U.S. patent application number 17/704621 was filed with the patent office on 2022-07-07 for method of preparing joint prosthesis with infinitely positionable head.
The applicant listed for this patent is DePuy Synthes Products, Inc.. Invention is credited to Conrad Klotz, Jack Long.
Application Number | 20220211506 17/704621 |
Document ID | / |
Family ID | 1000006226891 |
Filed Date | 2022-07-07 |
United States Patent
Application |
20220211506 |
Kind Code |
A1 |
Klotz; Conrad ; et
al. |
July 7, 2022 |
Method of Preparing Joint Prosthesis With Infinitely Positionable
Head
Abstract
A method of preparing an assembly for a surgical procedure while
an implant is engaged with a bone includes mounting a first insert
component, configured to mount to the implant with a first
predetermined orientation, with a first mating component fixed
thereto in a replication instrument at a second predetermined
orientation, and determining an angular position of the provided
first mating component with respect to the first insert component
using the replication instrument. The first insert component and
the first mating component are removed from the replication
instrument and a second insert component configured to mount to the
implant with the first predetermined orientation is mounted in the
replication instrument at the second predetermined orientation and
the determined angular position is replicated with the mounted
second insert component and a second mating component.
Inventors: |
Klotz; Conrad; (Lutz,
FL) ; Long; Jack; (Warsaw, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DePuy Synthes Products, Inc. |
Raynham |
MA |
US |
|
|
Family ID: |
1000006226891 |
Appl. No.: |
17/704621 |
Filed: |
March 25, 2022 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
17064282 |
Oct 6, 2020 |
11298233 |
|
|
17704621 |
|
|
|
|
15895576 |
Feb 13, 2018 |
10828161 |
|
|
17064282 |
|
|
|
|
14842229 |
Sep 1, 2015 |
9925047 |
|
|
15895576 |
|
|
|
|
13874025 |
Apr 30, 2013 |
9132012 |
|
|
14842229 |
|
|
|
|
11025185 |
Dec 29, 2004 |
8444698 |
|
|
13874025 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2220/0033 20130101;
A61F 2250/0006 20130101; A61F 2002/4044 20130101; A61F 2/30
20130101; A61F 2002/4037 20130101; A61F 2002/30484 20130101; A61F
2220/0025 20130101; A61F 2/4603 20130101; A61F 2/4014 20130101;
A61F 2002/30538 20130101; A61F 2002/30614 20130101; A61F 2002/30884
20130101; A61F 2/4059 20130101; A61F 2002/30378 20130101; A61F
2002/4029 20130101 |
International
Class: |
A61F 2/30 20060101
A61F002/30; A61F 2/40 20060101 A61F002/40; A61F 2/46 20060101
A61F002/46 |
Claims
1. A method of preparing an assembly for a surgical procedure,
comprising: providing a first insert component with a first mating
component fixed thereto while an implant is engaged with the bone,
the first insert component configured to mount to the implant with
a first single predetermined orientation, and configured to mount
to a replication instrument with a second single predetermined
orientation; mounting the first insert component in the replication
instrument at the second single predetermined orientation;
determining an angular position of the provided first mating
component with respect to the first insert component using the
replication instrument; removing the first insert component and the
first mating component from the replication instrument; providing a
second insert component, the second insert component configured to
mount to the implant with the first single predetermined
orientation; mounting the second insert component in the
replication instrument at the second single predetermined
orientation; and replicating the determined angular position with
the mounted second insert component and a second mating
component.
2. The method of claim 1, wherein replicating the determined
angular position further comprises: press fitting a ball portion of
the second mating component within a tapered bore of the second
insert.
3. The method of claim 2, wherein replicating the determined
angular position further comprises: impacting the press fit ball
portion within the tapered bore using an alignment tool of the
replication instrument which was used to replicate the determined
angular position.
4. The method of claim 1, wherein mounting the first insert
component in the replication instrument comprises: positioning a
tab portion of the first insert component in a recess of the
replication instrument, the recess having a first opening portion
that opens to a platform surface at a proximal portion of the
replication instrument and a second opening portion that opens to a
side of the replication instrument extending away from the platform
surface.
5. The method of claim 4, wherein mounting the second insert
component in the replication instrument comprises: positioning a
tab portion of the second insert component in the recess of the
replication instrument.
6. The method of claim 5, wherein mounting the second insert
component in the replication instrument further comprises: securing
the second insert component to the replication instrument using a
fixation element partially inserted through a bore in the second
insert component.
