U.S. patent application number 17/025035 was filed with the patent office on 2021-01-07 for hybrid compress bone fixator.
The applicant listed for this patent is Zimmer, Inc.. Invention is credited to Ronald Raymond Hugate, JR..
Application Number | 20210000619 17/025035 |
Document ID | / |
Family ID | |
Filed Date | 2021-01-07 |
United States Patent
Application |
20210000619 |
Kind Code |
A1 |
Hugate, JR.; Ronald
Raymond |
January 7, 2021 |
HYBRID COMPRESS BONE FIXATOR
Abstract
A stem for fixating a prosthesis to a bone can include a first
stem portion and a second stem portion. The first stem portion can
extend substantially along a longitudinal axis. The first stem
portion can include a distal portion. The second stem portion can
extend substantially distally from the distal portion of the first
stem portion along the longitudinal axis. The second stem portion
can be securable to the bone independent of the first stem portion,
and the second stem portion can include a distal portion couplable
to a compress assembly.
Inventors: |
Hugate, JR.; Ronald Raymond;
(Highlands Ranch, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zimmer, Inc. |
Warsaw |
IN |
US |
|
|
Appl. No.: |
17/025035 |
Filed: |
September 18, 2020 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
16017184 |
Jun 25, 2018 |
|
|
|
17025035 |
|
|
|
|
62604152 |
Jun 26, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
International
Class: |
A61F 2/78 20060101
A61F002/78; A61F 2/28 20060101 A61F002/28; A61B 17/72 20060101
A61B017/72 |
Claims
1. A method for fixating a prosthesis to a bone, the method
comprising: inserting a proximal portion of a stem of the
prosthesis into the bone in an interference fit to secure the
proximal portion to the bone; inserting a distal portion of the
stem into the bone, the distal portion connected to the proximal
portion, the distal portion including an outer diameter smaller
than an outer diameter of the proximal portion, and the outer
diameter of the distal portion configured to be smaller than a
diameter of an intramedullary canal of the bone; and securing a
fastener through the bone and through a bore of the distal portion
to secure the distal portion of the stem to the bone.
2. The method of claim 1, wherein the distal portion has a polished
outer surface to limit bone on-growth.
3. The method of claim 2, wherein the proximal portion includes an
outer surface comprising a porous material configured to promote
bone ingrowth.
4. The method of claim 3, wherein inserting the proximal portion of
the stem of the prosthesis into the bone includes engaging the bone
with a plurality of projections that extend radially along an outer
surface of the proximal portion, wherein the plurality of
projections extend axially along the proximal portion, and wherein
the plurality of projections are spaced around a circumference of
the proximal portion.
5. The method of claim 1, further comprising: engaging a distal
resected surface of the bone with a compress assembly secured to
the distal portion of the stem.
6. The method of claim 5, further comprising: securing a plurality
of fasteners through the bone and through a plurality of bores of
the distal portion to secure the distal portion of the stem to the
bone.
7. The method of claim 1, wherein the proximal portion and the
distal portion are connected by one of a fillet, chamfer, bevel, or
round.
8. The method of claim 1, wherein an outer surface of the proximal
portion is made of Ti6Al4V and has a porous structure that is
configured to mimic a porous structure of human cancellous
bone.
9. The method of claim 1, wherein the distal portion of the distal
portion of the stem includes a threaded portion configured to
receive a fastener to secure the distal portion to a biasing
element.
10. The method of claim 1, wherein the diameter of the distal
portion is constant along an axial length of the distal portion
between a distal end of the distal portion and a transition between
the proximal portion and the distal portion.
11. A method for fixating a prosthesis to a bone, the method
comprising: inserting a proximal portion of a stem of the
prosthesis into the bone in an interference fit to secure the
proximal portion to the bone; inserting a distal portion of the
stem into the bone, the distal portion connected to the proximal
portion, the distal portion including an outer diameter smaller
than an outer diameter of the proximal portion, and the outer
diameter of the distal portion configured to be smaller than a
diameter of an intramedullary canal of the bone; engaging a distal
resected surface of the bone with a compress assembly secured to
the distal portion of the stem; and securing a fastener through the
bone and through a bore of the distal portion to secure the distal
portion of the stem to the bone.
12. The method of claim 11, further comprising: securing a
plurality of fasteners through the bone and through a plurality of
bores of the distal portion to secure the distal portion of the
stem to the bone.
13. The method of claim 12, wherein the distal portion has a
polished outer surface to limit bone on-growth.
14. The method of claim 13, wherein the proximal portion includes
an outer surface comprising a porous material configured to promote
bone ingrowth.
15. The method of claim 14, wherein inserting the proximal portion
of the stem of the prosthesis into the bone includes engaging the
bone with a plurality of projections that extend radially along an
outer surface of the proximal portion, wherein the plurality of
projections extend axially along the proximal portion, and wherein
the plurality of projections are spaced around a circumference of
the proximal portion.
