surface base portion such that the porous pad has a first
preliminary precontoured shape. The porous pad is adapted for
wrapping about the fixation surÇace base portion in a second and
final shape corr~sponding to the shape of the fixation surface
¦base portion about which it is wrapped.
A further objec~ of the invention is ~o provide such a
¦prosthetic implant in which the pad is wrapped about at least
two adjaccnt sides.
A still further object of the invention is to provide a
process for wrapping a porous pad about a prosthesis stem in
wbich the pad has a first preliminary, substantially flat
precontoured shape which is subsequen~ly wrapped about the stem
into a second and final shape for attachment ~o the s~em.
The present invention accomplishes the above o~ec~s and as
such provides a prosthetic implant which includes a porous pad
which is pre~iminarily formed into a first shape and then
wrapped and/or formed about the stem of ~he implant to confor~
to the shape of the implant in a second and final shape.~ The
pad ls then adhered to the stem. The inven~ion also provides a
process for prepaFlng the porous pad and for convenientl~
wrapping th~ pad about the stem.
BRIEF DESCRIPTION OF TH~ DRAWINGS
These fea~ures and obj~cts of the in~ention, as well as
others, will become apparent to those skilled in the art by
; ¦¦referring to the accompanying drawings:
.
Fig. 1 is a perspective view of a femoral component for a
lhip prosthesis according to the present invention;
¦I Fig. 2 is an anterior side elevational view thereof;
¦ Fig. 3 is a lateral side elevational view thereof;
Fig. 4 is a medial side elevational view ~hereof;
Fig. S is a cross-sectional view taken along lines 5-5 of
Pi~. 2;
Fig. 6 is a cross-sectional view taken along lines 6-6 of
Fig. 2;
I Fig. 7 is a side view of a femoral component according to
¦the present invention located in a forming fixture with the
fixture shown in 8 cross-sectional view taken along lines 7-7 of
~ ~ig. ~c;
Fig. 8 is a cross-sectional view of the forming fixture
taken along lines 8-8 of Fig. 7;
Figs. ~a, 8b, and 8c are cross-sectional views taken along
lines 8-8 of Flg. 7 of the forming ~ixture illustrating various
jaws in act~vated posi~ions about the femoral component stem;
Fig. 9 is a top view o a pressed and prebonded shee~ of
porous material;
: Fig. 10 is a top view of~ the sheet of Fig. 9 illustrating a
; I cut;out portion;
~: Fig. 11 is a top view of the porous pad formed from the cut
: out of Fig. 10;
: ~ ~ Fig. 12 i5 a side view of~a femoral compvnen~ ac~ording to
the prssent lnvention located in a ~onding ixture with the
; : ~ixture shown in a cross-sectional view taken along lines 12-12
. of ~ie- 13;
Fig. 13 is a cross-sec~ional view o~ the bonding fixture
~a~en along lines 13-13 of Fig. 12;
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,;
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j Fig. 14 is an anterior side elevational view of an
alternate embodiment of a femoral component,
Fig. lS is posterior side view of the component of Fig. 14;
I and
¦ Fig. 16 is an alternate embodiment for a porous p~d to be
¦ used in conjunction with the component of Fig. 14.
; DETAIL~D DESCRIPTION OF TH~ NY~NTIGN
Figs. 1-13 illustrate a particularly advanta~eous
embodiment of a prosthetic implant according to the present
invention. The invention will be described with reference to a
femoral component 10 of a hip prosthesis and is particularly
sui~able as such. Howcver, it is understood that the principles
of the invention may be suitable for other implants having
elongated fixation stems. In addition, it is noted for
ref~rence that the partlcular femoral component 10 described
herein is desi~ned for i~plantation in a right femur, while a
: corresponding f~moral component (not shown) for implantation ina l~ft femur woul~d be a ~irror i~age of tbe:~femoral;~component 10
: shown or the ri~ht femur.
1 ;~ The f~moral component lO~of Figs. 1 6 includes a distal end
: ~ a~nd a proximal :en~ 14. As ~is well known, the ~emoral
componen~ 10 is intended to ~it within th* intramedullary canal
~ ~ ~ : of a femur (not shown) such~ tha~ ths proxi~al end ex~ends
i~ outwardly from the intramedullary canal o~ tha f0mur to
cooperate with an acotabulum or acetabular prosthetlo mcmber via
a ball or the like carricd at the proximal end 14. A dlstal
~portion 16 y includo a plurallty of grooves 18 extending ¦
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longitudinally. A proximal portion 24 includes a porous surface¦
or pad ~6 encircling the femoral component 10. The distal~
portion 16 and the proximal portion 24 comprise the stem portion
20 of the femoral component 10. A neck 28 extends from the !
proximal portion 24 a~d is adapted to carry a ball 30 sho~n in
phantom lines in Fig. 1. An aperture 31 adjacent the neck 28¦
accommodates a tool for removing the femoral component 10 romj
the intramedullary cana~ should removal be necessary. Thel
porous psd 26 is desi~ned to extend outwardly from the proximal¦
portion 24 albeit a small extension of about O.Smm psst the¦
adjacent smoo~h surface of the proximal portion 24.
