U.S. patent application number 11/689470 was filed with the patent office on 2007-09-27 for femoral and humeral stem geometry and implantation method for orthopedic joint reconstruction.
This patent application is currently assigned to Axiom Orthopaedics, Inc.. Invention is credited to Leo M. Reubelt, Peter L. Verrillo.
Application Number | 20070225821 11/689470 |
Document ID | / |
Family ID | 38523099 |
Filed Date | 2007-09-27 |
United States Patent
Application |
20070225821 |
Kind Code |
A1 |
Reubelt; Leo M. ; et
al. |
September 27, 2007 |
FEMORAL AND HUMERAL STEM GEOMETRY AND IMPLANTATION METHOD FOR
ORTHOPEDIC JOINT RECONSTRUCTION
Abstract
The present inventions relate to devices and methods that
improve the positioning and fit of orthopedic reconstructive joint
replacement stem implants relative to existing methods. For
example, an embodiment of the device provides a stem component
comprising proximal and distal body portions that can be configured
to mimic a geometric shape of a central cavity region created in a
bone of a joint for improving conformance and fixation of the stem
component thereto. Further, another embodiment provides a system of
stem implants that each have a unique medial offset for
facilitating the matching of an implant to the geometry of a
central cavity region of a bone. Additionally, an inclination angle
of a resection surface of each of the implants in the system can
remain constant or vary as a function of the medial offset.
Inventors: |
Reubelt; Leo M.; (Hawthorne,
NJ) ; Verrillo; Peter L.; (Wood Ridge, NJ) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
Axiom Orthopaedics, Inc.
Jersey City
NJ
|
Family ID: |
38523099 |
Appl. No.: |
11/689470 |
Filed: |
March 21, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60784236 |
Mar 21, 2006 |
|
|
|
Current U.S.
Class: |
623/22.41 ;
606/80; 623/19.14; 623/23.35 |
Current CPC
Class: |
A61F 2/4059 20130101;
A61B 2017/0046 20130101; A61B 2090/062 20160201; A61F 2002/30538
20130101; A61F 2002/30604 20130101; A61B 17/1668 20130101; A61F
2250/0006 20130101; A61F 2002/30332 20130101; A61B 17/164 20130101;
A61F 2/36 20130101; A61F 2002/3054 20130101; A61F 2002/4051
20130101; A61F 2220/0033 20130101; A61B 17/1659 20130101; A61F
2002/30616 20130101; A61F 2002/4018 20130101; A61F 2002/4077
20130101; A61B 2017/00464 20130101; A61F 2/3662 20130101; A61F
2002/3631 20130101; A61F 2002/30607 20130101; A61F 2002/3625
20130101; A61F 2250/0062 20130101; A61F 2/40 20130101; A61B 17/1684
20130101; A61F 2002/4062 20130101 |
Class at
Publication: |
623/022.41 ;
623/023.35; 606/080; 623/019.14 |
International
Class: |
A61F 2/36 20060101
A61F002/36; A61B 17/16 20060101 A61B017/16; A61F 2/40 20060101
A61F002/40 |
Claims
1. A system of orthopedic devices for joint reconstruction surgery,
the system comprising: a plurality of stem components, each stem
component comprising a distal body portion configured to be
inserted into a central cavity region created in a bone of the
joint and a proximal body portion, the distal body portion defining
a longitudinal axis, the proximal body portion defining a bearing
surface for supporting a hemispherical head component that in turn
has a geometric head center positioned within the proximal portion,
the head center being spaced from the longitudinal axis at a medial
offset distance and the bearing surface oriented at an inclination
angle with respect to the longitudinal axis; wherein each stem
component of the system is configured such that as the medial
offset decreases the inclination angle increases.
2. The system of claim 1, wherein the system includes at least
three stem components.
3. The system of claim 2, wherein a first stem component has a
medial offset of approximately 12 mm, a second stem component has a
medial offset of approximately 8 mm, and a third stem component has
a medial offset of approximately 5 mm.
4. The system of claim 3, wherein the first stem component has an
inclination angle of approximately 45 degrees, the second stem
component has an inclination angle of approximately 41 degrees, and
the third stem component has an inclination angle of approximately
37 degrees.
5. The system of claim 1 wherein each of the stem components of the
system has a medial offset of between approximately 4 mm and
approximately 20 mm.
6. The system of claim 5, wherein the inclination angle is between
approximately 30 degrees and approximately 55 degrees
7. The system of claim 1, wherein the distal body component and the
proximal body component form a single piece.
8. A system of orthopedic devices for joint reconstruction surgery,
the system comprising: a plurality of stem components, each stem
component comprising a distal body portion configured to be
inserted into a central cavity region created in a bone of the
joint and a proximal body portion, the distal body portion defining
a longitudinal axis, the proximal body portion defining a bearing
surface for supporting a hemispherical head component that in turn
has a geometric head center positioned within the proximal portion,
the head center being spaced from the longitudinal axis at a medial
offset distance and the bearing surface oriented at an inclination
angle with respect to the longitudinal axis; wherein each stem
component of the system is configured such that as the medial
offset increases the inclination angle remains substantially
constant.
9. The system of claim 8, wherein the system includes at least four
stem components.
10. The system of claim 8, wherein a first stem component has a
medial offset of approximately 5 mm, a second stem component has a
medial offset of approximately 7 mm, a third stem component has a
medial offset of approximately 9 mm and the fourth stem component
has a medial offset of approximately 11 mm.
11. The system of claim 8, wherein each of the stem components of
the system has a medial offset of between approximately 4 mm and
approximately 20 mm.
12. The system of claim 8, wherein the inclination angle is fixed
between approximately 30 degrees and approximately 55 degrees.
13. The system of claim 8, wherein the distal body component and
the proximal body component form a single piece.
14. A method of implanting an orthopedic reconstructive joint
replacement stem implant, the method comprising: resecting a head
of a bone of a joint; using a single instrument to successively
broach and ream a central cavity region in the bone of the joint;
and inserting a proximal body portion of the stem implant into the
central cavity region of the bone of the joint.
15. The method of claim 14, further comprising the step of
resecting a neck of the bone of the joint.
16. The method of claim 15, wherein the bone is a femur.
17. The method of claim 14, wherein the joint is a hip joint.
18. The method of claim 14, wherein the joint is a shoulder
joint.
19. The method of claim 14, wherein the bone is a humerus.
20. A method of implanting an orthopedic reconstructive joint
replacement stem implant, the method comprising: resecting a head
of a bone of a joint; broaching a central cavity region in the bone
of the joint; and inserting a proximal body portion of the stem
implant into the central cavity region of the bone of the joint
without damaging the supraspinatus.
21. An instrument for creating a central cavity region in a bone of
a joint, the instrument comprising: a reaming section being
disposed at a distal end of the instrument, the reaming section
being sized and configured to facilitate reaming of the bone; a
broaching section being disposed axially adjacent to the reaming
section and being sized and configured to facilitate broaching of
the central cavity region of the bone successive to the reaming of
the bone by the reaming section; and a handle being disposed at a
proximal end of the instrument and being coupled to the reaming and
broaching sections for facilitating driving of the reaming and
broaching sections.