7. The method of claim 6, wherein mounting the first insert
component in the replication instrument further comprises: securing
the first insert component to the replication instrument using the
fixation element partially inserted through a bore in the first
insert component.
8. The method of claim 5, further comprising: mounting an
articulating head component onto the second mating component.
9. The method of claim 8, wherein mounting the articulating head
component further comprises: impacting the articulating head
component onto the second mating component while the second insert
component is mounted in the replication instrument.
Description
[0001] This is a continuation of copending U.S. application Ser.
No. 17/064,282 filed Oct. 6, 2020, which issued as U.S. Pat. No.
11,298,233 on Apr. 12, 2022, which is a continuation of U.S.
application Ser. No. 15/895,576 filed Feb. 13, 2018, which issued
as U.S. Pat. No. 10,828,161 on Nov. 10, 2020 which is a divisional
application of U.S. application Ser. No. 14/842,229 filed Sep. 1,
2015, which issued as U.S. Pat. No. 9,925,047 on Mar. 27, 2018 and
which is a divisional application of U.S. application Ser. No.
13/874,025 filed Apr. 30, 2013, which issued as U.S. Pat. No.
9,132,012 on Sep. 15, 2015, which is a divisional of U.S.
application Ser. No. 11/025,185 filed Dec. 29, 2004 which issued as
U.S. Pat. No. 8,444,698 on May 21, 2013, the entire contents of
which are each herein incorporated by reference.
[0002] This application is related to U.S. Pat. No. 8,562,686 which
issued Oct. 22 2013.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to joint prosthesis, and
particularly to prosthesis having an articulating head component.
More specifically, the invention relates to a system for achieving
infinitely variable positions for the head component relative to a
bone engaging portion of the prosthesis.
[0004] Repair and replacement of human joints, such as the knee,
shoulder, elbow and hip, has become a more and more frequent
medical treatment. Longer life spans mean that the joints endure
more wear and tear. More sports activities mean greater likelihood
of serious joint injuries. Treatment of injuries, wear and disease
in human joints has progressed from the use of orthotics to mask
the problem, to fusion of the joint, to the use of prostheses to
replace the damaged joint component(s).
[0005] As the success rate for total or partial joint replacements
has increased, so too has the need for modularity and universality
in the joint prosthesis. Patient variety means that no single size
or configuration of joint prosthesis will suffice. The physical
dimensions of a patient's joint components vary, as well as the
bio-mechanic relationship between these components. For instance,
in a shoulder prosthesis, the relationship between the articulating
humeral and glenoid components can be significantly different
between patients. These relationships are especially important
where only one component of the joint is being replaced and must
integrate with the existing natural opposing joint component.
[0006] In joint replacement procedures, the proximal end of a bone,
such as the humerus, is resected to form a stable platform to
receive a joint implant. In some cases, it is discovered after the
implant has been fixed within the bone that the resection was
inappropriate for the patient's joint. Correction of this problem
requires, at a minimum, removal of the implant and implantation of
a new implant to fit the resected surface. The availability of a
differently sized or configured implant component is very
beneficial, and even more important where further resection of the
bone is necessary.
[0007] For instance, in many shoulder surgeries, only the humeral
component is replaced, leaving the glenoid component intact. In
this case, it is imperative that the articulating surface of the
humeral component match the articulating surface of the glenoid
component as perfectly as possible, both statically and
dynamically. With a typical humeral prosthesis, version and
inclination are adjusted by the geometry of the head of the
prosthesis. In other words, certain pre-determined head geometries
are available that can be selected for a mating glenoid component.
Absent an infinite variety of pre-determined head geometries, the
resulting humeral prosthesis can often only achieve a best-fit
relationship to the glenoid component of the shoulder joint.
[0008] In a typical surgical procedure, a trial component will be
used to determine the optimum final component to be fixed to the
bone. In most cases, the surgeon is able to make a good selection
that fits the joint very well. However, in some cases, the accuracy
of the fit cannot be determined until the surgery is completed and
the patient has had an opportunity to exercise the repaired joint.
Where significantly problems arise, a revision surgery may be
necessary to replace an improperly sized or configured joint
component. One typical revision surgery requires removal of the
entire prosthesis from the bone and replacement with a different
prosthesis.
[0009] There is a significant need for a joint prosthesis that is
both modular and universal. Such a prosthesis would be easily
manipulated during the surgery and capable of achieving nearly
infinite version and inclination angles. Moreover, an optimum
prosthesis would be readily available for modification in a
revision surgery without having to remove the entire
prosthesis.
