U.S. patent application number 16/107671 was filed with the patent office on 2019-02-28 for system, apparatus, and method for grafting tissue.
The applicant listed for this patent is The Curators of the University of Missouri. Invention is credited to James L. Cook, Ferris M. Pfeiffer, Aaron M. Stoker.
Application Number | 20190059911 16/107671 |
Document ID | / |
Family ID | 50934904 |
Filed Date | 2019-02-28 |
United States Patent
Application |
20190059911 |
Kind Code |
A1 |
Pfeiffer; Ferris M. ; et
al. |
February 28, 2019 |
SYSTEM, APPARATUS, AND METHOD FOR GRAFTING TISSUE
Abstract
Systems, apparatus, and methods may be adapted for grafting
tissue at a tissue site that may include an elongate housing and a
plurality of elongate cutting members. The plurality of elongate
cutting members may define a cutting surface at a distal end of the
elongate housing. The cutting surface may be adapted to contract
from a first diameter to a second diameter that is less than the
first diameter. The contraction of the cutting surface from the
first diameter to the second diameter may define a tapered profile
between the first diameter and the second diameter suitable for
obtaining a tapered graft.
Inventors: |
Pfeiffer; Ferris M.;
(Boonville, MO) ; Stoker; Aaron M.; (Columbia,
MO) ; Cook; James L.; (Columbia, MO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Curators of the University of Missouri |
Columbia |
MO |
US |
|
|
Family ID: |
50934904 |
Appl. No.: |
16/107671 |
Filed: |
August 21, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15582287 |
Apr 28, 2017 |
10080570 |
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16107671 |
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14102187 |
Dec 10, 2013 |
9668754 |
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15582287 |
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61735456 |
Dec 10, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23B 51/0453 20130101;
A61B 17/1615 20130101; A61B 17/1635 20130101; B23B 51/0406
20130101; B23B 51/05 20130101; B23B 51/04 20130101; B23B 51/0413
20130101; B23B 2251/428 20130101; A61B 17/3417 20130101; A61B
17/1613 20130101; A61B 17/1604 20130101; A61B 17/3439 20130101;
B23B 2251/54 20130101; A61B 17/16 20130101; A61B 17/1622
20130101 |
International
Class: |
A61B 17/16 20060101
A61B017/16; A61B 17/34 20060101 A61B017/34 |
Claims
1.-20. (canceled)
21. A tapered graft tissue comprising an insertion end and an
exposed end separated by a length, the tapered graft tissue having
a first diameter at the exposed end that is larger than a second
diameter at the insertion end, the length between the first
diameter and the second diameter defining an external taper.
22. The tapered graft tissue of claim 21, wherein the entire length
between the first diameter and the second diameter defines the
external taper.
23. The tapered graft tissue of claim 21, wherein the first
diameter is substantially concentric with the second diameter.
24. The tapered graft tissue of claim 21, wherein the tapered graft
tissue is adapted to self-align with a tapered socket.
25. The tapered graft tissue of claim 21, wherein the tapered graft
tissue has a conical, frustoconical, or pyramidal shape.
26. The tapered graft tissue of claim 21, wherein the first
diameter is about 8 millimeters.
27. The tapered graft,tissue of claim 21, wherein the first
diameter is about 20 millimeters.
28. The tapered graft tissue of claim 21, wherein the length is
about 6 millimeters.
Description
RELATED APPLICATION
[0001] This application claims the benefit, under 35 USC .sctn.
119(e), of U.S. Provisional Patent Application Ser. No. 61/735,456,
entitled "System, Apparatus, and Method for Grafting Tissue," filed
Dec. 10, 2012, which is incorporated herein by reference for all
purposes.
BACKGROUND
1. Field
[0002] This specification relates generally to systems, apparatus,
and methods adapted for grafting tissue at a tissue site. The
systems, apparatus, and methods may be suitable, for example, for
performing osteochondral allografts, autografts, and grafts with
other tissue types.
2. Discussion
[0003] Common usages for tissue grafts may include the treatment of
cartilage defects. For example, an osteochondral allograft (OCA) is
a type of tissue graft commonly used to treat cartilage defects
resulting from osteochondrosis, trauma, and osteoarthritis. Current
OCA techniques may utilize cylindrically shaped grafts having a
straight longitudinal sidewall that are inserted into a similarly
shaped cylindrical cavity or socket and held in place with a
press-fit interface. The insertion of the cylindrically shaped
graft may require large insertion forces to overcome the frictional
resistance between the sidewall of the cylindrical graft and a
sidewall of the corresponding cylindrical cavity. Installation of
the graft may require mechanical impacting. Studies have shown that
such mechanical insertion techniques may negatively impact
chondrocyte viability in the grafts and long term outcomes of the
procedure.
