U.S. patent application number 12/681105 was filed with the patent office on 2010-09-30 for modular necks for orthopaedic devices.
This patent application is currently assigned to SMITH & NEPHEW, INC.. Invention is credited to Alisha W. Bergin, Jerry L. Jones, Richard D. Lambert.
Application Number | 20100249943 12/681105 |
Document ID | / |
Family ID | 40526656 |
Filed Date | 2010-09-30 |
United States Patent
Application |
20100249943 |
Kind Code |
A1 |
Bergin; Alisha W. ; et
al. |
September 30, 2010 |
MODULAR NECKS FOR ORTHOPAEDIC DEVICES
Abstract
There is provided a system of modular orthopaedic devices. The
system comprises one or more hip implants or trials, each hip
implant or trial having a femoral stem and one of at least two neck
segments having different geometries. Each neck segment comprises a
proximal end configured to receive a femoral head portion and a
distal end configured to be operably received by a proximal portion
of the femoral stem. Each proximal end comprises a central portion
generally representative of a femoral head center. When each of the
at least two neck segments are joined with the femoral stem, the
central portion is displaced a predetermined distance in a single
direction relative to the femoral stem. The neck segments provided,
therefore, advantageously allow a user to independently adjust any
one of a height, an offset, or a version angle of an orthopaedic
device for best performance and fit.
Inventors: |
Bergin; Alisha W.;
(Southaven, MS) ; Jones; Jerry L.; (Memphis,
TN) ; Lambert; Richard D.; (Germantown, TN) |
Correspondence
Address: |
DIANA HOUSTON;SMITH & NEPHEW, INC.
1450 BROOKS ROAD
MEMPHIS
TN
38116
US
|
Assignee: |
SMITH & NEPHEW, INC.
Memphis
TN
|
Family ID: |
40526656 |
Appl. No.: |
12/681105 |
Filed: |
October 1, 2008 |
PCT Filed: |
October 1, 2008 |
PCT NO: |
PCT/US2008/078511 |
371 Date: |
March 31, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60976717 |
Oct 1, 2007 |
|
|
|
60976697 |
Oct 1, 2007 |
|
|
|
Current U.S.
Class: |
623/22.42 |
Current CPC
Class: |
A61B 17/164 20130101;
A61F 2/0095 20130101; A61F 2/3609 20130101; A61F 2002/3071
20130101; A61F 2002/3625 20130101; A61F 2002/30616 20130101; A61F
2250/0085 20130101; A61B 17/1668 20130101; A61F 2/40 20130101; A61F
2002/30604 20130101; A61F 2/4684 20130101 |
Class at
Publication: |
623/22.42 |
International
Class: |
A61F 2/32 20060101
A61F002/32 |
Claims
1. A system of modular orthopaedic devices comprises: at least one
hip implant, the hip implant having a femoral stem; a head portion;
and at least two neck segments having different geometries, each
neck segment comprising a proximal end configured to receive the
femoral head portion and a distal end configured to be operably
received by a proximal portion of the femoral stem; wherein each
proximal end of each neck segment comprises a central portion
generally representative of a femoral head center such that when
each of the at least two neck segments are interchangeably joined
with the femoral stem, the central portion is displaced a
predetermined distance in a single direction relative to the
femoral stem.
2. The system of claim 1 wherein the single direction is any one of
a height, an offset, or a version angle of an orthopaedic
device.
3. The system of claim 1, wherein the at least one hip implant, the
head portion and the at least two neck segments are temporary
trials.
4. The system of claim 1, wherein the at least one hip implant, the
head portion and the at least two neck segments are modular neck
segments.
5. The system of claim 1, wherein the at least two neck segments
comprise a kit of neck segments configured to adjust leg length
independently of offset and/or version angle.
6. The system of claim 1, wherein the at least two neck segments
comprise a kit of neck segments configured to adjust implant offset
independently of overall implant height and version angle.
