U.S. patent application number 10/446069 was filed with the patent office on 2004-12-02 for hip implant with porous body.
Invention is credited to Lyren, Philip S..
Application Number | 20040243246 10/446069 |
Document ID | / |
Family ID | 33450976 |
Filed Date | 2004-12-02 |
United States Patent
Application |
20040243246 |
Kind Code |
A1 |
Lyren, Philip S. |
December 2, 2004 |
Hip implant with porous body
Abstract
A hip implant having two distinct bodies, a neck body and a bone
fixation body. The neck body is formed from a solid metal and has
an interface for connecting to a femoral ball. The bone fixation
body has an elongated shape and is formed as a porous structure
that is inserted into an intramedullary canal of a patient.
Inventors: |
Lyren, Philip S.; (Houston,
TX) |
Correspondence
Address: |
Attention: Philip S. Lyren
289 Woodland Ave.
Wadsworth
OH
44281
US
|
Family ID: |
33450976 |
Appl. No.: |
10/446069 |
Filed: |
May 27, 2003 |
Current U.S.
Class: |
623/22.11 |
Current CPC
Class: |
A61F 2002/30156
20130101; A61F 2002/30354 20130101; A61F 2002/30403 20130101; A61F
2002/365 20130101; B22F 7/04 20130101; A61F 2002/30011 20130101;
A61F 2/36 20130101; A61F 2002/30125 20130101; A61F 2002/30367
20130101; A61F 2002/30153 20130101; A61F 2002/30957 20130101; A61F
2002/30968 20130101; A61F 2002/3652 20130101; A61F 2002/3625
20130101; A61F 2002/3611 20130101; A61F 2230/0026 20130101; A61F
2002/30838 20130101; A61F 2002/30925 20130101; A61F 2002/3631
20130101; A61F 2002/30112 20130101; A61F 2002/3092 20130101; A61F
2/3609 20130101; A61F 2002/30906 20130101; A61F 2250/0024 20130101;
A61F 2310/00796 20130101; A61F 2/30767 20130101; A61F 2/3662
20130101; A61F 2002/2817 20130101; A61F 2002/30331 20130101; A61F
2220/0033 20130101; A61F 2230/0021 20130101; A61F 2310/00023
20130101; A61F 2/3607 20130101; A61F 2002/30154 20130101; A61F
2002/30677 20130101; A61F 2002/30332 20130101; A61F 2230/0004
20130101; A61F 2220/0025 20130101; A61F 2002/30158 20130101; A61F
2/3601 20130101; A61F 2002/30136 20130101; A61F 2230/0023 20130101;
A61F 2002/30604 20130101; A61F 2230/0063 20130101; A61F 2230/0019
20130101; A61F 2230/0076 20130101; A61F 2230/0008 20130101 |
Class at
Publication: |
623/022.11 |
International
Class: |
A61F 002/32 |
Claims
What is claimed is:
1. A hip implant, comprising: a neck body extending from a distal
end to a proximal end, formed of a biocompatible metal, and having
an interface at the proximal end that is adapted to connect to a
femoral ball; and a bone fixation body extending from a proximal
end to a distal end and formed of a completely porous structure
from the proximal to distal ends of the bone fixation body, the
proximal end of the bone fixation body connected to the distal end
of the neck body.
2. The hip implant of claim 1 wherein the bone fixation body is
entirely porous, extends below a resected end of a femur of a
patient, and is adapted to integrate with the femur of the patient;
and wherein the neck body is non-porous and extends above the
resected end of the femur of the patient.
3. The hip implant of claim 2 wherein the bone fixation body has
horizontal cross-sectional triangular shape.
4. The hip implant of claim 2 wherein the bone fixation body has
horizontal cross-sectional elliptical shape.
5. The hip implant of claim 2 wherein the bone fixation body has a
horizontal cross-sectional trapezoidal shape.
6. The hip implant of claim 2 wherein the neck body is formed of a
machined metal with a solid metallic structure and further
comprises a collar adapted to seat against the resected end of the
femur; and wherein the distal end of the neck body terminates at
the resected end of the femur.
7. The hip implant of claim 6 wherein the bone fixation body is
sintered, and the neck body is fused to the bone fixation body.
8. A hip implant, comprising: a neck body formed of a non-porous
biocompatible metal having a smooth outer surface and having a neck
adapted to connect to a hip component; and a bone fixation body
having one end connected to the neck body and being formed of a
completely porous structure throughout the entire bone fixation
body; wherein the bone fixation body extends into an intramedullary
canal of a femur of a patient, and wherein the neck body extends at
least partially above the intramedullary canal.
