Patent Publication Number: US-7914343-B2

Title: Implantable bifurcated neurostimulator adapters

Description:
RELATED APPLICATION 
     The present patent application is a divisional application of U.S. patent application Ser. No. 11/678,716, filed Feb. 26, 2007, now U.S. Pat. No. 7,758,384, which is hereby incorporated by reference in its entirety. The present application is related to commonly assignment patent application Ser. No. 11/678,206, filed Feb. 26, 2007, now U.S. Pat. No. 7,594,828, issued Sep. 29, 2009, and is hereby incorporated, by reference, in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure pertains to extending implantable neurostimulator leads and more particularly to adapters for neurostimulator lead extensions. 
     BACKGROUND 
     Implantable neurostimulators can provide electrical stimulation for the treatment of pain and/or various neurological disorders. Neurostimulators typically include one or more stimulation electrodes which may be implanted at specific sites along a spinal cord, a peripheral nerve, or in a brain of a patient; the one or more electrodes are typically mounted to an elongate lead body which carries corresponding conductors for electrical coupling of the electrodes to a neurostimulator device. Because the neurostimulator device is usually implanted in a subcutaneous pocket that is somewhat remote from the stimulation site, often times a lead extension is required to couple a lead connector, which terminates a proximal end of the lead body, to the device. The extension provides an additional length of conductor(s) to reach the device for the electrical coupling of the one or more lead electrodes. One or more connector terminals terminating a proximal end of the lead extension are configured to mate with corresponding connector ports of the device. 
     In recent years, new models of neurostimulator devices have been developed for increased functionality; modifications to the size and/or shape of these newer devices have been made, for example, to accommodate additional components, while keeping a bulk of the devices to a minimum. In many instances, the modifications have been accompanied by changes to the configuration of the connector ports of these devices so that the ports are no longer compatible with connector terminals of lead extensions which were designed to couple with older style devices. Thus, for those patients who either require or desire that an older style device be exchanged for a newer device, there is a need for an adapter to couple the connector terminals of one or more previously implanted lead extensions to one or more ports of the newer device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following drawings are illustrative of particular embodiments of the present disclosure and therefore do not limit the scope of the disclosure. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the present disclosure will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements. 
         FIG. 1A  is schematic plan view of a human body showing various general implant locations for implantable neurostimulator systems. 
         FIG. 1B  is a perspective view of a portion of an exemplary implantable neurostimulator. 
         FIG. 2A  is a perspective view of a neurostimulator adapter and a corresponding neurostimulator device, according to some embodiments of the present disclosure. 
         FIG. 2B  is a plan view including a partial cut-away sections of the adapter shown in  FIG. 2A , according to some embodiments. 
         FIG. 2C  is an end view of the adapter shown in  FIG. 2A , according to some embodiments. 
         FIG. 2D  is a perspective view of a portion of a system including the adapter and device of  FIG. 2A , according to some embodiments of the present disclosure. 
         FIG. 3A  is a plan view of a neurostimulator adapter, according to some alternate embodiments of the present disclosure. 
         FIG. 3B  is a plan view of a portion of a system including the adapter of  FIG. 3A , according to some embodiments of the present disclosure. 
         FIG. 3C  is a perspective view of an adapter, according to some other embodiments of the present disclosure. 
         FIG. 4A  is a plan view of a neurostimulator adapter, according to yet further embodiments of the present disclosure. 
         FIG. 4B  is a plan view of a portion of a system including the adapter of  FIG. 4A , according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the following description provides practical illustrations for implementing exemplary embodiments of the present disclosure. Examples of constructions, materials, dimensions, and manufacturing processes are provided for selected elements, and all other elements employ that which is known to those of skill in the field of the disclosure. Those skilled in the art will recognize that many of the examples provided have suitable alternatives that can be utilized. 
       FIG. 1A  is schematic plan view of a human body showing various general implant locations for implantable neurostimulator systems.  FIG. 1A  illustrates three general types of neurostimulator systems including devices  10  each coupled to an elongate lead  11 . A first of devices  10  is shown implanted in a pectoral region  12 , for example, within a subcutaneous pocket, and corresponding lead  11  extending from device  10  to a site within a brain  2 ; a second of devices  10  is shown implanted in a lower region  13  of the body, and corresponding lead  11  extending from device  10  to a site along a spinal cord  3 ; a subcutaneous pocket in lower region  13  may be formed, in an anterior, abdominal area of the body, or in a posterior, high buttocks area of the body. A third of devices  10  is shown implanted in a subcutaneous pocket form in a thigh region  14  of the body, and a corresponding lead  11  is shown extending from device  10  to a peripheral nerve site in a leg of the body. It should be noted that any of the pockets in regions  12 ,  13 ,  14  may hold a device coupled to a lead extending to any of the peripheral nerves, for example, in either leg, in either arm, or in the neck or head. Although not shown, those skilled in the art will understand that leads  11  each include one or more electrodes in proximity to a distal end thereof. 
