U.S. patent application number 10/745612 was filed with the patent office on 2004-07-15 for plugs for filling bony defects.
This patent application is currently assigned to Synthes (USA). Invention is credited to Angelucci, Christopher M., Boyer, Michael L. II, Higgins, Thomas B., Kobayashi, kenneth I., Messerli, Dominique D., Paul, David C..
Application Number | 20040138748 10/745612 |
Document ID | / |
Family ID | 22704140 |
Filed Date | 2004-07-15 |
United States Patent
Application |
20040138748 |
Kind Code |
A1 |
Boyer, Michael L. II ; et
al. |
July 15, 2004 |
Plugs for filling bony defects
Abstract
The present invention relates to plugs for filling vacancies in
bone tissue. The plugs include a body and at least one end cap that
are coupled together and may be formed from bone. The body of the
plug may be a sleeve, and the plug may further include an insert
configured and dimensioned to be received in the sleeve.
Inventors: |
Boyer, Michael L. II;
(Paoli, PA) ; Paul, David C.; (Phoenixville,
PA) ; Higgins, Thomas B.; (Berwyn, PA) ;
Angelucci, Christopher M.; (Schwenksville, PA) ;
Messerli, Dominique D.; (West Chester, PA) ;
Kobayashi, kenneth I.; (Exton, PA) |
Correspondence
Address: |
JONES DAY
51 Louisiana Aveue, N.W
WASHINGTON
DC
20001-2113
US
|
Assignee: |
Synthes (USA)
|
Family ID: |
22704140 |
Appl. No.: |
10/745612 |
Filed: |
December 29, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10745612 |
Dec 29, 2003 |
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09814223 |
Mar 22, 2001 |
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60191099 |
Mar 22, 2000 |
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Current U.S.
Class: |
623/16.11 |
Current CPC
Class: |
A61F 2/44 20130101; A61F
2002/3055 20130101; A61F 2002/2835 20130101; A61F 2002/30133
20130101; A61F 2002/30158 20130101; A61F 2002/30324 20130101; A61F
2002/30331 20130101; A61F 2002/30841 20130101; A61F 2210/0004
20130101; A61F 2230/0006 20130101; A61F 2230/0067 20130101; A61F
2002/30616 20130101; A61F 2230/0058 20130101; A61F 2230/0063
20130101; A61F 2002/30225 20130101; A61F 2002/30487 20130101; A61F
2002/3082 20130101; A61F 2230/0043 20130101; A61F 2002/2817
20130101; A61F 2002/30148 20130101; A61F 2002/30228 20130101; A61F
2002/30261 20130101; A61F 2002/30599 20130101; A61F 2220/0041
20130101; A61F 2230/0013 20130101; A61F 2/442 20130101; A61F
2002/3071 20130101; A61F 2002/4638 20130101; A61F 2230/0082
20130101; A61F 2250/0026 20130101; A61F 2/4465 20130101; A61F
2/4644 20130101; A61F 2002/30327 20130101; A61F 2002/30383
20130101; A61F 2002/30131 20130101; A61F 2002/30166 20130101; A61F
2002/4635 20130101; A61F 2210/0061 20130101; A61F 2230/0069
20130101; A61F 2002/3023 20130101; A61F 2002/3054 20130101; A61F
2002/30153 20130101; A61F 2002/30354 20130101; A61F 2002/30367
20130101; A61F 2002/30459 20130101; A61F 2002/30484 20130101; A61F
2002/3079 20130101; A61F 2230/0093 20130101; A61F 2250/0039
20130101; A61F 2002/3021 20130101; A61F 2002/30477 20130101; B29L
2031/3041 20130101; A61F 2002/30011 20130101; A61F 2002/30299
20130101; A61F 2002/30494 20130101; A61F 2002/30975 20130101; A61F
2002/30507 20130101; A61F 2002/2825 20130101; A61F 2002/30062
20130101; A61F 2002/30112 20130101; A61F 2002/30179 20130101; A61F
2002/30909 20130101; A61F 2220/0025 20130101; A61F 2230/0026
20130101; A61F 2230/0028 20130101; A61F 2/30965 20130101; A61F
2002/2839 20130101; A61F 2002/30115 20130101; A61F 2002/30332
20130101; A61F 2230/0015 20130101; A61F 2/30724 20130101; A61F
2/30942 20130101; A61F 2002/30057 20130101; A61F 2002/30075
20130101; A61F 2002/30151 20130101; A61F 2002/305 20130101; A61F
2002/30593 20130101; A61F 2002/30971 20130101; A61F 2/3094
20130101; A61F 2002/30224 20130101; A61F 2002/30426 20130101; A61F
2002/30433 20130101; A61F 2002/30448 20130101; A61F 2310/00179
20130101; A61F 2002/30733 20130101; A61F 2002/30787 20130101; A61F
2220/0075 20130101; A61F 2002/30233 20130101; A61F 2002/30481
20130101; A61F 2310/00353 20130101; A61F 2002/30462 20130101; A61F
2230/0021 20130101; A61F 2002/30329 20130101; A61F 2230/0065
20130101; B29C 33/26 20130101; A61F 2002/30492 20130101; A61F
2230/0019 20130101; A61F 2002/30843 20130101; A61F 2002/30957
20130101; A61F 2220/0066 20130101; A61F 2002/30168 20130101; A61F
2002/30235 20130101; A61F 2250/0036 20130101; A61F 2002/30138
20130101; A61F 2002/30785 20130101; A61F 2230/0017 20130101; A61F
2250/0023 20130101; A61F 2310/00293 20130101; A61F 2/28 20130101;
A61F 2/4455 20130101; A61F 2002/30237 20130101; B29C 43/006
20130101; A61F 2002/30411 20130101; A61F 2002/30212 20130101; A61F
2220/0033 20130101; A61F 2220/005 20130101; A61F 2250/0006
20130101; A61F 2250/0097 20130101; A61F 2310/00023 20130101; A61F
2002/302 20130101; A61F 2002/3028 20130101; A61F 2002/30405
20130101; A61F 2002/30617 20130101; A61F 2002/30894 20130101; A61F
2230/0004 20130101; A61F 2250/0089 20130101; A61F 2310/00011
20130101; A61F 2002/30782 20130101; A61F 2002/30126 20130101; A61F
2002/30604 20130101; A61F 2230/0008 20130101; A61F 2/4611 20130101;
A61F 2002/30322 20130101; A61F 2002/30515 20130101; A61F 2002/30772
20130101; A61F 2002/30892 20130101; A61F 2250/0063 20130101; A61B
17/8875 20130101; A61F 2/30744 20130101; A61F 2002/30154 20130101;
A61F 2002/30232 20130101; A61F 2002/30387 20130101; A61F 2002/30538
20130101; A61F 2002/4649 20130101; A61F 2002/30904 20130101 |
Class at
Publication: |
623/016.11 |
International
Class: |
A61F 002/28 |
Claims
What is claimed is:
1. A plug for filling a vacancy in bone tissue, comprising a body
and at least one end cap coupled together.
2. The plug of claim 1, wherein the body comprises a sleeve with a
top end, a bottom end, an inner surface and an outer surface.
3. The plug of claim 2, further comprising an insert configured and
dimensioned to be received in the sleeve.
4. The plug of claim 3, wherein the insert is formed of cancellous
bone.
5. The implant of claim 4, wherein the cancellous bone has a fluid
concentrated therein.
6. The implant of claim 5, wherein the insert is subjected to
mechanical pressure to concentrate the fluid.
7. The implant of claim 6, wherein the mechanical pressure is
applied by aspiration.
8. The implant of claim 5, wherein the fluid is concentrated by
soaking.
9. The plug of claim 4, wherein the insert is secured to at least
one of the sleeve and end cap with at least one fastener.
10. The plug of claim 9, wherein the at least one fastener is
selected from a screw, key, pin, peg, rivet, cotter, nail, spike,
bolt, stud, staple, boss, clamp, clip, dowel, stake, hook, anchor,
tie, band, crimp, and wedge.
11. The plug of claim 9, wherein at least one of the sleeve, end
cap, insert, and fastener is formed from partially demineralized or
demineralized bone.
12. The plug of claim 9, wherein at least two of the sleeve, end
cap, insert, and fastener are bonded together with a bonding
agent.
13. The plug of claim 9, wherein at least one of the sleeve, end
cap, insert, and fastener is at least partially dehydrated to
loosely fit within a surrounding mating surface.
14. The plug of claim 4, wherein at least one of the sleeve, end
cap, and insert further comprises alignment indicia.