7. The system of claim 1, wherein the at least two neck segments
comprise a kit of neck segments configured to adjust version angle
independently of implant offset and overall implant height.
8. A method of using a modular orthopaedic device, comprising the
steps of: a. implanting a femoral stem of a hip implant for
cortical fixation; b. selecting a first neck segment with a first
geometry; c. assembling the first neck segment with the implanted
femoral stem; d. assessing an orientation of the first neck segment
in a first direction; e. removing the first neck segment from the
femoral stem; and f. replacing it with a second neck segment having
a second geometry, the second geometry being configured to move a
femoral head center a predetermined distance independently in the
first direction.
9. The method of claim 8 wherein the single direction is any one of
a height, an offset, or a version angle of an orthopaedic
device.
10. The method of claim 8, wherein the hip implant, and the first
and second neck segments are temporary trials.
11. The method of claim 8, wherein the wherein the hip implant; and
the first and second neck segments are modular neck segments.
12. The method of claim 8, wherein the replacing step further
comprises the step of choosing a second neck segment from a kit of
neck segments configured to adjust leg length independently of
offset and/or version angle.
13. The method of claim 8, wherein the replacing step further
comprises the step of choosing a second neck segment from a kit of
neck segments configured to adjust implant offset independently of
overall implant height and version angle.
14. The method of claim 8, wherein the replacing step further
comprises the step of choosing a second neck segment from a kit of
neck segments configured to adjust version angle independently of
implant offset and overall implant height.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/976,717, filed Oct. 1, 2007 and U.S. Provisional
Application No. 60/976,697, filed Oct. 1, 2007. The disclosure of
each application is incorporated by reference in its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] N/A
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates generally to orthopaedic
implants, and more particularly to modular femoral implants for use
in hip arthroplasty.
[0005] 2. Related Art
[0006] In some instances, an implant may sit higher or lower than
anticipated after its insertion into a medullary canal of a bone.
For example, in hip arthroplasty, a femoral stem portion of a hip
prosthesis may seat proximally proud, or might otherwise seat more
distally than expected after it is inserted into a prepared femoral
canal. This problem may cause the patient to have too short or too
long of a leg.
[0007] If the femoral stem portion sits too proud proximally, it
can be removed, and the medullary canal can be re-reamed with a
larger reamer to allow the stem to seat more distally. This
increases the risk of fracture and is more invasive, because
precious cortical bone is removed to make room for the prosthesis.
If the hip prosthesis seats too far distally in the femoral canal,
it can be removed, and re-reamed to make room for a larger
prosthesis.
[0008] In order to avoid these problems, prior implants have
incorporated modular designs. For example, some prior designs use
proximal bodies of varying height. Each of the proximal bodies are
configured to join to a distal stem of the implant at a middle
portion of the implant. Overall implant height adjustments are made
by selecting a proximal body that provides the desired implant
height, and then securing it to the distal stem segment. However,
there are several problems with these prior designs. For example,
the junction between the proximal body and the distal stem forms a
stress riser at a central portion of the implant, making the
implant more vulnerable to fatigue and shear under loading. Many of
these modular prior art devices are susceptible to fatigue failure.
Moreover, these prior implants can be difficult to assemble because
the junction is usually located inside the femoral canal and cannot
be easily seen. Lastly, each junction is subject to contamination
by bone debris, blood, or other biological matter that could
potentially prevent or interfere with establishing a good taper
lock at the junction, further increasing the risk of implant
failure.
[0009] Modular necks have also been used in the past to adjust
implant height. However, such conventional Cremascoli-type modular
necks (such as those used in PROFEMUR.RTM. implants by Wright
Medical Technology, Inc.) adjust implant height by changing the
overall neck length or the neck angle as shown in FIGS. 9a-9c. This
method disadvantageously changes offset and/or version angle
simultaneously with height, because of the way the sine and cosine
components of the neck change with changes in neck length (i.e.,
the hypotenuse) and angle. In an operating room, it can become
quite tedious and confusing to keep track of what geometries are
changing between neck segment selections during trial
reduction.
