U.S. patent application number 11/077884 was filed with the patent office on 2005-06-30 for method of forming a lead.
Invention is credited to Black, Damon Ray, Daglow, Terry, Erickson, John, Jones, Robert Earl, Lauro, B. Reno.
Application Number | 20050138791 11/077884 |
Document ID | / |
Family ID | 23155898 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050138791 |
Kind Code |
A1 |
Black, Damon Ray ; et
al. |
June 30, 2005 |
Method of forming a lead
Abstract
An implantable, substantially isodiametric, low resistance
implantable lead having at least one electrode positioned in a
stimulation/sensing portion of the lead as well as a method of
manufacturing the same. At least the stimulation/sensing portion is
unitized through partially surrounding and supporting insulation
and conductive element(s) of the stimulation/sensing portion with a
fused matrix of material having mechanical properties consistent
with a body of the lead.
Inventors: |
Black, Damon Ray; (Dallas,
TX) ; Daglow, Terry; (Allen, TX) ; Erickson,
John; (Plano, TX) ; Jones, Robert Earl;
(Wylie, TX) ; Lauro, B. Reno; (Murphy,
TX) |
Correspondence
Address: |
DOCKET CLERK, DM/ANSI
P.O. BOX 802432
DALLAS
TX
75380
US
|
Family ID: |
23155898 |
Appl. No.: |
11/077884 |
Filed: |
March 11, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11077884 |
Mar 11, 2005 |
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10042992 |
Jan 9, 2002 |
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10042992 |
Jan 9, 2002 |
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09760437 |
Jan 12, 2001 |
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09760437 |
Jan 12, 2001 |
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09299702 |
Apr 26, 1999 |
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6216045 |
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Current U.S.
Class: |
29/592.1 |
Current CPC
Class: |
Y10T 29/49002 20150115;
H01R 43/00 20130101; A61N 1/0551 20130101; Y10T 29/49174 20150115;
Y10T 29/4922 20150115; Y10T 29/49208 20150115; Y10T 29/49204
20150115; A61N 1/056 20130101; Y10T 29/49176 20150115; A61N 1/05
20130101; Y10T 29/49117 20150115 |
Class at
Publication: |
029/592.1 |
International
Class: |
A61N 001/00 |
Claims
1-14. (canceled)
15. An implantable lead comprising: a lead body having a distal end
and a proximal end having a terminal, wherein the lead body is
formed of a material having prescribed mechanical properties; a
first region extending proximally from the proximal end of the lead
body, wherein the first region includes at least one terminal, and
when the implantable lead includes a plurality of terminals,
adjacent terminals are separated by a first insulative material
having mechanical properties consistent with the material of the
lead body; at least one conductor electrically coupled to the at
least one terminal, and wherein in addition to the at least one
conductor, a first portion of an interior passage of the first
region is substantially filled with a second insulative material
having mechanical properties consistent with the material of the
lead body.
16. An implantable lead in accordance with claim 15 wherein the
first insulative material and the second insulative material are
the same.
17. An implantable lead in accordance with claim 15 wherein the
first insulative material, the second insulative material, and the
material of the lead body are the same.
18. An implantable lead in accordance with claim 15 wherein the at
least one conductor is formed of stranded wire and has a resistance
equal to or less than 25 ohms for a conductor length equal to or
less than 60 cm.
19. An implantable lead in accordance with claim 15 wherein an
outer diameter of the lead body is approximately 0.05 inches.
20. An implantable lead in accordance with claim 15 further
comprising a stylet guide, positioned within a second portion of
the interior passage defined by the lead body and the first
region.
21. An implantable lead in accordance with claim 15 wherein the
implantable lead is substantially isodiametric.
22. An implantable lead in accordance with claim 15 wherein the
second material is a fused matrix.
23. An implantable lead in accordance with claim 15 wherein the at
least one conductor passes through the lead body and the first
region.
24. An implantable lead in accordance with claim 23 wherein the
interior passage is also defined within a second region extending
proximally from the proximal end of the lead body, and in addition
to the at least one conductor, the interior passage of the second
region is substantially filled with a third insulative material
having mechanical properties consistent with the material of the
lead body.