15. The plug of claim 2, wherein the sleeve is packed with at least
one of bone chips, bone particulate, bone fibers, bone growth
materials, hydroxyapatite, metal, resorbable material, polymer,
ceramic, and bone cement.
16. The plug of claim 15, wherein the sleeve further comprises at
least one through-hole extending from the inner surface to the
outer surface.
17. The plug of claim 16, wherein the sleeve is cylindrical.
18. The plug of claim 15, wherein the sleeve further comprises at
least one depression extending from the outer surface toward the
inner surface.
19. The plug of claim 2, wherein the sleeve further comprises a
plurality of fingers formed integrally therewith.
20. The plug of claim 1, wherein the body and the at least one end
cap are formed from bone.
21. The plug of claim 20, wherein the sleeve and end cap are formed
of cortical bone.
22. A plug for filling a vacant region in anatomical bone,
comprising: a body with a top end, a bottom end, and an outer
surface disposed between the top and bottom ends; at least one cap
disposed at an end of the body, wherein the body and at least one
cap are formed from bone.
23. The plug of claim 22, wherein the body and cap are integrally
formed.
24. The plug of claim 23, wherein the body and cap are formed from
a section of a long bone taken transverse to a long axis of the
long bone, with the body including a through-hole formed by a canal
of the long bone.
25. The plug of claim 23, wherein the body is formed of cancellous
bone and the cap is formed of cortical bone.
26. A method for filling a vacancy in bone comprising: inserting a
filler into a portion of the vacancy, the filler comprising at
least one of bone chips, bone particulate, bone fibers, bone-growth
materials, hydroxyapatite, metal, resorbable material, polymer,
ceramic, and bone cement; and fitting a cap to the vacancy to seal
the filler therein.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The benefit of Provisional Application No. 60/191,099 filed
Mar. 22, 2000 is claimed under 35 U.S.C. .sctn. 119(e).
FIELD OF THE INVENTION
[0002] The invention relates to an implant for orthopedic
applications. More particularly, the invention is related to plugs
for filling vacancies in bone tissue.
BACKGROUND OF THE INVENTION
[0003] Bone grafts have become an important and accepted means for
treating bone fractures and defects. In the United States alone,
approximately half a million bone grafting procedures are performed
annually, directed to a diverse array of medical interventions for
complications such as fractures involving bone loss, injuries or
other conditions necessitating immobilization by fusion (such as
for the spine or joints), and other bone defects that may be
present due to trauma, infection, or disease. Bone grafting
involves the surgical transplantation of pieces of bone within the
body, and generally is effectuated through the use of graft
material acquired from a human source. This is primarily due to the
limited applicability of xenografts, transplants from another
species.
[0004] Orthopedic autografts or autogenous grafts involve source
bone acquired from the same individual that will receive the
transplantation. Thus, this type of transplant moves bony material
from one location in a body to another location in the same body,
and has the advantage of producing minimal immunological
complications. It is not always possible or even desirable to use
an autograft. The acquisition of bone material from the body of a
patient typically requires a separate operation from the
implantation procedure. Furthermore, the removal of material,
oftentimes involving the use of healthy material from the pelvic
area or ribs, has the tendency to result in additional patient
discomfort during rehabilitation, particularly at the location of
the material removal. Grafts formed from synthetic material have
also been developed, but the difficulty in mimicking the properties
of bone limits the efficacy of these implants.
[0005] As a result of the challenges posed by autografts and
synthetic grafts, many orthopedic procedures alternatively involve
the use of allografts, which are bone grafts from other human
sources (normally cadavers). The bone grafts, for example, are
placed in a host bone and serve as the substructure for supporting
new bone tissue growth from the host bone. The grafts are sculpted
to assume a shape that is appropriate for insertion at the fracture
or defect area, and often require fixation to that area as by
screws or pins. Due to the availability of allograft source
material, and the widespread acceptance of this material in the
medical community, the use of allograft tissues is certain to
expand in the field of musculoskeletal surgery.
[0006] Notably, the various bones of the body such as the femur
(thigh), tibia and fibula (leg), humerus (upper arm), radius and
ulna (lower arm) have geometries that vary considerably. In
addition, the lengths of these bones vary; for example, in an adult
the lengths may vary from 47 centimeters (femur) to 26 centimeters
(radius). Furthermore, the shape of the cross section of each type
of bone varies considerably, as does the shape of any given bone
over its length. While a femur has a generally rounded outer shape,
a tibia has a generally triangular outer shape. Also, the wall
thickness varies in different areas of the cross-section of each
bone. Thus, the use of any given bone to produce an implant
component may be a function of the bone's dimensions and geometry.
Machining of bones, however, may permit the production of implant
components with standardized dimensions.
[0007] As a collagen-rich and mineralized tissue, bone is composed
of about forty percent organic material (mainly collagen), with the
remainder being inorganic material (mainly a near-hydroxyapatite
composition resembling 3Ca.sub.3(PO.sub.4).sub.2.Ca(OH).sub.2).
Structurally, the collagen assumes a fibril formation, with
hydroxyapatite crystals disposed along the length of the fibril,
and the individual fibrils are disposed parallel to each other
forming fibers. Depending on the type of bone, the fibrils are
either interwoven, or arranged in lamellae that are disposed
perpendicular to each other.
[0008] There is little doubt that bone tissues have a complex
design, and there are substantial variations in the properties of
bone tissues with respect to the type of bone (i.e., leg, arm,
vertebra) as well as the overall structure of each type. For
example, when tested in the longitudinal direction, leg and arm
bones have a modulus of elasticity of about 17 to 19 GPa, while
vertebra tissue has a modulus of elasticity of less than 1 GPa. The
tensile strength of leg and arm bones varies between about 120 MPa
and about 150 MPa, while vertebra have a tensile strength of less
than 4 MPa. Notably, the compressive strength of bone varies, with
the femur and humerus each having a maximum compressive strength of
about 167 MPa and 132 MPa respectively. Again, the vertebra have a
far lower compressive strength of no more than about 10 MPa.
[0009] With respect to the overall structure of a given bone, the
mechanical properties vary throughout the bone. For example, a long
bone (leg bone) such as the femur has both compact bone and spongy
bone. Cortical bone, the compact and dense bone that surrounds the
marrow cavity, is generally solid and thus carries the majority of
the load in major bones. Cancellous bone, the spongy inner bone, is
generally porous and ductile, and when compared to cortical bone is
only about one-third to one-quarter as dense, one-tenth to
one-twentieth as stiff, but five times as ductile. While cancellous
bone has a tensile strength of about 10-20 MPa and a density of
about 0.7, cortical bone has a tensile strength of about 100-200
MPa and a density of about 2. Additionally, the strain to failure
of cancellous bone is about 5-7%, while cortical bone can only
withstand 1-3% strain before failure. It should also be noted that
these mechanical characteristics may degrade as a result of
numerous factors such as any chemical treatment applied to the bone
material, and the manner of storage after removal but prior to
implantation (i.e. drying of the bone).
[0010] Notably, implants of cancellous bone incorporate more
readily with the surrounding host bone, due to the superior
osteoconductive nature of cancellous bone as compared to cortical
bone. Furthermore, cancellous bone from different regions of the
body is known to have a range of porosities. For example,
cancellous bone in the iliac crest has a different porosity from
cancellous bone in a femoral head. Thus, the design of an implant
using cancellous bone may be tailored to specifically incorporate
material of a desired porosity.
[0011] It is essential to recognize the distinctions in the types
and properties of bones when considering the design of implants.
Surgeons often work with bones using similar tools as would be
found in carpentry, adapted for use in the operating room
environment. This suggests that bones have some properties which
are similar to some types of wood, for example ease in sawing and
drilling. Notably, however, are many differences from wood such as
the abrasive nature of hydroxyapatite and the poor response to
local heating during machining of a bone. The combination of
tensile and compressive strengths found in bone, resulting from the
properties of the collagen and hydroxyapatite, is thus more aptly
compared to the tensile and compressive strengths found in
reinforced concrete, due to steel and cement. Furthermore, while
wood is readily available in considerable quantity, bone material
is an extremely limited resource that must be used in an extremely
efficient manner.
[0012] Various types of bone grafts are known. For example, as
disclosed in U.S. Pat. No. 5,989,289 to Coates et al., a spinal
spacer includes a body formed of a bone composition such as
cortical bone. The spacer has walls that define a chamber that is
sized to receive an osteogenic composition to facilitate bone
growth.