[0010] For example, the geometric changes between modular necks
(910, 920) of the prior art create spherical spatial paths (950) of
the femoral head center (912, 922) as they are interchangeably
assembled to a femoral stem (900). The spherical spatial paths
(950) cause some change in at least offset or version angle in
order to achieve a desired height. This is clearly shown in FIG.
9a. Therefore, to this end, if a surgeon wants to change the height
of an implant using prior art modular necks, he or she must make
compromises between leg length discrepancy and joint
stability/range-of-motion. Due to the complex and iterative nature
of changing more than one input variable at a time, it is difficult
for a surgeon to re-establish the proper joint stability when using
modular necks of the prior art, if leg length needs to be
adjusted.
[0011] Another way the prior art aims to address leg length is by
providing kits of non-modular implants have different proximal
geometries in order to adjust overall implant height. In hip
arthroplasty, these non-modular implants are sometimes referred to
as calcar-replacing femoral stems. The problem with using such
monolithic stems is that a surgeon needs to extract the entire
implant from the medullary canal and replace it with another
implant in order to change the overall implant height. Each time an
implant is inserted and extracted from a medullary canal, there is
trauma to the bone and surrounding soft tissues (e.g., increased
risk of fat embolism and/or fracture). Moreover, each time an
implant is inserted and extracted from a medullary canal, there may
be a loss of bone fixation or stability. Furthermore, each time an
implant is inserted and extracted from a medullary canal, rotation
needs to be re-set and there is no guarantee that the height will
be optimal when the implant is fully re-seated in the canal.
[0012] There remains a need in the art to provide an easy,
reliable, minimally-invasive method of adjusting the height of an
implant without unnecessary steps. There also remains a need in the
art to provide an easy, reliable method of adjusting the height of
an implant without compromising soft tissue and bone integrity.
There is also a need to reduce the number of trialing steps needed
to optimize performance and fit for a patient. There is also a
financial need to reduce the amount of time required for a hip
arthroplasty procedure. Moreover, there is a need to provide a
means for adjusting implant height without compromising the
structural integrity of said implant.
SUMMARY OF THE INVENTION
[0013] The aforementioned needs are satisfied by several aspects of
the present invention.
[0014] According to one aspect of the invention, there is provided
a system of modular orthopaedic devices. The system comprises one
or more hip implants or trials, each hip implant or trial having a
femoral stem and one of at least two neck segments having different
geometries. Each neck segment comprises a proximal end configured
to receive a femoral head portion and a distal end configured to be
operably received by a proximal portion of the femoral stem. Each
proximal end comprises a central portion generally representative
of a femoral head center. When each of the at least two neck
segments are joined with the femoral stem, the central portion is
displaced a predetermined distance in a single direction relative
to the femoral stem. The neck segments provided, therefore,
advantageously allow a user to independently adjust any one of a
height, an offset, or a version angle of an orthopaedic device for
best performance and fit.
[0015] According to yet another aspect of the invention, there is
provided a kit of modular neck segments. The kit allows a surgeon
to fine-tune leg length independently of offset and/or version
angle.
[0016] According to yet even another aspect of the invention, there
is provided a kit of modular neck segments. The kit allows a
surgeon to fine-tune implant offset independently of overall
implant height and/or version angle.
[0017] According to another aspect of the invention, there is
provided a kit of modular neck segments. The kit allows a surgeon
to fine-tune version angle independently of implant offset and/or
overall implant height.