25. An implantable lead in accordance with claim 24 wherein the
first insulative material, the second insulative material, and the
material of the lead body are the same.
26. An implantable lead in accordance with claim 15 wherein a
second region extends distally from the distal end of the lead
body, wherein the second region includes a plurality of electrodes,
and adjacent electrodes are separated by a third insulative
material having mechanical properties consistent with the material
of the lead body.
27. An implantable lead in accordance with claim 26 wherein the at
least one conductor is electrically coupled to at least one
corresponding electrode of the plurality of electrodes.
28. An implantable lead in accordance with claim 15 wherein each
conductor extends along at least one interior passage of the lead
body.
29. An implantable lead in accordance with claim 15 wherein the
corresponding terminal is joined to the at least one conductor by a
laser weld.
30. An implantable lead in accordance with claim 15 wherein the
plurality of terminals equals eight.
31. An implantable lead comprising: a lead body having a distal end
and a proximal end having a terminal, wherein the lead body is
formed of a material having prescribed mechanical properties; a
first region extending distally from the distal end of the lead
body, wherein the first region includes a plurality of terminals,
and adjacent terminals are separated by a first insulative material
having mechanical properties consistent with the material of the
lead body; at least one conductor electrically coupling at least
one of the plurality of terminals with at least one corresponding
electrode of the plurality of electrodes, wherein the at least one
conductor extends through at least a portion of each of the lead
body and the first region; and wherein the material(s) forming the
first region has mechanical properties consistent with the material
of the lead body.
32. An implantable lead in accordance with claim 31 wherein the
material(s) forming the first region, which supports the plurality
of terminals and carries the at least one conductor, is a fused
matrix.
33. An implantable lead in accordance with claim 31, wherein each
of the plurality of conductors extends along the lead body.
34. An implantable lead in accordance of claim 31, wherein the
electrodes are located at a second region extending distally from
the distal end of the lead body.
35. An implantable lead comprising: a lead body having a distal end
and a proximal end having a terminal, wherein the lead body is
formed of a material having prescribed mechanical properties; a
stimulation portion extending distally from the distal end of the
lead body, wherein the stimulation portion includes a plurality of
electrodes, and adjacent electrodes are separated by an insulative
material having mechanical properties consistent with the material
of the lead body; at least one conductor electrically coupling the
terminal with at least one corresponding electrode of the plurality
of electrodes, wherein the at least one conductor extends through
at least a portion of each of the lead body and the stimulation
portion; and wherein at least the stimulation portion is formed
from a substantially solid, fused matrix of materials having
consistent mechanical characteristics, and the fused matrix of
material(s) supports the plurality of electrodes and the at least
one conductor extends at least partially therethrough.
Description
RELATED APPLICATIONS
[0001] This is a division of U.S. patent application Ser. No.
09/760,437, filed Jan. 12, 2001, pending, which is a division of
U.S. patent application Ser. No. 09/299,702, filed Apr. 26, 1999,
issued as U.S. Pat. No. 6,216,045.
FIELD OF THE INVENTION
[0002] The present invention relates to a lead, and in particular,
to an implantable lead and a method of manufacturing such lead.
BACKGROUND OF THE INVENTION
[0003] Implantable leads having ring electrodes can be used in a
variety of applications, including delivery of electrical
stimulation to surrounding tissue, neural or otherwise, as well as
measuring electrical energy produced by such tissue. Whether
serving in a stimulation capacity or a sensing capacity, such leads
are commonly implanted along peripheral nerves, within the epidural
or the intrathecal spaces of the spinal column, about the heart,
and in the brain.
[0004] Notwithstanding the application, the common requirements for
such implantable leads include flexibility, strength, and
durability. The extent of such qualities, of course, is dependent
upon the nature of the use, for example, temporary or permanent
implantation. While material selection and certain construction
techniques can be tailored to assist in meeting these prescribed
characteristics, an overriding consideration in the design of such
leads is achieving at least an isodiametric stimulation/pacing
portion thereof.
