U.S. patent application number 12/109511 was filed with the patent office on 2008-10-30 for carpometacarpal (cmc) joint arthoplasty implants and related jigs, medical kits and methods.
This patent application is currently assigned to Piper Medical, Inc.. Invention is credited to Mark J. Warburton.
Application Number | 20080269908 12/109511 |
Document ID | / |
Family ID | 39887944 |
Filed Date | 2008-10-30 |
United States Patent
Application |
20080269908 |
Kind Code |
A1 |
Warburton; Mark J. |
October 30, 2008 |
CARPOMETACARPAL (CMC) JOINT ARTHOPLASTY IMPLANTS AND RELATED JIGS,
MEDICAL KITS AND METHODS
Abstract
Thumb carpometacarpal (CMC) joint implants include a trapezium
implant defining an articulating surface and a cooperating first
metacarpal implant with a base portion of the first metacarpal
defining an articulating surface. The first metacarpal base
articulating-surface is configured to articulate against the
trapezium implant articulating surface.
Inventors: |
Warburton; Mark J.; (High
Point, NC) |
Correspondence
Address: |
MYERS BIGEL SIBLEY & SAJOVEC
PO BOX 37428
RALEIGH
NC
27627
US
|
Assignee: |
Piper Medical, Inc.
|
Family ID: |
39887944 |
Appl. No.: |
12/109511 |
Filed: |
April 25, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60914449 |
Apr 27, 2007 |
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Current U.S.
Class: |
623/21.15 |
Current CPC
Class: |
A61F 2002/30387
20130101; A61B 17/1782 20161101; A61F 2002/4635 20130101; A61F
2002/30113 20130101; A61B 17/1686 20130101; A61F 2002/30604
20130101; A61F 2002/30164 20130101; A61F 2/4684 20130101; A61F
2002/4258 20130101; A61F 2002/30156 20130101; A61F 2/4241 20130101;
A61F 2002/30616 20130101; A61F 2002/30431 20130101; A61F 2002/30265
20130101; A61F 2002/30672 20130101; A61F 2/4606 20130101; A61F
2002/30161 20130101; A61B 17/15 20130101; A61F 2002/30301 20130101;
A61F 2002/30403 20130101; A61F 2002/4256 20130101 |
Class at
Publication: |
623/21.15 |
International
Class: |
A61F 2/42 20060101
A61F002/42 |
Claims
1. A thumb Carpo-MetaCarpal (CMC) joint implant, comprising: a
trapezium implant defining an articulating surface; and a
cooperating first metacarpal implant with a base portion of the
first metacarpal defining an articulating surface, wherein the
first metacarpal base is configured to articulate against the
trapezium implant articulating surface.
2. An implant according to claim 1, wherein the trapezium implant
comprises at least one substantially rigid downwardly extending
anchoring member configured to reside in a channel formed in a
target trapezium.
3. An implant according to claim 2, wherein the at least one
anchoring member is a plurality of transversely spaced apart keels
extending at least a major portion of a length or width dimension
of the trapezium implant.
4. An implant according to claim 3, wherein the trapezium keels are
sized to extend only a portion of the length or width of the
trapezium implant, and wherein the keels extend transversely or
longitudinally closer to one outer perimeter surface than the
opposing outer perimeter surface.
5. An implant according to claim 1, wherein the trapezium implant
comprises a projecting portion that forms the articular surface,
and wherein the first metacarpal base portion has a recessed cavity
that matably receives the projecting portion of the trapezium
implant, thereby allowing articulating motion between the trapezium
implant and the first metacarpal base.
6. An implant according to claim 1, wherein the trapezium implant
is a unitary rigid body.
7. An implant according to claim 1, wherein the trapezium implant
and the first metacarpal implant define a total thumb CMC joint
replacement.
8. An implant according to claim 1, wherein the trapezium implant
has a projecting portion that extends outside the bounds of the
trapezium into the CMC cavity to define a substantially convex
articular surface, and wherein the first metacarpal implant base
portion has a socket with a substantially concave cavity sized and
configured to matably receive the projecting portion of the
trapezium implant.
9. An implant according to claim 1, wherein the first metacarpal
implant base portion has a projecting portion that extends outside
the bounds of the first metacarpal into the CMC cavity to define a
substantially convex articular surface, and wherein the trapezium
implant has a socket with a substantially concave cavity sized and
configured to matably receive the projecting portion of the
metacarpal base portion.
10. An implant according to claim 1, wherein the first metacarpal
implant comprises an elongate intramedullary body that is
attachable to the base portion.
11. An implant according to claim 1, wherein the base portion has a
locking member that is matably attachable to the elongate
intramedullary body.
12. An implant according to claim 1, wherein the first metacarpal
implant has an elongate intramedullary body that merges into the
base portion, wherein the elongate body is rigid, and wherein the
articular surface of the base portion material comprises a
polymer.
13. An implant according to claim 12, wherein the base portion has
a thickness defined to substantially fill a target articulating
cavity of the CMC joint.
14. An implant according to claim 1, wherein the trapezium implant
has at least one anchoring member with a substantially planar
downwardly extending body merging into a lower portion that is
substantially circular in cross-section
15. A medical kit for thumb CMC joint arthroplasty, comprising: at
least one thumb trapezium implant; and at least one thumb first
metacarpal intramedullary stem implant; whereby, in position, the
thumb first metacarpal intramedullary implant and the trapezium
implant articulate against each other.
