U.S. patent application number 09/904752 was filed with the patent office on 2002-02-07 for device and method for positioning an eccentric humeral head of a humerus prothesis for a shoulder arthroplasty.
Invention is credited to Coon, Michael, Durniak, Todd, Iannotti, Joseph, Maroney, Brian, Ondrla, Jeffrey, Williams, Gerald.
Application Number | 20020016634 09/904752 |
Document ID | / |
Family ID | 22828744 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020016634 |
Kind Code |
A1 |
Maroney, Brian ; et
al. |
February 7, 2002 |
Device and method for positioning an eccentric humeral head of a
humerus prothesis for a shoulder arthroplasty
Abstract
A kit and associated method is disclosed for implanting a
prosthetic device in a resected bone such as a humerus. The kit
includes a trial assembly including a trial body portion having a
trial bore defined therein, and a trial head portion having (i) a
trail head member which includes a trial offset indicia, and (ii)
an eccentrically located trial stem extending from the trial head
member, the trial head stem being configured to be received within
the trial bore. The kit also includes a final prosthesis assembly
including a final body portion having a final bore defined therein,
and a final head portion having (i) a final head member which
includes a final offset indicia, and (ii) an eccentrically located
final head stem extending from the final head portion, the final
head stem being configured to be received within the final
bore.
Inventors: |
Maroney, Brian; (Ft. Wayne,
IN) ; Coon, Michael; (Warsaw, IN) ; Ondrla,
Jeffrey; (Leesburg, IN) ; Durniak, Todd; (Ft.
Wayne, IN) ; Iannotti, Joseph; (Bentleyville, OH)
; Williams, Gerald; (Villanova, PA) |
Correspondence
Address: |
Paul J. Maginot
Maginot, Addison & Moore
Bank One Center/Tower
111 Monument Circle, Suite 3000
Indianapolis
IN
46204-5115
US
|
Family ID: |
22828744 |
Appl. No.: |
09/904752 |
Filed: |
July 13, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60221657 |
Jul 28, 2000 |
|
|
|
Current U.S.
Class: |
623/19.14 ;
623/22.42 |
Current CPC
Class: |
A61F 2/4014 20130101;
A61F 2002/4051 20130101; A61B 17/1684 20130101; A61F 2250/0089
20130101; A61F 2250/0097 20130101; A61F 2002/4018 20130101; A61B
17/1659 20130101; A61F 2002/30827 20130101; A61F 2002/30902
20130101; A61F 2250/0064 20130101; A61F 2/4657 20130101; A61F
2002/4077 20130101; A61F 2/4684 20130101; A61F 2002/30616 20130101;
A61F 2002/3071 20130101; A61F 2002/30617 20130101; A61F 2002/4062
20130101; A61F 2002/30332 20130101; A61F 2002/4681 20130101; A61F
2002/30884 20130101; A61F 2220/0033 20130101 |
Class at
Publication: |
623/19.14 ;
623/22.42 |
International
Class: |
A61F 002/40 |
Claims
What is claimed is:
1. A method of implanting a final prosthesis assembly in a resected
bone, comprising the steps of: positioning a trial assembly in said
resected bone, said trial assembly including a trial body portion
having a trial bore defined therein, and a trial head portion
having (i) a trial head member which includes a trial offset
indicia, and (ii) an eccentrically located trial head stem
extending from said trial head member, said trial head stem being
configured to be received within said trial bore; rotating said
trial head portion relative to said trial body portion while said
trial assembly is positioned in said resected bone so as to
position said trial head portion relative to said trial body
portion at an aligned orientation whereby said trial head portion
covers a resected surface of said resected bone; removing said
trial assembly from said resected bone after said rotating step;
positioning said trial assembly in a scale mechanism whereby said
trial offset indicia of said trial head portion aligns with a value
on said scale mechanism; securing a final head portion to a final
body portion based on said value so as to form said final
prosthesis assembly; and implanting said final prosthesis assembly
in said resected bone after said securing step.
2. The method of claim 1, further comprising the step of securing
said trial head portion to said trial body portion when said trial
head portion is positioned relative to said trial body portion at
said aligned orientation.
