U.S. patent application number 10/735449 was filed with the patent office on 2004-07-01 for cranial clamp with torque-limiting feature.
Invention is credited to Davis, Richard Champion III, Duncan, Jeffrey Allen, Lewis, Derek Sean, Roman, Shawn David, Stone, Kevin T..
Application Number | 20040127908 10/735449 |
Document ID | / |
Family ID | 32041737 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040127908 |
Kind Code |
A1 |
Roman, Shawn David ; et
al. |
July 1, 2004 |
Cranial clamp with torque-limiting feature
Abstract
A clamp assembly according to the invention can be fixed through
an opening between adjacent members. The clamp assembly includes a
base, a cap opposing the base, and a post connecting the cap and
the base in a fastening position on the adjacent members. The post
includes a torque-limiting feature to prevent over tightening of
the cap and base. The clamp assembly may further include an applier
interacting with the post to position the cap and base in the
fastening position. A method according to the invention includes
placing the base and cap on opposing internal and external surfaces
of the adjacent members. The post is rotated to bring the base and
cap to the fastening position, and a torque-limiting feature
prevents over tightening. The method may further include removing a
distal portion of the post projecting from the cap and leaving a
proximal portion of the post projecting from the cap and which can
be deformed to secure the base and cap in the fastening
position.
Inventors: |
Roman, Shawn David; (Orange
Park, FL) ; Davis, Richard Champion III; (Hollywood,
FL) ; Duncan, Jeffrey Allen; (Jacksonville, FL)
; Lewis, Derek Sean; (Jacksonville, FL) ; Stone,
Kevin T.; (Winona Lake, IN) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
32041737 |
Appl. No.: |
10/735449 |
Filed: |
December 12, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10735449 |
Dec 12, 2003 |
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10255146 |
Sep 25, 2002 |
|
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6685707 |
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60324658 |
Sep 25, 2001 |
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Current U.S.
Class: |
606/916 ;
606/305; 606/319; 606/324; 606/328; 606/331; 606/908 |
Current CPC
Class: |
Y10S 606/908 20130101;
A61B 2090/037 20160201; A61B 17/688 20130101; A61B 2090/031
20160201; A61B 17/8883 20130101 |
Class at
Publication: |
606/072 ;
606/073 |
International
Class: |
A61B 017/58 |
Claims
What is claimed is:
1. A clamp assembly for repairing a bone defect in a cranium and
operable to fix a bone plate relative the surrounding cranium, each
of the bone plate and surrounding cranium having a near face and a
far face, the clamp assembly comprising: a cap; a base opposing the
cap; a post having an elongate body rotatably attached to the base
and the cap and including a torque-limiting feature, the post
engaging the cap and base to fasten the cap and base relative one
another.
2. The clamp assembly of claim 1, further comprising an applier
operable to rotate the post to position the cap relative to the
base in a fastening position.
3. The clamp assembly of claim 2, wherein the applier is removable
from the post while leaving the cap and base interconnected.
4. The clamp assembly of claim 2, wherein the applier includes a
body having a keyed bore.
5. The clamp assembly of claim 4, wherein the post includes a key
for engaging the keyed bore of the applier.
6. The clamp assembly of claim 1, wherein the post includes
external threads.
7. The clamp assembly of claim 6, wherein the cap includes an
internally threaded collar for mating engagement with the threads
of the post.
8. The clamp assembly of claim 1, wherein the post includes
external ribs.
9. The clamp assembly of claim 8, wherein the cap includes a collar
for ratcheting the cap along the threads on the post.
10. The clamp assembly of claim 1, wherein the cap and base have
opposing inner faces that face each other when assembled in
use.
11. The clamp assembly of claim 10, wherein the cap includes teeth
extending from the inner face to inhibit rotation of the cap
relative to the adjacent members.
12. The clamp assembly of claim 1, wherein the torque-limiting
feature prevents over tightening of the cap relative to the
base.
13. The clamp assembly of claim 1, wherein the post further
includes a key disposed at a distal end of the elongate body.
14. The clamp assembly of claim 13, wherein the key is operable to
matingly engage the applier.
15. The clamp assembly of claim 13, wherein the torque-limiting
feature is disposed at a junction between the elongate body and the
key.
16. The clamp assembly of claim 1, wherein at least one of the cap,
base and post includes resorbable material.
17. The clamp assembly of claim 16, wherein the cap, base and post
include resorbable material.
18. The clamp assembly of claim 1, wherein at least one of the cap,
base and post includes non-resorbable, biocompatible material.
19. The clamp assembly of claim 18, wherein the cap, base and post
include non-resorbable, biocompatible material.
20. The clamp assembly of claim 18, wherein the non-resorbable,
biocompatible material is titanium.
