Abstract:
A cranial burr hole plug with an insertion tool and method of implantation is provided. The burr hole plug includes a shell; a collet interlocked within the shell; a clamp compressing the collet around an elongated medical device exiting the skull of a patient, such as a catheter or lead; and a cover over the clamp, collet, and shell. The insertion tool inserts the collet within the shell and locks the collet around the clamp. The method of implantation includes inserting the burr hole plug components in a cranial burr hole using the insertion tool and securing the exiting medical device without disturbing the position of the medical device.

Description:
[0001]    The present application claims the benefit of U.S. Provisional Patent Application Serial No. 60/403,787, filed Aug. 14, 2002, which application is incorporated herein by reference in its entirety. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to methods and apparatuses for securing elongated medical devices such as catheters or leads within a cranial burr hole.  
         BACKGROUND OF THE INVENTION  
         [0003]    Deep brain stimulation (DBS) and other related procedures involving implantation of leads and catheters are increasingly used to treat Parkinson&#39;s disease, dystonia, essential tremor, seizure disorders, obesity, depression, restoration of motor control, and other debilitating diseases. During these procedures, a catheter, lead, or other medical device is strategically placed at a target site in the brain. The body of the device then exits through a burr hole cut in the skull. The device must be secured as it exits the skull so as to prevent movement of the device from the precise target site in the brain, and the burr hole must be filled.  
           [0004]    Current burr hole plugs placed under the skin of a patient&#39;s head are unduly large and unsightly. Further, many current burr hole plugs do not adequately hold the exiting device in place; some force the device to bend at a right angle at the exit without any protection which makes the device vulnerable to fracture or short circuit. During placement of current burr hole plugs, the exiting device often moves from its precise target site in the brain. After placement of current burr hole plugs, the device may migrate over time and will require additional surgical procedures to correct the problem.  
           [0005]    Due to a lack of adequate burr hole plugs, many physicians attempt to compensate by securing the device to the skull with sutures and clamping screws, and then filling the burr hole with cyanoacrylate or bone cement. Securing the device with sutures and clamping screws subjects the patient to unnecessary human error. Further, suturing and clamping are cumbersome and time consuming steps. Filling the burr hole with cyanoacrylate or bone cement is messy and permanently locks the device into place, preventing easy access for future necessary procedures.  
           [0006]    There is, therefore, a need to provide a relatively small burr hole plug that, without disturbing the position of the device at the target site in the brain, adequately and permanently secures a medical device such as a catheter or lead exiting a burr hole at a gradual angle, but remains accessible for future procedure. Further, there is a need to provide a method of implanting a burr hole plug that mitigates human error and permits safe and efficient implantation.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention addresses the above and other needs by providing a burr hole plug, a method of implanting the burr hole plug, and an insertion tool. The burr hole plug includes a shell, a collet, a clamp, and a cover. The burr hole plug is smaller than most currently available burr hole plugs. The burr hole plug is installed and secures the exiting device with simultaneous 360° radial pressure from the collet portion of the burr hole plug, thus avoiding disturbance of the position of a medical device at the target site in the brain. The clamp mechanically locks the collet around the body of the medical device without exposing the medical device to pulling, pushing, or twisting forces that could cause unwanted displacement of the medical device from its target site in the brain. The collet simply clamps the medical device from all directions through radial force. The collet, including all other parts of the burr hole plug, is capable of being mechanically unlocked and disassembled to release the medical device and perform any needed future procedures. The device is able to exit the brain at a gradual angle through a conical chamber within the collet, through the tip of the conical chamber where the collet grips the device, and out from underneath the protective cover placed over the collet and clamp.  
           [0008]    The method of implantation includes inserting the shell that is sized to friction fit against the inner circumference of the burr hole; interlocking a collet within the shell; placing a clamp over the collet, which clamp compresses the collet as the clamp rotates and interlocks with the shell; and placing a cover over the clamp, collet, and shell. Certain portions of the burr hole plug may be inserted separately or simultaneously using an insertion tool tailored to maximize the efficiency of implantation.  
