U.S. patent application number 12/162571 was filed with the patent office on 2009-02-19 for hip stem centralizer datum guide and method.
This patent application is currently assigned to ZIMMER TECHNOLOGY, INC.. Invention is credited to Bobby Chan, Kevin S. Cook, James L. Crumley, Stephen H. Hoag, Erin M. Johnson, Archie W. Newsome, Scott J. Steffensmeier.
Application Number | 20090048603 12/162571 |
Document ID | / |
Family ID | 38055096 |
Filed Date | 2009-02-19 |
United States Patent
Application |
20090048603 |
Kind Code |
A1 |
Hoag; Stephen H. ; et
al. |
February 19, 2009 |
HIP STEM CENTRALIZER DATUM GUIDE AND METHOD
Abstract
A hip stem centralizer datum guide (40, 100, 200, 300) and
method are provided for positioning a proximal portion of a hip
stem component (44) within bone cement in an intramedullary canal
of a femur. The datum guide is positionable in a predetermined
position relative to the intramedullary canal and is able to create
a datum (70, 72, 74, 76, 120, 220, 302) that records the
predetermined hip stem component position relative to the
intramedullary canal. The datum is able to be referenced to
position the hip stem component in the predetermined hip stem
component position in the bone cement in the intramedullary
canal.
Inventors: |
Hoag; Stephen H.; (Warsaw,
IN) ; Crumley; James L.; (Fort Wayne, IN) ;
Steffensmeier; Scott J.; (Warsaw, IN) ; Johnson; Erin
M.; (Columbia City, IN) ; Cook; Kevin S.;
(Warsaw, IN) ; Newsome; Archie W.; (Mentone,
IN) ; Chan; Bobby; (Warsaw, IN) |
Correspondence
Address: |
ZIMMER TECHNOLOGY - BAKER & DANIELS
111 EAST WAYNE STREET, SUITE 800
FORT WAYNE
IN
46802
US
|
Assignee: |
ZIMMER TECHNOLOGY, INC.
Warsaw
IN
|
Family ID: |
38055096 |
Appl. No.: |
12/162571 |
Filed: |
February 1, 2007 |
PCT Filed: |
February 1, 2007 |
PCT NO: |
PCT/US2007/061437 |
371 Date: |
August 26, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11346069 |
Feb 2, 2006 |
|
|
|
12162571 |
|
|
|
|
Current U.S.
Class: |
606/89 ; 606/102;
623/23.48 |
Current CPC
Class: |
A61F 2/30724 20130101;
A61F 2002/30168 20130101; A61F 2002/30963 20130101; A61F 2002/30795
20130101; A61F 2/32 20130101; A61F 2/4607 20130101; A61F 2/4684
20130101; A61F 2002/3625 20130101; A61F 2220/0033 20130101; A61B
17/1666 20130101; A61B 17/1659 20130101; A61F 2002/30617 20130101;
A61F 2/36 20130101; A61F 2230/0008 20130101; A61F 2/4657 20130101;
A61F 2250/0097 20130101; A61B 17/175 20130101; A61F 2/367 20130101;
A61F 2002/365 20130101; A61F 2002/4631 20130101; A61F 2002/4668
20130101; A61F 2002/4662 20130101; A61F 2/34 20130101; A61F
2002/30125 20130101; A61F 2002/30332 20130101; A61F 2002/3611
20130101; A61F 2002/4687 20130101; A61F 2230/0043 20130101 |
Class at
Publication: |
606/89 ; 606/102;
623/23.48 |
International
Class: |
A61B 17/90 20060101
A61B017/90; A61F 2/28 20060101 A61F002/28 |
Claims
1. In combination, a datum guide for establishing a datum on an
anatomical structure and a reference locator for referencing the
datum, comprising: a datum guide including at least one guide
element for creating the datum on the anatomical structure; and a
reference locator including at least one alignment reference
element for aligning with the datum.
2. The combination of claim 1, wherein the datum guide comprises a
rasp including a plurality of reference marks.
3. The combination of claim 1, wherein the reference locator
comprises a stem component of a prosthesis including a plurality of
alignment reference marks.
4. The combination of claim 1, wherein the datum guide comprises a
guide including a guide portion.
5. The combination of claim 4, wherein the guide portion includes a
cut slot.
6. The combination of claim 4, wherein the guide portion includes
at least one drill guide.
7. The combination of claim 1, wherein the reference locator
comprises a prosthesis inserter instrument including a protruding
tab.
8. The combination of claim 1, wherein the reference locator
comprises a prosthesis inserter instrument including at least one
pin.
9. The combination of claim 8, wherein the at least one pin is
integrally formed with the prosthesis inserter instrument.
10. The combination of claim 8, wherein the at least one pin is
separately formed with respect to the prosthesis inserter
instrument.
11. The combination of claim 8, wherein the prosthesis inserter
instrument further includes a sleeve including at least one pin.
Description
TECHNICAL FIELD
[0001] The present invention relates to total hip arthroplasty.
More particularly, the present invention relates to a proximal
centralizer for a cemented hip stem and a method for its use.