9. The hip implant of claim 8 wherein the bone fixation body has an
elongated generally tapering shape that extends from a proximal end
surface to a distal end surface, and wherein the proximal end
surface is adjacent an entrance to the intramedullary canal and the
distal end surface is embedded into the intramedullary canal.
10. The hip implant of claim 8 wherein the neck body has a male
protrusion that extends into the bone fixation body.
11. The hip implant of claim 10 wherein the protrusion has a shape
selected from the group consisting of cylindrical, rectangular, and
square.
12. The hip implant of claim 8 wherein neck body comprises a
non-porous bone-engaging section between the smooth outer surface
and bone fixation body.
13. The hip implant of claim 12 wherein the non-porous
bone-engaging section is a band having a rough surface texture.
14. The hip implant of claim 8 wherein the neck body is formed of
solid metal and the bone fixation body is formed of sintered metal
material.
15. The hip implant of claim 14 wherein the neck body and bone
fixation body are fused together.
16. A hip implant, comprising: a neck body formed of a non-porous
machined metal having a neck adapted to connect to a femoral ball;
and a bone fixation body having an elongated shape with one end
connected to the neck body and being formed of a completely porous
structure throughout the entire bone fixation body, wherein the
bone fixation body extends into an intramedullary canal of a
patient.
17. The hip implant of claim 16 wherein the bone fixation body has
a cross section formed entirely of the porous structure.
18. The hip implant of claim 17 wherein the neck body has a cross
section formed of a solid biocompatible metal.
19. The hip implant of claim 18 wherein the neck body has a
protrusion that extends into the bone fixation body.
20. The hip implant of claim 16 wherein the bone fixation body has
a tapering shape with undulations along an outer surface.
Description
FIELD OF THE INVENTION
[0001] The disclosure herein generally relates to hip implants for
osseointegration into bone and, more particularly, to hip implants
having a porous body.
BACKGROUND OF THE INVENTION
[0002] Much effort has been directed to integrating hip implants
into surrounding bone. Ideally, a hip implant would be placed into
the femur, and thereafter bone would readily grow into the surface
of the implant. To achieve this objective, many different surface
technologies have been applied to hip implants. In some instances,
the surface of the implant is roughened, grit-blasted,
plasma-sprayed, or microtextured. In other instances, the surface
is coated with a biological agent, such as hydroxylapatite (known
as HA). In all of these instances, the goal is the same: Produce a
surface on the hip implant into which surrounding bone will grow or
bond.
[0003] Porous coatings have also been applied to surfaces of hip
implants. These coatings are advantageous since bone will indeed
grow into a portion of the outer most surface of the implant.
Osseointegration, to a limited extent then, has been achieved with
porous coated surfaces. These surfaces though are far from ideal in
terms of accepting and encouraging bone growth into the body of the
implant.
[0004] As one disadvantage, porous surfaces are often thin coatings
applied to the metallic substrate of the implant. Bone surrounding
the implant can only grow into the thin coating itself. Bone cannot
grow through the coating and into the metallic substrate. The depth
of bone growth into the implant is limited to the depth of the
porous coating. Bone simply cannot grow completely through the
implant or deeply into the body of the implant.
[0005] It therefore would be desirable to have a hip implant that
offers optimum anchoring in bone with bone growth into a porous
body.
SUMMARY OF THE INVENTION
[0006] The present invention is directed toward a femoral hip
implant for integrating with surrounding bone. In one exemplary
embodiment, the implant includes two separate and distinct bodies,
a neck body and a bone fixation body. Together, these bodies form a
complete femoral hip implant.
[0007] The neck body is located at the proximal end of the implant
and includes an interface adapted to connect with a femoral ball
component. In an exemplary embodiment, this interface comprises an
elongated cylindrical shaft or neck adapted to matingly engage with
a cylindrical recess in the femoral ball component.
[0008] In one exemplary embodiment, the neck body is formed of a
solid metal piece, such as titanium, titanium alloy, or other
metals or alloys suitable for a hip prosthesis. The body is formed
from a machining process and has a base portion that may comprise a
collar. The neck extends outwardly away from the base portion.
[0009] The bone fixation body is formed of a porous metal, such as
titanium or other metals or alloys suitable for a hip prosthesis.
In one exemplary embodiment, the body is formed with a sintering
process, is completely porous, and does not include a metal
substrate. In cross section then, the body has a porous structure
with no solid metal substrate.
