Note: Descriptions are shown in the official language in which they were submitted.
WO 93/02641 PCT/US91/05358
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PROSTHETIC JOINT SYSTEM FOR BONE REPLACEMENT
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention. relates to prosthetic joints and,
in particular, to a prosthetic joint system for use
when bone replacement is required.
2. Description of the Prior Art
Various prostheti c joints are known which
include means for replacing bone which the patient
I5 has lost as a result of disease, trauma, or'
bio-mechanical degeneration caused by, for example, a
previous joint implant.
Figure I shows a two piece prosthesis 14 of this
type which includes a stem 16 and a bone replacement
portion l8 which can be a bone graft or a shaped part
composed of a plastic material, such as ultra high
molecular weight polyethylene (UHMWPE). See "Link
Endo-Model Total Femur Replacement", Link America,
Inc., East Hanover, New Jersey, 1989, and "The
Leinbach Horizontal Platform Femoral Component", Allo
Pro Corporation, St. Petersburg, Florida, 1982.
Figure 2 shows another prior art construction of
this type which comprises a one piece metal
prosthesis l0 which includes a proximal portion 12
~ which, .serves as a replacement for bone. Examples of
prostheses of this general type include those sold by
Ho~amedica under the product designations "Universal
32mm Proximal Femur Total Hip Components with
Polished Loops", "Muller Type 32mm Proximal Femur",
"Harris Calcar Replacement 32mm Total Hip System",
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and "Averett Modified Head Neck 32mm Tatal Hip
System", and those sold by DePuy under the product
designation "1031-30/44 Femoral Upper Third".
' Although these prostheses have benefited many
patients, problems have remained with their use. In
particular, with reference to the prostheses of the
type shown in Figure 2, custom prostheses are often
needed and even when customized, these prostheses may
not fit the patient particularly well, especially in
~10 connection with achieving a tight fit, between the
prosthesis and the patient.'s.bone..~These prostheses
provide the surgeon with only one choice of
replacement at the time of surgery which limits the
ability of the surgeon to respond to specific needs
or problems ascertained after the surgery has begun.
Also, custom prostheses take a substantial amount of
time to fabricate and are expensive.
With reference to the prostheses of the type
shown in Figure d, these can provide the surgeon with
some degree of choice at the time of surgery.
Typically, a family of stems and a corresponding
family of replacement portions 18 are provided to the
surgeon. Also, in some cases, parts of the
replacement portion can be cut away at the time of
surgery to accommodate different amounts of bone
loss. See the Allo Pro system, supra. However,
these prostheses still suffer from problems in
achieving an optimum interface between the stem 16
and the patient's bone. In particular, because of
3d the ' Mechanical configuration of the prosthesis,
porous coating of the stem to achieve long term
fixation through bone ingrowth is inadvisable since
it may reduce the endurance~strength of the stem.
Femoral prostheses which include sleeves for
engagement with bone are also known in the art. See,
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for example, Noiles U.S. Patent No. 4,846,839 and Noiles U.S.
Patent No. 4,790,852. Such prostheses have not included
separate bona replacement elements of the type shown in Figure
1 but in some cases have included an integral bone replacement
portion of the type shown in Figure 2.
SUMMARY OF THE INVENTION
According to a first aspect of the invention there is
provided a prosthesis for implantation in a bone which has an
end for receiving the prosthesis and a medullary canal, said
prosthesis comprising= a) a stem comprising an elongated body
having a joint motion surface at one end and an outside surface
extending away from said joint motion surface, said outside
surface including a tapered portion, said tapered portion being
comically shaped with a circular cross section
b) an elongated sleeve for fixation within an elongated cavity
created in the bone at the end of the bone for receiving the
sleeve, said sleeve including an outer surface for engagement
with said cavity in the bone and an internal taper for locking
engagement with the tapered portion, said internal taper being
comically shaped with a circular cross sections c) an elongated
bone replacement element having a longitudinal lengthT and d)
means for attaching the bone replacement element to the stem at
a location between the joint motion surface and the sleeve,
wherein (i) the elongated sleeve is spaced from the joint
motion surface by a distance which is greater than the
longitudinal length of the bone replacement element and (ii)
the stem extends beyond the elongated sleeve by an amount
sufficient for stabilizing engagement with the bone s medullary
canal.
According to a second aspect of the invention there is
provided a prosthesis for implantation in a bona which has an
end for receiving the prosthesis, said prosthesis comprising:
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a) a stem comprising an elongated body having a joint motion
surface at one and and an outside surface extending away from
said joint motion surface, said outside surface including a
tapered portion, said tapered portion being comically shaped
with a circular cross sections b) an elongated sleeve for
fixation within an elongated cavity created in the bona at the
end of the bone for receiving the sleeve, said sleeve including
an outer surface for engagement with said cavity in the bone
and an internal taper for locking engagement with the tapered
portion, said internal taper being comically shaded with a
circular cross sections c) a bone replacement elements and d)
means for attaching the bone replacement element to the stem at
a location between the joint motion surface and the sleeve,
said means comprising an internal taper for locking engagement
with the tapered portion, said internal taper being comically
shaped with a circular cross section and being formed on an
inside surface of the bone replacement element.