SUMMARY
[0004] The disclosed systems, apparatus, and methods may be
adapted, in part, to decrease insertion force and energy required
to achieve installation of grafts to overcome the problems
associated with conventional technologies and methods.
[0005] In some illustrative embodiments, a cutting apparatus for
providing a tapered tissue graft may include an annular cutting
surface that may be adapted to contract from a first diameter to a
second diameter that is less than the first diameter.
[0006] In other illustrative embodiments, a cutting apparatus for
providing a tapered tissue graft may include an elongate housing
and a plurality of elongate cutting members. The elongate housing
may have a proximal end, a distal end, and a bore defining a
longitudinal axis. The elongate cutting members may define an
annular cutting surface at the distal end of the elongate housing.
The annular cutting surface may be adapted to contract from a first
diameter to a second diameter that is less than the first diameter.
The contraction of the annular cutting surface from the first
diameter to the second diameter may define a tapered profile
between the first diameter and the second diameter.
[0007] In some illustrative embodiments, a system adapted for
grafting tissue at a tissue site, may include an elongate housing,
a plurality of elongate cutting members, and a plunger. The
elongate housing may have a proximal end, a distal end, and a bore
defining a longitudinal axis. The plurality of elongate cutting
members may extend lengthwise at the distal end of the elongate
housing, and may be positioned about the longitudinal axis of the
elongate housing. The elongate cutting members may define an
annular cutting surface adapted to contract from a first diameter
to a second diameter that is less than the first diameter. The
contraction of the annular cutting surface from the first diameter
to the second diameter may define a tapered profile between the
first diameter and the second diameter. The plunger may have an
external surface and may be slidably disposed in the bore of the
elongate housing. When the annular cutting surface has the first
diameter, the elongate cutting members may be biased against the
external surface of the plunger at the distal end of the elongate
housing.
[0008] In some illustrative embodiments, a method of grafting
tissue at a tissue site may include inserting a tapered graft
tissue into a corresponding tapered socket at the tissue site.
[0009] In other illustrative embodiments, a method of grafting
tissue at a tissue site may include obtaining a tapered graft
tissue having an insertion end and an exposed end separated by a
length. The tapered graft tissue may have a first diameter at the
exposed end that is larger than a second diameter at the insertion
end. The length between the first diameter and the second diameter
may define an external taper. The method may additionally include
preparing a tapered socket in the tissue site for receiving the
tapered graft tissue. The tapered socket may define an internal
taper that substantially corresponds to the external taper of the
tapered graft tissue. The method may also include inserting the
tapered graft tissue into the tapered socket.
[0010] In other illustrative embodiments, a method of grafting
tissue at a tissue site may include providing a cutting apparatus
comprising an elongate housing, a plurality of elongate cutting
members, and a plunger. The elongate housing may have a proximal
end, a distal end, and a bore defining a longitudinal axis. The
plurality of elongate cutting members may extend lengthwise at the
distal end of the elongate housing, and may be positioned about the
longitudinal axis of the elongate housing. The elongate cutting
members may define an annular cutting surface that may be adapted
to contract from a first diameter to a second diameter that is less
than the first diameter. The contraction of the annular cutting
surface from the first diameter to the second diameter may define a
tapered profile between the first diameter and the second diameter.
The plunger may have an external surface, and may be slidably
disposed in the bore of the elongate housing. When the annular
cutting surface has the first diameter, the elongate cutting
members may be biased against the external surface of the plunger
at the distal end of the elongate housing. The method may
additionally include positioning the plunger at the distal end of
the elongate housing to place the annular cutting surface in the
first diameter, and inserting the annular cutting surface
longitudinally into a donor tissue source. Further, the method may
include displacing the plunger toward the proximal end of the
elongate housing with donor tissue entering the bore of the
elongate housing as the annular cutting surface advances into the
donor tissue source. Additionally, the method may include obtaining
a tapered graft tissue having an external taper by contracting the
annular cutting surface from the first diameter to the second
diameter along the tapered profile as the plunger is displaced.
Further, the method may include reaming a tapered socket in the
tissue site for receiving the tapered graft tissue. The tapered
socket may define an internal taper that substantially corresponds
to the external taper of the tapered graft tissue. The method may
also include inserting the tapered graft tissue into the tapered
socket.
[0011] In some illustrative embodiments, provided is a tapered
graft tissue for inserting in a tapered socket. The tapered graft
tissue may include an insertion end and an exposed end separated by
a length. The tapered graft tissue may have a first diameter at the
exposed end that is larger than a second diameter at the insertion
end. The length between the first diameter and the second diameter
may define an external taper.
