Abstract:
A surgical tool is used to facilitate the implantation of elements of an electrical stimulation system within a human body, and more particularly facilitates surgical procedures followed to connect an electrode lead extension between an Implantable Pulse Generator (IPG) and an electrode lead, when the IPG and the electrode lead may not be co-located. In one exemplary embodiment, a removable carrier cover defines an end tunneler portion to facilitate tunneling and a carrier is provided for receiving and holding a portion of a lead, such as a lead connector. Once the tunnel is formed, the removable carrier cover is removed to expose the carrier. The carrier is adapted to carry one or more leads back through the tunnel. In some embodiments of the invention, the tool provides rotational locking and unlocking of the handle relative to the carrier and/or tunneling means.

Description:
The present application is a Continuation-in-Part of U.S. patent application Ser. No. 09/702,422, filed Oct. 31, 2000, now issued as U.S. Pat. No. 6,605,094, which application is a non-provisional of U.S. Provisional Patent Application Ser. No. 60/166,560, filed Nov. 19, 1999. Both of these applications and patent are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to implantable medical devices and more particularly to a tool for use in surgically implanting such devices. A common role for such an implantable device is nerve or muscle stimulation and more particularly Spinal Cord Stimulation (SCS). SCS systems typically include an implantable pulse generator (IPG), which is a source of stimulation current, and an implantable electrode array (a.k.a., lead, electrode lead), which provides the stimulation current to the nerves to be stimulated. In many cases where such devices are utilized, the electrode array is remote from the location of the IPG. In such cases, an electrode lead extension may be used to electrically connect the IPG to the electrode array. For example, in the case of SCS, the electrodes providing the stimulation current to the nerves must be positioned adjacent to the spinal cord, but sufficient space is not available for the IPG in the area adjacent to the electrodes. In this example, the IPG must be located remotely from the electrode array. Thus, a tool(s) may be used to create a subcutaneous tunnel from the location of the electrode lead to the location of the IPG, and to carry the electrode lead extension back through the tunnel to the electrode lead. 
     Existing subcutaneous tunneling and carrying tools require a separate tunneling tip and carrying tip. After the tunnel is created using the tunneling tip, the tunneling tip must be removed and the carrying tip attached. The common method of attachment is a threaded adapter on the end of a shaft. This approach requires that the tunneling tip be removed by unscrewing and the carrying tip be attached similarly. The requirement to unscrew one tip and screw on another tip adds to the complexity of the surgical procedure. If the threads are damaged in the process of installing the carrier, a new tunneling tool and/or carrier must be used. The need to keep surgical procedures as simple and error-free as possible dictates that a more robust approach be found. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the above and other needs by providing an integrated subcutaneous tunneling and carrying tool that eliminates the need to unscrew a tunneling tip and screw on a separate carrying tip. The tools provided by the present invention create a tunnel through body tissue, and then carry an electrode lead extension (or the proximal end of a lead) through the tunnel for connection to the electrode lead, without requiring the manipulation of threaded tips. The electrode lead extension includes a female lead extension connector which connects with a male connector on the end of the electrode lead. Tools according to the present invention include: a cavity that a portion of a lead, such as the lead extension connector, and possibly some of the lead body, is inserted into, allowing the lead to be pulled through the tunnel; a first male connector similar to the connector on the electrode lead, wherein the female lead extension connector may be, connected to the first male connector, and the lead pulled through the tunnel; and/or a second male connector, to which a carrier may be attached, which carrier may hold a portion of the lead while the lead (e.g., lead extension) is pulled through the tunnel. These and other embodiments of the present invention are presented herein. 
     In a first embodiment of the integrated subcutaneous tunneling and carrying tool, a carrier is employed that serves both the function of tunneling and carrying. After the tool has completed the tunneling process, a cover that is part of the carrier is opened by a simple pull and twist action, and the lead extension connector is inserted into the carrier. Then, the tool is pulled back through the tunnel, carrying the lead extension connector and attached lead extension. 
     In a second embodiment, the integrated subcutaneous tunneling and carrying tool includes a mating connector designed to connect with the lead extension connector. The mating connector is the same basic shape as the male connector on the electrode lead to which the lead extension connector attaches, and also has a tip suitable for tunneling. After creating the tunnel and connecting the lead extension connector, the tool is pulled back through the tunnel, pulling the lead extension with it. In this embodiment, the section of the tool adjacent to the mating connector may be enlarged to provide additional clearance for pulling the lead extension connector and lead extension through the tunnel. 
     In a third embodiment, the lead extension connector of the electrode lead extension is packaged in a detachable carrier. The detachable carrier includes a receptacle with an attaching mechanism. The integrated subcutaneous tunneling and carrying tool includes a mating connector designed to both tunnel and to engage the attaching mechanism of the detachable carrier. After the tunneling tool is pushed through the tissue, the carrier is attached to the mating connector and then pulled back through the tunnel. After the lead extension is pulled through the tunnel, the detachable carrier is discarded. 
     In a fourth embodiment, the tool includes a carrier permanently attached to the tool. The carrier comprises a carrier body and a removable carrier cover, which carrier cover has an end for tunneling. After the tunnel has been made, the cover is removed and discarded. The lead extension connector is inserted into a cavity in the carrier body, and the electrode lead extension is pulled back through the tunnel. 
     In a fifth embodiment, the subcutaneous tunneling and carrying tool includes a handle, a rod, a carrier, and a removable carrier cover. The removable carrier cover defines a nose to facilitate tunneling. Once the tunnel is formed, the removable carrier cover is removed to expose the carrier. The carrier is adapted to carry two or more leads back through the tunnel. The handle is removably attachable to the rod by a coupler. 
