U.S. patent application number 11/656285 was filed with the patent office on 2007-05-24 for adjustable bone prostheses and related methods related applications.
This patent application is currently assigned to IncuMed, Inc.. Invention is credited to George Hadley Callaway, Dennis M. McDevitt.
Application Number | 20070118230 11/656285 |
Document ID | / |
Family ID | 26718455 |
Filed Date | 2007-05-24 |
United States Patent
Application |
20070118230 |
Kind Code |
A1 |
Callaway; George Hadley ; et
al. |
May 24, 2007 |
Adjustable bone prostheses and related methods related
applications
Abstract
Adjustable prostheses and related methods provide a wide range
of adjustment along or about multiple axes. The prostheses and
related methods make possible a straightforward, yet robust way of
securing, e.g., a humeral head prosthesis in a desired position and
maintaining the prosthesis in the desired position during use.
Inventors: |
Callaway; George Hadley;
(Raleigh, NC) ; McDevitt; Dennis M.; (Raleigh,
NC) |
Correspondence
Address: |
Daniel D. Ryan;RYAN KROMHOLZ & MANION, S.C.
Post Office Box 26618
Milwaukee
WI
53226-0618
US
|
Assignee: |
IncuMed, Inc.
|
Family ID: |
26718455 |
Appl. No.: |
11/656285 |
Filed: |
January 22, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10767673 |
Jan 29, 2004 |
7166132 |
|
|
11656285 |
Jan 22, 2007 |
|
|
|
10041722 |
Jan 8, 2002 |
6736852 |
|
|
10767673 |
Jan 29, 2004 |
|
|
|
60271895 |
Feb 27, 2001 |
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Current U.S.
Class: |
623/23.47 ;
623/19.12; 623/38 |
Current CPC
Class: |
A61F 2002/30507
20130101; A61F 2002/30378 20130101; A61F 2002/4681 20130101; A61F
2250/0006 20130101; F16M 11/14 20130101; A61F 2220/0025 20130101;
A61F 2002/4044 20130101; A61F 2310/00017 20130101; Y10T 403/32606
20150115; A61F 2002/4638 20130101; A61F 2/40 20130101; A61F 2/4014
20130101; A61F 2002/30553 20130101; A61F 2002/4062 20130101; Y10T
403/32639 20150115; A61F 2250/0097 20130101; Y10T 403/32622
20150115; A61F 2002/30433 20130101; A61F 2002/30514 20130101; A61F
2250/0063 20130101; A61F 2002/30332 20130101; A61F 2002/4037
20130101; A61F 2002/30899 20130101; A61F 2220/0041 20130101; A61F
2250/0008 20130101; F16C 11/0661 20130101; F16C 11/106 20130101;
A61F 2002/30405 20130101; A61F 2220/0033 20130101; A61F 2/4684
20130101; A61F 2002/30538 20130101; A61F 2002/30797 20130101; A61F
2002/30617 20130101; A61F 2002/30604 20130101; A61F 2002/30884
20130101 |
Class at
Publication: |
623/023.47 ;
623/038; 623/019.12 |
International
Class: |
A61F 2/28 20060101
A61F002/28 |
Claims
1. An assembly comprising a prosthesis; a support; a mount carried
by the support for movement relative to an axis, the mount
including a mounting surface adapted to be coupled to the
prosthesis; and a locking mechanism coupled to the mount and
comprising a series of stacked washers to selectively free the
mount for movement and to selectively restrain the mount against
movement.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of co-pending U.S.
application Ser. No. 10/767,673, filed Jan. 29, 2004, which is a
divisional of U.S. application Ser. No. 10/041,722, filed Jan. 8,
2002 (now U.S. Pat. No. 6,736,852), which claims the benefit of
provisional Application Ser. No. 60/271,895, filed Feb. 27, 2001,
entitled "Adjustable Head Prosthesis for the Shoulder."
FIELD OF THE INVENTION
[0002] This invention generally relates to an adjustable mounting
assembly and alignment system for a bone prosthesis and related
methods.
BACKGROUND OF THE INVENTION
[0003] A shoulder joint consists of a ball-and-socket type coupling
of the humerus to the scapula. The humerus forms the ball, and the
socket is formed at the glenoid cavity of the scapula. Injury or
disease to the joint often results in destruction or deterioration
of the head of the humerus, leading to pain and a corresponding
loss of mobility and function. In such cases, it is often necessary
to provide a replacement joint surface, i.e., a prosthesis, for the
head of the humerus that mates with the glenoid cavity.
[0004] The proper alignment of the prosthesis is generally useful
to effective performance of the replacement procedure. Typically,
the position of the mount is adjusted until the desired position is
achieved. The mount is fixed in the desired position and the
prosthesis is then secured onto the mount.
[0005] However, conventional mounts provide only a limited range of
adjustment, typically allowing only two degrees of freedom, i.e.,
linearly along an X-axis and Y-axis. The devices that do have more
degrees of freedom require multiple trials and a fixture to be used
away from the surgical site for proper alignment of the prosthesis
to the humerus.
[0006] Further, even upon locking the device in a desired position,
conventional mounts may not hold the desired position. This is
especially true when force is exerted, e.g., hammering the
prosthesis to secure its placement on a mount.
[0007] There remains a need for mounting systems and methods that
permit a wide range of adjustment of a humeral head prosthesis
while enabling the mount, and attached prosthesis, to remain
securely fixed in a desired position.
SUMMARY OF THE INVENTION
[0008] The invention provides various adjustable prostheses and
related methods that provide a wide range of adjustment along or
about multiple axes. The invention makes possible a
straightforward, yet robust way of securing, e.g., a humeral head
prosthesis in a desired position and maintaining the prosthesis in
the desired position during use.
[0009] Other features and advantages of the inventions are set
forth in the following specification and attached drawings.
DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is an exploded view of the components of an
adjustable locking mount system that embodies features of the
invention, in which the mounting hub is centric.
[0011] FIG. 2 is an assembled perspective view of the system shown
in FIG. 1.
[0012] FIG. 3a is a side sectional view of the assembled components
of the system shown in FIG. 2.
[0013] FIG. 3b is a view similar to FIG. 3a and illustrating the
spherical radii of the stacked washers.
[0014] FIGS. 4a-4e illustrate rotational movement of the
cooperating components of the assembled system shown in FIG. 2.
[0015] FIG. 5a is a side sectional view of the assembled components
of the system shown in FIG. 3 and illustrating the system
components in a level position.
[0016] FIG. 5b is a sectional view as shown in FIG. 5a,
illustrating the position of the system components and the movement
of the mounting hub and lock washer when the mounting hub is
rotated about the x or y axis.
[0017] FIG. 5c is a sectional view as shown in FIG. 5b,
illustrating the procedure of locking the system in a desired
position.
