USOO8646172B2
`
`(12) Un1ted States Patent
`(10) Patent No.:
`US 8,646,172 B2
`
`Kuzma et al.
`(45) Date of Patent:
`Feb. 11, 2014
`
`(54) ELECTRODE ARRAY ASSEMBLY AND
`METHOD OF MAKING SAME
`
`(75)
`
`Inventors: Janusz A. I.(uzma, Parker, CO (US);
`Anne M. Planca, Valenc1a, CA (US)
`
`(73) Assignee: Boston Scientific Neuromodulation
`Corporation, Valencia, CA (US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U-S-C~ 15403) by 315 days.
`
`(21) APPI- N05 133/013-1599
`
`(22)
`
`Filed:
`
`Jan. 25, 2011
`
`................... 607/122
`4/2001 Black et a1.
`6,216,045 B1 *
`
`607/122
`6/2001 Nelson et al.
`6,249,708 B1 *
`.. 604/505
`.
`4/2003 Rosinko et al.
`6,551,302 B1*
`7/2003 Giba et al. ........... 29/447
`6,598,280 B1*
`6/2005 Stypulkowski
`.
`607/117
`6,909,918 B2 *
`
`5/2006 Kuzma ............
`607/115
`7,047,081 132 *
`2/2007 Stolz et al.
`..
`607/122
`7,184,840 B2 *
`
`2/2004 Cole ...............
`607/ 122
`2004/0024440 A1 *
`..................... 600/3
`2004/0225175 A1* 11/2004 Moody et al.
`(Continued)
`
`
`
`OTHER PUBLICATIONS
`U.S.Appl. No. 11/329,907, Official Communication mailed Nov. 17,
`2008.
`
`U.S. Appl. No. 11/329,907, Official Communication mailed Apr. 2,
`2009.
`
`US. Appl. No. 11/329,907, Official Communication mailed Jul. 1,
`2009.
`
`(65)
`
`Prior Publication Data
`
`US. Appl. No. 11/329,907, Official Communication mailed Mar. 31,
`2010.
`
`US 2011/0118815 A1
`
`May 19, 2011
`
`US. Appl. No. 11/329,907, Notice of Allowance mailed Nov. 15,
`2010.
`
`Related U.S. Appllcatlon Data
`(63) Continuation of application No. 11/329,907, filed on
`Jan. 11, 2006, now Pat. No. 7,891,085.
`
`Primary Examiner 7 David Angwin
`(74) Attorney, Agent, or Firm 7 Frommer Lawrence &
`Haug LLP; Bruce E. Black
`
`(60)
`
`(51)
`
`ll’ioggsosnal applicatlon No. 60/643,093, filed on Jan.
`,
`Int. Cl.
`HOIR 43/00
`A61N1/00
`(52) US. Cl,
`USPC ............................................. 29/825; 607/1 16
`(58) Field of Classification Search
`USPC ..................................... 29/825; 607/1157122
`See application file for complete search history.
`
`(2006.01)
`(2006.01)
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`/
`*
`/
`h
`£73323? 2 * 153;: :23; e151 """""""""" 6g;011%?
`
`... 29/825
`5:555:618 A *
`9/1996 Winkler ........
`
`. 607/117
`6,055,456 A *
`4/2000 Gerber ..........
`
`..... 607/116
`6,205,361 B1 *
`3/2001 Kuzma et al.
`.
`
`ABSTRACT
`(57)
`A method of manufacturing a stimulation lead includes pro-
`viding a lead body having an insulation section that defines a
`central lumen extending along the insulation section and con-
`ductor lumens extending along the insulation section and
`arranged around, and external to, the central lumen. The lead
`body also includes conductive contacts located along an axial
`end ofthe leadbody and conductor wires with each conductor
`wire diSPosed within one ofthe conductor lumens and each of
`the conductor lumens having at least one of the conductor
`wires disposed therein. After providing the lead body, con-
`ductively at least one of the conductor wires to each of the
`conductive contacts; and placing non-conductive material
`into a portion of at least one of the conductor lumens of the
`lead body. A portion of the conductor lumens and at least a
`portion of the non-conductive material are disposed radially
`beneath the COHductiVe 0011mm
`
`11 Claims, 6 Drawing Sheets
`
`77
`
`722
`
`mflfg
`
`.790?
