Abstract:
Stabilizing array, which includes a body elongating the distal tip of an implantable cylindrical stimulator lead, a storable, deployable and retroflexing array element for stabilizing distal tip of said lead, a keeper for storing array element during implantation, and a deploying lumen within the body which accepts a deploying stylet. The invention is a refinement to the prior art of a cylindrical stimulator lead. The array element functions to minimize migration of permanently placed cylindrical stimulator leads.

Description:
REFERENCES CITED 
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         [0000]    
       
         
               
             
               
               
               
               
               
             
           
               
                   
               
               
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                 4,285,347 
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                 2005/0096718 A1 
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                 April 2006 
                 Cross et al. 
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                 2011/0022143 A1 
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       OTHER PUBLICATIONS 
       [0000]    
       
         Reina M A. Electron microscopy and the expansion of regional anesthesia knowledge. Techniques in Regional Anesthesia and Pain Management, Vol 6, No. 4 (October), 2002: pp 165-171 
         Andrès J. Epidural space and regional anesthesia. European Journal of Pain Supplements, 3 (2009): pp 55-63 
         Anderson J M. Inflamatory response to implants. ASAIO 1988; 11:101-107. 
         Anderson J M. Biological responses to materials. Annual Reviews Material Research 2001; 31:81-110. 
         Attorney, Agent, or Firm—R. Joseph Trojan, Esq. 
         Attorney Docket: 12-09-6445 
       
     
       TECHNICAL FIELD 
       [0008]    The invention relates to implantable medical devices, more particularly, implantable medical leads. 
       BACKGROUND 
       [0009]    Spinal cord stimulation is used as an analgesic in patients with chronic and refractory pain syndromes and has had success in the treatment of neurogenic bladder syndrome. 
         [0010]    Fundamentally a spinal cord stimulator consists of individually wired stimulator electrode contacts forming an electrode array which is incorporated into an implantable cylindrical or paddle lead. Stimulator electrode contacts are energized by a programmed stimulation sequence from a battery powered implantable pulse generator. To complete the circuit, the extra-epidural lead segment, which may require lead extensions, is tunneled under soft tissue where it plugs into the implantable pulse generator. Each medically implanted device is highly engineered for the integration of electronic components, coaxial porting and the use of durable biocompatible materials. 
         [0011]    A cylindrical stimulator lead is introduced into an individual by means of a percutaneous technique whereas the paddle lead is introduced after performing a more invasive laminotomy procedure. Both lead types are implanted within the epidural space and the electrode array is positioned over a specific and targeted region of the spinal cord known as the dorsal column. 
         [0012]    The positioning of the stimulator electrode array in a targeted location along the dorsal column is critical in determining the attenuation of chronic pain symptoms. Unfortunately lead migration, resulting in the loss of targeted dorsal column stimulation, is one of the common hardware related complications associated with spinal cord stimulator leads. This problem is associated more frequently with percutaneously placed cylindrical stimulator leads versus those of paddle designs. Patents are referenced for cylindrical stimulator leads that claim distal lead stability using glues, inflatable membranes, expanding wire loops, non-compliant loop-like elements and non-retroflexing tabs. Scar tissue formation into and round such elements may make retrograde removal of these leads difficult and potentially injurious to the contents of the epidural space. Furthermore, leads utilizing inflatable membranes to press against the epidural space have the potential for tissue ischemia and/or attenuated blood flow. Such leads may also limit the ability to place two stimulator leads side by side within the epidural space secondary to the space occupying volume of an expanded inflatable membrane. 
         [0013]    As such, patients may benefit by having the electrodes placed by means of a percutaneous technique rather than having to undergo a more invasive laminotomy procedure, but the benefit only holds if the entire system is stable, safe and provides long term pain control. 
       BRIEF SUMMARY OF THE INVENTION 
       [0014]    In accordance with the invention, there is a need for a system of dorsal column stimulation using a percutaneously placed epidural cylindrical stimulator lead(s) that allows for long term fixed stability of said leads distally positioned stimulator electrode contacts. Described herein are methods for optimizing the stabilization of said leads stimulator electrode contacts with the use of a storable, deployable and retroflexing array element. Storage (folding) of the array element provides a means of percutaneous placement of said lead. Deployment of the array element, where it assumes its intrinsic shape, fixes the distal tip of said lead with a self-gripping mechanical interaction and inflammatory response which leads to scar formation and long term fixation. 
         [0015]    Another purpose of the invention is provide a safe means of cylindrical stimulator lead removal utilizing a retrograde technique (prior art). A deployed array element has the ability to fold back on itself (retroflex) and assume a dimension no wider than any segment of the epidurally implanted cylindrical stimulator lead. Retroflexing of the array element upholds the practice of retrograde removal for the novel lead. 
         [0016]    The invention relates to the refinement of a medically implantable cylindrical stimulator lead comprising: proximal and distal ends; individually wired stimulator electrode contacts on said leads distal end; wired contacts on said leads proximal end; and a coaxial lumen originating at said leads proximal tip, for receiving a guiding stylet. 
         [0017]    The present invention relates, in one embodiment, to said cylindrical stimulator lead elongated distally by a stabilizing array comprising: a body continuous with the longitudinal axis said lead; a storable, deployable and retroflexing array element; a keeper (independent) of said stimulator electrode contacts for holding said array element in the stored (folded) position; a deploying lumen continuous with said coaxial lumen; contours on said body for accommodating said array element in stored and retroflexing positions; and radiopaque (x-ray) markers on said body and/or array element. 