[0018] According to yet another aspect of the invention, there is
provided a method of using the system of modular orthopaedic
devices discussed above. The method generally includes steps of: 1)
implanting a femoral stem of a hip implant or trial for best
cortical fixation, 2) selecting a first neck segment with a first
geometry, 3) assembling the first neck segment with the implanted
femoral stem, 4) assessing leg length, 5) if needed, removing the
first neck segment from the femoral stem and replacing it with one
or more second neck segments having one or more second geometries,
each of the one or more second geometries being configured to move
a femoral head center a predetermined distance in a
superior-inferior direction independently of offset and version
angle, 6) determining an optimum neck segment geometry which
provides the best overall height of the hip implant and leg length,
8) selecting, from a kit of neck segments having said optimum neck
segment geometry, a final neck segment having the proper offset or
version angle to obtain joint stability and acceptable range of
motion, 9) implanting a neck segment having the same geometry as
said final neck segment and finishing the surgical procedure as
conventionally done.
[0019] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating certain embodiments of the invention,
are intended for purposes of illustration only and are not intended
to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings, which are incorporated in and
form a part of the specification, illustrate the embodiments of the
present invention and together with the written description serve
to explain the principles, characteristics, and features of the
invention. In accordance with the invention there will be shown in
the drawings and described herein, more than one preferred
embodiment. These preferred embodiments are merely representative
of the invention and should not be construed as a limitation on the
scope of the present invention.
[0021] It will also be understood that like or analogous elements
and/or components, referred to herein, are identified throughout
the drawings by like reference characters. In addition, it will be
understood that the drawings are merely representations, and some
of the components may have been distorted from actual scale for
purposes of pictoral clarity. In the drawings:
[0022] FIGS. 1a and 1b are coronal views of a hip implant
comprising a femoral stem (100) and two superimposed neck segments
(200, 210) that allow independent adjustment of offset (510) in the
medial-lateral direction (500).
[0023] FIGS. 2a and 2b are sagittal views of the hip implant shown
in FIGS. 1a and 1b.
[0024] FIGS. 3a and 3b are coronal views of a hip implant
comprising a femoral stem (100) and two superimposed neck segments
(200, 220) that allow independent adjustment of offset (410) in the
superior-inferior direction (400).
[0025] FIGS. 4a and 4b are sagittal views of the hip implant shown
in FIGS. 3a and 3b.
[0026] FIGS. 5a and 5b are coronal views of a hip implant
comprising a femoral stem (100) and two superimposed neck segments
(200, 230) that allow independent adjustment of version (610) in
the anterior-posterior direction (600).
[0027] FIGS. 6a and 6b are sagittal views of the hip implant shown
in FIGS. 3a and 3b.
[0028] FIG. 7 shows one embodiment of the present invention which
comprises a kit (700) of modular neck segments for a femoral stem,
the kit allowing a surgeon to independently control height, offset,
and version angle of a hip implant.
[0029] FIG. 8 is a schematic illustrating a method of using the kit
(700) shown in FIG. 7 according to some embodiments.
[0030] FIGS. 9a-9c are examples of prior art modular neck segments
(910, 920) which do not allow independent adjustments of height,
offset, and version angle.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0031] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0032] Referring to the accompanying drawings, FIGS. 1a-2b
illustrate a system of modular orthopaedic devices according to
some embodiments. The system comprises a femoral stem (100) and one
of at least two neck segments (200, 210). The neck segments (200,
210) generally have a proximal end configured to receive a femoral
head implant (not shown), and a distal end configured to be
operably received by the femoral stem (100). The junction between
the neck segments (200, 210) may be any known in the art, but is
preferably a Morse taper lock. The proximal end of each neck
comprises a central portion (202, 212) which is representative of
the femoral head center when each of a femoral stem (100), neck
(200), and femoral head implant (not shown) are assembled
together.
[0033] One of said at least two neck segments may be a standard
neck segment (200) having a neutral referencing orientation. The
neutral referencing orientation may comprise, for instance, an
origin defined by a neutral height (410) in the superior-inferior
direction (400), a neutral offset (510) in the medial-lateral
direction (500), and a neutral version angle (610) in an
anterior-posterior direction (600). The other of said at least two
neck segments may be a high offset neck segment (210) having its
central portion (212) positioned with a higher offset (510) in a
medial-lateral direction (500) than the standard neck segment
(200). However, the high offset neck segment (210) generally
maintains the same neutral version angle (610) and height (410) as
the standard neck segment (200). The system of neck segments (200,
210) shown in FIGS. 1a-2b allows the surgeon to laterally or
medially displace a hip prosthesis for greater hip abduction and
motion without affecting leg length and
anteversion/retroversion.