`
`Nevro Corp.
`Ex. 1001
`
`US. Patent No. 8,646,172
`
`Nevro Corp.
`Ex. 1001
`U.S. Patent No. 8,646,172
`
`

`

`US 8,646,172 B2
`Page 2
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`2005/0215945 A1*
`2006/0036218 A1*
`2007/0021771 A1*
`
`.................... 604/66
`9/2005 Harris et al.
`2/2006 Goodson et al.
`604/264
`
`1/2007 Oepen et al.
`.................. 606/194
`
`2007/0021821 A1*
`2007/0249997 A1*
`2008/0097426 A1*
`2009/0018487 A1*
`
`1/2007
`10/2007
`4/2008
`1/2009
`
`Johnson et al.
`.............. 623/1.11
`Goodson et al.
`.
`604/93.01
`
`Root et al.
`...................... 606/41
`Doty ............................... 604/21
`
`* cited by examiner
`
`

`

`US. Patent
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`Feb. 11,2014
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`Sheet 1 0f6
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`US 8,646,172 B2
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`US 8,646,172 B2
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`US 8,646,172 B2
`
`1
`ELECTRODE ARRAY ASSEMBLY AND
`METHOD OF MAKING SAME
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This utility patent application is a continuation of allowed
`US. patent application Ser. No. 11/329,907 filed Jan. 11,
`2006, which claims the benefit of US. Provisional Patent
`Application Ser. No. 60/643,093, filed Jan. 11, 2005, all of
`which are herein incorporated by reference in their entirety.
`
`FIELD OF THE INVENTION
`
`The present invention relates to implantable leads for pro-
`viding electrical stimulation and, more particularly, relates to
`leads having multiple electrode contacts and methods ofmak-
`ing such leads.
`
`BACKGROUND
`
`Many types of implantable leads are currently used to treat
`a variety of maladies. Two common treatment applications
`use leads having multiple electrode contacts. Cochlear stimu-
`lator systems use a multiple electrode contact lead inserted
`into one of the cochlear chambers to stimulate the cochlear
`
`nerve. Another application where a multiple electrode contact
`lead is used is the treatment of chronic pain through stimula-
`tion of the spinal cord.
`Spinal cord stimulation systems generally have two
`implantable components: an implantable pulse generator
`(IPG) and at least one lead connected to one output ofthe IPG.
`Generally, however,
`the IPG is a multi-channel device
`capable of delivering electrical current through the electrode
`contacts of the lead. The term “lead” used herein will refer to
`
`an elongate device having any conductor or conductors, cov-
`ered with an insulated sheath and having at least one electrode
`contact attached to the elongate device, usually at the distal
`portion of the elongate device. The lead can have an inner
`stylet lumen running through most of the length of the lead
`and which lumen has an opening at the proximal end of the
`lead. A stylet may be placed into this stylet lumen during
`steering and implantation ofthe lead. The inserted stylet in the
`lumen can help stiffen the lead so that the stylet/lead combi-
`nation may be more easily inserted through tissue.
`There are two types of leads that may be used with the IPG.
`The first type is a paddle lead, which has a multiplicity of
`electrode contacts spread out over a flat, paddle-like surface
`that is attached to one end of the lead. A paddle lead advan-
`tageously permits the electrode contacts to be spaced apart to
`provide wide coverage over a stimulation area. A disadvan-
`tage presented with a paddle lead is that it usually requires a
`laminectomy or laminotomy, which are highly invasive sur-
`gical procedures necessary to implant the large, non-isodia-
`metric paddle.