BACKGROUND
[0002] Total hip arthroplasty is often used to restore function to
a diseased or injured hip joint. Positions and directions relative
to the hip joint may be described in terms of proximal being nearer
the hip joint, distal being further from the hip joint, anterior
being nearer the front of the body, posterior being nearer the back
of the body, medial being nearer the centerline of the body, and
lateral being further from the center line of the body. In total
hip arthroplasty (FIGS. 1-2), the articular surfaces of the femur
and pelvis are cut away and replaced with prosthetic implant
components. In a typical case, the implants can include a hip stem
component 10, a femoral head component 12, an acetabular component
14, and bone cement 16. The hip stem component includes a stem
portion 18 extending down into the intramedullary canal 20 of the
femur 22 and a neck portion 24 extending away from the femur 22 to
support the femoral head component 12.
[0003] The femur 22 is prepared by reaming the intramedullary canal
20 down into the bone along an axis 26 from a proximal position
near the hip joint at the upper end of the femur 22 toward a distal
position nearer the knee joint at the lower end of the femur 22.
The pelvis 28 is prepared by reaming the acetabulum 30. Bone cement
16 is introduced into the prepared intramedullary canal 20 and
acetabulum 30 and the prosthetic components are seated in the bone
cement 16 so that it hardens around and locks the components in
place. Alternatively, the hip stem component 10 and the acetabular
component 14 may be positioned in intramedullary canal 20 and
acetabulum 30, respectively, without the use of cement. Positioning
the hip stem component 10 in the correct orientation within the
cement 16 is important for proper biomechanical functioning and
long term stability. It is desirable to have a uniform and strong
cement mantle 16 proximally and distally around the anterior 34,
lateral 36, posterior 38, and medial portions of the stem component
10. Proper placement further results in appropriate loading of the
implants.
SUMMARY
[0004] The present invention provides a hip stem centralizer datum
guide and method for positioning a proximal portion of a hip stem
component within bone cement in an intramedullary canal of a
femur.
[0005] In one aspect of the invention, a combination includes a
datum guide for being positioned in a predetermined position
relative to the intramedullary canal and for creating a datum that
records a predetermined hip stem component position relative to the
intramedullary canal. The combination is further capable of
referencing the datum to position the hip stem component in the
predetermined hip stem component position in the bone cement in the
intramedullary canal.
[0006] In another aspect of the invention, a combination includes a
datum guide and a hip stem inserter. The datum guide includes a
base positionable adjacent to the intramedullary canal in a
predetermined position relative to the intramedullary canal and a
cut guide mounted to the base. The cut guide is able to guide a
cutter to cut a datum into the proximal portion of the femur that
records a predetermined hip stem component position relative to the
intramedullary canal. The hip stem inserter is engageable with the
hip stem component in axial, medial/lateral, and anterior/posterior
force transmitting relationship. The hip stem inserter includes a
portion engageable with the datum. The hip stem inserter is
simultaneously engageable with the hip stem component and the datum
to position the hip stem component in the predetermined hip stem
component position in the bone cement in the intramedullary
canal.
[0007] In another aspect of the invention, a method includes
positioning a datum relative to the intramedullary canal; creating
a datum on the femur using the datum guide, the datum recording a
desired hip stem component position in persistent manner such that
the datum remains after the datum guide is removed; introducing
bone cement into the intramedullary canal; inserting the hip stem
component into the bone cement in the intramedullary canal; and
referencing the datum to position the hip stem component in the
desired position.
[0008] In one form, the present disclosure provides a combination
for establishing a datum on a femur and for referencing the datum
during implantation of a hip stem component into bone cement in an
intramedullary canal of the femur, the femur having a proximal
portion nearer the hip joint, a distal portion nearer the knee
joint, an anterior portion toward the front of the body, a
posterior portion toward the rear of the body, a medial portion
toward the midline of the body, and a lateral portion further from
the midline of the body, the datum being able to guide positioning
of the proximal portion of the hip stem component within the bone
cement to provide a predetermined bone cement thickness around the
hip stem component, the femur having a proximal portion including a
calcar region, a greater trochanter, and medial, lateral, anterior,
and posterior sides and the intramedullary canal defining a
longitudinal axis, the combination including a datum guide
including means for positioning the datum guide in a predetermined
position relative to the intramedullary canal; and means for
creating a datum that records a predetermined hip stem component
position relative to the intramedullary canal in persistent manner
such that the datum remains after the datum guide is removed; and
means for referencing the datum to position the hip stem component
in the predetermined hip stem component position in the bone cement
in the intramedullary canal.
[0009] The means for positioning the datum guide may include a rasp
having a shape corresponding to the shape of the hip stem component
and a cement mantle thickness around the implant, the rasp being
insertable into the intramedullary canal to form an opening to
receive the bone cement and the hip stem component, the rasp having
a proximal portion with reference marks able to guide forming
corresponding datum marks on the femur, the means for referencing
the datum comprising alignment marks formed on the proximal portion
of the hip stem component, the position of the alignment marks on
the hip stem component being related to the position of the marks
on the rasp to produce a hip stem component position corresponding
to a predetermined cement mantle thickness around the hip stem
component.