SUMMARY OF THE INVENTION
[0010] These and other needs of the prior art are met by the
present invention in which a joint prosthesis includes a removable
component to which the articulating component of the prosthesis is
connected. The removable component permits adjustment of the
angular orientation of the articulating component so that the joint
prosthesis is truly universal.
[0011] In one aspect of the invention, the joint prosthesis
includes a component configured for engagement within the bone of a
patient, such as in a prepared intramedullary canal. The component,
or stem, can be configured as a trial stem or as a permanent
implant. The proximal end of the stem includes a platform surface
which defines features for removably supporting a removable insert
component. A fixation element is provided that is used to fix the
insert component to the stem. In accordance with one embodiment of
the invention, the fixation element is itself removable, although
it is capable of achieving substantially permanent, rigid fixation
of the insert component to the stem.
[0012] The joint prosthesis includes a mating component that has
one portion configured to mate with the articulating component and
another portion configured to adjustably mate with the insert
component. The mating component is also provided with a bore to
permit access to the fixation element when the mating component is
mated with the insert component, to allow removal of the fixation
element and thereby removal of the insert component from the stem
with the mating component intact.
[0013] In a specific embodiment of the invention, the insert
component includes a plate portion and a base portion projecting
from the plate portion. The insert component defines a tapered bore
therethrough and a fastener bore through the bottom wall of the
base portion. The platform surface of the stem defines an insert
cavity configured to receive the entire insert component therein.
In particular, the insert cavity includes a base recess into which
the insert base portion snugly fits, and a plate recess for
receiving the plate portion. Preferably, the plate recess is open
at one edge of the platform surface to facilitate access to the
plate portion of the insert component and ultimately to facilitate
dislodgement of the insert component from the insert cavity.
[0014] The mating component includes a ball portion that is
configured to form a press-fit within the tapered bore of the
insert component. The mating component also includes a tapered
cylinder configured to mate with a complementary bore defined in
the articulating component or head. Both ends of the mating
component are therefor configured for a press-fit engagement
accomplished by use of a typical impaction tool.
[0015] In accordance with a method of the present invention, a
joint prosthesis is constructed by placing an insert component into
a complementary configured cavity defined in the proximal portion
of a bone engaging implant, such as a stem. A fixation element,
such as a screw, is used to fix the insert within the stem. A
mating component is engaged with the insert component, such as by a
press-fit engagement between a tapered bore in the insert and a
compressible ball portion on the mating component. An articulating
component, such as a femoral head, is then mated with the mating
component, such as through a press-fit engagement.
[0016] In a further feature of the present invention, a revision
procedure includes the step of accessing the fixation element
through openings defined in at least the mating component. The
fixation element is released from engagement with the stem so that
the insert component is no longer fastened thereto. The insert
component is then removed, preferably with the mating component and
head components fastened undisturbed.
[0017] In yet another aspect, the removed insert component with the
undisturbed mating component and head component can be transported
to a replication instrument. The angular position of at least the
mating component may be ascertained relative to a fixed datum using
the instrument. That angular position can be conveyed to a new
insert and mating component using the instrument. Once the
three-dimensional angles have been properly replicated in the new
prosthesis components, the mating component can be fixed within the
insert component, preferably by impaction. The head component may
also be engaged to the mating component, also preferably by
impaction. The completed assembly is then conveyed to the stem that
has not been removed from the patient's bone. The insert component
is placed within the insert cavity in the stem and the fixation
element is used to rigidly connect the insert component to the stem
with the mating component and head component in their proper
anatomic relation to the patient's bone. These steps can be
implemented in a true revision surgery to replace an existing
prosthesis, or can be carried out during an original joint
replacement procedure.
[0018] In a further aspect, a method for preparing an articulating
component of a joint prosthesis having an implant engaged within a
bone of the joint includes inserting a first articulating component
into a first insert in the implant within the bone of the joint,
determining an angular orientation of the inserted first
articulating component relative to the implant within the bone of
the joint, positioning a second articulating component within a
second insert component, replicating the angular orientation of the
first articulating component in the second articulating component
positioned within the second insert, fixing the second articulating
component to the second insert component at the replicated angular
orientation, and mounting the second insert component with the
fixed second articulating component to the implant engaged within
the bone of the joint.
[0019] It is one object of the invention to provide a joint
prosthesis that is both modular and universal. This object is
achieved by features that permit infinitely variable positioning of
a mating joint component relative to a bone engaging portion of the
prosthesis.
