Patent Publication Number: US-2021177538-A1

Title: Medical device anchoring apparatus and placement tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/947,917, filed Dec. 13, 2019, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure generally relates to anchoring medical devices of implantable medical therapy systems, and more particularly to apparatus, tools, and systems that facilitate the anchoring of an elongate portion of the medical device within a body portal, for example, a burr hole formed in a patient&#39;s cranium. 
     BACKGROUND 
     Medical procedures for treating a variety of neurological conditions, for example, Parkinson&#39;s disease, essential tremor, and dystonia, require access to the brain, typically, through a burr hole formed in the cranium, for the insertion of deep brain stimulating electrodes. Burr holes may also be formed for the insertion of a delivery catheter, for example, to provide drug therapy for similar conditions, or an extraction catheter, for example, a hydrocephalus shunt. Stereotactic apparatus and procedures, which are known to those skilled in the art, may be employed by surgeons to locate inserted electrodes and/or drug delivery ports in target regions of the brain. 
     SUMMARY 
     The techniques of this disclosure generally relate to an apparatus that is adapted to be fastened to a cranium around a burr hole formed therethrough and a tool that can be utilized to deploy such apparatus. In one or more embodiments, the apparatus can include a base and a cover adapted to connect to the base. The base can include an alignment mark that can be aligned with an alignment mark of the cover such that the cover is oriented in a desired position relative to the base when the cover is connected to the base. Further, in one or more embodiments, the base can include a first lead retaining member and the cover can include a second lead retaining member, where the first and second lead retaining members are adapted to retain a lead when the cover is connected to the base and the lead extends between the first and second lead retaining members. 
     Further, the present disclosure provides various embodiments of a placement tool for an apparatus to be fastened to a cranium with a fastener around a burr hole formed through the cranium. The tool can include a retainer disposed within a channel of a receptacle that is adapted to hold a fastener. The retainer can include a recess or protrusion adapted to restrain the fastener against movement. Further, the tool can also include an arm that is adapted to align a fastener opening of the apparatus with a channel axis of the channel of the receptacle when the placement tool is engaged with the apparatus. 
     In one example, aspects of this disclosure relate to a placement tool for an apparatus to be fastened to a cranium with a fastener around a burr hole formed through the cranium. The placement tool includes a receptacle adapted to hold the fastener, where the receptacle includes a channel extending between an upper opening of the receptacle and a lower opening of the receptacle along a channel axis. The placement tool further includes a retainer disposed within the channel of the receptacle, where the retainer includes a recess or a protrusion adapted to restrain the fastener against movement. The fastener opening of the apparatus is configured to align with the channel axis of the channel of the receptacle when the placement tool is engaged with the apparatus. 
     In another example, aspects of this disclosure relate to an apparatus adapted to be fastened to a cranium around a burr hole formed therethrough. The apparatus includes a base having an orifice, an upper surface, and a lower surface, where the orifice is adapted to be aligned with the burr hole in a direction substantially orthogonal to the cranium. The apparatus further includes a cover adapted to connect to the base and extend over the orifice of the base. The base further includes a first alignment mark and the cover includes a second alignment mark. The first alignment mark is aligned with the second alignment mark in the direction substantially orthogonal to the cranium when the cover is aligned with and connected to the base. 
     In another example, aspects of this disclosure relate to a method that includes disposing a base on a cranium such that an orifice of the base is substantially aligned in a direction substantially orthogonal to the cranium with a burr hole disposed through the cranium, where the base further includes an upper surface and a lower surface. The method further includes connecting a cover to the base such that a first alignment mark disposed on the base is aligned with a second alignment mark disposed on the cover in the direction substantially orthogonal to the cranium, where the cover occludes the orifice of the base. 
     In another example, aspects of this disclosure relate to an apparatus adapted to be fastened to a cranium around a burr hole formed therethrough. The apparatus includes a base having an orifice, an upper surface, and a lower surface, where the orifice is adapted to be aligned with the burr hole in a direction substantially orthogonal to the cranium. The apparatus further includes a cover adapted to be connected to the base, where the cover includes an inner surface and a slot adapted to receive a lead of a medical device. The upper surface of the base includes a first lead retaining member and the inner surface of the cover includes a second lead retaining member. The first and second lead retaining members are adapted to retain the lead when the cover is connected to the base and the lead extends between the first and second lead retaining members. 
     In another example, aspects of this disclosure relate to a placement tool for an apparatus to be fastened to a cranium with a fastener around a burr hole formed through the cranium. The placement tool includes a receptacle adapted to hold the fastener, where the receptacle includes a channel extending between an upper opening of the receptacle and a lower opening of the receptacle along a channel axis. The placement tool also includes a retainer disposed within the channel of the receptacle, where the retainer includes a recess or a protrusion adapted to restrain the fastener against movement. The placement tool further includes an arm extending laterally from the receptacle, where the arm is adapted to align a fastener opening of the apparatus with the channel axis of the channel of the receptacle when the placement tool is engaged with the apparatus. The channel is adapted to align the fastener with a portion of a driving tool when disposed within the channel. 
     The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  is a schematic perspective view of one embodiment of a stereotactic guidance system mounted to a patient&#39;s cranium. 
         FIG. 1B  is a schematic perspective view of one embodiment of an elongate therapy delivery lead or catheter of an implantable medical device extending through an anchoring mechanism after the guidance system has been removed. 
         FIG. 1C  is a schematic perspective view of one embodiment of an implanted medical therapy system in which various embodiments of the present disclosure can be employed. 
         FIG. 2A  is a perspective view of one embodiment of an apparatus. 
         FIG. 2B  is a perspective view of the apparatus of  FIG. 2A . 
         FIG. 2C  is a side view of the apparatus of  FIG. 2A . 
         FIG. 2D  is a perspective view of a core of the apparatus of  FIG. 2A . 
         FIG. 2E  is a perspective view of an anchoring mechanism connected to the apparatus of  FIG. 2A . 