[0018] FIG. 6 is an exploded view of the components of an
alternative embodiment of an adjustable locking mount system that
embodies features of the invention, in which the mounting hub is
eccentric.
[0019] FIG. 7 is an assembled perspective view of the system shown
in FIG. 6.
[0020] FIG. 8 is side sectional view of the assembled components of
the system shown in FIG. 7.
[0021] FIGS. 9a-9e illustrate rotational movement of the
cooperating components of the assembled system shown in FIG. 7.
[0022] FIG. 10 is an exploded view of an adjustable locking mount
system embodying features of the invention incorporated in a
shoulder replacement assembly.
[0023] FIG. 11 is a perspective view of the assembled components of
the system shown in FIG. 10.
[0024] FIG. 12a is an enlarged perspective view of the top portion
of the trial ring shown in FIG. 10.
[0025] FIG. 12b is an enlarged perspective view of the bottom
portion of the trial ring shown in FIG. 10.
[0026] FIG. 13a is an enlarged perspective view of the top portion
of the artificial head shown in FIG. 10.
[0027] FIG. 13b is an enlarged perspective view of the bottom
portion of the artificial head shown in FIG. 10, and further
illustrating the interior surface of the artificial head.
[0028] FIG. 14a is an exploded view of the components of an
alternate embodiment of a shoulder replacement system embodying
features of the invention and viewed from the head to the stem.
[0029] FIG. 14b is a view similar to FIG. 14a and viewed from the
stem to the head.
[0030] FIG. 15 is a view similar to FIGS. 14a and 14b and
illustrating a partially assembled view of the system
components.
[0031] FIG. 16 is a perspective view of a humerus bone, with a line
representing a cut in the ball portion of the humerus made during
shoulder replacement surgery.
[0032] FIG. 17 illustrates a humerus as shown in FIG. 16,
illustrating the head cut and removed from the humerus and a bore
reamed into the bone.
[0033] FIG. 18 is a perspective view illustrating a humerus as
shown in FIG. 17, and further illustrating the insertion into the
bore of a stem carrying an adjustable mount of the present
invention.
[0034] FIGS. 19a and 19b are perspective views illustrating a
humerus as shown in FIG. 18, and further illustrating a trial ring
engaging the mount and being rotated simultaneously with the
mount.
[0035] FIG. 19c illustrates the trial being and the mount rotated
independently of each other.
[0036] FIG. 20 illustrates a humerus as shown in FIGS. 19a and 19b,
illustrating the trial ring being simultaneously tilted with the
mount.
[0037] FIG. 21 illustrates a humerus as shown in FIG. 20, and
further illustrates the procedure of locking the mount in a desired
position.
[0038] FIG. 22 shows a humerus as in FIG. 21, with the trial ring
removed and illustrating the placement of an artificial head onto
the mount.
[0039] FIG. 23 illustrates a humerus as shown in FIG. 22, with the
artificial head placed on the mount and further illustrating the
use of a hammer to secure the artificial head on the mount.
[0040] FIG. 24a is an exploded view of the components of an
alternative embodiment of a shoulder replacement system embodying
features of the invention and viewed from the head to the stem.
[0041] FIG. 24b is a view similar to FIG. 24a and viewed from the
stem to the head.
[0042] FIG. 25 is a view similar to FIGS. 24a and 24b and
illustrating the use and placement of the pivot pin component of
the system to secure the bottom insert component onto the stem
component.
[0043] FIG. 26 is a view similar to FIG. 25 and illustrating the
placement of the eccentric mount component onto the bottom insert
component.
[0044] FIGS. 27a-27e are partially assembled views of the system
shown in FIGS. 24a and 24b and illustrating rotational movement of
the partially assembled system.
[0045] FIG. 28 is a partially assembled view of the system shown in
FIGS. 24a and 24b and illustrating the placement of the top insert
on the bottom insert.
[0046] FIG. 29 is a perspective view of the components of the
system shown in 24a and 24b assembled.
[0047] FIG. 30a is an exploded view of the components of an
alternative embodiment of a shoulder replacement system embodying
features of the invention and viewed from the head to the stem.
[0048] FIG. 30b is view similar to FIG. 30a and viewed from the
stem to the head.
[0049] FIG. 31 is a view similar to FIGS. 30a and 30b illustrating
the use of the pivot pin component to secure the mounting ring and
the bottom disk to the stem.
[0050] FIG. 32 is a view similar to FIG. 31 and illustrating the
placement of the top disc on the bottom disk.
[0051] FIGS. 33a-33e are views similar to FIG. 32 and illustrating
the placement of the head component onto the mounting ring
component and further illustrating the rotational movement of the
assembled system.
[0052] FIG. 34 is a view similar to FIGS. 33a-33e and illustrating
the locking of the assembled system in a desired position.
[0053] FIG. 35a is an exploded view of an alternative embodiment of
a shoulder replacement system embodying features of the invention
viewed from the head to the stem.
[0054] FIG. 35b is a view similar to FIG. 35a and viewed from the
stem to the head.
[0055] FIG. 36 is an exploded view of the bottom and top plate
components of the system shown in FIGS. 35a and 35b and
illustrating the major and minor axes of the top and bottom
plates.
[0056] FIG. 37 is a partially assembled view of the system shown in
FIGS. 35a and 35b and illustrating the use of the pivot pin to
secure the placement of the bottom plate onto to stem.
[0057] FIG. 38 is a view similar to FIG. 37 and illustrating the
placement of the top plate on the bottom plate.
[0058] FIGS. 39a-39e are views similar to FIG. 38 and illustrating
rotational movement of the partially assembled system.
[0059] FIG. 40 is an assembled view of the system shown in FIGS.
35a and 35b.
[0060] The invention may be embodied in several forms without
departing from its spirit or essential characteristics. The scope
of the invention is defined in the appended claims, rather than in
the specific description preceding them. All embodiments that fall
within the meaning and range of equivalency of the claims are
therefore intended to be embraced by the claims.
DETAILED DESCRIPTION
[0061] Although the disclosure hereof is detailed and exact to
enable those skilled in the art to practice the invention, the
physical embodiments herein disclosed merely exemplify the
invention that may be embodied in other specific structure. While
the preferred embodiment has been described, the details may be
changed without departing from the invention, which is defined by
the claims.
I. The Adjustable Locking Mount System
[0062] A. System 1: [0063] Interior Hub Centrally Located with
Respect to Mounting Surface
[0064] FIG. 1 shows the individual components of an adjustable
locking mounting system 10A. FIGS. 2 and 3a illustrate the system
10A when assembled. As will be described in detail later, the
system 10A permits adjustment in three directions or three degrees
of freedom (rotational around axes x, y, and z, where the z-axis is
represented by the axis of the pivot pin 12) (see FIGS. 4a-4e).