21. A method of fixing a bone plate in a bony defect, wherein the
bone plate has opposing internal and external surfaces that are to
be held in position with internal and external surfaces of
surrounding bone, and a transverse face of the bone plate is to be
fixed in apposition against a transverse face of the surrounding
bone along a border of junction between the bone plate and
surrounding bone, the method comprising: rotatably connecting an
elongated externally threaded post to a base; extending the post
through a cap to engage the threaded post with the cap; positioning
the base and cap on opposing internal and external surfaces of the
bone plate, with a portion of each of the base and cap overlapping
the border of junction; rotating the post to position the cap and
base in a fastening position; and limiting the torque applied by
the post in the fastening position.
22. The method of claim 21, further comprising removing a distal
end of the post projecting from the cap.
23. The method of claim 22, further comprising leaving a proximal
portion of the post projecting from the cap.
24. The method of claim 23, further comprising deforming the
proximal portion of the post projecting from the cap to secure the
base and cap in the fastening positioning.
25. The method of claim 21, further comprising rotating an applier
to cause the post to rotate in the base and position the cap and
base in a fastening position.
26. The method of claim 21, wherein limiting the torque prevents
over tightening of the cap and base.
27. The method of claim 21, wherein limiting the torque includes
severing the post.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This case is a continuation of U.S. patent application Ser.
No. 10/255,146, filed Sep. 25, 2002, which claims priority on U.S.
provisional patent application Serial No. 60/324,658, filed Sep.
25, 2001.
FIELD OF THE INVENTION
[0002] This invention relates to a fastener for quickly and
securely fastening a bone plate to surrounding bone. In one
embodiment, the fastener contains a torque-limiting feature to
prevent over tightening when in the fastening position. In another
embodiment, the invention relates to an instrument for applying the
fastener to a bone plate and surrounding bone.
BACKGROUND AND SUMMARY OF THE INVENTION
[0003] When performing surgery on the brain, it is often necessary
to perform a craniotomy to provide access to portions of the brain.
A craniotomy is a surgical procedure in which a portion of the
cranium is removed to permit access to the brain. To perform the
craniotomy, one or more holes are initially drilled through the
skull. These holes, known as "burr holes," may be located, for
example, at the corners of a triangular region of bone that is to
be temporarily removed. A saw, i.e., a craniotome, is then used to
cut the skull along the line of separation connecting the adjoining
burr holes. The resulting bone cover or bone plug is subsequently
lifted from the underlying dura matter to expose the brain. The
bone cover may either be completely removed from the cranium, or
folded back in a flap along an uncut edge of the flap.
[0004] After completion of the procedure on the brain, the bone
cover must be re-attached to the skull. Several devices have been
developed that are used to facilitate securing the bone cover to
the skull. These devices suffer from the disadvantage that they are
cumbersome or inefficient to apply to the bone flap and surrounding
bone. Further, prior designs are relatively rigid, thus decreasing
conformance to the curvature of the skull. Moreover, prior designs
often required significant instrumentation to apply and/or adjust
the device used to secure the bone cover to the skull. Finally,
prior designs may require removal of the fastening device after
sufficient healing along the line of separation.
[0005] The Cranial Clamp And Method For Fixating A Bone Plate
according to the invention generally includes a cap and base
adjustably joined by a post for threadably bringing the opposing
cap and base closer together, thereby tightening them against the
internal and external surfaces of the bone plate and surrounding
cranium. The base and cap securely fix the bone plate to the
surrounding bone. In one embodiment, at least one of the base, cap
and post include resorbable material.
[0006] The clamp according to the invention may further include an
applier interacting with the post to position the cap and base to
securely fix the bone plate to the surrounding bone. Once
appropriately secured, the applier is removed from the post while
leaving the cap and base interconnected. In one embodiment, the
applier includes a keyed bore and the post includes a key for
engaging the keyed bore of the applier.
[0007] The clamp according to the invention may also include a
torque-limiting feature on the post. The torque-limiting feature
prevents stripping of the threaded interconnection between the post
and cap or overtightening of the cap relative the base. In one
embodiment, the torque-limiting feature is disposed at a junction
between an elongated body portion and a keyed portion of the
post.
[0008] The method for fixating a bone plate in a bony defect
according to the invention allows a bone plate to be fixed in
apposition against a transverse face of surrounding bone along the
border of junction between the bone plate and surrounding bone. A
base connected to an elongated externally threaded post projecting
from the base, and a cap with an internally threaded collar for
mating and threaded engagement with the threaded post connected to
the base, is provided. In one embodiment, at least one of the base,
cap, and post include resorbable material. The base and cap are
placed on opposing internal and external surfaces of the bone
plate, with a portion of each of the base and cap overlapping the
border of junction. The post is rotated into the collar to bring
the base and cap to a fastening position having the base and cap in
tight engagement against the opposing internal and external
surfaces of the bone plate. At least one of the base, cap, and post
include resorbable material, which is resorbed by the body.