[0012] Other objects, features, and advantages of the illustrative
embodiments will become apparent with reference to the drawings and
detailed description that follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1A is a perspective view of an illustrative embodiment
of a cutting apparatus for grafting tissue at a tissue site
depicting a plunger positioned toward a distal end of an elongate
housing and an annular cutting surface positioned in a first
diameter;
[0014] FIG. 1B is a perspective view of the cutting apparatus of
FIG. 1A, depicting the plunger positioned toward a proximal end of
the elongate housing and the annular cutting surface positioned in
a second diameter;
[0015] FIG. 2 is a top view of a proximal end of an illustrative
embodiment of a cutting apparatus for grafting tissue at a tissue
site, depicting a plunger guide rod received within an arbor
coupled to an elongate housing;
[0016] FIG. 3 is a perspective view of an illustrative embodiment
of a cutting apparatus for grafting tissue at a tissue site
including an annular cutting surface having serrations;
[0017] FIG. 4 is a perspective view of an illustrative embodiment
of a cutting apparatus for grafting tissue at a tissue site
including a smooth annular cutting surface;
[0018] FIG. 5A is a perspective view of an illustrative embodiment
of a tapered reamer;
[0019] FIG. 5B is a perspective view of a reamer guide pin suitable
for use with the tapered reamer of FIG. 5A;
[0020] FIG. 6 is a perspective view of a an illustrative embodiment
of a tapered graft tissue and an illustrative embodiment of a
corresponding tapered socket in a tissue site;
[0021] FIGS. 7A-7E illustrate experimental results of cell
viability representative on day zero and day three for both a prior
art cylindrical graft and a tapered graft tissue according to this
disclosure;
[0022] FIGS. 8A-8C illustrate experimental results of cell death
for both a prior art cylindrical graft and a tapered graft tissue
according to this disclosure;
[0023] FIGS. 9A-9C illustrate experimental results of insertion
force, insertion energy, and extraction force for both a prior art
cylindrical graft and a tapered graft tissue according to this
disclosure;
[0024] FIGS. 10A-10B illustrate experimental results of insertion
energy and extraction force for both a 20 millimeter diameter prior
art cylindrical graft and a 20 millimeter diameter tapered graft
tissue according to this disclosure; and
[0025] FIG. 11 provides an illustrative embodiment of a plunger
that may include an external surface rotatable about a tissue
contact surface.
DETAILED DESCRIPTION
[0026] In the following detailed description, reference is made to
the accompanying drawings that depict non-limiting illustrative
embodiments for practicing the subject matter disclosed in this
specification. Other embodiments may be utilized and logical,
structural, mechanical, electrical, and chemical changes may be
made without departing from the scope of this specification. To
avoid detail not necessary to enable those skilled in the art to
practice the subject matter disclosed herein, the description may
omit certain information known to those skilled in the art.
Therefore, the following detailed description is provided without
limitation, and with the scope of the illustrative embodiments
being defined by the appended claims.
[0027] This specification relates to systems, apparatus, and
methods that may be adapted to provide a tissue graft having a
tapered external surface and a corresponding internally tapered
socket in a tissue site for receiving the tissue graft. The
disclosed systems, apparatus, and methods may reduce the forces
required to implant the tapered tissue graft in the tapered socket
while attaining the desired stability for graft healing and
incorporation. The benefits may include increased chondrocyte
viability and an increase in likelihood of success for the grafting
procedure.
[0028] Referring to FIGS. 1-6, provided is a system 102 that may be
adapted for grafting tissue at a tissue site 104. The system 102
may comprise a cutting apparatus 106 for cutting a tapered graft
tissue 108. The cutting apparatus 106 may include an elongate
housing 112 and a plurality of elongate cutting members 114. The
cutting apparatus 106 may additionally include a plunger 116 that
may be adapted to actuate the elongate cutting members 114 as
described below.
[0029] Referring to FIGS. 1A-4, the elongate housing 112 may have a
proximal end 120, a distal end 122, and a bore 124 defining a
longitudinal axis 126. The bore 124 of the elongate housing 112 may
have a substantially constant internal diameter 128 along a length
130 of the elongate housing 112. The elongate housing 112 may
include optional features, such as, for example, grasping handles
134 and an arbor 136. The grasping handles 134 may be positioned
near the proximal end 120 of the elongate housing 112 to provide
stability during operation. The arbor 136 may be adapted, without
limitation, to facilitate operation of the system 102 in
combination with a desired surgical implement. The operation of the
system 102 will be described in further detail below.