`A second type of lead that is commonly used is a percuta-
`neous lead, which has multiple electrode contacts positioned
`along the distal portion of an elongate lead. US. Pat. No.
`6,205,361 issued to Baudino et al. describes the making of a
`multi-contact electrode array for a lead. The distal end of the
`lead may be about the same thickness or diameter as the
`remainder of the lead. The percutaneous lead is dimension-
`ally configured for tunneling to a target stimulation site. No
`invasive surgical procedure such as a laminotomy is required;
`the percutaneous lead may be placed through an epidural type
`needle reducing surgical trauma.
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`The method of making a multi-contact percutaneous lead
`can be involved. In general, it is desirable to make the lead
`efficiently, with the fewest number of process steps, maxi-
`mize the manufacturing yield, and hence reduce the cost of
`goods of building the leads. There is thus a continual need to
`improve the design ofa percutaneous lead in order to improve
`its performance and to improve the method of manufacturing
`the lead.
`
`BRIEF SUMMARY
`
`A method ofmaking a lead is provided. In one embodiment
`of the invention the method comprises: providing a plurality
`of conductive contacts located at the distal end of the stimu-
`
`lation lead; connecting a conductor wire to each of the con-
`ductive contacts; placing spacers between pairs of adjacent
`conductive contacts; placing monofilament within void
`spaces not occupied by a conductor wire, wherein the
`monofilament is the same material as the spacers; placing a
`heat shrink tubing around the spacers, conductive contacts
`and monofilament; and heating the spacers and monofilament
`just below the melting temperature to cause thermal fusion
`between the monofilament and spacer.
`The conductive contacts may be connector contacts located
`at the proximal portion of the lead, which contacts are used to
`connect to the IPG, or the conductive contacts may be elec-
`trode contacts located somewhere on the lead (e.g., usually at
`the distal end of the lead).
`In another embodiment of the method of making the lead,
`the method comprises: providing a plurality of conductive
`contacts located at the proximal end of the stimulation lead;
`connecting a conductor wire to each of the conductive con-
`tacts; placing spacers between pairs of adjacent conductive
`contacts; placing monofilament within void spaces not occu-
`pied by a conductor wire, wherein the monofilament is a
`different material than the spacers; placing a heat shrink
`tubing around the
`spacers,
`conductive contacts,
`and
`monofilament; and heating the spacers and monofilament to a
`temperature to cause thermal flow or melting of at least one of
`the spacers or monofilament.
`Hence, while the monofilament and spacers may be the
`same material with the same melting temperatures, that is an
`optional part of the invention. The monofilament and spacers
`may actually be different materials, e.g., a type of thermo-
`plastic polyurethane monofilament and another type thermo-
`plastic polyurethane spacer, with different hardness and melt-
`ing points in order to yield a particular stiffness.
`In an embodiment of the invention, a lead assembly is
`provided comprising: a plurality of electrically conductive
`contacts; spacers placed between each adjacent contacts; a
`conductor wire connected to each conductive contact; and
`monofilament placed into void spaces not occupied by con-
`ductor wire, wherein the monofilament is made from the same
`insulative material as the spacer; and wherein the spacer and
`monofilament are thermally fused from heat applied to the
`lead assembly, which heat is just below the melting tempera-
`ture of the spacer and the monofilament material.
`In yet another embodiment, a lead assembly is provided
`comprising: a plurality of electrically conductive contacts;
`spacers placed between each adjacent contacts; a conductor
`wire connected to each conductive contact; and monofilament
`placed into void spaces not occupied by conductor wire,
`wherein the monofilament is made from a different insulative
`
`material as the spacer; and wherein the spacer and monofila-
`ment are heated to a temperature to cause either the spacer or
`monofilament material to thermally reflow or melt.