     As previously described, a length of each of leads  11  may be extended by a lead extension.  FIG. 1B  is a perspective view of device  10  and an exemplary lead extension  117 .  FIG. 1B  illustrates device  10  including a housing or can  110  and a connector module  120  coupled to can  110  and including two connector ports  102 ; can  110  houses a battery and electronic circuitry necessary to provide electrical stimulation delivered by the electrodes of leads  11 . Those skilled in the art understand that electrical contacts within each of ports  102  are electrically coupled, via hermetically sealed feedthroughs, to the electrical circuitry housed within can  110 .  FIG. 1B  further illustrates lead extension  117  including an elongate body  171 , to which a plug  172  is coupled at a proximal end, and to which a connector port  174  is coupled at a distal end. A pair of connector terminals  175  is shown extending proximally from plug  172 ; each of connector terminals  175  includes a terminal pin contact  176  and a contact surface  177 , which is spaced apart from pin contact  176  along a length of the corresponding connector terminal  175 . 
     According to the illustrated embodiment, ports  102  of device connector module  120  are positioned to receive, for electrical and mechanical coupling, the pair of side-by-side connector terminals  175 , and, extension connector port  174  is adapted to receive, for electrical and mechanical coupling, a lead connector, for example, an in-line connector, such as is known to those skilled in the art, which terminates a proximal end of the lead and includes a plurality of spaced apart contacts. Those skilled in the art will appreciate that extension port  174  includes a plurality of electrical contacts, which couple with the contacts of the lead connector, when the connector is fully inserted in port  174 , and which are each coupled either to a corresponding terminal pin contact  176  or to a corresponding contact surface  177  of connector terminals  175 , via a corresponding elongate conductor extending within elongate body  171 . Thus, when connector terminals  175  are fully inserted into device ports  102 , and the lead connector is fully inserted into extension portion  174 , electrical stimulation therapy may be delivered from device  10  to the one or more electrodes of lead  11 , either implanted in brain  2 , or along spinal cord  3 , or along a peripheral nerve ( FIG. 1A ). 
       FIG. 2A  is a perspective view of a neurostimulator adapter  200  and a corresponding neurostimulator device  20 , according to some embodiments of the present disclosure.  FIG. 2A  illustrates device  20 , like device  10  ( FIG. 1B ), including a housing or can  210  and a connector module  220 , however connector module  220  includes ports  202  which differ in individual size and configuration from ports  102  of device  10 . According to embodiments of the present disclosure, when device  10  ( FIG. 1B ) is changed out for device  20 , an adapter, for example, adapter  200 , is necessary to provide a compatible coupling between one of ports  202  of device  20  and the previously implanted extension  117 . 
     With reference to  FIG. 2A , adapter  200  includes an elongate body  240  to which a connector  230 , which is compatible with each of ports  202  of device  20 , is coupled; connector  230  is shown including eight contacts  231 , so it should be appreciated that each of ports  202  include a corresponding set of eight device contacts for electrical coupling with contacts  231 , when connector  230  is fully inserted therein.  FIG. 2A  illustrates adapter  200  including a flexible bifurcation member  27  coupled to a distal end of body  240 ; bifurcation member  27  includes a first branch  271 , to which a first housing  281  is coupled, a second branch  272 , to which a second housing  282  is coupled, and a bending joint  275  located between first and second branches  271 ,  272 .  FIG. 2A  further illustrates each housing  281 ,  282  including a first sidewall  251 , a second sidewall  252 , opposite first sidewall  251 , a first face  261  extending between first and second sidewalls  251 ,  252 , a second face  262 , opposite first face  261  and extending between first and second sidewalls  251 ,  252 , a third face  263  extending between first and second sidewalls  251 ,  252  and between first and second faces  261 ,  262 , a fourth face  264 , opposite third face  263  and extending between first and second sidewalls  251 ,  252  and between first and second faces  261 ,  262 , a first port  21  and a second port  22 . 
