Abstract:
An implantable electrical lead comprising an elongate lead body comprising first and second ends and an outer housing defining an interior channel. At least one electrical contact is positioned along the elongate lead body. An anchoring system is disposed at one end of the elongate lead body. The anchoring system is movable between an elongate configuration and a compressed configuration. The compressed configuration has a greater diameter than the elongate configuration. A linkage is provided having a first end attached to the anchoring system, an intermediate portion disposed within the interior channel of the elongate lead body, and a second end disposed outside of the elongate lead body adjacent to the second end of the elongate lead body. Movement of the linkage away from the elongate lead body moves the anchoring system from the elongate configuration to the compressed configuration.

Description:
FIELD OF INVENTION 
       [0001]    The present invention is related to lead stimulation therapy. More specifically, the present invention is related to implantable medical electrical leads delivering stimulation therapy and to the prevention of lead migration from the insertion site, such as the spinal column or brain. 
       BACKGROUND 
       [0002]    Patients with intractable back pain that are unresponsive to conventional therapies such as surgical intervention, injection therapy, physical therapy, or narcotic analgesics can be treated with a lead stimulator, which consists of implantable leads with electrodes connected to a pulse generator. The leads, with electrodes, are inserted via an epidural needle into the epidural space. The leads are placed along the spinal cord in the epidural space such that the pulse generator can send an electrical impulse through the leads and electrodes over the spinal cord to have the effect of blocking the pain sensation in the spinal cord. 
         [0003]    During conventional spinal cord therapy, the lead of the stimulator is typically secured by an anchor outside of the spinal canal in the fascia with a suture or staples to prevent migration of the lead. However, a common complication in a high percentage of patients treated with spinal cord stimulation (i.e., over twenty percent) is lead migration. Lead migration is caused by natural movements of the body, which promote sliding of the lead in the epidural space. Lead migration can result in loss of stimulation in the painful area of the spine, and may require lead revision, which can increase surgical costs and the risk of infection with each additional surgery. 
         [0004]    A need exists for an improved lead anchoring system to securely anchor the lead in a desired location, such as the epidural space or the brain to reduce lead migration. There also exists a need for a system to securely anchor a lead in a desired location with reduced mechanical parts and minimal invasiveness. 
       SUMMARY 
       [0005]    An embodiment of the present invention is directed to an implantable electrical lead comprising an elongate lead body comprising first and second ends and an outer housing defining an interior channel. At least one electrical contact is positioned along the elongate lead body. An anchoring system is disposed at one end of the elongate lead body. The anchoring system is movable between an elongate configuration and a compressed configuration. The compressed configuration has a greater diameter than the elongate configuration. A linkage is provided having a first end attached to the anchoring system, an intermediate portion disposed within the interior channel of the elongate lead body, and a second end disposed outside of the elongate lead body adjacent to the second end of the elongate lead body. Movement of the linkage away from the elongate lead body moves the anchoring system from the elongate configuration to the compressed configuration. 
         [0006]    A method for inserting an implantable electrical lead in an epidural space of a spinal column comprising providing a lead having a proximal end, a distal end, an outer wall, and a hollow interior. The distal end has a self-anchoring system with a plurality of slits in the outer wall defining a plurality of strips. At least one electrical contact positioned on the outer wall. A linkage is provided having a first portion within the hollow interior of the elongate body and connected to the distal end of the elongate body, and a second portion exterior to the proximal end of the elongate body. The method further comprises positioning the lead in a desired location along the spinal column, and pulling the linkage of the catheter to actuate the self-anchoring system by compressing and radially expanding the plurality of strips. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0007]    The foregoing summary, as well as the following detailed description of the preferred embodiments of the invention will be better understood when read in conjunction with the appended drawings. For purposes of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the scope of the invention is not limited to precise arrangements and instrumentalities shown. 
           [0008]    In the drawings: 
           [0009]      FIG. 1  is a perspective view of a self-anchoring lead according to the present invention with the anchoring system in the elongate configuration. 
           [0010]      FIG. 1A  is a cross-sectional view of the self-anchoring lead of  FIG. 1 . 
           [0011]      FIG. 2  is a perspective view of the self-anchoring lead of  FIG. 1  with the anchoring system in the compressed configuration. 
           [0012]      FIG. 3  is a transverse cross-sectional view of the spinal column showing the self-anchoring lead of the present invention inserted in the epidural space in the elongate configuration. 
