Abstract:
A hub ( 200 ) includes a first lead receptacle having a plurality of contacts ( 280 ) for electrically coupling a lead to an implantable electrical device. The hub further contains a second lead receptacle having a plurality of contacts for electrically coupling a lead to the implantable electrical device. At least one of the plurality of contacts of the first receptacle is a contact of the second receptacle. Such a configuration may allow for the overall size of the hub to be reduced relative to a hub where each discrete contact of the hub corresponds to a discrete contact or electrical channel of the implantable electrical device.

Description:
RELATED APPLICATION 
     This application is a U.S. National Stage filing under 35 U.S.C. 371 of copending PCT Application Serial No. PCT/US2010/039299, filed Jun. 21, 2010, which claims the benefit of priority to U.S. provisional patent application No. 61/218,452, filed Jun. 19, 2009, both of which applications are incorporated herein by reference to the extent that they do not conflict with the present disclosure. 
     FIELD 
     This disclosure relates to implantable medical systems employing implantable medical leads; and more particularly, to hubs for operably coupling implantable medical leads to active implantable medical devices such as implantable medical signal generators. 
     BACKGROUND 
     Many implantable medical devices, such as neurostimulators, pacemakers and defibrillators, transmit electrical signals to provide therapy to a patient. Implantable medical leads deliver signals generated from such devices to tissue of the patient via one or more electrodes of the lead. Often the electrodes of the leads are located at a considerable distance from the implant location of the electrical signal generator device. If multiple leads are required or desired, separate subcutaneous paths may need to be tunneled for each lead, resulting in time consuming surgical procedures and potential patient discomfort. 
     In some situations a lead extension is employed to couple the lead to the signal generator. The lead extension may allow for connection of the lead in closer proximity to the tissue to which the generated electrical signal is applied, reducing the extent of tunneling required for the lead. However, the extension still needs to be tunneled through the patient. 
     When it is desired to implant two leads in the same general tissue location, a bifurcated lead extension with a single proximal leg may be employed. In such cases, one tunneling path may be made from the implant location of the electrical signal generation to a location close to the target tissue for the lead extension. The two leads may then be coupled to the extension at this location and may then traverse relatively short distances in the patient. 
     However, if more than two leads are desired, a single bifurcated extension is not sufficient and more than one extended subcutaneous tunneling procedure may be required. Further, bifurcated lead extensions tend to be of limited flexibility in terms of functionality. For example, if a proximal end of a bifurcated lead extension has eight discrete electrical contacts for making eight discrete electrical connections with an electrical signal generator, the bifurcated distal end will have two separate lead receptacles, each having four internal contacts for making electrical connections with four discrete contacts of a lead. 
     BRIEF SUMMARY 
     The present disclosure describes, among other things, a hub for electrically coupling a lead with an active implantable electrical device. The hub may be used to operably couple two or more leads to the electrical device. The hub may be implanted in proximity to a tissue site to which a lead is implanted, reducing the number of extended tunneling procedures that need to be done. In various embodiments, the hub may couple leads having differing numbers of contacts. In some embodiments, the hub is configured to reduce overall size while still providing functional flexibility. 
     For example, a hub may include a first lead receptacle having a plurality of contacts for electrically coupling a lead to an implantable electrical device. The hub may further contain a second lead receptacle having a plurality of contacts for electrically coupling a lead to the implantable electrical device. At least one of the plurality of contacts of the first receptacle may be a contact of the second receptacle. Such a configuration may allow for the overall size of the hub to be reduced relative to a hub where each discrete contact of the hub corresponds to a discrete contact or electrical channel of the implantable electrical device. 
     By way of further example, a system may include an implantable electrical medical device and a hub. The implantable electrical medical device is capable of generating electrical signals on a plurality of discrete channels. The hub is configured to electrically couple one or more leads to the electrical device. The hub has a plurality of internal contacts electrically coupled to the electrical device, wherein each of plurality of internal contacts is electrically coupled to the device via one of the discrete channels. The number of internal contacts of the hub is greater than the number of discrete channels of the electrical device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view of a generic implantable electrical system. 