           [0009]    This summary should not be taken in a limiting sense; the scope of the invention should be determined with reference to the claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The above and other aspects of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein:  
         [0011]    [0011]FIG. 1 shows an exploded view of a burr hole plug;  
         [0012]    [0012]FIG. 2 shows an exploded view of an alternate embodiment of a burr hole plug;  
         [0013]    [0013]FIG. 3 shows an isometric top view of a shell;  
         [0014]    [0014]FIG. 4A shows an isometric top front view of an alternate embodiment of a shell;  
         [0015]    [0015]FIG. 4B shows an isometric bottom front view of the shell shown in FIG. 4A;  
         [0016]    [0016]FIG. 5A shows an isometric front view of a collet;  
         [0017]    [0017]FIG. 5B shows an isometric rear view of the collet shown in FIG. 5A;  
         [0018]    [0018]FIG. 6 shows an isometric view of a collet with a side slot;  
         [0019]    [0019]FIG. 7 shows an isometric view of a clamp;  
         [0020]    [0020]FIG. 8 shows an isometric top view of a cover;  
         [0021]    [0021]FIG. 9 shows a cross-sectional view of a cover with pin holes;  
         [0022]    [0022]FIG. 10 shows an isometric side view of an insertion tool;  
         [0023]    [0023]FIG. 11 shows an isometric top view of an integrated shell-collet; and  
         [0024]    [0024]FIG. 12 shows an exploded view of the insertion tool with an integrated collet-clamp for insertion. 
     
    
       [0025]    Corresponding reference characters indicate corresponding components throughout the several views of the drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    The following description includes the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims.  
         [0027]    The present invention is a burr hole plug, an insertion tool, and a method for implanting the burr hole plug.  
         [0028]    As shown in FIG. 1, the burr hole plug has four main components: a shell  100 , a collet  200 , a clamp  300 , and a cover  400 . The burr hole plug, and its components, can be modified to match any shape or size of burr hole in the skull.  
         [0029]    [0029]FIG. 2 shows an alternate embodiment of the burr hole plug with four alternate main components: a shell  100 ′, a collet  200 ′, a clamp  300 ′, and a cover  400 ′. Shell  100 ′ and cover  400 ′ and their various alternate embodiments may be used with collet  200  and clamp  300  of FIG. 1 and their various alternate embodiments to form a number of alternate burr hole plug combinations. Similarly, shell  100  and cover  400  of FIG. 1 and their various alternate embodiments may be used with collet  200 ′ and clamp  300 ′ and their various embodiments to form a number of alternate burr hole plug combinations.  
         [0030]    As shown in FIG. 3, shell  100  forms the main part of the burr hole plug of FIG. 1 and is made from any hard biocompatible material such as titanium, stainless steel, other metals or alloys, or hard polymers. Shell  100  includes a flange  110 , at least two interlocking slots  120 , a locking base  130 , and a body  140 . An alternate embodiment of shell  100  has a side slot along the full length of shell  100 . This permits the alternate embodiment of shell  100  to be inserted into a burr hole after a medical device is inserted into the brain by sliding the body of the medical device through the side slot as the alternate shell  100  is moved into place.  
         [0031]    Flange  110  prevents shell  100  from being inserted deeper than the exterior surface of the skull. Flange  110  has a medical device exit  111  that secures the medical device and permits the medical device to gracefully exit the burr hole plug. Alternate embodiments of a medical device exit may include a similar structure such as a channel, hole, bump, tunnel, tube, or gate that secures the medical device and permits the medical device to exit.  