[0020] Another object is to provide a prosthesis that is readily
available for modification, whether during initial implantation or
during a subsequent revision procedure. One benefit of the
invention is that this modification can occur without removing or
disturbing the bone engaging component, or stem, of the
implant.
[0021] These and other objects and benefits of the invention will
be appreciated upon consideration of the following written
description together with the accompanying figures.
DESCRIPTION OF THE FIGURES
[0022] FIG. 1 is a side view of a prior art humeral prosthesis.
[0023] FIG. 2 is an enlarged cross-sectional view of a portion of a
joint prosthesis with a mounting element configured for
articulating engagement with the stem of the prosthesis to permit
angular positioning of a head component in multiple degrees of
freedom.
[0024] FIG. 3 is a side exploded view of a modular prosthesis in
accordance with one embodiment of the present invention that is
adapted to facilitate modification or revision of the implant.
[0025] FIG. 4 is a front cross-section view of the modular
prosthesis shown in FIG. 3 in an assembled configuration.
[0026] FIG. 5 is a front perspective of a stem component of the
modular prosthesis shown in FIGS. 3-4.
[0027] FIG. 6 is an enlarged cross-section view of a portion of the
stem depicted in FIG. 5.
[0028] FIG. 7 is a top perspective view of an insert component of
the modular prosthesis illustrated in FIGS. 3-4.
[0029] FIG. 8 is a side cross-section view of the insert component
shown in FIG. 7.
[0030] FIG. 9 is a side cross-section view of a mating component of
the modular prosthesis shown in FIGS. 3-4.
[0031] FIG. 10 is a side view of a fixation component of the
modular prosthesis shown in FIGS. 3-4.
[0032] FIG. 11 is a side view of a replication instrument for use
in replicating the orientation of the mating component of the
prosthesis shown in FIGS. 3-4.
[0033] FIG. 12 is a perspective view of a dummy stem for use in the
replication instrument shown in FIG. 11.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] For the purposes of promoting an understanding of the
principles of the invention, reference will now be made to the
embodiments illustrated in the drawings and described in the
following written specification. It is understood that no
limitation to the scope of the invention is thereby intended. It is
further understood that the present invention includes any
alterations and modifications to the illustrated embodiments and
includes further applications of the principles of the invention as
would normally occur to one skilled in the art to which this
invention pertains.
[0035] The present invention contemplates a joint prosthesis with
an articulating component that must be positioned at a particular
angular orientation to replicate and accommodate anatomic features
of the patient's joint. In the following description, the
prosthesis is identified as a humeral prosthesis for a shoulder
implant. It is understood, however, that the principles of this
invention can be applied to other prosthesis that include an
adjustable component. The present invention is particularly suited
for prostheses that are amenable to replacement or adjustment in a
revision surgery.
[0036] By way of background, a typical joint prosthesis of the
prior art is illustrated in FIG. 1. The prosthesis 10 is the
humeral component of a shoulder prosthesis that can be implanted in
the humerus bone for articulating engagement with the natural
glenoid or with a glenoid prosthesis. The prosthesis 10 includes a
stem 12 configured to be implanted within the humerus bone in a
conventional manner. The stem 12 forms a platform surface 15 that
faces the glenoid component of the joint when the prosthesis is in
its operative position. The platform surface 15 defines a tapered
bore for use in mounting the articulating head component 14. The
head component includes a tapered post 18 that can be press-fit or
friction-fit within the tapered bore 16 to firmly mount the head
component to the stem 12.
[0037] The prosthesis 10 can be a modular prosthesis, meaning that
a number of stem and head geometries can be provided from which a
selection can be made that most closely approximates the natural
joint components of the patient. Thus, the angle of the platform
surface 15 can be different among stems 12. While all head
components 14 will include a generally spherical bearing surface
19, the orientation of this surface relative to the platform
surface 15 can be changed. Specifically, the location of the post
18 relative to the bearing surface 19 can be offset from the center
of the surface (i.e., an eccentric head). In some cases, the angle
of the post can be different between head components 14.
[0038] An improved modular prosthesis introduces an articulating
mounting element 30 between the stem 12 and a head component 20, as
shown in FIG. 2. This mounting element 30 is shown and described in
co-pending application Ser. No. 10/748,448 (the '448 Application),
entitled JOINT PROSTHESIS WITH INFINITELY POSITIONABLE HEAD, filed
on Dec. 30, 2003, and owned by the assignee of the present
invention. While the '448 Application provides a more detailed
disclosure of the mounting element, which disclosure is
incorporated herein by reference, following is a general
description to facilitate an understanding of the present
invention.