         FIG. 2F  is a perspective of the anchoring mechanism of  FIG. 2E . 
         FIG. 3  is a schematic cross-section view of a portion of the apparatus of  FIG. 2A  fastened to the patient&#39;s cranium. 
         FIG. 4  is a schematic perspective view of another embodiment of an apparatus. 
         FIG. 5  is a schematic side view of the apparatus of  FIG. 4  disposed on a cranium of a patient. 
         FIG. 6  is a schematic plan view of a base of the apparatus of  FIG. 4 . 
         FIG. 7  is a schematic plan view of a cover of the apparatus of  FIG. 4 . 
         FIG. 8  is a schematic side view of the apparatus of  FIG. 4  and a lead extending through the base. 
         FIG. 9  is a schematic perspective view of the apparatus of  FIG. 4 . 
         FIG. 10  is a schematic cross-section view of a portion of the apparatus of  FIG. 4  and the lead disposed between lead retaining members of the cover and the base. 
         FIG. 11  is a schematic cross-section view of the portion of the apparatus of  FIG. 10  with the lead retaining members of the cover and base retaining the lead. 
         FIG. 12  is a schematic cross-section view of the portion of the portion of the apparatus of  FIG. 11 . 
         FIG. 13  is a flow chart of one method of disposing the apparatus of  FIG. 4  on the cranium of the patient. 
         FIG. 14  is a schematic perspective view of one embodiment of a placement tool. 
         FIG. 15  is a schematic side view of the placement tool of  FIG. 14 . 
         FIG. 16  is a schematic perspective view of the placement tool of  FIG. 14  engaged with an apparatus. 
         FIG. 17  is a schematic side view of the placement tool and apparatus of  FIG. 16 . 
         FIG. 18  is a schematic cross-section view of portions of the tool and apparatus of  FIG. 16 . 
         FIG. 19  is a schematic perspective view of the portions of the tool and apparatus of  FIG. 18 . 
         FIG. 20  is a schematic perspective view of the placement tool and apparatus of  FIG. 16  with a driving tool inserted into a receptacle of the placement tool. 
         FIG. 21  is a schematic side view of the placement tool and apparatus of  FIG. 16  with the driving tool inserted into the receptacle of the placement tool and engaged with a fastener. 
         FIG. 22  is a schematic top view of the receptacle of the placement tool of  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION 
     The techniques of this disclosure generally relate to an apparatus that is adapted to be fastened to a cranium around a burr hole formed therethrough and a tool that can be utilized to deploy such apparatus. In one or more embodiments, the apparatus can include a base and a cover adapted to connect to the base. The base can include an alignment mark that can be aligned with an alignment mark of the cover such that the cover is oriented in a desired position relative to the base when the cover is connected to the base. Further, in one or more embodiments, the base can include a first lead retaining member and the cover can include a second lead retaining member, where the first and second lead retaining members are adapted to retain a lead when the cover is connected to the base and the lead extends between the first and second lead retaining members. 
     Further, the present disclosure provides various embodiments of a placement tool for an apparatus to be fastened to a cranium with a fastener around a burr hole formed through the cranium. The tool can include a retainer disposed within a channel of a receptacle that is adapted to hold a fastener. The retainer can include a recess or protrusion adapted to restrain the fastener against movement. Further, the fastener opening of the apparatus is configured to align with a channel axis of the channel of the receptacle when the placement tool is engaged with the apparatus. 
     Apparatuses that can be placed over a burr hole formed in a cranium of a patient and are adapted to hold a medical device or lead that extends into the cranium typically include a base and a cover. The cover can be oriented in various positions when connected to the base. In some circumstances, however, the cover has a preferred orientation in relation to the base. Such preferred orientation may, however, be difficult to discern, especially when being connected to the base during surgery. 
     Further, typical apparatuses can include a mechanism that is adapted to retain a lead or medical device that is deployed into the cranium of the patient through the burr hole. Such mechanisms can, however, be cumbersome and unable to prevent the lead from slipping or moving after deployment. 
     Such apparatuses can also be challenging to connect to the cranium of the patient. Typically, the base of the apparatus includes one or more openings through which a fastener can be threaded or inserted therethrough and into tissue and bone of the patient. The fastener can first be disposed within a receptacle of a placement tool. These fasteners can in some circumstances be quite small, thereby presenting a challenge to the surgeon when attempting to drive them through the base and into the skull. Further, such fasteners tend to be difficult to retain within the tool prior to or as the fastener is driven into the skull by a driving tool. 
     One or more embodiments of the present disclosure can provide various benefits over typical apparatuses and placement tools. For example, one or more embodiments of an apparatus described herein can include one or more alignment marks disposed on a cover and a base of the apparatus such that the surgeon can more easily connect the cover to the base in the desired orientation. Further, one or more embodiments of an apparatus described herein can include one or more lead retaining members disposed on an inner surface of the cover and an upper surface of the base. The lead retaining members can be adapted to retain a lead when the cover is connected to the base and the lead extends between the lead retaining members. In addition, one or more embodiments of a placement tool described herein can include a retainer disposed within a receptacle of the tool. The retainer can include a recess or protrusion that is adapted to restrain a fastener against movement as the fastener is aligned with a fastener opening of an apparatus. 
       FIG. 1A  is a schematic perspective view showing an exemplary stereotactic guidance system  100  (e.g. Medtronic Nexdrive Micropositioning Drive attached to the Medtronic Nexframe®) mounted to a patient&#39;s cranium  13 .  FIG. 1A  illustrates a ring  120  of guidance system  100 , which extends around a perimeter of a body portal, or burr hole  11  formed in cranium  13 , supporting a socket assembly  140  to which a micropositioning drive  160  is attached. An anchoring mechanism or base  112  ( FIG. 1B ; e.g., the Medtronic StimLoc®) can be mounted around burr hole  11  and fastened to cranium  13 , for example, via fasteners received through fastener openings  106  of a base ring of base  112 , prior to attaching ring  120  of guidance system  100 .  FIG. 1A  further illustrates an elongate therapy delivery lead or catheter  15  of a medical device being held within drive  160  for advancement through burr hole  11  and into the cranial space for positioning in a target region of the brain. 