         [0018]    The present invention relates, in another embodiment, to said cylindrical stimulator lead elongated distally by a stabilizing array comprising: a body continuous with the longitudinal axis of said lead; a storable, deployable and retroflexing array element; a keeper (dependent) on an individual stimulator electrode contact for holding said array element in the stored position; a deploying lumen continuous with said coaxial lumen; contours on said body for accommodating said array element in stored and retroflexing positions; and radiopaque markers on said body and/or array element. 
         [0019]    The present invention relates, in another embodiment to a stylet necessary for the deployment of the novel cylindrical stimulator leads array element comprising: a deploying stylet body; a control stop on said stylet body for contacting said leads proximal tip; and a deploying stylet integral with said stylet body, for insertion into said leads proximally originating coaxial lumen whereby advancement the deploying segment of said stylet, into said deploying lumen, induces the release of array element from the stored to deployed position. 
         [0020]    The present invention relates, in yet another embodiment, to a deploying handpiece, utilized for retaining a proximal segment of said novel lead and deploying array element, generally comprising: a deploying stylet; a plunger integral with said deploying stylet; a cylinder which accommodates said plunger; a retention feature for securing a proximal segment of said lead; a seating surface to align said leads proximal tip; flexible tabs wherein the proximal end of said lead can be loaded and un-loaded from said retention feature; and a locking tab which prevents inadvertent deployment of said array element during percutaneous positioning of the novel cylindrical stimulator lead. 
         [0021]    Henceforth, a cylindrical stimulator lead with the embodiment of said stabilizing array will be referred to as either the lead, novel lead, or cylindrical stimulator lead. Any further reference to the prior art of a cylindrical stimulator lead without said stabilizing array will be referred to as a non-stabilized lead or non-stabilized cylindrical stimulator lead. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
         [0022]    The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like references numerals refer to similar elements and in which: 
           [0023]      FIG. 1  (prior art) illustrates the relevant components of an implanted medical stimulator; 
           [0024]      FIG. 2  is the vertebral column illustrated in sagital, oblique and transverse partial dissections; 
           [0025]      FIG. 2B , according to the present invention, illustrates the deployed array element of the cylindrical stimulator lead positioned within the epidural space; 
           [0026]      FIG. 3A , according to the present invention, is a perspective view of a stabilizing array integral with a spinal cord stimulator lead; 
           [0027]      FIG. 3B , according to the present invention, is a perspective view of a stabilizing array (variation) integral with a spinal cord stimulator lead; 
           [0028]      FIG. 4 , according to the present invention, are perspective views of independent and dependent keepers which may be used in the stabilizing array and said (variation) of  FIG. 3 ; 
           [0029]      FIG. 5  is an exploded perspective view of the stimulator lead and stabilizing array according to the present invention; 
           [0030]      FIG. 6  is a partially assembled exploded perspective view of the stimulator lead and stabilizing array according to the present invention; 
           [0031]      FIG. 7 , according to the present invention, are perspective views of the stimulator lead and stabilizing array illustrating array element in deployed and stored positions; 
           [0032]      FIG. 8A  is a perspective axial cutaway view of the stimulator lead and stabilizing array according to the present invention; 
           [0033]      FIG. 8B , according to the present invention, is a perspective axial cutaway view of the stimulator lead and stabilizing array illustrating a stored array element and a integrally formed keeper; 
           [0034]      FIG. 9  is a perspective axial cutaway view of the stimulator lead and stabilizing array (variation) according to the present invention; 
           [0035]      FIG. 10A , according to the present invention, is a perspective view of the stimulator lead and stabilizing array illustrating array element in the retroflexed position; 
           [0036]      FIG. 10B , according to the present invention, is a perspective axial cutaway view of the stimulator lead and stabilizing array (variation) illustrating array element in the retroflexed position; 
           [0037]      FIG. 11A , according to the present invention, is a perspective view of a stylet used in the deployment of array element of stabilizing array and said (variation); 
           [0038]      FIGS. 11B and 14B  (prior art) as pertaining to the present invention, shows a proximal segment of the stimulator lead; 
           [0039]      FIG. 12 , according to the present invention, are perspective axial cutaway views of the stimulator lead and stabilizing array illustrating the deployment of the array element; 
           [0040]      FIG. 13  is a perspective view of the deploying handpiece according to the present invention; and 
           [0041]      FIG. 14A  is a top view of the deploying handpiece used in the deployment of array element of stabilizing array and said (variation). 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0042]    The present invention will now be described in detail with reference to a few embodiments thereof as illustrated in the accompanying detailed description, examples, drawings and claims. Numerous specific details are set fourth in order to provide a thorough understanding of the present invention. However, before the present devices, systems, and/or methods are disclosed and described, it is to be understood that this invention is not limited to the specific devices, systems, materials, dimensions, and/or methods disclosed unless otherwise specified, and, as such, can, of course, vary. It will be apparent, however, to those skilled in the art, that the present invention may be practiced without some or all of these specific details. Furthermore, those who work in the art will recognize that many modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not in limitation thereof. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. In other instances, well known process steps have not been described in detail in order not to unnecessarily obscure the present invention. Given that the present invention is a refinement to the prior art of a non-stabilized cylindrical stimulator lead, a few references and figures pertaining to the prior art are made in this detailed description of the invention. 
