Abstract:
A straight-forward and tool-less mechanism is provided for securing lead wires to an implantable neurostimulator, or similar medical device. In one embodiment, a clip lock mechanism is pivotally connected to the enclosure of the medical device, which enclosure also includes at least one receptacle with contacts to the components within the device. The proximal end of the lead wires terminate in a connector, including at least one plug and at least one pin with contacts corresponding to the electrodes or other devices along the distal end of the lead. The pin is inserted into the receptacle, thus completing the connection between the pin and receptacle contacts, and the clip is pivoted over the plug. The plug preferably has depressions that provide a clear visual and tactual indication of the position of the properly placed clip.

Description:
This application claims the benefit of U.S. Provisional Application Serial No. 60/180,433, filed Feb. 4, 2000, which application is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to a medical device for implantation in a living body, and more particularly relates to a clip lock mechanism for lead wires used with an implantable medical device. 
     BACKGROUND OF THE INVENTION 
     A variety of devices exist which make use of electrical lead wires, i.e., leads or lead extensions, that detachably connect to an electrical device. For instance, numerous medical devices, such as neural stimulation devices, cardiac pacemakers and defibrillators, commonly establish a connection between an implanted lead or lead extension (herein, both will be referred to as ‘lead’) and an implanted electronic package. In a typical pacemaker, the proximal end of a lead is connected to an implantable pulse generator, while the distal end, containing one or more electrodes, is typically inserted in or on the heart. 
     It is preferable that the leads be detachable from the devices so that either may be implanted, explanted or replaced without affecting the other. Detaching and attaching the lead to the device should be simple, to reduce surgical time, and evident, to limit chances for error. In addition, it is preferable that attachment and detachment be possible without a tool. While the lead is attached to the device, the connection should be strong enough to resist flexing and any other forces that could unintentionally disconnect the lead. 
     The connection between a lead and an implantable device is preferably compact and light-weight, and it must be constructed of biocompatible materials and in such a way so that the electronic circuitry can survive for extended periods of time without any significant changes in performance. In addition to the connection being mechanically reliable, so that a lead does not inadvertently become disconnected from the device, it must also ensure proper electrical communication between the device and lead(s) at all times. 
     It is known in the art to use a set screw for each connection, often providing electrical contact, as well as mechanical connection, between the lead(s) and the device. This arrangement requires delicate and time-consuming surgical procedures ensuring that the set screw is secure yet does not strip, and that the device is not damaged. In addition, this arrangement is rather bulky. Also, sealing set screws from the surrounding body fluids is often difficult, as the seal may be damaged during tightening of the set screw. 
     There exists a need in the art for a compact, easy to operate, fast, and reliable way to detachably secure leads to implantable electronic packages. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention addresses the above and other needs by providing a clip lock mechanism for securing lead wires, i.e., lead or lead extension, to an, implantable neurostimulator, or similar implantable device. 
     The clip lock mechanism of the present invention preferably applies to an enclosure made of a case and a header. However, the invention also may be used with one-piece devices, i.e. headerless enclosures, as well as with multi-piece enclosures. With the case and header enclosure, the case is made of a biocompatible material (e.g. titanium or ceramic) and houses an electronic circuit assembly (hereafter also referred to as “electronic circuitry”, “circuitry”, or “electronics”). 
     The header, which is typically made of polymeric material, such as epoxy, is secured (e.g. molded in place) to the case. The header has a plurality of electrical connectors (electrical feed-through terminals) passing through it connecting to the electronic components inside the case. In addition, the header has a receptacle(s) where a lead connector(s) at the proximal end of a lead(s) or lead extension(s) is inserted to form the electro-mechanical connection between the electronics and leads. 
     The clip lock mechanism provided by the present invention is typically made of a medical grade metal such as 316 stainless steel or nitinol. The clip lock mechanism pivotally connects to the header. The lead connector (at the proximal end of a lead or lead extension) comprises at least one pin and a plug. Once the pin(s) of the connector have been inserted into the receptacle, the clip is pivoted over the lead plug. The plug preferably has depressions that provide a clear visual and tactual indication of the position of the properly placed clip. Advantageously, manipulation of the clip is straight-forward, simple, and tool-less, yet the clip is reliably locked in place and requires intentional manipulation to be unlatched. 