16. A kit according to claim 15, further comprising: a plurality of
base members having different sizes and/or shapes, each of the base
members configured to serially attach to the first metacarpal
intramedullary stem implant, whereby, in position, the attached
base member of the intramedullary implant and the trapezium implant
articulate against each other.
17. A medical kit according to claim 15, wherein the at least one
trapezium implant comprises at least one downwardly extending
anchoring member configured to reside in local bone of a target
trapezium.
18. A medical kit according to claim 16, further comprising a
plurality of trial trapezium implants, wherein the trials have a
substantially planar bottom surface devoid of any downwardly
projecting anchoring member or the trials have at least one
downwardly extending anti-rotational post.
19. A medical kit according to claim 15, further comprising at
least one trapezium implant jig configured to define a bone
preparation guide or template for preparing a target trapezium to
accept the trapezium implant.
20. A medical kit according to claim 15, wherein the trapezium
implant jig comprises at least one downwardly extending slot, and a
plurality of holding apertures.
21. A medical kit according to claim 20, wherein the at least one
downwardly extending slot merges into a keyhole on a medial to
lower portion of the jig.
22. A medical kit according to claim 20, wherein the jig comprises
a top portion that merges into a downwardly extending side portion,
with the side portion being substantially orthogonal to the top
portion, and wherein the jig at least one downwardly extending slot
is configured to continuously extend from the downwardly extending
portion upward and across the top portion to define a substantially
horizontal slot extending through a top surface of the jig thereby
providing a cutting guide to allow a cutting member to form a
channel in local bone of the trapezium that receives the anchoring
member.
23. A medical kit according to claim 15, further comprising at
least one first metacarpal bone broach sized and configured to
enter an intramedullary canal of a target first metacarpal bone to
size and/or prepare the bone for the first metacarpal stem
implant.
24. A medical kit according to claim 15, wherein the at least one
trapezium implant has a projecting portion that extends outside the
bounds of the trapezium into a CMC cavity to define a substantially
convex articular surface, and wherein the first metacarpal implant
has a socket with a substantially concave cavity sized and
configured to matably receive the projecting portion of a
corresponding trapezium implant.
25. A medical kit according to claim 15, wherein the trapezium
implant has at least one anchoring member with a substantially
planar downwardly extending body merging into a lower portion with
a larger shape in an end view thereof.
26. A jig for a thumb arthroplasty procedure, comprising: a rigid
body having a substantially planar top segment that merges into a
substantially planar downwardly extending side segment; and at
least one slot extending across at least a portion of the top
segment and down into at least a portion of the side segment,
whereby the slot is sized and configured to define a cutting guide
for a target trapezium.
27. A jig according to claim 26, wherein the slot is substantially
straight and substantially horizontal across the top segment and
substantially vertical along the side segment.
28. A method for treating and/or repairing a thumb in a patient,
comprising: implanting a trapezium implant so that the trapezium
implant defines surface of a joint in a patient; and implanting a
first metacarpal implant into the first metacarpal so that the
first metacarpal implant defines surface of the joint in the
patient whereby the first metacarpal implant articulates against
the trapezium implant.
29. A method according to claim 28, further comprising before the
step of implanting the trapezium implant: preparing the target
trapezium for receiving the trapezium implant by planarizing the
natural articular surface of the target trapezium, then forming a
channel in the target trapezium; and trying different size
trapezium trials to determine a proper size trapezium implant for
the patient.
30. A method according to claim 28, further comprising, before the
step of implanting the trapezium implant, temporarily affixing a
jig with at least one drilling and cutting channel guide to the
trapezium, and drilling and cutting at least one channel into the
target trapezium using the jig drilling and cutting channel
guide.
31. A method according to claim 28, wherein the first metacarpal
implant comprises an elongate intramedullary stem and an attachable
base member with a socket, the method further comprising, before
the step of implanting the first metacarpal implant; trying
different size base members to select a base member that
substantially fills the CMC cavity.
32. A method according to claim 31, further comprising attaching
the selected base member to the metacarpal stem.
33. A method according to claim 28, wherein the trapezium implant
has at least one anchoring member with a substantially planar
downwardly extending body merging into a lower portion that has a
larger cross-sectional configuration that the substantially planar
body.
34. A method according to claim 33, wherein the lower portion has a
substantially circular cross-section.
35. A thumb arthroplasty implant, comprising: a first implant
member having an upper surface; and a cooperating second implant
member with a base portion defining a lower surface thereof,
wherein the first implant upper surface faces the second implant
lower surface, and wherein the first implant member is configured
to articulate with respect to the second implant member.
36. An implant according to claim 35 wherein the first implant
member comprises at least one substantially rigid downwardly
extending anchoring member configured to reside in a channel formed
in a target bone of the hand.
37. An implant according to claim 36, wherein the at least one
anchoring member is a plurality of transversely spaced apart keels
extending at least a major portion of a length or width dimension
of the first implant member.
38. An implant according to claim 35, wherein the second implant
member has an elongate intramedullary body for placement in the
first metacarpal of a thumb, wherein the base portion is matably
attachable to the second implant member, wherein the elongate body
is rigid, and wherein the lower surface of the base portion
comprises a polymer.
39. An implant according to claim 35, wherein the first implant
member has at least one anchoring keel member with a substantially
planar downwardly extending body merging into a lower portion that
is substantially circular in cross-section.