         [0043]    All of the details listed in  FIG. 1  pertain to prior art and are included to aid in the description of the present invention.  FIG. 1A  is a perspective view indicating the relevant components of an implanted medical stimulator which comprise: a non-stabilized cylindrical stimulator lead  12 ; an implantable pulse generator  11 ; and a removable guiding stylet  16 . 
         [0044]    Wired contacts  22  at the proximal end of the non-stabilized lead  12  plug into implantable, battery powered, pulse generator  11  or lead extensions (not shown). Electrode array  13  is composed of independently wired stimulator electrode contacts  14  which are energized by output from implantable pulse generator  11 . 
         [0045]      FIGS. 1B and 1C , cross-sectional and perspective views respectively, as taken from dissecting lines (A) and (B), show a characteristic depiction of the prior art as it pertains to insulating body  20  of non-stabilized lead  12 . Eight wire conduit lumens  18  and electrical conductor wires  17 , shown projecting from  FIG. 1C , are depicted radially around coaxial lumen  19  which is encircled by stylet guide  15 . Guiding stylet  16  is used to stiffen and direct non-stabilized lead  12 , and novel lead  23 , during percutaneous placement within the epidural space ( 103  of  FIG. 2 ). With reference to  FIG. 1 , the illustrated components of non-stabilized lead  12 , as taken from dissecting line (D) and those between dissection lines (A) and (B), remain unchanged for novel lead  23 . 
         [0046]    As illustrated throughout, and pertaining to prior art as referenced by Cross (US patent 2006/0089692 A1), stylet guide  15 , of non-stabilized lead  12  and novel lead  23 , is depicted as a coiled wire feature. In some instances stylet guide  15 , as referenced by Cross and further by Kuzma (U.S. Pat. No. 7,891,085 B1), is a unique construct or may be omitted whereby insulating body  20  serves as stylet guide  15 . 
         [0047]    Within the human vertebral canal, as illustrated in  FIG. 2 , the epidural space  103  is both a true and potential space. The potential part becomes a true space when solutions or air are injected in it or, in this case, when cylindrical stimulator lead(s) ( 23  of  FIG. 2B ) is placed within it. The epidural space  103  is a cylindrical compartment surrounding the dural sac  112  of the spinal canal  106  and is further defined anteriorly by the posterior longitudinal ligament  114 , and intervertebral discs  105 , laterally by the vertebral pedicals  115  form the intervertebral foramina (not shown) while posteriorly it is delimited by the vertebral laminas  116  and the ligamentum flavum  102 . The contents of epidural space  103  (not shown) includes nerve roots, connective tissue, variable amounts of fat and a venous plexuses. The external surface of the dural sac  112 , composed of collagen and elastic fibers, is free and does not adhere to the vertebral canal. 
         [0048]    The epidurally implanted distal segment of non-stabilized lead  12 , which includes electrode array  13 , has no inherent static or dynamic self-gripping elements, as such, non-stabilized lead  12  may move laterally and axially away from a targeted posterior midline position overriding the dorsal column ( 117  of  FIGS. 2B and 2C ) of the spinal cord  107 . Such movement may be one factor resulting in attenuated or failure of therapeutic dorsal column  117  stimulation. Axial movement, as noted by Cross (US patent 2006/0089692 A1), occurs by tensile forces on non-stabilized lead  12  imposed by patient postural changes. Tensile forces may also cause lead failure, extra-epidural anchor damage (not shown), or tissue damage. Cross includes features in non-stabilized lead  12  constructs that increases the modulus of elasticity in an effort to lessen the impact of tensile forces. Of note, axial movement in the distal segment of non-stabilized lead  12  may be exaggerated by the accepted art of extra-epidural anchoring of said lead to soft tissue generally at the level of lead insertion into the epidural space  103 . 
         [0049]    The main purpose of the invention is to provide the distal segment of cylindrical stimulator lead  23  with fixed stability within the epidural space  103 . By inference, fixed stability of the distal segment of lead  23  provides electrode array  13  stability over a targeted dorsal column  117  stimulation site which is significantly independent of patient postural changes. 
         [0050]    Initial stability of the distal segment of lead  23  is achieved by a self-gripping array element  26  which, once deployed in a plane generally parallel to the posterior aspect of the epidural space  103 , exerts resistance to axial and lateral movement by interacting with the connective tissues of the epidural space  103 , including the collagen and elastic fibers of the dural sac  112 . With reference to Reina and Andrès, scanning electron micrographs of the dural surface (dura)  104  show collagen and elastic fibers that are, to some extent, responsible for the initial securing the self-gripping feature of deployed array element  26 . 
         [0051]    Complementing the initial self-gripping interaction of deployed array element  26  is foreign body tissue inflammation and subsequent scar formation which encapsulates any permanent medical device. These processes have been assiduously characterized by Anderson et al. with respect to the general time course, cells involved, cell-cell interactions, and cell-biomaterial interactions. Within the epidural space  103 , scar formation will chronically fixate the distal segment of lead  23  in axial and lateral planes, thereby reducing distal segment movement of lead  23  away from the targeted dorsal column  117  stimulation site. 
         [0052]    The polymer selected for array element  26  will have the ability to return from a deformed state (temporary shape) to its intrinsic (permanent) shape. The permanent shape of array element  26  is the deployed configuration. The temporary (folded) shape is necessary for storage of the distal tips of array element  26  into keeper  27  and is mandatory for percutaneous placement of lead  23  within the epidural space  103 . As illustrated and discussed below, a retroflexed position of array element  26  is also achievable if retrograde removal of lead  23  is necessary. 