22. An orthopedic device for joint reconstruction, the device
comprising: a stem comprising a distal body portion, a proximal
body portion, and an attachment portion, the stem component being
sized and configured to be implanted to within a central cavity
region of a bone, the bone defining a geometric shape, the stem
component tapering from the proximal body portion toward the distal
body portion to define medial and lateral curved surfaces, the
medial and lateral curved surfaces being configured to mimic the
geometric shape of the bone for improving conformance and fixation
of the stem component to the central cavity region of the bone,
wherein the proximal body of the stem component is inserted into a
central cavity region created in the bone of a joint.
23. The device of claim 22, wherein the attachment portion is
tapered.
24. The device of claim 22, wherein a longitudinal axis of the
distal body portion is oriented at a discrete angle with respect to
a neck axis of the proximal body portion.
25. The device of claim 22, wherein the bone is a humerus.
26. The device of claim 25, wherein the humerus comprises a
proximal portion having a shape and a distal portion.
27. The device of claim 26, wherein the proximal body shape
conforms to the shape of claim 22, wherein the distal body portion
of the stem component has a tapered shape.
28. The device of claim 22, wherein the distal section of the stem
component has a cylindrical, elliptical or irregular shape.
29. The device of claim 22, wherein the distal body portion of the
stem component further comprises at least one feature selected from
the group consisting of: a groove, a slot, a cutout, and a
protrusion.
Description
PRIORITY INFORMATION
[0001] The present application claims the priority benefit under 35
U.S.C. .sctn. 119(e) to U.S. Provisional Application 60/784,236,
filed Mar. 21, 2006, the entire contents of which are expressly
incorporated by reference herein.
BACKGROUND
[0002] 1. Field of the Inventions
[0003] The present inventions relates generally to orthopedic
implants, and more specifically, to a reconstructive joint
replacement implant and a method of positioning and fitting such an
implant.
[0004] 2. Description of the Related Art
[0005] Anatomically, a joint is generally a movable junction
between two or more bones. As used herein, the term "joint" is a
broad term that is meant to include the different kinds of
ligaments, tendons, cartilages, bursae, synovial membranes and
bones comprising the mobile skeletal system of a subject in various
quantities and configurations.
[0006] For example, the hip joint is a ball and socket joint
comprising the "ball" at the head of the thigh bone (femur) with a
cup-shaped "socket" (acetabulum) in the pelvic bone. The ball
normally is held in the socket by powerful ligaments that form a
complete sleeve around the joint (i.e., the joint capsule). The
joint capsule has a delicate lining (the synovium). Cartilage,
which covers the head of the femur and lines the socket, cushions
the joint, and allows the bones to move on each other with very
little friction. In a normal hip joint, the spherical head of the
thighbone (femur) moves inside the acetabulum of the pelvis.
Normally, all of these components replace the worn-out hip
socket.
[0007] The shoulder is the body's most mobile joint, in that it can
turn in many directions. The shoulder is a ball-and-socket joint
that is made up of three bones: the upper arm bone (humerus),
shoulder blade (scapula) and collarbone (clavicle). In the
shoulder, two joints facilitate shoulder movement. The
acromioiclavicular (AC) joint joins one end of the collarbone with
the shoulder blade; it is located between the acromion (the part of
the scapula that forms the highest point of the shoulder) and the
clavicle. The other end of the collarbone is joined with the
breastbone (sternum) by the sternoclavicular joint. The
glenohumeral joint, commonly called the shoulder joint, is a
ball-and-socket type joint that helps move the shoulder forward and
backward and allows the arm to rotate in a circular fashion or
hinge out and up away from the body. The ball of glenohurneral
joint is the top, rounded portion of the humerus; the socket, or
glenoid, is a dish-shaped part of the outer edge of the scapula
into which the ball fits. The socket of the glenoid is surrounded
by a soft-tissue ring of fibrocartilage (the glenoid labrum) that
runs around the cavity of the scapula (glenoid cavity) in which the
head of the humerus fits. The labrum deepens the glenoid cavity and
effectively increases the surface of the shoulder joint, which
helps stabilize the joint.
[0008] The bones of the shoulder are held in place by muscles,
tendons (tough cords of tissue that attach the shoulder muscles to
bone and assist the muscles in moving the shoulder) and ligaments
(bands of fibrous tissue that connects bone to bone or cartilage to
bone, supporting or strengthening a joint). A smooth, durable
surface (the articular cartilage) on the head of the arm bone, and
a thin lining (synovium) allows smooth motion of the shoulder
joint. The joint capsule, a thin sheet of fibers that encircles the
shoulder joint, allows a wide range of motion yet provides
stability of the joint. The capsule is lined by a thin, smooth
synovial membrane. The front of the joint capsule is anchored by
three geneohumeral ligaments.
[0009] The rotator cuff, a structure composed of tendons and
associated muscles that holds the ball at the top of the humerus in
the glenoid socket, covers the shoulder joint and joint capsule.
The rotator cuff provides mobility and strength to the shoulder
joint. A sac-like membrane (bursa) between the rotator cuff and the
shoulder blade cushions and helps lubricate the motion between
these two structures.
[0010] The shoulder is an unstable joint easily subject to injury
because of its range of motion, and because the ball of the humerus
is larger than the glenoid that holds it. To remain stable, the
shoulder must be anchored by its muscles, tendons and ligaments.
Some shoulder problems arise from the disruption of these soft
tissues due to injury or overuse, or underuse of the shoulder.
Other problems can arise from degenerative processes.
[0011] For example, instability of the shoulder joint can refer to
situations that occur when one of the shoulder joints moves or is
forced out of its normal position. The two basic forms of shoulder
instability are subluxations and dislocations. A partial or
incomplete dislocation of the shoulder joint (subluxation) means
the head of the humerus is partially out of the socket (glenoid). A
complete dislocation of the shoulder joint means that the head of
the humerus is completely out of the socket. Anterior instability,
for example, can refer to a type of shoulder dislocation where the
shoulder slips forward, meaning that the humerus moved forward and
down out of its joint. Anterior instability may occur when the arm
is placed in a throwing position. Both partial and complete
dislocation cause pain and unsteadiness in the shoulder joint.
Patients with repeat dislocation usually require surgery.
[0012] Bursitis or tendonitis can occur with overuse from
repetitive activities, which cause rubbing or squeezing
(impingment) of the rotator cuff under the acromion and in the
acromioclavicular joint. Partial thickness rotator cuff tears, most
often the result of heavy lifting or falls, can be associated with
chronic inflammation and the development of spurs on the underside
of the acromion or the AC joint. Full thickness rotator cuff tears
most often are the result of impingement.
[0013] Osteoarthritis and rheumatoid arthritis can cause
destruction of the shoulder joint and surrounding tissue and
degeneration and tearing of the capsule or rotator cuff. In
osteoarthritis, the articular surface of the joint wears thin.
Rheumatoid arthritis is associated with chronic inflammation of the
synovium lining, which can produce substances that eventually
destroy the inner lining of the joint, including the articular
surface.
