Note: Descriptions are shown in the official language in which they were submitted.
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RESURFACING IMPLANT FOR THE WRIST AND METHOD OF
IMPLANTATION THEREOF
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention generally relates to orthopedic implants and,
more
particularly, to a resurfacing implant for the radioscaphoid joint.
Description of Related Art
[00021 Osteoarthritis (OA), also known as degenerative arthritis, is a type of
arthritis
caused by the breakdown and eventual loss of articular cartilage. Cartilage
normally serves as
a "cushion" between the bones of a joint. Loss of this cartilage cushion
causes friction
between bones, leading to pain and limitation of joint mobility. OA is the
most common form
of arthritis and affects over 20 million people in the United States. It
commonly affects the
hands as well as large weight-bearing joints, such as the hips and knees. The
most common
type of OA at the wrist joint is periscaphoid OA. This is OA between the
proximal scaphoid
and the scaphoid fossa of the radius.
[00031 Periscaphoid OA can be primary or secondary. Primary OA is usually
related to the
wear and tear associated with aging. Secondary OA is usually due either to a)
injury to the
scaphoid bone or b) injury to the scapholunate ligament which attaches the
scaphoid to the
lunate. The most common symptom of OA is pain at the affected joint. In severe
OA,
complete loss of cartilage causes friction between bones, leading to pain with
motion and at
rest. Eventually patients also lose mobility at the affected joint.
[0004] Various treatments are currently available for treating periscaphoid
OA. One option
for treatment is surgery to repair the wrist joint. Such surgical treatments
are generally
reserved for those patients with OA that are particularly severe and
unresponsive to
conservative treatments. The two most common surgical treatments for
periscaphoid OA are
4-corner fusion (4-CF) and proximal row carpectomy (PRC). Unfortunately both
of these
procedures lead to loss of wrist motion. Another surgical option is a total
wrist fusion.
However, a total wrist fusion leads to a complete loss of wrist motion.
[00051 Alternative treatment options include wrist arthroplasty or joint
replacement.
However, current wrist arthroplasty technology has significant limitations.
Current total joint
replacement implants for the wrist require removing large sections of bone and
soft tissues
due to the large size of the implants. Current implants also require bone
purchase or bone
cement for stability. Further, implantation of current wrist implants requires
making large
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incisions in the patient to provide the surgeon with the access required to
ensure proper
alignment of the implants.
[0006] Consequently, patients can experience long operating room times,
lengthy recovery,
and reduced mobility. Revision surgeries are challenging because substantial
bone has been
removed, and there may not be a salvage procedure other than fusion of the
joint. Partial wrist
replacements are available; however, such techniques still require bone
removal and lead to
soft tissue damage during surgery, leading to joint instability and few
revision options.
[0007] Accordingly, attempts have been made to develop devices to resurface
the distal
radius of the wrist. For instance, United States Patent Application
Publication No.
2007/0185582 to Palmer et al. discloses a radial implant (100A) for the radius
(1) of the
wrist. The radial implant (100A) has tapered edges to prevent sharp contact
with soft tissue
and an articulating surface (102A). The articulating surface (102A) has at
least one generally
concave surface facing the joint space (5), and can have one or more points of
concavity
generally shaped and oriented to match the scaphoid bone (2) and the lunate
bone (3). The
radial implant (100A) also includes a static surface (101A) configured to
contact the
cartilage, bone, or tissue of the radius (1), and is shaped to generally fit
within the radius (1).
A stabilizing fin (150A) may also be provided, and can be a fixed component of
the radial
implant (100A) or a separate attachment connected during assembly of the
implant (100A).
However, such resurfacing implants still suffer from various deficiencies.
Since these
resurfacing implants are provided as a single integral piece, a relatively
large incision still
needs to be made for implantation. In addition, such implants also require the
resurfacing of
the entire distal radius, even if a portion of the distal radius is still
healthy.