[0010] The means for creating a datum may include means for guiding
a cutter to cut a datum into the proximal portion of the femur and
wherein the means for referencing the datum comprises a hip stem
inserter engageable with the hip stem component in axial,
medial/lateral, and anterior/posterior force transmitting
relationship, the hip stem inserter comprising a portion engageable
with the datum, the hip stem inserter being simultaneously
engageable with the hip stem component and the datum. The means for
creating a datum may include means for guiding a cutter to cut a
proximal/distally oriented datum slot in the proximal femur and
wherein the inserter comprises a tab engageable with the datum slot
in axial sliding relationship. The means for creating a datum may
include a cut guide having a base engageable with the calcar region
of the proximal femur and a guide portion defining a cut guide slot
and extending upwardly at an angle from the base to position the
cut guide slot adjacent to the greater trochanter, the cut guide
slot being oriented to guide a cutter to form the proximal/distally
oriented datum slot in the greater trochanter.
[0011] The inserter tab may have anterior, posterior, lateral, and
distal surfaces, the anterior and posterior surfaces being
engageable with the datum slot to establish the anterior/posterior
position of the hip stem component, the lateral surface being
engageable with the datum slot to establish the medial/lateral
position of the hip stem component, and the distal surface being
engageable with the datum slot to establish the hip stem component
insertion depth.
[0012] The means for creating a datum may include means for guiding
a cutter to cut a datum hole in the proximal femur and a datum pin
insertable into the datum hole, the inserter comprising an opening
engageable with the datum pin to position the inserter and hip stem
component relative to the intramedullary canal of the femur.
[0013] The means for creating a datum may include a drill guide
having a base engageable with the calcar region of the proximal
femur and a drill guiding portion extending upwardly and laterally
from the base to position the drill guiding portion above the
greater trochanter, the drill guiding portion being oriented to
guide a drill to form a proximal/distally oriented datum hole in
the greater trochanter.
[0014] The inserter may include an extension projecting radially
outwardly and defining the opening engageable with the datum pin,
the opening extending into the extension to form an elongated
socket having a side wall and an end wall, the side wall being
engageable with the datum pin to establish the medial/lateral
position of the hip stem component and the end wall being
engageable with the datum slot to establish the hip stem component
insertion depth.
[0015] The means for creating a datum may include a drill guide
having a base engageable with the calcar region of the proximal
femur and a drill guiding portion extending upwardly at an angle
from the base to position the drill guiding portion adjacent to the
greater trochanter, the drill guiding portion defining a plurality
of drill guide bores oriented to guide a drill bit to form a
plurality of datum holes in the greater trochanter, the means for
creating a datum further comprising a plurality of datum pins
insertable into the plurality of datum holes, the inserter
comprising a plurality of openings engageable with the datum pins
to position the inserter and hip stem component relative to the
intramedullary canal of the femur.
[0016] The drill guide bores may be directed distally and laterally
to form datum holes oriented distally and laterally transverse to
the intramedullary canal axis.
[0017] The means for creating a datum may include a datum sleeve
defining a bearing surface having an axis, the datum sleeve being
mountable to the datum cut into the femur to position the bearing
surface in predetermined relationship to the intramedullary canal,
the hip stem inserter further comprising a portion engageable with
the bearing surface in axial sliding relationship.
[0018] The means for guiding a cutter may include a drill guide
having a base engageable with the calcar region of the proximal
femur and a drill guide portion extending upwardly at an angle from
the base to position the drill guide portion adjacent to the
greater trochanter, the drill guide portion defining a plurality of
drill guide bores oriented to guide a drill bit to form a plurality
of datum holes in the greater trochanter, the datum sleeve
including a plurality of legs engageable with the plurality of
datum holes.
[0019] The means for positioning the datum guide may include a
spigot engageable with the opening of the intramedullary canal.
[0020] In another form, the present disclosure provides a
combination for establishing a datum on a femur and for referencing
the datum during implantation of a hip stem component into bone
cement in an intramedullary canal of the femur, the femur having a
proximal portion nearer the hip joint, a distal portion nearer the
knee joint, an anterior portion toward the front of the body, a
posterior portion toward the rear of the body, a medial portion
toward the midline of the body, and a lateral portion further from
the midline of the body, the datum being able to guide positioning
of the proximal portion of the hip stem component within the bone
cement to provide a predetermined bone cement thickness around the
hip stem component, the femur having a proximal portion including a
calcar region, a greater trochanter, and medial, lateral, anterior,
and posterior sides and the intramedullary canal defining a
longitudinal axis, the combination including a datum guide
including a base positionable adjacent to the intramedullary canal
in a predetermined position relative to the intramedullary canal;
and a cut guide mounted to the base, the cut guide being able to
guide a cutter to cut a datum into the proximal portion of the
femur that records a predetermined hip stem component position
relative to the intramedullary canal in persistent manner such that
the datum remains after the datum guide is removed; and a hip stem
inserter engageable with the hip stem component in axial,
medial/lateral, and anterior/posterior force transmitting
relationship, the hip stem inserter comprising a portion engageable
with the datum, the hip stem inserter being simultaneously
engageable with the hip stem component and the datum to position
the hip stem component in the predetermined hip stem component
position in the bone cement in the intramedullary canal.