`
`

`

`US 8,646,172 B2
`
`3
`The monofilament and spacer may be the same thermo-
`plastic material to have the same melting point and to thereby
`allow thermal fusion upon heating at a temperaturejust below
`the melting temperature of the material or the monofilament
`and spacer may have different melting points.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The above and other aspects ofthe present invention will be
`more apparent from the following more particular description
`thereof, presented in conjunction with the following drawings
`wherein:
`
`FIG. 1 shows a generalized spinal cord stimulation system
`with a percutaneous lead connected to an implantable pulse
`generator (“IPG”);
`FIG. 2 shows an illustration of the percutaneous lead
`implanted into the epidural space of a human spinal cord;
`FIG. 3A shows a side view of the distal end of a percuta-
`neous lead.
`
`FIG. 3B shows a side view of the proximal (connector) end
`of the percutaneous lead shown in FIG. 3A;
`FIG. 4 shows a view ofthe proximal end of the lead assem-
`bly showing the connector contacts and conductor wires that
`connect to each connector contact;
`FIG. 5A shows a cross-sectional view of the percutaneous
`lead shown in FIG. 3A at line 5A-5A;
`FIG. 5B shows a cross-sectional view of the percutaneous
`lead shown in FIG. 5A along line 5B-5B;
`FIG. 5C shows a perspective view of the lead body, having
`a central stylet lumen and surrounding smaller lumens for
`containing conductor wires;
`FIG. 6A shows a close-up, partial, longitudinal view of the
`lead assembly at the distal portion of the lead; and
`FIG. 6B depicts how polyurethane monofilament or a ther-
`moplastic material is used to fill the voids and is incorporated
`into the lead by applying heat.
`Corresponding reference characters indicate correspond-
`ing components throughout the several views ofthe drawings.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`The following description is of the best mode presently
`contemplated for carrying out the invention. This description
`is not to be taken in a limiting sense, but is made merely for the
`purpose of describing the general principles of the invention.
`The scope of the invention should be determined with refer-
`ence to the claims.
`
`FIG. 1 shows a generalized stimulation system that may be
`used in spinal cord stimulation (SCS), as well as other stimu-
`lation applications. Such a system typically comprises an
`implantable pulse generator (“IPG”) 12, an optional lead
`extension 14, a lead 16 and an electrode array 18. The elec-
`trode array 18 includes a plurality of electrode contacts 17. In
`a percutaneous lead, the electrode contacts 17 canbe arranged
`in an in-line electrode array 18 at the distal end of the lead 16.
`Other electrode array configurations can also be used. The
`IPG 12 generates stimulation current pulses that are applied
`to selected electrode contacts 17 within the electrode array
`18.
`
`The proximal end of the lead extension 14 can be remov-
`ably connected to the IPG 12 and a distal end of the lead
`extension 14 can be removably connected to a proximal end
`ofthe lead 16. The electrode array 18 is formed on a distal end
`ofthe lead 16. The in-series combination ofthe lead extension
`14 and lead 16 conduct the stimulation current from the IPG
`
`12 to electrode contacts 17 of the electrode array 18. It is
`noted that the lead extension 14 need not always be used with
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`the neural stimulation system 10. Instead, the lead extension
`14 may be used when the physical distance between the IPG
`12 and the electrode array 18 requires its use, or for the
`purpose of a temporary trial procedure.
`The IPG 12 contains electrical circuitry, powered by an
`internal primary (one-time-use-only) or a rechargeable bat-
`tery, which through the use of electrical circuitry can output
`current pulses to each stimulation channel. Communication
`with the IPG can be accomplished using an external program-
`mer (not shown), typically through a radio-frequency (RF)
`link.
`
`FIG. 2 shows a transverse, mid-sagittal view of a spinal
`cord and a generalized, implantable, spinal cord stimulation
`system. The stimulation system shown is being used as a
`spinal cord stimulator (SCS) system. In such an application,
`the lead 16 and, more particularly, the electrode array 18 are
`implanted in the epidural space 20 of a patient in close prox-
`imity to the spinal. cord 19. Because ofthe lack of space near
`the lead exit point 15 where the electrode lead 16 exits the
`spinal column, the IPG 12 may be implanted in the abdomen
`or above the buttocks. Use of lead extension 14 facilitates
`
`locating the IPG 12 away from the lead exit point 15.