[0030] The arbor 136 may be positioned at the proximal end 120 of
the elongate housing 112 and may be substantially aligned with the
longitudinal axis 126 of the elongate housing 112. For example, the
arbor 136 may be substantially concentric to the longitudinal axis
126 and the bore 124 of the elongate housing 112. In some
embodiments, as depicted in FIGS. 2-3, the arbor 136 may be adapted
to couple the elongate housing 112 to a surgical implement, such as
a drill. For example, the arbor 136 may have an octagonal
cross-section or other shape having flat surfaces 140 or keyways
disposed about a circumferential surface 142 or perimeter of the
arbor 136, to provide grip for the surgical implement. The arbor
136 may also provide an impact surface 144 at the proximal end 120
of the elongate housing 112 adapted to receive blows from, for
example, a hammer or similar instrument. In some embodiments, as
depicted in FIG. 4, the impact surface 144 of the arbor 136 may be
a portion of increased surface area on the proximal end 120 of the
elongate housing 112. In other embodiments, the impact surface 144
may be separate from the arbor 136. The arbor 136 may include an
aperture 146 that may be substantially aligned with or concentric
to the longitudinal axis 126 of the elongate housing 112 for use in
guiding the plunger 116 as described below.
[0031] Continuing with FIGS. 1A-4, the elongate housing 112 may
have a circular cross section, and may be, for example, a tube
formed of stainless steel, titanium, or similar material. The
internal diameter 128 or dimension of the bore 124 of the elongate
housing 112 may be, for example, between about 3 millimeters to
about 30 millimeters. Further, the elongate housing 112 may have a
wall 152 with a wall thickness 154 of about 1 millimeter or less.
However, the elongate housing 112 is not limited to any particular
internal diameter 128 or dimension, or wall thickness 154. Further,
the arbor 136 may be formed integrally with the elongate housing
112 or as a separate component that may be coupled to the elongate
housing 112. Without limitation, the arbor 136 may be formed of
similar materials described above for the elongate housing 112.
[0032] Referring to FIGS. 1A-1B, 3-4, and 6, the plurality of
elongate cutting members 114 may extend lengthwise at the distal
end 122 of the elongate housing 112 and may be positioned about the
longitudinal axis 126 of the elongate housing 112. The elongate
cutting members 114 may define a substantially annular cutting
surface 160 that may be adapted to contract from a first diameter
162 or first dimension shown in FIG. 1A to a second diameter 164 or
second dimension shown in FIG. 1B. The second diameter 164 or
dimension may be less than the first diameter 162 or dimension.
Further, the first diameter 162 or dimension may be substantially
concentric to the second diameter 164 or dimension, and the first
diameter 162 or dimension may substantially correspond to the
internal diameter 128 of the elongate housing 112. The contraction
of the annular cutting surface 160 from the first diameter 162 or
dimension to the second diameter 164 or dimension may define a
tapered profile 168 between the first diameter 162 or dimension and
the second diameter 164 or dimension. The tapered profile 168 may
have any dimensions and rate of taper suitable for a particular
grafting procedure. As described below, the tapered profile 168
between the first diameter 162 or dimension and the second diameter
164 or dimension of the annular cutting surface 160 may provide the
tapered graft tissue 108 with an external taper 172 or tapered
sidewall. The external taper 172 or tapered sidewall of the tapered
graft tissue 108 may substantially correspond to the tapered
profile 168 of the annular cutting surface 160 along an entire
length 174 of the tapered graft tissue 108. Although FIGS. 1A-1B
and 3-4 illustrate the annular cutting surface 160 as being
substantially annular or circular in shape, other shapes are
possible.
[0033] Continuing with FIGS. 1A-1B and 3-4, the elongate cutting
members 114 may be formed, for example, integrally with the
elongate housing 112 or as separate components coupled to the
elongate housing 112. In some embodiments, the elongate housing 112
may have longitudinal cuts 180 through the wall 152 of the elongate
housing 112 that provide the elongate cutting members 114. The
longitudinal cuts 180 may extend lengthwise along a portion of the
distal end 122 of the elongate housing 112 and about a
circumference 182 or perimeter of the elongate housing 112. In this
manner, the longitudinal cuts 180 may provide the elongate cutting
members 114 substantially as individual spring-like fingers at the
distal end 122 of the elongate housing 112. Each of the elongate
cutting members 114 or spring-like fingers may have at least one
cutting tip 186. In a relaxed state as shown in FIG. 1B, the
elongate cutting members 114 may be spring biased inward toward the
bore 124 of the elongate housing 112, positioning the annular
cutting surface 160 in the second diameter 164. Further, the
longitudinal cuts 180 may be pie-shaped as shown in FIG. 1A to
permit clearance between each of the elongate cutting members 114
when the annular cutting surface 160 is in the relaxed state and
positioned in the second diameter 164.