[0039] This mounting element 30 of the '448 Application includes a
proximal portion 33 that mates with the head component 20. In a
specific embodiment, the proximal portion 33 defines a tapered
surface that is press-fit or friction-fit within a complementary
bore 21 defined in the head component.
[0040] The mounting element 30 further includes an articulating
portion 34 that is preferably in the form of a spherical ball
joint. The articulating portion is sized to achieve a press-fit
engagement within a tapered bore 16 of the stem 12 when the portion
34 is pushed sufficiently far into the bore. The spherical shape of
the articulating portion 34 allows the mounting element 30 to
rotate about three dimensional axes x, y, z. Thus, the mounting
element can rotate about its own axis (the x axis), pivot about a
version axis (they axis) or pivot about an inclination axis (the z
axis).
[0041] In addition to the press-fit engagement, a second fixation
capability is disclosed in the '448 Application that augments the
engagement between the articulating portion 34 and the tapered bore
16. In particular, a machine screw 40 may be provided that includes
a threaded portion 46 configured to mate with a threaded bore 18 in
the stem 12. The bore 18 is concentrically disposed at the base of
the tapered bore 16. The screw 40 is introduced into the threaded
bore 18 through the articulating mounting element 30.
[0042] As shown in FIG. 2, the mounting element 30 defines a
central passageway 36 that extends through the length of element
and that is open at its proximal and distal ends. The passageway
defines an internal bearing surface 38 at the distal end of the
element, or more specifically at the base of the articulating
portion 34. The screw includes a head 42 that includes an underside
surface 44 that is complementary with the internal bearing surface.
These two surfaces form a spherical bearing interface that allows
the mounting element 30 to experience its full range of angular
motion without interference from the screw 40, even when the screw
is loosely threaded into the threaded bore 18. The articulating
portion 34 defines a relief 39 at the distal end of the passageway
36 to facilitate this full range of movement of the mounting
element.
[0043] The passageway 36 in the mounting element allows
introduction of the screw 40 through the mounting element and into
the threaded bore 18. The screw can be loosely threaded into the
bore to permit movement of the mounting element. Once the proper
position for the mounting element 30 has been achieved, the screw
can be tightened using a tool engaged within the tool recess 43 on
the head 42 of the screw. As the screw is tightened, it drives the
articulating portion 34 deeper into the angled bore 16, thereby
fixing the mounting element against further articulation. The screw
thus combines with the friction or press-fit feature to lock the
construct.
[0044] The mounting element 30 disclosed in the '448 Application
represents a significant improvement over the prior art prosthesis
10 in that it greatly simplifies the process of aligning the
mounting element, and ultimately the humeral head, at the proper
anatomic angle for the patient's shoulder joint. Moreover, the
mounting element 30 allows infinite positioning of the humeral
head, in lieu of the limited selection of pre-defined angles
available with the prosthesis of the prior art.
[0045] Even though the mounting element 30 presents a significant
advance over the prior prostheses, problems still arise when a
revision surgery is indicated. During some primary implant
procedures, the surgeon may discover that a different humeral head
is needed after the final implant stem has been fixed within the
humerus. In some cases, the accuracy of the fit of the prosthetic
components cannot be determined until the surgery is completed and
the patient has had an opportunity to exercise the repaired joint.
Where significant problems arise, a revision surgery may be
necessary long after the primary surgery to replace an improperly
sized or configured joint component. In most cases, the modular
components of the prosthesis cannot be removed without also
removing the component, or stem, fixed within the bone. Removal and
replacement of an implanted stem is often problematic and runs the
risk of creating a revision construct of poor integrity.
[0046] The present invention addresses the problem of revision
surgeries on prosthetic implants by providing an insert component
that allows the bone implanted component to remain within the bone.
In accordance with one embodiment of the invention, a prosthesis 50
is provided as illustrated in FIGS. 3-4 that includes a stem 52, an
insert component 54, a fixation element 56 and a mating component
58. The stem 52 is configured to be implanted within a bone of a
patient and may be identical in most respects to prior stems used
for similar joint replacement procedures. More particularly, the
portion of the stem 52 that is implanted within the prepared
intramedullary canal of the humerus may be identical to the prior
art stem 12 shown in FIG. 1. As with the prior art stems, the stem
52 includes a platform surface 60 that is aligned toward the mating
aspect of the joint, or the glenoid aspect in the case of a
shoulder prosthesis.