         FIG. 2  is a schematic drawing of showing a generic implantable electrical system and a generic target nerve in a patient. 
         FIG. 3  is a schematic drawing of a hub showing lead entry ports and internal contacts. 
         FIG. 4  is a schematic side view of a lead having contacts configured to electrically couple with internal contacts of a hub, such as a hub depicted in  FIG. 3 . 
         FIG. 5  is a schematic drawing of a hub showing tracks of bores. 
         FIG. 6  is a schematic drawing of a portion of hub showing a track of a bore and internal contacts disposed in the bore. 
         FIG. 7  is a schematic drawing of a hub showing lead entry ports and internal contacts. 
         FIG. 8  is a schematic drawing of a hub showing lead entry ports and internal contacts and leads inserted into the hub. 
         FIG. 9  is a schematic drawing of a hub showing lead entry ports and internal contacts and leads inserted into the hub. 
         FIGS. 10A-B  are schematic top views of a lead and a hub. 
         FIG. 11  is a schematic drawing of a hub showing lead entry ports and internal contacts. 
         FIG. 12  is a schematic drawing of a hub showing lead entry ports and internal contacts and leads inserted into the hub. 
     
    
    
     The drawings are not necessarily to scale. Like numbers used in the figures refer to like components, steps and the like. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number. In addition, the use of different numbers to refer to components is not intended to indicate that the different numbered components cannot be the same or similar. 
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration several specific embodiments of devices, systems and methods. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the devices, systems and methods described herein. The following detailed description, therefore, is not to be taken in a limiting sense. 
     All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure. 
     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” encompass embodiments having plural referents, unless the content clearly dictates otherwise. 
     As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     The present disclosure describes, among other things, a hub for electrically coupling a lead with an active implantable electrical device. The hub may be used to operably couple two or more leads to the electrical device. The hub may be implanted in proximity to a tissue site to which a lead is implanted, reducing the number of extended tunneling procedures that need to be done. In various embodiments, the hub may couple leads having differing numbers of contacts. In some embodiments, the hub is configured to reduce overall size while still providing functional flexibility. 
     The teachings presented herein are applicable to any implantable medical device system employing lead for delivering electrical signals to a tissue of a patient. For example, the system may include a neurostimulator, such as a peripheral nerve stimulator, a spinal cord stimulator, or a deep brain stimulator; a cardiac pacemaker or defibrillator; a gastric stimulator; or the like. It will be understood that the systems and devices described herein may be readily applied to systems employing leads for purposes of sensing, monitoring, recording, or the like. 
     Referring to  FIG. 1 , a schematic side view of a system  100  employing a generic lead extension  30  is shown. The system  100  also includes an implantable electrical signal generator  10  and a lead  20 . Implantable electrical signal generator  10  includes a connector header  40  configured to receive plug  50  at proximal end of lead extension  30  or other adaptor to couple lead  20  to electrical signal generator  10 . The distal end portion of lead extension  30  includes a connector  60  configured to receive proximal end portion of lead  20 . Connector  60  includes internal electrical contacts  70  configured to electrically couple extension  30  to lead  20  via electrical contacts  80  disposed on the proximal end portion of lead  20 . Electrodes  90  are disposed on distal end portion of lead  20  and are electrically coupled to electrical contacts  80 , typically through conductors (not shown). In general, a lead  20  may include any number of electrodes  90 , e.g. one, two, three, four, five, six, seven, eight, or sixteen. Typically, each electrode  90  is electrically coupled to a discrete electrical contact  80 . 
