Patent Publication Number: US-2021187308-A1

Title: Apparatus and Device for the Electrical Interconnect of Implantable Devices

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Nonprovisional Application claims priority to U.S. Provisional Patent Application No. 62/952,425 filed Dec. 22, 2019. 
    
    
     FIELD OF THE INVENTION 
     The present invention includes an apparatus, method and system of use that is directed to a low insertion force, securedly fixed and highly robust electrical and mechanical connection for an implantable medical device, generally. Said invention offers a rectangular, individualized coil-spring support structure exhibiting a high density, electrically isolated connection configuration capable of supplying and receiving electrical impulses via discrete lead electrodes providing a compact, modular construction. 
     BACKGROUND 
     Implantable electronic stimulation generators or implantable impulse generators (IPGs) consist of a class of devices exhibiting a means to provide stimulation to certain excitable tissues in the human body. These generators may be implanted into various locations about the body in order to supply electrical impulses to receptive muscles and tissues for excitation and regulation including pain modulation, nerve control (e.g. vagus nerve) and stimulation of varied end organs (including the heart, bladder and brain). Further, these same leads can be utilized to receive, monitor and record information (e.g. electric patterns in seizures and deep brain stimulation) which is an opposite yet reciprocal use of transmission in these leads. 
     The current devices used in electrical stimulation utilize a physical interface which provides an electrical connectivity to implanted electrodes, via stimulation leads, to electricity producing implantable pulse generators. This configuration commonly incorporates a welded “canted coil” placed within a metallic housing and/or a set screw block containing a cylindrical through hole and perpendicular threaded cavity containing a set screw. Specifically, a “canted coil” is a series of wire loops, similar to the loops of a compression spring, that have been flattened in one plane whereby this “flattened coil” is then secured within a cylinder. Disposed at a pre-selected angle, with respect to the centerline, the coil&#39;s ends are typically welded together, and the cylinder may then be removed. Moreover, this “canted coil” is normally confined within a defined, typically encapsulating toroidal housing or similar enclosure, whereby said compression spring is halted from expanding past a certain outward radial demarcated confine. 
     Once the cylindrical stimulation lead (exhibiting discrete contact rings about its proximal end) is inserted into and through the center of its respective welded “canted coil” spring (i.e. generator electrical contact), the coil is pressed (expanded radially outward via the force created by the contact ring) and is flattened into a cylindrical metallic housing thus creating an electrical connection between the stimulation (or recording) lead contact ring and the impulse generator via said metallic housing. An attached wire, onto a metallic housing, or into a non-metallic housing, completes the implantable pulse generator&#39;s electronic circuit, whereby the lead body is inserted within one to a plurality of receiving connectors in a terminal (implanted) position and the lead body is transfixed through a securing set screw block and held stationary by advancing the set screw onto the lead body. 
     The set screw block and set screw mechanism is primarily intended to retain the (1) stimulation, (2) recording and/or (3) data transmission lead by the implantable pulse generator but may also provide an electrical interconnect via a wire attached to the set screw block and the implantable pulse generator electronic circuit. 
     In order to provide long term electrical connection in a fluid filled environment, i.e. the human body, small silastic seals are placed in between each connector, canted coil and/or set screw block to provide a high impedance electrical barrier once the stimulation leads have been fully inserted and secured. 
     The current welded “canted coil” technology can only provide a minimum of 0.100″ (2.5 mm) center to center interconnect spacing which proves a space utilization defining and limiting aspect wherein limiting space for lead connectors (a) limits the number of connections (and ultimately electrodes) and (b) increases the space required for each additional electrode (thereby increasing the IPG device size). 
     It is the stated goal of inventor to remedy the historic intractable issues of untenable connector size (i.e., density infirmities in terms of shear connector size) and limited and stymied electrode/connector expansion capabilities (wherein only a set number of connectors may be serviced by one generator). As well it is a goal of inventor to provide for a rectangular, singularized, ergonomic, non-encapsulated, non-confined (open) coil spring “lattice structure” that is (1) a simplistic unibody design which is (2) demonstrably more compact (3) more easily modularized and (4) more readily lending itself to spring repair and/or replacement (via unencumbered access) which lends itself readily to not only ease of manufacture, production and replication (via 3-d printing, additive manufacturing or other like means) but also stratification (stacking), extension and infinite expansion wherein expanded numbers of lead connectors may be provided per lead in less space providing, ultimately and practically, more electrodes from a larger number of leads emanating from a smaller generator device. Moreover, the rectangular frame and resulting design of the present invention more readily lends itself to correct connector orientation when being inserted into an accepting device (as opposed to a circular housing that is mutable into any number of different, and potentially non-functional, arrangements and positions). Too, it is this directed design choice by inventor as to better support and situate each coil spring into its respective proper placement for accepting said lead&#39;s (connector ring exhibiting) proximal end. 