[0013] U.S. Pat. No. 5,899,939 to Boyce et al. discloses a
bone-derived implant for load-supporting applications. The implant
has one or more layers of fully mineralized or partially
demineralized cortical bone and, optionally, one or more layers of
some other material. The layers constituting the implant are
assembled into a unitary structure, as by joining layers to each
other in edge-to-edge fashion in a manner analogous to
planking.
[0014] With a rapidly increasing demand in the medical profession
for devices incorporating bone material, the tremendous need for
the tissue material itself, particularly allograft tissue material,
presents a considerable challenge to the industry that supplies the
material. Due to the size and shape of the bones from which the
material is harvested, and the dimensional limitations of any
particular type of bone in terms of naturally occurring length and
thickness (i.e. cortical or cancellous), there is a need for a
means by which individual bone fragments can be combined to form
larger, integral implants that are more suitable for use in areas
of larger fractures or defects. For example, the size of cortical
bone fragments needed to repair a fracture or defect site is often
not available in a thick enough form. While multiple fragments may
together meet the size and shape requirements, several prominent
concerns have placed a practical limitation on the implementation
of this concept. There is considerable uncertainty regarding the
structural integrity provided by fragments positioned adjacent to
one another without bonding or other means of securing the
fragments to each other. Moreover, there is concern over the
possibility that a fragment may slip out of position, resulting in
migration of the fragment and possible further damage in or near
the area of implantation.
[0015] In addition, due to the geometry of bones such as the femur
and tibia, all portions of the bones are not readily usable as a
result of size limitations. Thus, prior art implants, specifically
allografts, are produced with an inefficient use of source
bones.
[0016] There is a need for new, fundamental approaches to working
with and processing tissues, in particular allograft material,
especially with regard to machining, mating, and assembling bone
fragments. Specifically, there is a need for an implant that allows
more efficient use of source material. More specifically, there is
a need for an implant that is an integrated implant comprising two
or more bone fragments that are interlocked to form a mechanically
effective, strong unit.
SUMMARY OF THE INVENTION
[0017] The present invention is related to a plug for filling a
vacancy in bone tissue. The plug includes a body and at least one
end cap coupled together. The body may be a sleeve with a top end,
a bottom end, an inner surface and an outer surface. An insert
configured and dimensioned to be received in the sleeve may also be
provided. The insert may be formed of cancellous bone which may
have a fluid concentrated therein. The insert may be subjected to
mechanical pressure to concentrate the fluid, which may be applied
by aspiration. The fluid also may be concentrated by soaking.
[0018] In some embodiments, the insert is secured to at least one
of the sleeve and end cap with at least one fastener that is
selected from a screw, key, pin, peg, rivet, cotter, nail, spike,
bolt, stud, staple, boss, clamp, clip, dowel, stake, hook, anchor,
tie, band, crimp, and wedge. At least one of the sleeve, end cap,
insert, and fastener may be formed from partially demineralized or
demineralized bone, and at least two of the sleeve, end cap,
insert, and fastener may be bonded together with a bonding agent.
At least one of the sleeve, end cap, insert, and fastener may be at
least partially dehydrated to loosely fit within a surrounding
mating surface. At least one of the sleeve, end cap, and insert may
include alignment indicia. In some embodiments, the sleeve may be
packed with at least one of bone chips, bone particulate, bone
fibers, bone growth materials, hydroxyapatite, metal, resorbable
material, polymer, ceramic, and bone cement.
[0019] In some embodiments, the sleeve also may include at least
one through-hole extending from the inner surface to the outer
surface, and the sleeve may be cylindrical. In addition, the sleeve
may include at least one depression extending from the outer
surface toward the inner surface. Furthermore, the sleeve may
include a plurality of fingers formed integrally therewith.
[0020] The body and the at least one end cap of the plug may be
formed from bone, with the sleeve and end cap being formed of
cortical bone.
[0021] The present invention also is related to a plug for filling
a vacant region in anatomical bone. The plug includes a body with a
top end, a bottom end, and an outer surface disposed between the
top and bottom ends. In addition, the plug includes at least one
cap disposed at an end of the body, with the body and at least one
cap being formed from bone. In some embodiments, the body and cap
are integrally formed. The body and cap may be formed from a
section of a long bone taken transverse to a long axis of the long
bone, with the body including a through-hole formed by a canal in
the long bone. In another embodiment, the body may be formed of
cancellous bone and the cap may be formed of cortical bone.
[0022] The present invention further relates to a method for
filling a vacancy in bone, including: inserting a filler into a
portion of the vacancy, the filler comprising at least one of bone
chips, bone particulate, bone fibers, bone-growth materials,
hydroxyapatite, metal, resorbable material, polymer, ceramic, and
bone cement; and fitting a cap to the vacancy to seal the filler
therein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Preferred features of the present invention are disclosed in
the accompanying drawings, wherein similar reference characters
denote similar elements throughout the several views, and
wherein:
[0024] FIGS. 1A and 1B show perspective views of embodiments of
plugs according to the present invention;
[0025] FIGS. 1C to 1G show exploded, perspective views of
additional embodiments of plugs according to the present
invention;
[0026] FIG. 1H shows a perspective view of another embodiment of a
plug according to the present invention;
[0027] FIGS. 1I to 1J show exploded, perspective views of
additional embodiments of plugs according to the present
invention;
[0028] FIGS. 2A to 2H show perspective views of embodiments of caps
according to the present invention;
[0029] FIG. 3A shows a side view of a sleeve for a plug according
to the present invention;
[0030] FIG. 3B shows a cross-section of the sleeve of FIG. 3A
through line IIIB-IIIB;
[0031] FIG. 3C shows a cross-section of the sleeve of FIG. 3A
through line IIIC-IIIC;
[0032] FIG. 3D shows a perspective view of a cap according to the
present invention;
[0033] FIG. 3E shows a bottom view of the cap of FIG. 3D;
[0034] FIG. 3F shows a side view of the cap of FIG. 3D;
[0035] FIG. 3G shows a perspective view of the sleeve of FIG.
3A;
[0036] FIGS. 3H to 3J show the installation of the cap of FIG. 3D
on the sleeve of FIG. 3G;
[0037] FIGS. 3K and 3L show perspective views of fillers according
to the present invention;
[0038] FIG. 3M shows a side view of a plug according to the present
invention with a filler formed from a femoral head;
[0039] FIG. 3N shows another embodiment of a sleeve for a plug
according to the present invention with threading;
[0040] FIGS. 4A to 4C show a top view, side view, and another side
view, respectively, of an additional embodiment of a cap according
to the present invention;
[0041] FIG. 4D shows a side view of the cap of FIG. 4A installed in
a sleeve of a plug according to the present invention;
[0042] FIG. 4E shows a cross-section of the cap of FIG. 4A through
line IVE-IVE;
[0043] FIG. 4F shows a bottom view of a cap with a locking portion
having serrated edges according to the present invention;
[0044] FIG. 4G shows a perspective view of a sleeve with recesses
on the outer surface for a plug formed according to the present
invention;
[0045] FIG. 5A shows a side view of an additional embodiment of a
sleeve for a plug with fingers according to the present
invention;
[0046] FIG. 5B shows a cross-section of the sleeve of FIG. 5A
through line VB-VB;
[0047] FIG. 5C shows a cross-section of the sleeve of FIG. 5A
through line VC-VC;
[0048] FIGS. 5D and 5E show top and side views, respectively, of an
additional embodiment of a cap for a plug according to the present
invention;
[0049] FIG. 6A shows a perspective view of an additional embodiment
of a plug according to the present invention;
[0050] FIG. 6B shows an exploded, perspective view of another
embodiment of a plug according to the present invention;
[0051] FIGS. 7A and 7B show the forming of a cancellous plug
between a pair of dies according to the present invention;
[0052] FIG. 8A shows a side view of another plug according to the
present invention;
[0053] FIG. 8B shows a side view of the plug of FIG. 8A;
[0054] FIG. 9A shows a side view of another plug according to the
present invention;
[0055] FIG. 9B shows a side view of the plug of FIG. 9A;
[0056] FIG. 10A shows a side view of another plug according to the
present invention;
[0057] FIG. 10B shows a side view of the plug of FIG. 10A;
[0058] FIG. 11A shows a side view of another plug according to the
present invention;
[0059] FIG. 11B shows a side view of the plug of FIG. 11A;
[0060] FIG. 12 shows a side view of yet another plug according to
the present invention;
[0061] FIG. 13 shows a side view in cross-section of another plug
according to the present invention;
[0062] FIG. 14A shows a side view in cross-section of another plug
according to the present invention;
[0063] FIG. 14B shows a side view of the plug of FIG. 14A;
[0064] FIG. 15A shows a side view in cross-section of another plug
according to the present invention;
[0065] FIG. 15B shows a side view of the plug of FIG. 15A;
[0066] FIGS. 16 to 25 show side views in cross-section of
additional embodiments of plugs according to the present
invention;
[0067] FIGS. 26 and 27 show exploded perspective views of
additional plugs according to the present invention;
[0068] FIGS. 28 and 29 show perspective views of insertable
components for use with plugs according to the present
invention.
