SELF-FOLDING PADDLE LEAD AND METHOD OF FABRICATING A PADDLE LEAD
In one embodiment, a medical lead comprises a lead body for conducting electrical pulses and a paddle. The paddle includes an intermediate metal layer, at least an insulative polymer backing layer, and an insulative polymer covering layer. The intermediate metal layer comprises a plurality of features defined by gaps in the metal material in the metal layer such that each feature is electrically isolated from each other feature, wherein each feature includes a respective connector element that is electrically coupled to at least one conductor within the lead body, wherein a portion of the insulative polymer covering layer is exposed above each feature to define a respective electrode for the corresponding feature. Also, the paddle possesses shape memory to cause the paddle to assume a substantially planar orientation when the shape memory is in a relaxed state.
The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/772,321, filed Feb. 10, 2006, entitled “SELF-FOLDING PADDLE LEAD AND METHOD OF FABRICATING A PADDLE LEAD,” which is incorporated herein by reference.
TECHNICAL FIELDThe present application is generally related to a paddle lead that is self-folding for insertion in a patient using an insertion tool or catheter and that returns to an extended state upon exiting the insertion tool or catheter within the epidural space.
BACKGROUNDApplication of electrical fields to spinal nerve roots, spinal cord, and other nerve bundles for the purpose of chronic pain control has been actively practiced for some time. While a precise understanding of the interaction between the applied electrical energy and the nervous tissue is not fully appreciated, it is known that application of an electrical field to spinal nervous tissue (i.e., spinal nerve roots and spinal cord bundles) can effectively mask certain types of pain transmitted from regions of the body associated with the stimulated nerve tissue. Specifically, applying electrical energy to the spinal cord associated with regions of the body afflicted with chronic pain can induce “paresthesia” (a subjective sensation of numbness or tingling) in the afflicted bodily regions. Thereby, paresthesia can effectively mask the transmission of non-acute pain sensations to the brain.
It is known that each exterior region, or each dermatome, of the human body is associated with a particular longitudinal spinal position. Thus, electrical stimulation of nerve tissue must occur at a specific longitudinal location to effectively treat chronic pain. Additionally, it is important to avoid applying electrical stimulation of nerve tissue associated with regions of the body that are unaffected by chronic pain. Positioning of an applied electrical field relative to a physiological midline is also important.
Percutaneous leads and laminotomy leads are the two most common types of lead designs that provide conductors that deliver stimulation pulses from an implantable pulse generator (IPG) to distal electrodes adjacent to the nerve tissue. As shown in
As shown in
In one embodiment, a medical lead comprises a lead body for conducting electrical pulses and a paddle. The paddle includes an intermediate metal layer, at least an insulative polymer backing layer, and an insulative polymer covering layer. The intermediate metal layer comprises a plurality of features defined by gaps in the metal material in the metal layer such that each feature is electrically isolated from each other feature, wherein each feature includes a respective connector element that is electrically coupled to at least one conductor within the lead body, wherein a portion of the insulative polymer covering layer is exposed above each feature to define a respective electrode for the corresponding feature. Also, the paddle possesses shape memory to cause the paddle to assume a substantially planar orientation when the shape memory is in a relaxed state.
The foregoing has outlined rather broadly certain features and/or technical advantages in order that the detailed description that follows may be better understood. Additional features and/or advantages will be described hereinafter. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the appended claims. The novel features, both as to organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the appended claims.
The width of paddle 200 is sufficient to provide suitable spacing between the two sets of electrodes 203 to enable stimulation of the pertinent nerve fibers across the physiological midline of the patient. The design of paddle 200 enables paddle 200 to be substantially maintained at a desired position within the patient's epidural space. Moreover, the design of paddle 200 ensures that electrodes 203-1 through 203-8 will remain in fixed relative positions, e.g., electrodes 203-1 through 203-4 cannot be offset longitudinally from electrodes 203-5 through 203-8.
Paddle 200 includes guide structures 202-1 and 202-2 which are proximate to distal end 201 of the paddle. Guide structures 202-1 and 202-2 cause paddle 200 to fold upon itself when the guide structures 200 contact the lumen of an insertion tool. In some embodiments, the guide structures 202-1 and 202-2 are implemented by scribing longitudinal elements in the conductive material. When paddle 200 contacts the inner surface of the insertion tool, the longitudinal elements distribute force into the body of paddle 200 according to the shape of the respective longitudinal elements. Additionally, guide structures 202-1 and 202-2 are preferably implemented to possess different amounts of rigidity (e.g., due to the shape of the respective guide structures 202, the thickness of their respective longitudinal members, etc.). The difference in the amount of rigidity controls the manner in which paddle 200 folds. As will be discussed in greater detail below, one side of paddle 200 folds over the other side in a substantially lateral manner thereby minimizing the amount of open space within the epidural space required for paddle 200 to unfold.