[0014] Shoulder replacement is recommended for subjects with
painful shoulders and limited motion. The treatment options are
either replacement of the head of the humerus or replacement of the
entire socket. However, currently available treatment options are
less than adequate in restoring shoulder joint function. For
example, just as muscles get stronger through use, the density and
strength of bone varies with respect to the bone's load history. To
ensure proper bone loading and good bone health, accurate implant
placement, good bone fit, and restoration of a healthy anatomic
position is critical. Existing devices have focused on modifying
only the most proximal portion of the stem geometry, known as the
neck, to adjust for different angles but do not accommodate
variation of the proximal body shape.
SUMMARY
[0015] Currently, most humeral stems are implanted using a fairly
common procedure. First the head is resected and the humeral canal
is reamed to a best fit diameter. The humerus is then broached or
reamed, using the canal as a guide, to accept the proximal body.
One aspect of the present inventions is that this method poses
several basic problems. First, because the distal stem is meant to
be a tight fit with respect to the reamed cavity, it dictates the
position of the stem and therefore, the position of the head. Since
the size, location, and orientation of the head with respect to the
humeral canal vary greatly from person to person, a single stem
geometry per size cannot accommodate natural head placement or
proximal body shape. Consequently, head placement is typically
adjusted by rotating the prosthetic head around an eccentric taper.
This typically results in a proximal fit that is poor because
rotating an eccentric head adjusts both posterior and medial head
location at the same time, virtually excluding the possibility of
perfect placement. Similarly, since proximal body position and
orientation are governed by the distal canal, the proximal body
must be made small enough to fit the smallest possible envelope
within the proximal humerus. This excessively small proximal body
causes poor proximal fixation and leads to over-reliance on distal
fixation. Over time, when too much emphasis is placed on distal
fixation, the strength of the proximal bone begins to deteriorate.
This, in turn leads to stem loosening and potentially fracture.
While some companies have tried to improve upon this model by
offering different neck angles, they typically use the same
proximal body geometry and simply vary the resection angle. While
this may improve head center placement, it offers little to
accommodate varying shapes of the proximal body.
[0016] Accordingly, an embodiment of the present inventions is an
orthopedic device for joint reconstruction that comprises an
implantable stem component comprising a proximal section or
proximal body portion. The proximal body of the stem component can
be inserted into a central cavity region created in a bone of a
joint. According to one aspect, the orthopedic device optionally
comprises a distal section or distal body portion, wherein the
distal section of the implantable stem component is placed at least
one distal stem angle with respect to the proximal body component
of the implantable stem component of the device. In this regard, a
longitudinal axis of the distal body portion can be oriented at a
discrete angle with respect to a neck axis of the proximal body
portion.
[0017] In accordance with another embodiment, the stem component
can taper from the proximal body portion toward the distal body
portion to define medial and lateral curved surfaces. The medial
and lateral curved surfaces can be configured to mimic the
geometric shape of the bone for improving conformance and fixation
of the stem component to the central cavity region of the bone. In
this regard, the proximal body of the stem component can be
inserted into a central cavity region created in the bone of a
joint. The attachment portion can be tapered. Further, the bone can
be a humerus. The humerus can comprise a proximal portion having a
shape and a distal portion. The medial and lateral curved surfaces
can conforms to the shape of the proximal portion of the implant.
Further, the distal section of the stem component can have a
cylindrical, elliptical, tapered, or irregular shape. Additionally,
the distal body portion of the stem component can further comprise
at least one feature selected from the group consisting of: a
groove, a slot, a cutout, and a protrusion.
[0018] According to another aspect, the joint is a hip joint.
According to another aspect, the joint is a shoulder joint.
According to another aspect, the bone is a humerus. According to
another aspect, the humerus comprises a proximal portion having a
shape and a distal portion. According to another embodiment, the
proximal body shape of the device conforms to the shape of the
proximal portion of the humerus. According to another aspect, the
bone is a femur. According to another aspect, the distal section of
the stem component of the device has a tapered shape. According to
another aspect, the distal section of the stem component of the
device has a cylindrical, elliptical, tapered, or irregular shape.
According to another aspect, the distal section of the stem
component of the device further comprises at least one feature
selected from the group consisting of a groove, a slot, a cutout,
and a protrusion. According to another aspect, the distal section
of the stem component of the device further comprises a ball.
[0019] In another embodiment, a system of orthopedic devices for
joint reconstruction surgery is provided. The system can comprise a
plurality of stem components, wherein each stem component
comprising a distal body portion and a proximal body portion. The
stem component can be sized and configured to be implanted to
within a cavity of a bone. The distal body portion can define a
longitudinal axis, and the proximal body portion can define a neck
axis and a head center. Further, the proximal body portion can
comprise a resection surface. The head center can be spaced from
the longitudinal axis at a medial offset, and the resection surface
can be oriented at an inclination angle with respect to the
longitudinal axis. In such an embodiment, each stem component of
the system can be configured with a different medial offset when
compared to other of the stem components of the system. The system
can thus provide a variety of potential matching geometries for a
surgeon when performing the joint reconstruction surgery. The
proximal body of a given stem component can be insertable into a
central cavity region created in a bone of the joint.
[0020] In an embodiment of the system, each stem component of the
system can have the same inclination angle. Further, the
inclination angle of each stem component can vary as a function of
the medial offset of the respective stem component. In some
embodiments, the system can be configured such that each of the
stem components of the system has a medial offset of between
approximately 4 mm and approximately 15 mm. In addition, in other
embodiments, the medial offset can be varied while the inclination
angle is constant.
[0021] The system can include, for example, at least three stem
components. Accordingly, a first stem component can have a medial
offset of approximately 12 mm, a second stem component can have a
medial offset of approximately 8 mm, and a third stem component can
have a medial offset of approximately 5 mm. Additionally, the first
stem component can have an inclination angle of approximately 44
degrees, the second stem component can have an inclination angle of
approximately 49 degrees, and the third stem component can have an
inclination angle of approximately 54 degrees. The inclination
angle can be between approximately 30 degrees and approximately 55
degrees.
[0022] Further, in a method of implanting an orthopedic
reconstructive joint replacement stem implant is also provided in
accordance with another embodiment. The method can comprise:
resecting a head of a bone of a joint; using a single instrument to
successively broach and ream a central cavity region in the bone of
the joint; and inserting a proximal body portion of the stem
implant into the central cavity region of the bone of the joint. In
particular, embodiments disclosed herein can facilitate the
insertion of the proximal body portion into the central cavity
region of the bone of the joint can be performed without damaging
the supraspinatus. The method can further comprise the step of
resecting a neck of the bone of the joint. In this method, the bone
can be, for example, a femur or a humerus. Also, the joint can be,
for example, a hip joint or a shoulder joint.
[0023] Another embodiment of the method can further comprise the
step of selecting a stem implant in response to a geometric shape
of the central cavity region of the bone. As mentioned above with
respect to an embodiment of the stem implant, the stem implant can
taper from the proximal body portion toward a distal body portion
to define medial and lateral curved surfaces. Thus, the method can
be implemented such that the medial and lateral curved surfaces can
be configured to mimic the geometric shape of the central cavity
region of the bone for improving conformance and fixation of the
stem implant to the central cavity region of the bone.