[0021] In yet another form thereof, the present disclosure provides
a method for guiding the positioning of the proximal portion of a
hip stem component within bone cement in an intramedullary canal of
a femur, the femur having a proximal portion nearer the hip joint,
a distal portion nearer the knee joint, an anterior portion toward
the front of the body, a posterior portion toward the rear of the
body, a medial portion toward the midline of the body, and a
lateral portion further from the midline of the body, the
intramedullary canal defining a longitudinal axis, the method
including the steps of positioning a datum relative to the
intramedullary canal; creating a datum on the femur using the datum
guide, the datum recording a desired hip stem component position in
persistent manner such that the datum remains after the datum guide
is removed; introducing bone cement into the intramedullary canal;
inserting the hip stem component into the bone cement in the
intramedullary canal; and referencing the datum to position the hip
stem component in the desired position.
[0022] The step of positioning a datum guide may include inserting
a rasp into the intramedullary canal to form an opening for
receiving the hip stem component and a surrounding layer of bone
cement, wherein creating a datum comprises transferring reference
marks from the rasp to the femur to form datum marks on the femur,
and wherein referencing the datum comprises aligning reference
marks formed on the hip stem component with the datum marks to
position the hip stem component within the bone cement.
[0023] The step of positioning a datum guide may include mounting a
datum guide adjacent to the proximal portion of the femur in known
relationship to the intramedullary canal, wherein creating a datum
comprises cutting a feature into the proximal femoral bone, and
wherein referencing the datum comprises coupling an inserter to the
hip stem component and engaging the inserter with the feature cut
into the bone to guide the inserter in known relationship to the
intramedullary canal to position the hip stem component within the
bone cement.
[0024] The step of positioning a datum guide may include mounting a
datum guide adjacent to the proximal portion of the femur in known
relationship to the intramedullary canal, wherein creating a datum
comprises inserting at least one pin into the proximal femoral
bone, and wherein referencing the datum comprises coupling an
inserter to the hip stem component and engaging the inserter with
the at least one pin to guide the inserter in known relationship to
the intramedullary canal to position the hip stem component within
the bone cement.
[0025] The step of creating a datum may include mounting a guide
sleeve adjacent to the proximal portion of the femur in known
relationship to the intramedullary canal and wherein referencing
the datum comprises coupling an inserter to the hip stem component
and engaging the inserter with the guide sleeve to position the hip
stem component within the bone cement.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Various examples of the present invention will be discussed
with reference to the appended drawings. These drawings depict only
illustrative examples of the invention and are not to be considered
limiting of its scope.
[0027] FIG. 1 is an anterior sectional view of a total hip
prosthesis implanted in a hip joint;
[0028] FIG. 2 is a sectional view taken along line 2-2 of FIG.
1;
[0029] FIG. 3 is a distal plan view of a datum guide in use to
establish a hip stem centralizer datum on a femur according to the
present invention.
[0030] FIG. 4 is a distal plan view of a hip stem being positioned
in an intramedullary canal using the datum of FIG. 3.
[0031] FIG. 5 is an anterior elevation view of a datum guide in use
to establish a hip stem centralizer datum on a femur according to
the present invention.
[0032] FIG. 6 is a medial elevation view of the datum guide of FIG.
5.
[0033] FIG. 7 is an anterior elevation view of a hip stem being
positioned in an intramedullary canal using the datum of FIG.
5.
[0034] FIG. 8 is a cross sectional view taken along line 8-8 of
FIG. 7.
[0035] FIG. 9 is an anterior elevation view of a datum guide in use
to establish a hip stem centralizer datum on a femur according to
the present invention.
[0036] FIG. 10 is a medial elevation view of the datum guide of
FIG. 8.
[0037] FIG. 11 is an anterior elevation view of a hip stem being
positioned in an intramedullary canal using the datum of FIG.
8.
[0038] FIG. 12 is an anterior elevation view of a datum guide in
use to establish a hip stem centralizer datum on a femur according
to the present invention.
[0039] FIG. 13 is a medial elevation view of the datum guide of
FIG. 11.
[0040] FIG. 14 is an anterior elevation view of a hip stem being
positioned in an intramedullary canal using the datum of FIG.
11.
[0041] FIG. 15 is an anterior elevation view of a datum sleeve
according to the present invention useable in combination with the
datum guides of FIGS. 5-13. The datum sleeve is shown in use to
position a hip stem in an intramedullary canal.
[0042] FIG. 16 is a medial elevation view of the datum sleeve of
FIG. 15.
[0043] FIG. 17 is a cross sectional view taken along line 17-17 of
FIG. 15.
DETAILED DESCRIPTION
[0044] Embodiments of a hip stem centralizer datum guide include a
body positionable adjacent to the proximal portion of a femur and
having a guide element for guiding the establishment of a datum on
the proximal femur. The datum is subsequently able to be referenced
to guide positioning of the proximal portion of a hip stem
component within the intramedullary canal of the femur. For
example, the datum guide may be used to establish a datum that
records a desired medial/lateral position, anterior/posterior
position, proximal/distal position, varus/valgus angle,
anteversion/retroversion angle, and/or other hip stem component
positioning parameter. The datum may be referenced upon insertion
of a hip stem component to position the hip stem component in the
desired recorded position. The datum may be referenced visually as
a visual alignment aid. The datum may be positively engaged to
physically constrain the insertion position. The datum may be
referenced by the hip stem component, by an insertion instrument,
and/or otherwise referenced. The datum guide facilitates creation
of a persistent datum that remains after the datum guide is removed
without requiring an additional implantable component and without
interrupting or reducing the contact area between the hip stem
component and bone cement within the intramedullary canal.