[0005] The benefits of achieving desired levels of flexibility,
strength, and durability are intuitive. The isodiametric
characteristic is likely less obvious. Depending upon the
application, an isodiametric lead can reduce the potential for
damage to the lead during insertion (for example, when a lead is
passed through an insertion needle to reach a patient epidural
space) and/or placement, improve the ability of the lead to pass
through tissue or a vascular system, and is more resistant to being
immobilized by tissue growth at a permanent implantation site.
[0006] Differing techniques have been used to produce isodiametric
leads. One such technique concerns adhering a plurality of elements
(i.e., conductive electrodes, conductive terminals, and spacing
insulative tubing material) to produce a generally integral body.
Tubing material separates a stimulation/sensing portion (i.e.,
alternating insulative tubing material and electrodes) from a
terminal portion (i.e., alternating insulative tubing material and
terminals). The electrodes, terminals, and tubing are independently
formed but are intended to be isodiametric. Understandably,
dimension variances in any one element can result in a lead having
a varying diameter.
[0007] Of further interest, to strengthen the plurality of element
interfaces found in the stimulation/sensing portions and terminal
portions of these leads, a composition, for example, medical grade
epoxy, is injected within an interior of the leads in and about the
stimulation/sensing portions and the terminal portions. While this
technique does typically effect stabilization and strengthening of
these critical regions, the end result can also be that these
regions are too rigid and even brittle.
[0008] Other techniques include applying a ring electrode(s) about
an exterior surface of insulative tubing that forms the main body
of the lead. The insulative tubing may be prepared to receive the
electrode, for example, milled to remove an amount of material
substantially equal to the material thickness of the ring
electrode. Alternatively, the insulative tubing may be unprepared,
for example, a ring electrode is simply "crimped" to a diameter
substantially equal to the otherwise unadulterated diameter of the
tubing.
[0009] For all of the methods described above, a finished lead is
still comprised of a plurality of independent components brought
together in an effort to form an isodiametric cross-section.
Element misalignment, inaccuracies in grinding, variances in
electrode material thickness or individual element dimensions, or
over/under-crimping could respectively result in at least
undesirable variances in lead diameter.
[0010] Accordingly, a need exists for a lead, as well as a method
of fabricating such lead, that provides a requisite level of
flexibility, strength, and durability, while further providing a
true isodiametric body for at least the stimulation/sensing portion
of the lead.
SUMMARY OF THE INVENTION
[0011] One aspect of the present invention is directed to an
implantable lead including a lead body, having a distal end and a
proximal end, whereas the lead body is formed of a material having
prescribed mechanical properties. Extending from the distal end of
the lead body, a first region includes a plurality of electrodes. A
first insulative material, having mechanical properties consistent
with the material of the lead body, separates adjacent electrodes.
Extending from the proximal end of the lead body, a second region
includes at least one terminal. A second insulative material,
having mechanical properties consistent with the material of the
lead body, separates adjacent terminals. A conductor couples each
terminal to at least one corresponding electrode of the plurality
of electrodes, wherein the conductor(s) extends along an interior
passage defined by the lead body, first region, and second region.
In addition to the at least one conductor, the interior passage of
the first region is substantially filled with a third insulative
material having mechanical properties consistent with the material
of the lead body:
[0012] Another aspect of the present invention concerns a method of
forming a substantially isodiametric lead. Specifically, such lead
has a prescribed diameter and includes at least one electrode
separated from at least one terminal by a lead body, wherein the at
least one electrode is electrically coupled to the at least one
terminal by a conductor passing through a passage defined by at
least the lead body. The forming steps include assembling the at
least one electrode and the at least one terminal relative to the
lead body to form an assembly, including connecting the at least
one electrode to the at least one terminal via the conductor. The
assembly is subjected to an over-molding process that over molds
the assembly with a first material to form an intermediate
assembly. This first material is compatible with and has mechanical
properties consistent with a material of the lead body. Ultimately,
the intermediate assembly is processed to remove all material of
the intermediate assembly in excess of the prescribed diameter.