[0008] Accordingly, a need exists for a resurfacing implant for treatment of
periscaphoid
OA that is provided in two or more modular components. In addition, a further
need exists for
a resurfacing implant for the wrist that would resurface the scaphoid fossa of
the radius while
leaving the Innate fossa of the radius, the distal radioulnar joint, and the
ulnocarpal joint
intact.
SUMMARY OF THE INVENTION
[0009] An object of the present invention is to provide a resurfacing implant
for treatment
of periscaphoid OA that is provided in two or more modular components. An
additional
object of the present invention is to provide a resurfacing implant for the
wrist that would
resurface the scaphoid fossa of the radius while leaving the lunate fossa of
the radius, the
distal radioulnar joint, and the ulnocarpal joint intact.
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[0010] Accordingly, provided is a modular resurfacing implant for a
radioscaphoid joint of
a wrist. The implant includes a stem and an articular component coupled to the
stem. The
stem includes a threaded body for implantation into a distal radius and a
connection member
positioned at a second end of the stem. The articular component includes a
body member
configured to resurface a scaphoid fossa of the distal radius. The body member
includes a
concave top surface matching a curvature of the scaphoid fossa and a bottom
surface having a
post extending therefrom that is configured to mate with the connection member
of the stem.
The articular component is configured to resurface the scaphoid fossa while
leaving a lunate
fossa of the distal radius intact.
[00111 The articular component may be positioned such that it forms a smooth
surface with
the lunate fossa. The top surface of the articular component may be
manufactured from a
cobalt chrome alloy. The bottom surface of the articular component may be
manufactured
from titanium.
[0012] The connection member of the stem may include a hole configured to mate
with the
post of the articular component, thereby fixedly coupling the articular
component to the stem.
The stem may be cannulated. The threaded body of the stem may taper from the
second end
to a first end. The stem may be manufactured from titanium.
[0013] Also provided is a resurfacing implant for a radioscaphoid joint of a
wrist. The
implant includes a stem having an elongated body with a first end and a second
end; and an
articular component having a body member extending from the second end of the
elongated
body of the stem. The elongated body is configured to be implanted into a
distal radius of the
wrist such that the articular component resurfaces the scaphoid fossa while
leaving a lunate
fossa of the distal radius intact.
[0014] The stem and the articular component may be integrally formed or
removably
coupled. The elongated body of the stem may be implanted into the distal
radius by press
fitting the elongated body into an opening formed in the distal radius.
Alternatively, the
elongated body of the stem may be threaded such that it is threadedly coupled
to the distal
radius.
[0015] The articular component may be positioned such that it forms a smooth
surface with
the lunate fossa. The articular component may include a concave top surface
matching a
curvature of the scaphoid fossa and a bottom surface. The top surface may be
manufactured
from a cobalt chrome alloy. The bottom surface may be manufactured from
titanium. The
stem may be cannulated. The elongated body of the stem may taper from the
second end to
the first end.
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[0016] In addition, provided is a method of resurfacing a radioscaphoid joint
of a wrist.
The method includes providing a resurfacing implant. The resurfacing implant
includes a
stem having an elongated body with a first end and a second end; and an
articular component
having a body member configured to be coupled to the second end of the
elongated body of
the stem. The method also includes the steps of making a longitudinal midline
wrist incision;
implanting the stem in a distal radius of the wrist; removing a diseased
portion of bone at a
scaphoid fossa of the distal radius; and coupling the articular component to
the second end of
the elongated body of the stem such that the articular component resurfaces
the scaphoid
fossa while leaving a lunate fossa of the distal radius intact.
[0017] These and other features and characteristics of the present invention,
as well as the
methods of operation and functions of the related elements of structures and
the combination
of parts and economies of manufacture, will become more apparent upon
consideration of the
following description and the appended claims with reference to the
accompanying drawings,
all of which form a part of this specification, wherein like reference
numerals designate
corresponding parts in the various figures. It is to be expressly understood,
however, that the
drawings are for the purpose of illustration and description only and are not
intended as a
definition of the limits of the invention. As used in the specification and
the claims, the
singular form of "a", "an", and "the" include plural referents unless the
context clearly
dictates otherwise.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 illustrates bones of a typical human wrist;
[0019] FIG. 2 is a front plan view of a modular resurfacing implant in
accordance with one
embodiment of the present invention;
[0020] FIG. 3 is an exploded view of the modular resurfacing implant of FIG.
