Spinal needle abstract
The present invention discloses a method for producing a multi-lumen
needle suitable for administrating spinal anesthesia. The method
will provide a needle that will allow the simultaneous administration
of spinal and epidural anesthetic from a single site. A preferred
needle made by this method can optionally be made with a stock configuration
which has means for holding a catheter during the insertion of a
spinal needle and is configured so as to provide gripping sites
to assist in positioning the needle. The preferred needle of the
present invention has a lumen which can serve as a spinal introducer.
The introducer lumen sheaths the spinal needle until the spinal
needle is in the epidural space. This assures that the spinal needle
will not be bent or fractured in use by impingement with bone or
Spinal needle claims
What I claim is:
1. An improved epidural-spinal needle having an epidural lumen
bounded by epidural tubing which is larger than and joined along
a line of contact to introducer tubing bounding an introducer lumen,
the tubes forming a straight needle body having a direction of insertion
parallel to the lumen axes, the improvement comprising:
a tip region where the lumen axes are curved in the plane defined
by the lumen axes, the epidural lumen being convex with respect
to the introducer lumen;
a first piercing surface terminating the epidural lumen, said first
piercing surface being inclined with respect to the direction of
insertion by an angle sigma and intersecting the line of contact
at a first piercing point; and
a second piercing surface terminating the introducer lumen being
inclined with respect to the direction of insertion by an angle
delta and intersecting the line of contact at a second piercing
point, said first piercing point and said second piercing point
being nearly coincident and forming a vertex.
2. The improved needle of claim 1 wherein said axes are curved
such that the minimum radius of curvature of the needle tip is between
about 1/2 and 5/8 inches, sigma is less than 30 Deg. and said vertex
is located at a distance from a line defined by the line of contact
of the needle
body which is greater or equal to the radius of the epidural tube.
3. The improved needle of claim 2 wherein sigma is less than about
30 Deg. and sigma plus delta is greater than about 40 Deg. and less
than 60 Deg.
4. The improved needle of claim 3 wherein delta is not greater
than about twice sigma.
5. The improved needle of claim 4 wherein said first piercing surface
extends beyond the needle body by not more than four times the thickness
of the wall of said epidural tubing.
6. The improved needle of claim 5 wherein said second piercing
surface is tangent to said line of contact at said vertex.
7. An improved needle stock for a epidural-spinal needle having
a bonded region where an epidural lumen and an introducer lumen
are bonded and an unbonded region where the lumina diverge, the
a face plate having first reference surface with a first passage
there through and a second reference surface with a second passage
there through, said second reference surface being inclined with
respect to the first reference surface such that the epidural lumen
will pass through said first reference surface substantially normal
to said first reference surface and the introducer lumen will pass
through said second reference surface substantially normal to said
second reference surface.
8. The needle stock of claim 7 further comprising:
a central support rib attached to face plate and which provides
for encasement of the diverging lumina.
9. The needle stock of claim 8 further comprising:
a stop engaging the bonded region of the needle and attached to
the support rib.
10. The needle stock of claim 9 further comprising:
extensions providing gripping surfaces attached to said first reference
surface and symmetrically disposed about the epidural lumen; and
tabs attached to said second reference surface of the stock.
11. The needle stock of claim 10 further comprising:
means for holding a catheter to said face plate, said means for
holding a catheter to said face plate being attached to said face
12. The needle stock of claim 10 wherein said tabs attached to
said second reference surface are contoured to be gripped by a finger
13. The needle stock of claim 7 further comprising:
a fillet spaced apart from said face plate for engaging the epidural
tubing and the introducer tubing where divergence of the lumen begins.
14. The needle stock of claim 13 further comprising:
means for holding a catheter to said face plate, said means for
holding a catheter to said face plate being attached to said face
15. A method for manufacturing a epidural-spinal needle comprising
the steps of:
aligning epidural tubing having an epidural lumen with introducer
tubing having an introducer lumen in a side by side relationship
so as to form a line of contact between said first epidural tubing
and said introducer tubing;
bonding along the line of contact for a distance sufficient to
form a needle blank having a tip end, a needle body, and an unbonded
region, said line of contact in said needle body defining the needle
bending said tip region of said needle blank in the plane defined
by the axes of said lumen such that after bending said epidural
lumen is convex with respect to said introducer lumen;
cutting a first piercing surface intersecting the epidural tubing
inclined by an angle sigma to said insertion direction where sigma
is less than 30 Deg.; and
cutting a second piercing surface intersection the introducer tubing
inclined to said insertion direction by an angle delta.
