Abstract:
The present invention provides an anchor for securely positioning a catheter intended to deliver drug or other medicaments to a desired position in tissue wherever found in the body or in epidural or intrathecal space of a spinal cord or brain. The present invention comprises, in the preferred embodiment, a generally tubular body for receiving the catheter and a pair of wings to assist in securing the device. The body has a slot that extends through the body between the wings. The wings and the slot cooperate so that the opposed edges of the slot just come together as the wings are brought into contact with each other. The wings interact with the slot to radially compress the catheter within the lumen of the tubular body to hold the catheter in a fixed relation to the tubular body. In addition, the wings allow the device to be sutured to tissue to secure and fix the device to tissue. A first suture is placed around the base of the wings very near where the wings contact the body of the anchor. A second suture secures the wings together and affixes the anchor to the patient&#39;s tissue.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to the techniques for devices for delivering medicaments to selected sites in tissue. Specifically, this invention relates to an apparatus for securingly positioning a drug or medication delivering catheter after the catheter is positioned in the brain, spinal epidural space, the intrathecal space or in a peripheral nerve application or in other tissue. 
     2. Description of the Related Art 
     Medication delivery to the brain, spinal cord, cerebrospinal fluid or other tissue throughout the body is useful in treating many maladies, diseases and illnesses. Through the use of an implantable pump and catheter, precise drug doses can be directly delivered to the area of interest to treat the malady, disease or illness or its symptoms. 
     Controlled placement of drug delivering catheters in the position of interest is highly desirable. This allows highly concentrated drugs or other medicaments to be delivered to a specific site where, because the drug or medicament is highly concentrated, the therapeutic effect will be maximnized. Further, because only a small amount of such highly concentrated drug or medicarnent is needed at the site to be therapeutically beneficial, side effects from receiving relatively large doses of the drug orally or intravenously are minimized. 
     In view of the desirability of placing the highly concentrated drug or medicament at a specific site, movement of the catheter from its desired position is highly problematic. This is a problem known as “dislodgment”. Dislodgment means that the distal tip of the catheter is moved enough from its desired position for the therapy to be affected. For some therapies, for example, intrathecal administration of drugs to the spinal cord, movement on the order of 0.5 inch or less may cause a noticeable decrease in therapy. For others, such as when a catheter is implanted in the intrathecal space of the spinal cord, the catheter must exit the intrathecal space to cause a change in therapy. This can be as much as 8 inches. 
     It is rare for the anchor to move relative to the tissue it is attached to. It is much more likely for the catheter to move relative to the anchor (slip through). Where the catheter is implanted in the spine, an anchor is typically placed outside the spine and is anchored to a ligament. In this case, it is not uncommon for the catheter to exit the spine and “bunch up” just distal to the anchor between the anchor and the entrance to the spine. 
     Dislodgment causes the highly concentrated drug or other medicament to not be delivered to the desired location. As a result, the desired therapeutic effect is not achieved. In addition, applying the highly concentrated drug or medicament to another site may produce undesired effects. Therefore, dislodgment is a condition to be avoided. 
     There are currently several ways physicians attempt to solve the problem of dislodgment. One way is to suture the catheter to tissue to “anchor” the catheter to the tissue. A problem with this approach is that often the suture cuts through or occludes the catheter thereby disabling the catheter. This prevents the desired drug or medicament from passing to the distal end of the catheter to be delivered to the target site. In addition, the drug or medicament then leaks out of the cut area where it may possible cause undesirable effects. 
     Another way to solve the dislodgment problem is to place an “anchor” around the catheter and then secure the anchor to tissue. In this way, the anchor prevents the catheter from moving relative to the anchor and the anchor itself is prevented from moving relative to tissue because the anchor is securely fastened to the tissue. 
     An example of such an anchor is shown in FIGS. 1-4 labeled generally  2 . The anchor  2  has a tubular body  4  and a pair of opposed wings  6 . Body  4  has a central channel  8 . Central channel  8  is typically sized to be the same diameter as the outer diameter of a catheter  14  that is to be secured by the anchor  2 . Body  4  often has a longitudinal slit  10  that extends entirely through body  4  along the entire length of body  4 . 