       FIG. 1B  illustrates elongate therapy delivery lead or catheter  15  of the device extending through anchoring mechanism  112 , after guidance system  100  has been removed.  FIG. 1B  further illustrates therapy delivery lead or catheter  15  extending through a slot of mechanism  112  to be anchored between the mechanism and a cap or cover that snaps into place thereover (not shown; e.g., the Medtronic StimLoc® cap). Those skilled in the art appreciate that a proximal length of therapy delivery lead or catheter  15 , outside the cranial space, may be routed, beneath the scalp and subcutaneously, to a therapy generator of the device, for example, a generator  28  that is shown, in the schematic of  FIG. 1C , implanted subcutaneously in proximity to the patient&#39;s clavicle. With further reference to  FIG. 1C , a distal length  154  of therapy delivery lead or catheter  15 , which has been advanced through burr hole  11 , is shown including therapy delivery ports, or electrodes  26 A,  26 B positioned at the target region. 
     It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device. 
       FIG. 1C  is a schematic showing an implanted medical therapy system in which an apparatus  200  may be employed, according to some embodiments of the present disclosure.  FIG. 1C  illustrates the system including the aforementioned therapy generator  28  and elongate therapy delivery lead  15 , also referred to herein generally as a therapy delivery device, which is shown coupled thereto via a connector  30  that terminates the proximal length thereof. In other examples, the therapy delivery device may be a catheter. According to an exemplary embodiment, therapy generator  28  is configured to deliver electrical stimulation therapy to, and/or sense electrical signals from the patient&#39;s brain, via lead electrodes  26 A,  26 B that are mounted to distal length  154  of lead  15  and electrically coupled to connector  30  via insulated conductors. Those skilled in the art are familiar with suitable configurations and constructions for lead  15  and generator  28 . Therapy generator  28  can include processing circuitry, memory, signal generation circuitry, sensing circuitry, telemetry circuitry, and a power source, where the memory can include computer-readable instructions that are executed by the processing circuitry, for example, to deliver stimulation therapy to the patient, sense physiological signals of the patient, and/or perform other functions related to treating one or more conditions of the patient. The telemetry circuitry may include any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as a programmer  32 . Under the control of the processing circuitry the telemetry circuitry can receive downlink telemetry from and send uplink telemetry to programmer  32  with the aid of an antenna, which may be internal and/or external. Programmer  32  may be a handheld computing device, computer workstation, or networked computing device that includes electronics and other internal components necessary or desirable for executing the functions associated with the system. 
       FIG. 1C  further illustrates lead distal length  154  extending through an apparatus  200 , which is fastened to the patient&#39;s cranium  13  around the above-described burr hole  11 . According to embodiments described herein, apparatus  200  is configured to receive attachment thereto a medical device anchoring mechanism that secures lead  15  in place so that electrodes  26 A,  26 B remain positioned at the aforementioned target regions of the patient&#39;s brain for stimulation thereof over the course of the system implant. 
       FIGS. 2A-B  are perspective views of apparatus  200 ; and  FIG. 2C  is an elevation view of apparatus  200 .  FIGS. 2A-C  illustrate apparatus  200  including a substantially flat core  210  and a shell or base  240 , and  FIG. 2D  shows, in perspective view, core  210  without shell  240 .  FIG. 2D  illustrates core  210  including a ring portion  215  and first and second pliable arms  214  extending laterally from ring portion  215 , wherein each of first and second fastener members  212  of core  210  terminate a corresponding pliable arm  214 .  FIGS. 2A-C  further illustrate shell  240  encapsulating ring portion  215 . Ring portion  215  is indicated with dashed lines in  FIGS. 2A and 2C . Shell  240  defines an orifice  241  of apparatus  200 , which is substantially centered within ring portion  215  of core  210 . In  FIG. 2B , dashed lines accentuate a curved contour of a lower surface  24 L of shell  240 , to match a curvature of the patient&#39;s cranium (e.g. cranium  13  of  FIGS. 1A-C ). But core  210 , being substantially flat, extends within shell  240  without such a curvature. Core  210  can include any suitable material or materials, e.g., a medical grade titanium that is machined. Further, shell  240  can include any suitable material or materials, e.g., a medical grade polymer, such as polysulfone or polyether ether ketone (PEEK), that can be insert molded around core  210 . In one or more embodiments, the curvature of shell lower surface  24 L corresponds to an approximately ten inch diameter cranium, and a nominal maximum thickness between upper surface  24 U and lower surface  24 L may be approximately 0.05 inches. 