       FIG. 2B  is a plan view including partial cut-away sections of adapter  200 , according to some embodiments.  FIG. 2B  illustrates ports  21 ,  22  of housing  281  each including a spring-type housing contact  212 ,  222 , for example, a multi-beam contact, which may be formed from stainless steel, MP35N alloy, titanium or any other suitable material known to those skilled in the art, and a set screw-type housing contact, which may likewise be formed from stainless steel, MP35N alloy, titanium or any other suitable material known to those skilled in the art, and which includes a set screw  211 ,  221  mounted in a set screw block.  FIG. 2B  further illustrates a shaft of first port set screw  211  extending approximately parallel with first face  261 , while a shaft of second port set screw  221  extends at an angle X, for example, greater than 0 degrees and less than 90 degrees, with respect to first face  261 . An access port  216  for set screw  211  is shown located on third face  263 , and an access port  226  for set screw  221  is shown located on second face  262 . Those skilled in the art will understand that access ports  216 ,  226  provide access for a set screw wrench, to engage screws  211 ,  221 , respectively, yet are sealed to prevent ingress of bodily fluids when adaptor  200  is implanted; any suitable type of grommet known to those skilled in the art and through which a set screw wrench may pierce, may be employed by embodiments of the present disclosure. With reference to  FIG. 2B , in conjunction with  FIG. 1B , it should be appreciated that when each connector terminal  175  of extension plug  172  is fully inserted into a corresponding port  21 ,  22 , each contact surface  177  mates with a corresponding spring contact  212 ,  222  and each terminal pin contact  176  is positioned to mate with a corresponding set screw  211 ,  221 . Although not labeled in  FIG. 2B , those skilled in the art will recognize a set of sealing rings shown in each of ports  21 ,  22 . The illustrated sealing rings are intended to provide electrical isolation between each pin contact  176  and corresponding contact surface  177  of fully inserted terminals  175 , but are not necessary elements for every embodiment of the present disclosure. It should be noted that, according to preferred embodiments, ports  21 ,  22  of housing  282  include the housing contacts described above and are configured like ports  21 ,  22  of housing  281 . Furthermore, it should be noted that the scope of the present disclosure is not limited to the illustrated types of contacts and alternate embodiments of the present disclosure may include any other types of contacts known to those skilled in the art. 
     According to the illustrated embodiment: first and second ports  21 ,  22  of each housing  281 ,  282  have openings located on first face  261  thereof, in order to receive insertion of side-by-side connector terminals  175  of extension  117  ( FIG. 1B ); first and second sidewalls  251 ,  252  each include a relatively flat outer surface extending alongside each of ports  21 ,  22 ; and second face  262  extends at an angle Y, for example, greater than 0 degrees and less than 90 degrees, with respect to first face  261 . It may be appreciated that the angled arrangement of set screws  221 , in combination with the angling of second faces  262 , contributes to a reduction in a bulk of each of housings  281 ,  282  from a bulk that would have resulted if set screws  221  had been oriented in a traditional manner, for example, like set screws  211 , such that their shafts extended parallel to first faces  261 . Such a traditional arrangement of set screws  221  would have forced an increased footprint of each of housings  281 ,  282 , for example, along second faces  242  (to provide appropriately oriented access ports for the set screw along second faces  262 ), or would have forced an increased thickness of each of housings  281 ,  282 , between sidewalls  251 ,  252  (to provide appropriately oriented access ports along one or both of sidewalls  251 ,  252 ). 