[0009] The method according to the invention may further include
providing an applier, wherein the applier rotates the post through
inter-engagement of the applier with the post. The method according
to the invention may also include removing a distal portion of the
post projecting from the cap and leaving a proximal portion of the
post projecting from the cap. Moreover, the proximal portion of the
post projecting from the cap may be deformed to secure the base and
cap in the fastening position.
[0010] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0012] FIG. 1 is a partial perspective view of a clamp and applier
according to the invention securing a bone plate to surrounding
cranium;
[0013] FIG. 2 is a partial sectional view of a clamp and applier
cut along line 2-2 of FIG. 1;
[0014] FIG. 3 is a partially sectioned side view of an assembled
clamp and applier according to the invention;
[0015] FIG. 4 is a top view of a base of a clamp according to the
invention;
[0016] FIG. 5 is a sectional view cut along line 5-5 of FIG. 4;
[0017] FIG. 6 is a side view of a post of the clamp according to
the invention;
[0018] FIG. 7 is an end view of the post of FIG. 6;
[0019] FIG. 8 is a top view of a cap of the clamp according to the
invention;
[0020] FIG. 9 is a side view of the cap of FIG. 8;
[0021] FIG. 10 is a bottom view of the cap of FIG. 8;
[0022] FIG. 11 is a sectional view cut along line 11-11 of FIG.
8;
[0023] FIG. 12 is a sectional view of an applier according to the
invention cut along line 12-12 of FIG. 3;
[0024] FIG. 13 is an end view of the applier of FIG. 12;
[0025] FIG. 14 is a top view of an alternative embodiment of the
clamp according to the invention;
[0026] FIG. 15 is an exploded perspective view with an alternative
embodiment of the clamp according to the invention;
[0027] FIG. 16 is a sectional side view of the assembled clamp of
FIG. 15; and
[0028] FIG. 17 is a sectional side view of an assembled clamp
according to another embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses. While the present invention is
shown securing a bone plate to a surrounding cranium, the fastener
of the present invention may be used in other surgical and
non-surgical applications as well.
[0030] The present invention includes fasteners for securing flat
or curved plate structures to each other. The invention also
includes a positioning and applying instrument that is particularly
useful for positioning and applying the fasteners in a surgical
wound and for securing the fasteners to each other.
[0031] As shown in the drawings, the fastener according to the
invention is a clamp 10 for closing a craniotomy. A craniotomy is
performed by incising pericranium and muscle with cutting diathermy
in the line of an intended bone flap. An incision is not made
interiorly where a pedicle of pericranium or temporalis muscle is
often left uncut to allow some blood supply to the bone and
overlying tissue to remain intact. Alternatively, the pericranium
and muscle may be detached completely from the intended bone
flap.
[0032] As illustrated in FIGS. 1 and 2, the craniotomy is performed
by making a series of burr holes 12 through the cranium 28 about
six or seven centimeters apart with a cranial perforator.
Alternatively, a trephine can be used. The underlying dura matter
is separated from the bone covering the osteotomy site ("the bone
cover") using a periosteal elevator. Osteotomies 14 between the
burr holes 12 are then made using a craniotome that is passed
between adjacent burr holes 12 and moved back and forth to make the
osteotomies 14 from the internal to the external surfaces of the
cranium 28. Alternatively, a Gigli flexible saw can be used to make
the osteotomies 14. A base 16 is not cut with the saw. A bone
forceps (such as a deVilbis forceps) is used to ply a bone plate 18
until the bridge breaks at the base 16 when the bone plate 18 is
elevated.
[0033] The bone plate 18 is separated from the surrounding cranium
12 and 28 along a line of separation formed by osteotomies 14. Each
burr hole 12 has a plate portion 12(a) and a complimentary cranial
portion 12(b), which together form the completed burr hole 12.
Trephines come in graduated sizes, for example, between 0.5 and 2
inches (13-51 millimeters) diameter for drilling burr holes 12 of
sizes varying across this usual range.
[0034] The bone plate 18 may be completely removed if osteotomies
connect all of the burr holes 12. It is often preferred, however,
to leave an intact edge of the craniotomy (such as base 16) to
preserve the blood supplied to the bone. In either case, the bone
plate 18 is typically referred to as the cranial cover.
[0035] After the neurosurgical procedure is performed, the bone
defect must be repaired by placing the bone plate 18 back in the
defect with opposing internal surface 20 and external surface 22
substantially coplanar or aligned with the internal surface 24 and
external surface 26 of surrounding cranium 28. A transverse face 30
of bone plate 18 must also be fixed in opposition with a transverse
face 32 of cranium 28 along a border of junction defined by the
osteotomy 14 between bone plate 18 and surrounding cranium 28.