40. An implant according to claim 35, wherein at least one of the
first implant member or the base portion of the second implant
member is provided in a plurality of different sizes.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of priority of U.S.
Provisional Application Ser. No. 60/914,449 filed Apr. 27, 2007,
the contents of which are hereby incorporated by reference as if
recited in full herein.
FIELD OF THE INVENTION
[0002] This invention relates to implants suitable for use in
treating pain and/or injury of the carpometacarpal joint.
BACKGROUND OF THE INVENTION
[0003] Basilar thumb arthritis (arthritis at the base of the thumb)
of the carpo-metacarpal (CMC) joint is thought to be the most
common arthritis of the homosapien. It typically presents as a
symptomatic problem in the sixth decade of life and its incidence
increases thereafter. It is a result of the rather recent
phylogenetic appearance of a highly mobile, strong thumb ray. The
thumb acts as the pivotal and guiding member of the defining
anatomical features of the human, the prehensile hand. The brain's
cortical representation area of the thumb is huge. The thumb allows
for a panoply of activities from watch making to weightlifting.
Unfortunately, this distinct anatomical advantage can result in
arthritis of the CMC joint of the thumb.
[0004] It is believed that gaming and cell phone text-messaging and
the like may also lead to basilar thumb arthritis, with a resulting
increase in incidence as well as a potential earlier onset that has
been conventional.
[0005] Anatomically, the CMC joint includes the trapezium
articulating with the base of the first metacarpal as shown in FIG.
1. As shown in FIG. 2, the CMC joint is a saddle joint allowing
abduction toward the palm, abduction away from the palm, opposition
(toward the 5.sup.th finger), and extension or retroposition
(backward or hitch-hiker position.) As shown in FIG. 3B, the
articular surface of the base of the 1.sup.st metacarpal 20 is
divided into dorsal and palmer slopes and a central saddle portion.
As shown in FIG. 3A, the opposing articular surface of the
trapezium 10 also has two parts: a spherical portion 11, which
articulates with the slopes of the first metacarpal; and a saddle
portion 12, which articulates with the saddle portion of the
1.sup.st metacarpal. (See, e.g., Zancolli et al., Biomechanics of
the trapezio-metacarpal joint, Clinical Orthopaedics and Related
Research, No. 220, July 1987, pp. 14-26). FIG. 3C illustrates an
enlarged "normal" or "natural" trapezium 10 and first metacarpal
base 20b.
[0006] The subchondral (below cartilage) bone of the
trapezium-first metacarpal is covered by hyaline cartilage. This
cartilage is typically the first tissue to deteriorate during
arthritic wear of the joint. Initially, thinning and pitting
occurs, which can be followed by osteophyte (bone spur) formation
and subluxation (loss of congruity) of the joint.
[0007] Over the past fifty years various arthroplasties have been
proposed to try to alleviate the disabling pain of CMC arthritis.
Generally stated, the arthroplasties have been either soft tissue
interpositions, implant interpositions, or partial joint
replacements using implants. The implant procedures either have
replaced the base of the first metacarpal or replaced the trapezium
following trapezectomy.
[0008] Currently, 1.sup.st metacarpal implants involve inserting an
intramedullary stem into the base of the 1.sup.st metacarpal, to
which is attached a convex articular surface replacement. Trapezial
implants generally have the shape of the anatomic trapezium. In
both cases, an implant material (e.g., metal, silicone, or ceramic)
articulates with a bone surface where motion occurs. These
procedures do not attempt to replace the joint but rather act as
spacers. Fortunately, they can reduce the arthritic pain, but
problems have arisen. Potential problems include implant loosening,
implant breakage, implant dislocation, adverse tissue reaction to
the implant (particularly silicone), failure of pain relief, loss
of strength, and implant subsidence (sinking in or erosion of the
residual trapezium, as in 1.sup.st metacarpal implants). It is
believed that because of these problems, the most common procedure
currently performed for CMC arthritis is a soft tissue
interposition suspension procedure also known as "ligament
reconstruction with tendon interposition (LRTI)" where no implant
is used.
[0009] In view of the foregoing, there remains a need for
alternative thumb CMC implants.
SUMMARY OF EMBODIMENTS OF THE INVENTION
[0010] In some embodiments, thumb CMC joint implants include a
trapezium implant defining an articulating surface and a
cooperating first metacarpal implant with a base portion of the
first metacarpal defining an articulating surface. The first
metacarpal base articulating-surface is configured to articulate
against the trapezium implant articulating surface.
[0011] Embodiments of the present invention can replace both the
base of the first metacarpal and the opposing articular surface of
the trapezium, resulting in a total thumb CMC arthroplasty
(TCMA).
[0012] In some embodiments, the trapezium implant includes at least
one downwardly extending anchoring member. The at least one
anchoring member can include a plurality of transversely spaced
apart keels extending at least a major portion of a length or width
dimension of the trapezium implant.
[0013] In some embodiments, the trapezium implant can include a
projecting portion that forms the articular surface. The first
metacarpal base portion can include a recessed cavity that matably
receives the projecting portion of the trapezium implant, thereby
allowing articulating motion between the trapezium implant and the
first metacarpal base.
[0014] The trapezium implant can have a projecting portion that
extends outside the bounds of the trapezium into the CMC cavity to
define a substantially convex articular surface. The first
metacarpal implant base portion can have a socket with a
substantially concave cavity sized and configured to matably
receive the projecting portion of the trapezium implant.