[0047] However, the platform surface 60 of the stem 50 in the
present invention takes on different characteristics from the prior
art. In particular, the platform surface is configured to receive
an insert component 54 and a fixation element 56 operable to
rigidly fix the insert component to the stem. The insert component
54 is adapted for engagement with the mating component 58 under
conditions that allow adjustment of the angular orientation of that
component. The mating component 58 is configured to receive an
articulating component, such as the humeral head 20 shown in FIG.
2.
[0048] Referring to FIGS. 5-6, details of the platform surface 60
of the stem 50 are illustrated. The platform surface defines an
insert cavity 62 with a base recess 64 embedded within the stem and
a plate recess 66 opening into the platform surface. As shown in
FIG. 5, the base recess 64 is preferably cylindrical, for ease of
manufacturing and to facilitate placement of the insert component
54 within the insert cavity 62. However, other cross-sectional
configurations for the base recess may be acceptable.
[0049] The plate recess 66 is generally rectangular with an edge 67
that opens at the superior end 61 of the platform surface 60. The
plate recess preferably includes a rounded inboard end to
facilitate manufacture of the recess 66. For instance, the base
recess 64 can be formed by drilling to a certain depth into the
platform surface 60 of the stem 52. The plate recess 66 can be
initially formed by drilling concentrically with the base recess,
but at a larger diameter and to a shallower depth. The platform
surface can then be milled to carve out the open edge 67 of the
plate recess.
[0050] The insert component 54 is configured to fit snugly within
the insert cavity 62, as can be seen from FIGS. 7-8. In particular,
the insert component includes a base portion 70 that is configured
to be snugly received within the base recess 64. Thus, the cross
section of the base portion preferably emulates the cross section
of the base recess--i.e., the base portion 70 is cylindrical in the
illustrated embodiment. The insert component further includes a
plate portion 72 that is also configured to be snugly received
within the plate recess 66. As with the base portion, the plate
portion 72 follows the configuration of the plate recess 66 so that
the base portion is generally rectangular with a rounded inner
edge. In the preferred embodiment, the plate portion 54 includes a
tab 80 that extends from the cylindrical base portion 70 so that
the free end 81 of the tab is accessible at the open edge 67 of the
plate recess. Preferably, the free end 81 is substantially
coincident with the open edge.
[0051] The plate portion 72 defines a lower surface 78 that rests
within the plate recess 66. The insert component is preferably
sized so that the base portion 70 is slightly offset from the
bottom wall 77 of the base recess 64 when the lower surface 78 of
the plate portion 72 is situated within the plate recess. The free
end 81 of the plate portion 72 includes a lower rounded edge 79 to
provide a small access for a removal tool between the insert
component and the insert cavity, as discussed in more detail
herein.
[0052] In one feature of the invention, the insert component 54
defines a tapered bore 74. The tapered bore mates in press-fit
engagement with engagement surface 85 of a ball portion 84 of the
mating component 58 (FIG. 9). This press-fit engagement
accomplishes final fixation of the mating component 58 with the
stem 52. This interface may be similar to the press-fit engagement
described in the '448 Application incorporated by reference. The
mating component preferably includes a tapered cylinder 82 that is
configured for press-fit engagement within the complementary bore
21 of the humeral head 20 (also shown in FIG. 2). The mating
component includes a central bore 87 that may be configured for a
press-fit engagement with a male feature on the humeral head, in
lieu of or in addition to the press-fit against the outer surface
of the tapered cylinder 82.
[0053] In order to secure the mating component to the stem 52, a
fixation element 56 is provided that fixes the insert component 54
to the stem. In the preferred embodiment, the insert cavity 62 of
the stem defines a threaded bore 68 in the base recess 64. The
fixation element 56 constitutes a screw, as shown in FIG. 10, with
a threaded stem 92 adapted to engage the threaded bore 68. The head
94 of the screw preferably includes a hex recess 96 for receiving a
hex driving tool of known design. The insert component 54 includes
a fastener bore 76 through the bottom wall 77 of the component to
receive the fastener therethrough. Thus, the insert component is
fixed to the stem 52 using the fixation element or screw 56, as
shown in FIG. 4. The ball portion 84 of the mating component 58
preferably defines a flared opening 89 to prevent contact between
the mating component and the head of the screw when the mating
component 58 is impacted within the tapered bore 74.