16. A method for fixating a prosthesis to a bone, the method
comprising: inserting a stem of the prosthesis into the bone so
that a proximal portion of the stem engages the bone an
interference fit to secure the proximal portion to the bone, the
stem including a distal portion connected to the proximal portion,
the distal portion including an outer diameter smaller than an
outer diameter of the proximal portion, and the outer diameter of
the distal portion configured to be smaller than a diameter of an
intramedullary canal of the bone; engaging a distal resected
surface of the bone with a compress assembly secured to the distal
portion of the stem; and securing a plurality of fasteners through
the bone and through a plurality of bores of the distal portion to
secure the distal portion of the stem to the bone.
17. The method of claim 16, wherein the distal portion has a
polished outer surface to limit bone on-growth; and wherein the
proximal portion includes an outer surface comprising a porous
material configured to promote bone ingrowth.
18. The method of claim 17, wherein inserting the stem of the
prosthesis into the bone includes engaging the bone with a
plurality of projections that extend radially along an outer
surface of the proximal portion, wherein the plurality of
projections extend axially along the proximal portion, and wherein
the plurality of projections are spaced around a circumference of
the proximal portion.
19. The method of claim 18, wherein the compress assembly includes
a housing configured to receive the distal portion of the stem
therein, the housing including a proximal portion engageable with
the distal resected portion of the bone.
20. The method of claim 19, wherein the compress assembly includes
a biasing element located within the housing and configured to
engage the distal portion of the stem and the housing to bias the
housing proximally and to bias the distal portion of the stem
distally.
Description
CLAIM OF PRIORITY
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/017,184, filed on Jun. 25, 2018, which
claims the benefit of U.S. Provisional Patent Application Ser. No.
62/604,152, filed on Jun. 26, 2017, the benefit of priority of
which is claimed hereby, and which is incorporated by reference
herein in its entirety.
BACKGROUND
[0002] The present subject matter relates to orthopedic prostheses
and, more particularly, to prostheses, systems, and methods used
with prosthetic limbs. Orthopedic procedures and prostheses are
commonly utilized to repair and/or replace damaged bone and tissue
in the human body. For example, an above-the-knee amputation can
also include installation of an implant anchored to a femur of a
patient. A compress implant creates compression at a
bone-to-implant interface causing subsequent reactive bone
stimulation and formation that results in osseous integration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] In the drawings, which are not necessarily drawn to scale,
like numerals can describe similar components in different views.
Like numerals having different letter suffixes can represent
different instances of similar components. The drawings illustrate
generally, by way of example, but not by way of limitation, various
embodiments discussed in the present document.
[0004] FIG. 1 illustrates a front cross-sectional view of an
implant assembly and a leg, in accordance with at least one example
of this disclosure.
[0005] FIG. 2 illustrates a front cross-sectional of an implant
assembly and a leg, in accordance with at least one example of this
disclosure.
[0006] FIG. 3 illustrates a schematic view of a method, in
accordance with at least one example of this disclosure.
DETAILED DESCRIPTION
[0007] In some circumstances, a patient may require a bone implant
to adapt a resected bone for connection to an external prosthesis.
One type of implant is a compress where compression to the
bone/implant interface can be achieved through the placement of an
anchoring plug or stem within the intramedullary canal of the bone.
In some examples, a series of transversely oriented pins are placed
through the bone and through pre-drilled holes in the stem to act
as a base from which to create compression. The other end of the
stem can be attached to a spindle or housing of the compress
assembly with a roughened surface that contacts the end of the
hone. The stem can be engaged with a biasing element, such as a
stack of curved washers, that can create compressive forces in the
range of 1800 Newtons or more. This compressive force at the
bone-implant interface can take advantage of Wolf's Law to
stimulate formation of osseous integration of the bone with the
implant.
[0008] While this construct has proven effective at creating a
compressive interface and osseous integration in difficult clinical
situations (especially in the setting of limited bone), there are a
number of issues with some of these compress systems. For example,
a compress construct does not resist bending loads very well. The
anchor or stem can be designed to create a compressive force. Its
outer diameter can be relatively small (just enough cross-sectional
material to withstand the anticipated tension). This can create a
situation where the recipient of a compress implant can be at a
risk of fracture during the first several weeks postoperatively,
until reactive bone forms and osseous integration of the spindle
can be achieved. Early postoperative fractures have therefore been
an issue with compress implants.
[0009] The success of many compress implants depends on their
placement. Concentric placement of a device can be essential in its
success. While the technique guide and instruments are excellent, a
small amount of eccentricity can load the implant unevenly, which
can lead to failure. Because (in part) of the design, some compress
implants do not tolerate less than perfect placement.
[0010] Some patients who need fixation have poor biology. Compress
implants rely less on mechanical fixation and more on biologic
fixation over the long term. If the implant does not create osseous
integration within a few weeks or months, it may not have enough
stand-alone mechanical integrity to maintain fixation and will
eventually fail mechanically.
[0011] Many patients who would be candidates for a compress implant
have poor bone quality. Patients with multiple failed joint
replacements, or cancers (requiring chemotherapy), or more recently
the transdermal osseous integration candidates, all tend to have
very poor bone quality. With an anchor plug that will be
transmitting up to 3600 Newtons of compression through the cortical
bone, poor bone quality may not be tolerated well in compress-type
implants, which can lead to catastrophic failure if fracture
occurs.