,,
Figs. 2, 3, and 4 illustrate a chamfer 32 on the anterior
side of the femoral component which may be included to avoid
lmpingement o~ the distal end 12 into th0 bo~e surrounding the
intramedullary canal at ~hat loca~ion.
As shown in Figs. 1-4, ~he proximal portion 24 includes a
lateral side 34, a posterior slde 3~ a medial side 38, ~nd an
ant~rior side 40. A porous pad 26, as shown ln the embodiment
of Figs. 1-6, is oircumferentiallr wrapped around the`~-~proximal
~portion 24 of the ~tem portion 20. The pad 26 may be formed of
an~ suitable porous material that is adapted to be preliminarily
pressed into a first shRpe and th~n subsequently wrapped about
the stem portion 20 into a s~cond shape con~orming to the shaple
of the stem portion 20. One suoh suit~ble material is the fiber
metal structure disclosed in U~S. Patent 3,906,S50 to Rostoker
and ~alante, although it is noted tha~ the Rostoker et al.
patent t~aches that thc fi~er metal ~aterial ls molded directly
into the desired shap~, ratber than providing a first
preliminary shape which is then subsequently wr~pped or for~ed
;WQ~3~3
~about a pros~hetic implant into the second and final shape in
¦¦accordance with the present invention. It is understood that
¦any suitable porous material, particularly fibrous (wire-type)
¦Iporous structures which are adaptable to be practiced in
¦laccordance with the present invention, may be utilized. The
material for the porous pad may be titanium wire having a
diameter of 0.010 inches t and the material for the femoral
component may also be titanium. Again it is understood that any
suit~ble materials may be utili~ed.
The shape of the porous pad 26 may have any desirable
configuration, although preferably the pad is first formed in or
pressed into a substantially flat sheet 126 (see Figs. 9-11).
~The outer boundary of the pad 26 mar have any suitable contour.
¦The porous pad 26 is separate from the stem portion 20. The psd
26 is adapted for wrapping around the stem portion 20 for
~ttachment thereto. The porous pad 26 has a first preliminarr
precontoured shape as shown i~ Fig. 11 and is then subsequentlr
wrapped and/or formed about the stem portion 20 for attachment
thereto in a second and final shape corresponding to the shape~
of the s~em portion 20 as shown ln Figs. 1-4. The porous pad 26
is wrapped around at least~two eo three adjacent sides, althoug~i
preferabl~ is wrapped around all four ~sidss 34, 36, 38, ~nd 40
to~ form a continuous porous surface circumferentially about the
stem portion 20.
:
The porous material, such as a kinked titanium fiber metal,
is prass formed into D sheet 126 of porous material. The sheet
: 126 may have any desired thickness or dimensions. The
di~ensions of the sh~et 126 may be adapted to cut out ~ single
~pad 26 havi 8 a desired outer boundarr or adapted to cut out
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¦multiple pads 26 from a sin~le sheet. The sheet 126 is
prebonded in a vacuum furnace by holding the sheet for a
suita~le length of time at a temperature sufficient to create
metallurgical bonds at the points of contact of the fibers of
the porous material within the sheet 126. A porous pad 26
having the desired outer contour ls then cut from the sheet
leaving a correspondin~ cut out 226 in the sheet 126.
Prebonding ~he fiber metal sheet prior to cutting it creates
mechanical integrity in the sheet 126 so that the fiber material
is more easily formable and holds its shape better.
The porous pad ~6, shown in Fig. 11 which is subsequently
applied to the femoral component 10 of Figs. 1-4, lncludes a
medial pad side 1~8 to correspond to the medial stem side 38,
posterior and anterior pad sides 136 and 140 each extending from
or adjacent to the medial pad side 138 and adapted to correspond
to the posterior and anterior s~em sides 36 and 40,
respectively, and first and second tabs 120 and 122 extendin~
~rom the posterior and anterior sides, respecti~ely. The two
tabs together comprise the lateral pad sid~ 13d which will
oorrespond to the lateral stem side 34 of the emoral component
10. The pad 26 may be asymmet~i~ as shown with the pos~erior
porous pad surface 136 having greater surface area than the
~n~erior porous pad surface 140 ~nd with ~he medial pad surface
138 being longer than the lateral pad surface 134. However, ~he
pad 26 could readily be made symmetrically, if desired, as any
appropriate shspe may be utilized for the pad 26.