In the embodiment shown in
In a similar manner, if paddle 200 needs to be removed from the patient, distal end 205 and guide structures 202-2 and 202-3 are provided. Specifically, proximal end 205 can be pulled by lead body 410 into the same or similar tool as used to insert paddle lead 200. When guide structures 202-2 and 202-3 experience force due to contact of paddle 200 with the inner wall of the tool, segment 210 once again folds over segment 220 thereby enabling paddle 200 to be withdrawn from the patient's epidural space through the tool. Accordingly, it is not necessary to perform a partial laminectomy procedure for the insertion or removal of paddle 200.
Numerous variations upon the design shown in
Also, paddle 200 could include more than two segments with all or some of the segments folding when inserted into a suitable tool. Although eight electrodes are shown in
In step 302, a coating of urethane (or a similar polymer) is spin coated on one side of the conductive material for the purpose of achieving a surface with greater adhesive qualities. In step 303, a urethane film (or any other suitable biocompatible polymer) is applied to the same side as the spin coat and is laminated to the conductive material. The urethane film and coating provide an insulative layer to electrically isolate the conductive material. The urethane film preferably has a thickness of preferably 25.4 to 152.4 microns (one to six mils).
In step 304, the paddle form is created by scribing the paddle form in the conductive material using a suitable laser (e.g., a programmable YAG laser system). A separate strip or “feature” of conductive material is defined in a pattern definition for each electrode that extends from a respective connector element 206 (shown collectively as 206-1 through 206-8 in
The pattern definition is preferably provided to a programmable laser system. The programmable laser system then applies pulses of energy according to the defined pattern to ablate the conductive material between each strip of conductive material. The application of laser pulses is controlled to ablate the conductive material at the defined locations without cutting completely through the urethane film behind the ablated conductive material. The lamination between the urethane film and the conductive material holds the separate strips or features of conductive material at the defined locations. Also, upon completion of the application of laser pulses to paddle 200, each strip of conductive material is electrically isolated from every other strip or feature due to the laser scribed separations between them and the insulative characteristic of the urethane film. In an alternative embodiment, photo-etching techniques could be employed to create the paddle form. For example, the paddle form could be created using a photoresist and chemical etching in lieu of laser scribing. In another alternative embodiment, micro-printing is employed to create the paddle form.
In step 305, a spin coat of urethane is applied over the conductive material on the side opposite to the urethane laminate layer. The coating of the urethane material electrically insulates the top of paddle 200. In step 306, electrodes 203 are defined by removing the urethane material of the applied coating at the respective locations thereby exposing the conductive material at those locations. The removal of the urethane material may occur using the programmable laser. Alternatively, a separate CO2 laser could be utilized for exposure of the conductive material and/or masked plasma etching. In step 307, connector elements 206 are exposed on one or both sides of paddle 200.
After the completion of paddle 200 according to the flowchart of
On the distal end of a medical lead, openings in the outer body and in the insulative coating of the conductors are made at suitable locations. Conductive material can be provided within the openings to provide an electrical path from the conductors to the surface of the lead. The exposed connector elements 206 of paddle 200 are preferably coupled to the lead conductors at these locations to create the electrical connection between the conductors of the lead and electrodes 203. Alternatively, a wire connection could be employed between each conductor of the lead and a respective connector element 206. Additional details regarding specific medical leads and lead fabrication methods are available in U.S. Pat. No. 6,216,045 entitled “Implantable lead and method of manufacture,” which is incorporated herein by reference. It shall be appreciated that paddle designs according to the present invention can be implemented with any type of suitable medical lead.
One advantage of assembly 400 is the minimization of volume displacement associated with the folding and unfolding of the paddle. Reference is made to
As shown in
The distal end of paddle 200 of lead assembly 400 is inserted within insertion tool 500 as shown in
Although some representative embodiments have been discussed in terms of neurostimulation applications, alternative representative embodiments could be employed for other medical applications. For example, in one alternative embodiment, a paddle structure could be adapted for any suitable type of cardiac stimulation such as defibrillation and pacing. The paddle structure could be inserted through the vascular system of the patient using a suitable catheter and introduced within a suitable cardiac region. The paddle structure then could be adapted to unfold upon exiting the catheter to contact the cardiac tissue to be stimulated. In other alternative embodiments, the paddle could be utilized for cardiac mapping and/or tissue ablation.
Some representative embodiments may provide a number of advantages. Some representative embodiments provide a paddle that can be inserted into and removed from the epidural space of a patient without requiring a partial laminectomy. Furthermore, some representative embodiments provide a method of fabricating a paddle design that is highly repeatable and efficient. The fabrication method further does not necessarily require the use of any overly caustic chemicals.