       FIG. 2B  illustrates a group of eight conductors  280 , for example, individually insulated cable conductors, that extend within body  240  from connector  230  to bifurcation member  27 . A first subgroup  280 A of four conductors from group  280  is shown extending through first leg  271  of bifurcation member  27  and into first housing  281  in order to couple each of a first four of contacts  231  of connector  230  to the corresponding housing contact within one of ports  21 ,  22  of housing  281 , and, although not shown, it will be appreciated that a second group of four conductors from group  280  extends through second leg  272  of member  27  and into second housing  282  in order to couple a second four of connector contacts  231  to the corresponding housing contacts within one of ports  21 ,  22  of housing  282 . Conductors  280  may extend within body  240  in either a straight or coiled configuration, and body  240  may include either a single or multi-lumen tube, for example, formed, by an extrusion and/or molding process, from medical grade silicone, or polyurethane, or a combination thereof. Likewise, bifurcation member  27  may be formed, by an extrusion and/or molding process, from silicone, polyurethane, or a combination thereof. Conductors  280  are preferably formed from an MP35N alloy, which is known to those skilled in the art; and each of conductors  280  is coupled to a corresponding connector contact  231  by means known to those skilled in the art, for example, crimping and/or welding; and each of conductors  280  is preferably individually insulated by an insulative jacket, for example, formed from a fluoropolymer or a polyimide.  FIG. 2B  further illustrates conductor paths (not labeled) extending within housing  281  from each of spring-type housing contacts  211 ,  212  and the set screw-type housing contacts toward first leg  271  of bifurcation member  27 , and, it should be understood that, similar paths extend within housing  282 , according to preferred embodiments. Those skilled in the art will appreciate that conductors  280  may be electrically coupled to the housing contacts in a number of ways; for example, each conductor of each of the first and second subgroups may be routed into the respective housing  281 ,  282  along a corresponding conductor path for direct coupling with the corresponding contact, for example, via welding, or, a separate conductor may extend from each contact, along the corresponding conductor path to a corresponding coupling plate located in proximity to second face  262  for coupling to the corresponding conductor of group  280 , for example, via welding. Those skilled in the art will further appreciate that appropriate electrical isolation may be provided for each conductor within housings  281 ,  282 , either via an insulative jacket formed about each conductor, or via insulative walls formed within housings  281 ,  282  between each conductor, or via a combination thereof. 
       FIGS. 2A-B  further illustrate each of housings  281 ,  282  including an optional hole  29 , which extends through each housing  281 ,  282  from first sidewall  251  to second sidewall  252 , and which is located in proximity to an intersection of second housing face  262  and third housing face  263 . Hole  29  may be used to facilitate securing, for example, via a suture, of adapter housings  281 ,  282  to tissue within an implant pocket, either alongside device  20  or separate from device  20 . 
     According to an exemplary embodiment of the present disclosure, each of housings  281 ,  282  is formed from medical grade silicone, preferably having a durometer of approximately 65 D. With reference to  FIG. 2B , a reinforcing tubing or liner  290  that extends within hole  29  may be desirable, particularly when housing  24  is formed from a relatively soft material that requires a harder interface, for example, for a suture to bear against; examples of appropriate materials for liner  290  include, without limitation, polysulfone and a relatively hard durometer of polyurethane, for example, 75 D. Each of housings  281 ,  282  may be molded and the illustrated components assembled therein according to any suitable method known to those skilled in the art. According to an exemplary assembly method, a portion of each of housings  281 ,  282  is molded with openings into which the components are inserted; conductors may be coupled to each of the housing contact components either before or after insertion into the corresponding opening of the corresponding housing. After the conductors are routed along the conductor paths, voids over and around each opening are filled in, either by a secondary molding process or manual injection of filler material, for example, medical grade silicone. 
       FIG. 2C  is an end view of adapter  200 , according to some embodiments; and  FIGS. 2A-C  illustrate flexible bifurcation member  27  of adaptor  200  in a relaxed state, or un-deformed, such that fourth face  264  of housing  281  faces in a generally opposite direction to that in which fourth face  264  of housing  282  faces. A deformation of bifurcation member  27 , for example, by folding one of first and second housings  281 ,  282  over, per arrow A 1  or A 2  ( FIG. 2C ), will allow for an alternate alignment of housings  281 ,  282 , for example as is illustrated in  FIG. 2D . According to the illustrated embodiment, bending joint  275  of bifurcation member  27  allows first and second housings  281 ,  282  to be moved from the configuration shown in  FIGS. 2A-C  to the configuration shown in  FIG. 2D , such that first sidewall  251  of housing  281  is adjacent to, and faces, second sidewall  252  of second housing  282 , and first ports  21  of first and second housings  281 ,  282  are beside one another and second ports  22  of first and second housings  281 ,  282  are beside one another. Bending joint  275  may be formed in bifurcation member  27 , for example, by a soft section or by a thinned section, like a crease, which is shown in the embodiment of  FIGS. 2A-C . With reference to  FIG. 2D , it will be appreciated that hole  29  of first housing  281  is aligned with hole  29  of second housing  282 , when flexible bifurcation joint  275  is deformed to bring first sidewall  251  of housing  281  alongside second sidewall  252  of housing  282 ; thus, a securing member passed through holes  29  of first and second housings  281 ,  282  can, in addition to securing each housing  281 ,  282  to subcutaneous tissue, secure housings  281 ,  282  in close proximity with one another. 