2;
[0021] FIG. 4 is a bottom plan view of an articular component of the modular
resurfacing
implant of FIG. 2;
[0022] FIG. 5 is a top plan view of a stem of the modular resurfacing implant
of FIG. 2;
[0023] FIG. 6 is a front view of the bones of a typical human wrist with the
modular
resurfacing implant of FIG. 2 implanted therein;
[0024] FIG. 7 is a top plan view of the radius of a typical human wrist with
the modular
resurfacing implant of FIG. 2 implanted therein;
[0025] FIG. 8 is a cross-sectional view of the human wrist with the modular
resurfacing
implant implanted therein of FIG. 7 taken along line 8--8;
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[0026] FIG. 9 is a top plan view of an alternative embodiment of the articular
component
of the modular resurfacing implant in accordance with the present invention;
[0027] FIG. 10 is a cross-sectional view of the articular component of FIG. 9
taken along
line b0-40;
[0028] FIG. 11 is side view of another embodiment of the modular resurfacing
implant in
accordance with the present invention;
[0029] FIG. 12 is a front view of the modular resurfacing implant of FIG. 11;
and
[0030] FIG. 13 is a side view of still another embodiment of the modular
resurfacing
implant in accordance with the present invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0031] For purposes of the description hereinafter, the terms "upper",
"lower", "right",
"left", "vertical", "horizontal", "top", "bottom", "lateral", "longitudinal",
and derivatives
thereof shall relate to the invention as it is oriented in the drawing
figures. However, it is to
be understood that the invention may assume alternative variations and step
sequences,
except where expressly specified to the contrary. It is also to be understood
that the specific
devices and processes illustrated in the attached drawings, and described in
the following
specification, are simply exemplary embodiments of the invention. Hence,
specific
dimensions and other physical characteristics related to the embodiments
disclosed herein are
not to be considered as limiting.
[0032] FIG. 1 illustrates the primary bones of a human forearm and wrist. The
bones of the
forearm include a radius 1 and an ulna 3. The radius 1 includes a distal end
or distal radius 5
that includes two concavities: the scaphoid fossa 7 and the lunate fossa 9.
The scaphoid fossa
7 articulates against a scaphoid bone 11. The radioscaphoid joint 12 is formed
where the
distal radius 5 articulates with the scaphoid bone 11. The lunate fossa 9
articulates against a
lunate bone 13.
[0033] With reference to FIGS. 2-5, the present invention is directed to a
modular
unicompartmental resurfacing hemiarthroplasty system for treatment of
periscarphoid OA.
The system of the present invention is intended to replace the worn cartilage
surface at the
scaphoid fossa 7 of the radius 1. Accordingly, the system of the present
invention desirably
includes: 1) a resurfacing or articular component specific to the scaphoid
fossa of the radius;
2) modularity between the articular component and a stem of the implant; and
3) a stem with
a screw-fit design.
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[00341 A modular resurfacing implant 15 for a radioscaphoid joint of a wrist
in accordance
with one embodiment of the present invention includes a stem 17 and an
articular component
19 coupled to stem 17. Stem 17 includes a body 21 for implantation into
scaphoid fossa 7
region of distal radius 5. Body 21 includes a first end 23 and a second end
25. Desirably,
body 21 tapers from second end 25 to first end 23. A connection member 27 is
positioned at
second end 25 of stem 17.
[0035] In addition, body 21 desirably includes a plurality of threads 29.
Currently, most
wrist implants are manufactured to have stems with a press-fit design. A press-
fit design
requires the implant stem to sit in the center of a medullary canal of radius
1. Accordingly,
press-fit stems lead to increased trauma at the medullary canal of radius 1
and increased
difficulty with implant removal. In addition, the placement of subsequent
implants is difficult
because the subsequent implant would require a longer stem. The advantage of
providing
body 21 of implant 15 of the present invention is that screwing body 21 into
the appropriate
position leads to minimal damage to the medullary canal in comparison with
press-fit stems.