[0010] The neck body (formed of solid metal) and the bone fixation
body (formed of a completely porous structure) are permanently
connected together. When connected, the two bodies form a hip
implant. In one exemplary embodiment, these two bodies are
connected with a sintering process.
[0011] In one exemplary embodiment, the bone fixation body portion
of the hip implant is completely porous. This porous structure
extends entirely through the body of the implant along the region
where the implant engages femoral bone. As such, the depth of bone
growth into the implant is not restricted to a thin porous coating.
Instead, bone can grow deeply into the body of the implant or
completely into and even through the body of the implant. The
implant, then, can become fully integrated into surrounding bone
with the structure of bone dispersed throughout the body of the
implant.
[0012] In one exemplary embodiment, the geometric structure of the
porous body may be shaped and sized to emulate the shape and size
of natural bone surrounding the implant. Specifically, the porous
structure of the bone fixation body thus replicates the porous
structure of natural bone itself. The porous structure, thus,
readily accepts and encourages surrounding bone to grow into and
even through the body of the implant.
[0013] In one exemplary embodiment, the bone fixation body may be
doped with bone growth agents to enhance and stimulate bone growth.
These agents can be placed throughout the bone fixation body so
bone grows deeply into the implant or completely through the
implant. Bone growth, as such, is not restricted to the surface of
the implant.
[0014] As noted, the porous structure of the implant enables bone
to grow deeply into or completely through the implant itself.
Growth deep into the body of the implant provides an extremely
strong interface between the implant and surrounding natural bone.
As such, the likelihood that the implant will loosen is greatly
reduced. Further, the overall long-term acceptance of the implant
in the bone is increased. Further yet, the porous structure of the
bone fixation body reduces the overall weight of the hip
implant.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a side view of one embodiment of a hip implant of
an exemplary embodiment of the present invention.
[0016] FIG. 2 is a cross-sectional view of the implant of FIG. 1
embedded in the intramedullary canal of a femur.
[0017] FIG. 3 is a side view of another exemplary embodiment of a
hip implant of the present invention.
[0018] FIG. 4 is a cross-sectional view of FIG. 3 showing the hip
implant embedded in the intramedullary canal of a femur.
[0019] FIG. 5 is a side cross-sectional view of yet another
exemplary embodiment of a hip implant of the present invention.
[0020] FIG. 6 is a side view of yet another exemplary embodiment of
the present invention.
[0021] FIG. 7 is a top view of a horizontal cross section of an
exemplary embodiment of the present invention.
[0022] FIG. 8 is a top view of a horizontal cross section of
another exemplary embodiment of the present invention.
[0023] FIG. 9 is a top view of a horizontal cross section of yet
another exemplary embodiment of the present invention.
DETAILED DESCRIPTION
[0024] Referring to FIGS. 1 and 2, a hip implant 10 is shown
according to an exemplary embodiment of the invention. Implant 10
is preferably constructed of a biocompatible material such as
titanium, titanium alloy, or other metals or alloys suitable for a
hip prosthesis. Implant 10 comprises two primary components or
bodies, a neck body 14 and a bone fixation body 16.
[0025] The neck body 14 is located at the proximal end 18 of the
hip implant 10 and functions to connect the hip implant 10 to a
spherically shaped femoral ball 19 and acetabular component (not
shown). The neck body extends from a flat or planar distal end
surface 21 to a proximal end surface 23. Further, the neck body has
a base portion 20 that includes a collar 22 adapted to seat against
a resected or end portion of a femur. An interface is adapted to
connect the neck body to the femoral ball. A neck portion 24
extends outwardly from the base portion 20. This neck portion has a
short cylindrical configuration and has an end 26 with a slight
taper. This end 26 is adapted to be received in a correspondingly
shaped and sized cylindrical recess 30 in the femoral ball 19.
Together, end 26 and recess 30 form a Morse taper connection.
[0026] Preferably, the neck body 14 is formed of a biocompatible
metal, such as a solid metal piece of titanium, titanium alloy or
other metals or alloys suitable for a hip prosthesis. The body can
be machined to have a size and shape shown in the figures or other
sizes and shapes adapted for use as a hip implant.
[0027] The bone fixation body 16 has an elongated tapering shape
that extends from a flat or planar proximal end surface 40 to a
rounded distal end surface 42. The distal end surface 21 of neck
body 14 connects or fuses to the proximal end surface 40 of the
bone fixation body 16 at a junction 44.