       FIG. 2D  further illustrates two extensions  117  ( FIG. 1B ) plugged into adapter  200 , which couples extensions  117  to device  20 , via insertion of adapter connector  230  into one of device ports  202  ( FIG. 2A ). Although adapter  200  is illustrated in  FIG. 2D  with housings  281 ,  282  folded together, it should be appreciated that adapter  200  may couple extensions  117  to device  20  and be implanted without housings  181 ,  182  being folded together. Furthermore, it should be noted that, although device  20  has been illustrated having two connector ports  202 , device need only have one of these ports  202 . 
     According to some exemplary implant methods, extensions  117  are plugged into adapter  200 , either before or after adapter  200  is plugged into device  20 , and either before or after housings  281 ,  282  have been folded toward one another, then device  20  may be rotated around, per arrow W, and shifted alongside adapter  200  and extension plugs  172  such that elongate body  240  of adapter  200  wraps approximately around a perimeter of device  20 . A length of elongate body  240  and bifurcation member  27 , together, may be between approximately 10 centimeters and approximately 20 centimeters to accommodate such an implanted configuration. An implanter may desire to secure, for example, with a suture through holes  29 , adapter housings  281 ,  282  to subcutaneous tissue within an implant pocket alongside device  20  such that housings  281 ,  282  will remain either beside or behind device  20  in the pocket, rather than between device  20  and the skin of the body. Such an arrangement is preferred if a battery of device  20  has the capacity to be re-charged transcutaneously, and for added protection of adapter  200  and extensions  117  from nicks and cuts, if, and when an explant of device  20  is required, at a later date. 
     According to alternate implant methods, adapter  200  may be implanted in a first subcutaneous pocket and device  20  in a second subcutaneous pocket; for example, the first pocket may be one previously formed for a device which has been explanted to be exchanged for device  20 , and the second pocket, a new pocket formed for device  20 . With reference back to  FIG. 1A , the first pocket may be in pectoral region  12  and the second pocket in lower region  13  or thigh region  14 . For such an implant configuration in which there is a relatively significant distance between the two pockets, a length of body  240  and bifurcation member  27 , together, is preferably greater than approximately 40 centimeters, upwards to approximately 110 centimeters. 
       FIG. 3A  is a plan view of a neurostimulator adapter  300 , according to some alternate embodiments of the present disclosure.  FIG. 3A  illustrates adapter  300  including, like adapter  200 , connector  230  coupled to a proximal end of elongate body  240 , and each of first and second housings  281 ,  282  coupled to a corresponding branch  271 ,  272  of a flexible bifurcation member  27 ′, which is coupled to a distal end of elongate body  240 . In contrast to adapter  200 , bifurcation member  27 ′ of adapter  300  need not include a bending joint, like joint  275  ( FIGS. 2A-C ), since branches  271 ,  272  of adapter  300  are of a length and flexibility to allow for movement of housings  281 ,  282 , for example, per one or both of arrows B 1 , B 2 , into a side-by-side configuration as illustrated in  FIG. 3B .  FIG. 3B  is a plan view of a portion of a system including adapter  300 , according to some embodiments, and illustrates adapter  300  coupling at least one extension  117  to device  20  in a similar manner to that described for adapter  200  in conjunction with  FIG. 2D . In further contrast to adapter  200 , housings  281 ,  282  of adapter  300  are shown oriented such that fourth face  264  of each faces in a same general direction, when bifurcation member  27 ′ is not deformed ( FIG. 3A ), for example, by bending and/or twisting of one or both branches  271 ,  272 , as well as when branches  271 ,  272  are bent to allow housings  281 ,  282  to come together ( FIG. 3B ). With reference to  FIG. 3B , it should be appreciated that hole  29  of each housing  281 ,  282  may be aligned in order to secure housings  281 ,  282 , together, to subcutaneous tissue, for example, in a manner previously described for adapter  200 .  FIGS. 3A-B  further illustrate each leg  271 ,  272  including an optional groove  379  formed therein in proximity to the corresponding housing  281 ,  282 ; groove  379  may further facilitate securing of housings  281 ,  282  by providing a reinforced zone in each branch  271 ,  272  about which a suture may be tied. Exemplary implant methods for the system shown in  FIG. 3B  are similar to those previously described for the system described in conjunction with  FIG. 2D . 