[0013] An object of the present invention is to avoid the
shortcomings of known leads and manufacturing techniques for the
same.
[0014] Another object of the present invention is to provide a
method of forming a lead having a true isodiametric body for at
least the stimulation/sensing portion of the lead.
[0015] Another object of the present invention is to provide a lead
having a true isodiametric body for at least the
stimulation/sensing portion of the lead.
[0016] Another object of the present invention is to provide a lead
having a low resistance from a terminal to a coupled electrode to
reduce energy consumption during system operation.
[0017] Other aspects, objects, and advantages of the present
invention will be apparent to those of ordinary skill in the art
having reference to the following Specification together with the
provided drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In reference to the following figures, like reference
numerals and letters indicate corresponding elements:
[0019] FIG. 1 is a perspective view of a multi-electrode lead in
accordance with the present invention;
[0020] FIG. 2 is a plan view of another embodiment of a
multi-electrode lead in accordance with: the present invention;
[0021] FIG. 3 is a sectional view of the lead of FIG. 2, taken
along line III-III;
[0022] FIG. 4 is a perspective view of a preferred conductor;
[0023] FIG. 5 is a plan view of an assembly of elements on a
mandrel used to form a lead in accordance with the present
invention;
[0024] FIG. 6 is a sectional view of a transitional element;
[0025] FIG. 7 is a perspective view of an electrode spacer;
[0026] FIG. 8 is a perspective view of a terminal spacer;
[0027] FIG. 9 is a sectional view of a stylet guide;
[0028] FIG. 10 is a sectional view of a cap electrode; and
[0029] FIG. 11 is a schematic representation of one embodiment of
an assembly fixture used to assemble a lead in accordance with the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] Various embodiments, including preferred embodiments, will
now be described in detail below with reference to the
drawings:
[0031] FIG. 1 illustrates a preferred embodiment of multi-electrode
lead 10. While the leads illustrated and generally discussed here
have eight electrodes, lead 10 of the present invention may be
constructed having any number of electrodes (i.e., one or
more):
[0032] Lead 10 includes a proximal end 12 and a distal end 14. The
proximal end 12 includes a plurality of electrically conductive
terminals 16, and the distal end 14 includes a plurality of
electrically conductive electrodes 18. While typically each
terminal 16 is electrically connected to a single electrode 18 via
a conductor 20 (FIG. 3), a terminal 16 can be connected to two or
more electrodes 18.
[0033] Terminals 16 and electrodes 18 are preferably formed of a
non-corrosive, highly conductive material. Examples of such
material include stainless steel, MP35N, platinum, and platinum
alloys. In a preferred embodiment, terminals 16 and electrodes 18
are formed of a platinum-iridium alloy.
[0034] Spanning between electrodes 18 of the distal end 14 and
terminals 16 of the proximal end 12, body 22 is formed from a
medical grade, substantially inert material, for example,
polyurethane, silicone, or the like. While the specific material
used for body 22 is not critical to the present invention, body 22
must be non-reactive to the environment of the human body, provide
a flexible and durable (i.e., fatigue resistant) exterior structure
for the components of lead 10, and insulate adjacent terminals 16
and/or electrodes 18.
[0035] Serving as a sheath, body 22 substantially provides the
exterior structure that contains the internalized elements of lead
10. Specifically, body 22 provides an enclosure for each conductor
20 that connects a terminal 16 with one or more electrodes 18. Each
conductor 20 is formed of a conductive material that exhibits the
desired mechanical properties of low resistance, corrosion
resistance, flexibility, and strength. For consideration, however,
it should be appreciated that in the context of a multiple
electrode lead 10, a plurality of conductors 20 are required to fit
within the interior of body 22. Accordingly, the cross-sectional
area of each conductor 20 is restricted. As but one example, for a
lead in accordance with the present invention that has an outer
diameter of approximately 0.055 inches, conductor 20 could be on
the order of approximately 0.0065 inches.