[0065] The system 10A comprises the pivot pin 12, at least one slip
washer 14, at least one lock washer 16, a mounting hub 18, and a
locking screw 20. Each of these components of the system 10A will
now be described in detail.
[0066] 1. System Components
[0067] As seen in FIG. 1, the pivot pin 12 is a rigid, generally
cylindrical or rod-like member. The pivot pin 12 is convex, e.g.,
domed, at one end to couple with the mounting hub 18 (see, e.g.,
FIG. 3a). In a representative embodiment, the arc of curvature is
0.400'' diameter (0.200'' radius).
[0068] In particular, the convex arrangement permits adjustment of
the mounting hub 18 by swinging or tilting across the axis of the
pivot pin 12 (i.e., rotation about the x-axis and y-axis) as well
as by rotating or twisting about the axis of the pivot pin 12
(i.e., rotation about the z-axis) (see FIGS. 4a-4e).
[0069] As best seen in FIGS. 1 and 3, the pivot pin 12 has a
threaded central bore 26 that serves to receive the locking screw
20. Thus, the pivot pin 12 serves to receive both the mounting hub
18 and the locking screw 20 (see FIG. 3a).
[0070] The pivot pin 12 can be made of suitable metal, plastic, or
ceramic materials and formed by conventional molding or machining
techniques.
[0071] As shown in FIG. 1, the mounting hub 18 is a rigid member
comprising a mounting surface 24, an interior hub 22, and an
exterior pivot surface 28. The center of the mounting hub 18 serves
to receive the locking screw 20.
[0072] The mounting surface 24 is configured to mate with an object
or device being mounted on the hub and therefore can take on a
variety of shapes. Thus, the mounting hub 18 serves as a base for
mounting of another object or device. For example, the mounting
surface 24 can be circular or geometric. In the illustrated
embodiment, the mounting surface 24 is generally circular.
[0073] Additionally, the mounting surface 24 can be stepped to
further aid in positioning and securing the object or device on the
mounting surface 24 (not shown). In this arrangement, the object or
device being mounted would have a complementary stepped surface.
The stepped surface provides greater control of any adjustment by
permitting adjustment to be in uniform increments and reducing the
risk of inadvertent movement. The mounting surface 24 could
alternatively be a threaded surface to facilitate engagement with a
mating part.
[0074] As best illustrated in FIG. 1, the interior hub 22 is open.
The bottom surface of the interior hub 22 is configured to conform
to the shape of the convex end of the pivot pin 12 and sized to
receive the slip washer(s) 14 and lock washer(s) 16. That is, the
interior hub 22 permits a slip washer 14 and lock washer 16, or
multiple slip washers 14 and lock washers 16, to be alternately
stacked upon one another (see FIG. 3a).
[0075] As shown in FIGS. 1-3a, the exterior pivot surface 28 of the
mounting hub 18 is configured to nest on and to conform to the
convex end of the pivot pin 12, thus permitting a wider range of
motion, as previously described.
[0076] As best seen in FIG. 3a, the exterior pivot surface 28 is
located centrally with respect to the interior hub 22. Further, the
interior hub 22 is centrally located with respect to the mounting
surface 24, such that the geometric center of the mounting hub 18
coincides with the center of rotation of the mounting hub 18 about
the pivot pin 12.
[0077] The mounting hub 18 serves to engage and pivot about the
pivot pin 12, thus permitting adjustment of the position of the
mounting hub 18 with respect to the pivot pin 12, as will be
described later. Upon obtaining the desired position, the position
of the mounting hub 18 can be locked by use of the locking screw
20, as will also be described in greater detail later.
[0078] The mounting hub 18 can be made of any suitable metal or
plastic and formed by conventional machining or molding
techniques.
[0079] As shown in FIG. 1, the system 10A also provides at least
one slip washer 14. The slip washer 14 is preferably a rigid
annular ring or doughnut-like member. As FIGS. 1 and 3a best show,
the slip washer 14 is configured to conform to the bottom surface
of the interior hub 22.
[0080] The center of the slip washer 14 serves to receive the
locking screw 20. The center of the slip washer 14 is of a diameter
only slightly larger than the outside diameter of the locking screw
20. The slip washer 14 also serves to provide a frictional surface,
which upon tightening of the locking screw 20, serves to further
secure the mounting hub 18 in a desired position.
[0081] The slip washer 14 permits the lock washer 16 to slide
across the surface of the slip washer 14 (see FIGS. 5a and 5b). The
slip washer 14 is similar in function yet physically different in
top and bottom spherical radii from the lock washer 16.
[0082] As seen in FIG. 3b, additional washers 14 and 16 in the
assembly would also have different spherical radii, represented by
R1-R5 in FIG. 3b, as they are stacked further from the center of
rotation or pivot point on the pivot pin 12. In a representative
embodiment, R1 is 0.200, R2 is 0.250, R3 is 0.300, R4 is 0.350, and
R5 is 0.400.
[0083] The radii of the washers 14 and 16 can be varied to
accommodate the thickness of the individual washers 14 and 16.
Regardless of the thickness or radii of the washers 14 and 16, the
washers 14 and 16 are configured to rotate about the same pivot
point.
[0084] Desirably, as illustrated in FIGS. 1 and 3a, a second slip
washer 14, similar in function but differing in spherical radii
from the first slip washer 14 is placed over the lock washer 16. As
illustrated in FIGS. 5a and 5b, the lock washer 16 is able to slide
between the slip washers 14.
[0085] In this arrangement, the second slip washer 14 provides an
additional frictional surface, which upon tightening of the locking
screw 20, serves to further secure the desired position.
[0086] The slip washer(s) 14 can be made of any suitable metal or
plastic and formed by conventional machining or molding
techniques.
[0087] As also seen in FIG. 1, the system 10A further provides a
lock washer 16. The lock washer 16 is a rigid, annular ring or
doughnut-like member similar to the slip washer 14.
[0088] As FIGS. 1 and 3a best illustrate, the lock washer 16 is
configured to conform to the surface of the slip washer 14. This
arrangement permits the lock washer 16 to be stacked on top of the
slip washer 14.
[0089] As in the case of the slip washer 14, the center of the lock
washer 16 serves to receive the locking screw 20. The center of the
lock washer 16 is also sized larger than the center of the slip
washer 14. That is, the center of the lock washer 16 not only
serves to receive the locking screw 20, but also permits the lock
washer 16 to pivot about the pivot pin 12.
[0090] The lock washer 16 also provides two additional frictional
surfaces when sandwiched between two slip washers 14, which upon
tightening of the locking screw 20, serve to further secure the
desired position.