[0054] The fixation element 56 represents one beneficial feature of
the prosthesis 50 of the present invention. Specifically, the
fixation element allows removal of the insert component 54 from the
prosthesis stem 52 at any time, including when the mating component
56 is in solid engagement with the insert component. This feature
facilitates revision of the articulating component, or humeral
head, at any time by simply unscrewing the fixation element 56 from
the threaded bore 68 in the stem. When the fixation element 56 is
removed, the insert component 54 can be readily extracted from the
insert cavity 62 in the stem. Preferably, a tool can be pressed
between the rounded edge 79 of the tab portion 80 of the insert
component and the platform surface 60 of the stem to help dislodge
the insert without contacting the mating component 58. Once
removed, the insert component and mating component can serve as a
trial component that is replicated in a final prosthesis.
[0055] Whether as a final implant or a trial implant, when the
mating portion 58 is installed in the tapered bore 74, the ball
portion 84 may be initially loosely situated within the bore 74 so
that the angular orientation of the mating component 58 can be
adjusted. This adjustment may occur with the articulating head
component 20 mounted on the mating component. Once the proper
angles have been determined, the mating component can be fixed
within the tapered bore by impaction in a known manner, and the
humeral head can be added in a similar fashion. It can be
appreciated that since the mating component is engaging a removable
insert component 54 the impaction steps may occur apart from the
implant stem 52. Thus, the impaction of the mating component into
the insert component, and the impaction of the articulating head
onto the mating component can occur on a fixture. Rigid fixation of
the final implant may be accomplished through means other than
impaction, but this fixation may still occur apart from the stem
implanted within the patient's bone.
[0056] Preferably, the adjustment of the angular position of the
mating component for use in a final prosthesis can occur using a
replication instrument, such as the instrument disclosed in
co-pending application Ser. No. 10/879,261 (the '261 Application),
entitled INSTRUMENTATION FOR RECORDING AND REPLICATING ORTHOPAEDIC
IMPLANT ORIENTATION, owned by the assignee of the present
invention, the disclosure of which is incorporated herein by
reference.
[0057] While details of the instrument are found in the '261
Application, following is a general description of the instrument
100 as depicted in FIG. 11. In particular, the instrument includes
a base assembly 102 that carries a stationary clamp element 104 and
a movable clamp element 106. An adjustment mechanism 108 may be
manually operated to move the movable clamp element toward the
stationary element 104. The neck of the prosthesis stem 52 is
provided with positioning grooves 53a and 53b. The superior groove
53a accepts the fixed clamp element 104, while a pair of inferior
grooves 53b are configured to mate with the movable clamp element
106. When the neck of the stem is engaged by the clamp elements
104, 106, a fixed datum D is established that is perpendicular to
the platform surface 60. The spatial angular orientation of the
mating component 58 is gauged relative to this datum. The base
assembly 102 thus establishes a fixed spatial position for this
datum that can be used to replicate the angles of the mating
component.
[0058] To achieve this replication, the instrument 100 further
includes a replication fixture 110 that is mounted on the base
assembly 102. The fixture includes a platform 112 with legs 114
that are supported on the base assembly. The platform 110 includes
an annular dome 116 which supports a spherical washer 118 on one
surface and a cannulated guide member 120 on the opposite surface.
The guide member includes a hollow stem portion 121 that passes
through the dome 116 and washer 118. The stem portion 121 is
threaded to receive a locking nut 122 to fix the angular
orientation of the guide member 120 relative to the datum D.
[0059] As explained in more detail in the '261 Application, the
guide member 120 cannula allows passage of an alignment tool 125,
and more particularly the guide shaft 127 of the tool. The distal
end of the guide shaft is sized to fit snugly within the bore 87 of
the tapered cylinder 58. When the guide shaft 127 is situated
within the cylinder of the mating component used as part of the
trial assembly, the guide member 120 and spherical washer 118
assume a corresponding spatial angle relative to the dome 116. At
this point in the method, the locking nut is tightened, thereby
fixing the three-dimensional angular position of the guide member
120. The replication fixture 110 is then removed and stem 52 is
released from the base assembly. A final humeral prosthesis
configured as the prosthesis 50 shown in FIGS. 3-4 may then clamped
within the base assembly with a final mating element 58 loosely
engaged within the tapered bore 74 of a final insert component 54.
The alignment tool is reinserted into the guide member and the
guide shaft is engaged with the mating component to replicate the
angular orientation of the trial component. The alignment tool 125
is configured with an impaction end 129 that can be struck with a
mallet to impact the mating element into the insert component to
form the replicated final construct. Once the humeral head is
impacted onto the mating component, the insert component can be
positioned within the insert cavity 62 of a stem 52 implanted
within the prepared intramedullary canal of the patient's bone. The
insert component is then fixed in place using the fixation element
56.