     Although strides have been made to address the need for an impulse generator and receiving lead exhibiting a low insertion force electrical connector with adequate simplicity and requisite compact size to accommodate the need for an increasing number of implanted electrodes from a single, compact device, considerable shortcomings remain. It is therefore desirable to provide an impulse generating and conveying device configured to support an increasingly desired multiplicity of electrodes through high density, serial placement while also recognizing the need for controlling device size. It is the present invention, method and system of use that meets these requirements. 
     BRIEF SUMMARY OF THE INVENTION 
     The present disclosure provides an apparatus, method and system of use that discloses an electrical, mechanical connection between an impulse receiving or generating device and implantable connector(s) of an electrical impulse receiving and conveying lead via a low-force, side-loading of one or more secured compression springs ideally held in place in a metallic, 3-D printed uni-body housing. 
     As disclosed within the present specification and accompanying drawings, the lattice structure (connector housing), which is in the form of a rectangular frame or skeleton for the inclusion and support of parallel, axially co-planar spring coils, may be constructed of a metallic, semi-metallic or non-metallic material which is particularly amendable to a 3D printing process (e.g. Binder Jetting or Laser Sintering), casting, extrusion, injection molding or a similar (or combination of similar) processes whereby a single, uni-body coil spring frame is generated. Yet, where, as here, precision is an absolute requirement, 3-D printing provides the greatest degree of requisite reproducible accuracy. 
     Indeed, 3D printing (i.e. additive manufacturing) processes and similar processes are particularly well suited to the present invention in that these processes can create physical features that otherwise cannot be easily created with conventional machining processes or metal injection molding. Equally, by simplifying the design and construction of the present frame and lattice structure to a unibody design, as opposed to a multi-component and encapsulating housing, the present design finds itself particularly amendable to 3D printing processes to accomplish desired compactness and, most vital, appropriate connector&#39;s exacting precision and requisite density. 
     It is also within the contemplation of inventor that each 3D printing process may use fine metal partials to create a solid or semi-solid metal structure (framed housing) through which an electrical current may be supplied, via incorporated coil springs, to a lead connector and, finally, a discretely defined electrode or another pulse generating or receiving device. Yet, it is within inventor&#39;s preview to provide for a frame that is semi-metallic or dielectric. 
     The stimulation, recording or data transmission lead ring connector, the operable portion of the present invention, itself is a largely rectangular frame constructed to evidence a hollow-centered, structural support, typically, to a series of 2 coil springs—largely in parallel relation to one another—which are made to receive and run perpendicular to an inserted and received lead&#39;s outwardly displayed circular ring connectors. Each of these coil springs lies securedly coplanar within said frame, much in the same orientation as a vertical window grille, and each consists of a cylindrical axis which is perpendicular to the cylindrical axis of the stimulation lead (running coaxial to the axis of the hollow center of the aforementioned rectangular frame housing). These two or more compression spring(s) is/are positioned equal distance from one another and substantially equidistant to the centerline axis of the frame housing wherein the center axis of the frame housing runs coextensive with the cylindrical axis of the stimulation lead. Each of the largely parallel coil springs, being cylindrical in nature, themselves exhibit axes that run in the same axial plane with the frame when inserted into said frame housing. 