    
    
     BRIEF DESSCRIPTION OF THE DRAWINGS 
     The above and other aspects, features, and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
     FIG. 1A is a front view of a medical device of the type that may be used with the present invention; 
     FIG. 1B is a side view of the medical device of FIG. 1A; 
     FIG. 2 is a front view of a lead connector, prior to insertion into the device of FIGS. 1A and 1B; 
     FIG. 3A is a front view of the medical device including the clip lock mechanism of one embodiment of the present invention; 
     FIG. 3B is a side view of the medical device including the clip lock mechanism of one embodiment of the present invention; 
     FIG. 3C is a side view of the clip lock mechanism of one embodiment of the present invention; 
     FIG. 4A is a front view of the lead connector of FIG. 2 installed into the device of FIGS. 3A and 3B, prior to locking the clip into place over the lead plug; 
     FIG. 4B is a front view of the lead connector of FIG. 2 installed into the device of FIGS. 3A and 3B, with the clip locked into place over the lead plug; 
     FIG. 5A is a front view of an alternative configuration of the clip lock mechanism of another embodiment of the present invention and medical device of the type that may be used with the present invention; 
     FIG. 5B is a front view of an additional alternative configuration of the clip lock mechanism of another embodiment of the present invention and medical device of the type that may be used with the present invention; 
     FIG. 6A is a front view of a clasp of another embodiment of the present invention, and medical device of the type that may be used with the present invention; 
     FIG. 6B is a side view of the clasp of FIG. 6A of another embodiment of the present invention, and medical device of the type that may be used with the present invention; 
     FIG. 7A is a front view of a cam mechanism of another embodiment of the present invention, and medical device of the type that may be used with the present invention; 
     FIG. 7B is a side cross-sectional view of the cam mechanism taken along line  7 B— 7 B of FIG. 7A of another embodiment of the present invention, with the cam mechanism in an unlocked position, and medical device of the type that may be used with the present invention; 
     FIG. 7C is a side cross-sectional view of the cam mechanism taken along line  7 C— 7 C of FIG. 7A of another embodiment of the present invention, with the cam mechanism in a locked position, and medical device of the type that may be used with the present invention; 
     FIG. 8A is a front view of a spring-loaded pin of another embodiment of the present invention, and medical device of the type that may be used with the present invention; 
     FIG. 8B is a side cross-sectional view of the spring-loaded pin taken along line  8 B— 8 B of FIG. 8A of another embodiment of the present invention, with the spring of the spring-loaded pin in a compressed position, and medical device of the type that may be used with the present invention; 
     FIG. 8C is a side cross-sectional view of the spring-loaded pin taken along line  8 C— 8 C of FIG. 8A of another embodiment of the present invention, with the spring of the spring-loaded pin in a relaxed position, and medical device of the type that may be used with the present invention; and 
     FIG. 9 is a block diagram that illustrates the various connections between components of a typical medical device of the invention. 
    
    
     Corresponding reference characters indicate corresponding components throughout the several views of the 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 reference to the claims. 
     For illustration purposes, the following description of the present invention is shown in conjunction with an implantable electronic package or device  10 , shown, e.g., in FIG.  1 A. The implantable electronic device  10  typically comprises a sealed medical device that carries out a desired medical function, e.g., stimulation of the spinal cord or other nerves. The device  10  preferably comprises an enclosure made of a case  14  enclosing an electronic and/or mechanical assembly (not shown in FIG. 1A) and a header  18  for closing the package. However, the device may be a one-piece enclosure, i.e., headerless, or a multiple piece enclosure. The electronic or other components are configured in a desired circuit and/or mechanical relationship so that the device  10  is able to carry out its intended function, e.g., neuro-stimulation, sensing, monitoring, or the like. 