     In a sixth embodiment, the tool includes a tunneling end and a tunneler rod, which rod fits into a tool straw. After tunneling, the tool rod is removed from the straw so the lead may be passed through the straw. 
     In a seventh embodiment, the subcutaneous tunneling and carrying tool is similar to the tool of the fifth embodiment, wherein the coupler of the seventh embodiment functions like the coupler of the fifth embodiment, but is constructed differently. 
     It is thus a feature of the present invention to provide several embodiments of a simple-to-use tool, which provides a tunneling capability, and a carrying capability, without difficult manipulation of tool components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects 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  depicts a typical Spinal Cord Stimulation (SCS) system implant location with an electrode adjacent to the spinal cord, and an implantable pulse generator (IPG) beneath the rib cage; 
         FIG. 1B  depicts another typical implant location of an SCS system with the IPG implanted above the buttock; 
         FIG. 1C  shows a more detailed view of SCS system components; 
         FIG. 2  depicts a first embodiment of the tunneling and carrying tool with the carrier cover in an open position and carrier cavity exposed, and a lead extension connector suitable for carrying in the carrier cavity; 
         FIG. 3  shows details of the first embodiment of a carrier of the first embodiment of the tool with the carrier cover in the open position; 
         FIG. 3A  shows a cross section of the carrier shown in  FIG. 3 , taken along line  3 A- 3 A of  FIG. 3 , and illustrates the cover locking feature; 
         FIG. 3B  shows a second cross section of the carrier shown in  FIG. 3 , taken along line  3 B- 3 B of  FIG. 3 ; 
         FIG. 4  depicts the details of a second embodiment of the carrier of the first tool embodiment; 
         FIG. 4A  shows a cross section of the carrier shown in  FIG. 4 , taken along line  4 A- 4 A of  FIG. 4 , and illustrates a second method for providing a cover lock; 
         FIG. 4B  shows a second cross section of the carrier shown in  FIG. 4 , taken along line  4 B- 4 B of  FIG. 4 ; 
         FIG. 5  depicts the details of the second embodiment of the carrier of the first tool embodiment with the carrier cover pulled forward to allow the cover to be rotated between the open and the closed positions; 
         FIG. 5A  shows a cross section of the carrier shown in  FIG. 5 , taken along line  5 A- 5 A of  FIG. 5 , and further illustrates the second method for providing a cover lock wherein the cover lock is disengaged; 
         FIG. 5B  shows a second cross section of the carrier shown in  FIG. 5  taken along line  5 B- 5 B of  FIG. 5 ; 
         FIG. 6  depicts a second embodiment of the tunneling and carrying tool utilizing a mating connector which engages the lead extension connector and an enlarged section to expand the tunnel for easier passage of the electrode lead extension; 
         FIG. 7  depicts a third embodiment of the tunneling and carrying tool, which includes a second mating connector and a detachable carrier; 
         FIG. 8  shows details of the detachable carrier of the third embodiment; 
         FIG. 8A  shows a cross section of the carrier shown in  FIG. 8  taken along the lines  8 A- 8 A of  FIG. 8 ; 
         FIG. 9  depicts a variation of the third embodiment with a break apart carrier; 
         FIG. 9A  shows a cross sectional view of the embodiment in  FIG. 9 , taken along line  9 A- 9 A of  FIG. 9 , and illustrates a mating connector and cooperating connector port which provide a pivotal connection; 
         FIG. 10  depicts a fourth embodiment of the tunneling and carrying tool utilizing a removable carrier cover, with the carrier cover in place; 
         FIG. 10A  shows the fourth embodiment of the tool with the carrier cover removed, and an electrode lead connector inserted into a carrier cavity of the carrier; 
         FIG. 11  shows a more detailed view of the carrier body and carrier cover of the fourth embodiment; 
         FIG. 12  depicts a fifth embodiment of the tunneling and carrying tool utilizing a removable carrier cover, with the carrier cover in place; 
         FIG. 12A  shows the fifth embodiment of the tool with the carrier cover and handle removed; 
         FIG. 13  shows details of the carrier and carrier cover of the fifth embodiment; 
         FIG. 14  shows the handle, handle shaft, and coupler of the fifth embodiment; 
         FIG. 14A  depicts a cross-sectional view taken along line  14 A- 14 A of  FIG. 14 , with the handle shaft attached to the coupler; 
         FIG. 14B  shows an isometric view of the handle and handle shaft of the fifth embodiment; 
         FIG. 15  shows the coupler and rod handle end of the rod of the fifth embodiment; 
         FIG. 15A  depicts a cross-sectional view taken along line  15 A- 15 A of  FIG. 15 , with the rod handle end attached to the coupler; 
         FIG. 15B  shows an isometric view of the rod handle end of the fifth embodiment; 
         FIG. 15C  depicts the cooperation of the coupler, the handle shaft, and the rod handle end; 
         FIG. 16A  shows a top view of the rod of the fifth embodiment; 
         FIG. 16B  shows a side view of the rod of the fifth embodiment; 
         FIG. 16C  shown an isometric view of the rod carrier end of the rod of the fifth embodiment; 
         FIG. 17  depicts details of the rod carrier end and of the carrier of the fifth embodiment; 
         FIG. 17A  shows a cross-sectional view of the carrier taken along line  17 A- 17 A of  FIG. 17 ; 
         FIG. 18A  is a cross-sectional view of the carrier taken along line  17 B- 17 B of  FIG. 17 ; 
         FIG. 18B  is a cross-sectional view of the rod carrier end inserted into the carrier of the fifth embodiment in a rotationally locked position; 