     The frame itself exhibits protrusions above and below the centrally deposed hollow core of said frame whereas each protrusion acts as (1) a semi-circular, convex receiving guide for the concave, tubular inserted lead and (2) as a support to separate each coil spring. On either side of each protrusion lay either depressions, posts or a combination thereof (depressions with inserted posts) with which to hold and secure each coil spring and to support said coils at rest and during radial outward movement (upon lead insertion). In one embodiment said depressions themselves are sufficient to hold and secure said coil springs wherein the coil springs diameter is less than the thickness of the securing frame (i.e. in the thicker framed invention). In another embodiment, said posts are supported laterally on each end wherein the coil spring is “sandwiched” between a centrally deposed protrusion and an outwardly deposed shelf wherein said coil springs diameters may be less than, equal to or more than the thickness of the frame (e.g. in a thinner framed invention). Additionally, if each coil spring were bifurcated longitudinally at is midpoint, each coil spring may be seen to be provided open space both within the centrally deposed hollow core of the frame, for acceptance of lead insertion, and on corresponding, opposite right and left sides of each coil spring (away from the hollow center) for spring coil expansion (radially) thus providing outward relief required from lead insertion where said housing will provide physical clearance for the side loading deformation and outward V-shape (i.e. visually a “&lt;” and “&gt;” shape). 
     Functionally, the mating of the (male) stimulation lead and the (female) hollow core of the connector frame, radially influences the compression spring(s) of the connector, deforming the linear cylindrical axis of the compression spring away from the inserted lead resulting in large radii or a V-shape (i.e. visually a “&lt;” and “&gt;” shape), from the center of the coil spring, wherein the V-shape has roughly equal distance on either side of the V-shape vertex as the coil springs expand outward, radially, as to both accommodate and receive the outer diameter of said leads diameter and correspondingly rounded connector. Namely, one discrete coil-spring connector mates to exactly one reciprocal rounded connector in series wherein connectors are positioned linearly one behind the next whereby an inserted lead traverses the hollow core of each subsequent connector. The coil spring assisted housing will thus hold the compression spring(s) as the stimulation lead is inserted through the center axis of the housing causing the compression spring to deform outwardly and capture or “grip” each connector ring. This connection, in turn, supplies energy to exactly one pathway which is terminally connected to exactly one implanted electrode, medical device or distal terminal contact. The creation of each distinct pathway to a designated position on a nerve or tissue, represents a singular track which is repeated for each ‘connector-lead-electrode’ pathway where the number of discrete pathways is regulated by the density of connectors available to make to said lead/electrode associations. Each connector may also be separated and insulated from the next adjacent connector by a dielectric separator/insulator. 
     The width of the housing to range from 0.020 inch to 0.060 inch, 0.25 mm to 1.5 mm, depending on physical requirements and number of connections sought. The width and spring orientation represents the distance parallel to or in-line with the housing center axis and designation of depression, post (boss) or depression-post configurations. 
     The compression spring coil diameter ranges from 0.013 inch to 0.060 inch, 0.3 mm to 1.5 mm, yet may include a variable or varying coil diameter wherein some embodiments may include a uniform diameter and other embodiments may include alternating diameters within the same coil spring. For example, the central midpoint of a coil spring (dissected longitudinally), at an area corresponding with the frame&#39;s hollow center, may exhibit a coil spring diameter (involving one to a plurality of individual spring coils) that is smaller than its abutting coil spring sections as to better accept and “grip” an inserted lead. This is equally true of coil pitch or angle, although, as in the case of a canted coil, this is but one a series of possible modifications. 
     Too, compression spring wire cross section geometry is not relegated to a cylindrical form but can be round, square, rectangle, round with a flat, oblong or any other conceivable cross-sectional geometry or any combination thereof. 
     And, each coil could, as well, use one to a number of these modifications even within and on the same coil as necessity dictates. 
     In terms of position, the compression spring coil distance from the housing center axis to range from 0.000 inch to 0.040 inch, 0 mm to 1 mm. The compression spring can be assembled into the metallic housing in a free state, loosely attached or floating within the frame and housing constraints, uncompressed or even slightly, moderately or heavily compressed. 
     In addition to the housing containing full depressions, or partial depressions to capture one or more compression springs from falling out or being dislodged while the stimulation lead is being axially inserted through the housing center axis, the housing could also incorporate posts, or bosses, positioned to insert into the center end of each compression spring, within a depression or alone, in one end or both ends of the compression spring. It may be that the spring has a uniform means of securing each of its ends or, alternatively, differing means of securing and/or compressing said spring on either end (depression, posts, a combination of depressions and posts or any combination thereof). 