3. The method of claim 2, wherein: said trial body portion includes
a set of internal threads located within said trial bore, said
trial head portion further includes an externally threaded fastener
positioned within a passageway which extends through said trial
head portion, and said securing step includes the step of advancing
said externally threaded fastener into meshing engagement with said
set of internal threads so as to secure said trial head portion in
fixed relation to said trial body portion.
4. The method of claim 1, wherein: said trial body portion includes
(i) a trial body stem, (ii) a neck attached to said trial body
stem, and (iii) a flat attached to said neck, and said trial bore
extends through said flat and into said neck.
5. The method of claim 1, wherein: said scale mechanism includes an
indicia surface, and said value is identified on said indicia
surface.
6. The method of claim 5, wherein: said indicia surface possesses
markings which depict a clock which is divided into a plurality of
sections, and said value is identified on one of said plurality of
sections.
7. The method of claim 5, wherein: said scale mechanism includes a
channel defined therein, and said trial assembly positioning step
includes the step of locating said trial body portion within said
channel.
8. The method of claim 7, wherein: said trial body portion locating
step includes the step of locating said trial head portion adjacent
to said indicia surface.
9. The method of claim 1, wherein said final head portion includes
(i) a final head member having a final offset indicia, and (ii) an
eccentrically located final head stem extending from said final
head member.
10. The method of claim 9, wherein: said final head stem possesses
a male taper configuration, said final body portion has a final
bore defined therein, said final bore possesses a female taper
configuration, and said attaching step includes the step of
advancing said final head stem into said final bore in a friction
fit manner.
11. The method of claim 9, wherein: said scale mechanism includes
an indicia surface, said value is indicated on said indicia
surface, said scale mechanism further includes a channel define
therein, and said attaching step includes locating said final body
portion within said channel.
12. The method of claim 11, wherein said attaching step further
includes locating said final head portion adjacent to said indicia
surface.
13. The method of claim 12, wherein said attaching step further
includes positioning said final head portion relative to said final
body portion at said aligned orientation.
14. The method of claim 13, wherein said step of positioning said
final head portion relative to said final body portion includes the
step of aligning said final offset indicia with said value
identified on said indicia surface.
15. The method of claim 9, wherein: said trial offset indicia
includes a notch defined in a surface of said trial head member,
and said final offset indicia includes a removable sticker
positioned on said final head member.
16. The method of claim 1, wherein said resected bone is a resected
humerus.
17. A method of implanting a final prosthesis assembly in a
resected bone, comprising the steps of: providing a trail assembly
which includes a trial body portion having a trial bore defined
therein, and a trial head portion having (i) a trial head member
which includes a trial offset indicia, and (ii) an eccentrically
located trial head stem extending from said trial head member;
positioning said trial body portion in said resected bone;
positioning said trial stem in said trial bore after said trial
body positioning step; moving said trial head portion in relation
to said trial body portion after said trial stem positioning step
so as to locate said trial head portion relative to said trial body
portion at a user-selected orientation; securing said trial head
portion to said trial body portion at said user-selected
orientation; removing said trial assembly from said resected bone
after said securing step; positioning said trial assembly in a
scale mechanism after said removing step whereby said trial offset
indicia of said trial head portion aligns with a value on said
scale mechanism; attaching a final head portion in fixed relation
to a final body portion based on said value so as to form said
final prosthesis assembly; and implanting said final prosthesis
assembly in said resected bone after said attaching step.
18. The method of claim 17, wherein: said trial body portion
includes a set of internal threads located within said trial bore,
said trial head portion further includes an externally threaded
fastener positioned within a passageway which extends through said
trial head portion, and said securing step includes the step of
advancing said externally threaded fastener into meshing engagement
with said set of internal threads so as to secure said trial head
portion in fixed relation to said trial body portion.
19. The method of claim 17, wherein: said trial body portion
includes a (i) a trial body stem, (ii) a neck attached to said
trial body stem, and (iii) a flat attached to said neck, and said
trial bore extends through said flat and into said neck.
20. The method of claim 17, wherein: said scale mechanism includes
an indicia surface, and said value is identified on said indicia
surface.
21. The method of claim 20, wherein: said indicia surface possesses
markings which depict a clock which is divided into a plurality of
sections, and said value is identified on one of said plurality of
sections.