         FIG. 18C  is a cross-sectional view of the rod carrier end inserted into the carrier of the fifth embodiment in a rotationally unlocked position; 
         FIG. 19  shows a sixth embodiment of a tool of the present invention, adapted to cooperate with the handle of the fifth embodiment; 
         FIG. 20  shows a straw adapted to cooperate with the tunneler of the sixth embodiment; 
         FIG. 21  depicts the tunneler of the sixth embodiment in the straw; 
         FIG. 22A  shows a top view of an extension for the tool rod of the sixth embodiment; 
         FIG. 22B  shows a side view of the extension of  FIG. 22A ; 
         FIG. 22C  shows the extension of  FIGS. 22A and 22B  attached to the coupler of the sixth embodiment; 
         FIG. 23A  illustrates a seventh embodiment of a tunneling and carrying tool according to the present invention; 
         FIG. 23B  shows additional details of the tool of  FIG. 23A ; 
         FIG. 24A  shows details of a handle assembly of the tool of  FIG. 23A ; 
         FIG. 24B  is a view of the handle assembly of  FIG. 24A , with the coupler cover detached from the coupler; 
         FIG. 25  is an isometric view of a handle shaft of the handle assembly of  FIG. 24A ; 
         FIG. 25A  is a side view of the handle shaft of  FIG. 25 ; 
         FIG. 26  shows a rod of the tool of  FIG. 23A ; 
         FIG. 26A  is a detailed side view of the rod shown in  FIG. 26 ; 
         FIG. 27  is an isometric view of a coupler of the tool of  FIG. 23A , shown without a coupler cover; 
         FIG. 27A  is a side view of the coupler of  FIG. 27 ; 
         FIG. 28  is a top view of the coupler of  FIG. 27 ; 
         FIG. 28A  a cross-sectional view of the coupler of  FIG. 27 , taken along line  28 A- 28 A of  FIG. 28 ; 
         FIG. 29  is an isometric view of an upside-down coupler cover for the coupler of  FIG. 27 ; 
         FIG. 30  is an end view of the coupler cover of  FIG. 29 ; and 
         FIG. 30A  is a cross-sectional view of the coupler cover of  FIG. 29 , taken along line  30 A- 30 A of  FIG. 30 . 
     
    
    
     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. 
     Typical implants of a Spinal Cord Stimulation (SCS) system in a patient  4  are shown in  FIG. 1A  and in  FIG. 1B . The SCS system is comprised of at least one electrode  6 , an electrode lead extension  34 , and an Implantable Pulse Generator (IPG)  8 . The electrode  6  is part of an electrode lead  7 , and the electrode lead extension  34  includes a lead extension connector  40 . Generally, the electrode  6  and IPG  8  cannot be co-located because electrode  6  must be located at the stimulation site, but space is not always available for IPG  8  adjacent to the stimulation site. Typical locations for IPG  8  include beneath the rib cage, as shown in  FIG. 1A , and above the buttock, as shown in  FIG. 1B . In such cases, a tool is typically used to create a subcutaneous tunnel through the body tissue from the site of the electrode lead  7  spinal column exit to the IPG  8 . Once the tunnel has been created, the lead extension connector  40  and attached electrode lead extension  34  are carried back through the tunnel and removably attached (e.g., plugged into) the electrode lead  7 . It is also possible to use a tool of the present invention to carry the proximal end of a lead  7  to the IPG site. The present invention is described herein mainly in connection with lead extension  34 , however, when reference is made herein to carrying a lead or lead extension, what is intended is any lead, lead extension, or lead-like body. The present invention is further described mainly in terms of having a carrier(s) for carrying a lead connector, however, the carrier(s) may carry any portion of a lead. For example, a carrier may carry a connector and part of the lead body. 
     As seen in  FIG. 1C , and as is evident from  FIGS. 1A and 1B , the SCS system  2  includes three main components: electrode  6  on lead  7 , electrode lead extension  34 , and IPG  8 . IPG  8  produces electrical current. Electrode lead extension  34  is connected between IPG  8  and electrode  6 , and carries the electrical current to the electrode  6 . Electrode  6  delivers the electrical current to the nerve or other tissue. Electrode lead  7  has an end that is permanently connected to electrode  6 , and has another end with a connector that exits the spinal column. Lead extension connector  40  removably connects electrode lead extension  34  to electrode lead  7  and extends from electrode lead  7  to IPG  8 . 
     The present invention relates to an integrated subcutaneous tunneling and carrying tool. First, the tool is used to create a subcutaneous tunnel—either from the IPG  8  implant location to the site where the electrode lead  7  exits the spinal column, or vice versa. Then the tool is used to carry the electrode lead extension  34 , which can be detachably connected to the electrode lead  7 , through the tunnel. One embodiment of such a tool  9  is shown in  FIG. 2  and comprises a handle  10 , a rod  12 , and a carrier  14 . Carrier  14  has an end that is used to create the tunnel from electrode lead  7  to IPG  8 , and a carrier cavity  28  to carry the lead extension connector  40  and attached electrode lead extension  34  back through the tunnel. Thus, in this embodiment of the tool, carrier  14  is used for both tunneling and carrying. 
     As shown in more detail in  FIG. 3 , the first embodiment of carrier  14  of tool  9  includes a carrier tunneling end  17  for tunneling, the carrier cavity  28  into which lead extension connector  40  is inserted for carrying through the tunnel, and an optional lead guide  24  in which a portion of electrode lead extension  34  is removably positioned to help retain lead extension connector  40  and attached electrode lead extension  34  while they are carried through the tunnel. 