           [0013]      FIG. 4  is a transverse cross-sectional view of the spinal column showing the self-anchoring lead of the present invention inserted in the epidural space in the compressed configuration. 
           [0014]      FIG. 5  is a perspective view of an alternative embodiment of a self-anchoring lead without a manual locking system. 
           [0015]      FIG. 6  is a perspective view of the self-anchoring lead of the present invention in an alternate compressed configuration. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]      FIGS. 1 ,  1 A, and  2  illustrate a self-anchoring lead or catheter  10  for delivering electrical impulses to a spinal cord according to the present invention. As shown in  FIGS. 1 and 1A , the lead  10  includes a distal end (A) in which an anchoring system  20  is located, an elongate body (E), which includes a distal electrode portion (B) with electrical contacts  30  and a proximal electrode portion (C), with electrical contacts  40 , and a proximal end (D) in which a locking system  50  can be located. The lead  10  preferably has a housing  60  surrounding an interior channel  70  which houses a linkage  80 . Any suitable linkage can be used without departing from the spirit of this invention, including without limitation, a cable or wire. The linkage  80  is secured to the anchoring system at the distal end (A) of the lead, and has a portion  85  that can be exposed outside of the interior channel  70  adjacent to the proximal end (D) of the lead  10 . In a preferred embodiment, a metal ball  90  can be attached to the linkage  80  and the anchoring system  20  to secure the linkage  80  to the distal end (A) of the lead  10 . However, the linkage  80  can be secured directly to the distal end (A) of the anchoring system  20 . The linkage can also be connected to the anchoring system  20  in any other manner understood by one of skill in the art. 
         [0017]    Materials and methods of making leads are well known to those skilled in the art. Such techniques include extrusion and coextrusion. The lead  10  of the present invention can be made of any suitable lead material known in the art, including, without limitation, polymeric materials, such as polyamide (nylon), polyurethane, and plastic. Alternatively, the distal end (A) of the lead can be made from a different material than the remainder of the lead  10  so that the anchoring system  20  can be of a material that is softer or more rigid than the remainder of the lead  10 . In addition, it is preferred that the lead  10  include a radiopath material to increase the detectability of the lead  10  during surgical implantation of the lead or under X-ray or radio-imaging. 
         [0018]      FIGS. 1 and 1A  depict the anchoring system in the elongate configuration. The anchoring system  20  is preferably comprised of a distal end (A) of the lead  10  having a plurality of slit or cutouts  100  in the housing  60  such that strips  110  of the housing are provided between the slits  100 . The size and number of slits  100  can vary depending on the anatomy of the patient, the intended location for insertion, such as the spinal column or brain, and the intended rigidity/flexibility of the anchoring system  20 . 
         [0019]    The distal and proximal electrode contacts  30 ,  40  deliver the electrical current from an electrical source, such as a pulse generator (not shown), to the spinal cord. Proximal electrode contacts  40  can be enveloped by a connector  120  having an extension  130  that leads to the electrical source. Any suitable electrical source can be used without departing from the spirit of this invention, including without limitation, a battery pack that is implanted under the skin or a battery pack that is external to the body. 
         [0020]    Those of skill in the art will recognize that the dimensions of the lead  10  can vary based on factors which can include, without limitation, the anatomy of the patient (i.e., size of the epidural space or the brain) and the intended insertion location, such as the spinal column or brain. For example, in spinal cord lead therapy applications, the length of the lead  10  typically ranges from 10 to 100 centimeters, and more typically between 30 and 65 cm. The outer diameter of the lead  10  is typically between 0.5 and 5 millimeters, and more typically 1.0 to 2.5 mm. The linkage  80  is longer than the lead, and is preferably about 1-5 centimeters longer than the lead, and more preferably 2 centimeters longer than the lead. 
         [0021]      FIG. 2  illustrates the lead  10  with the anchoring system in the compressed configuration to secure the lead  10  in the desired location, such as the epidural space or brain. Pulling or moving the linkage  80  away from the lead  10  stresses the strips  110  of the anchoring system  20  to compress and radially expand to have an increased diameter as compared to the elongate configuration. When the linkage  80  of the lead  10  is pulled, the strips  110  will radially expand into a shape that is best for the anatomical space in which the lead  10  was inserted. For example, in certain instances, only one half of the self-anchoring system  20  may expand when half of the lead  10  meets resistance such that it cannot expand. The slits  100  in the self-anchoring system  20  can be arranged in a manner to provide the proper shape for the anatomical space in which the lead will be inserted. For example, there could be two slits  100  and two strips  100  wherein the expanded configuration of the anchoring system  20  will have two primary radially expanded portions. 
