Note: Descriptions are shown in the official language in which they were submitted.
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SPINAL CANAL NEEDLE
Technical Field: This invention relates to an improved needle for use in
administering anesthetics, analgesic medications, and the like into the spinal
canal
through the dura of the spinal cord into the subarachnoid space.
Background Art: When administering anesthetics, analgesic medications,
and the like into the subarachnoid space of the spinal canal, care must be
taken not
to traumatize the fibers of the dura and to cause minimal loss of
cerebrospinal fluid
with each puncture of the dura. It is well established that the loss of
cerebrospinal
fluid produces extremely severe spinal headaches.
When administering anesthetics into the subarachnoid space by means of
spinal needles, it may be necessary to maintain the patient in a horizontal
position
during the procedure. It may also require the patient to have multiple
punctures to
the dura to gain access to the subarachnoid space with each puncture
increasing the
likelihood of the loss of cerebrospinal fluid with the attendant severe spinal
headache.
Many spinal needles have a sharp point or chisel-shaped sharp point wherein
the fibers of the dura are severed during each puncture procedure. The
severing of
the fibers of the dura requires a healing period before the wound is fully
closed to
prevent the escape of cerebrospinal fluid from the spinal canal. Also,
catheters
inserted through the needle may be cut or severed by the sharp edges of the
sharp
points or chisel-shaped sharp points on the end of the needles making it
difficult to
remove the catheter from the needle or causing the partially severed catheter
to
traumatize surrounding tissue.
Some spinal needles use a sharp point in combination with a short bevel on
the point. However, the use of such a spinal needle may require the needle to
be
oriented during the insertion procedure to minimize the cutting of the fibers
of the
dura. Typically, the needle would be inserted with the sharp cutting edges of
the
bevel being parallel to the longitudinal fibers of the dura. When the dura
arachnoid
membrane is punctured with such a needle, a distinct dural snap is readily
discernable. Such a spinal needle decreases the chance of extradural injection
of
any local anesthetic but punches a relatively large hole in the dura with the
attendant
loss of spinal fluid when the needle is withdrawn and the accompanying
headache.
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Yet other types of spinal needles use a short bevel and an associated orifice
on the cannula which is occluded by the stylet in attempt to facilitate
unidirectional
flow of an anesthetic into the subarachnoid space. However, the bevel on such
needles do not have any significant effect on the spread of local anesthetics.
5 Another type of spinal needle has a sharp point with a completely rounded
non-cutting bevel like a pencil point. The tip on such a needle is solid with
a distal
orifice on one side of the cannula. A fitted stylet, when installed, occludes
the
distal orifice. The advantage of such a needle is the production of smaller
dural
puncture holes as the pencil point will separate rather than cut the
longitudinal dural
fibers. However, such a needle has the disadvantages of resistance to the
injection
of local anesthetic because the exit hole is smaller than the lumen of the
needle, the
stylet does not traverse the exit hole making it hard to clear if occluded,
the sharp
point is easily damaged, and the dural snap during insertion of the needle is
absent
making it difficult to feel when inserted.
In another needle, the cannula is beveled making a smooth junction with the
projeeting stylet therefrom. Such a needle produces a minimal dural puncture
hole.
The primary problem of such a needle is that the stylet must be unscrewed from
the
cannula before being removed thereby making it time consuming and increasing
the
possibility of dislodging the needle tip from the subarachnoid space.
Other needles utilize a relatively sharp point and a curved tip to allow the
use of plastic tubing or ureteral catheters therethrough. However, the sharp
edges
of the point cut the plastic tubing. A modified version of this needle uses a
bevel
which is shorter and blunter but a sharp stylet protrudes beyond the bevel of
the
needle which is intended to facilitate the passage of the needle through the
various
ligamentous structures during insertion to the subarachnoid space.