Although representative embodiments and advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from this disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized without departing from the scope of the appended claims. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
Claims
1. A medical lead for delivering electrical stimulation to tissue of a patient, the medical lead comprising:
- a lead body for conducting electrical pulses through a plurality of conductors; and
- a paddle for delivering the electrical pulses from the plurality of conductors to tissue of the patient, wherein the paddle includes: (i) an intermediate metal layer; and (ii) at least an insulative polymer backing layer and an insulative polymer covering layer; wherein the intermediate metal layer comprises a plurality of features defined by gaps in the metal material in the metal layer such that each feature is electrically isolated from each other feature, wherein each feature includes a respective connector element that is electrically coupled to at least one conductor within the lead body, wherein a portion of the insulative polymer covering layer is exposed above each feature to define a respective electrode for the corresponding feature; wherein the paddle possesses shape memory to cause the paddle to assume a substantially planar orientation when the shape memory is in a relaxed state.
2. The medical lead of claim 1 wherein the guide structures are scribed into at least one of a plurality of separate features of the paddle, the guide structures being adapted to control folding or unfolding of the paddle.
3. The medical lead of claim 1 wherein intermediate metal layer possesses a thickness of approximately one mil.
4. The medical lead of claim 1 wherein the insulative polymer backing layer possesses a thickness of approximately 25.4 to 152.4 microns.
5. The medical lead of claim 1 wherein the paddle comprises a slit in the paddle and the first longitudinal portion folds over the second longitudinal portion upon application of force to the paddle.
6. The medical lead of claim 1 further comprising:
- a support structure that extends substantially along a longitudinal direction of the paddle, the paddle being affixed to a flat surface of the support structure and the medical lead being affixed to a concave surface of the support structure.
7. The medical lead of claim 6 wherein the support structure is an extruded or injection-molded biocompatible polymer structure.
8. A method of fabricating a paddle adapted for electrical stimulation of tissue of a patient, the method comprising:
- providing a layer of conductive material;
- laminating a film of insulative material on a first side of the layer of conductive material;
- creating a paddle form in the layer of conductive material, the paddle form including: (i) at least a first segment and a second segment with a plurality of electrodes on each segment; and (ii) one or more guide structures proximate to at least one end of the paddle form, wherein the one or more guide structures are adapted to distribute force into a body of the paddle form to control folding or unfolding of the paddle form; and
- providing an insulative layer over the paddle on a second side of the layer of conductive material;
- wherein the paddle possesses shape memory that causes the paddle to assume a substantially planar state when the shape memory is in a relaxed state.
9. The method of claim 8 wherein the providing an insulative layer comprises:
- spin coating an insulative polymer on the paddle.
10. The method of claim 8 wherein the creating comprises:
- laser scribing the conductive material without completely cutting through the film of insulative material.
11. The method of claim 8 further comprising:
- removing portions of insulative material to expose conductive material corresponding to the plurality of electrodes.
12. The method of claim 8 wherein the guide structures are longitudinal elements that distribute force into the body of the paddle to cause the paddle to fold.
13. The method of claim 8 further comprising:
- mechanically coupling the paddle to a support structure; and
- electrically coupling the electrodes of the paddle to conductors of a medical lead.
14. The method of claim 13 wherein the medical lead is mechanically coupled to a concave surface of the support structure and the paddle is mechanically coupled to a flat surface of the support structure.
15. The method of claim 8 wherein, after the creating the paddle form is performed, the conductive material occupies substantially all of the surface area of the paddle.
16. The method of claim 8 wherein the paddle form comprises a slit in the conductive material and the first segment folds over the second segment when either of the guide structures experiences force by contact of the paddle with an interior surface of an insertion tool.
17. The method of claim 16 wherein the slit in the conductive material is covered by a highly elastic polymer material or hydrogel material.
18. A method of positioning a paddle-style lead in a patient for electrical stimulation of tissue of the patient, comprising:
- inserting a paddle structure of the lead into an insertion tool or catheter, the paddle structure including at least a first longitudinal portion and a second longitudinal portion, the first and second longitudinal portions defining respective substantially planar surfaces having a plurality of electrodes, wherein contact of the paddle structure with an interior portion of the insertion tool or catheter causes one or several memory shape elements in the paddle structure to be subjected to a compressive force; and
- advancing the paddle structure in a folded state through the insertion tool or catheter to exit the insertion tool or catheter within the patient, wherein the planar surfaces of the first and second longitudinal portions are disposed substantially adjacent to each other in the folded state;
- wherein release of the compressive force on the one or several shape memory elements upon the exiting of the paddle from the insertion tool or catheter causes unfolding of the paddle structure to occur in a substantially lateral direction.
19. The method of claim 18 wherein the paddle structure comprises one or more guide structures that possess an arcuate shape to distribute force into the second longitudinal portion and one or more guide structures that possess a substantially linear shape to distribute force into the first longitudinal portion.
20. The method of claim 19 wherein the one or more guide structures of the first and second longitudinal portions cause the paddle to possess a differential in rigidity between the first and second longitudinal portions.
Type: Application
Filed: Feb 9, 2007
Publication Date: Aug 16, 2007
Inventor: John W. Swanson (Portland, OR)
Application Number: 11/673,001
International Classification: A61B 6/00 (20060101);