22. The method of claim 20, wherein: said scale mechanism includes
a channel defined therein, and said trial assembly positioning step
includes the step of locating said trial body portion within said
channel.
23. The method of claim 22, wherein said trial body portion
locating step includes the step of locating said trial head portion
adjacent to said indicia surface.
24. The method of claim 17, wherein: said final head portion
includes (i) a final head member having a final offset indicia, and
(ii) an eccentrically located final head stem extending from said
final head member, said final head stem possesses a male taper
configuration, said final body portion has a final bore defined
therein, said final bore possesses a female taper configuration,
and said attaching step includes the step of advancing said final
head stem into said final bore in a friction fit manner.
25. The method of claim 24, wherein: said scale mechanism includes
an indicia surface, said value is indicated on said indicia
surface, said scale mechanism further includes a channel define
therein, and said attaching step includes the steps of (i) locating
said final body portion within said channel, (ii) positioning said
final head portion relative to said final body portion so that said
final offset indicia is aligned with said value identified on said
indicia surface.
26. The method of claim 24, wherein: said trial offset indicia
includes a notch defined in a surface of said trial head member,
and said final offset indicia includes a removable sticker
positioned on said final head member.
27. The method of claim 17, wherein said resected bone is a
resected humerus.
28. A kit, comprising: a trial assembly including a trial body
portion having a trial bore defined therein, and a trial head
portion having (i) a trail head member which includes a trial
offset indicia, and (ii) an eccentrically located trial stem
extending from said trial head member, said trial head stem being
configured to be received within said trial bore; and a final
prosthesis assembly including a final body portion having a final
bore defined therein, and a final head portion having (i) a final
head member which includes a final offset indicia, and (ii) an
eccentrically located final head stem extending from said final
head portion, said final head stem being configured to be received
within said final bore.
29. The kit of claim 28, further comprising a scale mechanism
having an indicia surface, wherein: said scale mechanism has a
channel defined therein which is configured to receive said trial
body portion, and said channel is configured so that said trail
head portion is positioned adjacent to said indicia surface when
(i) said trial body portion is located within said channel, and
(ii) said trial head portion is supported by said trial body
portion.
30. The kit of claim 29, wherein: said indicia surface possesses
markings which depict a clock which is divided into a plurality of
sections, and each of said plurality of sections possesses a
distinct value indicated thereon.
31. The kit of claim 28, wherein: said trial body portion includes
a set of internal threads located within said trial bore, said
trial head portion further includes an externally threaded fastener
positioned within a passageway which extends through said trial
head portion, and said externally threaded fastener is configured
to meshingly engage said set of internal threads so as to secure
said trial head portion in fixed relation to said trial body
portion.
32. The kit of claim 28, wherein: said final head stem possesses a
male taper configuration, said final body portion has a final bore
defined therein, said final bore possesses a female taper
configuration, and advancement of said final head stem into said
final bore of said final body portion in a friction fit manner
causes said final head portion to be secured to said final body
portion.
33. The kit of claim 28, wherein: said trial body portion includes
(i) a trial body stem, (ii) a neck attached to said trial body
stem, and (iii) a flat attached to said neck, and said trial bore
extends through said flat and into said neck.
34. The kit of claim 28, wherein: said trial offset indicia
includes a notch defined in said trial head member, and said final
offset indicia includes a removable sticker positioned on a surface
of said final head member.
35. The kit of claim 28, wherein: said trial body portion is
configured to be advanced into a humerus, and said final body
portion is also configured to be advanced into said humerus.
36. A kit, comprising: a trial assembly including (i) a trial body
portion, (ii) a trial head portion which includes a trial offset
indicia, and (iii) a fastener for securing said trial head portion
to said trial body portion; and a final prosthesis assembly
including a final body portion having a final bore defined therein,
and a final head portion having (i) a final head member which
includes a final offset indicia, and (ii) an eccentrically located
final head stem extending from said final head portion, said final
head stem being configured to be received within said final
bore.
37. The kit of claim 36, wherein: said trial body portion has a
trial bore defined therein, and said trial head portion has (i) a
trial head member which includes said trial offset indicia, and
(ii) an eccentrically located trial stem extending from said trial
head member, said trial head stem being configured to be received
within said trial bore.