         [0032]    Shell  100  is either anchored to the skull, anchored to the skull and cover  400  of FIG. 1, or anchored to cover  400  of FIG. 1. Illustrative embodiments that enable anchoring follow. To anchor shell  100  to the skull, flange  110  includes at least one hole  112  capable of receiving at least one screw or similar anchoring device such as a fastener, pin, spike, tab, or button. Similarly, flange  110  may include, on its undersurface, anchoring structures such as at least one fastener, pin, spike, tab, or button that sinks into the skull where there is at least one corresponding hole (see FIGS. 4A and 4B). To anchor both cover  400  and shell  100  to the skull, a corresponding hole and anchoring device or a corresponding anchor on the undersurface of cover  400  engages with at least one hole  112  on flange  110 . To anchor cover  400  to shell  100 , flange  110  and cover  400  include at least one other hole (not shown) or at least one other anchoring arrangement using combinable structures such as at least one additional screw and a corresponding hole, at least one button that snaps into a corresponding hole, or at least one ball (see FIGS. 4A and 4B) that friction fits into a corresponding socket (see FIG. 9).  
         [0033]    Interlocking slots  120  permit clamp  300  (FIG. 1) to compress and lock collet  200  (FIG. 1) into shell  100 . Other structures capable of performing the same function may be substituted for interlocking slots  120 .  
         [0034]    Locking base  130  permits collet  200  (FIG. 1) to interlock with shell  100  and avoid rotation. Locking base  130  may include any structure or structures capable of locking collet  200  from rotating within shell  100  such as at least one tab, at least one notch, or at least one gear.  
         [0035]    Body  140  fits tightly against the inner surface of the circumference of a burr hole in the skull so as to avoid any movement of the burr hole plug in the burr hole after implantation. Additional fixation means or structures may be added to the exterior surface of body  140  to further prevent movement. These means or structures may include, e.g., a rough sandpaper-like surface, notches, or bumps (not shown). Further, vertical or horizontal ribs or threads (not shown) on the exterior surface of body  140  will help prevent rotation of the burr hole plug in the burr hole or vertical movement of the burr hole plug out of or into the burr hole.  
         [0036]    As shown in FIG. 4A, an alternate embodiment of shell  100 ′ of FIG. 2 employs balls  160  as part of the anchoring arrangement between the shell  100 ′ and cover  400 ′ previously described.  
         [0037]    As shown in FIG. 4B, the shell  100 ′ of FIG. 4A employs pins  170  as structures for anchoring shell  100 ′ to the skull as previously described.  
         [0038]    As shown in FIG. 5A, collet  200  of FIG. 1 is made from any hard biocompatible material such as titanium, stainless steel, other metals or alloys, or hard polymers. Collet  200  fits within shell  100  of FIG. 1 and secures a medical device exiting the brain through a burr hole. To secure a medical device, collet  200  includes at least one finger-like gripper  210  and may additionally include at least one cushion  220 . FIG. 5A shows four finger-like grippers  210  that, when compressed, centrally secure a medical device using radial force. Alternatively, one “C”-shaped finger-like gripper with a side slot along all or a portion of its length may compress upon itself to centrally secure a medical device using radial force (see FIG. 6). Similarly, one, two, three, five, and any other possible number of finger-like grippers compress upon itself or each other to centrally secure a medical device using radial force. Cushion  220 , although not essential to securing a medical device, helps stabilize the medical device within at least one finger-like gripper  210  and helps protect the medical device from damage. At least one cushion  220  is made from a soft biocompatible material such as a soft polymer like silicone rubber or an elastomer. At least one cushion  220  is attached to one or all of finger-like gripper(s)  210  and may be attached at any point on the inside or outside surface of finger-like gripper(s)  210  as long as cushion  220  intermediates finger-like gripper(s)  210  and the medical device at the point of pressure, which is most likely to be at an apex  221  of the collet  200 .  
         [0039]    As shown in FIG. 5B, collet  200  has an internal conical surface  230  defining an internal conical chamber, an external conical surface  240 , at least one side slot  250  along all or a portion of the length of collet  200 , and a locking base  260 . The internal conical chamber permits a medical device to exit the surface of the brain at any point in the burr hole and subsequently angle toward the apex  221  of the chamber where finger-like gripper(s)  210  secure(s) the medical device. At least one side slot  250  allows at least one finger-like gripper  210  to compress upon itself. Locking base  260  permits collet  200  to interlock with locking base  130  of shell  100  and avoid rotation. Locking base  260  includes any structure or structures capable of interlocking with locking base  130  such as at least one tab, at least one notch, or at least one gear, thus preventing collet  200  from rotating within shell  100 .  