16. The method of claim 15 wherein said first piercing surface
terminates in a first piercing point and said second piercing surface
terminates in a second piercing point, said first piercing point
and said second piercing point are nearly coincident, and the sum
of sigma plus delta is greater than 40 Deg. and less than 60 Deg.
17. The method of claim 16 further comprising the steps of:
bending the tubing of the unbonded segment so as to provide a divergence
of at least 10 Deg. in the unbonded tubing;
engaging said diverging tube segments with a faceplate; and
attaching hubs to said diverging tube segments
18. The method of claim 17 wherein said method of bonding is selected
from the group of electron beam welding and laser welding, and further
wherein the method of cutting is selected from the methods of electrodeposition
cutting and electrochemical grinding.
Spinal needle description
Punctures of the spinal area are required in conjunction with a
variety of medical and surgical procedures. Frequently medication,
and in particular, epidural and spinal anesthetics must be introduced
through a needle or a catheter. It may be desirable to both introduce
medication in the vicinity of the puncture through a spinal needle
and to introduce medication through a catheter to a location remote
from the puncture in the epidural or spinal spaces.
Using prior art techniques, multiple punctures would have to be
made for simultaneous introduction of an epidural catheter and a
spinal needle, or for the introduction of two epidural and/or spinal
catheters. Multiple spinal punctures have greater risk than a single
puncture because of the increased trauma from additional punctures
and because the time required to perform the procedure must be extended.
Spinal anesthesia frequently requires the initial administration
of small quantities of an anesthetic agent into the subarachiod
space. Since spinal anesthesia may be effective for only short periods
of time, an adjunctive epidural anesthetic technique that can be
continuous may be required for longer surgical procedures. Alternatively,
either continuous epidural or spinal techniques must be utilized.
The epidural technique yields a less dense local anesthetic block,
while the spinal technique can lead to equally undesirable consequences
including post spinal headache. Significant advantages could be
obtained if the epidural and spinal procedures could be combined.
A procedure using conventional prior art single lumen needles to
administer the spinal and epidural anesthetic requires the procedures
either be performed at separate sites, or the two procedures be
separated by a time interval. It would be advantageous and would
reduce trauma if both procedures could be carried out nearly simultaneously
at the same site utilizing small gauge spinal needles. If both procedures
were carried out simultaneously utilizing one puncture the length
of the procedure, and the discomfort to the patient would be reduced.
One option for using a single needle is to use a needle to locate
the epidural space and then to insert a spinal needle through the
needle to such an extent that the spinal needle penetrates the dura.
An anesthetic agent can then be administered through the spinal
needle. The spinal needle can then be withdrawn, leaving the needle
in position for use in introduction of an epidural catheter in the
usual way. This technique may have a significant risk in that the
epidural catheter will pass into the space through the perforation
and be undetected. Also the immediate epidural catheterization is
If a single needle is not used for the administration of the spinal
and epidural anesthetic, but rather multiple needles are used, multiple
punctures must be made in separate locations. One puncture is used
for the insertion of, and to guide the spinal needle while the other
puncture is used for the introduction of a catheter or for the introduction
of a second needle.
If combined spinal and epidural anesthesia is to be used, the time
to complete the epidural must be minimized once the spinal anesthetic
is injected since a dangerous situation may occur such as serious
drops in blood pressure and/or pulse rate once the spinal anesthetic
has been administered. This dangerous situation may arise during
performance of the epidural catheterization since using prior art
techniques epidural catheterization must be performed subsequent
to the spinal anesthetic injection unless multiple needles and multiple
punctures are used.
The above mentioned problems have been largely over come by an
epidural-spinal needle which is disclosed and claimed in U.S. patent
application No. 07/072428. The epidural-spinal needle is a dual
lumen needle having lumen of different gauges. The larger lumen
is sized to pass a catheter and configured to direct a catheter
into and along the epidural space. The smaller lumen serves as an
introducer for a fine gauge spinal needle. The purpose of the introducer
is to assure that the fine gauge spinal needle passes into the epidural
space without being bent or fractured by bone and tissue matter
which it must pass through before entering the epidural space.