`FIG. 3A shows, in accordance with the invention, a distal
`portion of a percutaneous stimulating lead 16. The stimulat-
`ing lead 16 is used to stimulate neural tissue by delivering
`electrical stimulus pulses through at least one of the electrode
`contacts 17. The electrode contacts 17 can be separated by
`electrode contact spacers (or an insulative material) 61 that
`insulate the electrode contacts 17 from each other. A radio-
`
`paque marker 30 located at the distal tip ofthe lead 16 may be
`optionally included. Alternatively, the tip of the lead may be
`the same material as the remainder ofthe lead insulation. The
`
`IPG 12 may be configured to permit connection to the two
`stimulating leads, each having eight electrode contacts 17. A
`pair of stimulating leads 16 may be connected to an IPG 12
`and an electrical circuit may be created between one electrode
`contact on the first lead and another electrode contact located
`
`on the second lead. The IPG 12, for example, may have
`sixteen independently programmable outputs that allow pro-
`gramming of pulse amplitude, pulse width and frequency of
`the pulse width. The electrode contacts 17 are to be made of
`a bio-compatible, electrically conductive electrode material
`such as platinum/iridium alloy, platinum, titanium or the like.
`As an example, the stimulating lead 16 may have a diam-
`eter of between about 0.03 to 0.07 inches for spinal cord
`stimulation applications. An insertion cannula (not shown),
`e.g., a 14 gauge insertion needle may be used, while a 0.05
`inch diameter stimulating lead is inserted within the cannula
`to help implant the stimulating lead 16. The stimulating lead
`16 may come in a variety of lengths, e.g., 30, 50, 70 and 90
`cm. A practitioner can extend the length of any of the avail-
`able lead lengths by opting to use an extension lead 14 (shown
`in FIG. 1). The proximal male end of the extension lead 14
`should be configured to be insertable into the lead connector
`of the IPG and the distal female end of the extension lead
`
`should be configured to accept the proximal connector end of
`the stimulating lead 16.
`FIG. 3B shows, in accordance with the invention, a depic-
`tion of the proximal end of the lead 16. This proximal lead
`end, including the eight, electrically conductive, connector
`contacts 40, and a contact tip element 41, collectively will be
`called herein as the proximal lead connector end 42 of the
`stimulating lead 16. Connector contact spacers 45 are placed
`between the connector contacts 40. The spacers 45 may be
`made from an implantable grade polyurethane such as Pelle-
`thane® 55D thermoplastic material. The contacts 40 may be
`made from a non-corrosive, electrically conductive material,
`
`

`

`US 8,646,172 B2
`
`5
`e.g., platinum/iridium alloy or platinum. Contact tip 41, how-
`ever, is not electrically connected to any conductor and con-
`tact tip 41 may merely serve as a hard surface for a mechanical
`contact securing device, such as a set screw, which may be
`used to secure the lead connector end 42 with the connector
`
`block of the IPG 12. Contact tip 41 is optional and does not
`need to be included as part ofthe lead. Instead, the contact tip
`of the lead may be of similar or the same insulation material
`as the remainder of the lead 16 or lead body 110 (FIG. 5C).
`Preferably the lead 16 is substantially isodiametric, mean-
`ing that the diameter along the lead’ s entire length is equal or
`nearly equal. However, the lead 16 does not need to be iso-
`diametric. For example, the connector contacts 40 at the
`proximal end may be larger (oversized) or smaller in diameter
`compared to the remainder of the lead 16 or lead body 110
`(shown in FIG. 5C). Likewise, the electrode contacts 17 may
`be larger (oversized) or smaller in diameter compared to the
`remainder ofthe lead 16 or lead body 110 (shown in FIG. 5C).