[0024] In yet another embodiment, an instrument is provided for
creating a central cavity region in a bone of a joint. The
instrument comprises a broaching section, a reaming section, and a
handle. The reaming section can be disposed at a distal end of the
instrument. The reaming section can be sized and configured to
facilitate reaming of the bone. The broaching section can be
disposed axially adjacent to the reaming section and can be sized
and configured to facilitate broaching of the central cavity region
of the bone successive to the reaming of the bone by the reaming
section. The handle can be disposed at a proximal end of the
instrument and being coupled to the broaching and reaming sections
for facilitating driving of the broaching and reaming sections.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a side cross-sectional view of a prior art implant
with a distal stem inserted into a humeral canal.
[0026] FIG. 2 is top view schematic illustration of a prior art
eccentric head, which is used to adjust medial and posterior
offset.
[0027] FIG. 3 is a cross-sectional side cross-sectional view of a
prior art implant.
[0028] FIG. 4 is a side view of a humeral bone and implant
illustrating stem fracture.
[0029] FIG. 5A is a side view of a prior art implant illustrating a
unique head orientation of a proximal portion thereof.
[0030] FIG. 5B is a side view of another prior art implant
illustrating a unique head orientation of a proximal portion
thereof.
[0031] FIG. 6A is a side view of an embodiment of a humeral stem
having certain features and advantages according to the present
inventions.
[0032] FIG. 6B is a side view of another embodiment of a humeral
stem having certain features and advantages.
[0033] FIG. 7 is a side view of a humeral stem positioned within a
proximal humerus, according to another embodiment.
[0034] FIG. 8 is a schematic illustration of a proximal end of a
broach, according to an embodiment.
[0035] FIG. 9A illustrates a humeral stem, according to another
embodiment.
[0036] FIG. 9B illustrates a femoral stem, according to another
embodiment.
[0037] FIG. 10A is a side view of an embodiment of the stem wherein
a proximal body portion thereof is oriented at an inclination angle
with respect to a distal body portion thereof.
[0038] FIG. 10B is a side view of another embodiment of the stem
wherein the proximal body portion is oriented at another
inclination angle with respect to the distal body portion.
[0039] FIG. 10C is a side view of yet another embodiment of the
stem wherein the proximal body portion is oriented at yet another
inclination angle with respect to the distal body portion.
[0040] FIG. 10D is a side view of yet another embodiment of the
stem wherein the proximal body portion is oriented at yet another
inclination angle with respect to the distal body portion.
[0041] FIG. 11A is a side view of an implant of a system of
implants wherein an inclination angle of the implant changes
relative to a medial offset thereof, according to an
embodiment.
[0042] FIG. 11B is a side view of another implant of the system,
according to another embodiment.
[0043] FIG. 11C is a side view of yet another implant of the
system, according to yet another embodiment.
[0044] FIG. 12 shows how the broach can be inserted into the
humerus.
[0045] FIG. 13 shows the broach when it is fully inserted to the
correct size marking.
[0046] FIG. 14 shows a stem with a shortened distal region.
[0047] FIG. 15 shows how a reamer is inserted into a broached
humeral cavity.
[0048] FIG. 16 shows how the broach is guided by the conforming
proximal humerus.
[0049] FIG. 17 shows an instrument that combines a broach and a
reamer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0050] As used herein, the term "stem" is a broad term that is used
to designate a device that is implanted into the bone for the
purpose of supporting a functional component of a joint replacement
and resisting the loads applied to the functional component. For
example, a stem can be a device implanted into a humerus or femur
to support a modular prosthetic humeral or femoral head (i.e. the
supported structure). In other embodiments, the supported structure
can be an integral part of the stem, as with a monolithic stem and
head. Femoral and humeral stems typically include distal and
proximal sections as well as a taper or other coupling device to
which the functional component is attached. Additionally, femoral
stems typically include a neck section that extends the distance
between the proximal section and the head. The neck is not embedded
in the bone, but sits proud. As used herein, the term "neck" can
refer to the portion of a femoral stem that does not reside within
the femur bone, and extends the distance between the proximal body
and the head.
[0051] As used herein, the term "proximal body" can refer to the
portion of the humeral or femoral stem that resides within the bone
and is nearer to the head (more proximal). The proximal limit of
the proximal body is typically denoted by the resection plane or
coupling device. The distal limit of the proximal body is typically
denoted by a transition from a substantially diverging shape to a
slightly diverging or substantially elongated shape. These shapes
are intended to somewhat mimic the shapes of the bone in their
corresponding locations.
[0052] As used herein, the term "distal region" can refer to the
portion of the humeral or femoral stem that resides in the bone and
is farther from the head. The proximal limit of the distal region
is typically denoted by a transition from a slightly diverging or
substantially elongated shape, to a substantially diverging shape.
These shapes are intended to somewhat mimic the shapes of the bone
in their corresponding locations.
[0053] As used herein, the term "distal stem angle" can refer to
the angle between the best fit central axis of the distal region of
the stem and the resection plane.
[0054] As used herein, the term "cavity" can refer to the entire
prepared hole in which the stem will be implanted. When the cavity
is referred to as "central," a proximal location is implied because
the distal humerus and femur are very elongated distally and
consequently dictate central placement.
[0055] As used herein, the term "bone canal" can refer to the
portion of the humerus or femur that is substantially elongated and
accepts the distal region of the stem. The proximal limit of the
distal region is typically denoted by a transition from a slightly
diverging or substantially elongated shape, to a substantially
diverging shape.
[0056] As used herein, the term "broach" can refer to a bonecutting
tool comprising a series of progressively taller points mounted on
a single piece of metal, typically used to enlarge a circular hole
into a larger noncircular shape such as a square or other desired
shape. The amount of material removed by each broach tooth (or
chisel) varies with the material being cut. A broach also may also
be designed to be pushed or pulled through an existing hole. The
term "broaching" as used herein, can refer to this bone-removal
process.
[0057] As used herein, the term "reaming" can refer to a process
whereby a hole is enlarged to an accurate size. Although generally
reaming must be preceded by a drilling or boring operation, that is
not true in embodiments disclosed herein, for example, where the
starting material is a hole or other shape that is being cleaned
up. Reaming can also be performed on surfaces such as a sphere or
other concave or convex surfaces as it is when a glenoid is reamed
with a spherical reamer. The term "resect," "resecting," or
"resection" as used herein can refer to a process whereby a portion
of a structure is cut off or cut out.
[0058] The term "subject" as used herein includes animals of
mammalian origin, including humans. When referring to animals that
typically have one end with a head and mouth, with the opposite end
often having the anus and tail, the head end is referred to as the
cranial end, while the tail end is referred to as the caudal end.
Within the head itself, rostral can refer to the direction toward
the end of the nose, and caudal is used to refer to the tail
direction. The surface or side of an animal's body that is normally
oriented upwards, away from the pull of gravity, is the dorsal
side; the opposite side, typically the one closest to the ground
when walking on all legs, swimming or flying, is the ventral side.