The epidural-spinal needle serves to locate and cannulate the epidural
space, introduce a spinal needle into the epidural space, introduce
a spinal or epidural catheter, or the introduction of multiple catheters
through a single puncture resolving many of the problems of the
earlier needles. It will allow for the simultaneous introduction
of one or more needles, a needle and a catheter, or multiple catheters
through a single skin puncture. Thus the epidural-spinal needle
has advantages with respect to the prior art by reducing trauma,
reducing procedure time, and providing the practitioner with a greater
flexibility regarding the positioning of the catheters and needles
for a specific procedure since the needle of the present invention
can function as an introducer.
The present invention provides a method for making the epidural-spinal
needle of the U.S. application No. 07/072428 as well as an improved
tip and stock configuration for an epidural-spinal needle.
The tip configuration of the present application further reduces
the trauma of insertion of an epidural-spinal needle, guides the
spinal needle into the epidural space without obstruction from bone
or tissue, and directs a spinal needle into the dura at an angle.
Having a skewed path through the dura wall assists the sealing of
the wall when the needle is removed and in this manner further reduces
the chance of dural headaches.
The improved stock provides reference surfaces for aligning the
catheter and spinal needle to aid in the insertion of the catheter
and spinal needle; additional grips for holding and inserting the
spinal needle; and means for holding catheters during insertion
of the spinal needle.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for
making an epidural-spinal needle.
It is another object of the invention to provide a stock for an
epidural-spinal needle contoured to provide multiple grips for inserting
and positioning the epidural-spinal needle.
It is a further object of the invention to provide a stock with
means for holding a previously inserted epidural catheter during
insertion of a spinal needle through the epidural-spinal needle.
It is still another object of the present invention to provide
reference surfaces which aid in aligning and inserting the catheter
and the spinal needle.
It is a further object of the invention to provide an introducer
for spinal needles that directs a spinal needle through the dura
wall on a skewed path thereby limiting seepage of fluids between
the dura and epidural space when a spinal needle is withdrawn from
These and other objects of the present invention will become apparent
from the following figures and description.
In making an epidural-spinal needle the appropriate gauge needle
tubing should be selected based on its intended use. The epidural
tubing should be chosen such that its larger lumen, the epidural
lumen, passes the catheter for which it will be used. Generally,
the epidural lumen tubing of the epidural-spinal needle should have
a gauge size less than 14 gauge and preferably between approximately
16 and 20 gauge and preferably about 18 gauge.
When the epidural-spinal needle serves as an introducer for very
small spinal needles of 25 to 32 gauge, the size of the smaller
or introducer tubing should be between 20 and 24 gauge and preferable
21 or 22 gauge.
Such a range of gauges will accommodate a spinal needle of between
25 and 32 gauge. The small spinal needle can in turn be used for
a spinal puncture or microcatheters can be inserted intrathecally
through the small gauge spinal needle once the dura has been punctured.
In fabricating an epidural-spinal needle, the needle tubing for
the spinal lumen and the introducer lumen are aligned such that
the axes of the lumina are parallel and the needle tubing bounding
the lumina have a line of contact. With the needle tubing so positioned
a needle blank is formed by bonding the tubing for the epidural
lumen to the tubing for the introducer lumen. Starting at the first
end which becomes the tip end, the tubing for the lumina are bonded
along the line of contact for a length sufficient to form a tip
region, a needle body, and an unbonded region. Preferably this length
will be between about 3.7 and 5.7 inches for adult patients; the
tip and needle body for adults being between about 2.5 and 4.5 inches.
The direction of insertion for the resulting needle will be parallel
to the axes of the lumina and the line of contact in the body of
the needle. The unbonded region of the needle blank forms the extensions
of the epidural lumen and the introducer lumen.
The tip region of the needle blank body is bent in the plane defined
by the lumen axes. The axis of the epidural lumen after bending
is convex with respect to the introducer lumen in the tip region.
The minimum radius of curvature of the needle tubing in the tip
region is preferably between about 1/2 and 5/8 inches.