         [0053]    The deployed shape of array element  26  may be widely varied. It may, for example be somewhat rectilinear, curvilinear or a combination of the two. As an example, but not limitation,  FIG. 3 , shown in a perspective view, as taken from the distal segment of lead  23  across dissection line (A), depicts two embodiments of stabilizing array  24 . In one embodiment,  FIG. 3A , the deployed array element  26  is curvilinear, while that of the second embodiment,  FIG. 3B , depicts the deployed array element  26  as somewhat rectilinear. Both embodiments show that the deployed state of array element  26  is substantially perpendicular to the longitudinal axis of lead  23 . The embodiment of stabilizing array  24  depicted in  FIG. 3B , will be referred to as the (variation). As illustrated throughout, dissection line (C), taken across a distal segment of lead  23 , will only depict distal electrode contact  25  when referencing dependent keeper  27 ( c ) of  FIGS. 9 and 10B . 
         [0054]    One embodiment of stabilizing array  24 , and said (variation), is keeper  27 . Keeper  27  holds the distal tips of array element  26  in the stored (folded) position during percutaneous positioning of lead  23 . A stored array element  26  is substantially parallel to the longitudinal axis and no wider than any epidural segment of lead  23 . Keeper  27  is a static (non-movable) element and may be isolated (independent) or integral (dependent) with respect to distal electrode contact  25 . Keeper  27  may be formed as a separate piece, or pieces, that are assembled together to form keeper  27  within lead  23 . Alternatively, keeper  27  may be integrally formed as a single piece on insulating body  20 , body  28  or a combination of the two. 
         [0055]    In accordance with the invention,  FIGS. 4A and 4B  are depictions of independent keepers  27 ( a /b) shown in perspective positions. In this embodiment, independent keepers  27 ( a /b) are electrically isolated as it places stabilizing array  24 , and said (variation), distal to distal electrode contact  25 . Independent keepers  27 ( a /b) must prevent shear stress failure of lead  23  when deployable array element  26  is stored. It is likely that independent keepers  27 ( a /b) will be manufactured from a polymer or metal such as, but not limited to, cross-linked polyurethane, MP35N super Alloy™, stainless, titanium or the like. By way of example but not limitation, independent keeper  27 ( a ) is comprised of a ring  29  and collar  30 . Collar  30  functions as backstop ( 31  of  FIGS. 6 and 8 ), bonding surface and prevents electrical coupling with a potentially conductive stylet guide  15 . It is likely that collar  30  will be a polymer such as, but not limited to, polyurethane as referenced by Kuzma (U.S. Pat. No. 7,891,085 B1). Backstop  31  prevents reward movement of array element  26  during percutaneous positioning of lead  23 . The second independent keeper  27 ( b ) eliminates collar  30  and relies on insulating body  20  for the functions of backstop  31 , bonding surface and electrical decoupling. 
         [0056]    In accordance with the invention,  FIGS. 4C and 4D  are depictions of dependent keepers  27 ( c /d) shown in perspective positions. In this embodiment, dependent keepers  27 ( c /d) are integral with distal electrode contact  25 . As such, distal electrode contact  25  becomes part of stabilizing array  24  and said (variation). By way of example, but not limitation, dependent keeper  27 ( c ) is comprised of distal electrode contact  25  and insulating disc  33 . Insulating disc  33  functions as backstop  31 , bonding surface and prevents electrical coupling with a potentially conductive stylet guide  15 . It is likely that insulating disc  33  will be a polymer such as that used for collar  30 . The second dependent keeper  27 ( d ) eliminates insulating disc  33  and relies on insulating body  20  for the functions of backstop  31 , bonding surface and electrical decoupling. For illustrative purposes only, distal electrode contact  25  is only shown in axial cutaway depictions ( FIGS. 9 and 10B ) referencing dependent keeper  27 ( c ). 
         [0057]    In yet another embodiment, keeper  27  may be integrally formed as a single piece if insulating body  20  and stabilizing array  24 , including (variation) of, are formed concurrently. Alternatively, keeper  27  may be integrally formed on insulating body  20 , or body  28 , and then assembled (bonded) to complete stabilizing array  24  and said (variation). As an example, but not limitation,  FIG. 8B , a perspective axial cutaway as taken from dissection line (C), shows a construct using a molded insulating body  20  serving as keeper  27 , backstop  31  and bonding surface for body  28 . The polymer selected for such a construct, generally at the level of keeper  27 , or the entire lead  23 , must prevent failure, of said lead, secondary to torsion and shear stress caused by the stored array element  26 . 
         [0058]    Keepers  27 ( a /c) require bonding (fusion and/or encapsulation) to insulating body  20 , stylet guide  15 , if different from insulating body  20 , and body  28  if formed independently from insulating body  20 . Stylet guide  15 , if different from insulating body  20 , will not require bonding to keepers  27 ( b /d) because said keepers lack collar  30  and insulating disc  33  features respectively. 