     With further reference to  FIG. 2A , an upper surface  24 U of apparatus shell or base  240  defines a rim that has a plurality of uniform engagement features EF formed therein, which are equally spaced apart from one another around an entire perimeter of the rim. Engagement features EF can be adapted to receive attachment of the aforementioned medical device anchoring mechanism that secures a portion of the implanted medical device in place, for example, elongate therapy delivery lead  15  ( FIGS. 1A-C ). Such an anchoring mechanism is described in co-pending and commonly assigned U.S. Provisional Patent Applications having Ser. Nos. 62/400,140 and 62/446,923 (Attorney Docket Nos. C00014631.USP1 C00014631.USP2), salient portions of which are hereby incorporated by reference.  FIG. 2E  is a perspective view of a clip or jaw  300  of such an anchoring mechanism seated against shell upper surface  24 U of apparatus  200 .  FIG. 2E  illustrates jaw  300  including a plurality of uniform interlocking features  336  formed in an outer perimeter edge of a first plate member  330  thereof, which interlock with engagement features EF of apparatus  200 .  FIG. 2E  further illustrates first plate member  330  of jaw  300  including a sidewall  310  that has a gripping surface opposing that of a sidewall  320  of a second plate member  340  of jaw  300 , where second plate member  340  is movable relative to first plate member  330  to open and close jaw  300 . In  FIG. 2E , jaw  300  is shown closed and gripping the implanted lead  15  between grip surfaces of sidewalls  310 ,  320 . The uniformity of form and spacing of apparatus engagement features EF and jaw interlocking features  336  allow the operator to seat jaw  300  in a plurality of orientations about a longitudinal axis  2  of apparatus  200 , for example, to accommodate a trajectory of the implanted lead  15  through burr hole  11 .  FIG. 2F  is a perspective view of a cap  350  of the anchoring mechanism covering jaw  300  and including a channel  355  through which the anchored lead  15  passes. According to some embodiments, for example, like those described in the aforementioned co-pending and commonly assigned U.S. Provisional Patent Application Ser. Nos. 62/400,140 and 62/446,923, cap or cover  350  includes studs that project from a lower surface thereof and are configured to mate in a press fit with apertures  330 A ( FIG. 2E ) of jaw plate member  330 . 
     With further reference to  FIGS. 2B-C , each fastener member  212  of apparatus core  210  has an aperture or fastener opening  212 A to receive extension of a bone screw  23  therethrough for fastening apparatus  200  to the patient&#39;s cranium  13  when apparatus orifice  241  has been centered over cranial burr hole  11 , for example, as described below in conjunction with  FIGS. 4A-C . When each bone screw  23  is positioned through the corresponding fastener member  212  of the centered apparatus  200  and driven into cranium  13 , for example as illustrated in the schematic cross-section of  FIG. 3 , each pliable arm  214  of core  210  may bend from the relaxed substantially flat form of core  210  to generally conform to the curvature of cranium  13 .  FIG. 3  further illustrates cranial bone material BP, which has been displaced by the driven bone screw  23 , piled up in a pillar-like formation that surrounds screw  23 . Because the displaced bone material BP is relatively hard and firm, and remains attached to cranium  13 , unless some clearance between fastener member  212  and cranium  13  is provided, the fastened apparatus  200  may rock, or wiggle, and not provide a stable base for the aforementioned medical device anchoring mechanism. Thus, according to preferred embodiments, and with reference to  FIGS. 2B and 3 , each fastener member  212  of apparatus has a concave surface  212 C facing in a same direction as lower surface  24 L of shell  240  to provide clearance for displaced bone material BP. The fastener openings  212 A of each fastener member  212  are shown extending through an apex of the corresponding concave surface  212 C. It should be noted that, according to some alternate embodiments, core  210  of apparatus  200  can include more than two pliable arms  214  and corresponding fastener members  212 . 
     The various embodiments of apparatuses described herein can include one or more alignment marks to assist in orientating a cover of the apparatus with the base. For example,  FIGS. 4-6  are various views of one embodiment of an apparatus  400 . All of the design considerations and possibilities regarding the apparatus  200  of  FIGS. 2A-3  apply equally to the apparatus  400  of  FIGS. 4-6 . The apparatus  400  can be adapted to be fastened to a cranium  401  around a burr hole  405  formed therethrough. The apparatus  400  includes a base  402  ( FIG. 6 ) having an orifice  404 , an upper surface  406 , and a lower surface  408 . The orifice  404  is adapted to be aligned with the burr hole  405  in a direction  403  substantially orthogonal to the cranium  401  as can be seen, e.g., in  FIG. 5 . Further, in one or more embodiments, the lower surface  408  can include a contour  410  that substantially matches a curvature  412  of the cranium  401  around the burr hole  405  as shown in  FIG. 5 . As used herein, the term “substantially matches” means that a gap between the lower surface  408  and the cranium  401  is no greater than 10 mm. In one or more embodiments, the term “substantially matches” means that the lower surface  408  generally conforms to the curvature  412  of the cranium  401 . The apparatus  400  can also include a cover  414  adapted to connect to the base  402  and extend over the orifice  404  of the base. 
     The base  402  further includes a first alignment mark  416  and the cover  414  includes a second alignment mark  418 . The first alignment mark  416  is aligned with the second alignment mark  418  in the direction  403  substantially orthogonal to the cranium  401  when the cover  414  is aligned with and connected to the base  402 . Although depicted as including two alignment marks  416 ,  418 , the apparatus  400  can include any suitable alignment marks disposed in any suitable portion or portion of the base  402  and the cover  414 . 
     The base  402  can take any suitable shape or shapes and have any suitable dimensions. Further, the base  402  can include any suitable material or materials. The base  402  can be connected to the cranium  401  using any suitable technique or techniques. In one or more embodiments, the base  402  can be connected to the cranium  401  by one or more fasteners (e.g., fastener  23  of  FIG. 3 ) that are disposed through fastener openings  407  formed between the upper surface  406  and the lower surface  408  of the base  402 . 
     The cover  414 , which is adapted to connect to the base  402 , can take any suitable shape or shapes and have any suitable dimensions. Further, the cover  414  can include any suitable material or materials. In one or more embodiments, the cover  414  is substantially transparent such that the first alignment mark  416  of the base  402  is visible through the cover when the cover is connected to the base. As used herein, the term “substantially transparent” means that the cover of the apparatus transmits greater than 50% of electromagnetic radiation incident on the substrate for a selected wavelength or range of wavelengths, assuming no reflection at the air-substrate boundaries. The cover  414  can include any suitable materials such that it is substantially transparent, e.g., plastic, nylon, silicone, etc. 
     The first alignment mark  416  can be disposed in any suitable location on the base  402 . In one or more embodiments, the first alignment mark  416  can be disposed on the upper surface  406  of the base  402 . In one or more embodiments, the base  402  can be substantially transparent, and the first alignment mark  416  can be disposed on the lower surface  408 . In such embodiments, the first alignment mark  416  can be visible through the base  402 . 