     The case  14  is made of a biocompatible material, such as titanium. It should be understood, however, that the case  14  could be made from other suitable implantable materials, such as ceramic. As illustrated in FIGS. 1A and 1B, the case is preferably rounded, with smooth curved transitions that eliminate or minimize edges or sharp corners. The case preferably has a maximum circular diameter D of about 55 mm, and more preferably only about 45 mm (or dimensions encompassing a similar area) or less. The maximum thickness W of the case is preferably about 10 mm, and is more preferably only about 8 mm or less. However, case  14  may be formed to any desired shape and dimension by processes known to those skilled in the art of forming the chosen biocompatible material. 
     The electronic assembly  16  shown in FIG. 3A includes a circuit board on or in which various individual components are mounted, formed, or otherwise carried. Components may include, e.g, a permanent magnet, an antenna coil, integrated circuit (IC) chip(s), capacitors, resistors, inductors, transistors, and the like. The circuit board is connected at one end to a plate which is configured to mate with the open edge of the case  14 . A bond between the plate and case  14 , typically made by laser welding or other known process, holds the assembly in place within case  14 . Representative assembly techniques that may be used to hermetically seal an electronic package within a case are taught in U.S. Pat. No. 4,991,582, incorporated herein by reference. 
     Header  18 , when used, is made of biocompatible material, typically a polymeric material such as epoxy, polyurethane, or polysulfone. A plurality of electrical connectors (electrical feed-through terminals  27 ) pass through header  18 , connecting to the electronic assembly  16  inside the case  14 . A power source, e.g., a rechargeable battery  17 , is also typically contained within case  14  and connected to assembly  16 . Ultimately the components inside case  14  need to be connected to the electrode arrays or other devices at and/or along the distal end of a lead(s). The lead, i.e., lead system, typically comprises lead wires within a lead cable  24 , lead blank(s) with electrode arrays or other devices at and/or along its distal end, and possibly lead extension(s). Thus, lead cable  24  may enclose lead wires in a lead or in a lead extension. At the proximal end of the lead cable  24  is a lead connector  22  (FIG.  2 ). Header  18  has receptacle(s)  20  where the lead connector  22  is inserted to form the electro-mechanical connection between the components inside case  14  and lead wires within lead cable  24 . 
     As is known in the art, header  18  may be created by inserting case  14  including the electronic/mechanical assembly  16  and feed-through terminals  27  into a mold, wherein the material of header  18  is molded in place. A mold insert, also known in the art, is preferably used to retain a space for the lead receptacle(s)  20 . Alternatively, the space for the receptacles  20  may be drilled out after molding of the header  18 . As is known in the art, a suture hole(s) may be included at the top of the header, to assist in holding the device in a desired implanted location. This suture hole(s) may be formed in a similar manner as described above for the lead receptacle(s). 
     Turning now to FIG. 2, lead connector  22  connects a plurality of electrical lead wires in a lead cable  24  to the electronic or other components  16  inside of device  10  through the electrical feed-through pins or terminals  27  located in header  18 . For instance, in the case of a neural stimulator, device  10  includes n feed-through terminals to allow electrical contact to be individually made from inside the hermetically-sealed device with the n electrodes that form part of the lead system. The n electrodes are typically assembled into an array at the distal end (not shown), and/or spaced apart along the length of the lead cable  24 . 
     As indicated earlier, connector  22  is typically found at the proximal end of an implantable lead cable  24 . Connector  22  typically includes at least one lead pin  26  and lead plug  28 . At the distal end (not shown) of the lead cable  24 , or along the length of the lead cable  24 , there will typically be an array of electrodes, or other components (e.g., a sensor) to which the components within device  10  must be electrically connected. 