[0034] It should be noted that in addition to the increased offset
neck segment (210) shown, multiple other neck segments yielding
different overall implant offsets may be included in the system.
For instance, a system of neck segments may comprise without
limitation, very high offset (high abduction), high offset
(abducted), very low offset (high adduction), and low offset
(adducted) neck segments, each having the same version angle (610)
and height (410), but each producing a different overall implant
offset (510) in the medial-lateral direction (500).
[0035] FIGS. 3a-4b illustrate a system of modular orthopaedic
devices according to some embodiments. The system comprises a
femoral stem (100) and one of at least two neck segments (200,
220). The neck segments (200, 220) generally have a proximal end
configured to receive a femoral head implant (not shown), and a
distal end configured to be operably received by the femoral stem
(100). The junction between the neck segments (200, 220) may be any
known in the art, but is preferably a Morse taper lock. The
proximal end of each neck comprises a central portion (202, 222)
which is representative of the femoral head center when each of a
femoral stem (100), neck (200), and femoral head implant (not
shown) are assembled together.
[0036] One of said at least two neck segments may be a standard
neck segment (200) having a neutral referencing orientation. The
neutral referencing orientation may comprise, for instance, an
origin defined by a neutral height (410) in the superior-inferior
direction (400), a neutral offset (510) in the medial-lateral
direction (500), and a neutral version angle (610) in an
anterior-posterior direction (600). The other of said at least two
neck segments may be an increased height neck segment (220) having
its central portion (222) positioned at a greater height (410) in a
superior-inferior direction (400) than the standard neck segment
(200). However, the increased height neck segment (220) generally
maintains the same neutral version angle (610) and offset (510) as
the standard neck segment (200). The system of neck segments (200,
220) shown in FIGS. 3a-4b allows the surgeon to superiorly or
inferiorly displace a hip prosthesis for proper leg length without
affecting abduction and anteversion/retroversion.
[0037] It should be noted that in addition to the increased height
neck segment (220) shown, multiple other neck segments yielding
different overall implant heights may be included in the system.
For instance, a system of neck segments may comprise without
limitation, very short (more distal), short (distal), very long
(more proximal), and long (proximal) neck segments, each having the
same version angle (610) and offset (510), but each producing a
different overall implant height (410) in the superior-inferior
direction (400).
[0038] FIGS. 5a-6b illustrate a system of modular orthopaedic
devices according to some embodiments. The system comprises a
femoral stem (100) and one of at least two neck segments (200,
230). The neck segments (200, 230) generally have a proximal end
configured to receive a femoral head implant (not shown), and a
distal end configured to be operably received by the femoral stem
(100). The junction between the neck segments (200, 230) may be any
known in the art, but is preferably a Morse taper lock. The
proximal end of each neck comprises a central portion (202, 232)
which is representative of the femoral head center when each of a
femoral stem (100), neck (200), and femoral head implant (not
shown) are assembled together.
[0039] One of said at least two neck segments may be a standard
neck segment (200) having a neutral referencing orientation. The
neutral referencing orientation may comprise, for instance, an
origin defined by a neutral height (410) in the superior-inferior
direction (400), a neutral offset (510) in the medial-lateral
direction (500), and a neutral version angle (610) in an
anterior-posterior direction (600). The other of said at least two
neck segments may be an anteverted neck segment (230) having its
central portion (232) positioned with a greater displacement (610)
in an anterior-posterior direction (600) than the standard neck
segment (200). However, the anteverted neck segment (230) generally
maintains the same neutral height (410) and offset (510) as the
standard neck segment (200). The system of neck segments (200, 230)
shown in FIGS. 5a-6b allows the surgeon to anteriorly or
posteriorly displace a hip prosthesis for proper
anteversion/retroversion without affecting abduction/adduction and
leg length.