     Further, the second alignment mark  418  can be disposed in any suitable location on the cover  414 . In one or more embodiments, the second alignment mark  418  can be disposed on an inner surface  420  of the cover  414 . In one or more embodiments, the second alignment mark  418  can be disposed on an outer surface  422  of the cover  414 . 
     Although depicted as including triangular shapes, the first and second alignment marks  416 ,  418  can include any suitable mark, e.g., at least one of an indicium, a protrusion, a recess, one or more lines, one or more geometric shapes (e.g., rectangular, ovular, triangular), an icon, an image, or a color. In one or more embodiments, the first alignment mark  416  is the same as the second alignment mark  418 . In one or more embodiments, the first alignment mark  416  is different from the second alignment mark  418 . 
     The first and second alignment marks  416 ,  418  can be disposed on the base  402  and the cover  414  using any suitable technique or techniques. In one or more embodiments, at least one of the first and second alignment marks  416 ,  418  can be formed separate from the respective base  402  and cover  414  and connected to the base or cover using any suitable technique or techniques. In one or more embodiments, at least one of the first or second alignment marks  416 ,  418  can be integral with the respective base  402  and cover  414 . In such embodiments, the alignment marks  416 ,  418  can be formed using any suitable technique or techniques, e.g., molding, embossing, etching, etc. 
     In one or more embodiments, at least one of the first or second alignment marks  416 ,  418  can include one or more colors. For example, the first alignment mark  416  can include a first color and the second alignment mark  418  can include a second color. The first color and the second color can combine to provide a third color to a user viewing the outer surface  422  of the cover  414  when the first alignment mark is aligned with the second alignment mark. For example, the first alignment mark  416  can be blue and the second alignment mark  418  can be yellow. The two alignment marks  416 ,  418  would, therefore, combine to provide a green color that indicates to the user that the first alignment mark is aligned with the second alignment mark along the axis  403 . 
     Further, each of the alignment marks  416 ,  418  can be selected such that when aligned form a shape that is different from the shapes of each of the alignment marks. The formation of a new shape can indicate to the user that the first and second alignment marks  416 ,  418  are aligned and the cover  414  is in the desired orientation relative to the base  402 . For example, the first alignment mark  416  can include a triangular shape and the second alignment mark  418  can include a triangular shape that is rotated about a normal to the upper surface  406  of the base. The first shape and the second shape can combine to form a star shape as viewed by the user when viewing the outer surface  422  of the cover  414  when the first alignment mark  416  is aligned with the second alignment mark  418  and the cover is connected to the base  402 . 
     As mentioned herein, the first and second alignment marks  416 ,  418  can include one or more protrusions or recesses. In one or more embodiments, the first alignment mark  416  can include a protrusion disposed on the upper surface  406  of the base  402  and the second alignment mark  418  can include a recess disposed on the inner surface  420  of the cover  414 . The second alignment mark  418  is adapted to engage the first alignment mark  416  when the cover  414  is connected to the base  402  such that the first and second alignment marks fit into place, thereby indicating to the user that the cover is oriented in the desired position relative to the base. In one or more embodiments, the first alignment mark  416  can include a recess disposed on the upper surface  406  of the base  402  and the second alignment mark  418  can include a protrusion disposed on the inner surface  420  of the cover  414 . The first alignment mark  416  is adapted to engage the second alignment mark  418  when the cover  414  is connected to the base  402 . Each of the first and second alignment marks  416 ,  418  can include one or more protrusions or recesses that take any suitable shape or shapes. 
     Any suitable technique or techniques can be utilized to dispose the cover  414  onto the base  402  such the first and second alignment marks  416 ,  418  are aligned. For example,  FIG. 13  is a flowchart of one method  500  of connecting the cover  414  to the base  402 . Although described in regard to apparatus  400  of  FIGS. 4-12 , the method  500  can be utilized with any suitable apparatus. 
     At  502 , the base  402  is disposed on the cranium  401  such that the orifice  404  of the base is substantially aligned in a direction substantially orthogonal to the cranium with the burr hole  405  disposed through the cranium. In one or more embodiments, a core (e.g., core  210  of  FIG. 2A ) can be fastened to the cranium around the burr hole  405  prior to disposing the base  402  on the cranium  401 , where the base  402  encapsulates a ring portion (e.g., ring portion  215  of  FIG. 2D ) of the core that surrounds the burr hole when the base is disposed on the cranium. The cover  414  can be connected to the base  402  such that the first alignment mark  416  disposed on the base is aligned with the second alignment mark  418  disposed on the cover in the direction substantially orthogonal to the cranium  401  at  504 , where the cover occludes the orifice  404  of the base at  506 . 
     As mentioned herein, the various embodiments of apparatuses can include one or more lead retaining members for retaining a lead or medical device that has been disposed within the cranium through burr hole. For example, as shown in  FIGS. 6-7 , the upper surface  406  of the base  402  includes a first lead retaining member  424 , and the inner surface  420  of the cover  414  includes a second lead retaining member  426 . The first and second lead retaining members  424 ,  426  are adapted to retain a lead  428  ( FIG. 9 ) when the cover  414  is connected to the base  402  and the lead extends between the first and second lead retaining members as shown in  FIGS. 9-12 . In one or more embodiments, the first and second lead retaining members  424 ,  426  are adapted to retain at least two leads when the cover  414  is connected to the base  402  and each of the at least two leads extend between the first and second lead retaining members. The leads can include any suitable lead or leads, e.g., lead wires, lead circuits, lead members, etc. The first and second lead retaining members  424 ,  426  can be adapted to retain any suitable number of leads. 
     The apparatus  400  can include at least first and second lead retaining members  424 ,  426  and one or more alignment marks  416 ,  418 . In one or more embodiments, the apparatus  400  can include one or more alignment marks  416 ,  418  and no lead retaining members. Further, in one or more embodiments, the apparatus  400  can include at least first and second lead retaining members  424 ,  426  and no alignment marks. 