     Each electrode or other component is connected to a suitable wire within the lead cable  24 . Each wire that passes through lead cable  24  to an electrode or other electrical component is connected to a lead contact  30  of the lead connector  22  at the proximal end of the lead cable  24 . Lead contacts  30  are typically made of, for instance, stainless steel, titanium, tantalum, or noble metal(s) such as platinum or platinum iridium. Separating lead contacts  30  are electrical insulators  31 , typically made of polyurethane, silicone, epoxy, or polytetrafluorethylene (PTFE). Lead contacts  30  are formed along the length of the lead pin  26  so as to make electrical contact with lead receptacle contacts  21  formed along the inside of receptacle  20  when the connector  22  is inserted in receptacle  20 . Lead receptacle contacts are in turn in electrical contact with feed-through terminals  27 , and thus with assembly  16 . 
     For ease of handling, and in this case, also working in conjunction with the clip lock mechanism, a lead plug  28  is used at the transition from the lead cable  24  to the lead pin  26 . The lead plug  28  is typically cast or molded of an elastomeric or rigid polymer material such as polyurethane or silicone. Other configurations of lead contacts, electrical insulators, and lead plugs within a lead connector, as are known in the art, may also be useful with the present invention. The process of making a connector such as lead connector  22  is known to those of skill in the art. 
     It is the function of the connector  22  to electrically connect the lead wires within the lead cable  24  (and hence to electrically connect the electrodes or other components at the distal end or along the length of the lead cable  24 ) to the feed-through terminals  27  through the lead receptacle contacts  21  which are located in header  18 . That is, it is the function of the connector  22  to ultimately connect the distal electrodes/sensor(s) to the assembly  16  housed within the device  10 , thereby allowing the device  10  to perform its intended function. Thus, each wire within the lead cable  24  is electrically connected to a corresponding contact point  30  placed along the length of lead pin  26 . The metal contacts  30  in the connector  22  are positioned so as to match or “align” with corresponding lead receptacle contacts  21 , and are thus in electrical contact with feed-through terminals  27  of the header  18  when the connector  22  is placed in the receptacle  20 . Lead contacts  30  of lead connector  22  are configured to be flush with the inside surface of lead receptacle  20 . Thus, when lead connector  22  is fully inserted into lead receptacle  20 , with lead plug  28  being flush against header  18 , each lead contact  30  along the lead pin  26  aligns with and electrically contacts a respective conductive lead receptacle contact  21  of header  18 . 
     Turning again to FIGS. 3A and 3B, the clip lock mechanism  32  of the present invention is shown. Clip  32  is preferably made of a durable, biocompatible, medical grade material, more preferably of  316  stainless steel or similar metal or metal alloy, and most preferably of nitinol. The clip  32  comprises a wire, of approximately 1 mm or less diameter, or any suitable diameter, bent into the shape of a rectangle with rounded corners. The material properties and cross-sectional geometry of the wire should be such that the clip is strong enough to endure assembly, handling, and use, while being as unobtrusive as possible. To impart the necessary resilience to the clip, a steel wire is spring-tempered via standard means known to those of ordinary skill in the art of forming and treating steel, and similarly, a nitinol wire is formed and treated via standard means known to those of ordinary skill in that art. An advantage, inter alia, of the clip locking mechanism of the present invention is its simplicity and associated small size, low profile, tool-less activation, and lightweight design, especially as compared to the prior art mechanisms. 
     The minimum width of clip  32  along the shorter sides of the rectangle should be determined by the width of the lead plug  28 . The minimum length of clip  32  along the longer sides of the rectangle should be determined by the length of the lead plug  28 . The length and width of clip  32  should allow the clip to pivot over and secure the lead plug  28  to device  10 , as shown in FIGS. 4A and 4B. Lead plug  28  preferably includes a groove  29  or indentations along its length, or more preferably, about its periphery, allowing clip  32  to snap or settle snugly into place around the plug  28 , securing plug  28  to header  18 . 
     As best seen in FIG. 3C, a break, or gap, along the generally rectangular clip  32  is used for securing the clip to the header  18  of the device  10  (or directly to the case of a headerless device). Assuming plug  28  is longer than it is wide, as in FIG. 2, the break or gap in clip  32  would be along one of the shorter sides of the generally rectangular clip shape, preferably at or near the midpoint of the side. A hole  19  or indentations in the header  18 , preferably just slightly larger in diameter than the wire of the clip, allow the ends of the wire to be inserted into the hole or indentations. These holes  19  or indentations could be drilled after molding of header  18 . Alternatively, the holes  19 , indentations, and/or clip may be molded in place during molding of the header  18 . 