On the limbs or other appendages, a point closer to the joint
contact is "proximal"; a point farther away is "distal." This
principle shall be followed in relation to embodiments of the
apparatuses disclosed herein; a point closer to the main body of
the apparatus shall be referred to as "proximal;" a point farther
away shall be referred to as "distal."
[0059] Three basic reference planes are used in zoological anatomy.
A "sagittal" plane divides the body into left and right portions.
The "midsagittal" plane is in the midline, i.e. it would pass
through midline structures such as the spine, and all other
sagittal planes are parallel to it. A "coronal" plane divides the
body into dorsal and ventral portions. A "transverse" plane divides
the body into cranial and caudal portions.
[0060] When referring to humans, the body and its parts are always
described using the assumption that the body is standing upright.
Portions of the body which are closer to the head end are
"superior" (corresponding to cranial in animals), while those
farther away are "inferior" (corresponding to caudal in animals).
Objects near the front of the body are referred to as "anterior"
(corresponding to ventral in animals); those near the rear of the
body are referred to as "posterior" (corresponding to dorsal in
animals). A transverse, axial, or horizontal plane is an X-Y plane,
parallel to the ground, which separates the superior/head from the
inferior/feet. A corona] or frontal plane is an Y-Z plane,
perpendicular to the ground, which separates the anterior from the
posterior. A sagittal plane is an X-Z plane, perpendicular to the
ground and to the corona] plane, which separates left from right.
The midsagittal plane is the specific sagittal plane that is
exactly in the middle of the body.
[0061] Structures near the midline are called medial and those near
the sides of animals are called lateral. Therefore, medial
structures are closer to the midsagittal plane, lateral structures
are further from the midsagittal plane. Structures in the midline
of the body are median. For example, the tip of a human subject's
nose is in the median line.
[0062] Ipsilateral means on the same side, contralateral means on
the other side and bilateral means on both sides. Structures that
are close to the center of the body are proximal or central, while
ones more distant are distal or peripheral. For example, the hands
are at the distal end of the arms, while the shoulders are at the
proximal ends.
[0063] A symmetric subject is assumed when the terms "medial,"
"lateral," "inferior," "superior," "anterior," and "posterior," are
used to refer to an implant.
[0064] Embodiments disclosed herein relate to a method that can
improve the positioning and fit of orthopedic reconstructive joint
replacement implants. One of the goals in performing an orthopedic
reconstructive joint replacement is to place a stem implant
centrally within the bone and to provide good proximal fill. This
not only more evenly loads the bone, but also eliminates the need
for head position adjustment. Although specific explanations will
refer to either the shoulder (humerus) or the hip (femur), the
methods disclosed herein are mutually exclusive and can be used
alone or in combination as a general method for reconstructing
joints.
[0065] As will be described further herein, the embodiments of the
stem implants and the methods for implantation and adjustment of
the stem implants provide numerous advantages over the prior art.
For example, referring to FIG. 1, a prior art stem implant 10 that
is implanted into a humerus bone 12 is shown. During the
implantation, a head 14 of the humerus bone 12 is resected in order
to accommodate a tool (not shown) used to ream or broach a humeral
canal 16 of the bone 12 in preparation for implantation. Once
reamed, the humeral canal 16 defines a best fit diameter. The
humeral canal 16 of the humerus bone 12 is then used as a guide to
accept the stem implant 10. The stem implant 10 can include distal
and proximal body portions 20, 22. In this regard, the distal body
portion 22 of the stem implant 10 is inserted into the humeral
canal 16 until the distal body portion 22 is tightly fitted into a
distal area of the humeral canal 16. Additionally, the proximal
body portion 20 or head portion of the stem implant 10 is
positioned in a proximal area 23 of the humeral canal 16.
[0066] This prior art method poses several basic problems. First,
because the distal body portion 22 is configured to form a tight
fit with respect to the reamed humeral canal 16, the canal 16
dictates the position of the distal body portion 22 and therefore,
the position of the proximal body portion 20 of the implant 10.
Further, the proximal body portion 20 of such prior art implants
does not fill the proximal area 23 of the humeral canal 16, and
causes detrimental reliance on distal stem geometry and fit, as
described below. With reference to FIG. 2, since the size,
location, and orientation of the head portion 45 with respect to
the humeral canal 16 vary greatly from person to person, a single
stem geometry per size cannot accommodate natural placement or
shape of the head portion 45. Consequently, as shown in the top
axial view of the implant 10 of FIG. 2, adjustment of the
positioning of the head portion 45 is often made by rotating the
implant 10, for example, from a first position 40 to a second
position 42 around an eccentric taper 44. Consequently, proximal
fit of the head portion 45 on or in a resection plane 24 (shown in
FIG. 1) of the humerus 12 is typically poor. Unfortunately,
rotating an eccentric head 45 adjusts both posterior 46 and medial
48 head location at the same time, virtually excluding the
possibility of perfect placement.
[0067] An additional problem in the prior art is that the position
and orientation of the proximal body portion 20 are governed by the
distal area of the canal 16, as shown in FIG. 3. As such, the
proximal body portion 20 must be made small enough to fit the
smallest possible envelope within the proximal area of the humerus
12. An excessively small proximal body portion 20 can cause poor
proximal fixation of the implant 10 to the humerus 12 and lead to
over-reliance on distal fixation of the implant 10. Over time, when
too much emphasis is placed on distal fixation, the strength of the
proximal area of the bone 12 begins to deteriorate. This, as shown
in FIG. 4, can lead to loosening of the stem implant 10 and
potentially fracture of the implant 10.
[0068] While some companies have tried to improve upon this model
by offering different neck angles, such as with implants 50 having
different configurations, as illustratively shown in FIGS. 5A-B. As
illustrated, such implants 50 use the same geometry for the
proximal body portion 52 and simply vary a resection angle 54 of
the implant 50. While this may improve placement of the head
portion, it offers little to accommodate varying shapes of the
proximal body portion 52.
[0069] In contrast, according several embodiments of the present
inventions, it is contemplated that an angle of a distal section of
a stem implant can be varied with respect to an entire proximal
body instead of changing an angle of a resection cut or a neck.
This means that, for different distal angles, the proximal body
will move with respect to the humeral canal.
[0070] Referring now to FIGS. 6A-B, an embodiment of a stem implant
100 is shown. The stem implant 100 defines a proximal body 102 and
a distal body 104. In FIG. 6A, it is illustrated that in some
embodiments, the distal body 104 of the implant 100 can be
configured at a variety of angular orientations 106', 106'', 106'''
relative to the proximal body 102. The result, as shown in FIG. 6B,
is that the proximal body 102 of the implant 100 can be configured
at a variety of angular orientations 108', 108'', 108''' relative
to the proximal body 102. Thus, it is contemplated that in some
embodiments, a plurality of implants 100 can be provided to a
surgeon such that the surgeon can select one of the implants 100
depending on the configuration required for the implant procedure.