[0091] As also seen in FIGS. 1 and 3a, the lock washer 16 is of a
larger diameter than the slip washer 14. This arrangement allows
the lock washer 16 to fit over the slip washer 14. In a
representative embodiment, the lock washer 16 is sized to
approximate or be slightly less than the diameter of the interior
hub 22, thereby providing a secure fit of the lock washer 16 within
the interior hub 22 and allowing only minimal translation in the x
and y axes, yet not restricting z-axis translation of the lock
washer 16 within the interior hub 22 and with respect to the axis
of the pivot pin 12, as will later be described in detail.
[0092] This arrangement secures/couples the lock washer 16 to the
interior hub 22 and permits the lock washer 16 to slide with the
mounting hub 18 over the slip washer 14 (see, e.g., FIGS. 5a and
5b). Thus, the lock washer 16 serves to provide an additional
rotational and rocking surface for the mounting hub 18.
[0093] Like the slip washer 14, the lock washer 16 can be made of
any suitable plastic or metal and formed by conventional molding or
machining techniques.
[0094] Desirably, as previously noted, a second slip washer 14
similar in function but differing in spherical radii from the first
slip washer 14 can be provided. In this arrangement, as seen in
FIGS. 1 and 3a, the lock washer 16 also serves to receive the
second slip washer 14. It will be apparent that any number of slip
washers 14 and lock washers 16 can be similarly alternately stacked
upon each other and thereby accommodate variations in the depth of
the interior hub 22.
[0095] As also shown in FIG. 1, the system 10A provides a locking
screw 20. The locking screw 20 is a screw that is adapted for
passage through the mounting hub 18, the slip washer(s) 14, the
lock washer(s) 16, and the pivot pin 12 when the system is
assembled (see FIG. 3a). In inside the diameter of the slip washer
14 is sized to approximate or be slightly larger than the diameter
of the locking screw 20. This arrangement secures/couples the slip
washer 14 to the locking screw 20 and the pivot pin 12.
[0096] As illustrated in FIG. 3a, the locking screw 20 is desirably
threaded to fit the threaded bore 26 of the pivot pin 12. As FIG.
5c illustrates, rotation (represented by arrow in FIG. 5c) of the
screw 20, e.g., by an Allen wrench 30, advances the screw into the
pivot pin 12 to fix the mounting hub 18 in a desired position.
[0097] The locking screw 20 can be made of any suitable plastic or
metal and formed by conventional molding or machining
techniques.
[0098] The locking screw 20, when not fully tightened, serves to
hold the assembly while the desired position is determined.
Tightening of the locking screw 20 compresses the washers 14 and
16, hub 18, and pin 12 together, thereby creating multiple
frictional forces between the mating surfaces. These frictional
forces and the compression of the screw 20 are what limit movement
in the locked position.
[0099] It will be apparent that the components just described can
be used in any combination. For example, plastic slip washers 14
may be alternated with metal lock washers 16.
[0100] 2. Adjustment of the Orientation of the Mounting Hub
[0101] The system 10A as previously described enables the mounting
hub 18 to be oriented in a variety of directions with respect to
the pivot pin 12. The types of movement, and thus the types of
adjustments permitted, will now be discussed.
[0102] The system 10A permits movement of the mounting hub 18 in at
least three rotational directions.
[0103] First, as represented by arrows in FIGS. 4a-4b, the mounting
hub 18 can be rocked or rotated, i.e., tilted, about the x-axis
(i.e., side to side rotation). This motion is permitted by the
convex surfaces of the pivot pin 12, mounting hub 18, slip
washer(s) 14, and lock washer(s) 16.
[0104] Second, as represented arrows in FIGS. 4c-4d, the mounting
hub 18 can be rocked or rotated, i.e., tilted, about the y-axis
(i.e., front to back rotation). This motion is permitted by the
convex surfaces of the pivot pin 12, mounting hub 18, slip
washer(s) 14, and lock washer(s) 16.
[0105] Third, as represented by arrows in FIG. 4e, the mounting hub
18 can be rotated 360.degree. in either a clockwise or
counterclockwise direction about the z-axis (i.e., axis of the
pivot pin 12).
[0106] It is to be understood that the rotational and rocking
movements permit adjustment in virtually an infinite number of
rotational directions.
[0107] B. System 2: [0108] Interior Hub Eccentrally Located with
Respect to Mounting Surface [0109] 1. System Components
[0110] FIG. 6 shows the individual components of an alternative
system 10B providing an adjustable locking mount system. FIGS. 7
and 8 illustrate the system 10B when assembled.
[0111] Like system 10A, the system 10B comprises a pivot pin 12, at
least one slip washer 14, at least one lock washer 16, a mounting
hub 18, and a locking screw 20.
[0112] Also like system 10A, the mounting hub 18 has an exterior
pivot surface 28 that is located centrally with respect to the
interior hub 22. In this embodiment, as FIGS. 6-8 best show, the
interior hub 22 is eccentric with respect to the mounting surface
24, such that the geometric center of the mounting hub 18 does not
coincide with the center of rotation of the mounting hub 18 about
the pivot pin 12. The eccentric configuration permits a broader
range of adjustment. [0113] 2. Adjustment of the Orientation of the
Mounting Hub
[0114] The system 10B as previously described enables the mounting
hub 18 to be oriented in a variety of directions with respect to
the pivot pin 12. The types of movement, and thus the types of
adjustments permitted, will now be discussed.
[0115] The system 10B permits movement of the mounting hub 18 in at
least five directions.
[0116] First, as represented by arrows in FIGS. 9a-9b, the mounting
hub 18 can be rocked or rotated about the x-axis, as previously
described for system 10A.
[0117] Second, as represented by arrows in FIGS. 9c-9d, the
mounting hub 18 can be rocked or rotated about the y-axis, as also
previously described for system 10A.
[0118] Third, as represented by arrows in FIG. 9e, the mounting hub
18 can be rotated up to 360.degree. in either direction about the
z-axis, as previously described for system 10A.
[0119] As best illustrated in FIGS. 7 and 8, when the mounting hub
18 includes an interior hub 22 that is eccentric relative to the
mounting surface 24, the distance from the pivot pin 12 to the
mounting surface 24 increases to a maximum value, depicted as point
A1 and then decreases to a minimum value, depicted as point A2.
[0120] Reorientation or translation of the linear position of point
A1 and point A2 with respect to the pivot pin 12 is possible when
the mounting hub 18 is rotated about the z-axis.
[0121] Reorientation of points A1 and A2 with respect to the x-axis
provides a fourth degree of freedom. Similarly, reorientation of
points A1 and A2 with respect to the y-axis provides a fifth degree
of freedom.
[0122] It is to be understood that the rotational and rocking
movements just described permit adjustment in virtually an infinite
number of directions.