Furthermore, replacement of implant 15 with a total wrist implant would be
much simpler in
patients who have previously had an implant with stem 17 having body 21 with a
plurality of
threads 29.
[0036] Stem 17 is provided in a variety of widths and lengths, thereby
allowing surgeons to
accommodate the various types of patient bone size and density. Desirably,
stem 17 is
manufactured from titanium with a roughened surface to encourage
osseointegration. Finally,
stem 17 is cannulated to allow the surgeon to pass stem 17 over previously
placed guide wire,
such as a Kirshner wire. This allows the surgeon to check and optimize the
placement of the
Kirshner wire. Once the position of the Kirshner wire is confirmed, stem 17
can be positioned
in scaphoid fossa 7 of distal radius 5 using the Kirshner wire as a guide.
[0037] Articular component 19 includes a body member 31 configured to
resurface
scaphoid fossa 7 of distal radius 5. Body member 31 includes a generally
concave top surface
33 matching a curvature of scaphoid fossa 7 and a bottom surface 35 having a
post 37
extending therefrom that is configured to mate with a hole 39 provided in
connection member
27 of body 21 of stem 17. Accordingly, articular component 19 is fixedly
coupled to stem 17
when post 37 is frictionally fit within hole 39 by a Morse Taper-Cold Weld
fit. In operation,
as will be described in greater detail hereinafter, stem 17 is implanted into
a patient's distal
radius 5 and, thereafter, articular component 19 is connected thereto as
described
hereinabove. There are numerous advantages of such an implant 15 having such a
modular
design. For instance, the sizes of stem 17 and articular component 19 can be
independently
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adjusted according to the patient's unique anatomy and size. In addition, a
modular design
allows the surgeon to implant the device with less trauma and disruption to
the wrist
ligaments. The smaller modular components can be inserted with a smaller
exposure than
large single component implants. By using a smaller exposure, fewer wrist
ligaments are
disrupted, which leads to a shorter recovery and a more stable wrist.
[0038] Body member 31 of articular component 19 is sized and shaped to replace
only the
damaged scaphoid fossa 7 while leaving a lunate fossa 9 of distal radius 5,
the distal
radioulnar joint, and the ulnocarpal joint intact. Body member 31 may be
circular, elliptical
(as shown in FIG. 7) or any other suitable shape to replace scaphoid fossa 7.
Accordingly,
minimal cartilage and bone needs to be removed from the surface of distal
radius 5.
Therefore, implant 15 is desirably used for the treatment of periscaphoid OA.
As described
hereinabove, periscaphoid OA is a specific type of arthritis which affects
scaphoid fossa 7,
but not lunate fossa 9 of distal radius 5. Standard surgical treatment for
periscaphoid OA
requires an intact lunate fossa 9 at distal radius 5 in order for the surgical
treatment to be
succesful. Currently available implants replace both the scaphoid fossa 7 and
lunate fossa 9
of distal radius 5. As a result, these implants do not allow for patients to
undergo standard
surgical treatments for periscaphoid OA if the implant should fail. In
addition, the
implantation of currently available implants requires removal of significantly
more bone,
cartilage, and ligaments than the implantation of implant 15. As a result,
patients with failed
implants often cannot undergo a second implant surgery. If patients have a
problem with the
implant, their main option becomes a total wrist fusion. Unfortunately, the
current implants
also make total wrist fusion more difficult to achieve because of the large
amount of bone
that is removed.
[0039] Implant 15 of the present invention is designed to leave lunate fossa 9
of distal
radius 5 intact. This allows patients to undergo standard periscaphoid
surgical treatment at a
later date if the patient rejects the implant or if the implant fails.