38. The kit of claim 36, further comprising a scale mechanism
having an indicia surface, wherein: said scale mechanism has a
channel defined therein which is configured to receive said trial
body portion, and said channel is configured so that said trail
head portion is positioned adjacent to said indicia surface when
(i) said trial body portion is located within said channel, and
(ii) said trial head portion is supported by said trial body
portion.
39. The kit of claim 38, wherein: said indicia surface possesses
markings which depict a clock which is divided into a plurality of
sections, and each of said plurality of sections possesses a
distinct value indicated thereon.
40. The kit of claim 37, wherein: said trial body portion includes
a set of internal threads located within said trial bore, said
fastener includes an externally threaded portion, said fastener is
configured to be received within a passageway which extends through
said trial head portion, and said externally threaded portion is
configured to meshingly engage said set of internal threads so as
to secure said trial head portion in fixed relation to said trial
body portion.
41. The kit of claim 36, wherein: said final head stem possesses a
male taper configuration, said final body portion has a final bore
defined therein, said final bore possesses a female taper
configuration, and advancement of said final head stem into said
final bore of said final body portion in a friction fit manner
causes said final head portion to be secured to said final body
portion.
42. The kit of claim 37, wherein: said trial body portion includes
a (i) a trial body stem, (ii) a neck attached to said trial body
stem, and (iii) a flat attached to said neck, and said trial bore
extends through said flat and into said neck.
43. The kit of claim 37, wherein: said trial offset indicia
includes a notch defined in said trial head member, and said final
offset indicia includes a removable sticker positioned on a surface
of said final head member.
44. The kit of claim 36, wherein: said trial body portion is
configured to be advanced into a humerus, and said final body
portion is also configured to be advanced into said humerus.
Description
[0001] This application claims the benefit of U.S. Provisional
Application Serial No. 60/221,657, filed Jul. 28, 2000.
FIELD OF THE INVENTION
[0002] The present invention relates to prostheses for
reconstructive surgery of a gleno-humeral joint and, more
particularly, to the positioning of an eccentric head of a humerus
prostheses for reconstructive surgery of a gleno-humeral joint.
BACKGROUND
[0003] In total shoulder arthroplasty, reproduction of the correct
location of the humeral articular surface is critical to
reestablishing joint biometrics. Translating this location to the
implant is thus of critical importance.
[0004] Each shoulder arthroplasty needs to be adapted to the
patient's unique combination of soft tissue and bone anatomy. As
well, the patient typically has high expectations of the function
and durability of the arthroplasty. Thus, the implant and the
implant technique must be precise.
[0005] In view of this, there has been developed a range of
prostheses designed to fit the various sizes and shapes of people's
anatomy. For shoulder arthroplasty, a prosthesis with a humerus
head has been developed. It has been recognized, though, that the
humerus head may need to be eccentrically mounted relative to the
prosthesis body in order to cover the exposed, resected humerus
head. There has been a problem, however, with the ability to
adequately position the eccentric head on the implant in order to
meet the needs of every patient. Typically, the eccentric head is
positionable in only a few select orientations relative to the
eccentricity.
[0006] Thus, there is a need for an prosthetic implant that can
utilize an eccentric head wherein the eccentric head may be
positioned in any number of rotatably eccentric positions.
SUMMARY OF THE INVENTION
[0007] The present invention is a method, apparatus and
corresponding implant for positioning an eccentric head on a trail
implant/broach and transferring or translating the eccentric
position of the head onto the actual or definitive implant. The
present invention allows the eccentric head to be positioned in an
infinite amount of positions or orientations to best reproduce the
articular geometry of the patient. The infinite dialability is
optimum for reconstruction purposes.
[0008] Because each shoulder arthroplasty needs to be adapted to
the patient's unique combination of soft tissue and bone anatomy,
the present system maximizes the surgeon's flexibility in matching
a wide variety of anatomic requirements. The present invention
places a premium on secure fixation, conservation of bone and
optimization of mechanics.