[0034] The at least one cutting tip 186 associated with each of the
elongate cutting members 114 may have any shape suitable for a
particular application. For example, FIGS. 1A-1B depict an
embodiment that may have one pointed cutting tip 188 positioned at
an end of each of the elongate cutting members 114. FIG. 3 depicts
an embodiment that may have a plurality of pointed cutting tips 188
positioned at an end of each of the elongate cutting members 114 to
provide saw-like serrations. FIG. 4 depicts an embodiment that may
have one flat cutting tip 190 positioned at an end of each of the
elongate cutting members 114. The flat cutting tip 190 may be
smooth rather than pointed or serrated as shown in FIGS. 1A-1B and
3, respectively.
[0035] Similar to the elongate housing 112, the first diameter 162
or dimension of the annular cutting surface 160 may be, for
example, between about 3 millimeters to about 30 millimeters. The
second diameter 164 or dimension of the annular cutting surface 160
may be any suitable diameter that is less than the first diameter
162. Further, the annular cutting surface 160 may have a thickness
192 of about 1.0 millimeter or less. However, the annular cutting
surface 160 is not limited to any particular diameter or dimension,
or thickness. Without limitation, the elongate cutting members 114
may be formed of similar materials described above for the elongate
housing 112.
[0036] Referring to FIGS. 1A-4, the plunger 116 may have an
external surface 196 and a tissue contact surface 198 and may be
slidably disposed in the bore 124 of the elongate housing 112. The
plunger 116 may include a plunger guide rod 200 that may be adapted
to extend from the plunger 116 along the longitudinal axis 126 of
the elongate housing 112. If the elongate housing 112 includes the
optional arbor 136, in some embodiments, the aperture 146 in the
arbor 136 may receive the plunger guide rod 200 to assist with
guiding the plunger 116 in the bore 124 of the elongate housing
112. Further, the plunger guide rod 200 may protrude through the
aperture 146 in the arbor 136 to the exterior of the elongate
housing 112 to permit an operator to actuate the plunger 116 from
the exterior of the elongate housing 112.
[0037] In some embodiments, as shown in FIG. 4, the aperture 146 in
the arbor 136 may have internal threads 204 sized to receive an
actuation rod 206 having a corresponding externally threaded
surface 208 and an end 210 adapted to extend from the arbor 136
into the bore 124 of the elongate housing 112. The end 210 of the
actuation rod 206 may engage the plunger guide rod 200 in the bore
124 of the elongate housing 112 for actuating the plunger 116 from
the exterior of the elongate housing 112 as the actuation rod 206
moves along the internal threads 204 of the arbor 136.
[0038] Referring to FIG. 11, in some illustrative embodiments, the
plunger 116 may be a plunger 116a including a bearing (not shown)
that may permit the external surface 196 of the plunger 116a to
rotate about or relative to the tissue contact surface 198 of the
plunger 116a. In the embodiment of FIG. 11, the tissue contact
surface 198 may be a button 199 that is rotatable on the bearing
relative to the external surface 196. In this manner, the tissue
contact surface 198, or the button 199, may be substantially
precluded from rotating relative to the tapered graft tissue 108
during operation, permitting the tissue contact surface 198, or the
button 199, to remain substantially stationary relative to the
tapered graft tissue 108. For example, a circumference 197 of the
tissue contact surface 198, or the button 199, may carry a bearing
race (not shown) with the external surface 196 of the plunger 116a
being disposed about the bearing race and rotatable thereabout.
Utilizing the bearing with the plunger 116a may enhance the ability
of the plunger 116a and cutting apparatus 106 to avoid damage to
the tapered graft tissue 108.
[0039] Continuing with FIGS. 1A-4, when the annular cutting surface
160 has the first diameter 162 as shown in FIG. 1A, the elongate
cutting members 114 may be biased against the external surface 196
of the plunger 116 at the distal end 122 of the elongate housing
112. When the plunger 116 is positioned at the distal end 122 of
the elongate housing 112, the elongate cutting members 114 may be
moved away from the relaxed state against a spring bias to position
the annular cutting surface 160 in the first diameter 162. As shown
in FIG. 1B, the plunger 116 may be slidable toward the proximal end
120 of the elongate housing 112 to permit the annular cutting
surface 160 to gradually contract to the second diameter 164 and
return to the relaxed state. In this manner, as described further
below, the annular cutting surface 160 may be adapted to
automatically contract from the first diameter 162 in FIG. 1A to
the second diameter 164 in FIG. 1B as the annular cutting surface
160 advances into an object and the object enters the bore 124 of
the elongate housing 112, displacing the plunger 116 toward the
proximal end 120.
[0040] The plunger 116 and the plunger guide rod 200 may be formed
integrally or as separate components coupled to one another.
Further, the plunger 116 and the plunger guide rod 200 may be
formed of any suitable material, such as, for example, stainless
steel, titanium, or other suitable material. The external surface
196 of the plunger 116 may have any suitable size capable of
fitting within the bore 124 of the elongate housing 112 and moving
the elongate cutting members 114 to position the annular cutting
surface 160 in the first diameter 162. For example, an increase in
the external diameter of the plunger 116 may correspond to an
increase in the first diameter 162 of the annular cutting surface
160.