[0036] In an embodiment shown in FIG. 3, the clamp 10 includes a
first member or base 100 selectively connected to a second member
or cap 150 via a post 120. The cap 150 and base 120 are brought
toward one another by an instrument or applier 170. In one
embodiment, the base 100, post 120, cap 150 and applier 170 are
assembled prior to use in securing the bone plate 18. In another
embodiment, the base 100, post 120 and cap 150 are assembled prior
to use in securing the bone plate 18. Yet another embodiment
include an assembled base 100 and post 120, and the cap 150 and
applier 170 are assembled after positioning the base 100 and post
120 to secure the bone plate 18.
[0037] As shown in FIGS. 4 and 5, the base 100 is formed by a
generally solid disk having a central aperture 102, an annular
inner face 104 surrounding the aperture 102, and an outer face 108
except for a central recess 106 disposed coaxial with the aperture
102. The outer face 108 surrounds the central recess 106 and
generally accommodates the annular inner face 104. The inner face
104 and outer face 108 circumscribe a collar 110 projecting
inwardly from the inner face 104 coaxially about central aperture
102. In this embodiment, aperture 102 extends through base 100 and
is adapted to receive the post 120, whereby the post 120 is able to
rotate relative the base 100. In other embodiments, aperture 102
may only have an opening at the inner side of collar 110 and not
extend through the base 100.
[0038] As shown in FIGS. 6 and 7, the post 120 includes a head 122
at a first end and a key 124 at a second end. A substantially
cylindrical, elongated body 126 extends between the head 122 and
key 124, and generally includes ribs or threads 128 along its
length. Threads 128 will be used in the following description, but
ribs are within the scope of the invention. At the head Attorney
Docket No. 5490-000259/COB end of the post 120, the threads 128
taper or run out from a minor to major diameter of the body 126
over 360 to 720 degree revolutions. In one embodiment, the junction
of the body 126 and key 124 provides a torque-limiting feature 130
to allow the key 124 to break from the body 126 to prevent
stripping the threaded interface between the post 120 and cap 150
or over-tightening the clamp 10. In one embodiment, the ribs or
threads 128 along post 120 are pliable and resilient due to
material elasticity. Such pliable, resilient ribs or threads 128
allow the cap 150 to be quickly secured by ratcheting cap 150 along
the threads 128 on the post 150 to quickly position the cap 150
relative the base 100 along post 120. Due to the elasticity in
engagement of the ribs or threads, however, once the cap 150 is
ratcheted in position along post 120, it can be further adjusted
toward base 100 by threaded rotation or further ratcheting.
Further, in one embodiment, threads 128 can extend partially along
the elongated body 126 of the post 120. In this manner, the cap 150
can be slid along a portion of the elongated body 126, which may
include ribs, prior to engaging the threads 128.
[0039] The head 122 is preferably a rounded disk shape disposed
coaxially with the elongated body 126, which flares outwardly at
the junction with the head 122. In one embodiment, the key 124 is a
generally D-shaped cross section formed at the second end of the
post 120. In other embodiments, the shape or cross section of the
key 124 may differ. When clamp 10 is assembled for use, the post
126 is received coaxially through the aperture 102 of the base 100
such that head 122 seats in the central recess 106, as best shown
in FIG. 3.
[0040] The cap 150 fastens to the base 100 to secure the bone plate
18 in place and occlude the burr holes 12. As shown in FIGS. 6-9,
the cap 150 is a generally solid disk with an outer face 152 except
for a central recess 154 disposed coaxially about a central
aperture 156 extending therethrough. The cap 150 has an annular
inner face 160 including a collar 158 surrounding the aperture 156.
The inner face 160 comprises an arcuate channel coaxially
surrounding the collar 158 and aperture 156. Further, the inner
face 160 includes a series of radial teeth 162 radiating
circumferentially toward the outer diameter of the inner face 160.
The teeth 162 form a serrated edge 164 about the periphery of cap
150. The teeth 162 are disposed at an angle I and height H along
the serrated edge 164. For example, in an approximately 14
millimeter cap 150, the teeth 162 are separated by an angle I
approximating 53 degrees at a height H approximating 0.047 inches.
In the embodiment shown, the aperture 156 of collar 158 includes
internal threads 166. For this embodiment, the threads are
left-handed, but should compliment the threads 128 of the post 120
in other embodiments.
[0041] As shown in FIGS. 1, 3, 12 and 13, the applier 170 is used
to position and fasten the clamp 10. The applier 170 includes a
generally hexagonal elongated body 172 including a bore 174
extending generally coaxially therethrough along its length. At a
first end, the bore 174 extends to an opening 176. At an opposite
end, the bore 174 extends to a keyed bore 178. In one embodiment,
keyed bore 178 has a generally D-shaped cross section to compliment
the cross section of key 124. When key 124 is inserted into keyed
bore 178, rotation of body 172 rotates the post 120. In one
embodiment, the applier 170 is secured to the post 120 prior to use
in securing a bone plate 18 by deforming a portion of the post 120
extending through the keyed bore 178 and into the bore 174. This
deformation, indicated as 132 in the drawings, secures the post 120
and applier 170 to one another. As shown, the body 172 of the
applier has a generally hexagonal cross section, but in other
embodiments can have other shapes and cross sections. Further, bore
174 tapers to keyed bore 178 at an angle .theta.. In this
embodiment, angle .theta. approximates 118 degrees. Also in this
embodiment, bore 174 extends approximately 90 percent of the length
of applier 170, while keyed bore 178 extends approximately ten
percent thereof.
