Abstract:
A tubular medical device, such as an elongate catheter is provided. The catheter includes an anchor mechanism with two or more arms biased toward an expanded position and can be urged toward a narrower insertion position. Each of the two or more arms are fixed to the tube proximate a nonexpandable distal tip of the tube and to the central portion of the tube. A biasing member is disposed in conjunction with the anchor mechanism, the biasing member is connected to the tube at the central portion proximate to a position where the two or more arms connect to the tube and is also connected to the tube proximate to the distal tip. The biasing member urges the two or more arms toward the expanded position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Application No. 62/135,383 filed on Mar. 19, 2015, the entirety of which is hereby fully incorporated by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to catheters and methods of using the same, and more specifically, to a catheter for draining a body cavity. 
       BACKGROUND 
       [0003]    Catheters may be used for many purposes including draining fluids, such as urine or bile, from a body cavity. A drainage catheter may be inserted into the body through an orifice or the skin until it reaches a cavity in the body where fluid exists. Drainage catheters commonly have a proximal end portion and a distal end portion with an anchor at the distal end portion to secure the drainage catheter in the desired cavity in the body. These anchors can be referred to as a Malecot. Malecots are commonly used as a bladder or kidney anchoring mechanisms in urinary drainage catheters and nephrostomy tubes. 
         [0004]    This type of anchor is commonly made up of at least two wings or arms, which may be continuous with the rest of the catheter and may be made from the same material. These wings or arms are typically biased toward an expanded position, so that when no force is applied to the wings or arms, they can potentially hold the drainage catheter in place in a body cavity. While drainage catheters can be made of several materials, often, a thick-walled material must be used in order for the wings or arms to possess enough shape memory to function as an effective anchor. 
       SUMMARY 
       [0005]    A first embodiment of the disclosure is provided. The embodiment includes a drainage catheter with a Malecot-type anchoring mechanism and a spring that is incorporated into the Malecot-type anchoring mechanism. The drainage catheter may be a long narrow tube or shaft having an outer diameter and a smaller inner diameter. The drainage catheter may also have an inner lumen adapted to allow fluid to flow therethrough. The drainage catheter may also have a proximal end portion and a distal end portion. The drainage catheter may also be used in nephrostomy tubes, biliary drainage catheters, and urinary drainage catheters. 
         [0006]    At the distal end portion there may be a Malecot-type anchoring mechanism having a top portion and a bottom portion. The Malecot-type anchoring mechanism may also consist of a plurality of expandable wings or arms which are biased toward a first radially expanded open position and are moveable toward a second radially compressed insertion position. The Malecot-type anchoring mechanism may also comprise a spring that is connected to the top portion and the bottom portion of the Malecot-type anchoring mechanism. 
         [0007]    The spring may be biased toward a compressed position which may put an inward force on the Malecot-type anchoring mechanism so that the top portion and the bottom portion are urged toward one another and the plurality of expandable wings or arms are further urged in the first radially expanded open position. The spring may also be urged toward an expanded position by an external force to allow the Malecot-type anchoring mechanism to be moved toward a radially compressed insertion position. After the external force is removed, the spring may be formed from a superelastic material that will allow it to return to its original compressed position. Using a spring attached to the Malecot anchoring device, the drainage catheter can be made of a thinner walled catheter material and achieve the same Malecot shape memory as a thicker walled catheter material without a spring. 
         [0008]    Advantages of the disclosed devices will become more apparent to those skilled in the art from the following description of embodiments that have been shown and described by way of illustration. As will be realized, other and different embodiments are contemplated, and the disclosed details are capable of modification in various respects. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of a drainage catheter with the plurality of arms in a radially expanded open position. 
           [0010]      FIG. 2  is a close up perspective view of a Malecot-type anchoring mechanism in a radially expanded open position. 
           [0011]      FIG. 3  is a view of the inside of a tube or shaft of drainage catheter illustrating an inner and outer diameter. 