According to a further aspect of the invention there is
provided a prosthesis for implantation in a bona which has an
end for receiving the prosthesis, said prosthesis comprising:
a) a stem comprising an elongated body having a joint motion
surface at one and and an outside surface extending away from
said joint motion surface, said outside surface including a
first tapered portion, said first tapered portion being
comically shaped with a circular cross sections b) an elongated
sleeve for fixation within an elongated cavity created in the
bona at the and of the bona for receiving the sleeve, said
sleeve including an outer surface for engagement with said
cavity in the bone and an internal taper for locking engagement
with the first tapered portion, said internal taper being
comically shaped with a circular cross sections c) a bone
replacement elements and d) means for attaching the bone
replacement element to the stem at a location between the joint
motion surface and the sleeve, wherein the outside surface of
the stem includes a second tapered portion, said second tapered
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portion being located between the joint motion surface and the
first tapered portion, the means for attaching comprises an
internal taper for locking engagement with said second tapered
portion, and said second tapered portion and said internal
taper are each comically shaped with a circular cross section.
According to a further aspect of the invention there is
provided a prosthesis for implantation in a bone which has an
and for receiving the prosthesis, said prosthesis comprising:
a) a stem comprising an elongated body having a joint motion
surface at one end and an outside surface extending away from
said joint motion surface, said outside surface including a
tapered portion, said tapered portion being comically shaped
with a circular cross sections b) an elongated sleeve for
fixation within an elongated cavity created in the bone at the
end of the bone for receiving the sleeve, said sleeve including
an outer surface for engagement with said cavity in the bona
and an internal taper for locking engagement with the tapered
portion, said internal taper being comically shaped with a
circular cross sections c) a bone replacement elements and d)
means for attaching the bone replacement element to the stem at
a location between the joint motion surface and the sleeve,
wherein the outside surface of the stem includes flutes for
engagement with the bona replacement element.
According to a further aspect of the invention there is
provided a prosthesis for implantation in a bone which has an
end for receiving the prosthesis, said prosthesis comprising:
a) a stem comprising an elongated body having a joint motion
surface at one end and an outside surface extending away from
said joint motion surface, said outside surface including a
first tapered portion, said first tapered portion being
comically shaped with a circular cross sections b) an elongated
sleeve for fixation within an elongated cavity created in the
bona at the end of the bone for receiving the sleeve, said
sleeve including an outer surface for engagement with said
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cavity in the bona and an internal taper for locking engagement
with the first tapered portion, said internal taper being
conically shaped with a circular cross sections c) a bona
replacement elements and d) means for attaching the bone
replacement element to the stem at a location between the joint
motion sLrface and the sleeve, said means comprising a second
sleeve affixed to the bone replacement element and attached to
the stem, said second sleeve being a separate element from both
said bone replacement element and said elongated sleeve.
According to a further aspect of the invention there is
provided a prosthesis for implantation in a bone, said
prosthesis comprising two prosthetic elements and a stem for
attachment by locking tapers to the two prosthetic elements,
said stem comprising an elongated body having a joint motion
surface at one end and an outside surface extending away from
said joint motion surface, said outside surface including an
elongated tapered portion which has a sufficient length to
permit attachment of the two prosthetic elements and which is
conically shaped with a circular cross section for locking
engagement with the two prosthetic elements, each of the two
prosthetic elements having an internal taper which is conically
shaped with a circular cross section.
According to still yet a further aspect of the invention
there is provided a prosthesis for implantation in a bone, said
prosthesis comprising a first prosthetic element, a second
prosthetic element, and a stem for attachment by locking tapers
to the first and second prosthetic elements, said stem
comprising an elongated body having a joint motion surface at
one and and an outside surface extending away from said joint
motion surface, said outside surface including first and second
elongated tapered portions each of which is conically shaped
with a circular cross section, and first and second tapered
portions being separated from one another along the length of
the body, said first tapered portion being for locking
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engagement with the first prosthetic element and said second
tapered portion being for locking engagement with the second
prosthetic element, each of said two prosthetic elements having
an internal taper which is conically shaped with a circular
cross section.
The accompanying drawings, which are incorporated in and
constitute part of the specification, illustrate the preferred
embodiments of the invention, and together with the
description, serve to explain the principles of the invention.
It is to be understood, of course, that both the drawings and
the description are explanatory only and are not restrictive of
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side view of a prior art femoral prosthesis
which includes a stem and a bona replacement portion.