     Too, the device itself contains novel features wherein the aforementioned connector width and resulting ability to provide an increased number of connections translates into the potential for multiple lead connectors per device which may be stacked (with an upper and lower lead insertion points as shown in  FIGS. 1-3 ), conglomerated and/or located in various conformations and configurations all in one device. And, whereas depicted herein, stacking manifestly doubles the capacity of a pulse generating or monitoring device, this is merely representative and is not intended to limit the number and position of connectors—which could be exponentially arranged and rearranged—given the current potential for connector expansion, the number of connectors a device may support, the decreased space required, increased capacity for modular expansion as well as resultant decreases in device size requirements. 
     In terms of the functional components of the generating and monitoring device, the present invention exhibits additional key features aiding in its operation including, set screw securing blocks and seals. The former set screws securing blocks and screws work to secure inserted leads providing a mechanism for reversibly securing inserted leads into said device. The later insulating seals provide two proportionately advantageous elements to the present device wherein said seals allow for (a) proper connector placement and securing and (b) an insular barrier between connectors which serve to ensure the discrete conveyance or reception of signals without fear of interference from an adjacent connector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Novel features characteristics of the application are set forth in the appended claims. However, the application itself, as well as a preferred mode of use, and further objectives and advantages thereof, will best be understood by referencing the following detailed description when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1 . shows an isometric view of the front side of a 32-channel implantable medical device and leads. 
         FIG. 2 . illustrates an isometric view of the back side of a 32-channel implantable medical device and leads. 
         FIG. 3  displays an isometric exploded view of the back side of a 32-channel implantable medical device and leads of  FIG. 2 . 
         FIG. 4 a    shows an top view of the of a 32-channel implantable medical device and leads wherein the top half of the connector assembly has been sectioned to show the internal components and certain sections have been enlarged to show detail. 
         FIG. 4 b    exhibits a lead axis and perpendicular orientation of lead connectors in series. 
         FIG. 5 a    is an isometric view of the “thick” rectangular dual spring side loading connector assembly utilizing securing depressions and/or posts. 
         FIG. 5 b    depicts an isometric view of the “thin” rectangular dual spring side loading connector assembly utilizing securing posts. 
         FIG. 6 a    shows the orthographic view of a “thick” rectangular dual spring side loading connector assembly with inserted coil spring. 
         FIG. 6 b    shows the orthographic view of a “thin” rectangular dual spring side loading connector assembly with inserted coil spring. 
         FIG. 7 . shows the orthographic and isometric views of the dual spring side loading housing without an inserted coil spring. 
         FIG. 8  ( 9 ) shows the isometric views of the 16 channel neurostimulation lead and the dual side loading connector assembly, before engagement, spring coils largely parallel, and after engagement, spring coils deformed radially outward. 
         FIG. 10  exhibits coil springs of varying diameters as to better accommodate lead insertion. 
     
    
    
     And while the device, system and method of use of the present application is susceptible to various modifications and alternative forms, specific embodiments included herewith have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description, describing specific embodiments, is not intended to limit the application to the particular embodiment disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present application as defined by the appended claims read in context of the disclosure. 
     DETAILED DESCRIPTION AND BEST MODE OF IMPLEMENTATION 
     Illustrative embodiments of preferred embodiment are described below and depicted in the figures. It must be appreciated that in the development of any preferred embodiments, numerous references are made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices depicted in the appended drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, and apparatuses described herein may be positioned in any desired orientation which addresses the above deficiencies of the prior art. Thus, the use of terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components (e.g. lead connectors, lead electrodes, impulse generating devices, coil springs and the like) should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, whereas the device described herein may be oriented as to provide an ergonomic, rectangular and compact uni-body lead connector construct that is designed explicitly for low-force lead insertion, high-density and compacted arrangements providing for increased connector capacity, enhanced modulation and connector expansion leading to a smaller impulse generator device footprint. 
     The present invention will be understood by those having skill in the art, both as to its structure and operation, taken in conjunction with the accompanying description and drawings. It should be understood that various components, parts, and features of the different embodiments may be combined together and/or interchanged with one another, all of which are within the scope of the present application, even though not all variations and particular embodiments are shown in the drawings. It should also be understood that the mixing and matching of features, elements, and/or functions between various embodiments is expressly contemplated herein so that one of ordinary skill in the art would appreciate from this disclosure that the features, elements, and/or functions of one embodiment may be incorporated into another embodiment as appropriate. 