[0069] FIG. 30A shows a side view in cross-section of another plug
according to the present invention;
[0070] FIG. 30B shows a perspective view of the sleeve of FIG.
30A;
[0071] FIGS. 30C and 30D show a side view and bottom view,
respectively, of the end cap of FIG. 30A;
[0072] FIGS. 31A and 31B show the formation of a plug from a
cross-section of a bone taken transverse to the long axis of a
bone; and
[0073] FIGS. 32A and 32B show partial cross-sections of a long bone
and a vertebral body, respectively, with a bone plug inserted
therein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0074] Any of a wide variety of different implant structures,
particularly allograft, autograft, and/or xenograft implant
structures can be prepared according to the teachings of the
present invention. While a representative selection of implant
structures are described and depicted herein, additional disclosure
is found in U.S. Provisional Application No. 60/191,099 filed Mar.
22, 2000, which is hereby incorporated herein in its entirety by
reference, including all figures.
[0075] As used in the description of the present invention, the
words fitting, interfitting, mating, locking, interlocking,
meshing, and interlacing are all used generically to describe the
joining of bone sections or pieces together. Thus, these words are
not limited to the use of any particular manner of joining. Thus,
for example, the press-fitting of one bone section within a cavity
formed in another bone section may be described using any of the
above-mentioned terms. In addition, although various preferred
mechanical fastening approaches are described, the present
invention allows the use of any mechanical device for joining two
or more separate parts of an article or structure. Such mechanical
devices include, but are not limited to the following: screws,
keys, pins, pegs, rivets, cotters, nails, spikes, bolts, studs,
staples, bosses, clamps, clips, dowels, stakes, hooks, anchors,
ties, bands, and crimps. Also, bonding agents or other chemical
means for joining two separate parts may be employed alone or in
combination with the mechanical devices. Thus, as appropriate, the
means disclosed herein for fixing bone sections to each other may
be substituted, as with the above-mentioned mechanical devices,
bonding devices, or chemical means. Furthermore, although
particular types of joints are disclosed, the present invention is
directed to the creation of implants that may be joined using other
joints.
[0076] While the present invention is preferably directed to the
creation of implants from allograft material, the present invention
may also be applied to implants that utilize other materials,
including but not limited to the following: xenograft, autograft,
metals, alloys, ceramics, polymers, composites, and encapsulated
fluids or gels. Furthermore, the implants described herein may be
formed of materials with varying levels of porosity, such as by
combined bone sections from different bones or different types of
tissue having varying levels of porosity.
[0077] Also, the implants described herein may be formed of bone
materials with varying mineral content. For example, cancellous or
cortical bone may be provided in natural, partially demineralized,
or demineralized states. Demineralization is typically achieved
with a variety of chemical processing techniques, including the use
of an acid such as hydrochloric acid, chelating agents,
electrolysis or other treatments. The demineralization treatment
removes the minerals contained in the natural bone, leaving
collagen fibers with bone growth factors including bone morphogenic
protein (BMP). Variation in the mechanical properties of bone
sections is obtainable through demineralization. Advantageously,
use of a demineralizing agent on natural bone transforms the
properties of the bone from a stiff structure to a relatively
pliable structure when hydrated. Some portions of interfitting bone
components may be demineralized or partially demineralized in order
to achieve improved interfitting. For example, a tissue form may
include two bone components having portions that are coupled
together with an interference fit. The interference fit may be
enhanced if the surface region of one or more of the components is
demineralized or partially demineralized so that it is pliable and
exhibits some elasticity and/or malleability when hydrated.
[0078] In addition, while many of the embodiments described herein
show bone components disposed at right angles, or joints formed
with right angles, angles that are greater or less than ninety
degrees may alternatively be used in implants of the present
development.
[0079] The components that are used to create implants of the
present invention may all be formed from cortical bone, all from
cancellous bone, or a combination of components formed from
cortical and cancellous bone. The interfitting of the components
may be achieved through a variety of means, including but not
limited to the following: pinning, bonding with a suitable bone
bonding agent or chemical means, press fitting, threadably engaging
(as by helically screwing one component into another), inserting a
tapered component into a component with a matching inner surface,
twist-locking, or other interlocking means such as will be
described in other embodiments. While the present development
preferably allows the creation of implants from all bone material,
it is also anticipated that one or more components used to create
the implants may be formed of non-bone material such as a synthetic
or other material. Thus, while the implants disclosed herein are
typically described as being formed primarily from bone, the
implants alternatively may be formed in whole or in part from other
materials such as hydroxyapatite, metal, resorbable material,
polymer, and ceramic, and may additionally incorporate bone chips,
bone particulate, bone fibers, bone growth materials, and bone
cement. Also, while solid, cylindrical sleeve-like structures are
described herein, the sleeves optionally may include perforations
extending from outer to inner surfaces, or recesses formed in outer
surfaces that do not extend through inner surfaces. Geometries such
as circular depressions, dimples formed from a spherical geometry,
diamond shapes, or rectangular shapes may be used.
[0080] Bones suitable for forming implants of the present invention
include a radius, humerus, tibia, femur, fibula, or ulna, although
other bones may be used.
[0081] The moisture content of the bone sections also may be varied
to advantageously permit improved interlocking. Bone components
initially may be provided with moisture content as follows: (1)
bone in the natural state fresh out of the donor without freezing,
(2) bone in the frozen state, typically at -40.degree. C., with
moisture content intact, (3) bone with moisture removed such as
freeze-dried bone, and (4) bone in the hydrated state, such as when
submersed in water. Using the expansion and contraction properties
that can be obtained during heating and cooling of the bone
material, and the concomitant resorption of moisture along with
swelling for some bone material, permits an alternate approach to
achieving a tight press-fit.
[0082] Turning to FIGS. 1A to 1J, tissue forms are shown in the
shape of plugs suitable for implantation. Plugs may be created
using a core drill or trephine system, or may be machined or
otherwise formed from bone. For example, using a trephine system,
essentially a dowel cutter for use with tissues, a cylindrical
shaped plug may be cut in vivo from a tissue, such as a vertebral
body or tissue from another location such as the hip. This material
may be used as an autograft, which may serve as a plug to fill an
anatomical defect or instead may serve as a strut to be inserted
into another implant formed of bone to provide additional strength.
A similarly sized plug of allograft material may be used to fill
the hole created by the removal of autograft material. The plugs
contemplated by the present invention, however, may be made of
allograft or xenograft bone material as well, or combinations of
autograft, allograft, and xenograft bone material. The plugs may
also be formed from cancellous bone, cortical bone, or combinations
thereof and the choice of such materials may be based on the
materials properties obtainable from a given type of bone. For
example, cancellous bone is available in a range of porosities
based on the location in the body from which the bone is harvested.
Extremely porous cancellous bone may be harvested from various
areas such as the iliac crest, while less porous bone may be
harvested from areas such as a tibial condyle. Thus, the materials
properties--particularly the porosity--of the plugs may be selected
to meet the needs of a given application. In addition, the plugs of
the present invention may be formed either partially or completely
using non-bone materials such as metals, alloys, ceramics,
polymers, composites, and encapsulated fluids or gels.
[0083] Turning to the various embodiments of plugs according to the
present invention, it should be noted that the plugs discloses
herein may be of unitary construction, or may be formed from
multiple pieces that are interfitted together. Thus, while the
figures may show cross-sections of plugs or plugs formed with
multiple pieces to produce a particular structure, it should be
noted that the structures instead may be one-piece. In addition,
although the plugs are generally described herein as being formed
from bone or at least in part from bone, the plugs may additionally
be formed completely from non-bone materials such as metals or
ceramics. Also, while dimensions are indicated herein for plugs, it
should be noted that much smaller plugs as well as much larger
plugs also are contemplated following the general structures
disclosed herein.