The pad 26 is then ready to be wrapped about the stem
psrtion 20. The proximal portion ~4 of the s~em portion 20
includes a recess 74 (see Fig. ~) having a shape corresponding
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to the pad 26 and adapted to receive the pad 26 for subsequent ¦
attachment thereto. The pads 26 can be shaped to conform to any
desirable and suitable implant stem or fixation surface ,
configuration. The proximal portion 24 of the stem portion 20 ~
of the femoral component shown has an asymmetric noncircular !
cross-section as shown in Figs. S and 6.
.
The process for wrapping the porous pad 26 may be
accomplished by placing the femoral component 10 (without pad
26) in a forming fixture $0 as shown in Figs. 7 and 8. The
fixture 60 has a plurality of forming jaws 61, 6~, 63, and 64.
The forming jaws are each operated by corresponding rod 161,
162, 163, and 164, respectively, which operatively connects the
jaws to cylinders 261, 262, 263, and 264, respectively. The
cylinders 261, 262, 263, and 264 may be air operated cyllnders
or hydraulic cylinders or any other suitable activation
mechanism. The ~aws, rods, and cylinders may be made of tool
ste~l, or any other suitable material strong enough to form tbe
porous pad 26 about ths femoral component 10.
The neck 28 o~ the femoral component 10 is seated in a
cylindrical bushing 66 within base pla~e 68 of fixture 60 to
hold the femoral component 10 in place. A sliding locating pin
69 may be ~placed ~hrough the aperture 31 to keep the femoral
component 10 from rotating while the form~ng is taking place.
The bushing 66 may suitably be made rom a nonmetallic material
such as delrin so as not to scra~ch ~he neck ~. Th~ base plate
I may be made of aluminum or s~eel. Other suitable means of
holding the emoral component 10 s~curely in the forming fix~ure
60 could also be utili~ed.
~.~0~
\ l
¦ The jaws 61, 62, b3, and 64 are each in a retrac~ed
¦~ position about the femoral component 10. The precut
substantially flat porous pad 26 is placed in position between
¦ the jaws and the implant 10 with the ~edial pad portion 138
¦ aligned with the corresponding medial side 38 of the s~em
~por~ion 20. The jaws, which have interfac~ng surfaces
corresponding to the desired pad and stem configuration, are
,then activated in a predetermined sequence to form the pad 26
~about the implant conforming the pad 26 to the shape of the
implant lQ as shown in Figs. 8a, ~b, and 8c. In Fig. 8a the
first forming jaw 61 is activated from its retracted position to
a position in which the first jaw 61 is pressed up against the~
medial porous pad surface 138 which is thus pressed against the
corresponding medial side 38 of the stem portion 20 shaping and
¦locating the respective portion of the pad ~6 thereto. The
first jaw 61 is then held in its activated position agains~ the
stem portion 20.
Alternatively, the medial porous pad surface 138 c~uld be
preformed to the shape of th~ medlal side 38 by utilizing a
correspondingly shaped separate forming dye (not shown) for just
the medial side (rather than forming this ~edial side UsiDg the
saquential fixture ~0). The separate dye would include a
substantially U-shaped depression such as that shown in the
cross-sact1on of ~aw 61 in Fig. 8a and a corresponding U-shap~d
projecti~n corresponding to the outer contour of the medial side
of the emor~1 component; which when brought together with the
: pad 26 ln ~etween would preform the pad 26 into $he
substantlally U-shaped conf~guration, such as tSat ach~avsd
using th~ first ~aw bl of the s~qu~ntial orming fixture 60~ If
such a separate dye is used, the pad 26 having the preformed
".. ~ . ~;~UD~311' ''
(U-shaped) medial pad surface 138 would then ~e plac~d in
position in the forming fixture 60 between the jaws and the
implant 10 with the preformed medial pad 138 ali~ned with the
medial side 38 of the stem portion 20. The jaw 61 would be
activated to hold the pad 26 having the preformed medial pad
surface against the stem portion 20. The remaining se~uential
activation of the jaws would then continue.
The second and third jaws 62 and 63 may ~e then ac~iv~ted
simultaneously as shown in Fig. 8b to press the posterior and
anterior porous pad surfaces 136 and 140, respectively, against
the posterior and anterior sides 36 and 40 of the stem portion
thus shaping the respective portions of the pad thereto.