     Referring to  FIG. 1 ,  FIG. 1  illustrates a medical implant device  10  consisting of an electrical interconnect system  12 , consisting of internalized implantable pulse generator electronics  15  and two 16-channel stimulation/recording leads  20  (evidenced as  20   a  and  20   b ).  FIG. 1  exhibits upper and lower stimulation/recording leads  20   a  and  20   b  which are held securedly within electrical interconnect system  12  through insertion of set screws  60  through upper and lower apertures  62   a  and  62   b  of externally residing set screw guide  62 . 
       FIG. 2  provides for a reverse view of  FIG. 1  wherein upper stimulation/recording lead  20   a  and lower stimulation/recording lead  20   b  are seen to pass through set screw block  70   a  and  70   b , respectively, and into electrical interconnect system  12 . 
       FIG. 3 , shows an exploded view of  FIG. 2 , displays two 16-channel stimulation/recording leads  20   a  and  20   b , a truncated set of stimulation electrodes  25   a  and  25   b , set screw bands  30   a  and  30   b , interconnect bands  40   a  and  40   b , which are inserted into electrical interconnect system  12 , connector housing  50 , secured by set screws  60   a  and  60   b  and set screw blocks  70   a  and  70   b , through each side load spring contact assembly  100 , which corresponds to exactly one feedthrough wire  120  and into the internalized portion implantable pulse generator electronics  15 . And while each side load spring contact assembly  100  may be seen removed from the connector housing  50  in  FIG. 3  in the exploded view, it is to be understood that each side load spring contact assembly  100  is placed and secured into designated receiving slots, above and below, wherein contact connector rings  25   a  and  25   b  reside on lead  20   a  and  20   b . It may be noted that the distal end of recording and stimulation lead  20   a ,  20   b  may as well be another medical stimulation or recording device. 
       FIG. 4 a    illustrates a top view neurostimulation system  10  and  FIG. 4 b    a side view showing medical implant device  10  and a 32-channel neurostimulation system with two 16-channel stimulation/recording leads  20  inserted and held in place by the tightening of the sets screw  60  and set screw block  70  against a set screw band. 
     Referring to  FIG. 4 a   ,  FIG. 4 a    displays a (a) top view, and two exploded views: (b) top left set screw sectional view and (c) bottom right connector/lead sectional view showing a neurostimulation system  10  encompassing two 16-channel stimulation/recording leads,  20   a  visible and  20   b  beneath  20   a , whose insertion causes each side load spring contact  140  to deform in an outward manner as a mechanical and electrical connection is created between an interconnect band  40   a , corresponding to the 16-channel stimulation/recording lead  20   a , and interconnect band  40   b , corresponding to the 16-channel stimulation/recording lead  20   b , whereby the implantable pulse generator electronic system  15  supplies and receives impulses via attached feedthrough wires  120  (see  FIG. 3 ) into receiving slots  55 . Receiving slots  55  evidencing an upper and lower set of connectors  100  (see  FIG. 4 b    below) and insulator seals  131  placed between spring contacts  100 . 
     Referring to  FIG. 4 b   ,  FIG. 4 b    depicts a side detailed view showing 2 leads  20   a ,  20   b  of a 32-channel neurostimulation system  10  with two 16-channel stimulation/recording leads  20  inserted through screw set  70   a  and  70   b , respectfully and through individual hollow cores  170  of connectors  100  along axis  220 .  FIG. 4 b    additionally shows insulator seal  131  placed between spring contacts  100  (See as well  FIG. 3 ) of receiving slots  55  in a largely connector  100 -seal  131 -connector  100 -seal  131  configuration. Insulator seal  131  creates a high impendence electrical path between spring contacts  140  and set screw block  70  (also shown in top left of  FIG. 4 a   ). The insulator seal  131  is an integral part of the connector housing&#39;s interior  80  or may be a separate component assembled into connector housing  12 . The width of seal  131  can range from 0.050 inch (1.27 mm) to 0.005 inch (0.127 mm). The spacing between spring contact  140  to spring contact  140  can range from 0.050 inch (1.27 mm) to 0.005 inch (0.127 mm). The spacing between spring contact  140  to set screw back  70  can range from 0.050 inch (1.27 mm) to 0.005 inch (0.127 mm). Seal  131  is a compliant or flexible material such as silicone rubber, urethane or a combination of other flexible materials. 