`FIG. 4 shows a proximal lead assembly with each of the
`connector contacts 40 welded to a respective one of conduc-
`tors 122. Each of the eight connector contacts 40, as shown,
`are connected to a conductor 122 which, in turn, are con-
`nected to a respective electrode contact 17 at the distal end of
`the stimulating lead 16. The insulating material between the
`connector contacts 40 and around the conductors 122 is not
`
`shown in FIG. 4 for purposes of better illustrating the con-
`nection between each conductor and its respective connector
`contact. The connection may be a weld. Cylindrical element
`46 is optional and is not connected to any conductor. Cylin-
`drical element 46 may be used as a contact element for a
`mechanical securing device such as a set screw in order to
`secure the lead 16 to the IPG 12. Alternatively, or in addition,
`the cylindrical element 46 may function as a radiopaque
`element, provided that the material used for element 46 is
`radiopaque.
`FIG. 5A shows a cross-sectional view of the lead of FIG.
`
`3A along line 5A-5A.
`FIG. 5B shows a partial, cross-sectional view of the lead
`along the line 5B-5B.
`FIG. 5C shows a perspective view of an exemplary lead
`body 110 of the lead 16, excluding conductor wires. The lead
`body is that portion of the lead insulation 112 that is between
`the distal electrode contact array 18 and the array of connec-
`tors contacts 40 (FIG. 4) at the proximal lead connector end
`42. The lead body 110 may be extruded as a one-piece com-
`ponent. Note the central stylet lumen 114 and the surrounding
`eight conductor lumens 116.
`FIGS. 5A and 5B show an exemplary embodiment of an
`insulation section 112 of the lead body 110 having eight
`lumens 116 containing the conductor (wires) 122, having
`individual strands 120. For example 15 or 16 individual con-
`ductor strands 120 may be braided or bundled into a single
`conductor 122. Also shown is a central lumen 114 that may be
`used to accept an insertion stylet (not shown) within the
`lumen to facilitate lead implantation. The opening of the
`lumen occurs at the proximal end of the lead 16. The lead
`body 110 may be a biocompatible, insulating lead material.
`Preferably the lead body 110 is made from a polyurethane. In
`particular the material may be Pellethane® thermoplastic
`material, e.g. 55D, 65D, or other durometer hardness. As
`previously indicated for FIG. 5C, the lead body 110 shown in
`FIG. 5B may be extruded as one piece.
`FIG. 6A shows a partial view of a longitudinal, cross-
`section at the distal end of the lead, in accordance with an
`embodiment of the invention. FIG. 6A shows a ring-like
`electrode contact 17 (which may be platinum, for example),
`multi-stranded conductor 122 and electrode contact spacer 61
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`(or an insulative material). The spacer 61, which is ring-like in
`configuration, may be made of polyurethane insulative mate-
`rial, e. g., Pellethane®. Monofilament 60, also may be made of
`thermoplastic Pellethane® material or other insulation mate-
`rial, e. g., polyester. During manufacture, the monofilament
`60 may be inserted into the void spaces that are not filled by
`the conductor 50. A heat shrink tube 65 is also shown placed
`around the electrode contacts 17 and conductor 122 assembly.
`The heat shrink tube 65 may be PTFE (e. g., Teflon® material)
`or a polyester heat shrink material. The heat shrink tube can
`be used during manufacturing and is not part of the stimula-
`tion lead.