[0040] It should be noted that in addition to the anteverted neck
segment (230) shown, multiple other neck segments yielding
different overall implant version angles may be included in the
system. For instance, a system of neck segments may comprise
without limitation, highly retroverted (more posterior), slightly
retroverted (posterior), highly anteverted (more anterior), and
slightly anteverted (anterior) neck segments, each having the same
height (410) and offset (510), but each producing a different
overall implant version angle (610) in the anterior-posterior
direction (600).
[0041] One of ordinary skill in the art would appreciate that the
abovementioned systems may be combined in any fashion to provide
numerous intra-operative options for a surgeon. For example, FIG. 7
illustrates a kit (700) which may be provided according to the
teachings disclosed herein. The kit (700) comprises a first group
(710) of at least two neck segments having different lengths. When
assembled with a femoral stem (not shown), each of said at least
two neck segments in said first group (710) yields a different
overall implant height. During trial reduction, a surgeon may use
the first group (710) of neck segments to assess and "lock-in" leg
length for the remainder of trial reduction. For instance, a
surgeon may determine that for a particular patient, a first
optimum neck segment geometry (712) will ensure a proper leg
length. Next, the surgeon will obtain a second group (720) of neck
segments from a series of groups (720, 730, 740). Each neck segment
contained in the second group (720) will posses the same first
optimum neck segment geometry (712), and thereby, ensure a proper
leg length. Finally, the surgeon will select a neck having a
version angle (722) and offset (724) that provides the best
stability and range of motion for a given first optimum neck
segment geometry (712). The order in which version angle (722) and
offset (724) are decided may vary according to surgeon
preference.
[0042] FIG. 8 is a schematic illustrating a method of using the
systems of modular orthopaedic devices discussed above. The method
may include steps of: implanting a femoral stem of a hip implant or
trial for best cortical fixation (802); selecting a first neck
segment with a first geometry (804); assembling the first neck
segment with the implanted femoral stem (806); assessing leg length
(808); if needed, removing the first neck segment from the femoral
stem and replacing it with one or more second neck segments having
one or more second geometries, each of the one or more second
geometries being configured to move a femoral head center a
predetermined distance in a superior-inferior direction
independently of offset and version angle (810); determining an
optimum neck segment geometry which provides the best overall
height of the hip implant and leg length (812); selecting, from a
kit of neck segments having said optimum neck segment geometry, a
final neck segment having the proper offset or version angle to
obtain joint stability and acceptable range of motion (814); and
implanting a neck segment having the same geometry as said final
neck segment and finishing the surgical procedure as conventionally
done (816).
[0043] Adjustment for intra-operative leg length discrepancies
without changing the offset and version of an implant is desirable,
because it may reduce the number of joint dislocations and the
number of revision surgeries due to leg length discrepancies.
Moreover, the ability to change implant height independently of
offset and version may reduce trial reduction time, thereby
decreasing hospital overhead and risks associated with extended
patient exposure (e.g., bacteria, anesthesia).
[0044] The present invention may advantageously utilized in
prostheses for other joints, such as shoulders. For example, the
femoral stems and femoral heads mentioned throughout this
disclosure may alternatively be humeral stems and humeral heads,
respectively. The present invention may be used selectively within
a particular product system, or universally across different
orthopedic product lines.
[0045] In some instances, the neck segments provided may be labeled
with indicia to indicate a geometric configuration. Such indicia
may be, for example, textual in form (e.g., "STANDARD" or "STD" or
"OFFSET" or "HIGH OFFSET"). Similarly, numbers may be provided on
the neck segments to indicate actual geometric displacements of the
femoral head center (e.g., the number "+10" near the word "OFFSET"
may indicate an increase in offset of 10 millimeters, whereas the
number "0" may indicate a neutral position). Indicia on neck
segments may specify any one of a height, an offset, or a version
angle, and may be formed by laser etching, printing, colorization,
engraving, molding, or rapid prototyping.