In another embodiment, the surgeon can be provided with a kit that
comprises a variety of implants 100 with a variety of angular
orientations 108', 108'', 108''' relative to the proximal body
102.
[0071] In this regard, FIG. 7 illustrates that the stem 100 can be
selected based on the shape and sizing of the proximal body 102 and
the angle of the humeral canal, which is accommodated with one of
the implants 100 that provides the best fitting distal angle from a
selection of multiple angles. In this regard, because in some
embodiments, the proximal body 102 need not be fitted at a single
orientation into the humerus bone 110, the proximal body 102 can be
larger and more conforming with a cortical portion 112 of the
humerus bone 110, thus providing better proximal fixation and bone
loading. Additionally, as illustrated in FIG. 7, the proximal body
102 is more conforming to the shape a cavity 118 of the humerus
110, and the stem 100 will tend to center itself during insertion,
accommodating proper placement of the stem 100 and potentially
eliminating the need for offset adjustment of a head 120 of the
stem 100.
[0072] Furthermore, the stem sizes of embodiments disclosed herein
can be based on a continuous and progressive curvature. For
example, referring to FIG. 8, a single broach 130 could be used to
prepare the cavity 118 of the humerus 110 for multiple sizes,
simply by adjusting the depth that the broach 130 is inserted. The
prior art implants referred to above currently require a different
broach for each size, and in order to determine the proper size for
use with a particular patient, one must experiment with multiple
broaches, which can make it difficult to determine whether the next
size is too large.
[0073] However, as illustrated in FIG. 8, an embodiment disclosed
herein provides for a broach 130 having a progressive curvature.
The broach 130 can be used to prepare the cavity 118 of the bone
110 for implants 100 of any size. The broach 130 can be configured
to include a depth indicator 132, which can comprise a plurality of
markings 134. Thus, as the broach 130 is inserted into the humerus
110, the surgeon can broach the cavity 118 to a desired depth, and
be aided in such broaching by the indication provided by the depth
indicator 132.
[0074] The stem implant of embodiments disclosed herein can be
variously configured depending on the intended use of the implant.
For example, FIG. 9A illustrates an embodiment of a stem implant
150 for use in a shoulder prosthesis. As shown, the implant 150 can
comprise: a distal section 152 (optional stems without the distal
section 152 can be used); a proximal section 154; a resection plane
or neck 156; and a coupling device 158.
[0075] As noted above, various configurations of the implant 150
can also be provided such that a surgeon can use a particularly
configured implant 150 that suits the shape of the humeral cavity.
Such variations in the implant 150 can be performed by altering the
angular orientation of the distal section 152 and the proximal
section 154 with respect to each other. For example, as shown in
FIG. 9A, the distal section 152 of the implant 150 can define a
longitudinal axis 160 and the proximal section 154 of the implant
150 can define a neck axis 162. In this regard, various
configurations of the implant 150 can be designed with the
longitudinal axis 160 of the distal section 152 being placed at a
discrete angle 166 with respect to the neck axis 162 of the
proximal section 154. Additional embodiments of the implant 150 can
be configured with the longitudinal axis 162 of the distal section
152 being oriented at another discrete angle 168 with respect to
the resection plane 156. However, it is contemplated that in yet
other embodiments, the angle 166 can be varied while the angle 168
remains constant, and vice versa. In contrast, prior art stems vary
the angle between the resection plane and the longitudinal axis by
simply varying the resection angle. In contrast, in the illustrate
embodiment, the angle between the resection plane and the
longitudinal axis is varied by adjusting the angle between the
distal section of the stem and the proximal section such that in
certain embodiments the entire proximal section is pivoted about a
point.
[0076] In addition, other embodiments can be configured such that
the distal section 152 is tapered. Further, the coupling device 158
can be a tapered shape or other device for attachment of the
humeral or femoral head. As used herein, the term "tapered shape"
can refer to a shape that is gradually narrower or thinner toward
one end. The shape of the proximal portion 154 of the implant 150
can curve medially to approximate the contours of the natural
proximal humerus (as noted and illustrated above with respect to
the embodiment shown in FIG. 7) and allow self-centered
broaching.
[0077] Referring now to FIG. 9B, an embodiment of a stem implant
180 for use in a hip prosthesis is shown. As shown, the hip stem
implant 180 can comprise: a distal section 182 (optional stems
without the distal section 182 can be used); a proximal section
184; a resection plane or neck 186; and a coupling device 188.
[0078] As noted above with respect to FIG. 9A, various
configurations of the implant 180 can also be provided such that a
surgeon can use a particularly configured implant 180 that suits
the shape of the humeral cavity. Such variations in the implant 180
can be performed by altering the angular orientation of the distal
section 182 and the proximal section 184 with respect to each
other. For example, as shown in FIG. 9B, the distal section 182 of
the implant 180 can define a longitudinal axis 190 and the proximal
section 184 of the implant 180 can define a neck axis 192. In this
regard, various configurations of the implant 180 can be designed
with the longitudinal axis 190 of the distal section 182 being
placed at a discrete angle 196 with respect to the neck axis 192 of
the proximal section 184. Additional embodiments of the implant 180
can be configured with the longitudinal axis 190 of the distal
section 182 being oriented at another discrete angle 198 with
respect to the resection plane 186. However, it is contemplated
that in yet other embodiments, the angle 196 can be varied while
the angle 198 remains constant, and vice versa.
[0079] In addition, other embodiments can be configured such that
the distal section 182 is tapered. Further, the coupling device 188
can be a tapered shape or other device for attachment of the
humeral or femoral head. The shape of the proximal portion 184 of
the implant 180 can curve medially to approximate the contours of
the natural proximal humerus (as noted and illustrated above with
respect to the embodiment shown in FIG. 7) and allow self-centered
broaching.
[0080] FIGS. 10A-D illustrate an embodiment of a stem implant 200
comprising proximal and distal body portions 201, 202. As described
above, and as illustrated in FIGS. 10A-D, it is contemplated that
the proximal body portion 201 can be angularly oriented with
respect to the distal body portion 202 at a plurality of angles,
thus yielding a plurality of potential configurations of the stem
implant, indicated as 200, 200', 200'', and 200'''. In accordance
with the embodiment illustrated in FIGS. 10A-D, the proximal body
portion 201 can define a head center 203 and a resection plane
204.
[0081] In some embodiments, the head center 203 can lie in the
resection plane 204, and in particular, in a central location of
the proximal body portion 201 in the resection plane 204. Further,
the distal body portion 202 can define a longitudinal axis 205 that
is oriented at an inclination angle 206 with respect to the
resection plane 204. Furthermore, the head center 203 and the
longitudinal axis 205 are spaced apart at a medial offset 207.
[0082] The medial offset 207, as shown, can be the distance between
the head center 203 of the proximal body portion 201 and a closest
point along the longitudinal axis 205. If illustrated graphically,
the medial offset 207 would be the length of a line oriented
perpendicularly to the longitudinal axis 205 and extending between
the head center 203 and the longitudinal axis 205. Therefore, in
accordance with a preferred embodiment, the stem implant 200 can be
configured such that the inclination angle 206 remains constant
while the medial offset 207 varies.