     Referring now to  FIGS. 5 a , 5 b , 6 a  and 6 b   , two possible versions of the side load spring contact assembly  110  is exhibited where the side load spring contact  140  captured by the housing frame  130   a  is held and secured by depressions  132  and  133  (which may also harbor securing posts  132  and  133 ) and  130   b  shows coil spring  140  held and secured by posts  139  and  139 . The center axis  180   a  through the hollow core  170  of housing frame  130   a  in  FIG. 5 a    represents the ultimate receptacle of the cylindrical axis  220  (see  FIG. 4 ), running coaxially, of the 16-channel stimulation/recording lead  20 . The center axis  180   b  through the hollow core  170  of housing frame  130   b  in  FIG. 5 b    represents the ultimate receptacle of the cylindrical axis  220  (see  FIG. 4 ), running coaxially, of the 16-channel stimulation/recording lead  20 . 
     Referring now to  FIG. 6 a    and  FIG. 6 b   , a side, top and sectional view show the two possible versions of  FIGS. 5 a    (thick  130   a ) and  5   b  (thin  130   b ) where  FIG. 6 a    exhibits housing frame  130   a  harboring depressions  132  and  133  and posts  136  and  137  and  FIG. 6 b    exhibits posts  138  and  139 . The thickness ( 130   a ) or thinness ( 130   b ) of the side load spring contact  140  and the housing frame  130  is illustrated by  160   a  and  160   b  at the bottom figures of  FIG. 6 a    and  FIG. 6 b   , wherein this width  160   b  of connector  130   b  may range from 0.013 inch to 0.060 inch (0.3 mm to 1.5 mm). The distance of the side load spring contact  140  from the center axis  180   a  and  180   b  is illustrated by distance  150 , wherein this distance may range from 0.000 inch to 0.040 inch (0 mm to 1 mm). 
     Further evidenced are side recess spaces  155  allowing for coil spring  140  movement outward and radially into said recess space  155  (as further depicted in  FIGS. 8 and 9  upon insertion of lead  20 ) as well as upper and lower lead  20  guiding and coil spring  140  support protrusions  122  on each interior side of each coil spring  140  end and reciprocal demarcating shelf features  125  on each exterior coil spring  140  end of frame  130   b . And whereas  130   b  requires a shelf  125 -post  138 ,  139 -convex protrusion  122  support structure,  130   a &#39;s circular depressions  132 ,  133  serves as coil spring  140 &#39;s end placement and support. Representationally, from top to bottom, both housing frame  130   a  (thick, left) and  130   b  (thin, right), are represented as (a) a lateral cross section, (b) a top view, (c) a side view and (d) a horizontal cross section. 
       FIG. 7  is a sectional view showing the two possible versions of  FIGS. 5  ( 130   a  and  130   b ) with the side load spring contact  140  removed. The housing  130   a  contains a depression  133  to hold and secure the side load spring contact  140  as illustrated in  FIG. 7  left. The housing  130   a  contains a recess  200  to accommodate the displacement of the side load spring contact  140  (not shown) as the 16-channel stimulation/recording lead  20  is inserted into the side load spring contact assembly  130   a . To further aid the capture of the side load coil spring  140  contact within housing  130   a  one or more post  136 - 139  ( FIG. 6 a    and  FIG. 6 b   ) maybe added providing proper placement and securing with and without depressions  132  and  133 . 
     Referring to  FIG. 8  and  FIG. 9  an isometric view of the present invention before inserting the 16-channel stimulation/recording lead  20  exhibiting connector lead rings  88  into the side load spring contact assembly  110  and an isometric view of after the 16-channel stimulation/recording lead  20  is inserted into the side load spring contact assembly  110  (thin  130   b ) showing the first interconnect band (ring)  40  making contact with side load spring contact  140  resulting in deformation  150  outward (indicated by both right and left arrows). 
     Referring to  FIG. 10 , side load spring contact assembly  130   b  shows the use of variable coil pitch and coil diameters  210  of the side load spring  140  of side load spring contact  130   b  as to better accommodate and secure stimulation/recording leads  20  insertion. 
     The particular embodiments disclosed above are illustrative only, as the application may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. It is therefore evident that the particular embodiments disclosed above may be altered or modified, and all such variations are considered within the scope and spirit of the application. Accordingly, the protection sought herein is as set forth in the description. It is apparent that an application with significant advantages has been described and illustrated. Although the present application is shown in a limited number of forms, it is not limited to just these forms, but is amenable to various changes and modifications without departing from the spirit thereof.