[0123] After the desired position is obtained, the locking screw 20
is tightened to secure the mounting hub 18 in the desired position,
as previously described for System 10A (see FIG. 5c).
II. Use of the System in Shoulder Replacement
[0124] FIGS. 10-23 detail the use of either of the
previously-described systems 10A or 10B in shoulder replacement
surgery. Desirably, system 10B would be employed, thereby providing
the greatest range of adjustment. In the embodiment illustrated in
FIGS. 10-23, the mount of system 10B is employed.
[0125] The long bone of the upper or proximal arm, as shown in FIG.
16, is known as the humerus 38. The proximal end of the humerus 38
comprises a ball-shaped head 40 that normally nests within the
glenoid cavity of the shoulder bone, or scapula.
[0126] Through disease or injury, the head 40 of the humerus 38 can
become damaged such that the shape of the head 40 is altered or the
head 40 does not fit properly within the glenoid cavity. Such
damage typically results in the shoulder joint becoming painful and
a corresponding reduction in mobility of the joint.
[0127] Conventional techniques provide for replacement of the head
40 of the humerus 38 with a prosthesis, or artifical head 42. As
seen in FIG. 10, the system 10B, comprising a pivot pin 12, a
mounting hub 18 (with eccentrally located interior hub 22), slip
washers 14, a lock washer 16, and a locking screw 20, can be
employed within a shoulder replacement assembly 44 suitable for
implantation into a humerus 38. The system 10B would permit a
physician to mount, position, and secure an artificial head 42.
[0128] As shown in FIG. 10, the replacement assembly comprises a
stem 46 including tendon attachment holes 50, an assembled system
10B implanted within the stem 46, a trial ring 48, and an
artificial head 42. FIG. 11 illustrates the replacement assembly 44
in assembled form.
[0129] The stem 46 is a conventional stem 46 suitable for
implantation within a humerus 38. The stem 46 desirably includes
tendon attachment holes 50 that serve to secure attachment of
tendons (not shown) to the stem 46.
[0130] The stem 46 serves to hold the system 10B. That is, the
pivot pin 12 is implanted within the stem 46 such that the convex
portion protrudes at a pre-selected angle from the stem 46 (e.g.,
35.degree.).
[0131] The pivot pin 12 can be implanted within the stem 46 by
various techniques. In one embodiment, the pin 12 is integrally
molded with the stem 46. Alternatively, the pin 12 can be a
separate member configured to mate with an existing stem 46. In a
representative embodiment, the pin 12 includes a Morse taper, as
seen in FIG. 10, configured to mate with a complementary tapered
surface within the stem 46. In yet another embodiment, the pin 12
is configured to mate with the stem 46 by threaded engagement (not
shown).
[0132] As also shown in FIG. 10, a trial ring 48 is desirably
provided. The trial ring 48 is a rigid, generally ring-like member
having an inner surface 52 and an outer surface 54. The inner
surface 52 is desirably eccentric relative to the outer surface 54.
The trial ring 48 can be made of plastic or any other suitable
material.
[0133] The trial ring 48 is adapted to mate with the mounting hub
18, i.e., the trial ring's 48 inner surface 52 geometry
approximates the geometry of the mounting surface 24. In the
embodiment illustrated in FIG. 10, the mounting surface 24 is
circular and conically tapered and the trial ring 48 has an inner
surface 52 that is complementary circular and tapered.
[0134] Optionally, the inner surface 52 of the trial ring can be of
a geometric or stepped formation adapted to mate with a
complementary surface on the mounting surface 24, as previously
described (not shown).
[0135] As shown in FIG. 12a, the outer surface 54 of the trial ring
48 desirably has reference markers 56, e.g., A, B, C, and D, spaced
circumferentially around the outer surface 54.
[0136] Optionally, as also seen in FIG. 12a, the outer surface 54
is tapered or radiused outward toward the bottom of the trial ring
48 for better visualization of the markers 56.
[0137] In the embodiment illustrated in FIGS. 12a and 12b, the
outer surface 54 of the trial ring 48 contains knurls 58. The
knurls 58 provide for easier grasping of the trial ring 48.
Optionally, the outer surface 54 does not contain knurls 58 or the
outer surface 54 is otherwise adapted for grasping (not shown). The
outside diameter 57 of the trial ring 48 corresponds or is
equivalent to the outside diameter of the humeral head 42.
[0138] The trial ring 48 is adapted to engage the mounting hub 18
and pivot simultaneously with the mounting hub 18. In this
arrangement, the reference markers 56 can be utilized for
evaluation and recording of the desired position, as will be
described in greater detail later.
[0139] As seen in FIG. 10, an artificial head 42 is also provided.
The artificial head 42 is a rigid, dome-like member having interior
60 and exterior surfaces 62. The artificial head 42 can be made of
stainless steel or other suitable materials.
[0140] As best illustrated in FIGS. 11 and 13a, the exterior
surface 62 is domed to mimic the ball-like head 40 of the humerus
38.
[0141] As seen in FIG. 13b, the interior surface 60 is recessed and
adapted to mate with the mounting surface 24. In the embodiment
illustrated in FIG. 13b, the inner surface 60 is circular.
Optionally, the interior surface 60 can be stepped to mate with a
complementary mounting surface 24, as previously described (not
shown).
[0142] As FIG. 13b also shows, the interior surface 60 desirably
has reference markers 56' that are complementary to, i.e., mirror,
the reference markers 56 on the trial ring 48. This assures that,
when complementary markers 56 and 56' on the trial ring 48 and the
artificial head 42 are similarly orientated with respect to the
mounting hub 18, the position of the artificial head 42 will be the
same as the position of the trial ring 48, as will be explained in
greater detail later.
[0143] Desirably, as in the embodiment illustrated in FIG. 13b, the
recessed inner surface 60 of the artificial head 42 is eccentrally
located with respect to the outer surface 62.
[0144] When used in combination with the eccentrally located
interior hub 22 of system 10B, this arrangement provides a
"double-eccentric" system. The double-eccentric configuration
provides a maximum range of adjustment from O axes offset to up to
the maximum axes offset.
[0145] In an alternate embodiment, shown in FIGS. 14a-14b and 15,
the inner surface 60 of the artificial head 42 is centrally located
with respect to the outer surface 62. In this arrangement, an
intermediate collar 63 having an interior surface 59 and an
exterior surface 61 can be provided.
[0146] The interior surface 59 of the collar 63 is eccentrally
located with respect to the exterior surface 61 and configured to
mate with the mounting surface 24. The exterior surface 61 is
desirably configured to mate with the interior surface 60 of the
artificial head 42. This arrangement also results in a
double-eccentric configuration.
[0147] In use, as seen in FIG. 16, the physician makes a cut 65
through the head 40 of the humerus 38 by conventional techniques.