         [0059]    Keeper  27  may be widely varied; for example, the surface in direct contact with the stored array element  26  may be smooth or include dents, slots, tabs or the like. These features allow keeper  27  to be configured for holding array element  26 . An Independent keeper  27  may be widely varied; for example, the shape may be a ring or a more complex form with a snug fitting interface substantially similar around seating recess ( 32  of  FIG. 9 ) such that array element  26  is substantially uniformly placed inside seating recess  32 . Furthermore, a metallic keeper  27  may remain exposed or be encapsulated within and around seating recess  32  with a polymer substantially similar to insulating body  20 , body  28 , or a combination of the two. 
         [0060]    As referenced by Cross (US patent 2006/0089692 A1), high tensile strength is required to enable non-stabilized cylindrical stimulator lead  12  to be reliably removed using a retrograde technique. Tensile strength is also relevant to lead  23  during the deployment of array element  26 . With reference to Kuzma (U.S. Pat. No. 7,891,085 B1) an option to fill and possibly bond (fuse) empty wire conduit lumens  18 , distal to the electrical wiring of stimulator electrode contacts  14 , contributes to the tensile modulus of non-stabilized cylindrical stimulator lead  12 . By way of inference but not limitation to lead  23 , said filling and possible bonding will provide additional surface area for bonding keepers  27 ( a /c) and will seal lead  23  if insulating body  20  is used for backstop  31 , as in keepers  27 ( b /d) or lead  23  with a integrally formed keeper  27 . 
         [0061]      FIG. 5  shows a perspective exploded view of lead  23  as taken from dissection line (C). The fundamentals of Insulating body  20  and stylet guide  15  represent prior art. Wire conduit lumens  18  are not shown within insulation body  20 . They may remain as open voids or can be filled and possibly bonded. Keeper  27 ( a ) is exemplified in the exploded view and array element  26  is shown separated from body  28 . In one embodiment of the invention, array element  26  can be individually formed from a medically implantable, non-resorbable, polymer such as, but not limited to, polyethylene, polyurethane or crossed-linked polyurethane. As an example, but not limitation, intrabody segment  34  of an independently formed array element  26  is embedded, by fusing or casting, within body  28 . In another embodiment, array element  26 , and body  28  can be concurrently formed if the polymer selected is substantially the same for array element  26  and body  28 . With inference to keeper  27 , the surface of array element  26  in direct contact with keeper  27  may be widely varied; for example, the surface may be smooth or include dents, slots, tabs or the like. These features allow array element  26  to be configured for secure storage juxtaposed to keeper  27 . 
         [0062]    As taken from dissection line (C),  FIG. 6  shows a perspective exploded view of partially assembled lead  23  depicting keeper type  27 ( a - d ) bonded to insulating body  20  and type specific bonded to stylet guide  15 . When compared to  FIG. 5 , intrabody segment  34  of array element  26  is contained within body  28  where it is embedded as a separate component or was concurrently formed with body  28 . 
         [0063]    In still a further embodiment of the invention, radiopaque (x-ray) markers  35 , which contrast radiolucent polymers, are likely to be integrated into, or formed around, a segment of array element  26 . A radiopaque marker(s)  35  located substantially near or at distal tip  36 , of body  28 , would also be an option, especially if a radiopacifying element, or alloy, is not utilized for keeper  27 . Radiopaque markers  35  provide fluoroscopic, x-ray, detection during percutaneous placement of lead  23  and deployment of array element  26 . If removal of lead  23  is necessary, radiopaque markers  35  will assist the practitioner with respect to the location and extraction progress of lead  23  and its retroflexed array element ( 26  of  FIG. 10 ) By way of example, polyurethane/Tungsten marker bands (Radiopaque Solutions Inc.) may be formed to array element  26  and/or a radiopacifying element, such as Tantalum, may be added to the monomer, prior to polymerization, of body  28  and/or array element  26 . 
         [0064]      FIG. 7  shows the embodiment of stabilizing array  24  in a perspective view as taken from dissecting line (C).  FIGS. 7A and 7B  depict array element  26  in deployed and stored positions respectively. In yet another embodiment of stabilizing array  24 , contours ( 37  of  FIGS. 5-10 ) are formed on body  28  which generally follows the form of array element  26  in stored and retroflexed positions. For example, the spacing between array element  26  and contours  37  is substantially similar around the entire periphery of body  28 , such that array element  26  is substantially uniformly stored, and retroflexed, abutting body  28 . During percutaneous positioning and retrograde removal, contours  37  allow folded and retroflexed array element  26  to assume a dimension no wider than any epidural segment of lead  23 . 
         [0065]    The embodiments of stabilizing array  24 , as discussed and illustrated in  FIGS. 5-7 , are substantially the same for the (variation) in stabilizing array  24 . Axial cutaway depictions ( FIGS. 8 and 9 ) highlight the internal differences between stabilizing array  24  and said (variation). 
         [0066]    Deploying lumen ( 38  of  FIGS. 8-10  and  12 ) is yet another embodiment of stabilizing array  24  and said (variation). Deploying lumen  38 , continuous with coaxial lumen  19 , accommodates the deploying segment, dissecting line (E), of deploying stylet  40  of  FIGS. 11-14 . Deploying lumen  38  generally originates at the level of backstop  31 , may be sized to be substantially equal to stylet guide  15 , has a length dependent on stabilizing array  24 , and said (variation), and may have a substantially flat or rounded luminal contact surface  41  such that the distal tip of deploying stylet  40  is substantially uniformly matched to luminal contact surface  41 . Sidewalls  39 , surrounding deploying lumen  38 , may have an embedded wire wound feature (not shown) generally originating and terminating at backstop  31  and luminal contact surface  41  respectively. 