The epidural tubing is cut in the tip region providing a first
tip piercing surface inclined with respect to the insertion direction
of the needle by an angle sigma. Preferably sigma is not more than
about 30 degrees.
The piercing surface for the epidural lumen is cut such that the
piercing surface intersects the line of contact at a first piercing
point at a distance normal to the line of contact of the lumina
for the body of the needle that is greater than the radius of the
epidural lumen tubing. It is further preferred that the first piercing
surface does not extend beyond the crown by more than about the
thickness of the epidural tubing. Where the crown is the upper intersection
of the plane containing the lumen axes the free surface of the epidural
lumen which is diametrically opposed to the line of contact of the
The first condition assures that a catheter exiting the epidural
lumen will be directed away from the direction of insertion of the
needle, while the latter condition assures that the extension of
the tip beyond the needle body will not make removal of the needle
difficult by creating a barb which will make removal of the needle
A second piercing surface for the introducer lumen is cut angle
delta with respect to the direction of insertion such that a second
piercing surface intersects the line of contact at a second piercing
point. When the method of the present invention is used to produce
the improved tip of the present invention the two piercing points
coincide forming a vertex. In this case it is preferred that the
first piercing surface and the second piercing surface intersect
at an angle theta of greater than about 40 Deg. Where theta is the
sum of sigma and delta. This minimum of the angle theta assures
that the vertex will have sufficient mass to assure its structural
integrity and will not be subject to bending or fracture during
Since the epidural lumen is larger than the introducer lumen in
the epidural-spinal needle, the limitation on the angle between
the two piercing planes in combination with the limitation on the
angle between the first piercing surface and the insertion direction
of the needle assures that the opening through which a spinal needle
exits the introducer lumen in the second piercing surface is closer
to the vertex than the opening of the first piercing surface through
which the catheter exits. This will assure that the spinal needle
will be in the epidural space before it exits the introducer and
will immediately encounter and penetrate the dura mater thereby
avoiding impingement on hard tissue such as bone, cartilage or calcified
ligaments which could bend or break a fine spinal needle.
It is further preferred that the introducer piercing surface is
tangent to the line of contact at the vertex. This condition assures
that integrity of the epidural tubing will be maintained throughout.
The limitations set forth above on the improved tip configuration
of an epidural-spinal needle will slightly skew the direction of
a spinal needle with respect to the direction of insertion. To limit
the skewness of the path of the spinal needle it is further preferred
that delta not be greater than about twice sigma. By so limiting
the skewness, the friction between a spinal needle passing through
the wall will be limited and the tactile sensing of tissue being
pierced by a spinal needle passing through the introducer lumen
will be maintained.
A divergence of the lumina in the unbonded region of the needle
stock is obtained by bending the lumina. It is preferred that the
divergence be obtained by bending the introducer lumen. Bending
the introducer lumen while maintaining the epidural lumen straight
assures that a force applied to the epidural needle tubing in the
direction of insertion of the needle will not introduce bending
moments in the epidural lumen.
A divergence of up to about 15 Deg. can readily be obtained by
bending the introducer lumen without undue resistance to a spinal
needle passing through the introducer or without loss of the tactile
sensing of tissue being pierced by a spinal needle passing through
the introducer lumen. If the introducer lumen is bent in a smooth
curved path such as a circular arc then the divergence can be substantially
increased. By using a circular arc and an angle of divergence of
25 to 30 Deg. the unbonded section of the needle can be reduced
to less than 1.25 inches, thus making the epidural-spinal needle
shorter, easier to use, and less costly to manufacture.
Support means are provided to enhance the structural rigidity of
the diverging lumen. Preferably the means have a face plate having
two passages passing there through. It is further preferred that
the face plate has a first reference surface which is normal to
the epidural lumen as it passes there through and a second reference
surface which is normal to the introducer lumen as it passes there
The first reference surface has extensions which are symmetrically
disposed about the epidural lumen and provide gripping surfaces
which allow a force to be applied in the direction of insertion
direction of the needle.
The second reference surface has tabs attached which are parallel
to the direction of insertion of the epidural needle and extending
toward the needle vertex and are preferably contoured to be gripped
by finger and thumb.