[0028] In the exemplary embodiments of FIGS. 1 and 2, bone fixation
body 16 is formed from a porous metal, such as titanium. The body
has a completely porous structure that extends throughout the
entire body from the proximal end surface 40 to distal end surface
42. Specifically, as shown in FIG. 2, body 16 does not include a
solid metal substrate.
[0029] FIG. 2 shows the implant 10 embedded in a femur 50 of a
patient. In this embodiment, the implant is embedded into the
intramedullary canal 52 of the femur. The length of the bone
fixation body 16 extends along the region where the implant
contacts surrounding bone. As shown, the collar 22 seats against a
resected end 56 of the femur above an entrance 57 to the
intramedullary canal 59. In this embodiment, the bone fixation body
16 extends into the intramedullary canal, and the neck body 14
extends outwardly from the resected end of the initramyedullary
canal and femur. Further, the proximal end surfaced 40 is adjacent
the entrance 57 to the intramedullary canal.
[0030] As noted, the bone fixation body 16 has a porous structure
that extends throughout the body from the proximal end surface to
the distal end surface. By "porous," it is meant that the material
at and under the surface is permeated with interconnected
interstitial pores that communicate with the surface. The porous
structure can be formed by sintering titanium, titanium alloy
powder, metal beads, metal wire mesh, or other suitable materials,
metals, or alloys known in the art.
[0031] The porous structure of body 16 is adapted for the ingrowth
of cancellous and cortical bone spicules. In the exemplary
embodiment, the size and shape of the porous structure emulates the
size and shape of the porous structure of natural bone. Preferably,
the average pore diameter of body 16 is about 40 .mu.m to about 800
.mu.m with a porosity from about 45% to 65%. Further, the
interconnections between pores can have a diameter larger than
50-60 microns. In short, the geometric configuration of the porous
structure should encourage natural bone to migrate and grow into
and throughout the entire body 16.
[0032] Although specific ranges are given for pore diameters,
porosity, and interconnection diameters, these ranges are exemplary
and are applicable to one exemplary embodiment. In other
embodiments, these ranges could be modified, and the resulting hip
implant still within the scope of the invention.
[0033] Preferably, body 16 is created with a sintering process. One
skilled in the art will appreciate that many variations exist for
sintering, and some of these variations may be used to fabricate
the present invention. In the exemplary embodiment, the neck body
is formed from a solid piece of metal and prepared using
conventional and known machining techniques. Next, a ceramic mold
is provided. The mold has a first cavity that is sized and shaped
to match the size and shape of the bone fixation body. In this
first cavity, the sintering material can be placed. The mold also
has a second cavity that is adjacent and connected to the first
cavity. This second cavity is sized and shaped to receive the neck
body. The neck body is positioned in the second cavity such that
the distal end surface is adjacent and continuous with the first
cavity.
[0034] The sintering material is then placed into the first cavity.
This material may be a titanium alloy powder, such as Ti-6Al-4V.
Sonie of this powder will contact the distal end surface of the
neck body. The mold is then heated to perform the sintering
process. During this process, as the material in the first cavity
heats and sinters, the bone fixation body forms and simultaneously
bonds or fuses to the distal end surface of the neck body.
[0035] The size and shape of the pores and porous structure
produced in the first cavity depend on many factors, These factors
include, for example, the temperature obtained in the furnace, the
sintering time, the size and shape of sintering material, the
composition of the sintering material, and the type of ceramic mold
used. These factors (and others) can be varied to produce a bone
fixation body in accordance with the present invention. Further,
these factors (and others) can be varied to produce a strong bond
between the bone fixation body and neck body.
[0036] Once the sintering process is finished, the neck body is
directly fused to the bone fixation body. These two bodies are now
permanently connected together to form the hip implant.
[0037] In the aforementioned sintering process, the bone fixation
body simultaneously forms and attaches to the neck body. One
skilled in the art though will appreciate that each of these bodies
can be fabricated independently and subsequently connected
together. If the bodies are made separately, then they may be
attached or fused together using known welding or brazing
techniques, for example.
[0038] In FIG. 1, for example, the bone fixation body has an
elongated tapering body with a slight bow. The bone fixation body,
though, may have other configurations and still be within the scope
of the invention. The size and shape of the body depend on the size
and shape of the cavity of the mold during the sintering process.
This cavity can be shaped, for example, to emulate the natural
size, shape, and contour of a human intramedullary canal. As such,
the bone fixation body will more naturally fit into the
intramedullary canal and conform to the natural anatomical contours
of a human patient.