Furthermore, implant 15 is
designed to only resurface scaphoid fossa 7. Unlike currently available
implants that remove
a thick portion of bone from distal radius 5, implant 15 only requires the
removal of a small
portion of cartilage/bone from distal radius 5. This advantageously allows a
patient to
undergo treatment at a later time with a standard implant or complete wrist
fusion if implant
15 is unsuccessful in treating the periscaphoid OA. Finally, the ligaments of
the wrist are
maintained during the implantation of implant 15 providing patients with
improved stability
in the wrist.
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[0040] A standard articular component 19 has a height of approximately 13 mm
and a
width of approximately 15 mm. However, this is not to be construed as limiting
the present
invention, as the articular component 19 is envisioned as being available in a
variety of sizes
(i.e., heights and widths) to match the needs of various patients. Top surface
33 of articular
component 19 is desirably surfaced with a soft metal, such as a cobalt chrome
alloy. Bottom
surface 35 of articular component 19 may be manufactured from titanium with a
roughened
surface to encourage osseointegration.
[0041] With reference to FIGS. 6-8 and with continued reference to FIGS. 1-5,
the
procedure for implanting implant 15 is as follows. First, a single
longitudinal midline wrist
incision is made down to the level of the extensor retinaculum. The third and
second extensor
compartments are opened and their tendons are retracted radially. The fourth
compartment is
opened and its tendons are retracted ulnarly. The posterior interosseous nerve
is identified
and resected. Either a T-incision of the capsule or ulnar based capsular flap
is then made.
[0042] Thereafter, the articular surfaces of scaphoid 11 and scaphoid fossa 7
are examined
to assess for OA. A flexible guide wire, such as a Kirshner wire, is placed
into distal radius 5.
A guide is used to ensure the wire passes through radius I parallel to a shaft
of radius 1. The
guide also assists to ensure the entry point is at the center of scaphoid
fossa 7. Stem 17 is then
placed over the Kirshner wire such that the Kirshner wire enters through first
end 23 of body
21 of stem 17 and passes out of hole 39 at second end 25 of stem 17. Stem 17
is thereby
guided to the correct position in scaphoid fossa 7 for implantation and then
fixated therein by
threads 29. Once stem 17 is fixated into radius 1, a reamer is placed over the
Kirshner wire.
The reamer is used to remove a portion of the articular surface of scaphoid
fossa 7 and
freshen the bone at scaphoid fossa 7. This portion corresponds to the size and
site of articular
component 19 of implant 15. The Kirshner wire is then removed and articular
component 19
is placed. Articular component 19 is fixedly coupled to stem 17 by inserting
post 37 into hole
39 of connection member 27 to form a Morse Taper-Cold Weld fit.
[0043] Next, the surgeon must check to ensure top surface 33 of articular
component 19 is
not proud. In other words, the surgeon must check to ensure that top surface
33 of articular
component 19 forms a smooth surface with lunate fossa 9 as shown in FIG. 8. If
top surface
33 of articular component 19 is proud, articular component 19 is removed and
distal radius 5
is further reamed.
[0044] Finally, the surgical area is flushed with irrigation solution,
hemostasis is achieved,
the dorsal ligaments and capsule are repaired, and the skin is closed. The
patient is then
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placed in a volar slap for approximately one to two weeks. Physical therapy is
also started to
maintain range of motion at the wrist joint.
[00451 With reference to FIGS. 9 and 10, an alternative embodiment of
articular
component 41 is illustrated. Articular component 41 includes a body 43 having
a top surface
45 and a bottom surface 47. Bottom surface 47 has a post 49 extending
therefrom that is
configured to mate with hole 39 provided in connection member 27 of body 21 of
stem 17.
Top surface 45 of articular component 41 is desirably surfaced with a soft
metal, such as a
cobalt chrome alloy. Bottom surface 47 of articular component 41 may be
manufactured from
titanium with a roughened surface to encourage osseointegration.
[00461 Articular component 41 has generally the same size and shape as
articular
component 19. However, articular component 41 further includes a dorsal
extension 51.