     The wings  6  each have an eyelet  12 . In use, a catheter  14  is placed through slit  10  into channel  8 . Because of the tight tolerance in the diameter of central channel  8  and the outer diameter of catheter  14 , it is very difficult if not impossible to thread catheter  14  through channel  8 . Thereafter, anchor  2  is moved to the desired position. Wings  6  are pinched together toward slit  10 . A suture  16  is placed through eyelets  12  and tissue  18  to secure the catheter  14  in the anchor  2  and anchor  2  to tissue  18  (FIG.  4 ). 
     A problem with this design for anchor  2  is that as wings  6  are brought together, the material of body  4  develops hoop stresses. Hoop stresses are the stresses that develop as a tightening force is applied to a hoop and the hoop resists being inwardly compressed. In this case, the hoop is the cross-section of the body  4  of the anchor  2 . The tightening force is the application of force to the body  4  by bringing wings  6  together. These hoop stresses take a substantial amount of the energy provided by moving the wings  6  together and store it in tension within the material of body  4 . As a result, a seriously reduced amount of energy is available for contacting the outer surface of the catheter to cause frictional contact with the catheter to hold it in place with respect to the anchor  2 . 
     Another problem occurs because anchor  2  is placed in a pocket  20  formed in tissue  18  in a patient&#39;s body. A problem with this anchor  2  is that it is difficult bring the wings  6  from their 180° opposed position to their pinched position in the small opening provided by in the pocket in the tissue  18 . This problem is exacerbated when the surgeon also has to open slit  10  and place the catheter  14  in the central channel  8 . This is often accomplished by bending wings  6  together on the opposite side of body  4  so that slit  10  opens. This requires a very dexterous maneuver in the small space presented by the pocket  20  in the tissue  18 . Often, it takes several tries to get the catheter  14  positioned within central channel  8  through slit  10 . This complicates the surgery with the concomitant chance or problems or complications. 
     SUMMARY OF THE INVENTION 
     The present invention provides an anchor for securely positioning a catheter intended to deliver drug or other medicaments to a desired position in tissue wherever found in the body or in epidural or intrathecal space of a spinal cord or brain. The present invention comprises, in the preferred embodiment, a generally tubular body for receiving the catheter and a pair of wings to assist in securing the device. The body has a slot that extends through the body between the wings. The wings and the slot cooperate so that the opposed edges of the slot just come together as the wings are brought into contact with each other. In this way, hoop forces are virtually eliminated so that all the stress produced by bringing the wings together is applied to the catheter to frictionally hold the catheter in position within the anchor. The wings interact with the slot to radially compress the catheter within the lumen of the tubular body to hold the catheter in a fixed relation to the tubular body. 
     In addition, the wings allow the device to be sutured to tissue to secure and fix the device to tissue. A first suture is placed around the base of the wings very near where the wings contact the body of the anchor. A second suture secures the wings together and affixes the anchor to the patient&#39;s tissue. This suture is placed through an eyelet in each of the wings. In this way, the normal stresses applied to the catheter by bringing the wings together are maximized. 
     In use the catheter is placed in the central channel of the anchor. The wings are brought together and sutured. The wings are then sutured to the patient&#39;s tissue. 
     It is an object of the present invention to provide an anchor that securely holds a catheter without crushing, kinking,pinching or occluding the catheter. 
     It is another object of the invention to provide an anchor can be securely attached to a patient&#39;s tissue. 
     It is another object of the invention to provide an anchor that is easy to use. 
     The proposed design addresses these objects. Movement of the catheter relative to the anchor is greatly decreased because of the holding force provided as the wings are brought together and secured. Because the anchor is smaller and easier to place than known anchors, the physician should be able to place the anchor closer to the spinal entry site. This should make it unlikely that the catheter will pull out of the implant site and bunch up as the patient moves. 