[0042] In one embodiment, clamp 10 includes resorbable materials.
In one variation of this embodiment, the base 100, post 120, and
cap 150 are all comprised of resorbable materials. In another
variation, the base 100 and cap 150 are comprised of resorbable
material, while the post 120 is comprised of a suitable
biocompatible material. In yet another variation, either the base
100 or cap 150 is comprised of resorbable material, and the post
120 may be comprised of resorbable and/or biocompatible material.
Alternatively, only the post 120 comprises resorbable material. The
main benefit of using resorbable material is that the clamp 10, or
components thereof, will resorb into the body over a generally
predictable time period once a sufficient level of healing has
occurred, for example, at the junction of a bone fracture, thus
negating need for subsequent removal of the clamp 10.
[0043] One resorbable material is used in products marketed by
Biomet, Inc. (Warsaw, Ind.) under the trademark LACTOSORB.RTM..
LACTOSORB.RTM. is an absorbable co-polymer synthesized from all
natural ingredients: 82 percent L-lactic acid and 18 percent
glycolic acid. Unlike the homopolymers in common use, such as 100
percent poly-L-lactic acid (PLLA) or 100 percent poly-glycolic acid
(PGA), LACTOSORB.RTM. co-polymer is substantially amorphous (i.e.,
without crystallinity), meaning that its degradation is uniform,
precluding the crystalline release most often associated with
degrading homopolymers that have been associated with inflammatory
reactions. Furthermore, the LACTOSORB.RTM. co-polymer ratio permits
the polymer to retain most of its strength for six to eight weeks,
which is appropriate for healing, but not so long as to raise
concerns about long-term stress shielding. It should also be
understood that any other type of resorbable material may also be
used herein.
[0044] In an alternate embodiment, the clamp 10 includes of
non-resorbable, biocompatible materials. In one variation of this
embodiment, the base 100, post 120 and cap 150 are all comprised of
non-resorbable, biocompatible materials. In another variation, the
base 100 and cap 150 are comprised of resorbable material, while
the post 120 is comprised of a suitable non-resorbable,
biocompatible material. In yet another embodiment, either the base
100 or cap 150 is comprised of resorbable material, while the other
of the base 100 and cap 150 and the post 120 may be comprised of a
suitable non-resorbable, biocompatible material. Alternatively,
both the base 100 and cap 150 comprise non-resorbable,
biocompatible material and the post 120 comprises resorbable
material.
[0045] One non-resorbable, biocompatible material is titanium.
Titanium and its alloys are high strength, durable and corrosion
resistant materials. A titanium containing alloy such as, for
example, Ti.sub.6Al.sub.4V is commonly used in surgical
applications. Ti.sub.6Al.sub.4V is inert to human body fluids thus
its resistance in bodies is very high. Furthermore,
Ti.sub.6Al.sub.4V has been shown to have a high resistance to
abrasion and also has a high fatigue resistance. It should be
understood that any other suitable type of non-resorbable,
biocompatible material may also be used herein and should be
considered within the scope of the present invention, including
other metals having a layer of biocompatible cement to line the
metal in order to prevent the body's immune system from rejecting
the implanted material.
[0046] The clamp 10 according to the invention can be assembled in
various ways for use in replacing the bone plate 18 following a
craniotomy. For example, the clamp 10 can be provided unassembled
for use in securing the bone plate 18, in which case a user would
begin assembly of clamp 10 by inserting the post 120 into the base
10. In another embodiment, the clamp 10 may be provided to the user
at least partially assembled, for example with the post 120
assembled to the base 100, or otherwise affixed thereto. In another
embodiment, the clamp 10 would be assembled further by not only
assembling the post 120 and base 100 to one another, but also
connecting the post 120 to the cap 150. In this way, once the clamp
10 is in position to secure a bone plate 18, the applier 170 is
connected to the post 120 for securing the bone plate 18 to the
surrounding cranium 28. In yet another embodiment, the clamp 10
includes assembling the post 120 to the base 100 and cap 150, as
well as securing the applier 170 to the post 120. The post 120 may
be secured to the applier 170 in various ways; as shown, an end
portion of the post 120 extending through the key shaped bore 178
and into the bore 174 is deformed after assembly of the post 120 to
both the base 100 and cap 150, whereby the entire assembly of the
base 100, post 120, cap 150, and applier 170 is provided assembled
for use in replacing the bone plate 18 following the
craniotomy.