           [0012]      FIG. 4  is a perspective view of a drainage catheter with the plurality of arms in a radially compressed insertion position. 
           [0013]      FIG. 5  is another perspective view of a drainage catheter with the plurality of arms in a radially compressed insertion position. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Drainage catheters are designed to remove undesired fluids from body cavities such as the kidney and bladder. The drainage catheters may be a long narrow tube or shaft having an outer diameter and a smaller inner diameter. An anchoring mechanism may be provided at or proximate to the distal end portion of the tube. The anchoring mechanism may be a malecot having a plurality of expandable wings or arms that are biased toward an expanded position. The plurality of expandable wings or arms may be from an elastic material, such as a superelastic material that allows the material to return to its original shape after an external force has caused a deformation in the plurality of expandable wings or arms is removed. 
         [0015]    Sometimes, certain materials fail to return to their original shape after removal of an external force if the elasticity of the material is not strong enough initially or if the material has weakened over time. If the anchoring mechanism does not have a sufficient elasticity, it can often fail to effectively anchor the drainage catheter in place in a body cavity. If a material is too thick, it can cause complications with insertion and removal of the drainage catheter, which can also create a dangerous or uncomfortable situation for a patient. 
         [0016]    One embodiment of a typical drainage catheter  100  for use in draining fluids from a body cavity is depicted in  FIG. 1 . The drainage catheter  100  may include a long tube or shaft  300 , a proximal end portion  101 , a distal end portion  102  (with a distal tip  102   a ), with a central portion  103  disposed therebetween. A malecot-type anchoring mechanism  200  may be provided at the distal end portion  102  that may include a plurality of malecot arms  201 . The drainage catheter  100  may be adapted for insertion into a body with manipulation of the malecot-type anchoring mechanism  200 . The malecot arms  201  may each have a first end that extends from a portion of the tube  300  proximate to the distal tip  102   a  and a second end that extends from the central portion  103  of the tube. In some embodiments, the distal tip  102   a  of the tube may be nonexpendable, i.e. the diameter of the distal tip  102   a  remains substantially constant when malecot arms  201  are urged toward the insertion configuration (discussed above) and are allowed to return to the normal biased expanded configuration. 
         [0017]    The malecot type anchoring mechanism  200  may include a plurality of arms  201 , such as 2, 4, 6, 8, or any number of arms that may be appropriate for the necessary anchoring of the tube  100  in place (as will be readily understood or calculated by one of ordinary skill in the art with a thorough review of this specification and the clinical use of the device). The arms  201  may be formed to be biased into an extended position, and may be capable of being urged into a smaller insertion position. In some embodiments, the plurality of arms  201  collectively form an outer diameter that is significantly larger than the outer diameter of the central portion  103  of the tube  300  when the arms  201  are in the expanded position. For example, the outer diameter of the plurality of arms  201  in the expanded configuration may be referenced as a ratio of the diameter of the central portion of the tube  300 , and may be such ratios as 2:1, 3:1, 4:1, 5:1, 6:1, 8:1, and 10:1 (including all ratios in this range that are not whole numbers, e.g. 4.5:1) or other ratios that may be clinically suitable. One of ordinary skill in the art, after a thorough review of this specification will contemplate that other ratios may be possible and are within the scope of this disclosure. 
         [0018]    Turning now to  FIG. 2 , a view of the malecot-type anchoring mechanism  200  is provided. The Malecot-type anchoring mechanism  200  may include a bottom portion  210 , a top portion  220 , a plurality of expandable wings or arms  201 , and a spring  202 . In some embodiments, the spring  202  may be made of wire, which may be made from a non-corrosive material, and in some embodiments may be made from a superelastic material, such as nitinol. Opposite end portions  202   b,    202   a  of the spring  202  may be connected to the Malecot-type anchoring mechanism  200  at each of the top portion  220  and the bottom portion  210 , respectively. The connection of the spring  202  to the top portion  220  and the bottom portion  210  of the Malecot-type anchoring mechanism  200  may be made by wrapping the respective end portion  202   b,    202   a  of the spring  202  around the tube or shaft  300  of the drainage catheter  100  at the top portion  220  and the bottom portion  210  of the Malecot-type anchoring mechanism  200 . 