     A hub as described herein, in many respects, may be similar to a lead extension as described above with regard to  FIG. 1 . Referring now to  FIG. 2 , a hub  200  is electrically coupled to an implantable electrical device  10 , e.g. via a cable  150  carrying one or more conductors or wires (not shown). The cable  150  may include electrical contacts for electrically connecting to internal contacts of the device  10  when the cable  150  is inserted into the device  10 . As shown in  FIG. 2 , one or more leads  20  may be operably coupled to the hub  200 , which in turn operably couples the leads  20  to the device  10 . The leads  20  depicted in  FIG. 2  are positioned to apply electrical signals to a nerve  300 , such as a peripheral nerve, of a patient  1 . However, it will be understood that the leads  20  may be positioned or configured to apply or sense signals from any suitable tissue of the patient  1 . For example, in peripheral nerve stimulation for the treatment of pain, multiple leads may be used to target multiple pain areas or multiple nerve targets or multiple tissue targets (such as a scar or subcutaneous tissue areas). While not shown, it will be understood that more than one hub  200  may be operably coupled to one electrical device  10 . 
     Referring now to  FIG. 3 , a schematic drawing of some components of a hub  200  is shown. In the depicted hub  200 , only an outline of the hub housing  230 , lead entry ports  210  and internal contacts  280  are shown. It will be understood that hub  200  may include additional components, such as conductors electrically coupled to the contacts  280  and a cable for connection to an electrical device, even though such components are not shown.  FIG. 4  depicts a lead  20  having contacts  80  spaced apart in a manner suitable for electrically coupling to contacts  280  of a hub  200  as depicted in  FIG. 3 . Of course the contacts  280  of the hub  200  and the contacts  80  of the lead  20  may be spaced in any suitable manner. 
     Referring now to  FIG. 5 , tracks or bores  220 A,  220 B,  220 C,  220 D of the hub  200  are shown. The bores  220 A,  220 B,  220 C,  220 D are in communication with the lead entry ports  210  of the hub  200 . The bores  220 A,  220 B,  220 C,  220 D may be rectilinear or non-rectilinear. 
     With reference to  FIG. 6 , a schematic sectional view of a portion of the hub  200  through one of the bores  220 A is shown. As shown in more detail, openings of the lead entry ports  210 A,  210 B,  210 C are in communication with the bore  220 A. Contacts  280  are disposed in the bore  280  and are configured to electrically couple to contacts of a lead inserted into an entry port  210 A,  210 B,  210 C. The bore and each entry port  210 A,  210 B,  210 C forms a lead receptacle into which a lead may be inserted such that electrical contact can be made. Alternatively, a lead receptacle, such as those employed in implantable electrical signal generators or lead extensions, may be housed in the bore. In either case, the bore will be considered to form a lead receptacle for the purposes of the present disclosure. 
     Referring now to  FIG. 7 , which is an embodiment of the hub  200  depicted in  FIG. 3 , internal contacts  280  of the hub are numbered according to which channel of a 16-channel electrical signal generator the contacts  280  are configured to couple. As can be seen, the hub may have redundant contacts  280  capable of coupling to a given channel of the signal generator. Such a configuration allows for a great deal of flexibility regarding how leads may be operably coupled with the hub. 
     For example and with reference to  FIGS. 8-9 , some possible configurations of leads  20  employed in connection with a hub are shown. In  FIG. 8 , each lead  20  is coupled to a contact  280  that is coupled or couplable to a discrete channel of an electrical device, such as a signal generator. In  FIG. 8 , five leads  20  are operably coupled with the hub. Three of the leads are coupled to four contacts  280  (corresponding to channels  1 ,  2 ,  3 , and  4 ;  9 ,  10 ,  11 , and  12 ; and  13 ,  14 ,  15 , and  16  of the signal generator), and two of the leads  20  are coupled to two contacts  280  (corresponding to channels  5  and  6 ; and  7  and  8  of the signal generator). In  FIG. 9 , seven leads  20  are operably coupled with the hub. Note that some of the leads  20  are coupled to redundant contacts  280  (i.e., contacts corresponding to the same channel of the signal generator). For example, one lead  20  is coupled to contacts  280  corresponding to channels  1 ,  2 ,  3  and  4  of the signal generator and another lead  20  is coupled to contacts  280  corresponding to channels  1  and  2  of the signal generator. 
