Abstract:
A subcutaneous tunneling and carrying tool has a handle, a rod, and a carrier. The tool is used in connection with the implantation of electrical stimulators within the body, and more particularly facilitates the surgical procedure in the connection of an electrode lead extension to the implantable stimulator when the electrode and stimulator may not be co-located. In one embodiment, tunneling is accomplished by a tip that also serves to connect the tool to a disposable carrier in which the lead extension connector is packaged. In another embodiment the carrier comprises a carrier body and a removable cover, wherein the carrier cover covers a carrier cavity during tunneling and includes a tunneling end, and the carrier cover is removed after tunneling to expose the carrier cavity, into which carrier cavity the electrode lead extension is inserted to carry back through the tunnel.

Description:
The present application claims the benefit of U.S. Provisional Application Serial No. 60/166,560, filed Nov. 19, 1999 which application is incorporated herein by reference. 
    
    
     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, 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 is used to connect the IPG to the electrode array. For example, in the case of spinal cord stimulation, 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 and a tunneling tool is required to first create a subcutaneous tunnel from the location of the electrode lead to the location of the IPG, and then 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 advantageously addresses the above and other needs by providing an integrated subcutaneous tunneling and carrying tool, functionally similar to existing tools, that eliminates the need to unscrew a tunneling tip and screw on a separate carrying tip. The tool provided by the present invention is used to create a tunnel through body tissue, and then to carry an electrode lead extension 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. A tool according to the present invention includes either a cavity that the lead extension connector is inserted into, a male connector similar to the connector on the electrode lead, which male connector is connected to the lead extension connector, or a second male connector, which second connector connects to a disposable carrier which the lead extension connector is carried in. At least four embodiments of the present invention are envisioned. 
     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 electrode 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 and attached electrode lead extension. The mating connector is the same basic shape as the corresponding 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 electrode 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 electrode lead extension through the tunnel. 
     In a third embodiment, the lead extension connector of the electrode lead extension is delivered packaged in a disposable carrier. The disposable 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 disposable carrier. After the tunneling tool is pushed through the tissue, the disposable carrier is attached to the mating connector and then pulled back through the tunnel. After the carrier is pulled through the tunnel, the lead extension connector is removed, And the disposable 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 carrier cover, which carrier cover has a pointed 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. 
     It is thus a feature of the present invention to provide several embodiments 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 present invention will be described 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 the 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 the lines  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 the lines  3 B— 3 B of FIG. 3; 
     FIG. 4 depicts the details of a second embodiment of the carrier element of the first tool embodiment; 
     FIG. 4A shows a cross section of the carrier shown in FIG. 4 taken along the lines  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 the lines  4 B— 4 B of FIG. 4; 
     FIG. 5 depicts the details of the second embodiment of the carrier element 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 the lines  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 the lines  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. 8B shows a second cross section of the carrier shown in FIG. 8 taken along the lines  8 B— 8 B 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 the lines  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; and 
     FIG. 11 shows a more detailed view of the carrier body and carrier cover of the fourth embodiment. 
    
    
     Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of four alternative embodiments for carrying out the present invention. These include the best mode presently contemplated. The descriptions are not to be taken in a limiting sense, but are 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  is shown in FIG.  1 A and in FIG.  1 B. 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  includes an electrode lead  7 , and the electrode lead extension  34  includes a lead extension connector  40 . Generally, the electrode  6  and the IPG  8  cannot be co-located due to space limitations. Typical locations for the IPG  8  are beneath the rib cage as shown in FIG. 1A or above the buttock as shown in FIG.  1 B. This is because the electrode  6  must be located at the stimulation site, but space is not always available for the IPG  8  at the same location as the stimulation site. In these cases, a tool must be used to first create a subcutaneous tunnel through the body tissue from the site of the electrode lead  7  exit from the spinal column, 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 removable attached ( e.g, plugged into) the electrode lead  7 . 
     As seen in FIG. 1C, and as is evident from FIGS. 1A and 1B, the system  2  includes three main components, the electrode  6 , the electrode lead extension  34 , and the IPG  8 . The IPG  8  produces electrical current. The electrode lead extension  34  is connected to the IPG  8 , and carries the electrical current to the electrode  6 . The electrode  6  delivers the electrical current to the nerve. The electrode lead  7  has an end that is permanently connected to the electrode  6 , and has another end with a connector that exits the spinal column. The electrode lead connector  40  removably connects the electrode lead extension  34  to the electrode lead  7  and extends from the electrode lead  7  to the IPG  8 . 