[0045] The body of the datum guide may be in the form of a rasp,
reamer, provisional implant, guide rod, dedicated datum guide body,
and/or other suitable body positionable adjacent to the proximal
portion of the femur. The body may be positionable adjacent to the
uncut proximal femur, on the cut surface of the proximal femur, in
the intramedullary canal, and/or otherwise positionable adjacent to
the proximal femur. For example, the body may engage portions of
the prepared calcar region of the bone, the greater trochanter, the
reamed intramedullary canal, and/or other portions of the proximal
femur. The body may be positioned by engaging it with another item
located adjacent to the proximal portion of the femur. For example,
the body may be positioned by engaging it with a reamer, rasp,
provisional implant, guide rod, and/or other suitable item. The
body may be made of metal, plastic, ceramic, and/or other suitable
materials.
[0046] The guide element may be in the form of reference marks,
cutter guides, slots, holes, and/or other suitable guide elements.
For example, a guide element in the form of reference marks may be
used to align a datum on the proximal femur such as reference
marks, slots, notches, holes, pins, and/or other suitable datum
formed on or inserted into the proximal femur. For example, a guide
element may take the form of reference marks on a rasp and/or
provisional implant that are used to guide the formation of
corresponding datum reference marks on the proximal femur. Similar
reference marks may be provided on the hip stem component such that
it may be positioned by aligning the reference marks on the hip
stem component with the datum reference marks formed on the bone.
The reference marks may be formed on the femur with a surgical pen,
electrocautery, bur, chisel, and/or other suitable marking
device.
[0047] The guide element may be in the form of a cutter guide for
guiding a cutter to form a datum on the bone. For example, the
cutter guide may be used to guide a saw blade, drill bit, mill,
chisel, and/or other suitable cutter. The datum formed may be in
the form of a slot, notch, hole, and/or other suitable datum. For
example, the guide element may guide a cutter to form a slot and/or
hole on the bone that is engaged by the hip stem component and/or
insertion instrument to position the hip stem component in a
desired position. The datum may be in the form of a pin, sleeve,
rail, and/or other suitable datum engaged with a feature cut into
the bone. For example, the guide element may guide a cutter to form
a slot and/or hole on the bone and the datum may include a pin
and/or sleeve inserted into the hole. The pin and/or sleeve may be
engaged by the hip stem component and/or insertion instrument to
position the implant in a desired position.
[0048] FIGS. 3-4 illustrate an exemplary hip stem centralizer datum
guide in the form of an intramedullary rasp 40 and a method for
positioning a proximal portion of a hip stem component 44 within an
intramedullary canal 46 of a femur 48. The rasp 40 includes a
proximal surface 50 defining an opening 52 and a post 54 engageable
with a handle (not shown) for inserting the rasp 40 into and
removing it from the intramedullary canal 46. The proximal surface
50 of the rasp 40 includes datum guide elements in the form of
reference marks 56, 58, 60, 62 positioned adjacent to its anterior,
posterior, medial, and lateral sides respectively. The femur 48
includes a greater trochanter 64 and a cut calcar surface 66. In
the illustrative example, the calcar surface 66 has been cut to
form a generally planar surface. The intramedullary canal 46 is
progressively rasped to form a cavity shaped for receiving the hip
stem component 44 and bone cement 68 (FIG. 4). When the final rasp
40 is seated, it defines the desired depth and orientation for the
hip stem component 44 relative to the intramedullary canal 46. The
reference marks 56, 58, 60, 62 are transferred to the calcar
surface 66 by forming corresponding datum marks 70, 72, 74, 76 on
the calcar surface 66 with a pen or other suitable means of marking
the calcar surface 66. Bone cement 68 is introduced into the
intramedullary canal 46 and the hip stem component 44 is inserted
into the bone cement 68. Insertion may be aided by engaging an
inserter (not shown) with an inserter hole 77 defined by the
proximal portion of the hip stem component 44. The hip stem
component 44 includes alignment reference marks 78, 80, 82 that are
aligned with the datum marks 70, 72, 76 to position the proximal
portion of the hip stem component 44 within the bone cement 68 at a
desired position relative to the intramedullary canal. Aligning the
hip stem component 44 with the datum marks 70, 72, 76 ensures
proper positioning relative to the final rasp 40 position and a
desired cement mantle 68 distribution around the hip stem component
44. Aligning the anterior and posterior alignment reference marks
78, 80 with the anterior and posterior datum marks 70, 72
establishes the medial lateral position of the hip stem component.