[0015] Other embodiments are directed to medical kits for thumb CMC
joint arthoplasty. The kits include: (a) at least one trapezium
implant; (b) at least one first metacarpal intramedullary stem
implant; and (c) a plurality of base members having different sizes
and/or shapes, each of the base members configured to serially
attach to the first metacarpal intramedullary stem implant. In
position, the attached base member of the intramedullary implant
and the trapezium implant articulate against each other.
[0016] In some embodiments, the at least one trapezium implant
includes at least one downwardly extending anchoring member
configured to reside in local bone of a target trapezium.
[0017] The medical kits can also include a plurality of trial
trapezium implants. The trials have a substantially planar bottom
surface and can have a non-binding fin or keel or are devoid of a
downwardly extending anchoring member.
[0018] The medical kits may also include at least one trapezium
implant jig configured to define a bone preparation guide or
template for preparing a target trapezium to accept the trapezium
implant.
[0019] Still other embodiments are directed to jigs for a thumb CMC
arthoplasty procedure. The jigs include a rigid body having a
substantially planar top segment that merges into a substantially
planar downwardly extending side segment and at least one slot
extending across at least a portion of the top segment and down
into at least a portion of the side segment. The slot is sized and
configured to define a cutting guide for a target trapezium.
[0020] In particular embodiments, the slot is substantially
straight and substantially horizontal across the top segment and
substantially vertical along the side segment.
[0021] Other embodiments are directed to methods for treating
and/or repairing a CMC joint in a patient. The methods include: (a)
implanting a trapezium implant in a target trapezium so that the
trapezium implant defines an articulating surface; and (b)
implanting a first metacarpal implant into the first metacarpal so
that the first metacarpal implant defines an articulating surface
that articulates against the trapezium implant articulating
surface.
[0022] In some embodiments, the methods also include, before the
step of implanting the trapezium implant: (i) preparing the target
trapezium for receiving the trapezium implant by planarizing the
natural articular surface of the target trapezium, then forming a
channel in the target trapezium; and (ii) trying different size
trapezium trials to determine a proper size trapezium implant for
the patient.
[0023] The methods may also include, before the step of implanting
the trapezium implant, temporarily affixing a jig with a drilling
and cutting channel guide to the trapezium, and drilling and
cutting a channel into the target using the jig drilling and
cutting channel guide.
[0024] In some embodiments, the first metacarpal implant comprises
an elongate intramedullary stem and an attachable base member with
a socket, and the method further includes, before the step of
implanting the first metacarpal implant, trying different size base
members to select a base member that substantially fills the CMC
cavity.
[0025] The foregoing and other objects and aspects of the present
invention are explained in detail in the specification set forth
below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is an anatomical drawing of the palmar aspect of the
carpal and metacarpal bones illustrating the 1st metacarpal, the
CMC joint and the trapezium.
[0027] FIG. 2 is an axial view illustrating motions of the
thumb.
[0028] FIGS. 3A and 3B are schematic illustrations of the bones of
the trapezio-metacarpaljoint (the upper bones associated with the
trapezium and the lower bones associated with the metacarpal).
[0029] FIG. 3C is an enlarged schematic illustration of the
corresponding articular surfaces of the metacarpophalangeal joint
(the trapezium and the first metacarpal base).
[0030] FIG. 4A is a side perspective view of a 1st metacarpal
implant with a cooperating trapezium implant according to
embodiments of the present invention.
[0031] FIG. 4B is an end view of the 1st metacarpal implant shown
in FIG. 4A.
[0032] FIG. 4C is an exemplary end view of the trapezium implant
shown in FIG. 4A according to some embodiment of the present
invention.
[0033] FIG. 4D is a top perspective view of an alternate
configuration of the distal end member (the shape being similar to
the natural articular surface of the CMC joint) according to some
embodiments of the invention.
[0034] FIG. 5A is an enlarged side view of the trapezium implant
shown in FIG. 4A.
[0035] FIG. 5B is an enlarged side view of an alternate
configuration of the trapezium implant shown in FIG. 4A.
[0036] FIG. 5C is an enlarged end view of the trapezium implant
shown in FIG. 5A or 5B.
[0037] FIG. 5D is an enlarged end view of an alternative
configuration of the trapezium implant shown in FIG. 5A or 5B
according to some embodiments of the invention.
[0038] FIG. 6 is a schematic illustration of a thumb with a region
of the trapezium removed to define a prepared distal surface
suitable for the trapezium implant according to embodiments of the
present invention.
[0039] FIG. 7A is a side view of an intramedullary implant portion
of a 1st metacarpal implant configured to matably attach to a
selected distal end member (facing the trapezium).
[0040] FIG. 7B is an opposing side view of the distal end member
shown in FIG. 7A.
[0041] FIG. 7C is a side view of an articulating base member for a
saddle configuration of the 1st metacarpal with the intramedullary
portion of the implant in position and the distal end member
attached thereto and extending beyond the bounds of the metacarpal
to define an articular surface according to some embodiments of the
present invention.
[0042] FIG. 7D is a side view of an alternate attachment
configuration for the intramedullary member and the distal end
member according to other embodiments of the invention.
[0043] FIG. 8 is an exploded view of an alternate configuration of
the trapezium implant and the cooperating 1st metacarpal implant
according to yet other embodiments of the invention.
[0044] FIGS. 9A and 9B are schematic illustrations of a trapezial
jig according to embodiments of the invention.