A central support rib encases the diverging lumina and attaches
to the faceplate providing additional support to the diverging lumina.
This rib terminates at the other end with a stop which engages the
Preferably the face plate has extending therefrom hubs to allow
for the attachment of one or more conventional syringes. These hubs
can be made an integral part of the needle or alternatively part
of the face plate.
In another preferred embodiment of the present invention the stock
is color coded in such a manner that needles having different sizes
and/or different point configurations can be readily distinguished.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 illustrates the spacial relationship between a section of
needle tubing having a lumen suitable for an epidural lumen and
a section of needle tubing having a lumen suitable for introducer
FIG. 2 shows a needle blank which is formed by bonding the tubing
of FIG. 1.
FIG. 3 shows the needle blank of FIG. 2 with the tip region being
formed to provide an epidural tubing which will divert a catheter
into the epidural space.
FIG. 4 illustrates the needle tip of FIG. 3 which has been cut
forming piercing surfaces for the needle point.
FIG. 5 shows a needle body terminating at one end with a needle
point which is one embodiment of the improved point of the present
invention. The other end has extensions of the epidural lumen and
the introducer lumen which diverge which are stabilized by a faceplate
and a fillet provided in the region where the two lumina meet.
FIG. 6 illustrates a cross section of the improved point of FIG.
5. The phantom lines illustrate the continuation of the epidural
and the introducer tubing before piercing surfaces are cut.
FIG. 7 shows a catheter inserted in the epidural lumen of FIG.
6 and exiting the tip. FIG. 7 also shows a spinal needle passing
through the introducer lumen.
FIG. 8 is a prospective view of an epidural-spinal needle having
a stock of a preferred embodiment of the present invention.
FIG. 9 is a side view of FIG. 8 showing the relationship of the
diverging lumina to a two part face plate.
FIG. 10 is a schematic representation of a first means for holding
a catheter at the face plate.
FIG. 11 is a schematic representation of a second means for holding
a catheter at the face plate.
FIG. 12 is a schematic representation of a third means for holding
a catheter at the face plate.
BEST MODE FOR CARRYING THE INVENTION INTO PRACTICE
In fabricating an epidural-spinal needle the appropriate gauge
needle tubing should be selected based on its intended use. The
epidural tubing should be chosen such that its lumen, the epidural
lumen, passes the catheter for which it will be used. Generally
the epidural lumen of the epidural-spinal needle should have a gauge
size less than 14 gauge and preferably between approximately 16
and 20 gauge and preferably about 18 gauge.
When the epidural-spinal needle serves as an introducer for very
small spinal needles of 25 to 32 gauge, the size of the smaller
or introducer lumen tubing should be between 20 and 24 gauge. Such
a gauge will accommodate a spinal needle of 25 to 32 gauge. The
small spinal needle can in turn be used for a spinal puncture or
microcatheters could be inserted intrathecally through the small
gauge spinal needle.
FIG. 1 illustrates the spacial relationship segments of needle
tubing having a lumen suitable for an epidural lumen and a section
of needle tubing having a lumen suitable for introducer lumen. The
larger gauge needle tubing is the epidural tubing 10 and has an
epidural lumen 12. The epidural lumen 12 has an epidural lumen axis
14. The smaller needle tubing serves as introducer needle tubing
16 and has an introducer lumen 18 which has an introducer lumen
axis 20. The epidural tubing 10 is placed in a side by side relationship
with introducer tubing 16 such that their axes are parallel and
a line of contact 22 between the tubing is established. The overall
length of the tubing sections is a function of their intended use.
Typically for needles intended to be used for adult patients this
length will be between about 2.5 and 4.5 inches.
The needle tubing segments are bonded along a segment of their
line of contact 22 to form a needle blank 24 as is illustrated in
FIG. 2. The bonded segment of the line of contact 22 starts at a
first end which initiates the tip region 26 and continues along
the line of contact 22 for a distance sufficient to form a tip region
26 and a needle body 28 leaving an unbonded region 30.
Welding is the preferred method of bonding the epidural tubing
to the introducer tubing since welding provides a strong bond and
the method can be easily automated. Electron beam welding or laser
welding are preferred methods of welding since they can be focused
to provide sharp temperature profiles and highly localized melting
needed to bond the walls of the tubing without melting through the
walls. Laser welding is further preferred if continuous tube stock
is employed since laser welding is well suited to welding intermittent
sections in continuous stock.