     The first and second lead retaining member  424 ,  426  can include any suitable elements or components that can be adapted to retain the lead  428 . For example, the first lead retaining member  424  includes protrusion  430 , and the second lead retaining member  426  includes a first protrusion  432  and a second protrusion  433 . The protrusions  430 ,  432 ,  433  can take any suitable shape or shapes and have any suitable dimensions. As shown in  FIGS. 6-12 , the protrusions  430 ,  432 ,  433  of each of the first and second lead retaining members  424 ,  426  include one or more elongated teeth that have a substantially triangular cross-section in a plane orthogonal to the inner surface  420  of the cover  414  and the upper surface  406  of the base  402  respectively, i.e., in the plane of  FIGS. 10-12 . The protrusion  430  of the first lead retaining member  424  and the protrusions  432 ,  433  of the second lead retaining member  426  can have the same shape. In one or more embodiments, each of the protrusions  430 ,  432 ,  433  can take a unique shape. Further, each of the first and second lead retaining members  424 ,  426  can have any suitable number of protrusions  430 ,  432 ,  433 . In one or more embodiments, each of the first lead retaining member  424  and the second lead retaining member  426  can have a protrusion  430 ,  432 ,  433  that is different from another protrusion of respective member. 
     The protrusions  430 ,  432 ,  433  can be oriented in any suitable arrangement relative to the lead  428 , the base  402 , and the cover  414 . In one or more embodiments, each protrusion  430 ,  432 ,  433  extends along a gripping axis  438  that is substantially orthogonal to a slot axis  440  of a slot  442  of the cover  414  when the cover is connected to the base  402 . The slot  442  of the cover  414  is adapted to allow the lead  428  to extend therethrough and beyond the cover and the base  402 . As used herein, the term “substantially orthogonal” means that the slot axis  440  forms an angle with the gripping axis  438  that is at least 85 degrees and no greater than 95 degrees. In one or more embodiments, at least one of the protrusions  430 ,  432 ,  433  can extend along an axis that forms an angle with an axis of another protrusion. 
     Further, the first lead retaining structure  424  can be disposed in any suitable location on the upper surface  406  of the base  402 , and the second lead retaining structure  426  can be disposed in any suitable location on the inner surface  420  of the cover  414 . Although depicted as having one lead retaining member  424 , the base  402  can include any suitable number of lead retaining structures. Further, the cover  414  can also include any suitable number of lead retaining members. 
     For example, the upper surface  406  of the base  402  includes a third lead retaining member  456  ( FIG. 6 ) disposed such that the orifice  404  is disposed between the first lead retaining member  424  and the third lead retaining member. Further, the inner surface  420  of the cover  414  includes a fourth lead retaining member  458  ( FIG. 7 ), where the third lead retaining member  456  and fourth lead retaining member are adapted to retain the lead  428  of the medical device when the cover is connected to the base  402  and the lead extends between the third and fourth lead retaining members. The third and fourth lead retaining members  456 ,  458  can include any suitable protrusions, e.g., the same protrusions described herein regarding the first and second lead retaining members  424 ,  426 . 
     The protrusion  430  of the first lead retaining member  424  can be disposed in any suitable relationship relative to the protrusions  432 ,  433  of the second lead retaining member  426 . For example, as shown in  FIGS. 10-12 , the protrusion  430  of the first lead retaining member  424  is adapted to engage the lead  428 , and the protrusions  432 ,  433  of the second lead retaining member  426  are laterally spaced apart from the protrusion of the first lead retaining member when the cover  414  is connected to the base  402 . The protrusions  432 ,  433  of the second lead retaining member  426  are also adapted to engage the lead  428  of the medical device. 
     The lead  428  that is retained by the first and second lead retaining members  424 ,  426  can have any suitable structure and include any suitable material or materials. As shown in  FIGS. 10-12 , the lead  428  includes an elongated body  444  and a conductor  446  wound around the elongated body. The elongated body  444  can include any suitable dielectric material or materials, and the conductor  446  can include any suitable conductive materials. 
     As can be seen in  FIG. 11 , the protrusions  430 ,  432 ,  433  of the first and second lead retaining members  424 ,  426  are adapted to displace the conductor  446  to retain the lead  428  when the cover  414  is connected to the base  402 . In one or more embodiments, a lateral spacing  448  between the protrusion  430  of the first lead retaining member  424  and a protrusion  432  of the second lead retaining member  426  that is provided when the cover  414  is connected to the base  402  can be any suitable distance. In one or more embodiments, such lateral spacing  448  is equal to no greater than eight times a diameter  450  of the conductor  446  as shown in  FIG. 11 , such that at least two windings  452  of the conductor are disposed between the protrusion  430  of the first lead retaining member  424  and one protrusion  432  of the second lead retaining member when the first and second lead retaining members are engaged with the elongated body  444  of the lead  428  of the medical device. In one or more embodiments, at least four windings  452  of the conductor  446  are disposed between the protrusion  430  of the first lead retaining member  424  and one protrusion  432  of the second lead retaining member  426  when the first and second lead retaining members are engaged with the elongated body  444  of the lead  428  of the medical device. In one or more embodiments, the second lead retaining member  426  of the cover  414  includes a second protrusion  433  laterally spaced from the protrusion  432  of the second lead retaining member such that the protrusion  430  of the first lead retaining member  424  of the base  402  is laterally disposed between the protrusion  432  and the second protrusion  433  of the second lead retaining member when the cover is connected to the base as is shown in  FIG. 11 . 