[0039] FIGS. 3 and 4 show another hip implant 50 according to an
exemplary embodiment of the invention. With some differences,
implant 50 is similarly configured to the implant 10. As one
difference, the neck body 60 of implant 50 has two different and
distinct regions on its outer surface. A first region 62 has a
smooth outer surface. A second region 64 has a bone-engaging
surface that is contiguous and adjacent to the first region 62 on
one side and contiguous and adjacent the porous bone fixation body
66 on the other side. The second region is non-porous and is shaped
as a band that extends completely around the neck body. This second
region can be formed on the outer surface of the neck body with
various techniques. These techniques include, for example, coating
with HA, grit-blasting, etching, micro-texturing, other non-porous
surface treatments, or combinations of these techniques. This
surface 64 is provided as an intermediate zone between the porous
body and the smooth first region 62.
[0040] As shown in FIG. 4, the second region 64 is below collar 68
and is positioned into the intramedullary canal to contact bone.
Region 64, then, contacts bone, and region 62 does not contact bone
and extends above it.
[0041] FIG. 5 shows another implant 70 according to another
exemplary embodiment of the invention. With some differences,
implant 70 is similarly configured to the implant 10. As one
difference, neck body 72 includes a male protrusion 74 that extends
outward from base portion 76. This protrusion 74 is adapted to
extend partially into the bone fixation body 78 of implant 70.
[0042] The protrusion 74 forms a core for the bone fixation body.
As shown in FIG. 5, this protrusion extends past the proximal end
surface 80 and into the bone fixation body. The depth of the
protrusion into the bone fixation body can be increased or
decreased in various embodiments and still remain within the scope
of the invention. For example, the protrusion can partially extend
into the bone fixation body and remain substantially near the
proximal end surface. Alternatively, the protrusion can extend
farther into the bone fixation body toward the distal end surface
82. In this latter embodiment, the protrusion gradually tapers as
it extends toward the distal end surface.
[0043] The size and shape of the protrusion can also have various
embodiments and still remain within the scope of the invention. For
example, the protrusion can be cylindrical or polygonal, such as
rectangular or square. Other configurations are possible as well;
the protrusion can taper or have longitudinal ribs placed along its
outer surface. The size and shape of the protrusion can have
various embodiments to serve various functions. For example, the
protrusion can be sized and shaped to provide a strong connection
between the neck body and bone fixation body. The protrusion can be
sized and shaped to provide an anti-rotational interface between
the neck body and bone fixation body. Further, the protrusion can
be sized and shaped to provide additional strength to the bone
fixation body or more equally or efficiently distribute loads from
the neck body to the bone fixation body. Other factors as well may
contribute to the design of the protrusion.
[0044] FIG. 6 shows another implant 90 according to an exemplary
embodiment of the invention. Implant 90 has a bone fixation body 92
with an outer surface that has a plurality of undulations 94, such
as hills and valleys. These undulations may be provided as tiny
ripples or waves. Alternatively, the undulations may be larger and
more rolling. Regardless, the undulations are adapted to firmly
secure the implant into the intramedullary canal of the femur after
the implant is placed therein.
[0045] As shown in FIG. 6, the undulations extend along the entire
length of the bone fixation body 92 from the proximal end surface
96 to the distal end surface 98. In alternative embodiments, the
undulations do not extend along the entire length of the bone
fixation body, but partially extend along this body.
[0046] FIGS. 7-9 show various longitudinal cross-sectional shapes
of the bone fixation body for different exemplary embodiments of
the invention. The bone fixation body may have one single
longitudinal cross-sectional shape, or the body may have numerous
different longitudinal cross-sectional shapes. FIGS. 7-9 represent
examples of some of these shapes.
[0047] FIG. 7 shows a trapezoidal longitudinal cross-sectional
shape. FIG. 8 shows a triangular longitudinal cross-sectional
shape. FIG. 9 shows an elliptical or oval longitudinal
cross-sectional shape.
[0048] The bone fixation body can be adapted to induce bone growth
partially into or entirely through the body. The body, for example,
can be doped with biologically active substances. These substances
may contain pharmaceutical agents to stimulate bone growth all at
once or in a timed-release manner. Such biological active
substances are known in the art.
[0049] Although illustrative embodiments have been shown and
described, a wide range of modifications, changes, and
substitutions is contemplated in the foregoing disclosure; and some
features of the embodiments may be employed without a corresponding
use of other features. Accordingly, it is appropriate that the
appended claims be construed broadly and in a manner consistent
with the scope of the embodiments disclosed herein.
* * * * *