FIG. 3 shows the tip region 26 of the needle blank 24 of FIG. 2
being bent in the plane defined by the lumina axes (14 20) to form
a needle curved tip region 32 and leaving a straight needle body
34. It is preferred that the stylets not shown are positioned in
the lumina during bending. Preferably the needle blank 24 is bent
by employing a mandrel 36 to deform the crown 37 of the needle blank
24. The crown 37 is defined as the upper intersection of the plane
defined by the lumen axes (14 20) and the epidural lumen tubing
10 this intersection being diametrically opposed to the line of
contact 22. The mandrel 36 having a diameter such that the minimum
radius of curvature 38 of the epidural needle tubing 10 resulting
from bending will preferably be between about 1/2 and 5/8 inches.
When the tip is bent as shown, the epidural lumen axis after bending
is convex with respect to the axis 20 of the introducer lumen 18
in the tip region 32 of the needle blank 24.
The direction of insertion 39 for the resulting needle is parallel
to the line of contact 22 and the axes of the lumen in the needle
After forming the tip region 32 piercing surfaces for the lumina
are generated, preferably with stylets in the lumina. Referring
to FIG. 4 a first piercing surface 40 for the epidural lumen 12
is generated by a cutting plane 42. A second piercing surface 44
is produced by a cutting plane 46.
The first piercing surface 40 intersects the line of contact 22
at a first piercing point 48 while the second piercing point 50
results from the second piercing surface 44 intersecting the line
of contact 22. In general, the piercing points (48 50) do not coincide.
However it is preferred that the piercing points nearly coincide
due to the restricted depth of the cross section of the epidural
space. This depth is typically less than about 3 mm in lumbar spinal
innerspaces. Having the piercing points (48 50) coincide forming
a joint point 50' as illustrated in FIG. 5 assures that the epidural
lumen exit opening 51 and the introducer lumen exit opening 52 are
in close proximity to the joint point 50'.
In FIG. 5 the extensions of the epidural tubing 54 and the introducer
tubing 56 diverge in the unbonded region 58. The divergence in the
unbonded region 58 is introduced by bending the introducer tubing
56. It is preferred that the introducer tubing 56 be bent so that
it diverges with respect to the epidural tubing 54. By maintaining
the epidural tubing 54 straight a force applied to the epidural
tubing 54 in the needle insertion direction 57 will not produce
a bending moment about the epidural tubing 54. A divergence Mu of
15 Deg. can readily be obtained without loss of the tactile sensing
of tissue being pierced by a spinal needle introduced through the
introducer tubing 56. The divergence can be increased to about 30
Deg. when the curvature is gradually increased by a smooth curved
path such as a circular path of radius R.
Means for assuring structural rigidity of the divergent lumina
are attached to the diverging lumina (54 56). Preferably the support
means employs a face plate 59 having a first reference surface normal
to the epidural lumen 54 and a second reference surface normal to
the introducer lumen 56.
Details of the improved tip configuration for an epidural-spinal
needle of the present invention are shown in FIG. 6. The tip 60
which is terminated by a first plane 62 which cuts the epidural
lumen 64 at an angle sigma with respect to the direction of insertion
66 of the epidural-spinal needle. A second plane 68 cuts the introducer
lumen 70 and makes an angle delta with respect to the insertion
direction 66. The cutting planes generate an epidural piercing surface
72 and an introducer piercing surface 74 these piercing surfaces
meeting at a vertex 76. Since the epidural lumen 64 is the larger
of the two lumina, the introducer lumen 70 will terminate at a distance
d.sub.2 from the vertex 76 which is less than the distance d.sub.1
at which the epidural lumen terminates from the vertex 76 when delta
is equal to or greater than sigma.
Furthermore to assure that in the vicinity of the vertex 76 the
needle point 60 has sufficient structural integrity to withstand
the forces associated with insertion of the needle it is further
preferred that the sum of sigma plus delta be greater than 40 Deg.
An upper limit of this sum should be maintained below about 60 Deg.
so as to facilitate the insertion of the needle.