[0009] During the trialing process, the humeral head trial is
lockable into one of an infinite variety of rotational positions (a
set orientation) that then may be transferred to the definitive
humeral head of the definitive implant. A means is provided for
locking the eccentric trial head to the trial/broach in a set
orientation that allows for the trialing process to occur without
spinning of the eccentric trial head in the broach taper. In one
form, this is accomplished via a captured screw in the eccentric
trial head that extends beyond the taper of a neck of the eccentric
trial head. The captured screw engages threads in a bottom of a
bore in a taper in the broach.
[0010] Once the eccentric head has been threaded onto the trial
broach, it is rotated into a correct position covering the resected
humeral head surface. The eccentric head may be rotated into an
infinite number of positions on the trail broach without having to
be locked in any particular orientation. Once the eccentric head is
in position, the captured screw is tightened or locked. Trial
reduction is carried out and if deemed satisfactory, the
broach/eccentric head trail head assembly (or trial assembly) is
removed as a one piece unit from the humerus of the patient.
[0011] In accordance with an aspect of the present invention, the
eccentric head includes a mark or indicia showing the position of
maximum offset. Once the trial assembly has been removed, from the
patient's humerus, it is placed in an impaction stand or block. The
impaction stand allows the measurement of the orientation of the
eccentric head (by the indicia) on the trial broach, and the
translation or transference of that orientation onto the definitive
implant. The impaction stand has a scale or demarcations on a
surface thereof. The orientation of the indicia of the eccentric
head is noted relative to the scale.
[0012] The trial assembly is then removed from the impaction stand
and the appropriate size of the definitive implant is placed in the
impaction stand. An appropriate size of definitive eccentric head
is placed on the definitive implant. The definitive eccentric head
includes an indicia either as an etched or otherwise arrow or other
marking on the nonarticulating surface (or by a removable sticker
or the like on the articulating surface) showing the position of
maximum offset (in like manner to the trial eccentric head). The
indicia of the definitive eccentric head is orientated or aligned
with the scale to the same number or marking as the trial eccentric
head.
[0013] Once the definitive eccentric head has been properly
aligned, the definitive eccentric humeral head is impacted into
place onto the definitive implant while on the impaction stand. In
this manner, the appropriate position of the humeral head for the
definitive implant has been successfully transferred from the trial
assembly.
[0014] It can be appreciated from the foregoing, that the eccentric
head may be rotationally positioned in an infinite number of
positions, both during trialing and during the final implant.
[0015] In accordance with one embodiment of the present invention,
there is provided a method of implanting a final prosthesis
assembly in a resected bone. The method includes the step of
positioning a trial assembly in the resected bone, the trial
assembly including a trial body portion having a trial bore defined
therein, and a trial head portion having (i) a trial head member
which includes a trial offset indicia, and (ii) an eccentrically
located trial head stem extending from the trial head member, the
trial head stem being configured to be received within the trial
bore. The method further includes the step of rotating the trial
head portion relative to the trial body portion while the trial
assembly is positioned in the resected bone so as to position the
trial head portion relative to the trial body portion at an aligned
orientation whereby the trial head portion covers a resected
surface of the resected bone. In addition, the method includes the
step of removing the trial assembly from the resected bone after
the rotating step. The method also includes the step of positioning
the trial assembly in a scale mechanism whereby the trial offset
indicia of the trial head portion aligns with a value on the scale
mechanism. Moreover, the method includes the step of securing a
final head portion to a final body portion based on the value so as
to form the final prosthesis assembly. Additionally, the method
includes the step of implanting the final prosthesis assembly in
the resected bone after the securing step.
[0016] Pursuant to another embodiment of the present invention,
there is provided a method of implanting a final prosthesis
assembly in a resected bone. The method includes the step of
providing a trail assembly which includes a trial body portion
having a trial bore defined therein, and a trial head portion
having (i) a trial head member which includes a trial offset
indicia, and (ii) an eccentrically located trial head stem
extending from the trial head member. The method further includes
the step of positioning the trial body portion in the resected
bone. Also, the method includes the step of positioning the trial
stem in the trial bore after the trial body positioning step. In
addition, the method includes the step of moving the trial head
portion in relation to the trial body portion after the trial stem
positioning step so as to locate the trial head portion relative to
the trial body portion at a user-selected orientation. The method
also includes the step of securing the trial head portion to the
trial body portion at the user-selected orientation. Additionally,
the method includes the step of removing the trial assembly from
the resected bone after the securing step. Furthermore, the method
includes the step of positioning the trial assembly in a scale
mechanism after the removing step whereby the trial offset indicia
of the trial head portion aligns with a value on the scale
mechanism. Moreover, the method includes the step of attaching a
final head portion in fixed relation to a final body portion based
on the value so as to form the final prosthesis assembly. The
method also includes the step of implanting the final prosthesis
assembly in the resected bone after the attaching step.