Disclosure of Invention
The present invention is directed to an improved needle and stylet for use in
administering anesthetics, analgesic medications, and the like into the spinal
canal
through the dura of the spinal cord into the subarachnoid space. The needle
comprises a cannula including an improved point to help minimize the cutting
of
longitudinal fibers of the dura. The improved point further helps to minimize
the
cutting of any plastic tubing inserted through the needle and allows for the
removal
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of a cut plastic tube with the cannula to help prevent trauma to surrounding
tissue. If
desired, the improved needle includes a curved point to help direct the
insertion of a
plastic tube inserted through the needle in the desired direction in the
subarachnoid
space.
In accordance with the present invention, there is provided a needle for
insertion in the subarachnoid space of the human body and the like. The needle
comprises a cannula having a bore therethrough and a hub thereon, a stylet
having an
exterior diameter smaller than the bore of the cannula to allow passage
therethrough;
and a point on the cannula having substantially the same diameter as the bore
of the
cannula, a first angled surface, a horizontal surface extending from the first
angled
surface, and a second angled surface extending from one end of the horizontal
surface.
Still, in accordance with the present invention, there is also provided a
needle
for insertion in the subarachnoid space of the human body and the like. The
needle
comprises a cannula having a bore therethrough and a hub thereon, a stylet
having an
exterior diameter smaller than the bore of the cannula to allow passage
therethrough
and the cannula including a point having substantially the same diameter as
the bore
of the cannula, said cannula having a first angled surface, a horizontal
surface
extending from the first angled surface, and a second angled surface extending
from
one end of the horizontal surface, wherein said horizontal surface is
positioned at a
distance of substantially one-half of the diameter of the cannula, from the
top of the
cannula and said first angled surface is oriented at between 105 degrees and
115
degrees from the horizontal surface.
Brief Description of Drawings
Fig. 1 is a view of a first prior art needle.
Fig. 2 is a view of a second prior art needle.
Fig. 3 is side view of a first embodiment of the present invention.
Fig. 4 is a view of the end of the needle and stylet of the first embodiment
of the present invention.
Fig. 5 is Table I setting forth the various dimensions of the needle and
stylet of
the first embodiment of the present invention shown in drawing Figs. 3 and 4.
Fig. 6 is a top view of the end of the needle shown in drawing Fig. 4.
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Fig. 7 is a side view of the first embodiment of the present invention shown
in drawing Figs. 3 and 4 having a bent end or point.
Fig. 8 is a side view of the end of a second embodiment of a needle and stylet
of the present invention.
Fig. 9 is Table II setting forth the various dimensions of the needle and
stylet
of the second embodiment of the present invention shown in drawing Fig. 8.
Fig. 10 is a view of the present invention being used with a catheter which
has
been severed.
Fig. 11 is a view of the point of the stylet used in the cannula of the needle
of
the present invention.
The present invention will be better understood when the drawings are taken
in conjunction with the detailed description of the invention.
Best Mode for Carrying Out the Invention
Referring to drawing Fig. 1 the point 10 of a prior art Tuohy needle having a
Huber point with a medium bevel is shown. The Tuohy needle is shown having a
small hub and fitted stylet. The Huber point 10 with a medium bevel is formed
or
shaped to comprise an opening 12 with cutting edges 13 having a small radius
curved
portion 14 and a sharply angled or narrow v-shaped portion 16. The point
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is curved to allow any fluid being ejected therefrom to exit in a known
direction.
Typically, a slot in the hub indicates the direction of bevel. The sharp
inside edge
of the bevel increases the hazard of shearing of any plastic tubing or
ureteral
catheter which is used with the needle, particularly, if it is attempted to
withdraw
5 the plastic tubing or catheter without first removing the needle. Even when
the
edge is blunted, the problem remains. The purpose of the Huber point is to
direct
the spinal catheter or vinyl tubing in the desired direction and to help
prevent
impingement of these catheters on various subarachnoid structures and to
facilitate
the passage of the catheters in the desired direction in the subarachnoid
space.