[0047] The clamp 10 is used to replace the bone plate 18 following
a craniotomy, as shown in FIG. 1. The craniotomy is performed by
providing at least one craniotomy hole or multiple holes, such as
burr holes 12, through the skull. The burr holes 12 are
subsequently connected by osteotomies 14 to create a separation
border for the bone plate 18, which may be a plate that is removed
or a flap that is folded back along one edge. Alternatively, a
circular bone plate 18 can be formed by providing one burr hole 12
and a circular osteotomy beginning and ending at the one burr hole
12. In each case, the craniotomy opening includes a portion 12a of
at least one burr hole 12 formed in the bone plate 18 and a
complimentary portion 12b of the hole formed in the surrounding
cranium 28. The subsequent description employs the example of
multiple burr holes 12 and osteotomies 14 connecting the holes 12,
as shown in FIG. 1.
[0048] As shown in FIG. 2, the bone plate 18 has the internal
surface 20 and external surface 22 respectively placed in
substantially coplanar relationship with the internal surface 24
and external surface 26 of the surrounding cranium 28 when a
craniotomy is closed. Opposing transverse faces 30, 32 of the bone
plate 18 and surrounding cranium 28 appose along the separation
border when the bone plate 18 is replaced. Faces 30, 32 are
generally parallel to each other when in apposition.
[0049] In a method of the present invention, the bone plate 18 is
folded back along a base 16 or completely removed to expose the
underlying dura matter and brain. In one embodiment, following the
intracranial procedure, and prior to replacing the bone plate 18
into its original orientation within the craniotomy opening, the
assembled base 100 and post 120 is placed below each burr hole 12
with the inner face 104 of the base 100 against the internal
surface 24 of the cranium 28 and the post 120 extending through the
hole 12. The base 100 overlaps the margins of hole 12 and the
separation border between the bone plate 18 and surrounding cranium
28. The collar 110 projects upwardly toward the hole 12 and the
post 120 extends upwardly and through the hole 12. In another
embodiment, the assembled base 100, post 120, and cap 150 are
positioned with the inner face 104 and the base 100 against the
internal surface 24 of the cranium 28, the post 120 extending
through the hole 12, and the cap 150 positioned above the hole 12
with the inner face 160 of the cap 150 facing the external surface
26 of the cranium 28. In yet another embodiment, the applier 170 is
connected to the keyed end 124 of the post 120 such that the
assembled base 100, post 120, cap 150, and applier 170 are
positioned relative each bore hole 12 with the inner face 104 of
the base 100 against the internal surface 24 of the cranium 28, the
post 120 extending through the hole 12, and the inner face 160 of
the cap 150 facing the external surface 26 of the cranium 28. The
bone plate 18 is then replaced into the craniotomy opening, for
example, by folding the bone plate 18 along base 16 back down into
the craniotomy opening.
[0050] After the bone plate 18 is restored to its original position
in the craniotomy opening, complimentary portions 12a, 12b now
reform hole 12. The post 120 is positioned within hole 12 with the
inner face 104 of the base 100 engaging the internal surfaces 20
and 24 of bone plate 18 and cranium 28, respectively. If not
already assembled to the post 120, the cap 150 is positioned over
the reformed hole 12 to engage the post 120 above the hole 12. The
post 120 is introduced into the collar 158 of cap 150 through the
aperture 156. In one variation of this embodiment, wherein the
threads 128 extend generally along the length of the elongated body
126 of the post 120, the threads of internally threaded collar 158
engage the threads 128 of externally threaded elongated body 126
and the cap 150 is threaded into engagement with bone plate 18 and
surrounding cranium 28. In another variation of this embodiment,
wherein a portion of the elongated body 126 is externally threaded,
the cap 150 is slid along an unthreaded leading portion of the
elongated body 126 until it engages an externally threaded portion
of the elongated body 126. In any embodiment, the ribs or threads
128 may be pliable and resilient, whereby the cap 150 is ratcheted
along the externally ribbed or threaded elongated body 126 into
contact with the external surface of the cranium 28 and bone plate
18.
[0051] In one embodiment, once the cap 150 is in position to be
threadably driven, the applier 170 is attached to the post 120 by
inserting the key 124 of the post 120 into the keyed bore 178 of
the applier 170. In another embodiment, the applier 170 is
connected to the post 120 prior to positioning the post 120 on the
burr hole 12. In each embodiment, the cap 150 is held in place with
one hand while the applier 170 is rotated with the other hand,
causing the post 120 to rotate relative the base 100 and threadedly
engage the cap 150 to diminish the distance between the base 100
and the cap 150 and tighten respective inner faces 104, 160 of the
base 100 and cap 150 against the respective internal and external
surfaces of the cranium 28 and bone plate 18. The cap 150 and base
100 are brought together in frictional engagement against opposing
faces of the bone plate 18 and surrounding cranium 28, thereby
clamping the bone plate 18 and surrounding cranium 28 to each
other. The teeth 162 of the cap 150 anchor the cap 150 to both the
bone plate 18 and surrounding cranium 28, thereby preventing
rotation of the cap 150 while the base 100 is secured thereto. The
cap 150 is attached to the bone of the bone plate 18 and cranium 28
as the teeth 162 become progressively advanced into the bone by
rotating the clamp 10.