[0045] FIG. 10 is a schematic illustration of a drill that extends
through the jig shown in FIGS. 9A and 9B to define an anchoring
tunnel, aperture or hole for the trapezial implant according to
some embodiments of the invention.
[0046] FIG. 11A is a schematic illustration of a saw that extends
through the jig shown in FIGS. 9A and 9B to connect the anchoring
holes with a distal cut surface of the trapezium according to
embodiments of the invention.
[0047] FIG. 11B is a schematic illustration of a surgically
prepared trapezium according to embodiments of the invention.
[0048] FIG. 12 is a schematic illustration of a broach that can be
used to size the 1st metacarpal implant. A trial can be inserted to
determine the appropriate implant size.
[0049] FIG. 13A is a schematic illustration of a medical set or kit
of different sized trapezium trials according to embodiments of the
present invention.
[0050] FIGS. 13B and 13C are alternate end views of other trapezium
trials according to embodiments of the present invention.
[0051] FIG. 14 is a schematic illustration of a medical set or kit
of different components for a CMC total joint replacement procedure
according to embodiments of the invention.
[0052] FIG. 15 is a flow chart of exemplary operations that can be
used to carry out embodiments of the invention.
[0053] FIGS. 16-23 illustrate exemplary steps that can be used to
surgically implant a total TCMA prosthesis according to embodiments
of the present invention.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0054] The present invention will now be described more fully
hereinafter with reference to the accompanying figures, in which
embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein. Like
numbers refer to like elements throughout. In the figures, certain
layers, components or features may be exaggerated for clarity, and
broken lines illustrate optional features or operations unless
specified otherwise. In addition, the sequence of operations (or
steps) is not limited to the order presented in the figures and/or
claims unless specifically indicated otherwise. In the drawings,
the thickness of lines, layers, features, components and/or regions
may be exaggerated for clarity and broken lines illustrate optional
features or operations, unless specified otherwise.
[0055] It will be understood that when a feature, such as a layer,
region or substrate, is referred to as being "on" another feature
or element, it can be directly on the other feature or element or
intervening features and/or elements may also be present. In
contrast, when an element is referred to as being "directly on"
another feature or element, there are no intervening elements
present. It will also be understood that, when a feature or element
is referred to as being "connected", "attached" or "coupled" to
another feature or element, it can be directly connected, attached
or coupled to the other element or intervening elements may be
present. In contrast, when a feature or element is referred to as
being "directly connected", "directly attached" or "directly
coupled" to another element, there are no intervening elements
present. Although described or shown with respect to one
embodiment, the features so described or shown can apply to other
embodiments.
[0056] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and should not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein. The term "polymer" includes copolymers and
derivatives and/or combinations thereof.
[0057] The implant can be a total joint replacement implant that
allows articulation of the bones. The term "total joint
replacement" means that both the base of the first metacarpal and
the opposing articular surface of the trapezium are replaced with
cooperating implant surfaces, resulting in a total thumb
carpo-metacarpal arthroplasty (TCMA), thereby providing complete
joint replacement as in total hip arthroplasty (THA) or total knee
arthroplasty (TKA).
[0058] As shown in FIG. 4A, embodiments of the invention provide an
intramedullary first metacarpal implant 40 that cooperates with a
trapezium implant 60. The first metacarpal implant 40 includes a
base portion 45 that defines a base of the CMC joint. As shown, the
base portion 45 has a socket 46 (FIG. 4B) that matably receives the
projecting portion 61 of the trapezium implant 60, allowing
articulation between the two implants 40, 60 such that the
corresponding articulating surfaces 40s, 60s articulate against
each other. In the embodiment shown in FIG. 4A, the first
metacarpal implant 40 has a substantially concave articulating
surface 40s substantially matched to a convex articulating surface
60s of the trapezium implant 60. The first metacarpal implant 40
can be a single unitary member or can include a matable base member
that defines the articulating surface 40s. For example, if the
implants 40, 60 comprise pyrocarbon or a similarly lubricious
and/or strong composite or polymer, the two surfaces 40s, 60s can
articulate against each other without requiring an intermediary
material or component. Alternatively, if the first metacarpal
implant 40 and trapezium implant 60 are made out of stainless steel
or titanium or other suitable biomedical metal, then a base member
(typically attached to the first implant 40) can be used to define
one of the articulating surfaces, formed of a suitable
biocompatible material, such as, for example, polyethylene (so that
there is no "metal on metal" contact for the articulating surfaces
40s, 60s).
[0059] In other embodiments, the first metacarpal implant 40 can
include a base portion 45 that is shaped as a substantially
anatomically equivalent of a natural metacarpal base (FIGS. 3B and
3C) and, similarly, the trapezium implant 60 can have a
corresponding substantially natural anatomic distal articular
surface that can cooperate with the first metacarpal implant 40.
Examples of implants 45, 60 with alternative articulating surfaces
40s, 60s having more natural surface contours are shown in FIG. 4D.
The implants 40, 60 can thus define a natural anatomical contour of
the CMC joint to act as a resurfacing implant system.
[0060] FIG. 4B is an end view of the base portion 45 of the first
metacarpal implant 40 shown in FIG. 4A that can define a receiving
socket 46 with the articulating surface 40s forming part of the CMC
replacement joint. The socket 46 can have a width "W.sub.1" with an
overall width of the base portion 45 can have a width "W.sub.2".