10 Referring to drawing Fig. 2, a modified Tuohy needle is shown. The
modified Tuohy needle is commonly known as the Tuohy-Flowers needle. The
Tuohy-Flowers needle includes a shorter and blunter bevel 20 than that of the
standard Tuohy needle but a sharp stylet 22 protrudes beyond the bevel of the
needle which is intended to facilitate the passage of the needle through the
various
ligamentous structures en route to the subarachnoid space. While the bevel is
shorter and blunter than the standard Tuohy needle, the bevel still exhibits
the same
problem of shearing plastic tubing or catheters inserted therethrough by its
sharp
edges.
Referring to drawing Fig. 3 the needle 30 of the present invention is shown.
The needle 30 comprises a cannula 32 and stylet 34. Both the cannula 32 and
stylet
34 include hubs 36 and 38 respectively. The cannula is of any desired length,
preferably, 8.9 centimeters (3.500 inches) plus or minus 0.318 centimeters
(0.125
inches) in length. The cannula 32 also includes suitable markings 40
thereonwhich
are spaced a distance of 1.0 centimeter (0.394 inches) plus or minus 0.076
centimeters (0.030 inches) from the end or point of the cannula and spaced 1.0
centimeters (0.394 inches) plus or minus 0.0254 centimeters (0.010 inches) in
between markings to assist in the location of the cannula in use. The cannula
is
formed having the end shape or point 42 thereon. The stylet is formed having
its
own end shape or point thereon which differs from that of the cannula. The
cannula.
and stylet can be made of any suitable material. =
Referring to drawing Fig. 4 the point 42 of the cannula and stylet is shown
in a first embodiment. The point 42 of the cannula or stylet includes a first
angled
surface 46, horizontal surface 48, and second angled surface 50. The first
angled
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surface 46 is formed at an angle of 110 degrees plus or minus 5 degrees from
the
horizontal surface 48. The second angled surface 50 is formed at an angle of
45
degrees plus or minus 5 degrees from either the exterior surface of the
cannula or
the horizontal surface 48.
Referring to drawing Fig. 5, Table I sets forth the various dimensions of the
A Dimension (A Dim.) and B Dimension (B Dim.) shown on Fig. 4 as well as their
relationship to the cannula internal diameter (Cann. I.D.), cannula external
diameter
(Cann. O.D.), and the stylet diameter (STY. WIIZE DIA.). All the dimensions
shown in Table I are both in inches and in centimeters. As shown, the various
dimensions of Table I relate to various gauge needles where the needles have
varying wall thickness; i. e. , the gauges being 17, 16 or 15 gauge. As can be
seen,
each of the various gauge needles set forth in Table I has an A Dimension (A
Dim.)
of fifty five percent (55 lo ) of the exterior diameter of the cannula
(CANNULA
O.D.). Also, as shown, each of the various gauge needles set forth in Table I
has a
B Dimension (B Dim.) of 0.279 centimeters (0.110 inches). Both the A Dimension
(A Dim.) and B Dimension (B Dim.) have a tolerance of 0.00635 centimeters
(0.0025 inches). To eliminate sharp edges on the point 42 of the cannula all
edges
and angles of the point 42 are buffed or abrasion blasted to eliminate
potential
cutting surfaces for cutting any plastic tubing or catheters inserted
therethrough.
This buffing or abrasion blasting leaves a dull finish on the point of the
cannula.
Referring to drawing Fig. 6, the point 42 of the cannula 32 is shown in a top
view. As can be seen, the point 42 is formed without any portion thereof being
smaller diameter than the internal diameter of the cannula 32 to prevent the
point
from shearing or cutting any plastic tubing or catheter inserted therethrough.
Also,
since the point 42 and all the edges thereof have been buffed or abrasion
blasted to
remove any sharp cutting edges, the point 42 additionally helps prevent any
cutting
of any plastic tubing or catheter inserted therethrough.
Referring to drawing Fig. 7, a modified cannula 32 is shown having a bent
end or point 42 thereon. The axis of the point 42 may be at any desired angle
with
respect to the axis of the cannula, such as approximately thirty (30) degrees
as
shown, to assist in the placement of any plastic tubing or cannula inserted
therethrough into the subarachnoid space.