[0017] According to still another embodiment of the present
invention, there is provided a kit used during the implantation of
a prosthesis. The kit includes a trial assembly including a trial
body portion having a trial bore defined therein, and a trial head
portion having (i) a trail head member which includes a trial
offset indicia, and (ii) an eccentrically located trial stem
extending from the trial head member, the trial head stem being
configured to be received within the trial bore. The kit also
includes a final prosthesis assembly including a final body portion
having a final bore defined therein, and a final head portion
having (i) a final head member which includes a final offset
indicia, and (ii) an eccentrically located final head stem
extending from the final head portion, the final head stem being
configured to be received within the final bore.
[0018] According to yet another embodiment of the present
invention, there is provided a kit which includes a trial assembly
including (i) a trial body portion, (ii) a trial head portion which
includes a trial offset indicia, and (iii) a fastener for securing
the trial head portion to the trial body portion. The kit further
includes a final prosthesis assembly including a final body portion
having a final bore defined therein, and a final head portion
having (i) a final head member which includes a final offset
indicia, and (ii) an eccentrically located final head stem
extending from the final head portion, the final head stem being
configured to be received within the final bore.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention will be better understood by reference
to the following description of an embodiment of the invention
taken in conjunction with the accompanying drawings, wherein:
[0020] FIGS. 1A and 1B are elevational views of exemplary humerus
prostheses/trail broach bodies used in conjunction with the
eccentric head of the present invention;
[0021] FIG. 2 is an enlarged, side sectional view of a partial
humerus with a portion of the humerus head resected (removed) and a
trail broach inserted into the humerus;
[0022] FIG. 3 is a bottom plan view of an eccentric trail humerus
head;
[0023] FIG. 4 is a side elevational view of the eccentric trial
humerus head of FIG. 3;
[0024] FIG. 5 is a front elevational view of a partial humerus with
the humerus head resected;
[0025] FIG. 6 is a front elevational view of the partial humerus of
FIG. 5 showing a trial standard humerus head that exposes a portion
of the surface of the resected humerus head;
[0026] FIG. 7 is a front elevational view of the partial humerus of
FIG. 5 showing the trial eccentric humerus head covering the
surface of the resected humerus head;
[0027] FIG. 8 is an enlarged side elevational view of the trial
eccentric humerus head of FIGS. 3 and 4 having a seating screw
extending therefrom;
[0028] FIG. 9 is an enlarged perspective view of the seating screw
of FIG. 8;
[0029] FIG. 10 is a perspective view of a trial eccentric head
being attached to the trial broach via a driver;
[0030] FIG. 11 is an enlarged, side sectional view of a partial
humerus with the trail assembly (broach and eccentric head inserted
into the humerus;
[0031] FIG. 12 is a top perspective view of an impaction stand;
[0032] FIG. 13 is a bottom perspective view of the impaction stand
of FIG. 12;
[0033] FIG. 14 is a side elevational view of the impaction stand of
FIGS. 12 and 13;
[0034] FIG. 15 is a top plan view of the impaction stand of FIGS.
12-14;
[0035] FIG. 16 is a bottom plan view of the impaction stand of
FIGS. 12-14;
[0036] FIG. 17 is a perspective view of the impaction stand with a
broach or implant seated thereon;
[0037] FIG. 18 is an enlarged top plan view of a trial assembly
seated on the impaction stand with the indicia (notch) of the trial
eccentric head positioned at "5"; and
[0038] FIG. 19 is a perspective view of the impaction stand with a
definitive implant seated thereon with a definitive eccentric
humerus head ready to be impacted onto the implant.
[0039] Corresponding reference characters indicate corresponding
parts throughout the several views.