       FIG. 3A  shows a sectional view of carrier  14  taken along line  3 A- 3 A of  FIG. 3 . The carrier cover  16  is shown as surrounding the carrier body  15 . Carrier cover  16  is rotatably attached to carrier  14  and has two locking positions. In the position shown in  FIG. 3 , the cover is in the open position and is aligned with the carrier cavity  28 , allowing lead extension connector  40  to be removably inserted into carrier cavity  28 . To perform the tunneling process, carrier cover  16  is rotated 180 degrees into the closed position where it covers carrier cavity  28  to prevent body tissue from entering carrier cavity  28 , or snagging carrier cavity  28 . Carrier cover  16  also includes carrier tunneling end  17  shaped to facilitate use of carrier  14  for tunneling. When the tunneling procedure has been completed, carrier cover  16  is pulled toward the carrier tunneling end  17  and rotated to expose carrier cavity  28 . 
     The carrier cover  16  locking mechanism is also shown in the sectional view of  FIG. 3A . The locking mechanism comprises a spring  25  pushing a locking ball  22  cooperating with either of two ball receptacles  26 A,  26 B in the carrier cover  16  to lock the carrier cover  16  into an open or closed position. When twisting torque is applied to carrier cover  16 , the locking ball  22  pushes against spring  25 , thus permitting the carrier cover to the rotated. When the locking ball  22  is aligned with either ball receptacle  26 A,  26 B, the locking ball  22  is pushed forward by spring  25 , and locks the carrier cover  16 . 
     A second cross section of the second embodiment of the carrier  14  is shown in  FIG. 3B , taken along line  3 B- 3 B of  FIG. 3 . This view further illustrates the relationship of carrier body  15  and carrier cover  16 . 
     A second embodiment of the carrier  14 ′ is shown in  FIG. 4 . The only difference between the first and second embodiments of carrier  14 / 14 ′ is the method of locking carrier cover  16  into the open or closed positions. 
     A sectional view of second carrier  14 ′ is shown in  FIG. 4A , taken along line  4 A- 4 A of  FIG. 4 . The cover spring  23  is shown forcing second carrier cover  16 ′ into the locked open position (to the left in  FIG. 4A ). The locking is accomplished by locking pin  27  engaging pin receptacle  29 A. Carrier cover  16 ′ is placed into the closed position by pulling carrier cover  16 ′ to a forward position (to the right in  FIG. 4A ), rotating the carrier cover 180 degrees relative to carrier body  15 , and allowing the cover spring  23  to push carrier cover  16 ′ to the rearward position (to the left in  FIG. 4A ), so locking pin  27  engages the second pin receptacle  29 B. 
     A second cross sectional view of the second embodiment of carrier  14 ′ is shown in  FIG. 4B , taken along line  4 B- 4 B of  FIG. 4 . This view serves to further illustrate the relationship of carrier body  15  and carrier cover  16 ′. 
     A second view of second carrier  14 ′ is shown in  FIG. 5 , with carrier cover  16 ′ pulled forward to reveal locking pin  27 . When carrier cover  16 ′ is pulled forward as shown, it may be manually rotated into the open or closed position. 
     A second sectional view of the second locking embodiment is shown in  FIG. 5A , taken along line  5 A- 5 A of  FIG. 5 . Here, locking pin  27  is shown disengaged from pin receptacle  29 A. The cover spring  23  is shown in the compressed condition. 
     An additional cross section of this embodiment of carrier  14 ′ is shown in  FIG. 5B , taken along line  5 B- 5 B of  FIG. 5 . This view serves to further illustrate the relationship of carrier body  15  and carrier cover  16 ′. 
     Other methods of locking the cover in an open or closed position are possible. These other means include other spring arrangements, spring loaded detents, friction fits, and the like. These other means are intended to fall within the scope of the present invention. 
     A second embodiment of a tunneling and carrying tool, made in accordance with the present invention, is a tool  9 ′ as shown in  FIG. 6 . Tool  9 ′ includes an optional tissue expander  18  and mating connector  20 . Mating connector  20  includes a tunneling end  21  which is shaped to facilitate the tunneling function. The contour of mating connector  20  matches the basic shape of a male connector on the end of the electrode lead  7  and is able to engage (plug into) the lead extension connector  40 . When used, the tissue expander  18  is located behind mating connector  20 . The purpose of tissue expander  18  is to expand the tunnel in order to reduce the drag on lead extension connector  40  and electrode lead extension  34 , when lead extension connector  40  and electrode lead extension  34  are pulled through the tunnel. 
     A third embodiment of the present invention comprises a tool  9 ″, as shown in  FIG. 7 . Tool  9 ″ includes a detachable carrier  32 . The electrode lead extension  34  is provided by the manufacturer with lead extension connector  40  inserted into the detachable carrier  32 . Tool  9 ″ further includes a second mating connector  20 ′ which is designed to engage detachable carrier  32 . The mating connector  20 ′ includes a tunneling end  21 ′ similar to tunneling end  21  as described above and shown in  FIG. 6 . 
     A top view of the tool  9 ″ is illustrated in  FIG. 8  and shows detachable carrier  32  connected to the rod  12  of tool  9 ″. The lead extension connector  40  is shown resting in the detachable carrier  32 , and a section of the electrode lead extension  34  is shown removably inserted into the lead guide  24 . 
     The sectional view shown in  FIG. 8A , taken along the line  8 A- 8 A of  FIG. 8 , shows a garter spring  36 , contained in detachable carrier  32 , that disengagably engages mating connector  20 ′ to attach detachable carrier  32  to rod  12 . It is to be understood, however, that various methods of attaching the detachable carrier to rod  12  exist (e.g., O-rings, threads, etc.), and the present invention is not intended to be limited to the embodiment recited herein. 