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Referring to drawing Fig. 8, a second embodiment of the present invention
is shown. The point 52 of a cannula 32 includes a first angled surface 56,
horizontal surface 58, and second angled surface 60. The first angled surface
56 is
formed at an angle of 105 degrees with respect to the horizontal surface 58.
The
horizontal surface 58 is located at a position of one-half of the cannula
external
diameter. The length of the horizontal surface 58 is two and one-half times
the
external diameter of the cannula. The second angled surface 60 is formed at an
angle of forty five (45) degrees with respect to the exterior surface of the
cannula or
one hundred and thirty five (135) degrees to the horizontal surface 58, as
shown in
the previous embodiment of the invention. Both angles having a tolerance of
plus
or minus five (5) degrees.
Referring to drawing Fig. 9, Table II sets forth the various dimensions of the
point 52 as shown in Fig. 8 for the various sizes of the cannula as shown and
discussed hereinbefore with respect to drawing Fig. 5 and the point 42.
Referring to drawing Fig. 10, a portion of plastic tubing or catheter 100 is
shown having a cut 102 therein producing a fish hook 104. Also shown (in
phantom) is the cannula 32 including a point thereon, either point 42 or 52
described hereinbefore of the present invention, in relation to the plastic
tubing or
catheter 100. The prior art spinal needles shown in either drawing Fig. 1 or 2
prevent the cut plastic tubing or catheter from being pulled back through the
needle
because the fish hook 104 on the plastic tubing or catheter 100 is caught on
the
smaller portion 16 of the bevel or point 10. The sharp edges of the bevel 10
also
may cut the plastic tubing or catheter during use. With the present invention,
since
the shape of the point 42 or 52 does not obstruct the bore of the cannula, the
plastic
tubing or catheter 100 may be removed by pulling it through the bore of the
cannula
by first rotating the cannula until the cut 102 and fish hook 104 of the
plastic tubing
or catheter is covered by a portion of the point 42 or 52 as shown on the
right side
view of drawing Fig. 10. In this manner the cut is covered by a portion of the
point 42 or 52 as well as the fish hook 104 being retained within the cannula
32
thereby facilitating the removal of the plastic tubing or catheter 100. This
also
protects any surrounding tissue from being traumatized by the fish hook 104 on
the
plastic tubing or catheter 100. In contrast, the prior art needle shown in
drawing
Figs. 1 and 2 only allows the withdrawal of the cannula and the plastic tubing
or
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catheter together as the fish hook 104 on the plastic tubing or catheter 100
will hang
in the point 10 and any surrounding tissue may be traumatized by the fish hook
104.
Referring to drawing Fig. 11, the point of the stylet 34 used in the present
invention is shown. The stylet body 70 is formed having a point 72 which
includes
an angled surface 74 formed at an angle of fifteen (15) degrees with respect
to the
exterior diameter of the body 70. The angle has a tolerance of plus or minus
five
(5) degrees. In this manner the point 72 of the stylet 34 includes a
relatively long
flat surface thereon which does not interfere with the point 42 on the cannula
32 of
the needle 30 during insertion thereof.
It should be recognized and understood that the needle of the present
invention offers significant advantages over prior art needles. The needle of
the
present invention includes a cannula having a point having, in turn, an
unobstructed
bore therethrough. The point of the cannula has no sharp edges to minimize any
trauma to tissue and/or cutting of any tubing or catheter inserted
therethrough. The
point of the cannula easily separates with minimal trauma the longitudinal
fibers of
the dura and yields a distinct dural snap upon insertion. The point of the
cannula
allows easy insertion of tubing or a catheter therethrough with its subsequent
direction into the subarachnoid space. The cannula further allows the ready
removal of any cut tubing or catheter with minimal trauma to surrounding
tissue.
Having described the invention it will be obvious that changes, additions,
deletions, and substitutions may be made which fall within the scope of the
claimed
invention.