Aligning the lateral alignment reference mark 82 with the lateral
datum mark 76 establishes the anterior/posterior position of the
hip stem component 44. Alignment using all four datum 70, 72, 74,
76 establishes the version of the hip stem component 44. The
position of the alignment reference marks on the hip stem component
44 is related to the position of the reference marks on the rasp 40
to produce a predetermined desired bone cement mantle thickness.
The predetermined position of the hip stem component 44 relative to
the intramedullary canal 46 may be varied by varying the relative
position of the reference marks 56, 58, 60, 62 on the rasp 40 and
the alignment reference marks 78, 80, 82 on the hip stem component
44.
[0049] FIGS. 5-8 illustrate an exemplary hip stem centralizer datum
guide 100 and method for positioning a proximal portion of a hip
stem component 44 within an intramedullary canal 46 of a femur 48.
The datum guide 100 includes a body 102 having a guide portion 104,
and a base 106 alignable with the prepared intramedullary canal 46.
In the illustrative datum guide 100, the base 106 includes a distal
surface 108 that rests on the prepared calcar surface 66 and a
spigot 110 projecting distally below the distal surface 108 to
engage the opening of the prepared intramedullary canal 46 to
position the datum guide 100 relative to the intramedullary canal
46. The illustrative spigot 110 is continuous. However, it may be
discontinuous such as in the form of tabs, posts, and/or other
suitable form for engaging the intramedullary canal 46. The
illustrative base portion 106 engages the opening to the
intramedullary canal 46 directly. However, it may engage the
intramedullary canal 46 indirectly such as by mounting on another
member. For example, the base 106 may mount to the rasp 40 of FIG.
3 to position the datum guide 100 relative to the intramedullary
canal.
[0050] The illustrative base 106 is generally planar and the guide
portion 104 extends upwardly at an angle from the base 106 to form
a generally "L"-shaped body 102 (FIG. 5). The guide portion 104
includes a lateral surface 112 abuttable with a prepared medial
surface 114 of the greater trochanter 64. The angle between the
lateral surface 112 of the guide portion 104 and the distal surface
108 of the base 106 corresponds generally to the angle between the
prepared surfaces 66, 114 of the calcar and greater trochanter 64.
The guide portion 104 defines a cut guide slot 116 through the
guide portion 104 to guide a cutter in the form of a side cutting
mill 118.
[0051] In use, the femur is prepared by cutting the greater
trochanter 64, cutting the calcar surface 66, and reaming and
rasping the intramedullary canal 46 to receive the hip stem
component 44. The datum guide 100 is positioned relative to the
intramedullary canal 46, and the mill 118 is guided in cut guide
slot 116 to cut a notch 120 into the proximal femur 48. The cut
guide slot 116 has a width corresponding to the width of the mill
118. In the illustrative example, the datum guide 100 is used to
form a medially facing datum notch 120 in the greater trochanter 64
having a width corresponding to the mill 118 width. The datum notch
120 has a depth defined by a lateral side wall 121 (FIG. 7). The
depth of the datum notch 120 is controlled by a depth stop in the
form of a collar 117 extending radially outwardly from the mill
118. The collar 117 abuts a medial surface 119 of the guide portion
104 to limit the penetration of the mill 118 into the greater
trochanter 64. The datum notch 120 has a length defined by a distal
side wall 123 (FIG. 7). The length of the datum notch 120 is
controlled by the length of the cut guide slot 116. The mill 118
abuts a distal end 125 of the cut guide slot 116 to limit the
length of the datum notch 120.
[0052] The mill 118 and datum guide 100 are removed from the femur
48. Bone cement 68 is introduced into the intramedullary canal 46
and an inserter 122 is engaged with the hip stem component 44. The
inserter 122 includes a shaft 124 having a proximal end 126, a
distal end 128, and a longitudinal axis 129 extending between the
proximal and distal ends 126, 128. The distal end 128 engages the
inserter hole 77 in the proximal end of the hip stem component 44
in axial, medial/lateral, and anterior/posterior force transmitting
relationship such that when the inserter 122 is moved and tilted
medial/laterally the hip stem component 44 moves and tilts
medial/laterally and when the inserter 122 is moved and tilted
anterior/posteriorly the hip stem component 44 moves and tilts
anterior/posteriorly. The hip stem component 44 is inserted into
the bone cement 68 in the intramedullary canal 46 and pressed
distally with the inserter 122. As the hip stem component 44 nears
its final seated position, a datum engaging tab 130 projecting
laterally from the inserter shaft 124 engages the datum notch 120.
The tab 130 includes a proximal surface 132, a distal surface 134,
a lateral surface 136, and opposed anterior and posterior side
walls 138, 140 defining the tab width. The side walls 138, 140 are
spaced apart to define a close sliding fit of the tab 130 in the
datum notch 120 to set the anterior/posterior position of the hip
stem component. Abutting the distal surface 134 of the tab 130 with
the distal side wall 123 of the datum notch sets the insertion
depth of the hip stem component 44. Abutting the lateral surface
136 of the tab 130 with the lateral sidewall 121 of the datum notch
120 sets the medial/lateral position of the hip stem component 44.