[0036] While stranded bundles of stainless steel, MP35N, platinum,
platinum-iridium alloy, drawn-brazed silver (DBS) or the like can
be used, the preferred embodiment of conductors 20 utilizes wires
formed of multi-strands of drawn-filled tubes (DFT), as illustrated
in FIG. 4. Each strand is formed of a low resistance material 20a
and is encased in a high strength material 20b (preferably, metal).
A selected number of strands (seven, for this example) are wound
and coated with an insulative material 20c. With regard to the
operating environment of the present invention, insulative material
20c protects the individual conductors 20 if body 22 were breached
during use. Wire formed of multi-strands of drawn-filled tubes to
form conductors 20, as discussed here, is available from Temp-Flex
Cable, Inc. (City, State).
[0037] In addition to providing the requisite strength,
flexibility, and resistance to fatigue, conductors 20 formed of
multi-strands of drawn-filled tubes, in accordance with the
preferred embodiment, provide a low resistance alternative to other
conventional materials. Specifically, a stranded wire, or even
coiled wire, of approximately 60 cm and formed of MP35N or
stainless steel or the like would have a measured resistance in
excess of 30 ohms. In contrast, for the same length, a wire formed
of multi-strands of drawn-filled tubes, as illustrated in FIG. 4,
could have a resistance less than 4 ohms. Accordingly, in a
preferred embodiment, each conductor 20, having a length equal to
or less than 60 cm, has a resistance of less than 25 ohms. In a
more preferred embodiment, each conductor 20, having a length equal
to or less than 60 cm, has a resistance equal to or less than 10
ohms. In a most preferred embodiment, each conductor 20, having a
length equal to or less than 60 cm, has a resistance of less than 4
ohms.
[0038] As an alternative embodiment, body 22 can further encompass
stylet tubing 24 (FIG. 3). Stylet tubing 24 extends from the
proximal end 12 to a point within a distal portion of lead 10;
however, in a preferred embodiment, stylet tubing 24 extends to cap
electrode 34. In cooperative reference to FIG. 2, stylet tubing 24
operatively receives stylet 100 for purposes of allowing better
control over lead 10 during placement.
[0039] Lead Assembly
[0040] While the following discussion provides but one example of a
sequence of steps to form a lead similar to that illustrated in
FIGS. 2 and 3. One having ordinary skill in this art shall
appreciate that the following steps may be performed in a differing
order or otherwise inconsequentially modified to still yield the
present invention. Consequently, such minor variations are still
regarded as being within the scope of the present invention and
should be construed in such manner.
[0041] Furthermore, for purposes of illustration, the following
example includes certain physical dimensions to illustrate the
relationship between elements as well as effects of differing
processes. Accordingly, the provided physical dimensions are used
merely for example and shall not restrict the scope of the present
invention.
[0042] The following illustrative example concerns the construction
of an eight electrode, epidural lead that accommodates a stylet.
One skilled in the art shall appreciate, however, that a lead in
accordance with the present invention may have more than or less
than eight electrodes and/or have a larger or smaller diameter than
the following example and remain within the scope of this
disclosure.
[0043] In reference to FIG. 5, stylet tubing 24 is positioned over
mandrel 150. Stylet tubing 24 has an outer diameter of
approximately 0.02 inches:
[0044] Depending on the quantity of conductors 20 required (e.g.,
for this illustration, eight) and the size (i.e., diameter) of such
conductors 20, arranging and securing conductors 20 can be
problematic when they are being arranged and secured about an
element having the dimensions of stylet tubing 24.
[0045] While any number of techniques may be used to achieve such
arrangement of conductors 20 relative to stylet tubing 24, FIG. 11
illustrates an example of a fixture 200 that can assist in this
task. Specifically, fixture 200 includes first rotary clamp 202,
iris 204, iris 206, second rotary clamp 208, and clamp 210. Rotary
clamps 202 and 208 each include a corresponding plurality of
conductor clamps 203. While not required, it is preferred that the
plurality of conductor clamps 203 of each rotary claim 202 and 208
be positioned within an arbitrary perimeter 205, whereas perimeter
205 should be equal to or greater than a fully-opened inner
diameter of either iris 204 or 206:
[0046] As illustrated, mandrel 150, including stylet tubing 24,
passes through irises 204 and 206 and second rotary clamp 208 and
is secured between clamps 202 and 210. Each conductor 20 similarly
passes through irises 204 and 206 and is secured between respective
clamps 203 of rotary clamps 202 and 208.