[0046] In some embodiments, all high offset neck segments within a
system may share a common symbol or color or both. In another
embodiment, all neck segments having the same height within a
system may share a common symbol or color or both. In yet another
embodiment, each standard offset neck segment within a system may
share a common symbol or color, or both. A banding system such as
ones used for resistors in the electronic arts may be employed so
as to provide easy recognition of values for height, offset, and
version. Indicia may be placed on the distal and/or proximal ends
of the modular neck segments to indicate proper or incorrect
orientation. For example, to ensure that a neck segment is not
inserted upside-down, indicia may be oriented in a way such that a
user can only properly read it when the neck segment is installed
in its correct orientation relative to the femoral stem. In some
instances, indicia may be in the form of a separate piece that
permanently connects with a modular neck segment, or in the form of
a sticker that may be removed from the neck segment and disposed
of.
[0047] Preferably, the distal portion of each neck segment of the
present invention comprises a Morse taper having an oval-tapered
cross section which mates with a corresponding oval-tapered hole in
a proximal stem portion. However, any alternative means for
connecting the modular neck segment may be used. Preferably, the
proximal end of each neck segment of the present invention
comprises a frustoconically-tapered surface that mates with a
corresponding frustoconically-tapered hole in a femoral head
component (not shown).
[0048] The proximal and distal end portions of each neck segment
within the system may be tapered or non-tapered and may be
configured for a press-fit. A transverse cross-section of the
proximal and distal ends of the neck segments may comprise conical,
square, elliptical, trapezoidal, or other polygonal shapes. The
proximal and distal end portions of each neck segment within the
system may also comprise splines, keys, registration elements, or
orientation features. The proximal and distal end portions of each
neck segment within the system may or may not be identical in shape
or size. In some embodiments, it may be favorable to make a femoral
head completely integral and/or monolithic with the neck segments
described herein.
[0049] The portion of the neck segments extending between the
proximal and distal end portions may have different shapes and may
be optimized for increased range of motion and decreased
impingement. The surface texture of the portion between the first
and second connection portions is preferably smooth, but may have a
textured or grit-blasted surface when provided as a trial for easy
handling. Trial neck segments described herein may be provided as
re-usable or disposable devices.
[0050] The neck segments of the present invention may connect
directly to a monolithic stem or to a modular stem. The present
invention may comprise as few or as many neck segments in a
selection as is needed to provide a user with the number of
configuration options desired. The neck segments may be custom-made
or custom-packaged for a pre-templated patient, so that fewer neck
segments are needed for trial reduction during a surgery for said
pre-templated patient. Any of the neck segments described herein
can be made of any material suitable for permanent or temporary
implantation into a human or animal including, but not limited to,
cobalt chrome, titanium, stainless steel, oxidized zirconium, PEEK,
and polyethylene.
[0051] In view of the foregoing, it will be seen that the several
advantages of the invention are achieved and attained.
[0052] The embodiments were chosen and described in order to best
explain the principles of the invention and its practical
application to thereby enable others skilled in the art to best
utilize the invention in various embodiments and with various
modifications as are suited to the particular use contemplated. It
must be noted that as used herein and in the appended claims, the
singular forms "a" "and," and "the" include plural references
unless the context clearly dictates otherwise.
[0053] As various modifications could be made in the constructions
and methods herein described and illustrated without departing from
the scope of the invention, it is intended that all matter
contained in the foregoing description or shown in the accompanying
drawings shall be interpreted as illustrative rather than limiting.
Thus, the breadth and scope of the present invention should not be
limited by any of the above-described exemplary embodiments, but
should be defined only in accordance with the following claims
appended hereto and their equivalents.
* * * * *