         [0040]    As shown in FIG. 6, collet  200 ′ of FIG. 2 has a side slot  270  along the full length of collet  200 ′ allowing collet  200 ′ to mount and encircle a medical device at any point along the length of the medical device.  
         [0041]    As shown in FIG. 7, clamp  300  of FIG. 1 is made from any hard biocompatible material such as titanium, stainless steel, other metals or alloys, or hard polymers. Clamp  300  locks to shell  100  and compresses finger-like grippers  210  of collet  200 . Clamp  300  includes an internal conical surface  310 , a side slot  320 , at least two pins  330 , and holes  340  for engagement with insertion tool  900  (FIG. 10). Internal conical surface  310  engages with external conical surface  240  of collet  200 , thereby compressing finger-like grippers  210  as pins  330  are inserted into interlocking slots  120  of shell  100  and clamp  300  is rotatably locked into position on collet  200  and in shell  100 . Insertion tool  900  (as shown in FIG. 10) engages holes  340  to apply direction and rotational force to clamp  300  during locking. Any number of holes  340  or similar structures may be used to engage with a corresponding insertion tool. Pins  330  can be any similar structure capable of interlocking with interlocking slots  120  of shell  100  or similar structures. Pins  330  are preferably permanently spaced evenly apart in order to counterbalance each other, i.e., two pins are preferably spaced 180° apart, three pins are preferably spaced 120° apart, and so on.  
         [0042]    As shown in FIG. 8, plug cover  400  can be made from either a hard or soft biocompatible material such as titanium, another biocompatible metal, a hard polymer, a soft polymer, silastic, an elastomer, or any combination thereof. Cover  400  has an undercut  410  for sliding underneath flange  110  of shell  100 . Cover  400  also has a slot  420  for a medical device exit. Alternatively, a channel, hole, bump, tunnel, tube, gate, or similar structure may function as slot  420  to allow a medical device to exit. To anchor both cover  400  and shell  100  to the skull, at least one corresponding hole  430  and anchoring device or a corresponding anchor or other structure on the undersurface of cover  400  engages with at least one hole  112  or other structure on flange  110  of shell  100 . To anchor cover  400  to shell  100 , flange  110  and cover  400  may have at least one other hole (not shown) or at least one other anchoring arrangement using combinable structures such as at least one additional screw and corresponding hole, at least one button that snaps into a corresponding hole, or at least one ball that friction fits into a corresponding socket.  
         [0043]    An alternate embodiment of a cover is shown in FIG. 9 as cover  400 ′ of FIG. 2. Cover  400 ′ is made of a soft biocompatible material  450 , such as silastic. Cover  400 ′ has holes  460  for receiving anchors attached to shell  100 .- An alternate embodiment of a cover (not shown) has an exterior of soft biocompatible material and an interior of hard biocompatible material with anchors attached to the under side of the interior for engagement with the shell and/or skull.  
         [0044]    As shown in FIG. 10, an insertion tool  900  is used to implant a burr hole plug. Insertion tool  900  has a side slot  910  along its entire length to permit insertion tool  900  to mount and encircle a medical device at any point along its length. Interior conical surface  920  engages with exterior conical surface  240  to center collet  200  or collet  200 ′, while at least two ribs  930  engage with at least two slots  250  to rotate collet  200  or collet  200 ′ until locking base  260  of collet  200  or collet  200 ′ locks with locking base  130  of shell  100  or shell  100 ′. At least two pins  940  permit insertion tool  900  to engage with at least two holes  340  and lock clamp  300  or clamp  300 ′ into place by rotating insertion tool  900  and clamp  300  or clamp  300 ′ simultaneously. Ribs  930  and pins  940  are either on opposite ends of the same insertion tool  900  or are on separate tools. The body of insertion tool  900  need not be cylindrical, but can be take any size, shape, or form as long as it is constructed of a hard material such as stainless steel and has structures such as ribs  930  or pins  940  that are compatible with and capable of being engaged with collet  200 , collet  200 ′, clamp  300 , or clamp  300 ′.  