The implant 40 can be provided in different sizes with different
widths, recognizing that the anatomical constraints and needs will
likely vary by patient (age, gender, bone structure and the like).
In some embodiments, the socket 46 has a concave hemispherical
shape with an arc radius R.sub.1.
[0061] FIG. 4C illustrates an end view of the trapezium implant 60
shown in FIG. 4A. As shown, the implant 60 includes at least one
anchoring member 63, shown as two keels 63.sub.1, 63.sub.2. More or
fewer anchoring members 63 can be used and different anchoring
member configurations may also be used. FIG. 4A illustrates that
the anchoring member 63 can be oriented to extend transversely
across at least a major portion of the width of the implant 60.
[0062] The keels 63.sub.1, 63.sub.2 are typically rigid and reside
in a bone tunnel or channel formed in the trapezium, but may be
flexible and/or otherwise configured to promote and/or allow for
local tissue ingrowth. The implant 60 can have a substantially
planar bottom mounting surface 62 and the at least one anchoring
member 63 can extend below the bottom surface 62. As shown, the
anchoring member 63 can extend downwardly substantially orthogonal
to the mounting surface 62, but the anchoring member 63 may be
oriented at different angles.
[0063] The thickness T.sub.1 of the projecting portion of the
trapezium implant 60 can vary to allow a clinician to select the
size that substantially fills the target CMC cavity. Sets of the
implant 60 can be provided with different thickness T.sub.1 to
allow a clinician to select an appropriate one for the patient, as,
again, the desired thickness may vary due to target anatomical
considerations, age, gender and the like. The downwardly extending
length of the anchoring member 63 (e.g., keels 63.sub.1, 63.sub.2),
is typically between about 0.1 inch to about 0.25 inches, defining
an overall thickness T.sub.2. In some embodiments, the projecting
portion (e.g., dome) 61 can have a convexity with a radius R.sub.2
that may, in some particular embodiments, be between about 1/8 inch
to about 3/8 inches, which is typically slightly less than that of
the socket radius R.sub.1, thereby allowing for an articulating
snug fit to inhibit misalignment or separation during
articulation.
[0064] FIG. 5A is an enlarged side view of the trapezium implant
60. As shown, the at least one anchoring member 63 can reside
inside the bounds of the bottom surface 62 and terminate prior to
the outer portions thereof. FIG. 5B illustrates that the at least
one anchoring member 63 can extend closer to one outer side edge of
the implant than the opposing side edge. FIG. 5C illustrates that
the at least one anchoring member 63 can have a larger and/or
differently configured lower portion 64. As shown, the at least one
anchoring member 63 can have a substantially thin planar body that
merges into a substantially circular (cross-section) lower portion
64. As will be discussed further below, the lower portion can
reside in a correspondingly shaped tunnel or channel in local bone
to help retain the implant in a desired position. Alternatively, or
in combination with the anchoring member(s) 63, bone cement or
other anchoring mechanisms may be used. FIG. 5D illustrates an
alternative anchoring member configuration, located substantially
medially on the implant body 60. The lower portion 64 may be
flexible and able to be press fit into a holding bone channel or
tunnel. Combinations of the above anchoring configurations or other
configurations may also be used.
[0065] To prepare the surgical site for the implants 40, 60, the
base of the 1.sup.st metacarpal can be planarized and/or flattened
and the intramedullary implant 42 can be inserted into the proximal
portion of the 1.sup.st metacarpal 20. Similarly, as shown in FIG.
6, the distal articulating portion 10r of the anatomic trapezium
can be removed to flatten and planarize the implant support surface
and the implant 60 can be attached to the remaining trapezium. The
first metacarpal intramedullary component 42 can be selected to
fill and match the contour of the target endosteal (inside) surface
of the proximal aspect of the first metacarpal 20. FIG. 7A
illustrates that the implant 40 can include a base portion 45 that
is matably attachable to the intramedullary portion 42 (e.g.,
stem). The intramedullary portion 42 of the implant 40 can be
provided in various sizes to allow for correct patient sizing.
Similarly, the base portion 45 can be provided in different sizes
and/or configurations to allow a clinician to select the
appropriate size for a patient.
[0066] In some embodiments, the implants 40, 60 can be provided in
S, M, L and XL sizes, such as in the exemplary sizes provided
below. The size of the trapezium implant 60 will determine the
desired size of the first metacarpal implant 40, making the size of
the trapezium implant 60 determinate thereof.
TABLE-US-00001 Size Trapezium Radius 1st MC base member Small 3-4
mm (typically about matching 1/8 inch (3.18 mm)) Medium 5-7 mm
(typically about 1/4 matching inch (6.35 mm)) Large 8-10 mm
(typically about matching 3/8 inch (9.52 mm))
[0067] The intramedullary surface 42s of the implant 42 can be
roughened (cintered, pitted, scraped, filed, contoured, etc.) to
promote bone ingrowth. The intramedullary implant 42 can be press
fit into position, but also or alternatively can be cemented in
with suitable biocompatible cement, such as, for example,
polymethylmerthacolate. The intramedullary implant 42 can be
manufactured out of various substantially rigid biocompatible
materials, such as metals, rigidized polymers, ceramics, and/or
carbon. As shown in FIG. 7A, the intramedullary implant 42 can
include a locking member 44 to mate to the base portion 45 which
defines the articular component. FIG. 7A shows that the locking
member 44 can be a trunnion or post and FIG. 7B illustrates that
the base portion 45 can include an aperture or channel 49 sized and
configured to matably receive the locking member 44. FIG. 7C
illustrates that the base portion 45 with the 1.sup.st MC
articulating component can have a saddle ("natural") configuration
and may be snap-fitted and/or locked onto the proximal portion of
the 1.sup.st MC intramedullary component 42. FIG. 7D illustrates
that the base portion 45 can include the locking member 44 while
the intramedullary implant 42 can include the corresponding locking
aperture 49. In other embodiments, the first metacarpal implant 40
can be pre-formed at an OEM or offsite location or defined by a
single member (not shown).