Side walls 121, 123 may also be used to set the version of the hip
stem component 44 if walls 121, 123 are sufficiently dimensioned in
length. The predetermined position and depth of the datum notch 120
and consequently the position of the hip stem component 44 can be
varied relative to the intramedullary canal 46 by varying the
position of the guide slot 116, the length of the guide slot 116,
and/or the collar 117 position.
[0053] FIGS. 9-11 illustrate another exemplary hip stem centralizer
datum guide 200 and method for positioning a proximal portion of a
hip stem component 44 within an intramedullary canal 46 of a femur
48. The datum guide 200 and method of FIGS. 9-11 are similar to the
datum guide 100 and method of FIGS. 5-8. However, rather than
forming a datum notch 120 in the femur 48, a datum hole 220 is
formed in the femur 48 for receiving a datum pin 230. The
illustrative datum guide 200 includes a body 202, a base 204, and a
guide portion 206 generally configured like the example of FIG. 5.
However, the guide portion 206 includes a drill guide 208 extending
laterally over the greater trochanter 64. The drill guide 208
includes a proximal surface 210, a distal surface 212, and a guide
hole 214 through the drill guide 208 from the proximal surface 210
to the distal surface 212 along an axis 216. A drill bit 218 is
guided by the guide hole 214 to form the datum hole 220 in the
femur. In the illustrative example, the datum hole 220 is formed
proximal-to-distal in the greater trochanter. The depth of the
datum hole 220 is limited by a stop collar 222 projecting radially
from the drill bit 218 to abut the proximal surface 210 of the
drill guide 208. The datum pin 230 engages the datum hole 220 to
position the datum pin 230 in a desired medial/lateral and
anterior/posterior orientation relative to the intramedullary
canal. The datum pin 230 may be permanently attached to the
inserter 240 such that the datum pin 230 engages the datum hole
upon insertion of the hip stem component 44. Alternatively, and as
shown in FIG. 11, the datum pin 230 may be provided separate from
the inserter 240 and pre-positioned in the datum hole 220 prior to
insertion of the hip stem component.
[0054] The datum pin 230 includes proximal end 232, a distal end
234, and a longitudinal axis 236 extending between the proximal and
distal ends 232, 234. The distal end 234 forms a close sliding fit
with the datum hole 220 such that it is insertable axially into the
datum hole 220 to orient the datum pin 230 coaxially with the datum
hole 220. The distal end 234 of the datum pin 230 rests on the
bottom of the datum hole 220 and the proximal end 232 of the datum
pin 230 extends proximally a predetermined height relative to the
intramedullary canal 46.
[0055] The inserter 240 includes a shaft 242 having a proximal end
244, a distal end 246, and a longitudinal axis 248 extending
between the proximal and distal ends 244, 246. A datum engaging tab
249 projects radially outwardly from the shaft 242 and defines a
socket 250 with a closed proximal end wall 252 and a distal opening
254. The socket 250 receives the datum pin 230 in close axial
sliding relationship to orient the inserter 240 relative to the
datum pin 230. The engagement of the socket 250 with the datum pin
230 spaces the inserter 240, and consequently the hip stem
component 44, medial/laterally and anteriorly/posteriorly in a
predetermined position relative to the intramedullary canal as
established by the datum guide 200. The axis 236 of the datum pin
230 is generally parallel to the insertion axis 248 such that the
datum pin 230 guides the hip stem component 44 along the insertion
axis 248.
[0056] The illustrative datum pin 230 and socket 250 have round
cross sections such that the inserter 240 can rotate about the
datum pin 230 and permit the user to establish the
anterior/posterior position of the hip stem component manually such
as by visualizing the cement mantle thickness anteriorly and
posteriorly. Alternatively, the datum pin 230 and socket 250 may be
rotationally keyed such as with grooves, tabs, splines,
non-circular cross sections, and/or other rotational keying
mechanisms such that the datum pin 230 and socket 250 also
establish the anterior/posterior position and version of the hip
stem component 44. The datum pin 230 abuts the proximal end wall
252 of the socket 250 to set the depth of the hip stem component
44. The predetermined depth of the hip stem component 44 may be
varied by varying the depth of the datum hole 220, the depth of the
socket 250, and/or the length of the datum pin 230. Alternatively,
the socket 250 may be formed through the tab 249 so that the datum
pin does not bottom and the hip stem component 44 depth can be set
using other depth setting features. The predetermined
medial/lateral and anterior/posterior position of the hip stem
component 44 may be varied by varying the position and orientation
of the guide hole 214 relative to the intramedullary canal 46 and
the position and orientation of the socket 250 in the tab 249. In
the illustrative method, the datum hole 220 is predrilled and the
datum pin 230 is subsequently inserted into the datum hole 220.
Alternatively, the datum pin 220 may be guided directly by the
guide portion 206 to simultaneously insert the datum pin 230 and
form the datum hole 220.
[0057] FIGS. 12-14 illustrate another exemplary hip stem
centralizer datum guide 300 and method for positioning a proximal
portion of a hip stem component 44 within an intramedullary canal
46 of a femur 48. The datum guide 300 and method of FIGS. 12-14 are
similar to the datum guide 200 and method of FIGS. 9-11. However,
rather than forming a datum hole 220 distally into the greater
trochanter 64, a plurality of datum holes 302 are formed at an
angle into the medial cut surface 114 of the greater trochanter 64.