     Any suitable technique or techniques can be utilized to dispose an apparatus (e.g., anchoring apparatus  400  of  FIGS. 1-12 ) on a cranium of a patient. For example,  FIGS. 14-22  are various views of one embodiment of a placement tool  600  for an apparatus  602  to be fastened to a cranium (e.g., cranium  13  of  FIGS. 1A-B ) with a fastener  604  around a burr hole (e.g., burr hole  11  of  FIG. 1B ) formed through the cranium. The apparatus  602  can include any suitable apparatus, e.g., apparatus  400  of  FIGS. 1-12 . All of the design considerations and possibilities regarding the apparatus  400  of  FIGS. 1-12  apply equally to the apparatus  602  of  FIGS. 16-22 . 
     The placement tool  600  includes a receptacle  606  adapted to hold the fastener  604 , where the receptacle includes a channel  608  extending between an upper opening  610  of the receptacle and a lower opening  612  of the receptacle along a channel axis  614 . The placement tool  600  further includes a retainer  616  disposed within the channel  608  of the receptacle  606 . The retainer  616  includes a recess or a protrusion  618  adapted to restrain the fastener  604  against movement. Further, the fastener opening  622  of the apparatus  602  is configured to align with the channel axis  614  of the channel  608  of the receptacle  606  when the placement tool is engaged with the apparatus. The tool  600  can also include an optional arm  620  that extends laterally from the receptacle  606 , where the arm is configured to align the fastener opening  622  of the apparatus  602  with the channel axis  614  of the channel  608  of the receptacle  606  when the placement tool is engaged with the apparatus. In one or more embodiments, the receptacle  606  can extend from the central portion  624  without being coupled or connected via arms to the central portion. 
     The placement tool  600  can have any suitable dimensions and take any suitable shape or shapes. In one or more embodiments, the tool  600  includes a central portion  624  that is generally aligned along a central axis  626  of the tool. As used herein, the term “generally aligned” means that the central portion  624  is substantially rotationally symmetrical about the central axis  626  of the tool  600 . The channel axis  614  of the channel  610  of the receptacle  646  extends at an angle  628  ( FIG. 15 ) with the central axis of the tool. The angle  628  can include any suitable angle greater than 0 degrees and less than 90 degrees to conform to the curvature of the cranium. In other embodiments, the angle  628  could be, e.g., 0 degrees, at least 5 degrees, at least 10 degrees, at least 15 degrees, or at least 20 degrees. In other embodiments, the angle  628  can be no greater than 45 degrees, 40 degrees, 35 degrees, 30 degrees, or 25 degrees. In yet other embodiments, the angle  628  may be greater than 45 degrees but less than 90 degrees. 
     The central portion  624  of the tool  600  can be configured to engage with an upper surface  630  of the apparatus  602  as is illustrated in  FIGS. 16-21 . For example, the central portion  624  can include a lower part  632  that is adapted to extend through an orifice  634  of the apparatus  602  and to fit within the burr hole. For example, opposing elastically flexible legs  636  of the central portion  624  can be pushed toward one another to insert the lower part  632  of the central portion through the orifice  634  of the apparatus  602 , and then can be released so that tool  600  holds the apparatus in a press fit. The lower part  632  can be configured to fit within the cranial burr hole so that the tool  600  serves to center orifice  634  of the apparatus  602  over burr hole, for example, as illustrated in  FIGS. 1B-C . In one or more embodiments, the tool  600  does not include the central portion  624 . 
     The receptacle  606  can take any suitable shape or shapes and have any suitable dimensions. Further, the channel  608  can also take any suitable shape or shapes and have suitable dimensions. The channel  608  includes an inner wall  638 . In one or more embodiments, the channel  608  can have any suitable cross-sectional shape formed by the inner wall  638  in a plane substantially orthogonal to the channel axis  614 . In one or more embodiments, this cross-sectional area can take an elliptical (e.g., circular) shape. Further, the receptacle  606  can have any suitable length as measured between the upper opening  610  and a lower opening  612 . In one or more embodiments, the length of the receptacle  606  is at least two times the length of the fastener  604 . In one or more embodiments, the length of the receptacle  606  is at least three times the length of the fastener  604 . 
     In one or more embodiments, the receptacle  606  can include an extension  642  that defines a lower opening  612  of the receptacle. The extension  642  can be adapted to shroud the fastener opening  622  of the apparatus  602  when the tool  600  is engaged with the apparatus. The extension  642  can take any suitable shape or shapes and have any suitable dimensions. 
     Disposed within the channel  608  is the retainer  616 . The retainer  616  can be disposed in any suitable location within the channel  608 . The retainer  616  can include any suitable element or component that is adapted to restrain the fastener  604  against movement. For example, the retainer  616  can be adapted to prevent the fastener  604  from being displaced from the receptacle  606  in a direction from the lower opening  612  to the upper opening  610  of the receptacle. In one or more embodiments, the retainer  616  includes the recess or protrusion  618  that is adapted to restrain the fastener  604  against movement. In one or more embodiments, the retainer  616  can include one or more recesses and one or more protrusions. 
     As shown in the illustrated embodiment, the retainer  616  includes protrusions  618 . The retainer  616  can include any suitable number of protrusions  618 . Further, such protrusion  618  can take any suitable shape or shapes and have any suitable dimensions. In one or more embodiments, the protrusions  618  are adapted to engage the fastener  604 . For example, the protrusions  618  can be adapted to engage a head  640  of the fastener  604  as shown in  FIGS. 18-19 . In one or more embodiments, the retainer  616  can include a recess  644  as shown in  FIG. 18 . A portion of the fastener  604  can be adapted to be disposed within the recess  644 . The recess  644  can be disposed in any suitable location relative to the channel  608 . In one or more embodiments, the recess  644  is formed between protrusions  618  and the lower opening  612  of the channel  608 . The recess  644  can take any suitable shape or shapes. As shown in  FIG. 18 , the recess  644  takes a shape that is similar to a shape of the head  640  of the fastener  604 . 
     The retainer  616  can be formed separately from the receptacle  606  and disposed within the channel  608  of the receptacle using any suitable technique or techniques. In one or more embodiments, the retainer  616  can be integral with the receptacle, i.e., the retainer is unitarily formed of a single material with the receptacle  606 . For example, in one or more embodiments, the protrusions  618  are formed or disposed on the inner wall  638  of the channel  608 . 