Figure 2 is a side view of a prior art femoral prosthesis
whose proximal portion has been configured to replace lost
bona.
Figure 3 is a side view, partially in cross-section, of a
femoral prosthesis constructed in accordance with the invention
for use with a bone graft.
Figure 4 is a side view, partially in cross-section, of a
femoral prosthesis constructed in accordance with the invention
having a stem with two tapered portions, one for engagement
with a bone replacement element and the other for engagement
with a sleeve which is implanted in the patient s femur.
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Figure 5 is a side view, partially in
cross-section, of a femoral prosthesis constructed ir.
accordance with the invention having a bone
replacement element which is clamped to the
prosthesis' stem and a sleeve which engages a tapered
portion of the stem.
Figure 6 is a side view, partially in
cross-section, of a femoral prosthesis constructed in
accordance with the invention having a stem with an
elongated tapered portion for engagement with both a
bone replacement element and with a sleeve which is
implanted in the_patient's femur.
Figure 7 is an expanded view of the outside
surface of the sleeves of Figures 3-6 illustrating
the use of steps or terraces on the outside surface.
Figure 8 is a cross-sectional view along lines
8-8 in Figure 5 illustrating representative means for
attaching a bone replacement element to the
prosthesis' stem.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference now to the drawings, wherein like
reference characters designate Iike or corresponding
parts throughout the several views, there is shown in
Figure 3 a femoral prosthesis 20 constructed in
accordance with the invention which incorporates bone
graft 22.
Prosthesis 20 includes elongated stem 13 which
has ball 24 at one end which serves as a joint motion
surface. The outside surface of stem 13 includes a
~0 ' first tapered portion 26 and a second tapered portion
28. Between the tapered portions are flutes 30.
Stern 13 also includes a second set of flutes 38.
Prothesis 20 further includes first sleeve 32,
second sleeve 34, and trochanter washer 40 which is
attached to stem 13 by screw 42. First sleeve 32 is
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implanted in the patent s femur 36 and provides strong
mechanical fixation of the prosthesis to the proximal end of
the femur. Additional fixation of the prosthesis to the femur
is provided by flutes 38 which help stabilize the distal end of
the prosthesis with regard to rotation about the prosthesis
longitudinal axis.
In practice, a series (family) of sleeves 32 of different
sizes and/or configurations is provided to the surgeon so that
he or she can choose the sleeve which provides the best union
with whatever portion of the femur remains for implantation.
Similarly, a family of stems 13 is also provided to the surgeon
so that again optimizing choices can be made at the time of
implantation.
As shown in Figure 7, sleeve 32 preferably has a stepped
outside surface 48 of the type described in Noiles, U.S. Patent
No. 4,846,839. As also described in that patent, if porous
coating is used, such coating is preferably applied to just the
sleeve and not to the stem. In this way, an opportunity for
bone ingrowth is provided without putting the overall
structural integrity of the prosthesis at risk.
As shown in Figure 4, if desired, sleeve 32 can include a
collar 44 for engagement with the exposed, proximal end of the
femur. Similarly, as shown in Figure 5, the sleeve can include
a protruding portion 46 constructed in accordance With Noiles,
U.S. Patent No. 4,790,852. It is to be understood, of course,
that the illustrated sleeves can be used with any of the
prostheses of Figures 4-6. Whatever construction is used for
the sleeve s outside surface, its inner
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surface includes a tapered portion 50 for locking
engagement with first tapered portion 26 of stem 13.
The prosthesis. of Figure 3 includes second
sleeve 34 for engagement with bone graft 22.
Depending upon the size and shape of the bone graft,
sleeve 34 car. include various of the features
discussed above with regard to sleeve 32. Thus, it
can include a collar 44, a protruding portion 46, a
stepped outside surface 48, and, if desired, a porous
~10 , coating or other coating to enhance adhesion when
cement is used to affix the graft. As with the first
sleeve, whatever configuration is ehosen for the
outside surface of the second sleeve, its inner
surface includes a tapered portion 52 for loc~;ing
engagement with second tapered portion 28 of stem 13.
In addition to sleeve 34, flutes 30 and
trochanter washer 40 also.help affix bone graft 22 to
stem 13. The sleeve serves as the primary source of
mechanical fixation between the graft and the stem.
The flutes provide further fixation by helping
prevent rotation. of the graft about the stem as
tor4ue is applied to the graft by the patient's
tendons and muscles. Trochanter washer aids irt the
attachment of those tendons and muscles to the
prosthesis and also helps stabilize and strengthen
the greater trochanter portion of the graft. The
combination of these three . fixation mechanisms
provides excellent stabilization of bone grafts
including. long bone grafts.