Next, as shown in FIG. 17, an interior bore 64 is reamed in the
humerus 38 by conventional techniques to prepare the bone for
receiving the stem 46.
[0148] The stem 46, incorporating the system 10B, is then inserted
within the bore 64, as shown in FIG. 18. Tendons can then be
attached to the stem 46 using the tendon attachment holes 50 (not
shown).
[0149] The trial ring 48 is then placed on the mounting hub 18. The
eccentric interior hub 22 of the mounting hub 18, together with the
eccentric inner surface of the trial ring 48 form a
double-eccentric system, as shown in FIGS. 19a-19c. As represented
by arrows in FIGS. 19a and 19b, the trial ring 48 is then rotated
simultaneously with the mounting hub 18 until the desired position
relative to the cut surface of the humerus 38 is achieved (e.g.,
center of trial ring 48 is centered with cut surface of humerus
38).
[0150] As FIG. 19c shows, the trial ring 48 is also adapted to
rotate independently of the mounting hub 18.
[0151] Then, as shown in FIG. 20, the trial ring 48 is tilted
(represented by arrows and phantom lines in FIG. 20) with the
mounting hub 18 until the desired position relative to the cut is
achieved (e.g., parallel to cut).
[0152] As seen in FIG. 21, the mounting hub 18 is then secured in
the desired position by tightening (represented by arrow in FIG.
21) the locking screw 20, e.g., with an Allen wrench 30.
[0153] As also seen in FIG. 21, the physician can then make a mark
66 on the humerus 38 corresponding to the position of a given
reference marker 56 on the trial ring 48 when the mounting hub 18
is properly aligned.
[0154] For example, FIG. 21 illustrates a mark 66 made on the
humerus 38 corresponding to the position of reference marker "B"
when the trial ring 48 is properly aligned.
[0155] Next, as illustrated in FIG. 22, the artificial head 42 is
then orientated so that the desired reference marker on the
interior surface 60 of the artificial head 42 is aligned with the
mark 66 previously made on the humerus 38.
[0156] For example, FIG. 22 illustrates the reference marker "B" on
the interior surface 60 of the artificial head 42 being aligned
with the mark 66 previously made on the humerus 38.
[0157] The artificial head 42 is then placed (represented by
phantom lines in FIG. 22) on the mounting hub 18 in this desired
orientation.
[0158] Finally, as shown in FIG. 23, the physician seats and
secures the aligned artificial head 42 in place by hitting the
artificial head 42 with a hammer 68 to lock the tapers together
before placing the artificial head 42 into position within the
glenoid cavity.
III. Alternate Mounting Systems
[0159] A. Embodiment #1: Eccentric Mechanism
[0160] FIGS. 24a-29 detail an alternate embodiment of a shoulder
prosthesis mounting system 10C embodying features of the invention.
With reference to FIGS. 24a and 24b, the system 10C comprises a
stem 46, a pivot pin 12, a bottom eccentric insert 108, an
eccentric mount 110, a top eccentric insert 112, at least one
fastener 114, at least one guidepin 116, and an artificial head
42.
[0161] The stem 46 is a conventional stem suitable for implantation
into a humerus and serves to receive the pivot pin 12. The pivot
pin 12 comprises a ball component 118 and a post component 120. The
post 120 extends from the ball 118 and is sized to pass through the
mount 110 and an eccentric opening 122 on the bottom insert 108 to
mate with the stem 46, e.g., by threaded engagement (see e.g., FIG.
24a) or Morse taper (not shown).
[0162] In an alternate embodiment, the post 120 and the ball 118
are not integral. The post 120 is integral with the stem 46 and
extends from the stem 46. The ball 118 is configured to mate with
the post 120, e.g., by threaded engagement, and thus is selectively
removable from the post 120.
[0163] In either embodiment, the stem 46 is configured to carry the
post 120 such that the ball 118 protrudes at a pre-selected angle
from the stem 46, e.g., 35.degree.. Desirably, a portion of the
post 120 remains exterior to the stem 46, enabling the mount 110 to
pivot freely on the ball 118 (see FIG. 29).
[0164] The eccentric opening 122 is of a larger diameter than the
post 120 and sized to permit rotation of the mount 110 about the x,
y, and z axes, as will be described in greater detail later.
[0165] As seen in FIG. 25, the ball 118 is a spherical member sized
to rest on the eccentric opening 122 of the bottom insert 108. This
arrangement allows the ball 118 to serve as a pivot surface
permitting adjustment of the eccentric mount 110.
[0166] The eccentric mount 110 is a ring-like member having an
outer surface 124 and an inner surface 126, as seen in FIGS. 24a
and 24b. As best illustrated in FIG. 24b, the inner surface 126 of
the mount 110 is eccentric with respect to the outer surface 124.
This arrangement allows the head 42 to be positioned eccentrally
with respect to the mount 110. As FIGS. 25 and 26 show, the bottom
insert 108 has an outer surface 128 adapted to mate with the inner
surface 126 of the mount, e.g., by recessed slip fit that is free
to rotate.
[0167] With reference again to FIG. 26, at least one guidepin 116
extends from the bottom insert 108. In the illustrated embodiment,
three guidepins 116 are employed. The guidepins 116 are adapted to
pass through complementary guidepin holes 130 on the top insert 112
when the top and bottom inserts 112 and 108 are properly aligned.
Thus, the guidepins 116 serve to help align and secure the top and
bottom inserts 112 and 108.
[0168] As best seen in FIG. 24b, the top eccentric insert 112 has a
top surface 132 and a bottom surface 134. The bottom surface 134
has an eccentric recessed area 136 configured to mate with the ball
118. The top insert 112 is further adapted to rest on the bottom
insert 108.
[0169] As best shown in FIG. 26, the bottom and top inserts 112 and
108 each further comprise at least one fastener opening 138 adapted
for passage of a fastener 114, e.g., a screw. The fastener 114,
when tightened, serves to secure the mount 110 in a desired
position by compressing the top and bottom inserts 112 and 108
together around the ball 118 and the mount 110. The "stacking"
arrangement of the top and bottom inserts 112 and 108 serves to
maximize the surface area compressed, thereby aiding in securing
the mount 110 in a desired position.
[0170] The eccentric mount 110 along with the eccentric opening 122
of the bottom insert 108 and the eccentric recessed area 136 of the
top insert 112 provide a double-eccentric system.
[0171] The artificial head 42 serves as a prosthesis for the head
of a humerus, as previously described (see, e.g., FIG. 23). As FIG.
24b shows, the recessed interior surface 60 of the head 42 is
desirably concentric with respect to the outer surface 62 and is
threaded to mate with the outer surface 124 of the mount. Placement
of the head 42 onto the mount 110 secures the head to the mount 110
(see FIG. 28).