     The retainer  616  can also include a receiver  646  as shown in  FIG. 18 . The receiver  646  can take any suitable shape or shapes and have any suitable dimensions. In one or more embodiments, the receiver  646  is disposed between the recess or protrusions  618  and the lower opening  612  of the receptacle  606 . The receiver  646  is adapted to engage the fastener  604  to provide a friction fit for the fastener as can be seen in  FIG. 18 . The receiver  646  can include a cross-sectional area in a plane substantially orthogonal to the channel axis  614  of the receptacle  606  that is less than a cross-sectional area of the channel  608  in the plane substantially orthogonal to the channel axis. 
     In general, the receptacle  616  can be adapted to expand outwardly from the channel axis  614  such that the fastener  604  can be directed through the lower opening  612  of the receptacle  606 . In one or more embodiments, the receiver  646  of the retainer  616  can be adapted to deform such that the fastener  604  can be directed through the lower opening  612  of the receptacle  606 . Such deformation can be provided by the structure of the receiver  646  and/or the material utilized to form the receiver. 
     The tool  600  also includes the optional arm  620  that extends laterally from the receptacle  606 . In one or more embodiments, the arm  620  extends substantially orthogonally to the central axis  626 . The arm  620  can be adapted to align the fastener opening  622  ( FIG. 19 ) of the apparatus  600  with the channel axis  626  of the channel  608  of the receptacle  606  when the placement tool  600  is engaged with the apparatus  602 . The arm  620  can take any suitable shape or shapes and have any suitable dimensions. In one or more embodiments, the arm  620  is connected to the central portion  624  of the tool  600 . Further, the arm  620  can be connected to the central portion  624  and the retainer  606  using any suitable technique or techniques. In one or more embodiments, the arm  620  is integral with at least one of the central portion  624  or the receptacle  606 . 
     The tool  600  can include any suitable number of receptacles  606 . For example, the tool  600  includes a second receptacle  648  adapted to hold a second fastener  650 . In embodiments where the tool  600  includes the second receptacle  648 , the receptacle  606  can be referred to as the first receptacle, the channel  608  as the first channel, the channel axis  614  as the first channel axis, the retainer  616  as the first retainer, the fastener  604  as the first fastener, the fastener opening  622  of the apparatus  602  as the first fastener opening, and the arm  620  as the first arm. The second receptacle  648  can include any suitable receptacle, e.g., receptacle  606 . All of the design considerations and possibilities regarding the receptacle  606  apply equally to the second receptacle  648 . The second receptacle  648  includes a second channel  652  that extends between an upper opening  654  and a lower opening  656  along a second channel axis  658 . The tool  600  can also include a second retainer  660  disposed within the second channel  652  of the second receptacle  648 . The second retainer  660  includes a recess or protrusion  662  adapted to engage the second fastener  650 . Further, the second retainer  660  can include a receiver  664  disposed between the recess or protrusion  662  and the lower opening  656  of the channel  652  of the second receptacle  648 . The second receiver  664  is adapted to engage the second fastener  650  to provide a friction fit for the second fastener. 
     The tool  600  can also include a second arm  666  extending laterally from the second receptacle  648 . The second arm  666  is adapted to align a second fastener opening  668  ( FIG. 16 ) of the apparatus  602  with the second channel axis  658  when the tool is engaged with the apparatus. The second arm  666  can position the second receptacle  648  such that the second channel axis  658  forms an angle  670  with the central axis  626 . The angle  670  can be any suitable angle, e.g., the same angles described herein regarding angle  628 . 
     As described herein, the first and second receptacles  606 ,  648  can include any suitable first and second channels  608 ,  652  respectively. In one or more embodiments, at least one of the first and second channels  608 ,  648  can be adapted to align at least one of the fasteners  604 ,  650  with a portion of a driving tool  672  when the tool is disposed within the channel. For example, as shown in  FIG. 20 , the channel  608  of the first receptacle  606  is adapted to align the fastener  604  with a portion of the driving tool  672  when the driving tool is disposed within the channel. Any suitable technique or techniques can be utilized to align the driving tool  672  with the fastener  604 . In one or more embodiments, the inner surface  638  of the channel  608  can have a circumference in a plane perpendicular to the channel axis  614  that is substantially equal to a circumference of an outer surface  674  of the portion of the driving tool  672  that is inserted into the channel. 
     Further, the retainer  616  of the first receptacle  606  and/or the retainer  660  of the second receptacle  648  can be adapted to guide a blade  676  of the driving tool  672  into a groove  678  in the head  640  of the fastener  604  ( FIG. 22 ). For example, the  616  of the first receptacle  606  can include first and second protrusions  680 ,  682  that extend from the inner surface  638  of the channel  608  of the receptacle as shown in  FIG. 22 . The first and second protrusions  680 ,  682  are separated by a slot  684  that is substantially parallel to the channel axis  614 . The slot  684  is adapted to receive the blade  676  disposed on an end  686  of the driving tool  672  and guide the blade into the groove  678  of the head  640  of the fastener  604  as shown in  FIGS. 21-22 . In one or more embodiments, protrusions  618  of retainer  16  can form additional slots  688  such that the retainer can accommodate a Phillips-type driving tool  672 . 
     In one or more embodiments, the protrusion  618  can be disposed on the inner surface  638  of the channel  608  and can continuously extend around the circumference of the inner surface of the channel, where the protrusion includes a slot  688  that is substantially parallel to the channel axis  614 . This slot is adapted to receive the blade  676  disposed on the end  686  of the driving pool  672  and direct the blade into the groove  678  in the head  640  of the fastener  604 . In one or more embodiments, an additional slot  688  can be formed such that the retainer  616  can accommodate a flathead-type driving tool  672 .