     Detachable carrier  32  defines a carrier cavity  28  into which lead extension connector  40  is removably insertable through a cavity opening  48 . Detachable carrier  32  further defines a lead guide  24  into which a section of electrode lead extension  34  is removably pressed to help retain lead extension connector  40  in carrier cavity  28 . In one preferred embodiment, the lead extension connector  40  is inserted into carrier cavity  28  as part of the manufacturing process and is delivered in this configuration. However, the detachable carrier  32  and electrode lead extension  34  could be delivered separately and assembled before use. 
     The strong connection between tool  9 ″ and detachable carrier  32  of this embodiment (and other embodiments herein) ensures that the detachable carrier  32  does not detach from tool  9 ″ while detachable carrier  32  is being pulled through the tunnel. Additionally, detachable carrier  32  provides protection for lead extension connector  40  until the electrode lead extension  34  is in place, and lead extension connector  40  is removed from detachable carrier  32 . 
     Turning next to  FIG. 9 , a second embodiment of a detachable carrier  32 ′ is illustrated. Detachable carrier  32 ′ includes a carrier break ring  38  that replaces the opening  48  to carrier cavity  28 . Once detachable carrier  32 ′ has been carried through the tunnel, detachable carrier  32 ′ is broken at carrier break ring  38  and discarded. When detachable carrier  32 ′ is broken at carrier break ring  38 , the detachable carrier also separates at carrier break joint  46 , thus allowing lead extension connector  40  to be easily removed from detachable carrier  32 ′. In this embodiment, detachable daffier  32 ′ no longer requires an opening to the carrier cavity  28  that may snag on body tissue when it is carried through the tunnel. Detachable carrier  32 ′ also provides secure containment for lead extension connector  40  while electrode lead extension  34  is being carried through the tunnel, and permits extraction of the lead extension connector  40  from carrier  32 ′ with negligible force. Various other methods of making a closed detachable carrier that may be opened by breaking or flexing are possible (e.g., with break joints, peel-away tabs, or the like, in a variety of locations), and are intended to come within the scope of the present invention. 
     A cross sectional view of detachable carrier  32 ′ is shown in  FIG. 9A , taken along section line  9 A- 9 A of  FIG. 9 . Cooperation between a third mating connector  20 ″ and a connector port  50  permits detachable carrier  32 ′ to pivot where it attaches to the mating connector  20 ″ of tool  9 ″. As shown in  FIG. 9A , this pivoting is accomplished by lengthening the small diameter section of mating connector  20 ″, moving garter spring  36  nearer to carrier end  42 , and, optionally, beveling connector port  50  at carrier end  42 . When detachable carrier  32 ′ is pulled past bone or inflexible tissue, the ability to pivot reduces the force required to pull the carrier past such bone or tissue, and the disturbance of surrounding tissue is minimized. A variety of methods for creating a pivoting connection exist (e.g., ball and socket joint) and the device described here is an example of only one embodiment of many that are intended to come within the scope of the present invention. 
     A fourth embodiment of a tunneling and carrying tool, made in accordance with the present invention, comprises a tool  9 ′″, as shown in  FIG. 10 . Tool  9 ′″ comprises a second handle  10 ′, a rod  12 , a second carrier body  15 ′, and a removable carrier cover  16 ′. In  FIG. 10 , the removable carrier cover  16 ′ is in place over carrier body  15 ′. The entire removable carrier cover  16 ′ is in view, but just the rearward end of carrier body  15 ′ can be seen. Removable carrier cover  16 ′ has a cover tunneling end  52  for tunneling. 
     The tool  9 ′″ with removable carrier cover  16 ′ removed is shown in  FIG. 10A . Lead extension connector  40  is shown inserted into carrier body  15 ′. 
     A detailed view of carrier body  15 ′ and removable carrier cover  16 ′ is shown in  FIG. 11 . An O-ring  54  is held substantially captive in a groove in the exterior of carrier body  15 ′ near carrier end  42 . The carrier cavity  28  is partially open to permit insertion of lead extension connector  40  therein. Lead guide  24  is provided at carrier tip  44 . A section of electrode lead extension  34  is inserted into lead guide  24  to help secure lead extension connector  40  in carrier cavity  28 . Removable carrier cover  16 ′ includes an O-ring channel  56  on the end opposite cover tunneling end  52 . When removable carrier cover  16 ′ is slipped onto carrier body  15 ′, O-ring  54  engages O-ring channel  56  to retain removable carrier cover  16 ′ on carrier body  15 ′. Various other methods may be exercised to retain a carrier cover on a carrier body, for example, a friction fit, a ball and detent, threads, and the like, and tunneling and carrying tools exercising those other methods are intended to come within the scope of the present invention. 
     A fifth embodiment of a tunneling and carrying tool, made in accordance with the present invention, comprises a tool  60 , as shown in  FIG. 12 . Tool  60  comprises a handle  66 , a rod  62 , a coupler  64  connecting handle  66  to rod  62 , a carrier  70 , and a tunneler comprising a removable carrier cover  68 . In  FIG. 12 , removable carrier cover  68  is in place, partially covering carrier  70 . Carrier cover  68  may be removed from carrier  70  and rod  62  may be detached from coupler  64 , as shown in  FIG. 12A . 