[0012] Intrinsic to some compress-type implants, is the creation of
stress risers (or stress concentrations). A series of transverse
pins can be placed through the bone and through the anchor plug to
create a base for the compressive force to pull against. These
transverse drill holes and pins can create a stress riser in this
location, which, combined with poor bone quality, could result in a
failure or fracture.
[0013] To utilize positive aspects of compress-type implants
(long-term, biologically active osseous integration), while
simultaneously addressing the issues discussed above, this
disclosure proposes a hybrid compress stem as a solution. The
hybrid compress can combine the benefits of traditional stem
technology with the benefits of compress technology, satisfying the
needs of patients and satisfying surgeons who may have concerns
about the compress limitations. One solution can be to provide a
press-fit or cemented stem, straight or curved, along with a
compress mechanism at the bone implant interface. The press-fit or
cemented stem can fill the role of traditional stems with strong
early fixation, early stability in bending and torsion, and early
intrinsic mechanical strength and fixation, while the compress
mechanism can provide long-term osseous integration and can
increase fixation.
[0014] Many clinicians like the idea of a compress, but are put off
by its lack of immediate mechanical stability, difficulty of
positioning, and implications of its use in those with poor bone
quality or restricted biology. The hybrid design addresses those
concerns and can provide clinicians a valuable tool in these
difficult cases.
[0015] In one example, a spindle of a compress assembly can abut a
bone face and can be contiguous with a distal stem section. The
distal stem section can be a stem section of smooth, polished stem.
The distal stem section can be slightly smaller in diameter than
the endosteal diameter of the bone so as not to create a press or
interference fit. The distal stem section can vary in length
(depending on bone quality and clinical conditions). The distal
stem section can avoid integration with bone, to allow the bone to
compress longitudinally without resistance and to allow for
compressive forces of the compress assembly to load the bone
implant interface.
[0016] Under certain circumstances, a substance coating can be
applied to the surface of the distal stem section to help reduce
bone on-growth and/or to help prevent cement adhesion (should the
clinician decide to cement a proximal portion of the stem for
fixation). A proximal end of the distal stem section an include
smooth cross-drilled receptacles or bores for to receive anchoring
pins. The bores can be manufactured to reduce the stress riser
effect within the stem.
[0017] The proximal stem section can continue from the distal stem
section. The proximal stem section can be the portion of the hybrid
stem that can help provide immediate fixation. The proximal stem
section can help achieve immediate stability through press-fit or
cemented means, depending on the clinical scenario and clinician
preference. The proximal stem portion can also be of variable
length. Short and long straight press fit stems can have either
in-growth or on-growth surfaces, limited to the proximal stem
portion, and can have endosteal flutes that can engage the
endosteal cortex and can help to provide some immediate rotational
stability.
[0018] The proximal stem section of can be press or interference
fit to provide immediate fixation and stability of the implant.
Longer curved press-fit stems may not require endosteal flutes, as
they would be rotationally stable intrinsically in curved bone
(i.e. femur). Short or long stems could also be cemented for
immediate fixation, where a goal can be to limit the extent of the
cement fixation to the proximal stem portion only. The entirety of
the stem (proximal and distal stem portions) can be either straight
or curved and of variable length. Longer stems will need to be
curved to accommodate the anatomy in certain bones of the femur
(i.e. femur).
[0019] Alternatively, the stem can be such that the distal stem
portion can be entirely straight and such that the surface of the
distal stem portion can be prepared in such a way that cement could
not adhere to the surface of the distal stem portion, thereby
allowing longitudinal compression through the distal stem portion
to the compress assembly.
[0020] FIG. 1 illustrates a front cross-sectional view of an
implant assembly 100 and a leg 10, in accordance with at least one
example of this disclosure. The implant assembly 100 can be a
hybrid compress fixation system or assembly configured to secure a
prosthesis to the leg 10.
[0021] The leg 10 can include a bone 12, including a resected
distal portion 14, and an intramedullary canal 16. The leg 10 can
also include a dermis portion 18. The implant assembly 100 can
include a first stem portion 102, a second stem portion 104, a
compress assembly 106, and pins 108A-108C. The first stem portion
102 can include flutes 110 and can have a diameter of D1. The
second stem portion 104 can include bores 112A-112C and can have a
diameter of D2. The intramedullary canal 16 of the bone 12 can have
a diameter of D3. Also shown in FIG. 1 are orientation indicators
Proximal and Distal and an axis A.
[0022] The leg 10 can be, in some examples, a superior or proximal
leg portion, where the bone 12 is a femur, and the resected distal
portion 14 is created during a procedure, such as an amputation
and/or a femoral implant procedure, where the bone 12 of the femur
is resected to create a surface to receive the compress assembly
106 thereon.
[0023] The first stem portion 102 can be a rigid or semi-rigid and
elongate body extending substantially along axis A and connecting
to the second stem portion 104 at a distal end of the first stem
portion 104. In some examples, the first stem portion 102 can be
comprised of biocompatible materials such as such as stainless
steels, cobalt-chromium, titanium variations, polyether ether
ketone (PEEK), and combinations thereof.