`
`FIG. 6B shows a two-frame, time-elapsed illustration of a
`partial view ofthe distal end ofthe lead as in FIG. 6A showing
`the conductor 122 connected (e.g., welded) to the electrode
`contact 17. The first frame (i) of FIG. 6B shows the sequence
`in which the monofilament 60 fills a large part of the void
`space 70. The part of the lead assembly shown is then placed
`into a heat, for example, at 190 degrees Celsius for a period of
`30 seconds. The heat that may be used, e.g., for polyurethane
`material (such as Pellethane®), may range from about 140 to
`250 degrees Celsius for a period of about between 15 to 120
`seconds. However, importantly, the heat applied to the spacer
`and monofilament material, should be just below the melting
`temperature of the material. At this just-below-melting tem-
`perature, the spacer and monofilament will reflow and ther-
`mally fuse together as shown in the second frame (ii). The
`spacer 61 and the monofilament 60 may be exactly the same
`material with the same melting temperature in order to facili-
`tate thermal fusion. For example, the material may be the
`same implantable grade polyurethane such as Pellethane 55 D
`or 75 D.
`
`Alternatively, however, the monofilament may be of a dif-
`ferent material than the spacer to alter the mechanical char-
`acteristic of the final lead assembly. The monofilament and
`spacer may have different melting points or very close melt-
`ing points. The monofilament and spacers may be the same
`type of material but with different formulations, e.g., to pro-
`vide different hardness. For example, the monofilament may
`be a 55 D (durometer hardness) material and the spacer may
`be a 75 D material. The predetermined temperature chosen to
`heat both the monofilament and spacers should cause at least
`one of the materials used to thermally reflow or, alternatively
`to melt. In some cases, the temperature may be chosen that
`one material melts while the other material thermally reflows.
`While FIGS. 6A and 6B show the distal end ofthe lead, the
`same process of using a monofilament to fill up void spaces
`may be used at the proximal end of the lead assembly. At the
`proximal end of the lead assembly, the conductive contacts
`are not electrode contacts but, are instead, electrically con-
`ductive connector contacts 40 that must be in electrical con-
`
`nection with complementary contacts in the IPG connector.
`The connector contact spacers 45 at the proximal end of the
`lead (shown in FIG. 3B) are placed between adjacent connec-
`tor contacts 40. In one embodiment of the invention, the
`connector contact spacers 45 may be oversizedithat is, the
`spacers may have an initial diameter that is larger than the
`final lead diameter. The proximal connector end of the lead
`assembly 42 may then be heated to a temperature (just below
`melting point of the spacer and monofilament) for a duration
`of time previously described in order to produce thermal
`fusion of the connector contact spacer 45 and monofilament
`60 to create a continuous reflow of material between the
`
`spaces not occupied by the connector contacts 40 and con-
`ductor wires 122.
`
`

`

`US 8,646,172 B2
`
`7
`Alternatively, the monofilament 60 and spacer 45 may be
`different materials with different melting points or about the
`same melting points.
`Hence, the method of placing monofilament into void
`spaces not occupied by the conductor 122, may be used solely
`at the distal end of a lead, solely at the proximal end of a lead,
`or may be employed concurrently at both ends of a lead. If
`only one end of a lead employs monofilament, the other end
`of the lead may employ another method to finish the build,
`e.g., overrnolding using a mold or injecting material such as
`epoxy, e.g., Hysol® into the void spaces between the contacts
`and conductor wires.
`
`EXAMPLE
`
`The following steps illustrate one example embodiment of
`a method for making the lead, in accordance with the inven-
`tion. Embodiments of the method can include one or more of
`
`the following steps (although not necessarily in the order
`presented). (1) A braided or bundled, insulated, multi-fila-
`ment conductor, e.g., having 2-200 filaments, can be ablated
`of insulation at one end to expose the conductor. (2) The
`exposed end of the conductor can be welded to an electrode
`contact (located on the distal end lead assembly). (3) Over-
`sized, distal lead spacers may be placed between the electrode
`contacts. (4) The multi-lumen tube (lead body) may be pre-
`cut with ablated section located at the distal and proximal
`ends. (5) Each end of the conductor cable can be inserted
`through the corresponding conductor lumens in the lead body.