     The present invention relates to an integrated subcutaneous tunneling and carrying tool. First the tool is used to create a subcutaneous tunnel from the site where the electrode lead  7  exits from the spinal column, to the implant location of the IPG  8 . Then the tool is used to carry the electrode lead extension  34  from the IPG  8  to the electrode lead  7  so that the lead extension connector  40  may be detachably connected to the electrode lead  7 . One embodiment of such a tool  9  is shown in FIG.  2  and comprises a handle  10 , a rod  12  and a carrier  14 . The carrier  14  has a pointed end that is used to create the tunnel from the electrode lead  7  to the IPG  8 , and a carrier cavity  28  used to carry the lead extension connector  40  and attached electrode lead extension  34  back through the tunnel. Thus, in this embodiment of the tool, the carrier  14  is used for both tunneling and carrying. 
     As shown in more detail in FIG. 3, the first embodiment of the carrier  14  of the tool  9  includes a carrier tunneling end  17  for tunneling, the carrier cavity  28  into which the lead extension connector  40  is inserted for carrying through the tunnel, and a lead guide  24  in which a portion of the electrode lead extension  34  is removably pressed to retain the lead extension connector  40  and attached electrode lead extension  34  while they are carried through the tunnel. 
     FIG. 3A shows a sectional view of the carrier  14  taken along the line  3 A— 3 A of FIG.  3 . The carrier cover  16  is shown as surrounding the carrier body  15 . The carrier cover  16  is rotatably attached to the 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 the lead extension connector  40  to be removably inserted into the carrier cavity  28 . To perform the tunneling process, the carrier cover  16  is rotated 180 degrees into the closed position where it covers the carrier cavity  28  to prevent body tissue from entering the carrier cavity  28 , or snagging the carrier cavity  28 . The carrier cover  16  also includes the carrier tunneling end  17  shaped to facilitate use of the carrier  14  for tunneling. When the tunneling procedure has been completed, the carrier cover  16  is pulled toward the carrier tunneling end  17  and rotated to expose the carrier cavity  28 . 
     The carrier cover  16  locking mechanism is also shown in the sectional view in FIG.  3 A. The locking mechanism comprises a spring  25  pushing a locking ball  22  to 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 the carrier cover  16 , the locking ball  22  pushes against the 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 the 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 the line  3 B— 3 B of FIG.  3 . This view further illustrates the relationship of the carrier body  15  and the 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 the carrier  14  is the method of locking the carrier cover  16  into the open or closed positions. 
     A sectional view of the second carrier  14 ′ is shown in FIG. 4A taken along the line  4 A— 4 A of FIG.  4 . The cover spring  23  is shown forcing the second cover  16 ′ to the rear (to the left in FIG.  4 A), which is into the locked position. The locking is accomplished by locking pin  27  engaging pin receptacle  29 A. The carrier cover  16 ′ is placed into the closed position by pulling the carrier cover  16 ′ to a forward position (to the right in FIG.  4 A), rotating the carrier cover 180 degrees relative to the carrier body  15 , and allowing the cover spring  23  to push the carrier cover  16 ′ to the rearward position (to the left in FIG.  4 A), so that the locking pin  27  engages the second pin receptacle  29 B. 
     A second cross sectional view of the second embodiment of the carrier  14  is shown in FIG. 4B taken along the line  4 - 4 B of FIG.  4 . This view serves to further illustrate the relationship of the carrier body  15  and the carrier cover  16 ′. 
     A second view of the second carrier  14 ′ is shown in FIG. 5 with the carrier cover pulled forward to reveal the locking pin  27 . When the 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 the line  5 A— 5 A of FIG.  5 . Here the locking pin  27  is shown disengaged from the pin receptacle  29 A. The cover spring  23  is shown in the compressed condition. 
     An additional cross section of this embodiment of the carrier  14  is shown in FIG. 5B taken along the line  5 B— 5 B of FIG.  5 . This view serves to further illustrate the relationship of the carrier body  15  and the carrier cover  16 ′. 
     It will be apparent to those skilled in the art that many equivalent methods of locking the cover in the open or closed position are possible. These include other spring arrangements, spring loaded detents, friction fits, etc., and these other methods 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, a tool  9 ′, is shown in FIG.  6 . The tool  9 ′ includes a tissue expander  18  and mating connector  20 . The mating connector  20  includes a tunneling end  21  which is shaped to facilitate the tunneling function. The contour of the 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 . The tissue expander  18  is located behind the mating connector  20 . The purpose of the tissue expander  18  is to expand the tunnel in order to reduce the drag on the lead extension connector  40  and electrode lead extension  34 , when the 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 . The tool  9 ″ includes a disposable carrier  32 . The electrode lead extension  34  is shipped from the manufacturer with the lead extension connector  40  inserted into the disposable carrier  32 . The tool  9 ″ further includes a second mating connector  20 ′ which is designed to engage the disposable carrier  32 . The mating connector  20 ′ includes the tunneling end  21  as described in FIG.  6 . 