[0084] As shown in FIG. 1A, a cylindrical plug 10 according to the
present invention includes a central region 12 and end caps 14, 16.
Preferably, central region 12 is formed of cancellous bone
material, while caps 14, 16 are formed of cortical bone material.
Cortical bone material is placed at the ends of plug 10 due to its
superior mechanical strength and lower porosity as compared to
cancellous bone material. In alternate embodiments, central region
12 and end caps 14, 16 may be formed from other types of bone and
or non-bone materials to suit a particular need.
[0085] Other embodiments of plugs according to the present
invention are shown in FIGS. 1B to 1J. Plug 20 includes a body 22
and single end cap 24. Plug 30 is formed of two sections of bone
32, 34 that are interfitted together. Ribbing 36 may be provided
along the length of plug 20, and a keyhole 38 may be provided at a
head 39. Keyhole 38 preferably is sized to receive a screwdriver,
or other suitable device, to facilitate the installation of plug 30
in an anatomical region. Alternate forms of keyhole 38 include
recesses shaped in the form of a cruciform, hex, star, recess, or
clover. In another embodiment, a tapered, conical shaped plug 40
may be formed from bone material. Plug 40 may be formed from a
single piece of bone, or it may be formed of two or more pieces of
bone that are interfitted together as shown for example with
sections 42, 44. Similarly, a bullet shaped plug 50 with a blunt
tip 52 may be formed from bone sections 54, 56.
[0086] A plug 60 as shown in FIG. 1F is formed of bone sections 62,
64 that are interfitted together, and further includes threading 66
that is machined on the plug. A plug 70, also formed for example
from two bone sections 72, 74 includes migration-resistance
protrusions such as spurs or teeth 76 disposed around the
circumference of the plug. Alternatively, a plug 70 could be formed
from a single piece of bone or other material such as metal or
ceramic.
[0087] A plug 80 with an oversized head 82 and a shaft 84 is shown
in FIG. 1H. As previously discussed with respect to embodiments
with end caps, head 82 may be formed of cortical bone while shaft
84 may be formed of cancellous bone. Although plug 80 may be
machined from one piece of bone, head 82 and shaft 84 may be
separate bone pieces that are interfitted together. Similarly, plug
80 may incorporate non-bone material. Other designs of plugs
include a plug 90 formed from two bone sections 92, 94 that are
interfitted together along a longitudinal axis extending through
the free ends of the sections, and plug 100 formed from bone
sections 102, 104 that are interfitted together at one free end of
each section. Alternate embodiments contemplated by the present
invention include plugs formed of non-symmetrical bone sections,
plugs formed from one piece of bone, and plugs formed from more
than two pieces of bone with the sections joined together using
joints, fasteners, or other techniques described above. In
addition, the plugs may be formed using metal, resorbable material,
plastic, or ceramic, as well as the various types of bone with
various degrees of porosity as previously described. Plug may
include sections of cortical bone, cancellous bone, metals
ceramics, or other materials.
[0088] In some circumstances it is desirable not to fill an entire
defect or vacant region in a bone with a single plug. For example,
other material such as bone chips, slurries of bone particulate,
bone fibers, bone-growth inducing substances, bone cement, or
polymers may be inserted into the defect or vacancy, and sealed
therein using a cap. Various forms of caps suitable for this
purpose are shown in FIGS. 2A-2H. The caps may be created using
allograft tissue. In alternate embodiments, the caps may be formed
using metal, resorbable material, plastic, ceramic, autograft, or
xenograft. The cap 110 shown in FIG. 2A includes a rounded head 112
and a body 114 which may be press-fit into a vacancy in bone, while
cap 120 includes a flat head 122 and a body 124. Cap 130, shown in
FIG. 2C, includes a cap 132, body 134, and migration-resistant
protrusions 136, while cap 140 includes a head 142, body 144, and
flange area 146 that functions similar to circumferentially
distributed teeth. Another cap of the present invention, cap 150,
includes a head 152 and a tapered body 154. A through-hole 156 may
also be provided, for example, to permit a needle to gain access to
the vacancy sealed by the cap. Such a hole may permit delivery of
substances after the cap has been installed, or permit expansion of
the cap as by inserting a component therein.
[0089] Cap 160, shown in FIG. 2F, includes a flat, circular head
162 and a generally rectangular body 164. Notably, the faces of
body 164 meet to create four longitudinal radiused portions 166.
When cap 160 is inserted in a suitably sized vacancy, the four
radiused portions 166 provide four regions of contact with the
walls of the vacancy. Such a construction facilitates press-fitting
in the vacancy; a press-fit of a cap body that is closely shaped to
conform to the walls of a defect may be difficult to achieve due to
the tightness inherent in the fit itself. A less tight fit, as
provided for example by body 164, may permit a press-fit to be
achieved with less difficulty. While a press-fit with four radiused
portions 166 of contact has been described, it is also contemplated
that press-fits with other amounts of contact may be used.
[0090] Several additional embodiments of caps are shown in FIGS. 2G
and 2H. Cap 170 includes a head 172 and a body 174 with threading
176. Cap 180 includes a head 182 and a body 184. A slit 186 extends
about halfway through head 182 and body 184. Slit 186 allows cap
180 to be compressed when inserted in a vacancy; after insertion,
the cap may re-expand to more closely fit against the walls of the
vacancy. Also, cap 180 may be inserted into a vacancy and expanded
using a wedge or pin that is subsequently inserted into slit
186.
[0091] Referring initially to FIGS. 3A to 3C, a preferred
embodiment of a plug according to the present invention is shown.
Plug 200 includes a sleeve 202 with open, free ends 204, 206. Holes
208 extend from outer wall 210 to inner wall 212. Preferably, holes
208 are arranged in rows centered about parallel planes with
respect to each other, around the circumference of plug 200. A slot
214 is disposed at a free end 204 and a circumferential groove 216
is cut into inner surface 212 proximate free end 204. A central
axis 218 is disposed longitudinally about the center of plug 200,
and preferably inner and outer diameters D.sub.1, D.sub.2,
respectively, of plug 200 are generally constant, but may be
tapered. In the preferred embodiment, holes 208 are offset by a
generally constant angle .theta..sub.1 with respect to each other,
as measured from center 220 defined along axis 218. Preferably,
angle .theta..sub.1 is between about 35.degree. and about
55.degree. and more preferably about 45.degree.. In a preferred
embodiment, plug 200 has an inner diameter D.sub.1 of between about
1.2 cm and 1.4 cm, an outer diameter D.sub.2 of between about 1.5
cm and 1.7 cm, and a length L, of between about 1.6 cm and 2.0 cm.
More preferably, inner diameter D.sub.1, outer diameter D.sub.2,
and length L, are about 1.3 cm, 1.6 cm, and 1.9 cm, respectively.
Holes 208 are preferably circular and have a diameter of between
about 0.2 cm and about 0.5 cm, and more preferably about 0.35 cm.
In alternate embodiments, holes 208 may be in other shapes such as
elliptical or oblong geometries; the number of holes 208 as well as
the alignment of holes 208 with respect to each other may be
varied.
[0092] As shown in FIGS. 3D to 3F, a cap 222 suitable for coupling
to sleeve 202 includes a top surface 224 and a bottom surface 226.
A locking portion 228 preferably is integrally formed on bottom
surface 226, and includes narrow and wide portions 230, 232,
respectively, which are symmetrical about central line 233. The
outer edges of narrow and wide portions 230, 232 are preferably
disposed along the circumference of a circle centered about point
234 along central axis 236 of cap 222, with the diameter of the
circle being smaller than that of outer diameter D.sub.2 of sleeve
202. In particular, as shown in FIG. 3F, locking portion 228 of cap
222 includes a lip 236 and a wall 238. Preferably, outer diameter
D.sub.4 of cap 222 is about the same as outer diameter D.sub.2 of
sleeve 202, lip 236 of cap 222 has an outer diameter D.sub.3 sized
to fit and turn within groove 216 in sleeve 202, while wall 238 has
an outer diameter D.sub.2 sized to fit and turn proximate inner
surface 212 of sleeve 202. In addition, locking portion 228
preferably tapers from wide portion 232 to narrow portion 230 along
a radius of curvature R.sub.1 of between about 0.5 cm and 1.1 cm,
and more preferably 0.8 cm. Preferably, the overall thickness
L.sub.2 of cap 222 is between about 0.2 cm and about 0.5 cm.