Accordingly, articular component 41 is provided to treat patients having a
scapholunate
ligament injury. Patients with scapholunate ligament injury commonly develop
flexion of the
scaphoid. This eventually leads to a form of arthritis known as scapholunate
advanced
collapse (SLAG}. Dorsal extension 51 is provided to control scaphoid flexion.
More
specifically, dorsal extension 51 includes a gradual curve to control the
tendency of scaphoid
11 to flex.
[0047] While the present invention has been described hereinabove as including
a threaded
stem 17 to provide a screw-fit within radius 1, this is not to be construed as
limiting the
present invention, as a stem having a press-fit design may also be utilized.
With reference to
FIGS. 11 and 12, an alternative embodiment of a stem 53 having a press-fit
design is
illustrated. Stem 53 has an elongated body 55 having a first end 57 and a
second end 59.
Second end 59 includes a hole 61 for receiving post 37 of articular component
19 or post 49
of articular component 41.
[00481 Stem 53 may be provided in a variety of widths and lengths, thereby
allowing
surgeons to accommodate the various types of patient bone size and density.
Desirably, stem.
53 is manufactured from titanium with a roughened surface to encourage
osseointegration.
Finally, stem 53 may be cannulated to allow the surgeon to pass stem 53 over a
previously
placed guide wire, such as a Kirshner wire. This allows the surgeon to check
and optimize the
placement of the Kirshner wire. Once the position of the Kirshner wire is
confirmed and the
site within radius I has been prepared by the'surgeon, stem 53 can be
positioned in scaphoid
fossa 7 of distal radius 5 and press-fit within radius 1 using the Kirshner
wire as a guide.
Thereafter, distal radius 5 is prepared and articular component 19 or 41 is
coupled to second
end 59 of stem 53 as discussed hereinabove.
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[0049] While implant 15 has been discussed hereinabove as including modular
articular
and stem components, this is also not to be construed as limiting the present
invention as the
articular components and stem components may be provided integrally. In
addition, and with
reference to FIG. 13, a resurfacing implant 63 may be provided that includes
an integrally
formed stem 65 and articular component 67. Stem 65 is configured to be press-
fit into radius
1 and articular component 67 is configured to resurface scaphoid fossa 7 of
distal radius 5
while leaving lunate fossa 9 intact. Stem 65 and articular component 67 may be
manufactured
from titanium having a roughened surface.
[0050] Articular component 67 is sized and shaped generally the same as
articular
component 19. However, articular component 67 further includes a tray 69
configured to
receive a resurfacing component 71. Resurfacing component 71 is configured to
be provided
in variable thicknesses to suit a specific patient's needs. Resurfacing
component 71 is
desirably manufactured from a soft metal, such as a cobalt chrome alloy.
[0051] Accordingly, the present invention described hereinabove provides a
resurfacing
implant for treatment of periscaphoid OA that is provided in two or more
modular
components that resurfaces the scaphoid fossa of the radius while leaving the
lunate fossa of
the radius, the distal radioulnar joint, and the ulnocarpal joint intact.
[0052] The unicompartmental resurfacing hemiarthroplasty system is
beneficially provided
for patients with symptomatic periscaphoid OA. Ideal candidates would have OA
limited to
the scaphoid fossa of the radius. This would include patients with grades 1-2
SLAC or
scaphoid non-union advanced collapse (SNAG). However, this is not to be
construed as
limiting the present invention as the use of a resurfacing implant to
resurface only a portion
of a joint has also been envisioned. For instance, if the lunate fossa were
diseased, an implant
could be developed that only replaced the surface of the lunate fossa while
leaving the
scaphoid fossa intact.
[0053] Although the invention has been described in detail for the purpose of
illustration
based on what is currently considered to be the most practical and preferred
embodiments, it
is to be understood that such detail is solely for that purpose and that the
invention is not
limited to the disclosed embodiments, but, on the contrary, is intended to
cover modifications
and equivalent arrangements. For example, it is to be understood that the
present invention
contemplates that, to the extent possible, one or more features of any
embodiment can be
combined with one or more features of any other embodiment.
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