[0024] In some examples, the first stem portion 102 can have a
substantially cylindrical shape (having a substantially consistent
diameter D1). In other examples, the first stem portion can have
other geometric shapes. For examples, the first stem portion 102
can be tapered from a proximal end of the first stem portion 102 to
a distal end to make insertion into the intramedullary canal 16
easier and to help ensure an outer surface of the first stem
portion engages an endosteum and/or compact bone of the bone
12.
[0025] Accordingly, the first stem portion 102 can have a diameter
of D1 that is larger than the diameter D3 of the intramedullary
canal, such that the first stem portion 102 can engage the bone 12
in a press-fit configuration or an interference fit arrangement
between the first stem portion 102 and the bone 12 within the
intramedullary canal 16.
[0026] In some examples, the first stem portion 102 can include
flutes 110, which can be radial projections extending axially along
an outer surface of first stem portion 102. The flutes 110 can be
circumferentially disposed around first stem portion 102 and can be
of a quantity of flutes 110 such as 1, 2, 3, 4, 5, 6, 10, 15, and
the like. The flutes 110 can be configured to engage the endosteum
and/or compact bone of the bone 12 to help prevent axial and
rotational movement of the first stem portion 102 relative to the
intramedullary canal 16 and the bone 12. The flutes 110 can thereby
improve early fixation of the implant assembly 100 to the bone 12
before osseointegration occurs, which can help limit movement of
the implant assembly 100 and can help prevent fractures of the bone
12 and the implant assembly 100.
[0027] In some examples, the flutes 110 can have a diameter that is
larger than the diameter D3 of the intramedullary canal 16 to
ensure an interference fit between the bone 12 and the flutes 110.
In some of these examples, the diameter of the flutes 110 can be
larger than the diameter D1 of the first portion 102, which can
also be larger than the diameter D3 of the intramedullary canal 16,
such that the first stem portion 102 can engage the bone 12 in an
interference fit and the flutes 110 can extend radially further
into the bone 12, to help further limit movement of the implant
assembly 100, such as axial translation and rotation of the implant
with respect to the bone 12.
[0028] In some examples, the first stem portion 102 can have a
surface finish and/or can be made of a material configured to
promote bone in-growth and/or on-growth, such as a porous surface
finish, to enhance fixation (such as through osseointegration) of
the first stem portion 102 to the bone 12. For example, one porous
material the first stem portion 102 can be made of (or made
partially of) is OsseoTi.TM. porous metal from Zimmer Biomet.TM.
(Warsaw, Ind.). OsseoTi can be made out of Ti6A14V and can have a
porous structure that generally mimics a porous structure of human
cancellous bone. Also, the porous material can be Trabecular
Metal.TM., also from Zimmer Biomet. Such a material can be formed
from a reticulated vitreous carbon foam substrate that can be
infiltrated and coated with a biocompatible metal, such as
tantalum, such as using a chemical vapor deposition ("CVD") process
in the manner disclosed in detail in U.S. Pat. No. 5,282,861. Also,
the porous material can be Regenerex.RTM. can be used, also from
Zimmer Biomet. In other examples, other porous materials can be
used.
[0029] In some examples, the first stem portion 102 can be
configured to be fixed to the bone 12 using a bone cement or
adhesive. In these examples, the flutes 110 may or may not be
included. In some examples, the first stem portion 102 can include
ejection ports for ejecting adhesive therefrom through implant
assembly 100.
[0030] The second stem portion 104 can be a rigid or semi-rigid and
elongate body extending substantially along axis A and connecting
to the first stem portion 102 at a distal end of the first stem
portion 102 and a proximal end of the second stem portion 104. In
some examples, the first stem portion 104 can be comprised of
biocompatible materials such as such as stainless steels,
cobalt-chromium, titanium variations, polyether ether ketone
(PEEK), and combinations thereof.
[0031] The second stem portion 104 can have a diameter D2 that is
smaller than the diameter D3 of the intramedullary canal 16 and, in
some examples, smaller than the diameter D1 of the first stem
portion 102. In some examples, the diameter D2 of the second stem
portion 104 can be smaller than the diameter D3 of the
intramedullary canal 16 such that contact between the second stem
portion 104 and the intramedullary canal 16 is reduced to help
limit friction or interaction between the second stem portion 104
and the bone 12 and to help reduce in-growth and on-growth onto the
second stem portion 104. Further, the second portion 104 can have a
smooth or polished surface to help reduce bone in-growth and
on-growth. In other examples, one or more coatings or layers can be
applied to the surface of the second stem portion 104 to help
prevent in-growth and on-growth. By helping to reduce in-growth and
on-growth, these features can help to allow the bone 12 to compress
axially without resistance and can help to allow for compressive
forces of the compress assembly to load the bone/implant
interface.
[0032] The second stem portion 104, can include bores 112A-112C,
which can be bores extending through the second stem portion 104
substantially transversely to axis A. Though only three bores are
shown in FIG. 1, the second stem portion 104 can include five
bores, as shown in FIG. 2, and can include fewer or more bores in
other examples, such as 1, 2, 3, 4, 6, 7,8, 9, 10, or the like. In
some examples, each of bores 112A-112C can be configured to receive
one of the pins 108A-108C, respectively, therethrough.