     A detailed view of carrier  70  and carrier cover  68  is seen in  FIG. 13 . Carrier threads  72  are defined on the exterior of carrier  70 . Carrier threads  72  cooperate with threads inside carrier cover  68  to attach cover  68  to carrier  70 . Carrier cover  68  is somewhat bullet shaped to facilitate the use of cover  68  to tunnel through body tissue. As shown in  FIG. 13 , the outer surface of cover  68  may include sunken portions  68 ′ or any other suitable texturing (e.g., bumps, a rubberized section, engraving, or the like) to facilitate handling (e.g., screwing and unscrewing) of the carrier cover  68 . Carrier cover  68  may be attached to a carrier body by means other than threads (e.g., an o-ring and o-ring channel, a friction fit, a snap fit, and/or the like), and a carrier utilizing these other attaching means falls within the scope of the present invention. 
     In the present embodiment, at least two carrier cavities  74  are provided in carrier  70 , wherein each carrier cavity  74  is adapted to receive a lead, or lead extension  34 . Of course, the present embodiment is readily adapted for use with one lead extension  34 , via one carrier cavity  74 . Carrier cover  68  is preferably, but not necessarily, about 0.330 inches in outside diameter. Carrier  70  and carrier cover  68  are preferably made from ULTEM® 1100F manufactured by G.E. Plastics (Pittsfield, Mass.). Modifications to the dimensions and materials recited here may be made to accommodate various needs, such as a variety of lead extensions  34 . 
     As shown in  FIG. 14 , handle  66  is attached to a handle shaft  67 , and the handle shaft  67  defines a shaft coupler end  79 . Handle shaft  67  is shown detached from coupler  64  in  FIG. 14 . A cross-sectional view of the cooperation of handle shaft  67  with coupler  64  is depicted in  FIG. 14A . An isometric view of the handle  66  and handle shaft  67  is shown in  FIG. 14B . Handle  66  (and any handle described herein, e.g., handle  10 ,  10 ′) may be any suitable shape and material(s), for example, ULTEM® 1000, ULTEM® 1100F, 304 stainless steel, or the like. 
     Coupler  64  defines a coupler neck  76 , and handle shaft  67  defines a shaft step  78 . Handle shaft  67  and coupler  64  are assembled by forcing shaft step  78  past coupler neck  76  to form a substantially permanent attachment (i.e., handle shaft  67  may be removed from coupler  64  by sufficient force, but will not become detached in normal use). Coupler  64  is preferably made from ULTEM® 1100F, ULTEM® 1000, or 304 stainless steel, and handle shaft  67  is preferably made from 304 stainless steel or other steel (e.g., 316 stainless, 17-4 PH stainless); however, these materials are modifiable as needed or desired. Handle shaft  67  further defines a shaft tongue  80  on shaft coupler end  79  (i.e., on the end of handle shaft  67  opposite the handle  66 .) Shaft tongue  80 , described in more detail presently, defines a substantially semi-circular cross-section offset from the longitudinal axis of handle shaft  67 . 
     Coupler  64  and rod handle end  85  of rod  62  are shown in  FIG. 15 . Coupler  64  defines internal coupler threads  82  (see  FIG. 15A ) for connecting rod  62  to coupler  64 . A rod tongue  86  extends from rod threads  84  of rod handle end  85 . Rod tongue  86  defines a substantially semi-circular cross-section offset from the longitudinal axis of rod  62 . Rod threads  84  are defined on the portion of rod  62  abutting rod tongue  86 . A cross-section of coupler  64  taken along line  15 A- 15 A of  FIG. 15  is shown in  FIG. 15A , with rod handle end  85  attached to coupler  64  by cooperation of rod threads  84  and coupler threads  82  (see also  FIG. 14A ). An isometric view of rod handle end  85  of rod  62  is shown in  FIG. 15B . 
     Another cross-sectional view of coupler  64  taken along line  15 A- 15 A of  FIG. 15 , and depicting the cooperation of shaft tongue  80  with rod tongue  86 , is shown in  FIG. 15C . When only handle shaft  67  is attached to coupler  64 , coupler  64  is free to rotate relative to handle shaft  67 . When rod  62  is connected to coupler  64  by cooperation of coupler threads  82  with rod threads  84 , shaft tongue  80  cooperates with rod tongue  86  to rotationally lock handle shaft  67  to rod  62 . Shaft tongue and rod tongue may define other than semi-circular shapes (e.g., stepped shapes), and a tool including any structure providing a rotational lock between a handle shaft and a rod falls within the scope of the present invention. 
     Rod  62  is shown in three views in  FIGS. 16A ,  16 B, and  16 C. A top view in  FIG. 16A  shows rod handle end  85  (including rod tongue  86  and rod threads  84 ) and rod carrier end  89  (including rod flats  88 , rod groove  90 , and rod end portion  91 ). The functions of the rod flats  88 , rod groove  90 , and rod end portion  91  are depicted in  FIGS. 18B and 18C , as described presently. A side view of rod  62  is provided in  FIG. 16B , and an isometric view of rod carrier end  89  is shown in  FIG. 16C . The diameter of rod  62  may be, for instance, between about 0.120 inches and about 0.127 inches, such as about 0.125 inches. The length of rod  62  (including rod handle end  85  and rod carrier end  89 ) may be about 10.17 inches. Rod  62  is preferably, but not necessarily, made from 304 stainless steel or other steel (e.g., 316 stainless, 17-4 PH stainless). 
     Rod carrier end  89  and carrier  70  are shown in  FIG. 17 . Carrier  70  has a distal end  73  opposite rod  62 . Carrier  70  defines cavity mouths  71  at distal end  73 , wherein leads may be inserted into the cavity mouths  71 . 
     A cross-sectional view of carrier  70 , taken along line  17 A- 17 A of  FIG. 17 , is shown in  FIG. 17A . The cavity mouths  71  are seen to define a tapered entry  71   a  connecting with a round passage  71   b . Taper  71   a  is sufficiently wide to allow insertion of a lead into round passage  71   b , and sufficiently narrow to retain the lead within passage  71   b  when tool  60  is pulled through the tunnel. Generally, lead extension connector  40  will be inserted into carrier cavity  74 , and the lead portion adjacent to the lead extension connector  40  will be pushed into cavity mouth  71  to retain the lead in carrier  70 . 