[0041] Referring to FIGS. 5A-5B, the system 102 may include a
reamer 250 that may have an external cutting surface 252, a
proximal end 254, and a distal end 256. The external cutting
surface 252 of the reamer 250 may have a first diameter 262 or
proximal diameter at the proximal end 254 of the reamer 250 and a
second diameter 264 or distal diameter at the distal end 256 of the
reamer 250. The first diameter 262 at the proximal end 254 of the
reamer 250 may be larger than the second diameter 264 at the distal
end 256 of the reamer 250. The reamer 250 may be a tapered reamer
and may define a tapered profile 268, or reamer taper, between the
first diameter 262 and the second diameter 264 of the reamer 250.
The tapered profile 268 between the first diameter 262 and the
second diameter 264 of the reamer 250 may substantially correspond
to the tapered profile 168 between the first diameter 162 and the
second diameter 164 of the annular cutting surface 160. The reamer
250 may have a reamer bore 270 or guide bore substantially aligned
along a length 272 and about a longitudinal axis 274 of the reamer
250 that may be adapted to receive a reamer guide pin 276. The
reamer 250 may be rotatable about the reamer guide pin 276. The
reamer 250 and the reamer guide pin 276 may be formed of any
suitable material, such as, for example, stainless steel or
titanium.
[0042] Referring generally to FIGS. 1-6, in an illustrative
embodiment of operation, an operator may position the plunger 116
at the distal end 122 of the elongate housing 112 to position the
annular cutting surface 160 in the first diameter 162 as shown in
FIG. 1A. Upon positioning the plunger 116 and the annular cutting
surface 160 in the first diameter 162, the operator may insert the
annular cutting surface 160 longitudinally into a donor tissue
source (not shown). The annular cutting surface 160 may be advanced
into the donor tissue source along the longitudinal axis 126 of the
elongate housing 112 by pressing the annular cutting surface 160
into the donor tissue source with or without rotation of the
annular cutting surface 160. Lubrication such as saline may be
applied to the plunger 116 and annular cutting surface 160 prior to
and during insertion into the donor tissue source. Upon insertion
into the donor tissue source, the plunger 116 may move toward the
proximal end 120 of the elongate housing 112 and be displaced by
donor tissue entering the bore 124 of the elongate housing 112 as
the annular cutting surface 160 proceeds into the donor tissue
source. The operator may obtain the tapered graft tissue 108 having
the external taper 172 by the contracting action of the annular
cutting surface 160 from the first diameter 162 to the second
diameter 164 along the tapered profile 168 as the plunger 116 is
displaced toward the proximal end 120 of the elongate housing 112.
The tapered graft tissue 108 may be captured within the bore 124 of
the elongate housing 112 when the annular cutting surface 160
contracts to the second diameter 164. The tapered graft tissue 108
may be extracted from the bore 124 of the elongate housing 112 by
returning the plunger 116 from the proximal end 120 of the elongate
housing 112 to the distal end 122 of the elongate housing 112. In
some embodiments, the tapered graft tissue 108 may be extracted
from an opening (not shown) at the proximal end 120 of the elongate
housing 112.
[0043] Referring to FIG. 6, the tapered graft tissue 108 may
include a graft insertion end 280 and a graft exposed end 282
separated by the length 174 of the tapered graft tissue 108. The
tapered graft tissue 108 may have a first diameter 284, or exposed
end diameter, at the graft exposed end 282 that is larger than a
second diameter 286, or insertion end diameter, at the graft
insertion end 280. In some embodiments, substantially the entire
length 174 between the first diameter 284 and the second diameter
286 of the tapered graft tissue 108 may define the external taper
172 of the tapered graft tissue 108.
[0044] Referring to FIGS. 5A-6, the reamer 250 may be used for
reaming or preparing a tapered socket 302 in the tissue site 104
for receiving the tapered graft tissue 108. A pin insertion end 304
of the reamer guide pin 276 may be inserted into the tissue site
104 for adapting the tissue site 104 to receive the tapered graft
108. A pin exposed end 306, or opposite end of the reamer guide pin
276 that opposes the pin insertion end 304, may be inserted into
the reamer bore 270 of the reamer 250. The reamer 250 may be
rotated about the reamer guide pin 276 and advanced into the tissue
site 104 while being guided longitudinally along the longitudinal
axis 274 of the reamer 250 into the tissue site 104 by the reamer
guide pin 276. Advancing the reamer 250 into the tissue site 104
with the distal end 256 of the reamer 250 facing the tissue site
104 may create the tapered socket 302 as shown in FIG. 6.