         [0067]      FIG. 8  details the embodiment of stabilizing array  24  in a perspective axial cutaway representation, as taken from dissection line (C). Distal electrode contact  25  is not shown as it is not integral with the depicted independent keeper  27 ( a ). Stylet guide  15  is specific to manufacturing and, for illustrative purposes, is shown as a coiled wire feature. To provide detail, one side of keeper  27 ( a ) is shown elevated out of the axial cutaway depiction of  FIG. 8A . In the illustrated embodiment, deploying lumen  38  terminates at luminal contact surface  41 ( a ) which is contiguous with contoured deploying surface  42 . Juxtaposed to contoured deploying surface  42  is deploying contact surface  43  of the curvilinear shaped array element  26 . By way of example but not limitation, the embodiment of stabilizing array  24  depicts relief contour  44  distal to, and substantially mirroring, contoured deploying surface  42 . As seen in  FIG. 8B , relief contour  44  accommodates the deflection of array element  26  forward progresses during packing (storage) and deployment. 
         [0068]      FIG. 9  details the (variation) in stabilizing array  24  in a perspective axial cutaway representation, as taken from dissection line (C). Keeper  27 ( c ), integral with distal electrode contact  25 , is shown partially elevated out of the axial cutaway illustration. The (variation) in stabilizing array  24 , which utilizes a substantially rectilinear deployed array element  26 , has deploying lumen  38  terminating at luminal contact surface  41 ( b ); notably isolated from the deployable surfaces of array element  26 . 
         [0069]    Another purpose of this invention is to provide a safe means of lead removal in the event of lead failure, infection or medical and/or patient necessity. An intact, non-stabilized cylindrical lead  12  can be removed by a retrograde technique (prior art). In yet another embodiment of the invention, deployed array element  26  has the ability to fold back on itself (retroflex). Retroflexing of array element  26  upholds the practice of retrograde removal for lead  23 . 
         [0070]    Illustrating retroflexed array elements  26 :  FIGS. 10A and 10B , perspective views as taken from dissection line (C), show stabilizing array  24 , and said (variation), in whole and axial cutaway depictions respectively.  FIG. 10B  depicts keeper  27 ( c ) which is integral with the distal electrode contact  25 . As previously noted, contours  37  allow array element  26  to achieve a stored and retroflexed dimension no wider than any epidural segment of lead  23 . Additionally, the polymer selected for array element  26  may require an intrinsic perforation, thinning or retroflexing relief cut  45  to achieve an optimal retroflexed dimension for retrograde extraction of lead  23 . 
         [0071]    The method (prior art) of percutaneously implanting non-stabilized cylindrical lead  12  is well documented. Except for the unique deployment of array element  26 , the basic implantation steps of non-stabilized lead  12  apply to lead  23 . Those basic steps involved with implanting lead  23  (within the epidural space  103 ) as well as the unique step of deploying array element  26  will now be discussed in further detail. 
         [0072]    The practitioner identifies the vertebral level to be entered for percutaneous placement of lead(s)  23 . Using sterile technique a percutaneous introducer needle i.e. Tuohy or Hustead ( 108  of  FIG. 2A ), is inserted using a paramedian or midline approach. With tactile feedback and possible fluoroscopic or ultrasonic assistance, the introducer needle  108  is advanced through the supraspinous ligament  100  and into the intraspinous ligament  101  for a midline approach to the epidural space  103  or to the lamina  116  for a paramedian approach to the epidural space  103 . The introducer needle stylet  110  is removed, which prevents coring of soft tissue, and the introducer needle tip  111  is advanced into the epidural space  103  through the ligamentum flavum  102  using the traditional loss of resistance technique with air or sterile saline. The introducer needle  108  can be rotated so that needle tip  111 , with its beveled cutting surface, aims in the direction of catheter advancement, i.e. cephalad, prior to, or after, the advancement of the introducer needle  108  into the epidural space  103 . Using fluoroscopic guidance, lead  23  is inserted through the lumen of the introducer needle  108  and advanced to the targeted stimulation site within the epidural space  103 . Guiding stylet  16 , introduced into proximal originating coaxial lumen  19 , may be required to stiffen and steer lead  23  to obtain final positioning of electrode array  13 . Assessment of electronic integrity, which confirms continuity of electrode array  13 , electrical conductor wires  17  and wired contacts  22 , is commonly preformed when lead  23  is at, or near, its final location within the epidural space  103 . A practitioner&#39;s preference determines if intra-operative stimulation testing, using a non-implantable pulse generator (not shown), is preformed in a responsive (awake) patient. Such testing optimizes initial stimulator performance and offers the chance of fine tuning electrode array  13  positioning over the targeted dorsal column  117  of the spinal cord  107 . Using fluoroscopic guidance, guiding stylet  16  is carefully removed from coaxial lumen  19  to prevent movement of the epidurally implanted segment of lead  23 . 
         [0073]    For clarification, guiding stylet  16 , comprised of a wire sized to fit within the proximally originating coaxial lumen  19 , is shorter than deploying stylet  40  and will not enter deploying lumen  38 . 