[0060] As shown in FIG. 11, the replication instrument 100 engages
a prosthesis 50 that can be configured as a final or a trial
prosthesis. However, for the purposes of providing a baseline for
replicating the angular orientation of the articulating components
of the joint, an entire bone implant is not necessary. Thus, in an
alternative method for replicating the necessary angles, a dummy
prosthesis 150 is provided as shown in FIG. 12. The dummy
prosthesis 150 meticulously emulates the proximal portion of the
trial or final prosthesis 50 to provide the proper alignment of the
datum line D (FIG. 11). Thus, the dummy prosthesis includes a
truncated stem 152 that includes positioning grooves 153a, 153b
that are identical to the grooves 53a, 53b described above. These
dummy grooves are engaged by the clamp elements 104, 106, in the
manner described above. The proximal end of the dummy prosthesis
150 defines an insert cavity 162 with a base recess 164 and plate
recess 166, all configured to receive the insert component 54.
[0061] The dummy prosthesis 150 functions the same as a final or
trial prosthesis when mounted within the replication instrument
100. However, the dummy stem 152 does not require the features
found on an implantable stem, since the dummy prosthesis 150 is not
configured for implantation within the patient's bone. Preferably,
the stem 152 is about 1/3 the length of the final prosthesis stem
so that the dummy prosthesis is easy to manipulate and fix within
the replication instrument.
[0062] As explained above, the illustrated embodiment provides a
prosthesis for the humeral aspect of the shoulder joint. Thus, the
prosthesis 50 and its components are appropriately dimensioned for
implantation within the humerus bone of the patient. In a specific
embodiment, the base portion 70 of the insert component 54 has a
diameter of 0.5 inches and a height of 0.183 inches to fit within a
comparably dimensioned base recess 64. The plate portion 72 has a
width of 0.525 inches, a thickness of 0.1 inches, and an overall
length of 0.752 inches to fit within a plate recess 66 of the same
dimensions. The threaded stem 92 of the fixation screw 56 has a
length of 0.197 inches to pass through the bottom wall 77 of the
insert portion and into a bore 76 threaded to a depth of 0.175
inches. Preferably, the plate portion 72 of the insert is sized to
sit substantially flush with the platform surface 60 of the
prosthesis 50
[0063] Furthermore, the components of the prosthesis are formed of
acceptable medical grade materials appropriate for the particular
function being served by the components. For instance, the stem is
formed of a material appropriate for implantation within a prepared
intramedullary canal. The insert component and mating component are
formed of a biocompatible material appropriate for the mating
engagement between these components.
[0064] While the invention has been illustrated and described in
detail in the drawings and foregoing description, the same should
be considered as illustrative and not restrictive in character. It
is understood that only the preferred embodiments have been
presented and that all changes, modifications and further
applications that come within the spirit of the invention are
desired to be protected.
[0065] For instance, the mating interface between the insert
component and the mating component can be reversed. Specifically,
the tapered bore may be incorporated into the mating component,
while the ball portion projects from the insert component. The same
modification can be made to the mating interface between the
humeral head and the mating portion.
[0066] In the preferred embodiment, the fixation element is a
machine screw; however, other forms of fixation or fastening are
contemplated. For instance, rather than a screw that requires
multiple turns for complete fixation, the element can incorporate a
rotating locking cam or bayonet mount arrangement. As a further
alternative, the fixation element can incorporate a press-in
feature in which the element is pressed into the bore and locks in
place, such as a spring clip construction. The fixation element
must be capable of achieving a rigid attachment of the insert
component to the stem. Moreover, it is preferred that the fixation
element be capable of removal without disturbing or damaging the
implanted stem.
[0067] In accordance with the preferred embodiment of the
invention, the insert component is removable to facilitate revision
or replacement of the angularly adjustable components. In one
specific application, the insert component is implemented solely as
a trial implant wherein the insert component is removably fixed to
the stem to permit positioning of the mating component and femoral
head in a proper anatomic orientation. With the mating component
locked in its acceptable position, the insert component can be
removed and placed within a replication instrument. The orientation
of the mating component may then be replicated in a final
prosthesis that does not include the insert component.
[0068] The present invention provides advantages even if the insert
component is permanently fixed to the stem. Where the final implant
includes the insert component, the insert component may be
permanently fixed to the implanted stem with an appropriate
fixation element. This variation still takes advantage of the
ability to establish a final angular orientation of the mating
component outside the surgical site.
* * * * *