[0045] The tapered socket 302 may define an internal taper 310 that
substantially corresponds to the external taper 172 of the tapered
graft tissue 108 for receiving the tapered graft tissue 108
therein. Thus, the tapered graft tissue 108 may be adapted to
self-align with the tapered socket 302 when the graft insertion end
280 of the tapered graft tissue 108 faces the tissue site 104 for
insertion into the tapered socket 302. Further, the tapered graft
tissue 108 and the tapered socket 302 may each have, for example, a
conical, frustoconical, or pyramidal shape. After reaming or
providing the tapered socket 302 in the tissue site 104, insertion
of the tapered graft tissue 108 into the tapered socket 302 may
take place. Prior to inserting the tapered graft tissue 108 into
the tapered socket 302, the tapered socket 302 may be finish sized
to receive the tapered graft tissue 108 with, for example, a tamp
(not shown). The tamp may have an externally tapered profile
substantially corresponding to the external taper 172 of the
tapered graft tissue 108 to provide final sizing of the tapered
socket 302 for accepting the tapered graft tissue 108.
Experimental Results
[0046] Referring to FIGS. 7A-9C, fresh femoral condyles and humeral
heads were obtained from donor tissue sources. Cylindrical grafts 8
millimeters in diameter and 6 millimeters in height were created
and implanted using a conventional system. Tapered grafts having an
8 millimeter first diameter at a top or exterior facing surface and
a 6 millimeter height were implanted using a tapered graft system
according to this disclosure. The cylindrical grafts and the
tapered grafts were obtained from and implanted into the same
specimen. After surgical implantation, the cylindrical grafts and
the tapered grafts were analyzed at day zero to determine the
immediate effect of graft implantation on cell viability and at day
three to determine how changes in cell viability develop over time
after implantation. For day zero testing, the cylindrical grafts
and the tapered grafts were placed in a tissue culture media during
processing for cell viability testing. For day three testing, the
cylindrical grafts and the tapered grafts were placed in the same
tissue culture media with standard tissue culture supplementation
and stored at 37.degree. Celsius with CO.sub.2 supplementation. For
cell viability analysis, the cylindrical and the tapered grafts
were sectioned and then assessed for cell viability by fluorescent
microscopy using the cell viability stains sytox blue (dead cell
stain) and calcein AM (live cell stain). Images of each section of
tissue were obtained, and the number of live and dead cells were
determined using a validated cell counting protocol. FIG. 7A
depicts the cell viability for the cylindrical graft at day zero,
and FIG. 7B depicts the cell viability for the tapered graft at day
zero. Further, FIG. 7C depicts the cell viability for the
cylindrical graft at day three, and FIG. 7D depicts the cell
viability for the tapered graft at day three.
[0047] Percent cell viability was calculated by dividing the live
cell count by the total cell count and multiplying the result by
100 utilizing the following formula: (live cell count/total cell
count)*100. As shown in FIG. 7E, total cell viability did not
differ significantly between the tapered and the cylindrical grafts
at both day zero and day three after implantation. Such a result
indicates that the graft type did not significantly affect total
cell viability through day three of culture after graft
insertion.
[0048] The area of superficial cell death and total tissue area
were determined on 4.times. images. The percent of superficial cell
death area was determined by dividing the area of superficial cell
death by the total area of the tissue and multiplying the result by
100 utilizing the following formula: (area of superficial cell
death/total area of the tissue)*100. The area of superficial cell
death is the ratio of the area of low cell viability in the
superficial zone compared to the total area of the grafted
cartilage tissue. The superficial area of cell death was determined
by measuring the area of low cell viability from the superficial
surface of the cartilage tissue down to the area of high cell
viability deeper in the graft. FIG. 8A depicts the superficial area
of cell death for the cylindrical graft, and FIG. 8B depicts the
superficial area of cell death for the tapered graft. As shown in
FIG. 8C, the tapered grafts had significantly less superficial cell
death compared to the cylindrical grafts, suggesting that the
tapered graft system is associated with significantly better
superficial zone preservation, which may correlate to improved
outcomes.
[0049] For biomechanical testing, frozen hind limbs from donor test
subjects were obtained. Cylindrical grafts were created using a
conventional 8 millimeter OCA graft harvester. Tapered grafts were
created using a tapered graft system according to this disclosure
having an 8 millimeter first diameter cutting surface. The
cylindrical grafts and the tapered grafts were trimmed to a depth
of 6 millimeters. A 6 millimeter deep cylindrical hole was created
for implantation of the cylindrical graft using a conventional
cylindrical cannulated reamer. Further, a 6 millimeter deep tapered
hole was created for implantation of the tapered graft using a
tapered cannulated reamer according to this disclosure. Each graft
was manually positioned within the corresponding hole and a
servo-hydraulic test machine equipped with a 880N load cell was
used to seat each graft at a rate of 0.1 millimeters per second
with force and displacement data being collected simultaneously at
100 Hertz. Insertion force was plotted as a function of
displacement and the area under this curve was calculated to yield
insertion energy for each graft. FIG. 9A depicts the insertion
force for both the cylindrical graft and the tapered graft. FIG. 9B
depicts the insertion energy for both the cylindrical graft and the
tapered graft.