To assure that the epidural lumen provides guidance to a catheter
directing it into the epidural space the vertex 76 should be displaced
a distance d.sub.3 from the line 78 the extension of the line of
contact 78' for the needle body, where d.sub.3 is greater than the
radius r.sub.s of the epidural tubing 79.
Furthermore to facilitate removal of the epidural spinal needle
it is preferred that the first piercing surface 72 does not extend
a distance l.sub.m beyond the crown 79 of the needle body by more
than about four times the thickness t.sub.e of the epidural tubing.
FIG. 7 shows a catheter 80 positioned in the epidural lumen 82
and exiting from it with the angle Xi. This angle turns the catheter
in such a direction that it will be directed along the epidural
space assisted by the dural wall.
Since both the epidural lumen 82 and the introducer lumen 84 are
bent in the tip region 86 a spinal needle 88 when exiting the introducer
lumen 84 will be deflected in the direction of the catheter by an
angle Phi. Maintaining delta not more than about approximately twice
sigma will assure that the angle Phi will be substantially less
than Xi. Having Phi substantially less than Xi provides two benefits.
First, it assures that the spinal needle will enter the dural wall
away from the area of the wall which might be effected by the vertex
89 of the tip. Second, it assures minimum resistance to the passage
of the spinal needle 88 as it passes through the introducer lumen
84. By so limiting the resistance resulting from the passage of
the spinal needle 84 as it passes through the tip, the divergence
between the introducer lumen 84 and the epidural lumen 82 can be
increased in the unbonded region of the needle to greater than 30
Deg. when bent in a smooth curve as illustrated in FIG. 5. without
loss of the tactile response to tissue penetration by a spinal needle.
While Phi should be less than Xi having a non zero value of Phi
is beneficial for spinal taps. Having Phi non zero results in a
skewed puncture path which upon removal of the spinal needle assists
in the sealing of the wall of the dura. Sealing the wall reduces
the fluids that will transfer between the subarachoid and the epidural
space and in turn reduces the likelihood of post dural headaches.
FIGS. 8 and 9 are a perspective view and a side view of an epidural-spinal
needle of one embodiment of the stock of the present invention.
The stock 90 is a preferred means for providing structural support
for the diverging lumina to the unbonded region 58 shown in FIG.
The stock 90 has a face plate 92 having a first passage 94 through
which the epidural lumen 96 passes. Preferably a first reference
surface 98 normal to the epidural lumen 96. A second passage 100
passes through the face plate 92 which preferably has a second reference
surface 102 which is normal to the introducer lumen 104. Having
the reference surfaces (98 102) normal to their respective lumina
(96 102) provides surfaces which serve as a reference surface.
These surfaces assist in aligning catheters and spinal needles for
insertion and provide advantages in bonding the lumen to the reference
The included angle between the two reference surfaces is equal
to the divergence of the lumina at the reference surfaces since
the reference surfaces are normal to their respective lumina. The
face plate 92 is preferably provided with extensions 106 attached
to the first reference surface and symmetrically disposed around
the epidural lumen. The extensions provide gripping surfaces for
inserting the epidural-spinal needle.
A stand alone faceplate 59 as shown in FIG. 5 can serve as a means
for stabilizing the divergent lumina. However it is preferred to
employ a fillet f at the joinder of the divergent lumina as illustrated
in FIG. 5 in combination with the face plate 59. A central support
rib 108 to encase the diverging lumina (96 104) and attaches to
the faceplate 92 is preferred to provide additional support to the
diverging lumina (96 104). A stop 110 attaches the support rib
and engages the epidural-spinal needle body 112.
The second reference surface 102 preferably has tabs 114 attached
extending toward the needle vertex 116 and are preferably contoured
to be gripped by finger and thumb.
Preferably the faceplate has extending therefrom hubs 118 for the
attachment of one or more conventional syringes. These hubs can
be made an integral part of the needle or alternatively part of
the face plate.
FIGS. 10 11 and 12 illustrate various means for holding a catheter
to a face plate 92 when a spinal needle is being inserted. FIG.
10 illustrates notches in the face plate 122 into which a catheter
124 can be placed. FIG. 11 illustrates loops 126 for holding the
catheter 124. While FIG. 12 shows the catheter being held by a knob
and hook 128.