     In the embodiments, depicted in  FIGS. 7-9 , each of the contacts  280  of the hub corresponding to a given channel of the signal generator may receive a signal when a channel is activated. Alternatively, a switch or sensor may be employed to determine which contacts are coupled to leads, and only those coupled contacts may be activated when a channel sends a signal. In one example, the sensor could be electrical as when using an electrical impedance test in unipolar or bipolar fashion. When using this test, contacts  280  of the hub that are connected to a lead  20  will detect an impedance within a certain range suggestive of good electrical contact from the signal generator to the electrodes on the appropriate lead(s)  20 , for example between 100 and 4000 ohms. If a lead  20  is not connected to a contact  280  at the hub, the impedance test will detect an open circuit, i.e. a very high impedance value, and no stimulation would be delivered to those contacts  280 . In another example, the sensor could be mechanical, as in activation of a switch at the contact  280  that allows current flow through that specific contact  280  only when a lead  20  touching the contact  280  on the hub. In one example, a contact  280  in the hub may consist of two surfaces that slightly expand when a lead  20  is placed within the contact. The expansion of these surfaces may create an electrical connection that will indicate to the device or signal generator that there is a lead  20  within the contact  280 . In some embodiments, a switch or sensor may be activated when a lead  20  is inserted into an entry port. In some embodiments, a sensor may be employed with regard to each contact  280  of the hub. 
     In some embodiments, a multiplexer (not shown) and demultiplexer (not shown) may be employed to limit the number of conductors that run between the electrical signal generator and the hub. For example, a multiplexer may be employed in the signal generator and a demultiplexer may be employed in the hub. In addition or alternatively, a demultiplexer may be employed in the hub to allow for creation of subchannels such that different contacts  280  corresponding to the same channel may be activated at different times to effectively increase the number of channels. The different contacts  280  may be connected to different electrodes on the same lead  20  or two one or more contacts  280  on multiple other leads  280 . 
     It will be understood that the configuration of internal hub contacts  280  presented in  FIGS. 7-9  are merely an illustration of the configurations that may be employed. It will also be understood that a hub as described herein may be coupled to a signal generator or other electrical device having any number of channels. 
     Referring now to  FIGS. 10A-B , a lead  20  prior to insertion into a hub  200  ( FIG. 10A ) and after insertion into the hub  200  ( FIG. 10B ) is shown. The lead  20  includes a stop mechanism  25  configured to engage the housing  230  of the hub  200  to ensure that the contacts of the lead  20  properly align with internal contact of the hub  200 . The stop mechanism  25  may be a bump or protrusion, bar, plate, or the like. The position of the stop mechanism  25  relative to the distal end of the lead  20  may vary depending on the number of contacts the lead has or are configured to engage internal contacts of the hub  200  (e.g., two or four contacts as depicted in  FIGS. 8-9 ). The stop mechanism  25  may be moveable, e.g. slidable, along the length of the lead  20  or may be permanently fixed to the lead body. Alternatively or in addition, the lead  20  may include a visible marker (not shown) that indicated when the lead is fully and properly inserted into the hub. For example, a marker band may be aligned with the exterior of the hub  200  at a port to indicate that the lead  20  is properly inserted and the contacts of the lead are aligned with the contacts of the hub. A lead  20  may include more than one such marker to allow for insertion into the hub  200  by an amount that couples a desired number of contacts of the lead with a desired number of contacts of the hub. If the lead includes a moveable stop mechanism  25 , the markers may be used to indicate proper positioning of the stop mechanism for fixation relative to the lead. 