[0093] Referring to FIGS. 3G to 3J, free end 204 of sleeve 202
preferably is closed using a cap 222. Cap 222 is coupled to sleeve
202 by first placing cap 222 with wide portion 232 of locking
portion 228 centrally disposed within free end 204 of sleeve 202
and narrow portion 230 of locking portion 228 disposed in slot 214
of sleeve 202. In this position, central line 233 of cap 222 is
aligned with central line 240 extending along a diameter of sleeve
202, centrally through slot 214. With lip 236 of cap 222 disposed
in groove 216 of sleeve 202, cap 222 is securely coupled to sleeve
202 by rotating cap 222 in the direction of arrow A, such that
lines 233, 240 of cap 222 and sleeve 202, respectively, are no
longer colinear. In some embodiments, groove 216 is interrupted to
create a stop (not shown), as for example located at region 242,
thereby preventing additional rotation of cap 222.
[0094] With a cap 222 installed on sleeve 202, plug 200 includes a
chamber 244 with one end open. This chamber 244 may be packed with
such materials as bone chips, slurries of bone particulate, bone
fibers, bone-growth inducing substances, hydroxyapatite, polymers
such as polymethylmethacrylate, ceramics, bone cement, or other
materials. In a preferred embodiment, sleeve 202 and cap 222 are
formed of cortical bone, and chamber 244 is packed with a cylinder
246 that is preferably formed of cancellous bone and inserted prior
to installation of cap 222. Alternatively, other materials such as
porous ceramics may be used. Holes 208 facilitate incorporation of
plug 200 into surrounding bone tissue, by permitting ingrowth as
well as access to materials retained in chamber 244. If a solid
cylinder 246 having a diameter of about D.sub.1 is inserted into
chamber 244, the cylinder may be prevented from removal through
free end 206 by a circumferential lip 245. Thus, an end cap is not
required at free end 206 to retain cylinder 246. The cortical bone
may be obtained from the thin cortical bone proximate the ends of
long bones, such as the humerus or tibia, or other regions. A
sleeve 202 and cap 222 formed of cortical bone provide structural
integrity to plug 200, and advantageously the cortical bone is
readily machinable to repeatable dimensions and desirable
tolerances. In an alternate embodiment, cylinder 246 may be formed
of a main cancellous body portion 248 and a cortical end cap 250,
with cortical end cap 250 disposed in a free end of sleeve 202 such
that both free ends are closed by cortical bone for added
structural integrity. In another alternate embodiment, cylinder 246
may be used as a plug. Although cylinder 246 is shown as a
one-piece component, cylinder 246 alternately may be formed of two
or more portions, for example, by sectioning cylinder 246 along
lines 247, 248. A sectioned cylinder 246 may loosely fit in a
sleeve, with the sectioning permitting expansion of the cylinder
portions or contraction of the sleeve without creating significant
stress on the components.
[0095] When plug 200 is inserted into an anatomical vacancy,
preferably open free end 206 is inserted first such that cortical
cap 222 faces outward. Other materials may be used to form plug
200, such as metals or ceramics. To facilitate insertion of plug
200, the circumferential edge 252 proximate free end 206 preferably
is chamfered to assist in guiding plug 200 into the vacancy.
[0096] In an alternate embodiment, a plug 260 includes a
cylindrical, cortical shell 262 and a filler 264. Preferably,
filler 264 is harvested from a femoral head, and thus naturally
includes integral cancellous and cortical bone portions 266, 268,
respectively. The natural geometry of cortical bone portion 268 is
curved or otherwise variable at free end 270, and a flat free end
270 is not necessary to provide sufficient structural integrity. In
one embodiment, filler 264 may be harvested from a femoral head,
although it is difficult to obtain a natural, uniformly thick
cortical bone portion 268. Preferably, the distance L.sub.3 from a
free end of cortical shell 262 to a hole 272 is chosen so that
cortical bone portion 268 does not intersect any holes 272, and
filler 264 may then prevent the release of blood or other fluids
from within the plug or vacancy in which it is inserted.
Optionally, a cortical cap may be disposed proximate free end 270;
cortical bone portion 268 of filler 264 may serve as a redundant
cortical sealing for plug 260 should the cap become detached.
[0097] Another alternate embodiment of a plug 280 includes a shell
or sleeve 282 with holes 284 and threading 286 on outer surface
288. Plug 280 is thus configured to be threadably received in an
anatomical vacancy in bone tissue. Threading on the inner surface
of plug 280 also may be provided.
[0098] Another embodiment of a cortical cap suitable for the
present invention is shown initially in FIGS. 4A to 4C. Cap 290
includes a top surface 292 and a bottom surface 294. A locking
portion 296 preferably is integrally formed on bottom surface 294,
and is symmetrical about central lines 298, 300. The outer edges
302, 304 of locking portion 296 are preferably disposed along the
circumference of a circle centered about point 306 along central
axis 308 of cap 290. As shown in FIG. 4C, locking portion 296 of
cap 290 includes a lip 310 and a wall 312. As discussed with
respect to cap 222, lip 310 of cap 290 is sized to fit and turn
within groove 216 in sleeve 202, while wall 312 is sized to fit and
turn proximate inner surface 212 of sleeve 202. A cap 290 may be
coupled to a sleeve 202, preferably by snap-fitting of lip 310 of
cap 290 in groove 216 of sleeve 202, as shown in FIGS. 4D and 4E.
The snap-fitting of cap 290 to sleeve 202 obviates the need for a
slot 214 in sleeve 202. The hole pattern of sleeve 202 may be
varied, and different hole patterns are shown in FIGS. 3A and 4D.
Alternate embodiments of cap 290 may include serrations, ribbing,
scoring, or other undulating features on edges 302, 304 of locking
portion 296, such as ribs 307 shown in FIG. 4F. Alternatively, such
ribs may be oriented in a plane perpendicular to line 308,
following the curvature of edges 302, 304, as shown in FIG. 4B.
Ribs 307 may be used to lower tolerances between edges 302, 304 and
receiving surfaces on a sleeve. Additionally, the grooving in a
sleeve for receives edges 302, 304 may be provided with similar
undulating features for positive interlocking.
[0099] An alternate sleeve 314 for use in a plug is shown in FIG.
4G. Sleeve 314 includes recesses 315 formed in outer surface 316.
Recesses 315 do not extend through inner surface 317. Although
recesses 316 are shown in the shape of circular depressions, the
recesses may be other shapes such as dimples formed from a
spherical geometry, diamond shapes, or rectangular shapes.
[0100] A further embodiment of a plug is shown in FIGS. 5A to 5C.
Plug 320 includes a sleeve 322 with holes 324 and elongate slots
326 extending from free end 328 toward free end 330. Due to the
positioning of slots 326, fingers 327 are formed. Advantageously,
fingers 327 provide flexibility at free end 328, thus facilitating
the snap-fitting of a cap on free end 328. Preferably, holes 324
are disposed in aligned groups, such as along line 332. A
circumferential groove 334 is provided to facilitate coupling of a
cap to sleeve 322, as discussed previously. Preferably, holes 324
and grooves 326 are disposed at a generally constant angular
interval .theta..sub.2 with respect to each other, as measured from
the center of sleeve 322 at point 336. Preferably, angle
.theta..sub.2 is between about 35.degree. and about 55.degree. and
more preferably about 45.degree.. Another cap particularly suitable
for use with plug 320 is cap 338, shown in FIGS. 5D and SE. Cap 338
includes a top surface 340 and a bottom surface 342. A locking
portion 344 preferably is integrally formed on bottom surface 342,
and is circular. The outer edge 346 of locking portion 344 is
disposed along the circumference of a circle centered about point
348, formed at the intersection of diameters 350, 352. Referring to
FIG. 5E, locking portion 344 of cap 338 includes a lip 354 and a
wall 356. As discussed with respect to other embodiments of caps,
lip 354 of cap 338 is sized to fit within groove 334 in sleeve 322,
while wall 356 is sized to fit proximate the inner surface of
sleeve 322.
[0101] Caps referred to herein may be coupled to sleeves using a
variety of other structures, including threading, ribs, teeth,
tapers, and knurled surfaces. In addition, the use of adhesive
bonding is also contemplated.
[0102] Although circular, elongate, and irregular protrusions have
been disclosed for use in coupling caps to sleeves, other
configurations of protrusions are also contemplated for use in the
present invention. For example a protrusion with a triangular or
rectangular geometry may be used to provide three or four points of
contact, respectively, with the inner walls of a sleeve. A
cross-shaped protrusion would also provide four regions of contact.
In one embodiment, a rectangular protrusion is provided with a
length that is a factor of three greater than the width.