[0033] In some examples, the pins 108A-108C can be rigid or
semi-rigid and elongate fasteners configured to secure the bone 12
to the second stem portion 104. In some examples, each of the pins
108A-108C can have a tapered profile and/or a sharp or tapered tip.
In some examples, each of the pins 108A-108C can be other types of
fasteners, such as a screw, rivet, or the like.
[0034] Lengths of each of the first stem portion 102 and the second
stem portion 104 can vary depending on bone quality and clinical
conditions. In some examples, the lengths of one or more of the
first stem portion 102 and the second stem portion 104 can be
optimized for a patient. Similarly, curvature or both the first
stem portion 102 and the second stem portion 104 can vary depending
on clinical conditions, such as bone quality, and available length
of the femur for implant insertion. In examples where a curved
first stem portion 102 and/or second stem portion 104 is used,
fluting may not be required.
[0035] The compress assembly 106 can be configured to couple to the
second stem portion 104 at a distal portion of the second stem
portion 104. The compress assembly 106 can also be configured to
engage the distal resected portion 14 of the bone 12 to apply a
compressive force to the bone 12. The components of the compress
assembly 106 are discussed in further detail below with respect to
FIG. 2.
[0036] In operation of some examples, the bone 12 can be resected
to create the resected distal portion 14. Following resection and
preparation, the first stem portion 102 can be inserted distally to
proximally into the intramedullary canal 16 of the bone 12. In some
examples, cement or adhesive can be applied to the first stem
portion 102 before, during, and/or after insertion into the
intramedullary canal 16. The first stem portion 102 of implant
assembly 100 can be inserted into the bone 12 distally to
proximally, such that the first stem portion 102 engages the
endosteum of the bone 12 in an interference or press-fit
arrangement. In some examples, the flutes 110 can also engage the
endosteum of the bone 12. The first stem portion 102 can be
inserted into the intramedullary canal 16 of the bone 12 until the
second stem portion 104 is disposed within the bone 12 and until
the compress assembly 106 contacts the distal resected portion 14
of the bone 12.
[0037] In some examples, pilot or guide holes can be drilled
through the bone 12 to align with the bores 112A-112C. These holes
can be pre-drilled into bone 12 using guide tools, in some
examples. The bores 112A-112C can be aligned with respective holes
through the bone 12 so that pins 108A-108C can be passed through
respective bores 112A-112C, as shown in FIG. 1. Pins 108A-108C can
thereby secure the second stem portion 104 to the bone 12. The
engagement of the first stem portion 102 with the endosteum (and in
some cases compact bone) of the bone 12 can help provide near
immediate transmission of forces between the bone 12 and an
external prosthesis, which can help reduce a possibility of
fracture prior to osseointegration of the implant assembly 100. In
some examples, engagement of the flutes 110 with the endosteum of
the bone 12 and/or adherence of the first stem portion 102 to the
bone 12 using an adhesive can further help provide near immediate
transmission of forces between the bone 12 and an external
prosthesis. In this way, the features of implant assembly 100 can
provide a balance of long-term mechanical integrity through osseous
integration from the second stem portion 104 and the compress
assembly 106 with early fixation provided by a mechanical stem (the
first stem portion 102).
[0038] FIG. 2 illustrates a front cross-sectional view of the
implant assembly 100 and the leg 10, in accordance with at least
one example of this disclosure. The implant assembly 100 shown in
FIG. 2 can be the same as the implant assembly 100 of FIG. 1;
however, FIG. 2 shows additional details of the implant assembly
100.
[0039] The implant assembly 100 can include the first stem portion
102, the second stem portion 104, the compress assembly 106, and a
prosthesis adapter 114. The first stem portion 102 can include
flutes 110 and can have the diameter of D1. The second stem portion
104 can include bores 112A-112E, a threaded portion 116, and can
have the diameter of D2. The prosthesis adapter 114 can include a
tapered bore 118, and a threaded female bore 120. The compress
assembly 106 can include a housing 122, a biasing element 124, a
stem retainer 126, and a plug 128. The housing 122 can include a
proximal housing portion 130, a cavity 132, and a plug bore 134.
The intramedullary canal 16 of the bone 12 can have the diameter of
D3. Also shown in FIG. 2 are orientation indicators Proximal and
Distal and an axis A.
[0040] Because the first stem portion 102 can have a greater
diameter than the second stem portion 104, the second stem portion
104 can be connected to the first stem portion 102 at a transition
105. In some examples, the transition 105 can be a round, chamfer,
bevel, J groove, combination thereof, or the like. The transition
105 can help prevent a stress concentration or stress riser between
the first stem portion 102 and the second stem portion 104.
[0041] The second stem portion 104 can include bores 112A-112E in a
staggered pattern to accommodate multiple fasteners therethrough,
as discussed in detail in FIG. 1 above. In other examples, other
patterns can be used and other quantities of bores can be used. In
some examples, the bores 112A-112E can include edges that include a
round, chamfer, bevel, J groove, combination thereof, or the like,
to help reduce a stress concentration or stress riser at each of
the bores 112A-112E.