         [0045]    A method for implanting a burr hole plug includes a combination of the following steps in various orders so that the burr hole plug securely fastens and protects a medical device exiting the skull. Except when necessary, only the structures of the burr hole plug of FIG. 1 are described in the following method. However, this method also applies to the structures of the burr hole plug of FIG. 2 and all other embodiments of the present invention.  
         [0046]    A burr hole is created. Shell  100 , which is shaped and sized to form a dimensionally close press fit with the internal circumference or surface of the burr hole, is positioned and inserted by being pressed into the hole. If desired, shell  100  is fixed or anchored to the skull by small screws or other anchoring structures. The target site of the medical device in the brain is located, and the medical device is placed in the brain. To close the burr hole plug, collet  200  is carefully inserted into the opening of shell  100  and properly rotated using insertion tool  900  to an interlocking position with shell  100 . Clamp  300  is then carefully placed in shell  100  on collet  200  such that pins  330  align with interlocking slots  120  and clamp  300  is pressed and rotated using insertion tool  900  to an interlocking position with shell  100 . Compression and rotation of clamp  300  lock clamp  300  into shell  100  and restrain the medical device from further movement in the burr hole.  
         [0047]    During the process of closing the burr hole plug, the medical device is not exposed to pulling, pushing, or twisting forces that could cause an unwanted displacement of the medical device from its target site in the brain. The medical device is simply clamped from all directions through radial force from the collet. Plug cover  400  is placed on the top of the burr hole and attached securely by sliding undercut  410  under shell flange  110 , employing at least one anchoring arrangement described above.  
         [0048]    Alternately, plug cover  400 ′ is anchored to shell  100 ′ and/or the skull using at least one anchoring arrangement described above. Cover  400  or cover  400 ′ protects the medical device at the exit and prevents the medical device from fracturing.  
         [0049]    As shown in FIG. 11, shell  100  and collet  200 , or their corresponding alternate embodiments, are integrated either permanently, such as by a weld or combined mold, or temporarily, such as by adhesive with a weak bond, to form a shell-collet  500 . Integrated shell-collet  500  reduces the number of components for installation thereby reducing the number of steps needed in the insertion and closing procedure. The procedure of inserting a burr hole plug with an integrated shell-collet  500  is essentially the same as the procedure of inserting a burr hole plug with a separate shell  100  and collet  200  except that shell-collet  500  is inserted into the burr hole after the medical device is inserted into the brain. Integrated shell-collet  500  may have a side slot along its full length in order to permit shell-collet  500  to mount and encircle a medical device at any point along the medical device&#39;s length.  
         [0050]    As shown in FIG. 12, collet  200 ′ and clamp  300 ′ may be temporarily combined or integrated as by a weak adhesive bond  610  to form collet-clamp  600 . Integrated collet-clamp  600  reduces the number of components individually inserted by insertion tool  900  and thus reduces the number of steps needed during a burr hole closing procedure. When insertion tool  900  places collet-clamp  600  into shell  100 , locking base  260  of the collet portion of collet-clamp  600  is interlocked with locking base  130  of shell  100 , insertion tool and the clamp portion of collet-clamp  600  are rotated, and weak adhesive bond  610  between the collet and clamp portions is broken. When bond  610  is broken, individual collet  200 ′ remains in a locked position in shell  100 ′ or shell  100  and clamp  300 ′ is then rotatably locked against shell  100 ′ or shell  100  by engaging pins  330  of clamp  300 ′ with interlocking slots of shell  100 ′ or interlocking slots  120  of shell  100 . Similar weak adhesive, cohesive, magnetized, or other bonds placed prior to procedure may combine various components of the burr hole plug, i.e., shell  100 ′, collet  200 ′, clamp  300 ′, or cover  400 ′, with insertion tools for ease of use and implantation. After the components are placed in locked position, the bond will easily break, allowing an insertion tool to be removed.  
         [0051]    While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.