[0103] With respect to sleeve constructions, multipiece sleeves are
also contemplated. For example, as shown in FIG. 6A, a sleeve 370
may be formed from two portions of bone 372, 374 that are
interfitted together and closed at one end using a cap 376. Another
sleeve 380 is shown in FIG. 6B, and includes a slit 382 extending
from free end 384 to free end 386. Slit 382 is sized such that when
a cylindrical filler is inserted into hollow region 388, sleeve 380
is permitted to flex to accommodate dimensional differences between
the inner diameter of sleeve 380 and the outer diameter of the
filler. Ends 384, 386 may be closed using caps, as discussed
previously, for example with a cap 390. Cap 390 may optionally be
provided with a slit extending from a central point to the outer
diameter of the cap. Sleeve 380 also may be compressed when
inserted in a vacancy, such as in a vertebral body; after
insertion, sleeve 380 may re-expand to more closely fit against the
walls of the vacancy. Also, sleeve 380 may be inserted into a
vacancy and expanded using a wedge or pin that is subsequently
inserted into slit 382.
[0104] With respect to cancellous fillers for sleeves, or plugs
formed of cancellous bone, the cancellous bone may be shaped to a
desired geometry using dies, as shown in FIGS. 7A and 7B. Such a
manufacturing process provides an alternative to turning or
milling, which may be more difficult than pressing for cancellous
bone. A section of cancellous bone 400 is disposed between a pair
of dies 402, 404, which may include particular geometrical features
such as indentations 406, protrusions, or other shapes. Once dies
402, 404 are brought together such that surfaces 408, 410 contact
each other, an oversized bone section 400 is compressed and molded
into the geometry of the dies. As shown in FIG. 7B, compression of
a bone section 400 that is initially smooth and cylindrical in dies
402, 404 results in the formation of ribs 412 about the
circumference of bone section 400 due to the compression of
portions of bone section 400 in indentations 406. Thus, machining
of such cancellous bone fillers may be avoided.
[0105] Advantageously, plugs formed of cancellous bone may be
attached to syringes or aspirators, and blood or other fluids such
as bone-growth inducing substances may be drawn into the plugs. The
use of mechanically applied pressure, such as with aspiration
devices, permits a greater degree of fluid absorption and/or
concentration to be achieved than otherwise readily obtainable by
soaking bone in such fluids without applying pressure from a
device. In embodiments of the present invention that include hollow
regions, a bone component of cancellous bone formed using the
aforementioned technique may be inserted therein.
[0106] Other embodiments of plugs according to the present
invention in the form of dowels are shown in FIGS. 8 to 15. Plugs
described and depicted as sleeves alternatively may be formed as
solid plugs with the outer contours shown in the figures. In the
preferred embodiments, the plugs are generally cylindrical. Turning
to FIG. 8A, a plug 500 includes a sleeve or solid portion 510
formed of a single piece of bone. Grooved regions 504 are provided
proximate free end 506, and preferably include angled edges 510
disposed at an angle .theta..sub.3 with respect to outer surface
512. Preferably, angle .theta..sub.3 is between about 20.degree.
and about 40.degree., and more preferably about 30.degree..
Preferably, plug 500 has an overall length L.sub.3 of between about
1.7 cm to about 2.3 cm, and more preferably about 2.0 cm, while the
outer diameter D.sub.5 is between about 1.4 cm and about 1.8 cm,
and more preferably about 1.6 cm. In one embodiment, plug 500 is
formed from bone harvested from a condyle. Thus, bone proximate
free end 508 may be cortical, while the remainder of plug 500 is
formed of cancellous bone. As shown in the side view of FIG. 8B,
free end 506 of sleeve portion 510 has a circular wall 514 with a
chamfer 511 to facilitate insertion of plug 500 into a vacancy.
Similarly, a plug 520 shown in FIGS. 9A and 9B is formed of a
sleeve or solid portion 522 with flutes 524 disposed about the
outer surface 526 of portion 522 proximate a free end 528, as
partially indicated in phantom. If plugs 500, 520 are formed as
sleeves, central chambers 516, 529, respectively are formed
therein. Additional forms of fluting for similarly dimensioned
plugs are shown in FIGS. 10 to 11. Plugs 530, 540 include flutes
532, 542 respectively. Side views from ends 534, 544 of plugs 530,
540, respectively, are shown in FIGS. 10B and 11B.
[0107] Further embodiments of plugs according to the present
invention are contemplated. Plug 550, shown in side view in FIG.
12, includes a sleeve 552 with a chamfered end 554. As shown in
FIG. 13 in cross-section, a generally cylindrical plug 560 includes
cortical end caps 562, 564 disposed at the ends of a cancellous
sleeve 566. End cap 564 includes chamfered edges 568. A central
chamber 570 is also formed, and may be filled with a cylindrical
element 572 formed of cortical bone in the shape of a pin to
improve structural integrity. Preferably, element 572 is press-fit
within sleeve 566 and end caps 562, 564. Similarly, as shown in
FIGS. 14A and 14B, plug 580 includes an oversized end cap 582,
while shown in FIGS. 15A and 15B is a plug 590 with an oversized
end cap 592. The components of plugs 560, 580, 590 may be may be
held together using ribbing, keys, pins, or other features as
described previously with respect to other embodiments.
[0108] Additional embodiments of generally cylindrical plugs
according to the present invention are shown in cross-section in
FIGS. 16-25. Turning to FIG. 16, plug 600 includes a cortical
sleeve 602 with through-holes 604, cortical end caps 606, 608, and
a chamber 609 with a cancellous central filler 610 disposed
therein. In an alternate embodiment, because end caps 606, 608
create a chamber 609, plug 600 may be filled with other materials
such as bone chips. End caps 606, 608 may be press-fit or snapped
within sleeve 602. Plug 620, as shown in FIG. 17, includes a
cortical cap 622 and a cancellous body 624, which together form a
central, substantially right cylindrical chamber 626. Plug 630,
shown in FIG. 18, includes a cortical cap 632 with a central
through-hole 634, aligned with a cancellous sleeve 636 with a
central through-hole 638. Holes 634, 638 are aligned such that a
suitably sized pin 639 extends therethrough. In some embodiments,
holes 634, 638 form a tapered hole such that a generally
frustoconical chamber is formed for receiving a like-shaped filler
such as a cancellous bone filler.
[0109] As shown in FIG. 19, a plug 640 includes a cortical sleeve
642 with a substantially right cylindrical cancellous insert 644;
sleeve 642 is closed at one end with a cortical end cap 646. Plug
650 includes a cortical end cap 652 that is threadably received in
a cancellous body 654. A chamfer 656 is provided at face 658,
opposite end cap 652, to assist in guiding the insertion of plug
650 into a vacancy. A plug 660 includes a cortical end cap 662 and
a cancellous body 664. A cortical insert 666 extends through end
cap 552 and partway through body 664. Insert 666 is fixed to body
664 with a pin 668 which extends through body 664 and insert 666.
Pin 668 is shown extending generally perpendicular to the plane of
the page. In the embodiment shown in FIG. 22, plug 670 includes a
cap 672 that press fits to sleeve 674 along both the outer and
inner surfaces 676, 678, respectively. Optionally cap 672 may be
pinned in place with a pin 679 extending through both cap 672 and
sleeve 674. Additionally, as shown in FIG. 23, a plug 680 includes
a cortical cap 682 that is locked within sleeve 684 by a cancellous
insert 686. Components 682, 686 may instead be integral, formed for
example by machining a potion of bone harvested from a femoral
head, as described previously with respect to plug 260. A pin 688
further constrains movement of cancellous insert 686. In yet
another embodiment, a sleeve 692 of plug 690 is provided with a
dovetail-shaped through-slot 694 at one end so that a cap 696 may
be coupled to sleeve 692 by sliding dovetail portion 698 within
slot 694 from either end of the slot. Also, a plug 700 may be
formed by press-fitting or loosely fitting a cortical cap 702 to a
cancellous body 704 and further coupling cap 702 to body 704 with a
pin 706 as shown in FIG. 25.
[0110] Turning to FIG. 26, plug 710 includes a body 712 with a
protrusion 714 having slots 716. When a cap 718 with a central hole
720 is placed around protrusion 714, the protrusion may contract so
that the width of slots 716 decreases, thereby providing a tighter
fit of cap 718 to an oversized protrusion 714.