[0172] The system 10C provides at least five degrees of freedom,
thereby allowing a wide range of adjustment in multiple
dimensions.
[0173] First, as illustrated by arrows in FIGS. 27a-27b, the mount
110 can be rocked or rotated, i.e., tilted, about the x-axis (i.e.,
side to side rotation).
[0174] Second, as illustrated by arrows in FIGS. 27c-27d, the mount
110 can be rocked or rotated, i.e., tilted, about the y-axis (i.e.,
front to back rotation).
[0175] Third, as illustrated by arrows in FIG. 27e, the mount 110
can be rotated up to 360.degree. in either direction about the
z-axis.
[0176] Fourth and fifth, the double eccentric arrangement permits
translation of the linear position of points A1 and A2 with respect
to the pivot pin 12 when the inserts 108 and 112 and mount 110 are
rotated, as previously described for system 10B (see FIGS. 7 and
8). This action permits translation along the x and y axes.
[0177] The double-eccentric configuration serves to maximize the
range of translational adjustment possible under the fourth and
fifth types of movement.
[0178] In use, as shown in FIG. 25, the pivot pin 12 is passed
through the bottom insert 108 and the mount 110. The pivot pin 12
is then coupled to the stem 46, e.g., by screwing the post 120 into
the stem 46. As FIG. 26 shows, the top insert 112 is then aligned
with the bottom insert 108 by aligning the fastener openings 138 on
the top and bottom inserts 112 and 108, the guidepins 116 with the
guidepin holes 130, and the recessed area 136 with the ball
118.
[0179] The position of the mount 110 is then adjusted by rotating
or rocking the mount about the x, y, and z axes (see FIGS.
27a-27e). The fastener 114 is then tightened to secure the mount
110 in a desired position (not shown). Finally, the head 42 is
mounted onto the mount 110 (see FIGS. 28 and 29).
[0180] B. Embodiment #2: Disk Slide Mechanism
[0181] FIGS. 30a-34 detail another embodiment of a shoulder
prosthesis mounting system 10D embodying features of the invention.
With reference to FIGS. 30a and 30b, the system 10D comprises a
stem 46, a pivot pin 12, a mounting ring 140, a bottom disk 142, a
top disk 144, an artificial head 42, and a locking tool 146.
[0182] The stem is a conventional stem 46 and serves to receive a
pivot pin 12, as previously described for system 10C. The pivot pin
12 is similar in configuration to the pivot pin of System 10C. The
post 120 is adapted to pass through the bottom disk 142 and the
mounting ring 140 to mate with the stem 46, e.g., by threaded
engagement.
[0183] As FIG. 31 shows, the ball 118 is sized to rest within the
bottom disk 142. This arrangement allows the ball 118 to serve as a
pivot surface, thereby permitting adjustment of the mounting ring
140.
[0184] As best seen in FIG. 30a, the mounting ring 140 is comprised
of an outer ring 148 having a circular marginal surface and an
integrally-formed upstanding inner annular ring 150. The center of
the inner ring defines a chamber 152 and includes an opening 154
permitting passage of the post 120.
[0185] With reference again to FIG. 31, the chamber 152 is
configured to receive the bottom disk 142 and the ball 118. The
outer surface 156 of the inner ring 150 is desirably configured,
e.g., threaded, to mate with the interior surface 60 of the head
42.
[0186] In the illustrated embodiment, the inner ring 150 is
concentric with respect to the outer ring 148. However, the
invention also contemplates embodiments in which the inner ring 150
is eccentric with respect to the outer ring 148.
[0187] As best seen in FIG. 34, the center opening 154 of the
mounting ring 140 is of a larger diameter than the diameter of the
post 120 and sized to permit translation of the mounting ring 140
about the x and y axes and rotation about the z-axis, as will be
described in greater detail later.
[0188] As seen in FIG. 30a, the mounting ring 140 desirably has a
locking aperature 158. The aperature 158 is a bore that transverses
the circumferential margin of the mounting ring 140 and serves to
receive the locking tool 146. The locking tool 146 is configured
for insertion into the locking aperature 158 and allows rotation of
the mounting ring 140 to tighten the head 42 onto the mounting ring
140 (see also FIG. 34).
[0189] The bottom disk 142 is a ring-like member having an open
center permitting passage of the post 120 and is configured to rest
within the chamber 152 and receive the ball 118 (see FIGS. 30a-31).
It is further configured to receive the top disk 144, as
illustrated in FIG. 32.
[0190] Referring again to FIGS. 30a and 30b, the top disk 144 has a
top surface 160 and a bottom surface 162. The top surface 160 is
desirably flat or otherwise configured to permit compression of the
top and bottom disks 144 and 142 upon mounting of the head 42 onto
the mounting ring 140. The bottom surface 162 has a recessed area
164 configured to mate with the ball 118. The top disk 144 is
further configured to rest on the bottom disk 142 (see also FIG.
32).
[0191] This stacking arrangement permits compression of the top and
bottom disks 144 and 142 as the head 42 is mounted onto the
mounting ring 140 and serves to maximize the surface area
compressed, thereby securing the mounting ring 140 in a desired
position.
[0192] The artificial head 42 serves as a prosthesis for the head
of a humerus, as previously described. As seen in FIG. 30b, the
recessed interior surface 60 of the head 42 is desirably concentric
with respect to the outer surface 62 of the head 42. The invention
also contemplates, however, embodiments in which the interior
surface 60 is eccentric. The interior surface 60 of the head 42 is
also desirably threaded or otherwise configured to mate with the
inner ring 150 of the mounting ring 140.
[0193] Similar to system 10C, the system 10D provides at least five
degrees of freedom.
[0194] First, as illustrated by arrows in FIGS. 33a-33b, the
mounting ring 140 can be rocked or rotated, i.e., tilted, about the
x-axis (i.e., side to side rotation).
[0195] Second, as illustrated by arrows in FIGS. 33c-33d, the
mounting ring 140 can be rocked or rotated, i.e., tilted, about the
y-axis (i.e., front to back rotation).
[0196] Third, as illustrated by arrows in FIG. 33e, the mounting
ring 140 can be rotated up to 360.degree. in either direction about
the z-axis.
[0197] The difference between the outside diameter of the top and
bottom disks 144 and 142 and the inside diameter of recessed
chamber 152 forms a gap, as seen in FIG. 32. This arrangement
permits linear translation along the x-axis, providing a fourth
degree of freedom, and the y-axis, providing a fifth degree of
freedom.
[0198] In use, with reference to FIGS. 30a-32, the post 120 is
passed through the bottom disk 142 and the mounting ring 140. The
post 120 is then coupled to the stem 46, e.g., by screwing. The top
disk 144 is then aligned with the bottom disk 142 by aligning the
recessed area 164 with the ball. Next, the head 42 is mounted onto
the mounting ring 140.