30' Figure 4 shows an alternate embodiment 60
wherein a bone replacement element 54 composed of
metal is used in place of bone graft 22. For this
embodiment, as well ~s those shown in Figures 5 and
6, a series of bone replacements is preferably
provided to the surgeon so that a selection of the
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most appropriate element can be made at the time of
surgery.
As in Figure 3, stem 13 includes a first tapered
portion 26 which mates with first sleeve 32. The
stem also includes second tapered portion 28 which
mates and locks with taper 56 formed on the inside
surface of element 54._ As shown in Figure 4, the
outside surface of element 54 can include a porous
coating 58 to aid in the ixitegration and bonding of
the prosthesis to the patient's tissues. Although
not: shown in Figure 4, element 54 can also include a
muscie/tendon attachment plate 62 of the type shown
in Figure 5.
Figure 6 shows a variation of the prosthesis of
Figure 4 wherein the stem's first tapered portion 26
has been elongated so that it mates with the internal
tapers of both sleeve 32 and bone replacement element
54. Such a construction can also be used with the
bone graft embodiment of Figure 3 for applications in
which flutes 30 are not required.
Figure 5 shows a further variation of the
invention employing a bone' replacement element 64
composed of plastic. Instead of locking tapers, this
embodiment uses opposing flanges 66 and locking
screws 68 to attach element 64 to stem 13. Such an
attachment system can also be used with the metal
bone replacement elements of Figures 4 and 6~. Also,
for- a ceramic bone replacement element, the
attachment system of Figure 5 can be combined with a
taped ,lock of the type shown in Figures 4 and 6 to
produce a strong attachment.
The prostheses of the invention can be implanted
using a variety of techniques known in the art.
Trial components are typically used to select a set
of components best suited to the patient's needs.
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The patient's femur is resected as necessary and a
straight hole for -receiving stem 13 is reamed into
the femur's medullary canal. A conical cavity is
then formed in the end of the femur for receiving
sleeve 32. For sleeves including a protruding
portion 46, a side cavity for that portion can be
formed in the end of the femur using a cutting tool
of the type disclosed in U.S. Patent No. 4,790,852,
the relevant portions of which are incorporated
herein by reference.
The bone replacement element is affixed to stem
13 prior to its implantation. In.the case of a metal
element of the type shown in Figures 4 anc 6,
fixation can be achieved by placing the element in an
appropriate fixture and then applying a sharp impact
force to stem 13 to lock the complimentary tapers on
the element and the stem together. For a plastic
element of the type shown in Figure 5, the element is
slid over the stem and then tightened into place
using screws 68.
In the case of a bone graft, a cavity for the
stem and sleeve 34 can be formed in the graft using
techniques similar to those used to prepare the
patient's femur. Sleeve 34 is then implanted in the
graft, with or without cement, and the stem and
sleeve are united by applying a sharp impact force to
the stem to lock together the complimentary tapers.
After the bone replacement element has been
locked onto the stem, the prosthesis is inserted into
30~ the prepared femur by passing the stem through sleeve
32 into the straight cavity formed in the medullary
canal. As the stem moves into its final position,
f lutes 38 cut channels into the canal . As the last
step in the implantation, the stem and sleeve 32 are
lacked together by applying a sharp impact force to
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the stem to engage tapered surface 26 with tapered
' surface 50.
The tapered surfaces) formed on stem 13 can
have a variety of inclinations. For example, taper
angles of 6° total included angle for surfaces 26 and
50 have been found to work successfully. Similar
taper angles can be'used for surfaces 28 and mating
surfaces 52 and 56.. Other taper angles which can be
used a.re in the range of from about 3° to about 10°.
For components made of a titanium alloy, preferred
surfaces for the interlocking tapers are a smooth
machined surface on the stem an-d a recrvstallized
surface ~o.n the sleeve's internal taper as occurs
during sintering of a porous coating.
The components of the prosthesis can be
constructed from surgically implantable materials
such as chemically pure titanium or a titanium alloy
containing 6°d aluminum and 4x vanadium for stem 13,
bone replacement element 54, and sleeves 32 and 34
(see ASTM Specification No. F136) and ultra high
molecular weight polyethylene for element 64. When
porous coating is used, the coating car. comprise
small spheres or particles o~ the same material as
that used to form the underlying component.
~25 Although specific embodiments of the invention
have been described and illustrated, it is to be
understood that modifications can be made without
departing from the invention's spirit and scope. For
example, although the invention has been illustrated
in t~,e~ context of a femoral prosthesis, it is also
applicable to other artificial joints, such as,
shoulder and knee joints. A variety of other
modifications which do not depart from the scope and
spirit of the invention will be evident to persons of
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ordinary skill in the art from the disclosure herein.
The following claims are intended to cover the
specific embodiments set forth herein as well as such
modifications, variations, and equivalents.
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