`(6) The oversized spacers can be placed between each ring-
`like electrode contact at the distal end of the lead assembly;
`the spacers 61 may be “oversized”, meaning that they may
`have a diameter greater than the lead body 110 and in addi-
`tion, the diameter of the electrode contacts 17 may be over-
`sized compared to the diameter of the lead body 110. (7) The
`distal end of each conductor cable can be welded to the
`
`ring-shaped electrode contact. (8) Polyurethane monofila-
`ment may be placed inside the void space as shown in FIG.
`6A, and inside any empty conductor lumens 116. (9) A heat
`shrink tube or wrap, preferably, made from PTFE (Teflon) or
`polyester, can be placed over the distal end of the lead assem-
`bly and over the electrode array; this distal end can be placed
`into a high temperature block, e.g., between about 140-250
`degrees Celsius for a period of about 30 to 120 seconds. (10)
`The distal assembly can be removed from the heat and the
`shrink tube or wrap can be removed. (10) Optionally, the
`distal tip of the lead can be formed using an RF welder.
`Post processing of the lead is not always required. For
`example, grinding of the distal or proximal ends of the leads
`is not necessary with this method of manufacturing, although
`optionally, a centerless grinding process may be used, if
`desired.
`
`The method of making the distal and proximal part of the
`lead, in accordance with the present invention, eliminates
`most, if not all tooling, including eliminating the use of
`molds.
`
`The method of making a lead and the resulting multi-
`contact lead,
`in accordance with the invention, provides
`advantages over conventional leads and methods of making a
`lead. A prior method of making the distal portion of the lead
`uses epoxy to fill the voids between the spacer 61 and the
`contacts 17. This has certain disadvantages. For instance, use
`of an epoxy requires a curing step, e.g., of up to eight hours,
`adding to the total time required to build a lead. With use of
`epoxy, there may also be some variation in stiffness of the
`final lead assembly post-cure because the epoxy is generally
`a different material than the insulative body or spacers and
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`because curing may occur unevenly. The use oflike materials,
`e.g., polyurethane lead body, polyurethane spacers and poly-
`urethane monofilament can yield a better bond between these
`parts.
`Although the lead and method of making the lead are
`described in the context of a spinal cord stimulation lead, it
`will be understood by those skilled in the art that the same
`lead, albeit with appropriate dimensions for a particular appli-
`cation, and the method of making the lead may be used to
`make a multi-contact lead suitable for use in other applica-
`tions, such as deep brain stimulation, cardiac stimulation and
`peripheral nerve stimulation.
`While the invention herein disclosed has been described by
`means of specific embodiments and applications thereof,
`numerous modifications and variations could be made thereto
`
`by those skilled in the art without departing from the scope of
`the invention set forth in the claims.
`
`What is claimed and desired to be protected by Letters
`Patent of the United States is:
`
`1. A method of manufacturing a stimulation lead compris-
`ing:
`providing a lead body comprising an insulation section, the
`insulation section defining a central lumen extending
`along the insulation section and a plurality of conductor
`lumens extending along the insulation section and
`arranged around, and external to, the central lumen, the
`lead body further comprising a plurality of conductive
`contacts located along an axial end of the lead body, and
`a plurality of conductor wires, wherein each of the con-
`ductor wires is disposed within one of the plurality of
`conductor lumens and each of the conductor lumens of
`
`the plurality of conductor lumens has at least one of the
`conductor wires of the plurality of conductor wires dis-
`posed therein, wherein a portion of the conductor
`lumens is disposed radially beneath the conductive con-
`tacts;
`after providing the lead body, conductively coupling at
`least one of the plurality of conductor wires to each of
`the conductive contacts; and
`after providing the lead body, placing non-conductive
`material into a portion of at least one of the conductor
`lumens ofthe lead body, wherein at least a portion ofthe
`non-conductive material is disposed radially beneath the
`conductive contacts.
`
`2. The method of claim 1, further comprising heating the
`non-conductive material to cause the non-conductive mate-
`
`rial to thermally reflow or melt.
`3. The method of claim 1, wherein placing non-conductive
`material comprises placing the non-conductive material into
`a portion of each of the conductor lumens of the lead