[0047] Conductors 20 secured within fixture 200 are prepared for
assembly in that a prescribed amount of insulative material 20c is
removed at or about the proximal and distal ends of each conductor
20 to expose conductive material 20a and 20b. As will be discussed
later, this exposed conductive material 20a and 20b of the proximal
and distal ends of each conductor 20 is eventually joined to an
electrode 18 and a terminal 16. Accordingly, the exposed conductive
material 20a and 20b is arranged at differing positions relative to
stylet tubing 24 to accommodate the serial arrangement of terminals
16 and electrodes 18.
[0048] The rotational nature of rotary clamps 202 and 208 provides
unobstructed access to the in-process lead 10. Specifically, upon
securing a single conductor 20 between opposing (or non-opposing)
clamps 203, the rotary clamps 202 and 210 are simply rotated to
allow access to unoccupied clamps 203.
[0049] When all of the conductors 20 are strung between claims 202
and 208, irises 204 and 206 are actuated to close and draw
conductor(s) 20 closely about the outer diameter of stylet tubing
24. When conductor(s) 20 are resting against the outer diameter of
stylet tubing 24, conductor(s) 20 are secured in place.
Conductor(s) 20 may be secured using adhesive and/or subjected to a
force applied through use of a temporary or permanent restraint,
for example, one or more crimped collars.
[0050] While the illustration of FIG. 11 shows but one embodiment
of fixture 200, one skilled in the art should appreciate that other
techniques/structures may be employed to position conductors 20
adjacent an exterior surface of stylet tubing 24. Specifically,
clamps 203 of each rotary clamp 202 and 208 could be moveable along
respective radial paths (not shown) that would allow strung
conductors 20 to be moved from a first position to a second
position adjacent the exterior surface of stylet tubing 24.
Alternatively, conductors 20 could initially be secured to one end
of stylet tubing 24 and only a single iris could be used to draw
the unsecured portions of conductors 20 toward stylet tubing 24. As
yet another alternative, while the various alternatives offered
provide some mechanism to control the rate of movement and relative
positioning of conductors 20, an operator could simply manipulate
the conductor(s) 20 to manually position and secure them relative
to stylet tubing 24.
[0051] Once all conductors 20 are secured to stylet tubing 24,
transitional element 26, electrode(s) 18, electrode spacer(s) 28,
outer tubing 23, terminal spacer(s) 30, terminal(s) 16, and stylet
guide 32 are positioned over, and concentrically arranged with,
stylet tubing 24. The arrangement of these elements is in
accordance with that illustrated in FIG. 5.
[0052] Transitional element 26 is illustrated in FIG. 6. As will be
discussed later, transitional element 26 provides a platform to
receive cap electrode 34 (FIG. 10). Transitional element 26 further
provides a durable guide 26a to direct a distal end (not shown) of
stylet 100 to cap electrode 34 via passage 26b. Transitional
element 26 is preferably formed of a conductive material, for
example, the same material used to form electrodes 18.
[0053] Electrode spacer 28 is illustrated in FIG. 7. Similarly,
terminal spacer 30 is illustrated in FIG. 8. Functionally,
electrode spacer 28 and terminal spacer 30 accurately defines a
space between adjacent electrodes 18 and terminals 16,
respectively. Electrode spacer 28 and terminal spacer 30 are
preferably formed of the same material as outer tubing 23. However,
spacers 28 and 30 may be formed of a material that differs from
that of outer tubing 23; provided however, any differing material
used for electrode spacer 28 and/or terminal spacer 30 must be
compatible with and possess largely the same mechanical properties
(e.g., non-reactive to the environment of the human body, flexible
and durable) as outer tubing 23. At least for purposes of this
example, spacers 28, and 30 are formed of a polyurethane material,
for example, Bionate 75D (Polymer Tech. Group, City, State). As is
noted in FIG. 5, spacers 28 and 30 should have an outer diameter
greater than lead 10.