[0068] In some embodiments, the intramedullary implant 42 and the
trapezium implant 60 are metallic while the base portion 45 can
comprise a polymer that provides the articulating surface 40s with
the desired sliding frictional and/or lubricity property. The base
portion 45 can be formed of a unitary member and material, similar
to a spacer. In some embodiments, the base portion 45 comprises
polyethylene. It can be provided in varying thicknesses as
discussed herein in order to substantially fill the articulating
cavity of the CMC joint. As also noted above, the articulating
surface 40s can be substantially concave in shape but also can be
fashioned more like an anatomic 1.sup.st MC articular surface
(e.g., saddle shaped), as noted above (see, e.g., FIGS. 4D,
7C).
[0069] The trapezial implant 60 has an articulating surface 60s
that can be generally and/or substantially convex but also can be
saddle shaped. The convex shape can reduce the stresses on the
component at the bone implant interface.
[0070] FIG. 8 also shows that the trapezium implant 60 can define a
socket that has a substantially concave articulating surface 60s
while the base portion 45 of the first metacarpal implant 40 can be
substantially convex. The concave shape may reduce the stresses on
the component at the bone implant interface.
[0071] The anchoring member 63 of the trapezium implant 60 can be
configured to be resistance-fitted. The keel(s) and/or anchoring
portion of the implant 60 can be forced into position by hammering,
pushing and/or forcibly sliding the implant 60 into place. The
placement can be done by overcoming the friction of the trapezial
bone against the implant 60. A jig or series of jigs can be
employed to prepare the implant bone site to facilitate the
implantation (see, for example, an exemplary surgical procedure
described below). The lower bone contact surface of the implant 60
and/or anchoring member(s) 63 can be roughened to promote bone
ingrowth. The trapezium implant 60 can be configured to withstand
loosening forces. The implant system can allow early motion,
obviating the need for a cast post-operatively.
Surgical Procedure
[0072] It is contemplated that the implantation procedure should be
able to be completed in less than about 1.5 hours. It may be
performed under intravenous block anesthesia, but axillary block or
general anesthesia are additional options. During the surgical
procedure, the hand is typically in the palm up or semi-supinated
position. A Wagner approach can be used, taking down the thenar
muscles to expose the CMC capsule. A suitable needle, such as an
18-gauge needle, can be inserted into the CMC joint, identifying
the joint. The CMC capsule can be incised axially, in line with the
joint surface, taking care to preserve the capsular attachments to
the trapezium and the base of the first metacarpal. The capsular
cut can be made closer to the trapezium since the capsular
attachment to the base of the 1.sup.st MC is tenuous. As shown in
FIG. 6, a wafer of bone comprising the articular surface is cut
from the distal aspect of the trapezium with a suitable cutting
member, such as, for example, a microsagital saw. This cut can be
flat and made parallel to the scapho-trapezial joint, that is,
perpendicular to the long axis of the trapezium. A thin wafer of
articular surface can also be cut from the proximal aspect of the
base of the first metacarpal (1.sup.st MC).
[0073] Next, as shown in FIG. 9A, a trapezial jig 80 is applied to
the trapezium 10 with its flat top surface 81 placed against the
distal cut surface of the trapezium. The jig 80 can be rigid and
may be metallic. The jig 80 has a top segment 80s that merges into
a downwardly-extending side segment 80s. The jig 80 can include
cutting and drilling guide channels 83 and holding apertures 81a
that allow pins, staples, nails, screws, wires and/or sutures to
hold the jig 80 in position. The drilling and cutting guide
channels 83 can be slots that extend across the top segment 80s
down through at least a major portion of the side segment 80s.
Although shown with two channels 83, the jig 80 can include one
channel or more than two channels, typically corresponding to the
number of anchoring members 63 (FIG. 5C). Also as shown, the
channels 83 can end at a keyhole 84 that is sized and configured to
correspond to a shape that can receive the lower portion of the
anchoring member 63. As shown, the shape is circular, and may be
sized to be the same or slightly less than the size of the lower
portion of the anchoring member 64 for frictional fit thereof.
[0074] As shown in FIG. 9B, in some embodiments, a plurality of
holding members 82, such as 0.35 or 45 kirschner wires, can be used
to secure the jig 80 to the trapezium 10. FIG. 10 illustrates a
suitably sized drill bit 85 (e.g., a 3/32'' drill bit) with a stop
feature can be used to drill the lower anchoring holes 164 (FIG.
11B) for the trapezial implant 60. Referring to FIGS. 11A and 11B,
a cutting member 86, such as a microsagital saw, can be used to
form bone tunnels or channels 163 that connect the anchoring holes
164 with the distal cut surface 10s of the trapezium to form a
prepared implant site 10p as shown in FIG. 11B. The cutting may be
done with a knife rather than a saw. Also, the cutting may be done
before or after the drilling.