    
    
     BRIEF DESCRIPTION OF TIE DRAWING 
     The preferred embodiment of the invention is illustrated in the drawing, wherein like reference numerals refer to like elements in the various views, and wherein: 
     FIG. 1 is a top view of a prior art catheter anchor. 
     FIG. 2 is an end view of the prior art catheter anchor of FIG.  1 . 
     FIG. 3 is a top view of the prior art catheter anchor of FIG. 1 in use. 
     FIG. 4 is a side view of the prior art catheter anchor of FIG. 1 in use. 
     FIG. 5 is a perspective view of the preferred anchor of the present invention. 
     FIG. 6 is a top view of the anchor of FIG.  5 . 
     FIG. 7 is an end view of the anchor of FIG.  5 . 
     FIG. 8 is a side cross-sectional view of the anchor of FIG.  5 . 
     FIG. 9 is an end view of the anchor of FIG. 5 in its closed position. 
     FIG. 10 is a perspective view of the preferred anchor of FIG. 5 ready to receive a catheter. 
     FIG. 11 is a perspective view of the preferred anchor of FIG. 5 with the catheter in place and the wings sutured together. 
     FIG. 12 is a perspective view of the preferred anchor of FIG. 5 in a cavity in a patient with the catheter in place, the wings sutured together and the anchor sutured to the patient&#39;s tissue. 
     FIG. 13 is a top view of an alternate embodiment of the anchor of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 5, a preferred embodiment of the medical catheter anchor is shown generally labeled  22 . Anchor  22  comprises a shell or sleeve  24  and a pair of wings  26 . Anchor  22  is preferably molded of silicone or any other flexible polymeric material such as urethane or other materials as will be clear to those skilled in the art. 
     Referring to FIGS. 5-8, the preferred sleeve  24  is essentially a cylindrical tube  28  that extends along a longitudinal centerline  30 . Tube  28  has a first end  32  and a second end  34  with a channel  36  extending through tube  28  from first end  32  to second end  34 . Channel  36  is preferably circular in cross-section and preferably is centered on the longitudinal centerline  30  of the tube  28 . Although this is the preferred embodiment, it is to be understood that other cross-sections could also be used as for example oval, “egg” shaped, square, rectangle, pentagon shaped, hexagonal, octagonal, to name but a few possibilities. Further, channel  36  may be located offset from the longitudinal centerline  30  of tube  28 . Channel  36  is defined by the inside surface  38  of tube  28 . In the preferred embodiment, the diameter of channel  36  is just slightly larger than the diameter of the catheter  14  that is intended to be secured by the anchor  22 . 
     In the preferred embodiment, first and second ends  32 ,  34  are tapered away from the center  40  of anchor  22  in tapered portions  42 . Tapering means that the diameter of the outer surface  44  decreases as the distance from center  40  increases. This tapering allows first and second ends  32 ,  34  to act as a strain relief for the catheter  14  placed therein as will be explained hereafter. 
     A slot  46  is preferably formed in the outer surface  44  between wings  26 . Slot  46  is preferably elongated in the direction of longitudinal centerline  30  and preferably extends from the outer surface  44  entirely through tube  28 . Slot  46  has side edges  48 , in an unstressed configuration, that form an angle to each other. As described hereafter, bringing wings  26  together causes the side edges  48  to come into full surface contact with each other. It is acceptable for side edges  48  to just barely touch each other. The key is for side edge  48  to not be compressed together so that hoop stresses are avoided. Side edges  48  define the side dimensions of slot  46 . 
     In an alternate embodiment shown in FIG. 13, a slit  50  extends through tube  28 . Slit  50  preferable extends radially from the longitudinal centerline  30 . Slit  50  allow the catheter  14  to be place in channel  36  by slightly deforming slit  50  to open and allow the catheter  14  to be passed through slit  50  into channel  36 . 
     A pair of wings  26  extend from the outer surface  44  of tube  28 . In the preferred embodiment, the angle between the wings  26  is about 90°. This configuration allows for ease of use by the surgeon as will explained hereafter. Further, this provides a smaller projected footprint for the device which allows the surgeon more room to work with the anchor  22  in the pocket  20 . 