     Cross-sectional views of carrier  70 , taken along line  17 B- 17 B of  FIG. 17 , are shown in  FIGS. 18A ,  18 B, and  18 C. A carrier mouth  92  is provided for insertion of rod  62  into carrier  70 . Two carrier pin holes  94  are defined in carrier  70 . Two carrier pins  96  reside in the carrier pin holes  94 . The carrier pins  96  retain rod  62  in carrier mouth  92  via rod end portion  91 , and, depending on the position of rod  62 , either allow rod  62  to rotate within carrier mouth  92 , or rotationally lock rod  62  relative to carrier  70 . The carrier pins  96  may be held in the carrier pin holes  94  by a press fit between the carrier pins  96  the carrier pin holes  94  or other suitable means. The carrier pins  96  are preferably, but not necessarily, made from 316L SS. 
     In  FIG. 18B , rod  62  is shown pushed into a forward position in carrier  70 , as indicated by arrow  98 . In such forward position, carrier pins  96  cooperate with rod flats  88  (see  FIGS. 16A ,  16 B, and  16 C) to prevent rotation of rod  62  relative to carrier  70  (i.e., rod  62  is rotationally locked). In  FIG. 18C , rod  62  is shown pulled into a rearward position in carrier  70 , as indicated by arrow  100 . In such rearward position, carrier pins  96  cooperate with rod groove  90  (see  FIGS. 16A ,  16 B, and  16 C) to retain rod carrier end  89  in carrier  70 , while allowing rotation of rod  62  (i.e., rod  62  is rotationally unlocked) relative to carrier  70 . 
     The rotational locking and unlocking functions described in  FIGS. 18B and 18C  are accomplished using two rod flats  88 , a groove  90 , and two carrier pins  96 . It is to be understood, however, that tools with more or less than two rod flats and two carrier pins are intended to come within the scope of the present invention. Further, other cooperating features may similarly provide rotational locking and unlocking functions. For example, grooves or teeth may be substituted for rod flats. A tunneling and carrying tool using these, or other means for rotationally locking and unlocking a rod carrier end and a carrier, are intended to come within the scope of the present invention. 
     A sixth embodiment of a tool of the present invention is shown in  FIG. 19 . A tunneler tool  102  comprises tunneler rod  104 , a tunneler handle end  106 , and a tunneling end  108 . Tunneler handle end  106  is adapted to cooperate with coupler  64  in the same way as rod handle end  85  (described in  FIGS. 15A and 15C ) cooperates with coupler  64 . The diameter of tunneler rod  104  may be, for example, between about 0.120 inches and about 0.127 inches, such as about 0.125 inches. The diameter of tunneling end  108  may be about 0.20 inches, and is typically smaller in diameter than carrier cover  68  described in  FIG. 13 . Tunneler tool  102  is preferably, but not necessarily, made from 304 stainless steel or other steel (e.g., 316 stainless, 17-4 PH stainless). 
     A tunneler tool straw  110  is shown in  FIG. 20 . The diameter of tool straw  110  is sufficiently large to allow rod  104  of tunneler tool  102  to be inserted through straw  110 , and straw  110  is somewhat shorter than tunneler rod  104 . In  FIG. 21 , tunneler tool  102  is shown positioned in straw  110 . Straw  110  is preferably, but not necessarily, made from polytetrafluoroethylene (PTFE). 
     Three views of a tool extension  112  are shown in  FIGS. 22A ,  22 B, and  22 C. Extension  112  comprises an extension handle end  114 , an extension rod  118 , and an extension carrier end  116 . Handle end  114  is adapted to cooperate with coupler  64  in the same way as rod handle end  85  (described in  FIGS. 15A and 15C ) cooperates with coupler  64 . Carrier end  116  is adapted to cooperate with coupler  64  in the same manner as shaft coupler end  79  (described in  FIGS. 14A and 15C ) cooperates with coupler  64 . Extension carrier end  116  of tool extension  112  is shown attached to coupler  64  in  FIG. 22C . 
     A seventh embodiment of a tunneling and carrying tool  120 , shown in  FIG. 23A , utilizes the same carrier  70  as the fifth embodiment, but includes a second rod  136 , a second coupler  126 , and a handle assembly  121 . A view of tool  120  with rod  136  detached from coupler  126 , and carrier cover  68  separated from carrier  70 , is shown in  FIG. 23B . 
     Details of the handle assembly  121  are shown in  FIG. 24A . The handle assembly  121  comprises a handle  122 , a handle shaft  124 , and coupler  126 , which includes a coupler cover  128 . A second detailed view of handle assembly  121  with the coupler cover  128  detached from coupler  126  is shown in  FIG. 24B . Coupler cover  128  is typically permanently attached to coupler  126 , by laser welding, for instance. However, coupler cover  128  may instead be removably attached by screws, clips, or the like, or may be semi-permanently attached by, e.g., adhesive. 