[0042] The second stem portion 104 can extend axially distally at a
substantially consistent diameter, D2, throughout a length of the
second stem portion 104, such as from the transition 105 through
the threaded portion 116. As discussed further below, the diameter
D2 of the second stem portion 104 can be large enough to transfer
loads between the first stem portion and the compress assembly (and
therefore an external prosthesis) to help avoid stem or bone
fracture prior to osseointegration of the implant and the bone. In
other examples, the diameter of the second stem portion 104 can
vary along the length of the second stem portion 104.
[0043] In some examples, stem retainer 126 can be a nut; however,
in other examples, stem retainer 126 can be other types of
fasteners. In one example, the biasing element 124 can be a washer
stack sized and configured to receive threaded portion 116 of the
second stem portion 104 therethrough. In some examples, biasing
element 124 can be other types of resilient elements, such as a
coil spring, one or more wave springs, or the like. In other
examples, biasing element 124 can be one or more compressible and
resilient members comprised of resilient materials such as rubbers,
plastic, and the like.
[0044] The threaded portion 116 of the second stem portion 104 can
be located at a distal portion of the second stem portion 104 and
can be insertable into the cavity 132 of the housing 122 and
through biasing element 124 and can be secured therein by the stem
retainer 126. The stem retainer 126 can also engage a distal
portion of the biasing element 124, compressing the biasing element
between the housing 122 and the stem retainer 126, simultaneously
securing the threaded portion 116 within the housing 122 and
securing the biasing element 124 between the housing 122 and the
stem retainer 126. In some examples, the stem retainer 126 can be
threaded onto the threaded portion 116 to compress the biasing
element to achieve a desired force applied to the housing 122 and
the stem retainer 126 (and therefore to the second portion of the
stem 104).
[0045] The prosthesis adapter 114 can include a tapered bore 118
configured to engage an outer taper of housing 122 such that the
prosthesis adapter 114 and the housing 122 engage in a
taper-to-taper arrangement. In some examples, the tapered bore 118
and the housing 122 can have one consistent taper and in other
examples, the tapered bore 118 and the housing 122 can have
multiple tapered portions of varying taper sizes and/or styles
including Brown, Morse, Jarno, Jacobs, and the like tapers. The
threaded female bore 120 of the prosthesis adapter can be
configured to receive a fastener (such as a screw or bolt) secure
an external prosthesis to the prosthesis adapter.
[0046] The plug 128 can be a member insertable into and securable
within the plug bore 134 of the housing 122 to seal the cavity 132
of the housing 122. In some examples, the plug 128 can be a
threaded member, threadably securable to the plug bore 134 of the
housing 122. The proximal housing portion 130 can be a proximal
portion of the housing 122 and can be comprised of materials
configured to support bone ingrowth and/or ongrowth to enhance
fixation of the housing 122 to the bone 12 (such as through
osseointegration), such as Trabecular Metal.TM., Regenerex.RTM., or
OsseoTi.RTM., described above, a roughened surface, and/or
hydroxyapatite.
[0047] In operation, after the first stem portion 102 and the
second stem portion 104 have been inserted into and secured to the
bone 102, the biasing element 124 can be secured around the second
stem portion 104 using the stem retainer 126. The biasing element
124 can be compressed and retained within the housing 122 before or
during the procedure. The stem retainer 126 can be threadably
secured to the second stem portion 104 such that biasing element
124 applies a substantially distally directed force on stem
retainer 126, which is transferred to second stem portion 104 and
to pins 108A-108E and ultimately to bone 12. The biasing element
124 also applies a substantially proximally directed force on
housing 122 which is transferred to the distal resected portion 14
of bone 12. In other words, the biasing element 124 is configured
to bias the housing 122 proximally and to bias the second stem
portion 104 distally. These forces combine to impose a pair of
forces that compress the distal portion of bone 12 (between pins
108A-108E and the distal resected portion 14 of bone 12). The
compression can stimulate an increase in bone density and
osseointegration of the implant assembly 100 with bone 12.
[0048] Because the diameter D2 of the second stem portion 104 is
relatively large with respect to the intramedullary canal 16, the
second stem portion is strong enough to transfer loads between the
first stem portion and the compress assembly (and therefore an
external prosthesis) to help avoid stem or bone fracture prior to
osseointegration of the implant and the bone. For example, the
second stem portion 104 can transmit non-axial compressive loads,
such as eccentric loads and can accordingly transfer bending
moments. This can help prevent fracture or breakage of the implant
assembly 100 and can help reduce fracture of the bone 12.
[0049] FIG. 3 illustrates a schematic view of method 300, in
accordance with at least one example of this disclosure. Method 300
can be a method of securing an implant to a bone. The steps or
operations of method 300 are illustrated in a particular order for
convenience and clarity; many of the discussed operations can be
performed in a different sequence or in parallel without materially
impacting other operations. Method 300, as discussed, includes
operations performed by multiple different actors, devices, and/or
systems, it is understood that subsets of the operations discussed
in method 300 attributable to a single actor, device, or system
could be considered a separate standalone process or method.