     It is important that the wings  26  be sufficiently separated in the unstressed position so that as the wings  26  are brought together, there is sufficient stress generated to adequately frictionally hold the catheter  14  within the anchor  22 . Additionally, the angle between the wings  26  could exceed 90°. In fact, it is within the scope of this invention that the angle between wings  26  could be as large as almost 360° although angles larger than 180° would be difficult to work with by the surgeon. 
     Wings  26  include opposed sidewalls  52 . In the preferred embodiment, wings  26  extend substantially radially from outer surface  44  along radials from the longitudinal centerline  30 . Wings  26  are preferably substantially planar with the planes being substantially parallel to the longitudinal centerline  30 . As shown in FIG. 3, wings  26  preferably form an acute angle to each other. 
     In addition, the width “A” of wings  26  preferably exceeds about 30% of the total length “B” of the anchor  22 . (FIG. 8) With these ratios, the area of the anchor  22  that causes fixation to the catheter  14  is increased over previously know designs. The wider dimensions of width “A” combined with slot  46  allows a greater area within slot  46  to radially compress into contact with catheter  14  than would be possible with a narrower width “A”. 
     Further, the thicker “C” the wings  26 , the higher the stress levels that can be applied to the catheter  14 . But, patients and doctors prefer to have as small of an anchor  22  as is possible. So, if wings  26  combined are thicker than the outer diameter of the tube  28 , the anchor  22  will be larger than would be desirable. Therefore, it is most preferable that the width “C” be about equal to half the diameter of the tube  28 . (FIG. 7) In this way, the maximum stress can be applied to grip the catheter  14  without increasing the overall dimensions of the anchor  22 . 
     Wings  26  each have a suture eyelet  54  and a pair of opposed suture indents  56 . Suture eyelets  54  preferably extend entirely through wings  26  for a purpose that will be explained hereafter. Suture indents  56  extend into the sidewall  52  of wings  26  for a purpose that also will be explained hereafter. In the preferred embodiment, suture indents  56  are located as close to outer surface  44  as possible. This increases stress on the catheter  14  when a suture is applied as will be described hereafter. We have found that the normal stress between the catheter  14  and the anchor  22  is inversely proportional to the distance between the centerline of the catheter  14  and the location of the point where the wings  34  are fixed together. The friction between the catheter  14  and the anchor  22  is proportional to the normal stress between the catheter  14  and the anchor  22 . Friction is what holds the catheter  14  in a fixed relationship to the anchor  22 . 
     Although wings  26  are preferably substantially planar, they need not be so. Other configurations of wings  26  can be used. Whatever the configuration of wings  26 , wings  26  have three key functions. First, wings  26  cooperate with slot  46  to change the effective circumference of tube  28  to cause a radially compressive force on a catheter  14  when wings  26  are brought together. Second, wings  26  provide a means for securing the anchor  22  to tissue  18 . The use of wings  26  eliminated the need to suture the tube  28  directly to the tissue  18  with the concomitant possibility of cutting or occluding the catheter  14 . Finally, wings  26  are “handles” that allow the surgeon to grasp and manipulate the anchor  22 . 
     Catheters  14  are typically manufactured to specifications including the minimum radius about which the catheter  14  must bend without permanent change in shape, kinking or fracture. Where the catheter  14  exits the anchor  22  at the sleeve  24  at an angle to the longitudinal centerline  30 , as shown in FIGS. x and y, the tapered first and second ends  32 ,  34  are pliable and allow the first and second ends  32 ,  34  to deform slightly in the direction that the catheter  14  is going. This causes the first or second end  32 ,  34  to contour to the direction that the catheter  14  is going as it leaves the anchor  22 . In this way, the strain on the catheter  14  from deviating from the longitudinal axis is not concentrated at the point where the catheter  14  leaves first or second end  32 ,  34 , but is instead distributed over the entire tapered portion  42 . 