[0052] The torque-limiting feature 130 disposed at the junction of
the body 126 and key 124 of the post 120 allows the key 124 to
break from the body 126 to prevent stripping the threaded interface
of the post 120 and cap 150 or overtightening the cap 150 relative
the base 100. The key 124 will separate from the body 126 of the
post 120 before the threaded interface between the cap 150 and post
120 strips. In this manner, the time and expense of replacing a
stripped clamp 10 is avoided, and a proper amount of frictional
engagement of the cap 150 and base 100 against opposing faces of
the bone plate 18 and surrounding cranium 28 is provided. The
torque-limiting feature 130 of the post 120 could be provided in
other ways within the scope of this invention, such as by notching
the post 120 at a portion other than the junction of the key 124
and body 126, or narrowing the diameter of the post 120 at any
point along the body 126 and key 124, among other ways.
[0053] After the cap 150 and base 100 are suitably brought together
against the opposing faces of the bone plate 18 and surrounding
cranium 28 to clamp the bone plate 18 and surrounding cranium 28 to
each other, a distal portion of the post 120 is cut a distance D
above the cap 150, as best shown in FIG. 2. The distance D is a
distance suitable to provide a proximal portion 140 of the post 120
with enough material to secure the cap 150 to the post 120 upon
deformation of the proximal portion 140 of post 120. In one
embodiment, the distance D is approximately two millimeters for a
14 millimeter diameter cap 150. The remaining distance D of the
post 120 is flattened or otherwise deformed to prevent the cap 150
from backing off the post 120 and away from the base 100.
Preferably, opthalmic cautery or a heat pen is used to cut the post
a distance D above the cap 150, and further used to deform the
remaining distance D of the post 120 to secure the cap 150 relative
the base 100, as best shown in FIG. 1. A heat pen, such as the
LACTOSORB.RTM. Heat/Contouring Pen, is available from W. Lorenz
Surgical of Jacksonville, Fla.
[0054] The clamp 10 is used to clamp the bone plate 18 to the
surrounding cranium 28 at one or more of the burr holes 12, and
preferably all of the burr holes 12 as shown in FIG. 1. The clamp
10 can also clamp the bone plate 18 to the surrounding cranium
along an osteotomy 14. That is, use of the clamp 10 is not limited
to occluding burr holes 12, but is useful for supporting a bone
plate 18 in a circular or curved osteotomy 14 as well. A base 100
and post 120 is therefore positioned below each burr hole 12 or at
discrete points along an osteotomy with the post 120 projecting up
into and through the hole 12 on the line of separation prior to
replacement of the bone plate 18. A cap 150 is then threaded along
each externally threaded post 120 until the cap 150 and base 100
clamp the bone plate 18 and surrounding cranium 28 securely to each
other. The cap 150 and base 100 are in a fixed relationship
determined by the degree of advancement of the externally threaded
post 120 into the internally threaded collar 158 of the cap 150, so
that the movement of the bone plate 18 is substantially prevented.
The bone plate 18 and surrounding cranium 28 are held firmly in
place with respect to each other, which avoids inadvertent
depression of the bone plate 18 and attendant catastrophic
neurological consequences.
[0055] The outer face of the cap 150 diminishes the aesthetic
problem of visible indentations on the skull or face overlying the
craniotomy burr holes 12. Further, by employing a malleable
material with high ductility for the cap 150, aesthetic problems
are further reduced. The closed base 100 tightly engages the
internal surfaces of the bone plate 18 and surrounding cranium
providing ideal occlusion of the hole 12 to held avoid infection or
trauma. The clamp 10 also clamps the bone plate 18 in place
quickly, thereby diminishing the period of time the brain must be
exposed and also reduces medical expenses associated with prolonged
time in the operating room. In one embodiment, as explained
previously, the clamp 10 is made partially or wholly of resorbable
material so that the body can resorb the clamp after suitable bone
growth across the osteotomies. Beside the biocompatibility of such
materials, such a clamp 10 need not be removed by a follow-up
neurosurgical procedure.
[0056] The clamp 10 may be made in many different sizes. For
purposes of illustration, the diameter of the post 120 can be 1.8
millimeters (the same diameter as the apertures 156 and 102), the
diameter of base 100 can be 14 millimeters, and the diameter of the
cap 150 may be 14 millimeters. In one embodiment, the post 120 is
35.6 millimeters long, with key 124 extending approximately 5
millimeters from a leading end of the post 120.