     A top view of the tool  9 ″ is illustrates in FIG.  8  and shows the disposable carrier  32  connected to the rod  12  of the tool  9 ″. The lead extension connector  40  is shown resting in the disposable 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 the disposable carrier  32 , that disengagably engages the mating connector  20 ′, to attach the disposable carrier  32  to the rod  12 . It will be apparent to those skilled in the art.that many equivalent methods of attaching the disposable carrier to the rod  12  exist and the present invention is not intended to be limited to the embodiment recited herein. 
     The disposable carrier  32  defines a carrier cavity  28  into which the lead extension connector  40  is removably insertable through a cavity opening  48 . The disposable carrier  32  further defines a lead guide  24  into which a section of the electrode lead extension  34  is removably pressed to help retain the lead extension connector  40  in the carrier cavity  28 . In a preferred embodiment, the lead extension connector  40  is inserted into the carrier cavity  28  as part of the manufacturing process and is delivered in this configuration. However, the disposable carrier  32  and electrode lead extension  34  could be delivered separately and assembled before use. 
     Advantageously, the tool  9 ″ provides a stronger connection between the tool  9 ″ and the disposable carrier  32  than may be made with a tool that connects with the lead extension connector  40 . Such strong connection ensures that the disposable carrier  32  does not detach from the tool  9 ″ while the disposable carrier  32  is being pulled through the tunnel. Additionally, the disposable carrier  32  provides protection for the lead extension connector  40  until the electrode lead extension  34  is in place and the lead extension connector  40  is removed from the disposable carrier  32 . 
     A cross sectional view of the electrode lead extension  34  exiting the disposable carrier  32  through a lead guide  24  is illustrated in FIG.  8 B. The view shown in FIG. 8B is taken along the section line  8 B— 8 B of FIG.  8 . 
     Turning next to FIG. 9, a second embodiment of a disposable carrier  32 ′ is illustrated. The disposable carrier  32 ′ includes a carrier break ring  38  that replaces the opening to the carrier cavity  28 . Once the disposable carrier  32 ′ has been carried through the tunnel, the disposable carrier  32 ′ is broken at the carrier break ring  38  and discarded. When the disposable carrier  32 ′ is broken at the carrier break ring  38 , the disposable carrier separates into three parts along the carrier break joint  46  and the carrier break ring  38 , thus allowing the lead extension connector  40  to be easily removed from the disposable carrier  32 ′. Advantageously, the disposable carrier  32 ′ no longer requires an opening to the carrier cavity  28  that may snag on body tissue when it is carried through the tunnel. The disposable carrier  32 ′ also provides secure containment for the lead extension connector  40  while the lead extension connector  40  is being carried through the cavity, and permits extraction of the lead extension connector  40  with negligible force. Various other methods of making a closed disposable carrier, which may be opened by breaking or flexing, will be apparent to those skilled in the art, and are intended to come within the scope of the present invention. 
     A cross sectional view of the disposable carrier  32 ′ is shown in FIG. 9A taken along the section line  9 A— 9 A of FIG.  9 . Cooperation between a third mating connector  20 ″ and a connector port  50  permits the disposable carrier  32 ′ to pivot where it attaches to the mating connector  20 ″ of the tool  9 ″. In FIG. 9A this is accomplished by lengthening the small diameter section of the mating connector  20 ″, moving the garter spring  36  nearer to a rearward carrier end  42 , and beveling the connector port  50  at a rearward carrier end  42  of the disposable carrier  32 . Advantageously, when the disposable 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 will be apparent to those skilled in the art 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 . The 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 the carrier body  15 ′. The entire removable carrier cover  16 ′ is in view, but just the rearward end of the carrier body  15 ′ can be seen. The removable carrier cover  16 ′ has a cover tunneling end  52  for tunneling. 
     The tool  9 ′″ with the removable carrier cover  16 ′ removed is shown in FIG.  10 A. The lead extension connector  40  is shown inserted into the carrier body  15 ′. 
     A detailed view of the carrier body  15 ′ and removable carrier cover  16 ′ are shown in FIG.  11 . An O-ring  54  is held substantially captive in a groove in the exterior of the carrier body  15 ′ near the rearward carrier end  42 . The carrier cavity  28  is partially open to permit the insertion of the lead extension connector  40  therein. The lead guide  24  is provided at a forward carrier end  44 . A section of the electrode lead extension  34  is inserted into the lead guide  24  to help secure the lead extension connector  40  in the carrier cavity  28 . The removable carrier cover  16 ′ includes an O-ring channel  56  on the end opposite the cover tunneling end  52 . When the removable carrier cover  16 ′ is slipped onto the carrier body  15 ′, the O-ring  54  engages the O-ring channel  56  to retain the removable carrier cover  16 ′ on the carrier body  15 ′. Those skilled in the art will recognize various other methods of retaining a carrier cover on a carrier body, and tunneling and carrying tools exercising those other methods are intended to come within the scope of the present invention. 
     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.