         [0074]    By way of example but not limitation, deploying stylet  40  may be of similar material and sized to be substantially equal to the width (gauge) of guiding stylet  16 . Furthermore, a step-down radius in the deployment section of deploying stylet  40  may be necessary to prevent binding of said stylet with sidewalls ( 39  of  FIGS. 8 ,  9  and  12 ) of deploying lumen  38 . The distal tip of deploying stylet  40  may have a substantially flat or rounded distal tip which is substantially uniformly matched to luminal contact surface  41 . The lengths of deploying stylet  40  are, to some extent, dependent on stabilizing array  24  and said (variation). 
         [0075]    Deployment of array element  26  occurs after fluoroscopic assisted final positioning of lead  23  and possible electrode array  13  stimulation testing in a responsive patient. Deployment of array element  26  is done with either stylet ( 46  of  FIG. 11A ) or deploying handpiece ( 49  of  FIGS. 13 and 14A ). The embodiments and deployment methods of each will now be illustrated and discussed in detail. 
         [0076]      FIGS. 11A and 11B  depict the embodiment of stylet  46  and a proximal segment of lead  23 , as taken across dissection line (D), respectively. Control stop  48  on deploying stylet body  47 , which may be molded plastic, contacts proximal tip  21  of lead  23  thereby preventing the deploying segment of deploying stylet  40  from displacing stabilizing array  24 , and said (variation), any further than necessary to deploy array element  26 . Stylet  46  must be clearly identified to prevent its use during percutaneous guiding and final positioning of lead  23 . 
         [0077]    There exists a potential for inductive movement of electrode array  13 , possibly away from the targeted stimulation site, during the deployment of array element  26  when using stylet  46 . Inductive movement is attenuated by countertraction between the extra-epidural segment of lead  23  and deploying stylet body  47  of stylet  46 . 
         [0078]    With final epidural positioning of lead  23  complete and fluoroscopic guidance present, deployment of array element  26  using stylet  46  is accomplished in the following sequence: deploying stylet  40  is advanced through proximally originating coaxial lumen  19 ; prior to deployment, countertraction is established and maintained as deploying stylet  40  is advanced into deploying lumen  38 ; deployment of array element  26  initiates as the distal tip of deploying stylet  40  seats to luminal contact surface ( 41 ( a /b) of  FIGS. 8A and 9 ); continued advancement of deploying stylet  40  elastically elongates body ( 28  of  FIG. 6 ) and displaces the retained tips of array element  26  from keeper  27 ; deployment of array element  26  concludes when control stop  48  contacts proximal tip  21  of lead  23  whereby array element  26  assumes its permanent (intrinsic) deployed shape. 
         [0079]    To reduce tensile stress on lead  23 , deploying stylet  40  is carefully pulled away from deploying lumen ( 38  of  FIG. 12C ) and positioned within the epidurally implanted segment of lead  23 . As noted below, removal of deploying stylet  40  occurs after fluoroscopic verification of array element  26  deployment, rotational alignment and extraction of the percutaneous introducer needle  108 . 
         [0080]    The present invention relates, in yet another embodiment, to deploying handpiece  49  comprised primarily of: a handpiece  50 ; a deploying stylet  40 ; a plunger  62 ; and a safety tab  64 . The embodiment of deploying handpiece  49 , as illustrated in  FIGS. 13 and 14A , will now be described in more detail. 
         [0081]    A proximal segment of lead  23 , which may included all wired contacts  22 , is secured by deploying handpiece  49  and eliminates the manual countertraction necessary on the extra-epidural segment of lead  23  during deployment of array element  26 . Deploying handpiece  49  incorporates deploying stylet  40  on to plunger  62  rather than deploying stylet body ( 47  of  FIG. 11A ). Deploying handpiece  49  is intended for the deployment of array element  26 . While not a replacement for guiding stylet  16 , lead  23  can be guided within the epidural space  103  using deploying handpiece  49  with safety tab  64  secured to plunger  62 . 
         [0082]      FIG. 13A  is a perspective view of deploying handpiece  49 . Safety tab  64  is shown clipped to plunger ( 62  of  FIG. 14 ). A proximal segment of lead  23 , as taken from dissection line (D), is depicted in retention feature  51 . Projecting beyond dissection line (D), a segment of deploying stylet  40  is shown within the proximally originating coaxial lumen  19 . 
         [0083]      FIG. 13B  details plastic safety tab  64  with integral locking clips  65 . Locking clips  65  maintain non-deployable distance  66  between plunger finger rest  63  and cylindrical end  56  of handpiece  50 . Non-deployable distance  66  prevents deploying stylet  40  from entering deploying lumen  38 . Furthermore, locking clips  65  securely fasten safety tab  64  to plunger  62 . Removal of safety tab  64  can only happen with a pulling and/or twisting action. 
         [0084]      FIG. 14A  is a top view of deploying handpiece  49 . As a reference,  FIG. 14B  depicts a proximal segment of lead  23  as taken across dissection line (D).  FIG. 14A  shows the embodiment of handpiece  50  in a dashed hidden line format to illustrate its internal structure. The embodiment of handpiece  50 , which may be molded plastic, is somewhat wing like and comprises: a retention feature  51 ; a recess  52 ; a tapered relief  53 ; a cavity  54 ; a seating surface  55 ; a cylindrical end  56 ; a cylindrical opening  57  for plunger  62 ; a cylinder  58 ; a cylinder floor  59 ; a stylet passage way  60 ; and opposing tabs  61 . Of course, this is not a limitation. For example; handpiece  50  may have a more complex shape and/or include such additions as finger seats to aid in the downward displacement of plunger  62  and/or a stylet passageway  60  with a wire wound element substantially similar to stylet guide  15  of non-stabilized lead  12  or lead  23 . Retention feature  51  is formed to match the outer shape of lead  23  with an interface configured for a snug fit. Retention feature  51  can be widely varied; it may, for example, include slots, tabs, snaps or the like. Stylet passageway  60  links cylinder floor  59  to seating surface  55 . As an example, but not limitation, the diameter of stylet passageway  60  is generally comparable to coaxial lumen  19  of lead  23 . This prevents bending and possible failure of deploying stylet  40  during deployment of array element  26 . Plunger  62 , integral with deploying stylet  40 , may contain flat o-ring  67  which provides a smooth gliding surface between plunger  62  and cylinder  58 . 