     During insertion of lead connector  22  into receptacle  20 , clip  32  is in an unlocked position, as shown in FIG.  4 A. After the lead plug  28  is flush against header  18 , clip  32  may simply be pivoted with a finger in the direction of arrow  34  into place over plug  28 , as shown in FIG.  4 B. Of course, the clip may be manipulated with a tool, if desired, but is configured in such a way that a tool is not necessary. As previously described, grooves  29  or indentations along plug  28  allow clip  32  to be firmly snapped into place and secured in position over the connector. The connector is thus locked into place, so that only intentional manipulation of the clip will disconnect the lead. Once the connector  22  is fully inserted into the receptacle  20  of header  18 , both the lead pin  26  and the connections within the header are generally protected from body fluids via a seal provided by the receptacle and pin mating shapes and their materials (e.g., polyurethane, silicone, epoxy, PTFE). 
     If ever there is a need to remove, explant, or replace a lead, lead extension, or device  10 , the lead cable  24  may be detached from the device  10  by simply pivoting the lead clip  32  in the direction opposite arrow  34 , and then pulling connector  22  from the receptacle  20 . The simple and sure mechanism of the present invention results in reduced surgical time and possible error, while ensuring a secure connection between the electrodes or other devices at or along the distal end of the lead(s) and the components within device  10 . 
     Other clip shapes, sizes, and configurations will be apparent to those of skill in the art, such as a clip of generally oval or circular shape or a clip including a tab for ease of manipulation. Likewise, the clip may have a break in a position anywhere along its length, and be attached to the device in any appropriate way (e.g., the clip may extend through a hole in the device or the clip may be formed in place) as necessitated by the clip design. Alternatively, if the wire that forms the clip is welded together at its ends, the clip may not have a break anywhere along its length. In addition, rather than a pivoting wire, secured at all times through the device, a clip could be connected to the device at only one end. Once the connector was inserted, the wire clip could swing into place over the plug, and the free end of the wire inserted into a hole or indentation in the device. 
     Furthermore, the clip may be attached to the header or device in various locations. One alternative configuration is seen in FIG.  5 A. In this alternative configuration, the base of header  18  extends entirely across case  14 , so that the underside of lead plug  28  contacts a shoulder portion  33  of the header when connector  22  is inserted into receptacles  20 . In the previous embodiment, as shown in FIG. 3A, the header extends across case  14  only to a position flush with the openings to receptacles  20 , and there is no shoulder portion. Thus, in the previous configuration, the underside of lead plug  28  directly contacts case  14 . 
     As mentioned earlier, the present invention also applies to use with a “headerless” device, as seen in FIG.  5 B. In addition, the clip may be attached via means other than insertion into a hole or indentation. For instance, the clip may be attached to the device via a hinge type mechanism. Alternatively, the clip may be a two piece device comprising a rod attached to the device and a generally U-shaped piece of wire that pivotally connects to the ends of the rod. 
     Alternative embodiments of the clip mechanism include a clasp  36  that secures to the lead pin once the pin is inserted in the lead receptacle  20  (FIGS.  6 A and  6 B). A slot provided in device  10  would allow clasp  36  to slide into place around the lead pin, which may be provided with indentations for increasing the reliability of the connection. Clasp  36  may include a clasp slot  38  and clasp pin  40  that allow the clasp to release the lead pin without the clasp separating from device  10 . 