[0050] Method 300 can begin at step 302 where a bone can be
resected. For example, the bone 12 of FIGS. 1 and 2 can be resected
to create the distal resected portion 14. In step 304, a stem can
be inserted into the bone. For example, the first stem portion 102
of implant assembly 100 can be inserted into the bone 12 distally
to proximally, such that the first stem portion 102 engages the
bone 12 in an interference or press-fit arrangement. The first stem
portion 102 can be inserted until the second stem portion 104 is
disposed within the bone 12 and until the compress assembly 106
contacts the distal resected portion 14 of the bone 12.
[0051] At step 306, the second stem portion can be secured to the
bone. For example, the second stem portion 104 can be secured to
the bone 12. In some examples, pilot or guide holes can be drilled
through the bone to align with bores of the second stem portion
(typically prior to stem insertion into the bone). For example,
holes can be drilled through the bone 12 such that the bores
112A-112C align with respective holes through the bone 12 following
insertion of the first stem portion 102 and the second stem portion
104 into the bone. Once the bores of the bone 12 are aligned with
the bores 112A-112C, fasteners, such as pins 108A-108C, can be
secured to the bone 12 and to the second stem portion 104 by
passing through respective bores 112A-112C.
[0052] Thereafter, the biasing element 124 can be compressed and
retained within the housing 122 using stem retainer 126 to secure
the housing 122 to the second stem portion 104 at the threaded
portion 116.
Notes and Examples
[0053] The following, non-limiting examples, detail certain aspects
of the present subject matter to solve the challenges and provide
the benefits discussed herein, among others.
[0054] Example 1 is a stem for fixating a prosthesis to a bone, the
stem comprising: a first stem portion extending substantially along
a longitudinal axis, the first stem portion including a first
diameter larger than a diameter of an intramedullary canal of a
bone such that the first stem portion is configured to engage the
bone, the first stem portion including a distal portion; and a
second stem portion extending substantially distally from the
distal portion of the first stem portion along the longitudinal
axis, the second stem portion including a second diameter smaller
than the first diameter and smaller than the diameter of the
intramedullary canal of the bone, the second stem portion securable
to the bone independent of the first stem portion, and the second
stem portion including a distal portion couplable to a compress
assembly.
[0055] In Example 2, the subject matter of Example 1 optionally
includes wherein the first diameter is sized such that the first
stem portion engages the bone in an interference-fit.
[0056] In Example 3, the subject matter of any one or more of
Examples 1-2 optionally include wherein the second stem portion
includes a plurality of bores each configured to receive a fastener
therethrough to secure the second stem portion to the bone
independent of the first stem portion.
[0057] In Example 4, the subject matter of any one or more of
Examples 1-3 optionally include wherein the first portion includes
a plurality of flutes extending radially from a surface of the
first stem portion, extending substantially axially along the first
stem portion, and spaced around a circumference of the first
portion, each of the plurality of flutes configured to engage the
bone to limit rotation of the stem relative to the bone.
[0058] In Example 5, the subject matter of any one or more of
Examples 1-4 optionally include wherein the second stem portion
includes a polished outer surface to limit bone on-growth.
[0059] In Example 6, the subject matter of any one or more of
Examples 1-5 optionally include wherein the first stem portion and
the second stem portion are connected by one of a fillet, chamfer,
bevel, or round.
[0060] In Example 7, the subject matter of any one or more of
Examples 1-6 optionally include wherein the first stem portion
includes an outer surface comprised of a porous material configured
to promote bone ingrowth.
[0061] In Example 8, the subject matter of Example 7 optionally
includes V and has a porous structure that substantially mimics a
porous structure of human cancellous bone.
[0062] In Example 9, the subject matter of any one or more of
Examples 1-8 optionally include wherein the distal portion of the
second stem portion includes a threaded portion configured to
receive a fastener to secure the second stem portion to a biasing
element.
[0063] In Example 10, the subject matter of any one or more of
Examples 1-9 optionally include wherein the diameter of the second
stem portions is substantially consistent along an axial length of
the second stem portion between a distal end of the second stem
portion and a transition between the first portion and the second
portion.
[0064] Example 11 is a hybrid compress fixation system for securing
a prosthesis to a bone, the system comprising: a compress assembly
including a proximal portion engageable with a resected distal
portion of a bone and distal portion securable to a prosthesis; a
stem comprising: a first stem portion extending substantially along
a longitudinal axis, the first stem portion including a first
diameter larger than a diameter of an intramedullary canal of a
bone such that the first stem portion is configured to engage the
bone, the first stem portion including a distal portion; and a
second stem portion extending substantially distally from the
distal portion of the first stem portion along the longitudinal
axis, the second stem portion including a second diameter smaller
than the first diameter and smaller than the diameter of the
intramedullary canal of the bone, the second stem portion securable
to the bone independent of the first stem portion, and the second
stem portion including a distal portion couplable to the compress
assembly.
[0065] In Example 12, the subject matter of Example 11 optionally
includes wherein the compress assembly includes a housing
configured to receive the second stem portion therein, the housing
including a proximal portion engageable with the resected distal
portion of the bone.