DETAILED DESCRIPTION
[0040] With reference to FIG. 1A, there is shown an exemplary, 210
mm humerus prosthesis or trial broach generally designated 20. The
humerus prostheses/trial broach 20 includes a stem 22 extending
from a neck 24. The neck 24 terminates in a generally flat surface
26 that is adapted to be seated on a surface of a resected humerus
head of a patient's humerus. In FIG. 1B, there is shown an
exemplary, 138 mm humerus prosthesis or trial broach generally
designated 28. The humerus prostheses/trial broach 28 includes a
stem 30 extending from a neck 32. The neck 32 terminates in a
generally flat surface 34 that is adapted to be seated on a surface
of a resected humerus head of a patient's humerus.
[0041] In FIG. 2, there is shown a patient's humerus 36 wherein the
humerus head 38 has been resected in accordance with standard
shoulder arthroplasty surgery. It is beyond the scope of the
present invention to discuss humerus head resection. Various texts
and papers may be consulted for this procedure. After the humerus
head 38 has been resected, the humerus head must be sized for a
prosthetic head of the implant. Various sizes are available such as
44, 48 and 52 mm. It will be assumed that an eccentric head will be
chosen. In FIG. 2, the medullary canal of the humerus 36 has been
reamed and the trial broach 20 has been placed thereon. The flat 26
is in contact with a surface 40 of the resected humerus head 38.
The trial broach 20 is ready to be fitted with a trial eccentric
head.
[0042] Preoperative evaluation of the Humerus 36 with templates
(not shown) helps determine the size of the prostheses and level of
humerus head resection. Humeral head resection is accomplished as
is known in the art or with other methods the detail of which is
beyond the scope of the present invention and this disclosure.
[0043] Briefly, in FIGS. 5-7 there is shown a reason for selecting
an eccentric head. FIG. 5 shows the humerus 36 whose humerus head
38 has been resected. It is now necessary to find a trial head that
will cover the humerus surface 40 formed by the resection. In FIG.
6 a trail standard head 60 having a tapered stem 62 is shown in
position over the surface 40. It can be seen that the surface 40 is
visible around the periphery of the trial standard head 60. A
centerline shows how the trial standard head 60 fits over the
surface 40. Even with rotation of the trial standard head 60, the
surface 40 is exposed. Thus, the trial standard head 60 is not
appropriate. In FIG. 7, a trial eccentric head 42 having a tapered
stem 46 is shown in position over the surface 40. It can be seen
that with the correct rotation/orientation/placement of the trial
eccentric head 42, the entire surface 40 is covered. With an
infinite number of rotational positions, an eccentric head is thus
appropriate.
[0044] Referring to FIGS. 3, and 4, a trial eccentric head 42 in
accordance with the principles of the present invention is shown.
Four eccentric head 42 sizes may be provided, 44 mm, 48 mm, 52 mm,
and 56 mm. The trial eccentric head 42 includes a tapered stem 46
that is positioned off center (approximately a 4 mm offset) such
that an eccentricity during rotation thereabout is defined or
formed. The stem 46 extends essentially perpendicularly from a
bottom surface 43 of the trial eccentric head 42 and includes a
bore 48 that extends through the stem 46 and the head 42. The trial
eccentric head 42 includes an indicia (here a notch) 44 that
indicates a maximum offset position for the eccentric head 42. It
should be appreciated that other types of indicia may be used. Here
the notch 44 is located on the edge of the articular surface of the
eccentric head 42.
[0045] Referring to FIG. 9, a retaining screw or the like 50 for
the trial assembly (trial eccentric head and trial broach) is
shown. The retaining screw 50 includes a head 52 having an opening
54 for receiving a screw driver or the like. The opening may be hex
shape or otherwise. Extending from the head 52 is a shank 56
terminating in threads 58. The retaining screw 50 is designed to
fit into the bore 48 of the trial eccentric head 42 with its
threads 58 extending therefrom (see FIG. 8).