         [0022]    The linkage  80  can be locked in place by engaging locking system  50  to maintain the position of the strips  110 . The locking system  50  can comprise any suitable locking system for maintaining the linkage  80  at a desired position. For example, and without limitation, the locking system  50  can consist of an orbital tapering lock or fastener that is secured around a helical ridge of the proximal end (D) of the lead  10 . 
         [0023]    The length and width of the anchoring system  20  depends on how far the strips  110  are required to radially expand. The width of the anchoring system  20  is also dependent on the anatomy of the patient, the intended insertion location, such as the spinal column or brain, and the size of the space at the desired insertion location. For example, the width of the epidural space generally increases along the spinal column from the cervical vertebrae to the thoracic vertebrae and to the lumbar vertebrae. 
         [0024]      FIG. 3  illustrates a transverse cross-sectional view of a spinal column  140  showing the placement of the lead  10  in its elongate configuration in the epidural space  150  of the spinal column. The spinal column  140  consists of vertebrae  160  and a spinal cord  170  with nerves exiting the spinal cord  180 . The epidural space  150  is located between the spinal cord  170  and vertebrae  160 .  FIG. 4  illustrates a transverse cross-sectional view of the spinal column  140  showing the lead  10  in its expanded configuration in the epidural space  150  of the spinal column  140 . 
         [0025]      FIG. 5  illustrates an alternate embodiment of the lead  10  without a locking system. In this embodiment, the strips  110  of the anchoring system  20  can be made of a polymeric material that retains its shape upon stress or the exposed portion  85  of the linkage  80  can be wrapped around the lead in order to maintain the anchoring system  20  in the desired position. Alternatively, the self-anchoring system  20  can be made of material that has a residual memory causing it to be biased in an expanded configuration. In order to move the anchoring system  20  to the elongate configuration, the linkage  80  must be pushed toward the distal end of the lead  10 . 
         [0026]      FIG. 6  illustrates the strips of the anchoring system  20  in an alternate compressed configuration. As shown, the linkage  80  is moved or pulled away from the lead  10  to a greater degree such that the strips  110  fully collapse upon themselves. 
         [0027]    The lead  10  according to the present invention may be delivered to the implantation site in the spinal column using methods well-known to those skilled in the art. The lead  10  may be inserted into a patient with an epidural needle. The epidural needle is placed in the epidural space  150  at the appropriate location along the spinal column  140  and the lead  10  is then inserted through the needle into the epidural space  140  at the desired location along a portion of the spinal cord that requires stimulation. During the initial positioning of the lead  10 , a trial connector can be connected to a stimulation programmer for trial stimulation to determine the final position of the stimulating lead  10 . The trial connector is placed on the proximal part of the lead  10  about the proximal electrode contacts  40 . Once the preferred location for the lead is determined, the trial connector  120  is detached from the lead  10 , the skin and subcutaneous tissue is cut down until fascia is exposed and the needle is removed. 
         [0028]    Once the trial connector is removed, a permanent connector  120  and extension  130  is inserted and connected with the lead  10  by inserting the proximal portion of the lead  10  and the linkage  80  through the opening of the connector  120  and the connector  120  is moved along the lead  10  until the proximal electrode contacts of the lead  10  and the connector  130  are aligned. The attached extension  130  will lead out to an electrical source. Once the connector  120  and extension  130  are in place, the linkage will extend out from the locking system  50 . Pulling or moving the linkage  80  away from the lead stresses the strips  110  of the anchoring system  20  to compress and radially expand to have an increased diameter as compared to the elongate configuration. The linkage  80  can be locked in place by engaging the locking system  50 . 
         [0029]    The lead anchoring system of the present invention reduces lead migration with minimal parts and minimal invasiveness. 
         [0030]    While various methods, configurations, and features of the present invention have been described above and shown in the drawings, one of ordinary skill in the art will appreciate from this disclosure that any combination of the above features can be used without departing from the scope of the present invention. It is also recognized by those skilled in the art that changes may be made to the above described methods and embodiments without departing from the broad inventive concept thereof.