[0066] In Example 13, the subject matter of Example 12 optionally
includes wherein the compress assembly includes a biasing element
disposable within the housing and configured to engage the second
stem portion and the housing to bias the housing proximally and to
bias the second stem portion distally.
[0067] In Example 14, the subject matter of Example 13 optionally
includes wherein the compress assembly includes a fastener
securable to the distal portion of the second portion to engage and
retain the biasing element.
[0068] In Example 15, the subject matter of any one or more of
Examples 12-14 optionally include wherein the compress assembly
includes a taper adapter including a proximal tapered bore
configured to engage a distal taper of the housing to secure the
taper adapter to the housing in a taper-to-taper configuration.
[0069] In Example 16, the subject matter of Example 15 optionally
includes wherein the distal adapter is securable to the
prosthesis.
[0070] Example 17 is a stem for fixating a prosthesis to a bone,
the stem comprising: a first stem portion extending substantially
along a longitudinal axis, the first stem portion including a first
diameter larger than a diameter of an intramedullary canal of a
bone such that the first stem portion is configured to engage the
bone, the first stem portion including a distal portion; and a
second stem portion extending substantially distally from the
distal portion of the first stem portion along the longitudinal
axis, the second stem portion including a diameter that is
substantially consistent along an axial length of the second stem
portion between a distal end of the second portion and a connection
between the first portion and the second portion, and the second
stem portion including a distal portion couplable to a compress
assembly.
[0071] In Example 18, the subject matter of Example 17 optionally
includes wherein the second stem portion is securable to the bone
independent of the first stem portion, and wherein the second
diameter is smaller than the first diameter and smaller than the
diameter of the intramedullary canal of the bone.
[0072] In Example 19, the subject matter of any one or more of
Examples 17-18 optionally include wherein the first portion
includes a plurality of flutes extending substantially axially and
spaced around a circumference of the first portion, each of the
plurality of flutes configured to engage the intramedullary canal
to limit rotation of the stem relative to the bone.
[0073] In Example 20, the subject matter of any one or more of
Examples 17-19 optionally include wherein the first diameter is
sized such that the first stem portion engages the bone in an
interference-fit.
[0074] In Example 21, the subject matter of any one or more of
Examples 17-20 optionally include wherein the second stem portion
includes a plurality of bores each configured to receive a fastener
therethrough to secure the second portion to the bone.
[0075] In Example 22, the subject matter of any one or more of
Examples 17-21 optionally include wherein the second stem portion
includes a polished outer surface to limit bone on-growth.
[0076] In Example 23, the apparatuses or method of any one or any
combination of Examples 1-22 can optionally be configured such that
all elements or options recited are available to use or select
from.
[0077] The above detailed description includes references to the
accompanying drawings, which form a part of the detailed
description. The drawings show, by way of illustration, specific
embodiments in which the invention can be practiced. These
embodiments are also referred to herein as "examples." Such
examples can include elements in addition to those shown or
described. However, the present inventors also contemplate examples
in which only those elements shown or described are provided.
Moreover, the present inventors also contemplate examples using any
combination or permutation of those elements shown or described (or
one or more aspects thereof), either with respect to a particular
example (or one or more aspects thereof), or with respect to other
examples (or one or more aspects thereof) shown or described
herein.
[0078] In the event of inconsistent usages between this document
and any documents so incorporated by reference, the usage in this
document controls.
[0079] In this document, the terms "a" or "an" are used, as is
common in patent documents, to include one or more than one,
independent of any other instances or usages of "at least one" or
"one or more." In this document, the term "or" is used to refer to
a nonexclusive or, such that "A or B" includes "A but not B," "B
but not A," and "A and B," unless otherwise indicated. In this
document, the terms "including" and "in which" are used as the
plain-English equivalents of the respective terms "comprising" and
"wherein." Also, in the following claims, the terms "including" and
"comprising" are open-ended, that is, a system, device, article,
composition, formulation, or process that includes elements in
addition to those listed after such a term in a claim are still
deemed to fall within the scope of that claim. Moreover, in the
following claims, the terms "first," "second," and "third," etc.
are used merely as labels, and are not intended to impose numerical
requirements on their objects.
[0080] The above description is intended to be illustrative, and
not restrictive. For example, the above-described examples (or one
or more aspects thereof) can be used in combination with each
other. Other embodiments can be used, such as by one of ordinary
skill in the art upon reviewing the above description. The Abstract
is provided to comply with 37 C.F.R. .sctn. 1.72(b), to allow the
reader to quickly ascertain the nature of the technical disclosure.
It is submitted with the understanding that it will not be used to
interpret or limit the scope or meaning of the claims. Also, in the
above Detailed Description, various features can be grouped
together to streamline the disclosure. This should not be
interpreted as intending that an unclaimed disclosed feature is
essential to any claim. Rather, inventive subject matter can lie in
less than all features of a particular disclosed embodiment. Thus,
the following claims are hereby incorporated into the Detailed
Description as examples or embodiments, with each claim standing on
its own as a separate embodiment, and it is contemplated that such
embodiments can be combined with each other in various combinations
or permutations. The scope of the invention should be determined
with reference to the appended claims, along with the full scope of
equivalents to which such claims are entitled.
* * * * *