[0083] The medial offset 207 can be between approximately 4 mm and
approximately 15 mm, and is preferably between approximately 5 mm
to approximately 11 mm. In a system of stem implants 200, it is
contemplated that a plurality of implants 200, such as four, can be
provided, and that the implants can have medial offsets of
approximately mm, approximately 7 mm, approximately 9 mm, and
approximately 11 mm, respectively. Accordingly, each implant would
have a different medial offset, but all of the implants could have
the same inclination angle. Other embodiments and combinations can
be created by one of skill utilizing these teachings.
[0084] In accordance with another embodiment shown in FIGS. 11A-C,
it is contemplated that the medial offset can vary as a function of
the inclination angle. FIGS. 11A-C illustrate a system of implants
200', 200'', and 200'''. As similarly described with respect to the
embodiment shown in FIG. 10, each of the implants 200', 200'', and
200''' can include proximal and distal body portions 201', 201'',
201''' and 202', 202'', 202''', respectively, as well as medial
offsets 207', 207'', 207''' defined as the distance between head
centers 203', 203'', 203''' of the respective ones of the proximal
body portions 201', 201'', 201''' and longitudinal axes 205',
205'', 205''' of the respective ones of the distal body portions
202', 202'', 202'''.
[0085] FIGS. 11A-C illustrate an embodiment of a system of implants
200', 200'', 200''' wherein the medial offsets 207', 207'', 207'''
change as a function of inclination angle 206', 206'', 206''',
respectively. In the embodiment of FIG. 11A, the medial offset 207'
is approximately 12 mm while the inclination angle 206' is
approximately 45 degrees. In the embodiment of FIG. 11B, the medial
offset 207'' is approximately 8 mm while the inclination angle
206'' is approximately 41 degrees. Finally, in the embodiment of
FIG. 11C, the medial offset 207''' is approximately 5 mm while the
inclination angle 206''' is approximately 37 degrees. These
measurements are those of exemplary embodiments for purposes of
illustration only. It is contemplated that the medial offset can be
in the range of approximately 4 mm to approximately 15 mm, and that
the inclination angle can be in the range of approximately 30
degrees to approximately 55 degrees.
[0086] Referring now to the cross-sectional views of FIGS. 12-13,
an embodiment of a procedure will be described for preparing a
humeral cavity 210 of a humerus bone 212 and implanting the stem
into the prepared cavity 210. After the humeral head of the bone
212 is resected to define a resection surface 214, an initial or
pilot hole 216 may be drilled in the center of the resected head. A
broach 220 can then be inserted through a central area of the
resection surface 214, through the pilot hole 216, and driven into
the humerus 212 with a mallet or other impaction device. As the
broach 220 is being driven in, it is guided by a proximal area 222
of the humerus bone 212. As discussed above, the broach 220 can be
configured for use with multiple sizes, and a depth indicator 224,
such as graduations, marking, or other visual or physical devices
used on or with the broach 220. Thus, the surgeon can determine the
necessary size of the implant required for the bone, and can then
use a single broach 220 to broach the cavity 210 to the desired
depth as needed. The depth indicator 224 can illustrate the depth
or distance required to further insert the broach 220 in order to
reach a given stem implant size, as illustrated in FIG. 13.
[0087] The sizing of a proximal body 226 of the broach 220 can be
configured such that it increases in size in the proximal
direction. Such increases in size can be progressive, if desired,
depending on the geometry of the implants being used. Thus, one
broach 220 could be used to prepare the cavity 210 for an implant
of small size or of large size, depending on how much of the
proximal body 226 of the broach 220 is inserted to within the bone
212 during preparation. Because of this, a single broach 220 can be
used to prepare a cavity 210 for several sizes simply by changing
the depth of insertion. This will make it very simple for a surgeon
to determine the proper size. For example, if the broach is
inserted for a size 3, the depth indicator 224 can show the
location for a size such that the difference in insertion depth is
clearly illustrated.
[0088] It is also contemplated that during the preparation of the
cavity 210, the surgeon may trial one or many implants to determine
what size of the distal portion of the implant is necessary. If the
surgeon feels that stem stability will be sufficient without the
distal portion, he/she may opt to stop the preparation of the
cavity 210 at that point and implant a short stem. Thus, the
surgeon can exercise caution and discretion in incrementally
reaming the cavity 210 so that a stem 230 with a shorter distal
portion 232 can be used if desired, as shown in FIG. 14.
[0089] Referring now to FIG. 15, if the surgeon opts to use a stem
with a distal section, the next step is to ream the canal 210 of
the humerus 212 using a tapered or cylindrical reamer 240. The
reamer 240 is inserted into the humeral canal 210 at a base 242 of
the cavity 210 and reamed to a desired depth. Once the canal 210
has been reamed to its proper depth, a trial of the reamer 240 can
be used to determine which of the angled stems is needed, and the
stem can then be implanted.
[0090] As noted above, once the proximal section of the humeral
canal has been prepared, the humeral canal must be reamed if a stem
with a distal section is to be used. As also mentioned above, the
angle of the stem of the certain embodiments can be adjusted by
varying the angle of the distal section with respect to the
proximal body. Because of this, instead of fitting the stem to the
humeral canal and forcing a non-conforming proximal body to be
poorly placed in the humerus, a conforming proximal body can be fit
to the proximal humerus and different distal stem angles can be
used to fit the canal. In some embodiments, a set of stems can be
provided that have three discrete stem angles of approximately 35,
approximately 40, and approximately 45 degrees (as measured between
the longitudinal axis and the resection plane, discussed in FIGS.
9A-B). Alternate embodiments comprising more angles and/or a wider
range also may be used. With a five degree interval between angles,
a maximum 2.5 degree mismatch could exist between the stem distal
angle and the humeral canal; however, such a mismatch could still
allow proper placement of the stem. In some embodiments, the distal
portions of the reamer and the stem implant can be tapered to help
accommodate this difference.
[0091] Wolff's law states that when bone is repeatedly stressed, it
becomes stronger, harder, and denser. Because the outside of a
given bone typically carries the majority of the load, the bone
tends to get much stronger towards the outside. Conventional
shoulder stems do not attempt to approximate the shape of the
proximal body of the humerus. Instead, they force the broach to be
inserted into the bone at a certain position and in a certain
direction, not taking advantage of the above-mentioned strength
properties of the bone.
[0092] In contrast, as illustrated in the embodiment of FIG. 16, a
broach 250 can be configured to have a medial curve/surface 252 and
a lateral curve/surface 254 that are configured to provide the
broach 250 with a shape that facilitates proper alignment of the
stem 250 within a cavity 256 of a bone 258 such that the broach 250
can be centered within a cortical portion 260 of the bone 258.
Thus, the medial curve 252, and to a somewhat lesser extent, the
lateral curve 254, can be designed to mimic the general shape of
the proximal area of the humerus 258.