     In use, catheter  14  is threaded through anchor  22 . (FIG. 10) Catheter  14  is placed in central channel  36  by threading catheter  14  into either first or second end  32 ,  34 , passing catheter  14  through central channel  36  and out the respective other of first or second end  32 ,  34 . The present invention allows the tolerance between the catheter  14  and the inside surface  38  to be larger than with prior anchors so that the anchor  22  can slide down the catheter to the desired position. In the embodiment having a slit  50 , the catheter  14  can be placed in anchor  22  by opening slit  50  and placing catheter  14  into central channel  36  so that the longitudinal axis  54  of catheter  14  is coaxial with the longitudinal centerline  30  of tube  28 . 
     The wings  26  should be sutured together as shown in FIG. 11 by placing a suture  58  around the indents  56  and pulling the knot so that the wings  26  lie flat against each other. As wings  34  are pulled together, the side edges  48  of slot  46  come together. Preferably, just as the wings  34  come together, side edges  48  will come together. In this way, no hoop stresses will be present as wings  34  come together. As a result, virtually all the stress introduced into the anchor  22  by bringing wings  34  together will be applied to holding catheter  14  in frictional contact within anchor  22 . 
     Further, because side edges  48  meet only when wings  34  come together, there is no chance of “over-tightening” the anchor  22  so that material will be directed inwardly into contact with the catheter  14  to pinch, occlude or otherwise block catheter  14 . 
     In an unstressed configuration, tube  28  has a certain outer circumference. Slot  46  represents a discontinuity in the material in the circumference of tube  28  when tube  28  is in the unstressed configuration. When the side edges  48  are brought together into full surface contact, because the width of slot  46  is eliminated, the circumference of tube  28  will be smaller than when tube  28  is in an unstressed configuration. Because of the direct relationship between circumference and radius, as the circumference decreases, the radius decreases. If the radius of tube  28  when wings  26  are brought together is less than the outer radius of catheter  14 , then the inner surface  38  of tube  26  will apply compressive normal forces to the outer surface of catheter  14 . As a result, catheter  14  will be fixed with respect to the anchor  22 . 
     Slot  46  consists of material omitted from the tube  28 . As a result, as side edges  48  come together, no material will be deformed downward into undesired contact with catheter  14 . At this time, the inside surface  38  of tube  28  will be moved into gripping contact with the outer surface of catheter  14  to prevent catheter  14  from moving longitudinally with respect to anchor  22 . 
     If slot  46  were not present, as wings  26  are brought together, the space between wings  26  will be reduced. As a result, material in tube  28  between wings  26  would be “folded”. Part of this “folded” material would likely be moved into contact with catheter  14  which could pinch or occlude the catheter  14 . Although the preferred embodiment of the anchor  22  has a slot  46 , it is to be understood that the invention may also be practiced without slot  46 . 
     As mentioned above, the wings  26  are preferable at an acute angle to each other. This makes it easier to suture the wings together as described above because the wings  26  are closer together than they would be if the wings were 180° apart or more. 
     Finally, a suture  60  is fastened through the eyelets  54  and tissue  18  at the site of fixation to fasten the anchor  22  to the tissue  18 . (FIG. 12) In this way, anchor  22  is prevented from moving relative to the tissue  18  so catheter  14  is also prevented from moving relative to the tissue  18  by the interaction of catheter  14  with the anchor  22  and anchor  22  with the tissue  18 . 
     If the catheter  14  needs to be repositioned, the physician may remove sutures  58  and  60  and slide the catheter  14  to the new desired position. Then sutures  58  and  60  may be reattached as described above. 
     The invention has been described in connection with specific embodiments. Those skilled in the art will recognize that modifications can be made to the anchor  22  described herein without departure from the true spirit and scope of the invention. In addition, although the anchor  22  has been described in connection with securely positioning a catheter  14 , the anchor  22  may also be used to position a lead such as would be used for electrical stimulation of the nervous system or heart. 
     The true spirit and scope of the inventions of this specification are best defined by the appended claims, to be interpreted in light of the foregoing specification. Therefore, to particularly point out and distinctly claim the subject matter regarded as invention, the following claims conclude this specification.