         [0019]    In one embodiment of the disclosure, the plurality of expandable wings or arms  201  may be biased toward a first radially expanded open position and may be moveable toward a second radially compressed insertion position with the arms  201  collectively compressed into an outer diameter that is less than the outer diameter when the arms  201  are in the expanded position. In some embodiments, when the arms  201  are compressed into the insertion position, the arms  201  collectively form the same outer diameter as the outer diameter of the central portion  103  of the tube  300 , or in other embodiments, the outer diameter of the arms  201  may be within 5, 10, 15, 20, or 25 percent of the outer diameter of the central portion  103 . 
         [0020]    In some embodiments, the plurality of expandable wings or arms  201  may be elastic and may be trained or configured to be urged toward the radially expanded open position due to the construction of the arms  201 . In some embodiments, the arms may be formed from polymers or plastics that may be formed with a biasing force toward the radially expanded open position. In some embodiments, the arms  201  may include a superelastic wire or wires that are trained to extend toward the radially expanded open position, such as after an external force that urged the arms  201  toward the insertion position is removed. 
         [0021]    The spring  202  also may be formed from an elastic material, such as superelastic material, such as nitinol including various alloys of nitinol. By connecting to the Malecot-type anchoring mechanism  200  at the top portion  220  and the bottom portion  210  of the spring, the spring  202  may be urged in compression (i.e. the spring  202  is biased to compress along its length), urging the top portion  220  and the bottom portion  210  toward one another. This biasing force of the spring  202  may further assist the plurality of expandable wings or arms  201  in returning toward their original positions after an external force that urged the malecot arms  201  to the insertion position is removed. 
         [0022]    As best shown in  FIG. 3 , which depicts the inside of the tube or shaft  300  of the drainage catheter  100 , the tube or shaft  300  may have an outer diameter  301  and an inner diameter  302  that is less than the diameter of the outer diameter  301 . A greater wall thickness, which provides for a greater distance between the outer diameter  301  and the inner diameter  302  may create a greater memory strength of the material out of which the tube or shaft  300  is made. In some embodiments, the plurality of expandable wings or arms  201  of the Malecot-type anchoring device  200  may be made of the same material as the tube or shaft  300  of the drainage catheter  100 . In other words, the expandable wings or arms  201  may have the same thickness as the remaining portions of the tube or shaft  300 . Therefore, an increase in tube thickness may create greater memory strength in the plurality of expandable wings or arms  201  of the Malecot-type anchoring mechanism  200 . 
         [0023]    One embodiment of a typical drainage catheter  100  for use in draining fluids from a body cavity in an insertion position is depicted in  FIG. 4 . This illustrates the plurality of expandable wings or arms  201  of the Malecot-type anchoring mechanism  200  being urged toward the second radially compressed insertion position by an external tension force F being applied to the tube  100 . As depicted, the external force F may urge the plurality of expandable wings or arms  201  of the Malecot-type anchoring mechanism  200  toward the second radially compressed insertion position from the first radially expanded open position. In other embodiments shown in  FIG. 5 , the malecot arms  201  may each be urged toward the compressed insertion position by locally compressing the arms  201 , such as with an external component disposed around the arms, the arms  201  being threaded through an external sheath  400 , and the hoop strength of the sheath  400  imparts a force that urges or compresses each of the arms  201  inwardly toward the insertion position. 
         [0024]    When the external force F is removed (or in other embodiments when the inward force upon the arms  201  is removed), the plurality of wings or arms  201  may return to or toward the first radially expanded open position based upon the outer biasing force of the arms  201  as further urged by the spring  202 . 
         [0025]    While the preferred embodiments of the disclosure have been described, it should be understood that the disclosure is not so limited and modifications may be made without departing from the invention. The scope of the invention is defined by the appended claims, and all devices that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein.