U.S. patent application number 09/863767 was filed with the patent office on 2002-11-28 for skull closure.
Invention is credited to Bremer, Paul W..
Application Number | 20020177850 09/863767 |
Document ID | / |
Family ID | 25341740 |
Filed Date | 2002-11-28 |
United States Patent
Application |
20020177850 |
Kind Code |
A1 |
Bremer, Paul W. |
November 28, 2002 |
SKULL CLOSURE
Abstract
A fastener system for use in reattaching a skull flap in an
opening formed in a patient's skull during brain surgery is simple,
quick and easy to use, and cost effective. The system includes a
fastener element and a substantially disc shaped lock element. The
fastener element has a shank with a plurality of ratchet teeth, and
a plurality ridges extending upwardly from the shank a distance
greater than the height of the ratchet teeth, and substantially
perpendicular to the ratchet teeth. The ridges engage at least one
of the skull and skull flap and either bend or collapse, or cut
locking grooves into the skull or skull flap, to provide a force
holding the shank in engagement with the skull and skull flap. The
lock element may have force concentrating projections extending
outwardly toward the fastener head, and the head may have a
plurality of resilient[ outrigger leaves.
Inventors: |
Bremer, Paul W.;
(Jacksonville, FL) |
Correspondence
Address: |
NIXON & VANDERHYE P.C.
8th Floor
1100 North Glebe Road
Arlington
VA
22201-4714
US
|
Family ID: |
25341740 |
Appl. No.: |
09/863767 |
Filed: |
May 24, 2001 |
Current U.S.
Class: |
606/70 |
Current CPC
Class: |
A61B 17/688 20130101;
Y10S 606/912 20130101 |
Class at
Publication: |
606/70 |
International
Class: |
A61B 017/80 |
Claims
What is claimed is:
1. A fastening system comprising: a fastener element of
bio-compatible radiolucent plastic material comprising a
substantially disc shaped head and a shank; said shank having
substantially flat first and second substantially parallel
surfaces, said surfaces having ratchet teeth thereon; a
substantially disc shaped lock element of bio-compatible
radiolucent rigid plastic material having a through extending
opening and locking teeth defining at least part of said opening,
said locking teeth cooperating with said ratchet teeth to allow
said shank to pass through said opening so that said head and lock
element can be forced toward each other, but not allowing movement
away from each other; and a plurality of ridges extending upwardly
from at least one of said first and second substantially parallel
surfaces adjacent said head, said ridges extending substantially
perpendicular to said ratchet teeth.
2. A system as recited in claim 1 wherein said ridges upstand from
both said first and second surfaces, and wherein said ridges are of
relatively soft plastic and constructed so that in use said ridges
bend or collapse and provide a wedging action against a bone
surface engage thereby.
3. A system as recited in claim 1 wherein said ridges are of hard
plastic or metal and constructed so that in use said ridges cut
locking grooves in a bone surface engaged thereby.
4. A system as recited in claim 1 wherein said ridges are about 3-7
mm long.
5. A system as recited in claim 4 wherein said ridges substantially
abut said head.
6. A system as recited in claim 5 wherein said ridges upstand from
both said first and second surfaces, and wherein the distance from
the tip of a ridge extending upwardly from said first surface to
the tip of a ridge extending upwardly from said second surface is
between about 2-5 mm.
7. A system as recited in claim 1 wherein said ridges upstand from
both said first and second surfaces, and wherein the distance from
the tip of a ridge extending upwardly from said first surface to
the tip of a ridge extending upwardly from said second surface is
between about 2-5 mm.
8. A system as recited in claim 1 wherein said lock element has
first and second faces, and a plurality of force concentrating
projections extending outwardly from said first face, toward said
head in use.
9. A system as recited in claim 8 wherein said locking teeth extend
outwardly from said first face.
10. A system as recited in claim 9 wherein said head has a
plurality of resilient outrigger leaves.
11. A system as recited in claim 1 wherein said head has a
plurality of resilient outrigger leaves.
12. A method of reattaching a skull flap, removed during brain
surgery and leaving an opening in a patient's skull, the flap
having an area less than the area of the opening but substantially
the same shape, and using a fastening system, comprising a fastener
element made of bio-compatible radiolucent rigid plastic having a
shank with ratchet teeth and a substantially disc shaped lock
element with an opening defined at least in part by at least one
locking tooth, and a plurality of ridges upstanding from the shank
and extending substantially perpendicular to the ratchet teeth;
said method comprising: (a) placing a plurality of fastener heads,
with shanks facing outwardly, in the skull opening; (b) placing the
skull flap in the skull opening so that a gap is provided between
the outer periphery of the skill flap and the periphery of the
skull opening, and the fastener shanks extend through the gap and
the ridges engage at least one of the skull and the skull flap and
provide a force holding the shank in operative engagement with the
skull and skull flap; (c) placing the lock elements over the
shanks; (d) for each fastener forcing the lock toward the head so
that the ratchet teeth and at least one locking tooth move with
respect to each other, until the head and lock element are locked
together holding the skull flap in a position closing the skull
opening; and (e) removing substantially all shank portions
extending outwardly from the lock elements.
13. A method as recited in claim 12 wherein (b) is practiced so
that ridges engage both the skull and skull flap.
14. A method as recited in claim 13 wherein the ridges are of soft
plastic and constructed so that they bend or collapse; and wherein
(b) is practiced so that the ridges bend or collapse so as to
provide a wedging action holding the shank between the skull and
skull flap.
15. A method as recited in claim 13 wherein the ridges are of hard
plastic or metal and are constructed so that they can cut locking
grooves in bone; and wherein (b) is practiced so as to cut locking
grooves in the skull and skull flap so as to lock the shank in
place therebetween.
16. A method as recited in claim 12 wherein the ridges are of hard
plastic or metal and are constructed so that they can cut locking
grooves in bone; and wherein (b) is practiced so as to cut locking
grooves in the skull or skull flap so as to lock the shank in place
therebetween.
17. A method as recited in claim 12 wherein the ridges are of soft
plastic and constructed so that they bend or collapse; and wherein
(b) is practiced so that the ridges bend or collapse so as to
provide a wedging action holding the shank between the skull and
skull flap.
18. A method as recited in claim 12 wherein the locking element has
a plurality of substantially axially extending force concentrating
projections; and wherein (d) is practiced so as to cause the force
concentrating projection to engage at least one of the skull and
skull flap to enhance securement of the locking element to the
skull or skull flap.
19. A method as recited in claim 18 wherein (d) is practiced so
that the force concentrating elements operatively engage both the
skull and skull flap.
20. A fastener system comprising: a fastener element of
bio-compatible radiolucent rigid plastic material comprising a
substantially disc shaped head and a shank; said shank having a
plurality of ratchet teeth thereon, and a thickness of about 7 mm
or less; a substantially disc shaped lock of bio-compatible
radiolucent plastic material having a through extending opening
into at least one locking tooth defining at least part of said
opening, said at least one locking tooth cooperating with said
ratchet teeth to allow said shank to pass through said opening so
that said head and lock can be forced toward each other, but not
allowing movement away from each other; and wherein said lock
element has first and second faces, and a plurality of force
concentrating projections extending outwardly from said first face,
toward said head in use.
21. A system as recited in claim 20 wherein said locking teeth
extend outwardly from said first face.
22. A system as recited in claim 21 wherein said head has a
plurality of resilient outrigger leaves.
23. A fastener system comprising: a fastener element of
bio-compatible radiolucent rigid plastic material comprising a
substantially disc shaped head and a shank; said shank having a
plurality of ratchet teeth thereon, and a thickness of about 7 mm
or less; a substantially disc shaped lock of bio-compatible
radiolucent plastic material having a through extending opening
into at least one locking tooth defining at least part of said
opening, said at least one locking tooth cooperating with said
ratchet teeth to allow said shank to pass through said opening so
that said head and lock can be forced toward each other, but not
allowing movement away from each other; and wherein said head has a
plurality of resilient outrigger leaves.
24. A system as recited in claim 23 wherein said shank has a
plurality of ridges substantially abutting said head and extending
substantially perpendicular to said ratchet teeth a distance of
about 3-7 mm from said head.
25. A system as recited in claim 24 wherein said shank itself has a
thickness of about 1-1.5 mm, and at said ridges a thickness of
about 2-5 mm.
26. A system as recited in claim 20 wherein said shank has a
plurality of ridges substantially abutting said head and extending
substantially perpendicular to said ratchet teeth a distance of
about 3-7 mm from said head.
27. A system as recited in claim 26 wherein said shank itself has a
thickness of about 1-1.5 mm, and at said ridges a thickness of
about 2-5 mm.
28. A system as recited in claim 1 wherein said shank itself has a
thickness of about 1-1.5 mm, and at said ridges a thickness of
about 2-5 mm.
29. A system as recited in claim 2 wherein said shank itself has a
thickness of about 1-1.5 mm, and at said ridges a thickness of
about 2-5 mm.
30. A system as recited in claim 3 wherein said shank itself has a
thickness of about 1-1.5 mm, and at said ridges a thickness of
about 2-5 mm.
31. A system as recited in claim 28 wherein said ridges are about
3-7 mm long.
32. A system as recited in claim 1 wherein said shank has first and
second exterior side walls extending over a portion of the length
thereof including past said ridges and at least some of said
ratchet teeth; and wherein said locking element opening has first
and second side portions for receiving said side walls.
33. A system as recited in claim 32 wherein said side walls extend
upwardly past said first and second shank surfaces a distance
approximately equal to the heights of said ratchet teeth, and less
than the height of said ridges.
34. A system as recited in claim 33 wherein said shank has a basic
thickness of about 1 mm, and at said side walls a thickness of
about 2 mm and at said ridges a thickness of about 3 mm.
35. A fastener system comprising: a fastener element of
bio-compatible radiolucent rigid plastic material comprising a
substantially disc shaped head and a shank; said shank having a
plurality of ratchet teeth thereon, and a thickness of about 7 mm
or less; a substantially disc shaped lock of bio-compatible
radiolucent plastic material having a through extending opening
into at least one locking tooth defining at least part of said
opening, said at least one locking tooth cooperating with said
ratchet teeth to allow said shank to pass through said opening so
that said head and lock can be forced toward each other, but not
allowing movement away from each other; and wherein said shank has
first and second exterior side walls extending over a portion of
the length thereof including past at least some of said ratchet
teeth; and wherein said locking element opening has first and
second side portions for receiving said side walls.
36. A system as recited in claim 35 wherein said side walls extend
past said first and second shank surfaces a distance approximately
equal to the heights of said ratchet teeth.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] U.S. Pat. No. 6,022,351 (the disclosure of which is hereby
incorporated by reference herein) has provided a significant
advance in the art of bone fastening systems during surgical or
related medical procedures, in reattaching a skull flap. The
invention provides an improvement over the system and method of the
U.S. Pat. No. 6,022,351, particularly in providing an enhanced
force holding the shank in engagement with the skull and skull
flap, and in addition other features are provided that facilitate
holding the locking element in place, and facilitate maintaining
the fastener and locking elements clamped together in a position
holding the skull flap in place. These advantageous results are
provided according to the present invention by utilizing a
plurality of ridges extending from the fastener head generally
perpendicular to the ratchet teeth, and extending upwardly from the
fastener shank substantially flat surfaces; by providing a
plurality of force concentrating projections on the locking element
disc extending axially with respect to the disc; and by providing
side walls on the shank having approximately the height of the
ratchet teeth, and engaged in side portions of the opening in the
locking element.
[0002] According to one aspect of the present invention there is
provided a fastening system comprising: A fastener element of
bio-compatible radiolucent plastic material comprising a
substantially disc shaped head and a shank. The shank having
substantially flat first and second substantially parallel
surfaces, the surfaces having ratchet teeth thereon. A
substantially disc shaped lock element of bio-compatible
radiolucent rigid plastic material having a through extending
opening and locking teeth defining at least part of the opening,
the locking teeth cooperating with the ratchet teeth to allow the
shank to pass through the opening so that the head and lock element
can be forced toward each other, but not allowing movement away
from each other. And, a plurality of ridges extending upwardly from
at least one of the first and second substantially parallel
surfaces adjacent the head, the ridges extending substantially
perpendicular to the ratchet teeth.
[0003] The ridges may be of two different types, both of which
provide a force holding the shank in engagement with the skull and
skull flap. The first type of ridges may be of relatively soft
plastic, and constructed so that in use the ridges bend or collapse
and provide a wedging action against a bone surface engaged
thereby. Another alternative is to provide the ridges out of a hard
plastic or metal and construct them so that in use the ridges cut
locking grooves in a bone surface engaged thereby. In either case
the stability of the fastening system is enhanced, as is its
ability to hold the skull flap properly in place.
[0004] The ridges may be about 3-7 mm long, and typically
substantially abut the fastener head. Desirably the ridges upstand
from both the first and second surfaces of the shank, and the
distance from the tip of a ridge extending upwardly from the first
surface to the tip of a ridge extending upwardly from the second
surface is between about 2-5 mm, most desirably about 3-3.5 mm.
Typically between two and six ridges are provided (extending
upwardly from each of the first and second surfaces). The shank may
have a thickness of about 1-1.5 mm.
[0005] Also the shank may have first and second exterior side walls
extending over a portion of the length thereof including past the
ridges, and at least some of the ratchet teeth. The locking element
opening has first and second side portions for receiving the side
walls. For example the side walls extend upwardly past the first
and second shank surfaces a distance approximately equal to the
heights of the ratchet teeth, and less than the height of the
ridges. For example in one embodiment the shank has a basic
thickness of about 1 mm, and at the side walls a thickness of about
2 mm, and at the ridges a thickness of about 3 mm.
[0006] The lock element typically has first and second faces and a
plurality of force concentrating projections extending outwardly
from the first face, toward the fastener head in use. The locking
teeth also typically extend outwardly from the first face. The
fastener head may have a plurality of resilient outrigger leaves,
which may be deformed during the clamping operation, to provide a
force enhancing the clamping action.
[0007] According to another aspect of the present invention there
is provided a method of reattaching a skull flap, removed during
brain surgery and leaving an opening in a patient's skull, the flap
having an area less than the area of the opening but substantially
the same shape, and using a fastening system, comprising a fastener
element made of bio-compatible radiolucent rigid plastic having a
shank with ratchet teeth and a substantially disc shaped lock
element with an opening defined at least in part by at least one
locking tooth, and a plurality of ridges upstanding from the shank
and extending substantially perpendicular to the ratchet teeth. The
method comprises: (a) Placing a plurality of fastener heads, with
shanks facing outwardly, in the skull opening. (b) Placing the
skull flap in the skull opening so that a gap is provided between
the outer periphery of the skill flap and the periphery of the
skull opening, and the fastener shanks extend through the gap and
the ridges engage at least one of the skull and the skull flap and
provide a force holding the shank in operative engagement with the
skull and skull flap. (c) Placing the lock elements over the
shanks. (d) For each fastener forcing the lock toward the head so
that the ratchet teeth and at least one locking tooth move with
respect to each other, until the head and lock element are locked
together holding the skull flap in a position closing the skull
opening. And, (e) removing substantially all shank portions
extending outwardly from the lock elements.
[0008] In the method (b) may be practiced so that the ridges engage
both the skull and the skull flap. When the ridges are of soft
plastic and constructed so that they bend or collapse, then (b) is
practiced so that the ridges bend or collapse so as to provide a
wedging action holding the shank between the skull and skull flap.
When the ridges are of hard plastic or metal and are constructed so
that they can cut locking grooves into the bone, then (b) is
practiced so as to cut locking grooves in the skull and skull flap
so as to lock the shank in place therebetween. When a locking
element has a plurality of substantially axially extending force
concentrating projections, then (d) is practiced so as to cause the
force concentrating projection to engage at least one of the skull
and skull flap to enhance securement of the locking element to the
skull and/or skull flap. Preferably (d) is practiced so that the
force concentrating elements operatively engage both the skull and
skull flap.
[0009] According to another aspect of the present invention there
is provided a fastener system comprising: A fastener element of
bio-compatible radiolucent rigid plastic material comprising a
substantially disc shaped head and a shank. The shank having a
plurality of ratchet teeth thereon, and a thickness of about 7 mm
or less. A substantially disc shaped lock of bio-compatible
radiolucent plastic material having a through extending opening
into at least one locking tooth defining at least part of the
opening, the at least one locking tooth cooperating with the
ratchet teeth to allow the shank to pass through the opening so
that the head and lock can be forced toward each other, but not
allowing movement away from each other. And, wherein the lock
element has first and second faces, and a plurality of force
concentrating projections extending outwardly from the first face,
toward the head in use. The details of the first concentrating
projections may be as set forth above.
[0010] According to another aspect of the present invention there
is provided a fastener system comprising: A fastener element of
bio-compatible radiolucent rigid plastic material comprising a
substantially disc shaped head and a shank. The shank having a
plurality of ratchet teeth thereon, and a thickness of about 7 mm
or less. A substantially disc shaped lock of bio-compatible
radiolucent plastic material having a through extending opening
into at least one locking tooth defining at least part of the
opening, the at least one locking tooth cooperating with the
ratchet teeth to allow the shank to pass through the opening so
that the head and lock can be forced toward each other, but not
allowing movement away from each other. And, wherein the head has a
plurality of resilient outrigger leaves.
[0011] For example in the fastening system set forth above, the
shank has a plurality of ridges substantially abutting the head and
extending substantially perpendicular to the ratchet teeth a
distance of about 3-7 mm from the head; and typically the shank
itself has a thickness of about 1-1.5 mm, and the shank including
the ridges has a thickness of about 2-5 mm.
[0012] According to yet another aspect of the present invention
there is provided a fastener system comprising: A fastener element
of bio-compatible radiolucent rigid plastic material comprising a
substantially disc shaped head and a shank. The shank having a
plurality of ratchet teeth thereon, and a thickness of about 7 mm
or less. A substantially disc shaped lock of bio-compatible
radiolucent plastic material having a through extending opening
into at least one locking tooth defining at least part of the
opening, the at least one locking tooth cooperating with the
ratchet teeth to allow the shank to pass through the opening so
that the head and lock can be forced toward each other, but not
allowing movement away from each other. And, wherein the shank has
first and second exterior side walls extending over a portion of
the length thereof including past at least some of the ratchet
teeth; and wherein the locking element opening has first and second
side portions for receiving the side walls. In this embodiment
typically the side walls extend past the first and second shank
surfaces a distance approximately equal to the height of the
ratchet teeth, e.g. the total thickness of the shank at the side
walls is about 2 mm.
[0013] It is the primary object of the present invention to provide
an enhanced fastening system, and method of utilization thereof,
particularly suitable for reattaching a skull flap in a skull after
brain surgery. However the invention has other uses in association
with other bones and suitable medical procedures. This and other
objects of the invention will become clear from an inspection of
the detailed description of the invention and from the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a greatly enlarged side view of one embodiment of
an exemplary fastener element according to the present
invention;
[0015] FIG. 2 is a detail view of the fastener element of FIG. 1
with the side walls removed for clarity of illustration of the
ratchet teeth and perpendicular ridges;
[0016] FIG. 3 is a top plan view of the fastener element of FIG.
1;
[0017] FIG. 4 is a cross-sectional view of the fastener element of
FIG. 3 taken along lines 4-4 thereof;
[0018] FIG. 5 is an end view of an exemplary locking element
utilizable with the fastener of FIG. 1, according to the present
invention;
[0019] FIG. 6 is a longitudinal cross-sectional view of the locking
element of FIG. 5;
[0020] FIG. 7 is a side schematic view, with the skull and skull
flap shown in cross-section and the fastening system in elevation,
of the utilization of the fastener element of FIG. 1 and the
locking element of FIG. 5 to hold the skull flap in place with
respect to the surrounding skull;
[0021] FIG. 8 is a detail schematic view showing the action of one
embodiment of ridges of the fastener element in providing a wedging
action when utilized in the manner illustrated in FIG. 7;
[0022] FIG. 9 is a view like that of FIG. 8 only showing different
ridges which cut grooves in the surrounding bone when utilized in
the manner illustrated in FIG. 7;
[0023] FIG. 10 is a top plan view of the head of a second
embodiment of fastener element according to the present invention;
and
[0024] FIG. 11 is a side schematic view of a portion of the head of
FIG. 10 particularly showing curvature of the resilient outrigger
leaves thereof.
DETAILED DESCRIPTION OF THE DRAWINGS
[0025] For the exemplary embodiment of the fastener element 10 of
the fastening system according to the present invention (shown
schematically at 11 in use, in FIG. 7), where features are the same
as in U.S. Pat. No. 6,022,351 they are not explained in detail
herein, but rather reference is made to the U.S. Pat. No. 6,022,351
(which has been incorporated by reference herein).
[0026] The fastening element 10 of FIGS. 1 through 4 includes a
shank portion 12 which typically has a thickness of about 1-2 mm,
preferably about 1 mm, and substantially flat first and second
surfaces 13,14. The shank 12 is integral with a substantially
disc-shaped head 15, and ratchet teeth 16 extend upwardly from one,
and preferably both, surfaces 13,14 as seen most clearly in FIGS. 1
and 2. Closer to the head 15, where the ratchet teeth 16 must
operatively engage and provide a clamping action with the locking
element shown generally at 17 in FIGS. 5 through 7, the ratchet
teeth 16 are spaced immediately adjacent each other, whereas in the
portion of the shank 12 indicated by reference numeral 18 in FIGS.
1 and 3 the ratchet teeth may be spaced much more widely from each
other, the widely spaced ratchet teeth being shown generally by
reference numeral 19. For the section 18 of the shank 12 the
ratchet teeth 19 merely provide a mechanism to prevent the locking
element 17 from falling off of the fastener element 10 during use
or handling but do not provide a clamping action, as is provided by
the teeth 16 on the portion of the shank 12 closer to the head
15.
[0027] According to the present invention adjacent the head 15 a
plurality of ridges 20 are provided upwardly extending from at
least one of the surfaces 13,14, and preferably extending upwardly
from both of the surfaces 13,14. The ridges 20 may abut the head
15, as illustrated in FIGS. 1 through 3, and extend substantially
perpendicular to the ratchet teeth 16, that is extend in the
dimension of elongation of the shank 12. The ridges 20 are
preferably substantially parallel to each other, and between two
and six ridges are typically provided extending upwardly from each
of the surfaces of 13,14. The ridges 20 preferably extend a
distance (have a length) 21 from the head 15 which is between about
3-7 mm, e.g. about 5 mm. The distance may depend upon the thickness
of the skull with which the fastener system 11 is utilized. The
dimension 22 from the top of one ridge 20 extending from the
surface 13 to the top of an aligned ridge 20 extending from the
surface 14 is typically about 2-5 mm, preferably about 3 mm. The
distance 22 will depend upon the particular materials of which the
ridges 20 are made, and the spacing between the skull flap and
skull during a brain operation.
[0028] In the embodiment illustrated in FIGS. 1 through 4 the
fastener element 10 also preferably has exterior side walls 24 (cut
away in FIG. 2) each of which has a height that is greater than the
thickness of the shank 12; for example if the thickness of the
shank 12 is about 1 mm, the height of each of the walls 24 is about
2 mm. The side walls 24 typically have a height that is less than
the height (distance 22) of the ridges 20; for example if the side
walls 24 have a height of about 2 mm the distance 22 is about 3
mm.
[0029] The substantially disc-shaped locking element 17 of FIGS. 5
and 6 has a slightly different construction than the corresponding
locking element in U.S. Pat. No. 6,022,351. The substantially
disc-shaped locking element 17 has a first surface 27 and a second
surface 28. The one or more locking teeth 29 extend outwardly from
the surface 27, adjacent the through-extending opening 30. Also
extending outwardly from the surface 27, preferably around the
periphery of the disc forming the locking element 17 (as seen in
FIGS. 5 and 6), are a plurality of force concentrating projections
31, each of which typically has a sharp tip as illustrated in FIGS.
5 and 6. The projections 31 facilitate clamping action by providing
excellent engagement of either or both of (depending upon where the
force concentrating projections 31 are located) the skull and the
skull flap of a human or animal with which the fastening system 11
is utilized.
[0030] The opening 30 also preferably has side portions thereof
exteriorly of the locking teeth 29 that are dimensioned to receive
the side walls 24 therein, and to provide rotational stability to
the fastening system 11 so that the elements 10,17 do not have a
tendency to rotate with respect to each other.
[0031] FIG. 7 schematically illustrates one of the fastening
systems 11 in use in holding a skull flap 35 to the surrounding
bone of the skull 36. Note that the ridges 20 engage the surfaces
of the skull flap 35 and the skull 36 (preferably engaging both of
them, but engaging at least one) to provide a force holding the
shank 12 in operative engagement with the skull and the skull flap
36, 35. In the position illustrated in FIG. 7, as for the system
shown in U.S. Pat. No. 6,022,351, the shank 12 has been broken off
and the locking teeth 29 of the locking element 17 engage ratchet
teeth 16 and tightly hold the head 15 in engagement with the
substantially flat surfaces of both the skull flap 35 and skull 36,
while the force concentrating elements 31 of the locking element 17
provide secure engagement with the opposite substantially flat
faces of the skull flap 35 and skull 36. A plurality of such
fastening systems 11 are utilized, as illustrated in FIGS. 6 and 7
of the U.S. Pat. No. 6,022,351, according to the preferred
embodiment of the invention.