[0054] Outer tubing 23 separates electrodes 18 from terminals 16.
In a preferred embodiment, outer tubing 23 has a diameter
substantially equal to a diameter of lead 10. Alternatively, outer
tubing 23 may have a diameter less than lead 10, or a diameter
greater than lead 10. In regard to the latter alternative, outer
tubing 23 must have a wall thickness greater than a differential
between a radius of lead 10 and a radius (to the outer diameter) of
outer tubing 23. For this particular example, outer tubing 23 has a
nominal outer diameter of approximate 0.055 inches.
[0055] Stylet guide 32 is illustrated in FIG. 9. Stylet guide 32
provides an inlet to stylet tubing 24. Stylet guide 32 is
preferably formed of conductive material, for example, the same
material used to form electrodes 18. Stylet guide 32, as well as
terminals 16, electrodes 18, and transitional element 26,
preferably each have an outer diameter equal to or greater than a
nominal diameter of lead 10. In a more preferred embodiment, these
elements each have an outer diameter greater than a nominal
diameter of lead 10.
[0056] Following the assembly of each of the elements described
above, terminals 16 and electrodes 18 are joined to their
respective conductors 20. Generally, each terminal 16 (and each
electrode 18) is positioned relative to exposed conductive material
20a and 20b of a conductor 20 and is joined in a manner that
facilitates a transfer of electrical energy, for example,
resistance weld or laser weld. Once all terminals 16 and electrodes
18 are secured, stylet guide 32 is secured to a proximal-most
terminal 16, and transitional element 26 is secured to a
distal-most electrode 18. Provided transitional element 26 and
stylet guide 32 are formed a conductive material, these elements
may be secured using a process consistent with that used to join
terminals 16 arid electrodes 18 with conductors 20. Otherwise,
transitional element 26 and stylet guide 32 can be joined using an
adhesive, cement or the like.
[0057] The completed assembly (FIG. 5) is then over-molded, using
well known injection molding techniques, using a material having
mechanical properties consistent with a material(s) used to form
outer tubing 23, electrode spacer 28, and terminal spacer 30. In a
preferred embodiment, the over-molding material and the material of
outer tubing 23, electrode spacer 28, and terminal 28 are the
same.
[0058] This process has the beneficial effect of unitizing the
element assembly to form lead 10. Moreover, electrode spacers 28
and terminal spacers 30 are placed in a state of flow, which, at
least in part, results in a filling of regions between terminals
16/electrodes 18 and stylet guide 24. Consequently, terminals 16
and electrodes 18 are partially surrounded (i.e., along an interior
surface) and supported by a fused matrix of; material. Importantly,
as electrode spacers 28 and terminal spacers 30 are formed of a
material mechanically equivalent to that of body 22/outer tubing
23, the stimulation/sensing portion and terminal portion of lead 10
are stabilized and strengthened while also retaining their flexible
properties.
[0059] The over-molded assembly (not shown) is then subjected to a
grinding process to remove all excess material. In a preferred
process, the over-molded assembly is subject to centerless
grinding, wherein excessive material, including over-molded
material, electrode material, terminal material, and the like, is
removed. Pursuant to the described over-molding and grinding of the
entire lead assembly, an isodiametric lead is obtained, which is
further free of any gaps or voids between insulative material and
conductive material that may otherwise exist in conventional
devices.
[0060] Following the grinding process, cap electrode 34 is affixed
to transitional element 26 using conventional means, for example,
resistance welding, laser welding, or the like.
[0061] While addressed in part above, as the invention has been
described herein relative to a number of particularized
embodiments, it is understood that modifications of, and
alternatives to, these embodiments, such modifications and
alternatives realizing the advantages and benefits of this
invention, will be apparent to those of ordinary skill in the art
having reference to this specification and its drawings. It is
contemplated that such modifications and alternatives are within
the scope of this invention as subsequently claimed herein, and it
is intended that the scope of this invention claimed herein be
limited only by the broadest interpretation of the appended claims
to which the inventors are legally entitled.
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