       FIG. 3A  further illustrates a plane  35 , in which branches  271 ,  272  of bifurcation member  27 ′ extend; according to the illustrated embodiment, first and second sidewalls  251 ,  252  of each housing  281 ,  282  extend approximately parallel to plane  35  when bifurcation member  27 ′ is un-deformed. According to an alternate embodiment, for example, adapter  300 ′ shown in  FIG. 3C , housings  281 ,  282  are oriented such that sidewalls  251 ,  252  extend approximately parallel to a plane  37 , which extends at an angle Z with respect to plane  35 , when bifurcation member  27 ′ is un-deformed. Angle Z is preferably approximately 90 degrees, but may be any angle greater than 0 degrees. 
       FIG. 4A  is a plan view of a neurostimulator adapter  400 , according to yet further embodiments of the present disclosure.  FIG. 4A  illustrates adapter  400  including, like adapter  300 , connector  230  coupled to a proximal end of elongate body  240 , and each of first and second housings  281 ,  282  coupled to a corresponding branch  271 ,  272  of a flexible bifurcation member  27 ″, which is coupled to a distal end of elongate body  240 . Like bifurcation member  27 ′ of adapter  300 , member  27 ″ of adapter  400  does not include a bending joint, like joint  275  ( FIGS. 2A-C ), but, unlike member  27 ′ of adapter  300 , a length of branch  271  is greater than that of branch  272  such that housing  281  is offset from housing  282 , in both directions D 1  and D 2  along plane  35 , when bifurcation member  27 ″ is un-deformed. It should be noted that, according to alternate embodiments, a length of branch  271  is less than a length of branch  272  so that housing  281  is offset from housing  282  in a direction opposite to D 1 .  FIG. 4B  is a plan view of a portion of a system including adapter  400 , according to some embodiments, and illustrates adapter  400  coupling extensions  117  to device  20 . Exemplary implant methods for the system shown in  FIG. 4B  are similar to those for the system described in conjunction with  FIG. 2D . However, in contrast to adapters  200 ,  300  and  300 ′, where, according to preferred embodiments, housings  281 ,  282  are allowed to come together, such that second sidewall  252  of first housing  281  is alongside first sidewall  251  of second housing  282 , the differing lengths of branches  271  and  272  in bifurcation member  27 ″ of adapter  400  can help to prevent such a coming together of housings  281 ,  282 . Thus, adapter  400  provides an option encouraging a minimal thickness in adapting extensions  117  to device  20 , the minimal thickness being approximately equal to or only slightly greater than that defined between first and second sidewalls  251 ,  252  of each of housings  281 ,  282 . Of course, it should be appreciated that any of adapters  200 ,  300  and  300 ′ may be implanted in such a slimmer configuration, if desired. The thicker configuration of adapters  200 ,  300  and  300 ′ as shown in  FIGS. 2D ,  3 B, and  3 C, respectively, may be particularly preferred for those situations when an new pocket is created for device  20  and it is desirable for the adapter to fit snugly in the old pocket from which the old device has been explanted. The slimmer configuration of any of the adapters may be preferred if both device  20  and the adapter need to fit together within a newly created pocket. 
       FIG. 4B  further illustrates the system including optional sleeves  40 , for example, formed, by an extrusion or molding process, from medical grade silicone, extending around each of extension plugs  172  and the corresponding housing  281 ,  282  to bridge a junction therebetween. Sleeves  40  may provide for additional sealing and/or retention at an interface of the junction between each plug  172  and the corresponding housing  281 ,  282 . An optional groove  45  shown extending about an outer surface of sleeves  40  may provide an interface for a securing element, for example a suture; sleeve  40  may include more than one of groove  45 . Sleeves  40  may be pre-assembled onto housings  281 ,  282  or onto extension plugs  172 , and may be initially slid back or rolled back thereon during insertion of plugs  172  into housings  281 ,  282 . With reference back to  FIG. 3B , a similar optional sleeve  30  is shown with dashed lines; optional sleeve  30  is sized to fit around both housings  281 ,  282  and the corresponding plugs  172  coupled thereto. 
     In the foregoing detailed description, the invention has been described with reference to specific embodiments. However, it may be appreciated that various modifications and changes can be made without departing from the scope of the invention as set forth in the appended claims.