     As shown in the embodiments depicted in  FIGS. 8-9 , it may be desirable for the distal regions of the leads to be sufficiently flexible to follow the path of the contacts of the hub (e.g., defined by a bore as depicted in  FIGS. 5-6 ), yet sufficiently rigid to be fully inserted into the hub. Thus, it may be desirable for the angles of the path of the bores in the hub to not be too sharp. 
     The leads  20  may be fixed relative to the hub  200  through any suitable mechanism. For example, the hub  200  may include one or more set screws (not shown) for securing the lead relative to the hub when the lead is inserted into a lead receptacle or bore of the hub. Such set screws are well known for lead extensions and implantable electrical signal generators and may be readily adopted for use with the hubs described herein. Alternatively or in addition, any of a variety of screw-less securing mechanisms that have been developed for used with lead extensions, implantable electrical signal generators, or the like may be readily adopted for use with the hubs described herein. 
     Referring now to  FIGS. 11-12 , alternative embodiments of hubs  200  are depicted. In  FIGS. 11-12 , the hub  200  is generally octagonal. However, it will be understood that the hub may take any suitable shape. It may be desirable of the hub to have rounded corners, if any corners are present, for purposes of patient comfort or for reducing complications, such as skin erosion due to sharp corners or edges, when implanted. Alternatively or in addition, a polymeric coating, covering, boot, sheath, or the like may be placed about the hub to improve patient comfort or to prevent fluid ingress into the hub and its electrical connections. The hub  20  depicted in  FIG. 11  is similar to the hubs depicted in  FIGS. 3-9  in that different lead receptacles may have overlapping or common internal contacts  280 . In the embodiment depicted in  FIG. 12 , each lead receptacle (indicated by dashed lines for two of the receptacles) has discrete contacts, with no overlapping or common contacts between receptacles (or in communication with different lead entry ports  210 ). Of course, in some embodiments, a hub may employ a combination of receptacles having common contacts and receptacles having no contacts in common with other receptacles. 
     In various embodiments, a hub as described herein is rotatable such that a single entry port can be used to deliver more than one lead to the hub. In one example, the top portion of the hub that contains the lead entry port would rotate relative to the base of the hub that contains the rows of electrical contacts that would be connected to the channels of the signal generator. This would result in one entry port that would still allow leads to be inserted into the hub and be aligned with multiple rows of contacts within the hub. 
     A hub, or components thereof, as described herein may be made of any suitable material and according to any suitable process. The hub may, in many respects, be manufactured in a manner similar to a lead extension or implantable signal generator. For example, the hub body form may be made from a metallic material, such as stainless steel or titanium, or polymeric material, such as polycarbonate, polysulfone, polyurethane, silicone or the like. The hub housing could be molded or otherwise formed into halves that could be welded or otherwise joined. Preferably, the hub housing is sealed in a manner sufficient to prevent bodily fluid from entering a seam. 
     It is also desired to prevent bodily fluid from entering a bore or from flowing through a bore to maintain electrical isolation of contacts in the bore of a hub. Wiper seals or other fluid seals that are well known in the art for use with lead extension or implantable electrical signal generators may be employed with the hubs described herein. For example, a wiper seal may be positioned in the bore at or near a port entrance of the hub or between contacts in a bore. 
     Lead receptacles, such as those known for implantable signal generators or lead extensions, with alternating insulating and conductive members may be fitted into bores of the hub. The cable extending from the hub for coupling the hub to an implantable electrical signal generator may include contacts for insertion into a lead receptacle of the signal generator, lead extension, adaptor, or the like. In many respects, techniques and materials employed for forming implantable medical leads may be used to form the cable. 
     Thus, embodiments of HUB FOR IMPLANTABLE MEDICAL LEADS are disclosed. One skilled in the art will appreciate that the present invention can be practiced with embodiments other than those disclosed. The disclosed embodiments are presented for purposes of illustration and not limitation, and the present invention is limited only by the claims that follow.