     A further embodiment, shown in FIGS. 7A,  7 B, and  7 C, comprises a rotating cam mechanism  42  comprising a part of the device enclosure, located between the lead receptacle  20  and the outer surface of the enclosure, with a tab  44  for actuating the cam. As mentioned earlier and illustrated with this embodiment, the present invention relates not only to the use of multiple receptacles  20  for multiple lead pins  26 , but also to the use of a single receptacle  20  for a single lead pin  26 . As shown in FIG. 7B, before and during insertion of the lead pin  26  into the lead receptacle  20 , the cam is in an unlocked position with tab  44  protruding from the enclosure. After the pin is in place within the receptacle, tab  44  is actuated (with a tool or preferably with a finger) into a locked position, as shown in FIG.  7 C. The cam thus provides sufficient force to hold the pin securely within the receptacle. For increased reliability of the connection, the pin may have an indentation that fits a portion of the cam mechanism when the cam mechanism is in locked position. 
     In yet another embodiment, shown in FIGS. 8A,  8 B, and  8 C, a spring-loaded pin  48  comprises a part of the device enclosure, located between lead receptacle  20  and the outer surface of the enclosure. Spring-loaded pin  48  typically comprises a helical compression spring  50  biased into a position that causes the distal tip  52  of spring-loaded pin  48  to protrude into lead receptacle  20 . During insertion into lead receptacle  20  (shown in FIG.  8 B), lead pin  26  pushes the distal tip  52  of spring-loaded pin  48  in a proximal direction, which in turn compresses spring  50 . Once lead pin  26  is fully inserted (shown in FIG.  8 C), distal tip  52  is pushed distally by spring  50  into depression  54  in the side of lead pin  26 . Depression  54  is located in lead pin  26  to be in alignment with spring-loaded pin  48  when lead pin  26  fully inserted, thus securing lead pin  26  in proper position within lead receptacle  20 . Spring-loaded pin  48  is preferably fully contained within the device but may also have at its proximal end a head which protrudes through the outer surface of the enclosure, by which the attitude of spring  50 , distal tip  52 , and lead pin  26 , may be determined. Suitable spring-loaded pins are commercially available from Interconnect Devices, Inc. of Kansas City, Kans. 
     As will be evident to one of ordinary skill in the art, the above clip lock  32 , clasp  36 , cam mechanism  42 , spring-loaded pin  48 , and similar mechanisms apply to connections other than between an implantable device and a lead or lead extension. For instance, other connections found between components of a typical implantable medical device are illustrated in the block diagram of FIG.  9 . Some of these components are implanted and some are external. The implanted components may include implanted medical device  100  which interfaces with an electrode array(s) positioned on one or more implanted leads  110 . This interface may occur through one or more implanted lead extensions  120 . For testing and/or fitting purposes, the electrode array of implanted lead(s)  110  may also interface with an external trial device  140  through one or more percutaneous lead extensions  132 . During implant surgery, external trial device  140  is typically connected to percutaneous lead extension(s)  132  through external cable(s)  134 . Each interface between components is illustrated in FIG. 9 as a line with an arrow and, whether internal or external, may use clip lock  32 , clasp  36 , cam  42 , spring-loaded pin  48 , or similar mechanism to ensure a secure connection. Additional alternative means will be apparent to those skilled in the art from reading the specification and reviewing the drawings herein, without deviating from the spirit of the instant invention. 
     Thus, the invention provides a simple, yet reliable and easy-to-use approach for detachably securing an implantable device to an implantable lead, which lead has multiple contacts therein (which contacts respectively attach to electrodes or other devices or components at a distal end, or along the length of, the lead). The locking clip mechanism of the present invention also provides a secure and evident connection without the use of a tool, thus reducing surgery time, risk of infection, and likelihood of error. With the clip in place, the connection is reliable electrically and mechanically, so that it resists body fluids, flexing, and other forces, yet it is compact and light-weight. 
     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. For example, the case may also be used to house or protect other types of assemblies, in addition to electronic circuit assemblies. For example, a housing may be used to protect an implantable hydraulic assembly, or an implantable electromechanical pump (e.g., an insulin pump), in which certain components need to be protected from the environment within the human or other body. Such assemblies may communicate with external components via a header assembly and lead system as described above which has hermetic feed-through posts, e.g., hermetic pipettes for communicating a fluid to an electromechanical pump and/or hermetic electrical feedthrough terminals and connectors for making electrical connection with electronic circuitry.