     An isometric view of handle shaft  124  is shown in  FIG. 25 . Handle shaft  124  is preferably about 1.4 inches long, and about 0.125 inches in diameter, but these dimensions (as well as others recited herein) may be modified. Handle shaft  124  includes a coupler end  130  defining a tuning-fork-like shape. A side view of handle shaft  124  is shown in  FIG. 25A . Coupler end  130  includes a forked end  132  and a neck  134 . The cross-section CS of the forked end  132  can be 0.115 inches±about 0.125 inches in diameter, such as about 0.123 inches in diameter. A fork mouth  133  of forked end  132  defines a gap G of about 0.055 inches±about 0.001 inches across, such as about 0.055 inches across, and may have a depth D of about 0.135 inches. The forked end  132  defines a fork length FL which may be about 0.190 inches. Neck  134 , adjacent to forked end  132 , has a reduced diameter of about 0.093 inches, and a neck length NL of about 0.075 inches. Again, these dimensions are variable. 
     Rod  136  is shown in  FIG. 26  with coupler  126  and carrier  70  (see  FIG. 23A ) detached. Rod  136  may be about 0.120 inches in diameter. A detailed side view of rod coupler end  138  and rod carrier end  139  is shown in  FIG. 26A . Rod coupler end  138  includes a tongue  140  adapted to cooperate with fork mouth  133  of handle shaft  134  shown in  FIG. 25A . Tongue  140  may have a tongue thickness TT of about 0.052 inches, and a tongue length TL of about 0.140 inches. A threaded shoulder  142  is defined next to the tongue  140 . Threaded shoulder  142  may be about 0.052 inches in diameter and about 0.040 inches long. Threads  142 ′ may be positioned on some or all of the length of threaded shoulder  142 , which threads  142 ′ may comprise 5-40 UNC threads, 4-48 UNF threads, 4-40 UNC threads, or the like. 
     An isometric view of coupler  126  without cover  128  is shown in  FIG. 27 , and a side view is shown in  FIG. 27A . Coupler  126  includes a rod end  125  and a handle end  127 . 
     A top view of coupler  126  is shown in  FIG. 28 , and a cross-sectional view of coupler  126  taken along line  28 A- 28 A of  FIG. 28  is shown in  FIG. 28A . Rod end  125  defines a substantially cylindrical rod mouth  129 , which includes coupler threads  131 . Rod end  125  and coupler threads  131  are adapted to cooperate with the threaded shoulder  142  of rod  136 . Handle end  127  of coupler  126  defines a substantially cylindrical shaft mouth  143  including a coupler shoulder  144 . Shaft mouth  143  and coupler shoulder  144  are adapted to cooperate with shaft coupler end  130  ( FIGS. 25 and 25A ), wherein coupler shoulder  144  rotatable engages neck  134  ( FIG. 25A ) to retain the shaft in the carrier once carrier cover  128  is in place. The dimensions of rod mouth  129  and shaft mouth  143  are defined such that when rod  136  is retained in coupler  126  by threads  131 , and shaft  124  is retained in coupler  126  by shoulder  144 , tongue  140  of the shaft engages fork  132  of the rod, thus preventing rotation of rod  136  relative to shaft  124 . Rod  136  may be attached or detached from coupler  126  by twisting rod  136  relative to the coupler  126 . 
     An isometric view of upside-down coupler cover  128  is shown in  FIG. 29 . An end view of coupler cover  128 , taken from handle end  127 , is shown in  FIG. 30 , and a cross-sectional view of the coupler cover  128  taken along line  30 A- 30 A, is shown in  FIG. 30A . Coupler cover  128  defines a cover interior  150  substantially mirroring shaft mouth  143  of coupler  126  ( FIGS. 28 and 28A ). Cover interior  150  includes a cover shoulder  154  which cooperates with coupler shoulder  144  ( FIG. 28A ) in engaging neck  134  of handle shaft  124  to rotatably retain shaft  124  in coupler  126 . 
     Tool  120  preferably utilizes the same carrier as described in  FIGS. 13 ,  17 ,  18 A,  18 B, and  18 C, and the cooperation of rod  136  with carrier  70  is as described in  FIGS. 18A ,  18 B, and  18 C. However, tool  120  may also be utilized with other carriers. 
     Tool  120  may cooperate with a second tunneler tool similar to the tunneler tool  102  ( FIG. 19 ), wherein the second tunneler tool includes a coupler end adapted to cooperate with coupler  126 . Similarly, tool  120  may cooperate with a second extension similar to extension  112 , wherbin the second extension includes a threaded coupler end adapted to cooperate with coupler  126 , and a distal end attached to an additional coupler  126 . 
     A method for creating a tunnel and for carrying a lead or lead extension back through the tunnel using a tunneling and carrying tool of the invention, such as tool  60  in this example, is described by the following steps: 
     a) push the tool  60 , tunneling end (i.e., carrier cover  68 ) first, through tissue to create a tunnel; 
     b) after completing the tunnel, remove carrier cover  68  from carrier  70 ; 
     c) insert at least one lead extension connector  40  into at least one carrier cavity  74  of carrier  70 ; and 
     d) pull the tool  60 , with attached lead or lead extension  34  back through the tunnel. 
     A method for creating a tunnel and for passing a lead or lead extension back through the tunnel using a tool of the invention, such as tunneler tool  102  with tool straw  110 , in this example, is described by the following steps: 
     a) push tunneling tool  102 , with the tool straw  110  in place over tunneler rod  104 , through tissue to create a tunnel; 
     b) after completing the tunnel, detach tunneling tool  102  from handle  66 ; 
     c) remove tool  102  from straw  110 , leaving straw  110  in the tunnel; 
     d) pass a lead or lead extension  34  through straw  110 ; and 
     e) pull straw  110  out of the tunnel. 
     The method for creating a tunnel using the tunneler tool  102  may similarly be performed using the tool  60  or the tool  120 , however, carrier  70  and carrier cover  68  generally have a larger diameter than tunneling end  108 , and thus result in a more invasive procedure. Tool  120  may in general be substituted for tool  60  in any method of use, including the method recited above. 
     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.