[0050] To measure extraction strength, the femur was rotated
180.degree. and a guide pin was placed through the condyle until
positioned flush against the opposite side of the graft. The above
test machine was utilized to push each graft out, and the
extraction strength was calculated for each graft. FIG. 9C depicts
the extraction force for both the cylindrical graft and the tapered
graft. Statistically significant differences were determined using
the students t-test or the rank sum test, depending on data
normality, with significance set at p<0.05 using Sigma Plot.
[0051] As shown in FIGS. 9A-9B, insertion force and energy required
to optimally seat the grafts were both significantly lower for the
tapered graft system compared to the cylindrical graft system in
cadaveric tissues. However, as shown in FIG. 9C, there was not a
significant difference between the two graft types for extraction
strength required to extract the two types of grafts after
insertion. These data indicate that the tapered graft system
according to this disclosure may decrease the force and energy
required to insert tapered grafts in a clinically relevant manner.
Further, the tapered graft system may decrease the associated
damage to the tapered graft without compromising stability of the
tapered graft after insertion.
[0052] Additional testing was conducted using a tapered graft
cutter having a 20 millimeter first diameter cutting surface
according to this disclosure to measure insertion energy and
extraction force of grafts cut from human femoral condyles.
Cadaveric human femoral condyles were acquired from tissue banks.
Cylindrical grafts 20 millimeters in diameter and 6 millimeters in
height were created and implanted using a conventional cylindrical
graft system. Tapered grafts having a 20 millimeter first diameter
at a top or exterior facing surface and a 6 millimeter height were
created and implanted using a tapered graft system according to
this disclosure. Each graft was trimmed to a depth of 6 millimeters
prior to being implanted. A 6 millimeter deep cylindrical hole was
created for implantation of the cylindrical graft using a
conventional cylindrical cannulated reamer. Further, a 6 millimeter
deep tapered hole was created for implantation of the tapered graft
using a tapered cannulated reamer according to this disclosure.
Each graft was manually positioned within the corresponding hole
and a servo-hydraulic test machine equipped with a 880N load cell
was used to seat each graft. Insertion force was plotted as a
function of displacement and the area under this curve was
calculated to yield insertion energy for each graft. FIG. 10A
depicts the insertion energy for both the cylindrical graft and the
tapered graft. Additionally, the above test machine was utilized to
push each graft out as described above, and the extraction strength
was calculated for each graft. FIG. 108 depicts the extraction
force for both the cylindrical graft and the tapered graft.
Statistically significant differences were determined using the
students t-test or the rank sum test, depending on data normality,
with significance set at p<0.05 using Sigma Plot.
[0053] Similar to the results above, both the insertion force and
energy required to optimally seat the tapered grafts were
significantly lower compared to the conventional cylindrical grafts
in cadaveric tissues. However, there was not a significant
difference between the two graft types for extraction strength.
Thus, this additional testing indicates that the larger 20
millimeter tapered graft system according to this disclosure may
also decrease the force and energy required to insert tapered
grafts in a clinically relevant manner. Further, the larger 20
millimeter graft system may decrease the associated damage to the
tapered graft without compromising the stability of the tapered
graft after insertion.
[0054] In summary, the testing shows that the tapered graft system
according to this disclosure was associated with significantly
lower insertion force and energy required to seat the tapered
grafts compared to conventional cylindrical grafts. Further, the
tapered grafts exhibited similar extraction strength compared to
conventional cylindrical grafts. Thus, the tapered graft system may
allow surgeons to implant tapered osteochondral grafts, for
example, with much less damage to the grafts while still achieving
the desired stability for graft healing and incorporation.
Chondrocyte viability assessments from this study support this
premise from biomechanical testing in that the tapered grafts were
associated with significantly less cell death in the superficial
zone of the cartilage. The preservation of superficial zone
cartilage in the tapered grafts may be directly related to the
lower force and energy required for insertion, and may result in
improved clinical outcomes for grafts implanted using the tapered
graft system.
[0055] While this specification describes a number of non-limiting,
illustrative embodiments, various modifications may be made without
departing from the scope of this specification as defined by the
appended claims. Further, any feature described in connection with
any one embodiment may also be applicable to any other embodiment.
Thus, this specification contemplates that the various features of
the disclosed embodiments may be combined with one another.
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