[0075] The trapezial jig 80 can be removed and the thumb ray can be
extended and adducted to expose the base of the 1.sup.st MC for
intramedullary sizing. As shown in FIG. 12, broaches 90 can be
inserted to size the 1.sup.st MC. Intramedullary trials 190 (FIG.
22) can be used to select an intramedullary implant 40 or 42 of the
desired size. Trapezial trials 100 can also be inserted to
establish a suitable trapezium implant 60 size/configuration. As
shown in FIG. 13A, the trapezium trials 100a, 100b, 100c
(corresponding to different sizes) can be provided as a kit 100. In
FIG. 13A, the trials 100a-c do not include the anchoring member(s)
63. However, as shown in FIGS. 13B and 13C, the trials 100a (only
one trial is shown) can include at least one relatively thin fin
101 that can fit into the anchoring member channel and act as a
post that can inhibit rotation during the trialing (but do not bind
or lock into position). The thumb ray is distracted and the space
created is sized. A 1.sup.st MC trial 190 (typically without the
1.sup.st MC articulating surface) can be attached to the 1.sup.st
MC intramedullary trial. Range of motion is tested. The final
implants 42, 45, 60 can be inserted in the following order:
1.sup.st MC intramedullary implant 42, trapezial articulating
implant 60, and 1.sup.st MC articulating implant 45. Once
positioned, the surgeon can proceed with capsular, muscle and skin
closure and can optionally reinforce the capsule with a GRAFT
JACKET reinforcement (Wright Medical Technologies). A removable
thumb spica splint can be used for support and range of motion can
begin early.
[0076] FIG. 14 illustrates an exemplary medical kit 125 that can
include trial base implants 145, trial trapezium implants 100a,
100b, a selection of different size actual implants 42, 45, 60 (or
these may be provided separately in individual sterilized sealed
packages) and optionally broaches 90 and/or intramedullary trials
190 (not shown), all in a sterile package or packages. The kit 125
may also include the jig(s) 80, saw 86 and/or drill bit 85 (with or
without drill).
[0077] FIG. 15 is a flow chart of exemplary operations that can be
used to carry out embodiments of the invention. As shown, a
trapezium implant can be implanted in a target (prepared) trapezium
so that the trapezium defines an articulating surface of a CMC
joint in a patient (block 200).
[0078] In some particular embodiments, the target trapezium can be
prepared for receiving the trapezium implant by planarizing the
natural articular surface of the target trapezium (removing a thin
wafer), then forming at least one channel in the target trapezium
(block 202). Different size trapezium trials can be positioned in
the CMC joint to determine a proper size trapezium implant for the
patient (block 204).
[0079] In some embodiments, before the step of implanting the
trapezium implant, a jig with a drilling and cutting channel guide
can be temporarily affixed to the trapezium, and at least one
channel can be drilled and/or cut into the target trapezium using
the jig drilling and cutting channel guide (block 206).
[0080] The first metacarpal implant can include an elongate
intramedullary stem and an attachable base member with a socket,
and before the step of implanting the first metacarpal implant, the
method may include trying different size base members to select a
base member that substantially fills the CMC cavity (block
208).
[0081] FIGS. 16-23 schematically illustrate the steps in an
exemplary surgical procedure. FIG. 16 illustrates that a Wagner
incision is made. FIG. 17 illustrates that a capsular incision (do
not section abductor to thumb). FIG. 18 illustrates the 1st
metacarpal articular resection 300 (variable according to space
needed) and a minimal trapezium resection 400 to preserve bone for
the trapezium implant 60. FIG. 19 illustrates the jig 80 in
position (pinned in place) and a drill 85 used to create the
anchoring hole 164 for the keel 63. As shown, the drill bit 85 can
include a stop collar to inhibit forward movement of the drill into
the trapezium at a certain distance. FIG. 20 illustrates the saw 86
for creating the keel shaft 163 in the bone. FIG. 21 shows the
thumb adducted and extended for the first metacarpal base exposure
and a broach 93 used to (rasp, broach and/or prepare) an
intramedullary space for the first metacarpal implant 40. FIG. 22
illustrates the placement of the trapezium trial 100a (with
anti-rotational fin 101) and first metacarpal trial 190. A
clinician can measure or size the distance or size "D" of the gap
350 created between the first metacarpal base and the trapezial
implant 60, then select the appropriate articulating thickness. As
shown, where a separate base member 45 is used, this member 45 can
define the articulating thickness. In other embodiments, the entire
implant 40 can be selected from a kit to provide the desired
thickness.
[0082] The foregoing is illustrative of the present invention and
is not to be construed as limiting thereof. Although a few
exemplary embodiments of this invention have been described, those
skilled in the art will readily appreciate that many modifications
are possible in the exemplary embodiments without materially
departing from the novel teachings and advantages of this
invention. Accordingly, all such modifications are intended to be
included within the scope of this invention as defined in the
claims. In the claims, means-plus-function clauses, if used, are
intended to cover the structures described herein as performing the
recited function and not only structural equivalents but also
equivalent structures. Therefore, it is to be understood that the
foregoing is illustrative of the present invention and is not to be
construed as limited to the specific embodiments disclosed, and
that modifications to the disclosed embodiments, as well as other
embodiments, are intended to be included within the scope of the
appended claims. The invention is defined by the following claims,
with equivalents of the claims to be included therein.
* * * * *