[0032] FIGS. 8 and 9 schematically show in detail from an end view
two alternative types of engagement that may be provided between
the teeth 20 and the skull 36 and/or skull flap 35, in the practice
of the method according to the invention utilizing the fastener
system 11. In the FIG. 8 embodiment relatively soft ridges are
utilized, which are shown by reference numeral 120, whereas in FIG.
9 relatively hard ridges are illustrated, shown generally by
reference numeral 220.
[0033] In the FIG. 8 embodiment, which is not to scale, but merely
for schematic illustrative purposes, the ridges 120 (two of which
are shown, but typically between two and six are provided
associated with each of the surfaces 13,14 of the shank 12) engage
the substantially flat surface 38 of the skull 36 which has been
cut with a bone saw during the brain operation. The ridges 120 are
much longer than they are thick, and are of relatively soft plastic
so that they have a tendency to bend or collapse, as illustrated in
FIG. 8, when inserted between the skull 36 and skull flap 35. This
bending or collapsing action illustrated in FIG. 8 provides a
wedging action which enhances the holding action of the shank 12
with respect to the skull 36 and skull flap 35 so that a
combination of this wedging action and the clamping provided by the
locking element 17 engaging the ratchet teeth 16 and the head 15
engaging the skull 36 and skull flap 35, provides a very secure
holding action, to securely hold the skull flap 35 in place.
[0034] In the embodiment illustrated in FIG. 9, the ridges 220 have
a squatter configuration and are of hard material, such as hard
plastic or metal, so that instead of bending or collapsing as
illustrated in FIG. 8, when the fastener element 10 is inserted
into place between the skull flap 35 and the skull 36, the ridges
220 actually cut grooves 39 in the bone of the skull 36 (and/or
skull flap 35), again enhancing the force holding the shank 12 in
engagement with the skull 36 and skull flap 35.
[0035] FIGS. 10 and 11 show another embodiment that the head 15 of
the fastener element 10 may have. In this embodiment the head 15
has a plurality of outrigger leaves 41 of a resilient construction
and/or material, and are preferably curved toward the face of the
head 15 from which the shank 12 extends (as seen in FIG. 11). With
this construction, as the fastener system 11 is clamped into place
as illustrated in FIG. 7, the outrigger leaves 41 are flexed, as
indicated by arrow 42 in FIG. 11, so that when the fastener system
11 is clamped in place the resilient force provided by the
outrigger leaves 41 tending to return to the curved position
illustrated in FIG. 11 enhances the clamping action provided for
the fastener 11.
[0036] In the practice of the method according to the present
invention, a plurality of fastener heads 15 with shanks 12 facing
outwardly are placed in the skull opening, inside the surface 38 of
the skull 36. Then the skull flap 35 is placed in the skull opening
so that a gap is provided between the outer periphery of the skull
flap 35 and the periphery 38 of the skull opening and the fastener
shanks 12 extend in the gap as seen in FIGS. 7 through 9, and the
ridges 20,120, 220 engage at least one of the skull 36 and the
skull flap 35 and provide a force holding the shank in operative
engagement therewith [either a wedging action by deformation of the
ridges 120 as illustrated in FIG. 8, or a cutting action as shown
for the ridges 220 in FIG. 9]. Then the lock elements 17 are placed
over the shanks 12, each lock 17 is forced toward the head 15 so
that the ratchet teeth 16 and the locking teeth 29 move with
respect to each other until the head 15 and lock element 17 are
locked together holding the skull flap 35 in a position closing the
skull opening (as seen in FIG. 7). Once element 17 moves past a
tooth 16 it cannot move backwardly over it again. Then one removes
substantially all of the shank 12 portions extending outwardly from
the lock element 17, such as by clipping or in other manners
described in U.S. Pat. No. 6,022,351.
[0037] Each of the ranges described herein also specifically
includes all smaller ranges within a broad range. For example the
dimension of 2-5 mm for the combined height of the ridges 20 and
shank 12 (the distance 22) specifically includes 2.5-3.1 mm,
3.1-4.2 mm, and all other narrower ranges within the about 2-5 mm
range.
[0038] It will thus be seen that according to the present invention
an improved fastening system and method of reattaching a skull flap
are provided. While the invention has been herein shown and
described in what is presently conceived to be the most practical
and preferred embodiment thereof it will be apparent to those of
ordinary skill in the art that many modifications may be made
thereof within the scope of the invention, which scope is to be
accorded the broadest interpretation of the appended claims so as
to encompass all equivalent structures and methods.
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