[0199] The position of the head 42 is then adjusted by rotating and
rocking the head 42 about the x, y, and z axes (see FIGS. 33a-33e).
As FIG. 34 illustrates, the locking tool 146 is then inserted into
the locking aperture 158. As represented by arrows in FIG. 34, the
mounting ring 140 is then rotated by use of the locking tool 146 to
tighten the head 42 onto the mounting ring 140. This action places
all the components in compression and fixes the head 42 in
place.
[0200] C. Embodiment #3:
[0201] Slotted Mechanism
[0202] FIGS. 35a-40 detail another embodiment of a shoulder
prosthesis mounting system 10E embodying features of the invention.
With reference to FIGS. 35a and 35b, the system comprises a stem
46, a pivot pin 12), a bottom plate 166, a top plate 168, at least
one fastener 170, and at least one fastening element 172 for
securing the fastener 170.
[0203] The stem 46 and pivot pin 12 are configured as previously
described for systems 10C and 10D. The post 120 is adapted to pass
through the bottom plate 166 to mate with the stem 46, e.g., by
threaded engagement. The ball 118 is sized to rest on the bottom
plate 166. This arrangement allows the ball 118 to serve as a pivot
surface that permits adjustment of the bottom plate 166.
[0204] As shown in FIG. 36, the bottom plate 166 is a circular
member having a major axis A1 and a minor axis A2. An elongated
eccentric slot 174 is provided along the major axis A1. The bottom
plate 166 also provides a pair of elongated fixation slots 176
radially spaced from the center and parallel to the major axis A1.
The fixation slots 176 allow the position of the top plate 168 to
be laterally adjusted with respect to the bottom plate 166. The
fixation slots 176 also serve to receive fasteners 170, e.g.,
bolts, to secure the position of the top plate 168.
[0205] As shown in FIG. 37, the eccentric slot 174 receives the
ball 118 and allows lateral, i.e., side to side, adjustment
(represented by arrows and phantom lines in FIG. 37) of the
position of the ball 118 within the eccentric slot 174.
[0206] The bottom plate 166 includes a circumferential outer
surface 178 configured to mate with the head 42, e.g., by threaded
engagement (see e.g., FIG. 35b). The bottom plate 166 serves to
receive the top plate 168 in a stacked configuration.
[0207] Referring again to FIG. 36, the top plate 168 is a generally
elliptical member having a major axis A3 and a minor axis A4. The
major axis A3 parallels the minor axis A2 of the bottom plate 166
and the minor axis A4 parallels the major axis A1 of the bottom
plate 166 when the top plate 168 is aligned with bottom plate 166.
The top plate 168 further provides fastener receiving openings 180
sized and configured to receive the fasteners 170.
[0208] The top plate 168 further provides a top surface 182 and a
bottom surface 184. The top surface 182 is configured to receive a
fastening element 172 for the fastener 170, e.g., a nut. The bottom
surface 184 includes a recessed area 186 configured to mate with
the ball 118. The recessed area 186 desirably includes an opening
188 adapted for viewing the ball 118, thereby aiding in aligning
the top plate 168 with respect to the bottom plate 166. The top
plate 168 is further configured to rest on the ball 118, leaving a
gap between the top plate 168 and bottom plate 166.
[0209] The fasteners 170, when tightened, serve to secure the
plates 166 and 168 to the ball 118 in a desired position by
compressing the top and bottom plates 166 and 168 together. The
stacked arrangement of the plates 166 and 168 serves to maximize
the surface area compressed, thereby aiding in securing the plates
166 and 168 in the desired position relative to the ball 118.
[0210] The artificial head 42 serves as a prosthesis for the head
of a humerus, as previously described. The recessed interior
surface 60 of the head 42 is desirably concentric with respect to
the exterior surface 62 of the head 42, as shown in FIG. 35b. It
should be understood, however, that the invention also contemplates
embodiments in which the interior surface 60 is eccentric.
[0211] Similar to systems 10C and 10D, the system 10E provides at
least five degrees of freedom.
[0212] First, as illustrated by arrows in FIGS. 39a-39b, the bottom
plate 166 can be rocked or rotated, i.e., tilted, about the x-axis
(i.e., side to side rotation).
[0213] Second, as illustrated by arrows in FIGS. 39c-39d, the
bottom plate 166 can be rocked or rotated, i.e., tilted, about the
y-axis (i.e., front to back rotation).
[0214] Third, as illustrated by arrows in FIG. 39e, the bottom
plate 166 can be rotated up to 360.degree. in either direction
about the z-axis.
[0215] The slots 176 in the base 166 permit translation of the
linear position of the major axis A1 and minor axis A2 with respect
to the pivot pin 12 when the bottom plate 166 is slid along the x
axis, providing a fourth degree of freedom, or the y axis,
providing a fifth degree of freedom.
[0216] In assembling the system 10E, the post 120 is passed through
the eccentric slot 174 of the bottom plate 166, thereby resting the
ball 118 within the slot 174, as seen in FIG. 37. The bottom plate
166 is then slid (illustrated by arrows in FIG. 37) along the slot
174 until the desired lateral position is obtained. The fasteners
170 are then passed through the fixation slots 176 of the bottom
plate 166.
[0217] Next, the top plate 168 is aligned with the bottom plate 166
by aligning the recessed area 186 with the ball 118 and the
fastener receiving holes 180 with the fasteners 170. The fasteners
170 are then passed through the fixation slots 176 of the bottom
plate 166 and the fastener receiving openings 180 on the top plate
168. The top plate 168 is thereby positioned to rest on the ball
118 and over bottom plate 166, as FIG. 38 illustrates. The position
of the plates 166 and 168 is then adjusted by rotating or rocking
the bottom plate 166 about the x, y, and z axes (see FIGS.
39a-39e).
[0218] The components of the system 10E can be provided in a fully
assembled form in which the user only need tighten the fasteners
170 after adjusting the position of the plates 166 and 168 to
secure the plates 166 and 168 in the desired position.
[0219] Fastening elements 172, e.g., nuts, can be used if desired
to tighten and secure the fasteners 170. This action compresses the
plates 166 and 168 around the ball 118 to secure the plates 166 and
168 in the desired orientation and location relative to the ball
118.
[0220] Finally, as seen in FIG. 40, the head 42 is mounted onto the
bottom plate 166.
[0221] The foregoing is considered as illustrative only of the
principles of the invention. Furthermore, since numerous
modifications and changes will readily occur to those skilled in
the art, it is not desired to limit the invention to the exact
construction and operation shown and described. While the preferred
embodiment has been described, the details may be changed without
departing from the invention, which is defined by the claim.
* * * * *