[0093] Due to the shaping of such embodiments of the broach 250,
the broach 250 will want to follow the path of least resistance,
which will be through the weakest bone at the center of the humerus
258 and not through the cortical portion 260 thereof. The final
result is that a proximal body 262 of the broach 250 can be placed
in the center of a resected surface 264 of the humerus 258
regardless of its position with respect to the humeral canal 256.
Further, it is also contemplated that proximal bodies 262 of large
sizes can be used and that they will be supported by more
structural bone than a traditional humeral stem. Since the proximal
body 262 can be placed essentially in the center of the humerus
258, little or no adjustment of the proximal portion 262 will be
required.
[0094] While the present inventions have been described with
reference to the specific embodiments, it should be understood by
those skilled in the art that various changes may be made and
equivalents may be substituted without departing from the true
spirit and scope of the inventions. In addition, many modifications
may be made to adopt a particular situation, material, composition
of matter, process, process step or steps, to the objective spirit
and scope of the present inventions. All such modifications are
intended to be within the scope of the claims appended hereto.
[0095] For example, in another embodiment, a reamer guide could be
placed into the prepared proximal cavity to eliminate any angular
mismatch between sizes instead of reaming using the canal for
guidance. Similarly, in other embodiments of the present
inventions, more angled stems could be added to reduce the
potential for mismatch.
[0096] In other embodiments, the humeral canal could be reamed and
the proximal cavity could be broached using the reamer for
guidance, instead of broaching before reaming. While this could
somewhat influence proximal stem placement, the benefit of multiple
distal angles would still vastly improve placement and fill over
current stems.
[0097] In yet other embodiments, curves that mimic the proximal
body shape could be used in areas other than the medial and lateral
curves/surfaces. They could be placed anterior and posterior or at
any number of regular intervals around the stem.
[0098] In yet another embodiment, the distal stem shape could also
have a local increase in size at its tip (such as, but not limited
to, a ball on the end of the distal section). This would help
accommodate any mismatch between the distal section and the reamed
humeral canal. The distal increase would contact the reamed cavity
and the gap after the increase would allow the distal stem center
to vary slightly from the humeral canal center.
[0099] In other embodiments, the shape of the distal section of the
stem and/or reamer can be cylindrical, elliptical, or irregularly
shaped instead of being tapered. As used herein, the term
"elliptical" can refer to a shape that resembles an elongated or
flattened circle; the term "cylindrical" can refer to a shape that
is round in cross section, and equally wide throughout its length;
and the term "irregularly shaped" can refer to a shape that does
not vary consistently in shape or size, for example, a distal
region that is substantially tapered, but has one area that has a
significantly increased size.
[0100] In other embodiments, the shape of the distal section of the
stem and/or reamer can incorporate any grooves, slots, or cutouts
for flexibility, fit, or fixation. As used herein, the term
"groove" can refer to an elongated channel in the distal region of
the stem. These grooves are typically narrow and distributed around
the distal region at close intervals, creating narrow raised ridges
between them. When inserted with slight interference with the bone,
these ridges can embed themselves within the bone, providing
mechanical locking and allowing a tight fit with some mismatch in
shape between the canal and the distal region. As used herein, the
term "slot" can refer to an elongated opening in the distal region
of the stem placed to increase the flexibility of that portion of
the stem. If a single slot is used, it can extend through the
entire thickness of the distal region of the stem, dividing it in
two. If multiple slots are used, they can intersect and end near
the central axis of the distal region of the stem, dividing the
distal region in as many sections as there are slots. As used
herein, the term "cut out" can refer to a recess in the distal
region of the stem that is meant to increase the flexibility of
that portion of the stem. These cutouts are typically on one or
more sides of distal region of the stem and are placed around the
periphery, not through the center.
[0101] In other embodiments, the entire cavity could be prepared by
broaching instead of by broaching and then reaming.
[0102] In other embodiments, the cavity could be broached first and
then reamed using a reamer that was guided by the broach or ream
first and use a broach that was guided by the reamer instead of
broaching and reaming independently.
[0103] In yet another embodiment illustrated in FIG. 17, an
instrument 300 is provide that incorporates a reaming section 302
and a broaching section 304 that are coupled together with a handle
or driving member 306. The reaming section 302 can be disposed at a
distal end of the instrument 300 and be used to ream the bone for
preparation thereof for implantation. The broaching section 304 can
incorporate a broach and be disposed intermediate the reaming
section 302 and the handle 306, such that during use, after the
reaming section 302 has reamed the cavity of the bone, the
instrument 300 can continue to be driven into the bone such that
the broaching section 304 can be used to broach a proximal portion
of the cavity. In this regard, a single tool can be used to perform
both of the broaching and reaming operations in preparation for
implantation of a stem. Further, the instrument 300 can incorporate
a joint 310 that would allow for slight angular adjustments of the
orientation of the reaming section 302 relative to the broaching
section 304.
[0104] In other embodiments, the distal region of the stem could be
angled in the anterior/posterior direction as well as the
medial/lateral direction,
[0105] In other embodiments, the neck of the stem, particularly a
hip stem, could be made modular, such that a given stem would
accept multiple necks that would be fixed to the stem using a taper
or other locking mechanism.
[0106] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower limit
unless the context clearly dictates otherwise, between the upper
and lower limit of that range and any other stated or intervening
value in that stated range is encompassed within the inventions.
The upper and lower limits of these smaller ranges which may
independently be included in the smaller ranges is also encompassed
within the inventions, subject to any specifically excluded limit
in the stated range. Where the stated range includes one or both of
the limits, ranges excluding either both of those included limits
are also included in the inventions.
[0107] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this inventions belongs.
Although any methods and materials similar or equivalent to those
described herein can also be used in the practice or testing of the
present inventions, the preferred methods and materials are now
described. All publications mentioned herein are incorporated
herein by reference to disclose and described the methods and/or
materials in connection with which the publications are cited.
[0108] It must be noted that as used herein and in the appended
claims, the singular forms "a" "and," and "the" include plural
references unless the context clearly dictates otherwise. All
technical and scientific terms used herein have the same
meaning.
[0109] The publications discussed herein are provided solely for
their disclosure prior to the filing date of the present
application. Nothing herein is to be construed as an admission that
the present inventions is not entitled to antedate such publication
by virtue of prior invention. Further, the dates of publication
provided may be different from the actual publication dates which
may need to be independently confirmed.
[0110] Although these inventions have been disclosed in the context
of certain preferred embodiments and examples, it will be
understood by those skilled in the art that the present inventions
extend beyond the specifically disclosed embodiments to other
alternative embodiments and/or uses of the inventions and obvious
modifications and equivalents thereof. In addition, while several
variations of the inventions have been shown and described in
detail, other modifications, which are within the scope of these
inventions, will be readily apparent to those of skill in the art
based upon this disclosure. It is also contemplated that various
combination or sub-combinations of the specific features and
aspects of the embodiments may be made and still fall within the
scope of the inventions. It should be understood that various
features and aspects of the disclosed embodiments can be combined
with or substituted for one another in order to form varying modes
of the disclosed inventions. Thus, it is intended that the scope of
at least some of the present inventions herein disclosed should not
be limited by the particular disclosed embodiments described
above.
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