[0057] The clamp 10 is adjustable for use in repairing craniotomies
through bone of varying thickness. The pterion (in the
temporal-parietal region), for example, is quite thin and would
conventionally require a shorter fastener. Because the unused
portion of the post 120 is simply removed once the base 100 and cap
150 are appropriately positioned, different-sized fasteners are not
necessary. For example, the parietal or frontal bone may be 10 to
20 millimeters thick, wherein the present invention would work
properly with both bone thicknesses, as well as smaller or larger
thicknesses.
[0058] Other variations of the disclosed fastener are possible. The
relative positions of the cap and base can be reversed, for
example, by disposing the cap 150 on the interior surface of the
cranium and bone plate 18 while the base 100 is disposed along the
external surfaces thereof by simply threading the collar 110 of the
base 100 and leaving the collar 158 of the cap 150 unthreaded. The
cap 150 and base 100 may assume many shapes other than circular,
and may, for example, be square or triangular. Bone plates other
than in the skull may be secured to surrounding bone, for example,
a relatively flat top bone such as the trapezium, mandible, maxilla
or bones of the orbit. The outer face of the cap 150 may also be
flat, particularly in areas of the skull, such as the temporal
bone, with relatively flat external surfaces. The fastener may also
be used to fix adjacent members together, even where the members
are curved. A malleable material may be used to accommodate
differing surface shapes. Such materials include LACTOSORB.RTM.
copolymer, VHMN polyethylene, polyethyl ketone, silicone, nylon,
etc.
[0059] In one embodiment, the base and cap may include flexible
struts 200 to provide more flexibility than a solid member, as
shown in FIG. 14 for exemplary base 100'. The struts 200 are
preferably made of a high-density polyethylene. In the disclosed
embodiment, each strut 200 does not occupy more than about a 20 to
30 degree sector of the base or cap. The struts 200 radiate from
the center of the cap or base to a peripheral ring, but they can
alternatively taper, flair, or assume other shapes that
sufficiently reduce the solid areas of the base and cap to increase
the flexibility such that it conforms to the curvature of the skull
when the clamp is tightened to such an extent that the bone in the
skull is not fractured or damages. For example, the modulus of
flexibility of the cap or base, or each individual strut, is
300,000 to 700,000 PSI.
[0060] In yet another embodiment shown in FIGS. 15-17, the clamp 10
includes a first member or base 100" selectively connected to a
second member or cap 150" via a post 120". As before, the cap 150"
and base 100" are brought toward one another by an instrument or
applier 170. The base 100" is formed by a generally solid disk
having a central aperture 102" for rotatably receiving the post
120". Similar reference numbers are used in this description to
note features similar to those described for the prior
embodiments.
[0061] The post 120" includes a head 122" at a first end and a key
124 at a second end. A substantially cylindrical elongated body 126
extends between the head 122" and the key 124, and generally
includes ribs or threads 128 along its length. As before, threads
128 are used in the description, but ribs are within the scope of
the invention. The head 122" of the post 120" includes a channel
121 for receiving a periphery 103 of the aperture 102" in order to
rotatably secure the base 100" to the post 120". Slots 105 allow
deflection of the base 100" at the periphery 103 to facilitate
insertion of the head 122" in the aperture 102", whereby the
periphery 103 is received in the channel 121. In this manner, as
described in prior embodiments, the post 120" is able to rotate
relative the base 100".
[0062] The cap 150" is a generally solid disk having a central
aperture disposed coaxially therethrough for receiving the collar
110". The collar 110" includes a central aperture 156" extending
therethrough and including internal threads 166 that mate with the
threads 128 on the post 120". The collar 110" includes a flange 157
to prevent pulling the collar 110" through the cap 150" during
assembly or use. The collar 110" is press fit into the aperture 159
of the cap 150", whereby the collar 110" and cap 150" rotate
together. Alternatively, the collar 110" and cap 150" could be
threaded together where the threaded engagement between the collar
110" and cap 150" is an opposite thread to that of the engagement
between the internal thread 166 of the collar 110" and the thread
128 of the post 120".
[0063] In a variation of this latter embodiment, the collar 110"
can be a collar 110" that is formed integral with a cap 150", as
shown in FIG. 17. The operation and use of this variation of the
invention is similar to that described for the previous embodiment
of the invention, and the inventions shown in FIGS. 15-17 are used
and assembled in manners similar to that described above for the
prior embodiments.
[0064] As used in this specification, conformance to a curved
member does not require identical curvature of the conforming
member at the surface to which it conforms. Substantial conformity
of the members is all that is required, and that includes surfaces
between flat planes and curves that precisely conforms to the
curved member against which the conforming member seats.
[0065] The description of the invention is merely exemplary in
nature and, thus, variations that do not depart from the gist of
the invention are intended to be within the scope of the invention.
Such variations are not to be regarded as a departure from the
spirit and scope of the invention.
* * * * *