[0046] Referring to FIG. 10, the trial broach 20 is shown wherein
the trial eccentric head 42 is ready to be attached thereto. Using
an appropriate screw driver 66, the eccentric trial head 42 is
attached to the trial broach by threading the screw 50 into a
complementary threaded bore 64 in the flat 26. Once the eccentric
head 42 is attached to the trial broach 20 it is inserted into the
humerus 36 (see FIG. 11). Once the trial prosthesis is in place as
depicted in FIG. 11, the screw 50 may be loosened to rotate the
eccentric head 42 to a proper orientation. Once a proper rotational
orientation has been achieved, the screw 50 is tightened. The trial
prosthesis may now be removed from the humerus 36. Once the trial
prosthesis has been removed from the humerus 36 it is ready to be
place in an impaction stand or block in accordance with the
principles of the present invention. The position of the eccentric
head 42 is now ready to be transferred or reproduced in the final
or definitive prosthetic implant that will remain in the
patient.
[0047] Referring to FIGS. 12-16, there is shown an impaction stand
or block generally designated 70 in accordance with the principles
of the present invention. The impaction stand 70 may be made of a
suitable plastic or the like and is essentially a hexagonal
cylinder. The impaction stand 70 is designed to accommodate various
sizes of trail broaches/final prostheses. To this end, the
impaction stand 70 has two faces or surfaces 76 and 78 on opposite
sides thereof. Extending diagonally from the surface 76 to an
outside surface of the cylinder is a first channel 72. Extending
diagonally from the surface 78, opposite in orientation to the
first channel 72, is a second channel 74. The second channel 74
extends to an outside surface of the cylinder. The first and second
channels 72 and 74 and their respective surfaces 76 and 78, are
designed to accommodate various sizes of trial broaches/final
prostheses. In the figures, surface 76/channel 72 is designed to
hold trial broaches/final prostheses of sizes 6 mm, 8, and 10 mm,
while the surface 78/channel 74 is designed to hold trial
broaches/final prostheses of sizes 12 mm, 14 mm, and 16 mm. Of
course, it should be appreciated that the impaction block 70 may be
designed for other sizes, or several blocks for the various
sizes.
[0048] Each surface 76 and 78 includes an indicia or scale in the
manner of a clock or the like that divides the periphery thereof
into sections. The scale is used to reference the position of the
notch 44 of the trial eccentric head 42 when the trial assembly is
place in the impaction stand (as well as the final assembly as
indicated below).
[0049] Referring to FIGS. 17 and 18 the trial assembly is placed
into the impaction stand 70 (in FIG. 17, the eccentric head is not
present to illustrate how the body 22 fits in the impaction stand
70/channel 74). As seen in FIG. 18 the position of the notch 44 in
the trial eccentric head 42 is noted (here at position 5) for
transference or reproduction onto the final prosthesis.
[0050] The final step is to fit the final eccentric head onto the
final humeral stem (of the same size as the trial broach). The
trial assembly is removed from the impaction stand 70 and the final
humeral stem/body is placed therein (see FIG. 17). In FIG. 19, a
final eccentric head 80 is chosen of the same size as the trial
eccentric head 42. The final eccentric head 80 is held by an
impactor 86 such as a Delrin-tipped impactor. The final eccentric
head includes an indicia, either as a permanent mark or the like on
the nonarticulating surface thereof or as a removable sticker or
the like on the articulating surface thereof, that indicates the
maximum offset in like manner to the trial eccentric head 42. The
indicia of the final eccentric head 80 is aligned with the marking
or indicia on the scale of the surface 78 that is the same as that
noted above (here "5"). The taper 82 of the eccentric head 80 is
inserted into a complementary tapered bore 84. Keeping the indicia
of the eccentric head 80 as noted, the final eccentric head 80 is
impacted onto the final humeral stem with a mallet (not shown) onto
the impactor 86. The final assembly is now ready to be inserted
back into the patient's humerus.
[0051] While this invention has been described as having a
preferred design and/or configuration, the present invention can be
further modified within the spirit and scope of this disclosure.
This application is therefore intended to cover any variations,
uses, or adaptations of the invention using its general principles.
Further, this application is intended to cover such departures from
the present disclosure as come within known or customary practice
in the art to which this invention pertains. For example, while the
invention is discussed in the context of implanting a prosthesis in
the humerus, the present is application to implantation of a
prosthesis into any bone which forms a joint such as the shoulder,
hip, etc. For instance, the present in invention is application to
the implantation of a prosthesis into a femur.
* * * * *