Jaws 61, 62, and 63 are then held in this activated position
against the stem portion 20.
The fourth ~aw 64 is then activated as shown in Fig. 8c to
press the first and second tabs 120 and 122 of the lateral
porous pad surface 134 against the lateral side 34 of the stem
portion 20 thus shaping the respective portions o~ the pad
thereto. The tabs 120 and 1~2 mate together on the later~l side
~ ,~
34 to form a flush interface 27, thus providing a continuous
circumferential porous surface connecting the ~nterior, medial,
posterior, and lateral sides.
The forming ~aws are ~en released from their ac$ivated
positions, and thus retracted sway from the stem portion 20.
The ~moral component lO wi~h the conformed pad 26 surrounding
it is remov~d from th~ forming fixture 60. The femoral
component lO is then placed in ~n appropriate bonding fixtur~ 80
such as ln Figs. 12-13 in which the porous pad is held s~curely
l;~UOl~
ln place against the s~em por~ion ~0. The pad 26 is positioned~
securely in the recess 74 which corresponds to the wrapped shape
of the pad 26. The porous pad 26 is then bonded to the stem
¦~portion 20 to securely att~ch i~ thereto. Th~ bonding may bel
achieved by diffusion bonding the pad to the stem portion ~ !
holding the pad securely thereagainst at a sufficient
temperature for a sufficient length of ~ime to achieve secure
bonding. However, it is understood that other bonding processes¦
such as sintering or other suitable bonding methods may be
utilized.
Although any appropriate bonding fixture or holding
mechanism may be used for bonding the pad 26 to the stem portion,
20, Figs. 12 and 13 illustrate such a suitable fixture 80. The
fixture 80 includes a support frame 86 with a pluralit~ of
holding or bonding blocks or jaws 81, 82, 83, and 84 which
surround thc porous pad 26 on the proximal portion 24 and which
conform ~o the shape of tbe stem portion 20 about whicb they are
positioned. The bonding blocks which hold the pad 26 in place
against the stem portion 20 are suitabl~ made of a carbon
material, as is the rame 86. The bonting blocks 81, ~2,~ 8~,
and 84 are placed under sufficient pressure evenlr holding the
pad 26 agains~ the stem por~ion 20 ~ia scr~ws 88.
Alternatively, rakher than orming the substantially 1at
first preliminarily shaped pad 26 about the stem portion 20 ln~o
its second and final contoured shape, the pad 26 can be formed
about a man~rel (not shown) whlch has a shape which corresponds
to the portion of the i~plAnt to which th~ pad i~ to be
~ttached. This formln~ about a ~andrel can b~ done with a
fixture 60 such as that described aboYe used or ~orming the
l~V~l~
,
subs~antlally flat or medially preformed pad 26 about the ¦
implant itself. Then the formed pad 26 which has been shaped i
about the m~ndrel is removed from the mandrel and placed about
the femoral component 10. The pad 26 can then be securely
bonded to the stem portion 20 as described above.
An alternate embodiment for a femoral component 400 is
shown in Figs. 14-16 in which the porous pad 426 is adapted to
fit in recess 474. Figs. 14 and 15 show the component 400
without the porous pad 426 thereabout. The pad 426 is adap~ed
to be wrapped about t1lree ad~acent sides including the lateral,
medial, and anterior sides 36, 38~ and 40 to form a continuous
porous surface interconnecting these three sides. Since the pad
426 does not completely surround all sides of the implant, the
pad 426 may be conveniently formed from its substantially flat
first preliminary shape (as shown in Fig. 16) to its second and
final contoured shape which corresponds to the shape of the
recess 474 in the stom portion 20 either by using a
correspondingly shaped (substantially U-shaped for tbe
embodi~ent shown in Figs. 14-16) s~parate sin~le forming dye
(not shown), or R orming fixture 60 wi~h multiple sequ~atially
operated forming jaws such as previously described. The formed
pad 426 can then be bonde~ to th~ s~em por~ion 20 in a similar
manner as previously describ~d for tbe p~d 2S which
circumferentially surrounds the stem portion.
The prosthetic implant of the present in~ntion provides an
implant ha~ing a wrapped porous pad and a method o wrapping
such pad about a prosthetic stem portion. T~ pr~sent invention
proYides for a substantially flat pad having a predetermined
outer ~oundary to be su~sequently wrapped about a prosthesis
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~31~0~11
stem to conform to the shape of the stem and to be attached ¦
thereto. While this invention has been described and
exemplified in terms of particularly advantageous embodiments,
those skilled in the art can appreciate that modifications can
be made without departing from the spirit and scope of this
lnvention