[0111] Another plug 730 according to the present invention is shown
in exploded perspective view in FIG. 27. Washer-like end caps 732,
734 include central holes 736, 738, respectively, for receiving a
central member 740. Preferably, end caps 732, 734 and central
member 740 are formed of cortical bone. Member 740 also passes
through a central hole in body 742, extending beyond each free end
744, 746 thereof, such that holes 736, 738 receive portions of
member 740. Preferably, member 740 includes interlocking features
at free ends 746, 748 to facilitate coupling. Such features may
include a taper, ribs, threads, saw teeth, flanges, or knurls. In
one embodiment, shown in exploded perspective view in FIG. 28, a
member 750 suitable for use with plug 730 includes a slotted
portion 752 and an insertable wedge-shaped portion 754. Rod 750 is
initially disposed in an end cap hole such as hole 736, without
wedge-shaped portion 754. Rod 750 is locked in place to end cap 732
by inserting wedge-shaped portion 754 in slot 752 and thus
increasing the effective diameter of rod 750 so that a press-fit
within hole 736 is achieved. Similarly, a press-fit may be achieved
using a member 760 with a bulging end 762, as shown in the
perspective view of FIG. 29. Insertion of bulging end 762 in a hole
736, for example, provides a fit such that member 760 may be
coupled to end cap 732. Such a member 760 may be in the form of a
button snap mechanical fastener.
[0112] Yet another plug 770 according to the present invention is
shown in FIGS. 30A to 30D. As shown in the cross-sectional side
view of FIG. 30A, plug 770 includes end cap 772, tapered sleeve
774, and tapered insert 776 sized to fit in sleeve 774. A pair of
L-shaped recesses 776 are disposed proximate end 778, as shown in
the perspective view of FIG. 30B. As shown in side view in FIG. 30C
and bottom view in FIG. 30D, end cap 772 includes head 780 and
shaft 782. A pair of opposing protrusions 784 are disposed on shaft
782. Protrusions 784 are located and sized on shaft 782 such that
end cap 772 may be inserted onto end 778 of sleeve 774 with
protrusions 784 fitting in L-shaped recesses 776. To fix end cap
772 to sleeve 774, end cap 772 is turned so that protrusions 784
abut edges 786 of recesses 776.
[0113] Referring now to FIG. 31A, a section 800 of a long bone such
as a humerus is shown. Although the particular geometry of the
inside and outside of the bone is shown as being generally
cylindrical for exemplary purposes, a plug formed from section 800
in part may follow the natural outer and inner geometry of section
800. Bone 800 includes a canal 802. A generally cylindrical plug
804, taken transverse to the long axis of a bone, may be removed
from bone section 800 and may be used to form a plug 806. Plug 806
includes free ends 808, 810. When initially removed from bone
section 800, free ends 808, 810 are both closed. A cavity 811 may
be bored into a free end 808, 810. Preferably, cavity 811 is
disposed about axis 812, which is generally perpendicular to axis
814 of through-hole 816 formed by canal 802. Thus, cavity 811 is
bounded by an open free end 808 and closed free end 810, forming a
sleeve. Plug 806 may be filled with materials such as bone chips,
bone particulate, bone fibers, bone growth materials,
hydroxyapatite, metal, resorbable material, polymer, ceramic, and
bone cement. Preferably, perforations 818 are formed in plug 806. A
cap (not shown) also may be fixed to free end 808. Preferably,
alignment indicia 820 is provided such as a line extending from
free end 808 to free end 810 and across through-hole 816. Free end
810, which is closed, also may include indicia. Such indicia may
facilitate positioning of plug 806 by a surgeon, particularly with
respect to the orientation of through-hole 816 in the anatomical
vacancy to be filled. In addition, it should be noted that a
section taken through line XXIB-XXIB may create an end cap such as
cap 718 shown in FIG. 26.
[0114] The plugs disclosed in the present invention may be sized to
meet a particular need and applied in areas of bony tissue.
Exemplary use of the plugs described herein is shown in FIGS. 32A
and 32B. A plug 200, for example, may be used in a bone such as a
long bone 900. In addition, a plug 200 may be used in a vertebral
body 910. Plugs 200 are used to fill voids that may exist or be
created in long bone 900 and vertebral body 910 due to trauma,
disease, malformation, or other conditions. Also, the plugs may be
used to fill holes in healthy bone tissue that are surgically
created when healthy tissue is removed for transplantation to other
bony regions of the body.
[0115] The embodiments of plugs disclosed herein may include
components that are initially provided with a first moisture
content, but then allowed to assume a new configuration with a
second moisture content. For example, in the embodiment shown in
FIG. 4E, a cap 290 is used with a sleeve 202. Cap 290 may have a
first outer diameter for lip 310. Freeze-drying of cap 290 results
in shrinkage such that lip 310 assumes a configuration with a
second outer diameter that is smaller than the first outer
diameter. When cap 290 is rehydrated or treated with a swelling
agent, lip 310 of cap 290 may reassume a configuration with the
first outer diameter. Plug 200 initially may be provided with a
freeze-dried cap 290 disposed inside another bone section such as
sleeve 202 so that a loose interference fit is achieved, and
subsequent rehydration of cap 290 in place permits a tighter
interference fit. Notably, the shrinkage and expansion effects may
be used with bone components that have both outer and inner
diameters, such as sleeve 202.
[0116] For example, sleeve 202 initially may be supplied with a
first outer diameter and a first inner diameter, and subsequently
freeze-dried so that sleeve 202 assumes a configuration with a
second outer diameter that is smaller than the first outer
diameter, while having a second inner diameter that is smaller than
the first inner diameter. When sleeve 202 is rehydrated or treated
with a swelling agent, sleeve 202 may reassume a configuration with
the first outer diameter and a first inner diameter. Thus, sleeve
202 may first be provided in dehydrated state to loosely fit in a
void, and rehydrated after insertion to provide a tighter
interference fit between the sleeve and its anatomical
surroundings. Use of these properties also can permit greater
variation in dimensional tolerance between bone sections during
manufacture, while tight final assembly can still be achieved. In
addition, protrusions on bone sections become smaller when
dehydrated, but expand when rehydrated; in contrast, recesses in
bone sections become smaller when hydrated, but larger when
dehydrated. Furthermore, temperature changes may be used to achieve
better interference fits.
[0117] Alignment indicia 285 such as a line along the side of
sleeve 280, as shown in FIG. 3N, may be provided on the outer
surface of the sleeve. Preferably, indicia 285 is an imprint, i.e.
with ink, although indicia 285 may instead be provided in the form
of surface scoring or a protrusion on the surface. In addition to
sleeves, caps may also be provided with indicia to assist in
properly orienting the caps, along with any component coupled
thereto, after insertion into an anatomical void. Also, the indicia
may be used to properly align a plug with a particular body or
sleeve hole configuration to facilitate and guide the release or
exposure of substances contained therein. The indicia suitable for
the present invention includes, but is not limited to, markers such
as lines, arrows, lettering, and symbols.
[0118] Numerous types of joints are useful in the present
development, including joints that permit articulation such as a
ball and socket type of joint, and particularly joints that permit
firm interlocking between two components to prevent relative
movement between the components. Preferably, mortise and tenon
joints can be used to interfit components of the plugs. Other
coupling arrangements such as edge joints including tongue and
groove joints, rabbeted joints, toothed joints, and dovetail joints
are also suitable for the present invention.
[0119] The use of insertable securing elements such as keys, pegs,
pins, wedges, or other suitable components in joints to assist in
securing bone components to each other is also an effective
approach to providing a stable joint. Keys, for example, may be
inserted in notched or grooved areas in plug components, serving as
the securing element between two or more plug components.
Parameters that may be varied when using insertable securing
elements, such as keys, include the angle of application, the
spacing of the elements, and the thicknesses of the elements.
[0120] While various descriptions of the present invention are
described above, it should be understood that the various features
can be used singly or in any combination thereof. The various types
of joints and connections can be used on plugs of different size or
configuration, such that the invention is not to be limited to only
the specifically preferred embodiments depicted in the
drawings.
[0121] Further, it should be understood that variations and
modifications within the spirit and scope of the invention may
occur to those skilled in the art to which the invention pertains.
For example, multiple, differently shaped and sized plugs can be
constructed for interfitting or interconnection to form a multiple
part plug that serves the desired purpose. Accordingly, all
expedient modifications readily attainable by one versed in the art
from the disclosure set forth herein are within the scope and
spirit of the present invention and are to be included as further
embodiments. The scope of the present invention is accordingly
defined as set forth in the appended claims.
* * * * *