In the illustrative example, three datum holes 302 are formed in a
triangular hole pattern. A drill guide portion 304 of the datum
guide 300 includes guide holes 306 to guide a drill bit 308 to form
the datum holes 302. Datum pins 310 are engaged with the datum
holes 302 to establish a hip stem component 44 seating datum
relative to the intramedullary canal 46. An inserter 312 includes
an insertion axis 313 and further includes notches 314 for engaging
the datum pins 310 to establish the medial/lateral position,
anterior/posterior position, and depth of the hip stem component 44
relative to the intramedullary canal. The datum holes 302 are
formed transverse to the insertion axis 313 such that the inserter
312 and hip stem component 44 move distally and laterally as the
inserter engages the datum pins 310. Notches 314 may be formed in a
distal to proximal direction to allow insertion of datum pins 310
into notches 314. In the illustrative method, the datum holes 302
are predrilled and the datum pins 310 are subsequently inserted
into the datum holes 302. Alternatively, the datum pins 310 may be
guided directly by the guide portion 304 to simultaneously insert
the datum pins 310 and form the datum holes 302.
[0058] FIGS. 15-17 illustrate a datum in the form of a datum sleeve
400 configured for engagement with the datum holes 302 of FIGS.
12-14. The datum sleeve 400 includes a sleeve 402 having a convex
outer surface 404, a concave inner bearing surface 406, a proximal
end 408 and a distal end 410 oriented along a longitudinal axis
412. The inner surface 406 includes a lateral portion 414, an
anterior portion 416, and a posterior portion 418. The sleeve 402
includes a medial opening 419 defined by an open medial side from
the proximal end 408 to the distal end 410. An outrigger 420
extends from the sleeve 402 and includes an anterior leg 422, a
posterior leg 424, and a lateral leg 426. All three legs extend
laterally and distally from the sleeve parallel to one another for
insertion into the datum holes 302. With the outrigger legs 422,
424, 426 inserted into the datum holes 302 the sleeve 402 is
supported with its inner surface 406 at a desired orientation
relative to the intramedullary canal 46 of the femur 48. An
inserter 430 includes a longitudinal shaft 432 having a
longitudinal axis 434. The inserter shaft 432 is received in the
sleeve 402 in axial sliding arrangement. As the hip stem component
44 is inserted into the intramedullary canal 46, the inserter shaft
432 is moved laterally through the sleeve opening 419 to engage the
shaft 432 with the lateral, anterior, and posterior portions 414,
416, 418 of the inner surface 406. The lateral portion 414 spaces
the shaft 432 and consequently the hip stem component 44 a
predetermined distance from the lateral side of the intramedullary
canal 46. The anterior and posterior portions 416, 418 position the
shaft 432 and hip stem component 44 anterior/posteriorly relative
to the intramedullary canal 46. The shaft 432 may optionally
include a depth stop (not shown) for abutting against the proximal
end 408 of the sleeve to set the hip stem component 44 insertion
depth. The illustrative sleeve 402 receives the shaft 432 in close
sliding relationship anteriorly and posteriorly (FIG. 17) such that
the shaft 432 position is closely constrained anterior/posteriorly.
The shaft 432 can move in and out of the sleeve 402 through the
medial opening 419. However, positioning the shaft 432 against the
lateral portion 414 of the sleeve 402 sets the medial/lateral
position. In alternative embodiments, the sleeve may form a
complete ring (not shown) fully enclosing the shaft 432 such that
the shaft 432 and sleeve 402 are inserted together. In this
alternative embodiment, as the hip stem component 44 is inserted
into the intramedullary canal 46, the legs 422, 424, 426 are
inserted into the datum holes 302 to position the hip stem
component 44 relative to the intramedullary canal 46. In an
alternative embodiment, shaft 432 and sleeve 402 may be rectangular
in cross-sectional shape to allow control of version of hip stem
component 44. The illustrative datum sleeve 400 has been shown
configured to engage the datum holes 302 created with the datum
guide 300 of FIGS. 12-14. However, the datum sleeve 400 may be
configured to engage the datum hole 220 created with the datum
guide 200 of FIGS. 9-11, the datum notch 120 created with the datum
guide 100 of FIGS. 5-8, and/or configured to engage other suitable
datums.
[0059] Although examples of a hip stem centralizer datum guide and
its use have been described and illustrated in detail, it is to be
understood that the same is intended by way of illustration and
example only and is not to be taken by way of limitation. The
invention has been illustrated in use to create datums on the
calcar and greater trochanter of the femur to space a hip stem
component from the lateral side of the intramedullary canal during
hip replacement surgery. The hip stem centralizer datum guide has
also been illustrated in use to space the hip stem component
anterior/posteriorly in the intramedullary canal and further it has
been illustrated to set the depth of insertion of the hip stem
component. However, the hip stem centralizer datum guide may be
configured to create datums at other locations and to set other
parameters of hip stem positioning. Accordingly, variations in and
modifications to the hip stem centralizer datum guide and its use
will be apparent to those of ordinary skill in the art, and the
following claims are intended to cover all such modifications and
equivalents.
* * * * *