         [0085]    By way of example, and with deploying handpiece  49  fully assembled, safety tab  64  attached to plunger  62 , and fluoroscopic guidance present, the loading of a proximal segment of lead  23  into deploying handpiece  49  takes place in the following sequence: deploying stylet  40  is advanced through proximally originating coaxial lumen  19 ; tapered relief  53  allows proximal tip  21  to be angled and inserted into cavity  54  where it is mated to seating surface  55 ; retention feature  51  is opened by a flexing action of tabs  61 ; recess  52 , shown generally gaping retention feature  51 , allows lead  23  to be finger pressed (seated) into retention feature  51 ; after confirming that proximal tip  21  is mated to seating surface  55 , tabs  61  are released trapping a proximal segment of lead  23 . Failure to seat proximal tip  21  to seating surface  55  may result in a null deployment of array element  26 . 
         [0086]    With a proximal segment of lead  23  loaded into deploying handpiece  49 , and final epidural positioning of lead  23  complete, deployment of array element  26  for stabilizing array  24  and said (variation) is accomplished by removing safety tab  64  and pressing plunger finger rest  63  until plunger  62  bottoms out on cylinder floor  59 . The action of pressing said plunger seats stylet  40  to luminal contact surface ( 41 ( a /b) of  FIGS. 8A and 9 ) elastically elongates body ( 28  of  FIG. 6 ) and displaces the retained tips of array element  26  from keeper  27 . Bottoming out also prevents the deploying segment of deploying stylet  40  from displacing stabilizing array  24  and said (variation) any further than necessary to deploy array element  26  to its permanent (intrinsic) shape. 
         [0087]    To reduce tensile stress on lead  23 , deploying stylet  40  is carefully pulled away from deploying lumen ( 38  of  FIG. 12C ) and positioned within the epidurally implanted segment of lead  23 . 
         [0088]    Verification of array element  26  deployment and its rotational alignment within the epidural space  103  is confirmed by the fluoroscopic positional relationship of radiopaque markers  35  on array element  26  to the cylindrical portion of lead  23  with its radio-dense electrode array  13 , optional distal tip  36  radiopaque marker(s)  35  and contrasting radiolucent polymer insulating body  20 . A correctly positioned stabilizing array  24 , and said (variation), will image with the bilateral radiopaque markers  35  of array element  26  extended and substantially perpendicular to the longitudinal axis of lead  23  as viewed from an anterior/posterior fluoroscopic image. As previously noted, the epidural space  103  is a potential space with major borders consisting of dural sac  112 , ligamentum flavum  102 , and the vertebral pedicals  115  and laminas  116 . As the array element is deployed it will follow the path of least resistance and will rotate away from the borders of the epidural space  103 . If necessary, the extra-epidural segment of lead  23 , generally at the level of the introducer needle hub  109 , can be carefully twisted until the acquired image of two radiopaque markers  35  of array element  26  are obtained. 
         [0089]    After confirmed deployment of array element  26 , removal of the retained proximal segment of lead  23  from deploying handpiece  49  is accomplished by a flexing action of tabs  61  allowing lead  23  to be angled and carefully pulled free of retention feature  51  and cavity  54 . 
         [0090]    The prior art of: removing the introducer needle  108  and guiding stylet  16  (with inference to deploying stylet  40 ); anchoring the extra-epidural segment of non-stabilized lead  12  as it emerges from the epidural space  103 ; adding possible lead extensions; soft tissue tunneling of said lead and/or lead extensions to the implantable pulse generator  11  implant site; establishing electronic connections, testing and initial programming of said lead and pulse generator; implantation of said pulse generator; and surgical closures of anchoring and implant sites—are relevant and generally apply to lead  23 . 
         [0091]    To elucidate the prior art of introducer needle  108  and guiding stylet  16  removal as it applies to lead  23  and deploying stylet  40  the following sequence is performed: the extra-epidural anchoring and tunneling site is surgically prepared; fluoroscopy is used to visualize deploying stylet  40  and the positional stability of electrode array  13  during deploying stylet  40  removal and extraction of the introducer needle  108 ; deploying stylet  40  is partially withdrawn—locating its distal tip generally at the beveled tip  111  of the introducer needle  108 ; to attenuate movement of the epidurally implanted segment of lead  23 , minimal traction is used to remove the introducer needle  108  from surrounding tissue and the remainder of deploying stylet  40  is carefully removed from coaxial lumen  19 . 
         [0092]    While the invention has been described in terms of several preferred embodiments, numerous alterations, permutations and equivalents could be made thereto by those skilled in the art without departing from the scope of the invention. It is therefore intended that the following claims be interpreted as including all such alterations, permutations and equivalents as fall within the true spirit and scope of the present invention.