Abstract:
A surgical snare is provided having an operating wire and an outer sheath having a lumen extending therethrough, wherein the operating wire is disposed within the lumen and is longitudinally movable within the lumen. The surgical snare also has a first locking member attached to the operating wire and a second locking member attached to the outer sheath. The first locking member is frictionally engageable with the second locking member by sliding the outer sheath longitudinally along the operating wire until the first locking member contacts the second locking member. The operating wire is prevented from moving longitudinally with respect to the outer sheath when the first locking member is frictionally engaged with the second locking member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present patent document claims the benefit of the filing date under 35 U.S.C §119(e) of Provisional U.S. Patent Application Ser. No. 62/169,287 filed Jun. 1, 2015, which is hereby incorporated by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates generally to medical devices, and more specifically to surgical snares. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    Medical devices of various shapes and sizes are commonly placed within patients to repair or assist in repairing damaged portions of the body. Often, these medical devices need to be removed from the patient at some point. For example, the patient may no longer need the medical device or the device is damaged and must be replaced. If these medical devices are not removed, they may cause harm to the patient, such as by causing infections or blockage in various body lumens. 
         [0005]    However, removing these medical devices from a patient by performing open surgery is not ideal. The cost and time, both to perform the surgery and for the patient to recover, are prohibitive. Additionally, these patients are often in weakened states and are thus more susceptible to additional complications from performing an unnecessary open surgery. 
         [0006]    Thus, minimally invasive techniques are preferable to performing open surgery. Frequently, a surgical snare is used to remove a medical device from a patient&#39;s body. Surgical snares are long, flexible devices that are inserted into a patient&#39;s body lumen. Generally, the distal end of the surgical snare uses some type of capture mechanism to secure the medical device to the surgical snare. Once the medical device is secured to the surgical snare, the surgical snare may be retracted from the patient&#39;s body, pulling the medical device with it. 
         [0007]    Surgical snares as currently designed have several disadvantages. Often, the snares require the constant use of both of the surgeon&#39;s hands to properly manipulate the snare and remove the medical device from the body. Using both hands can be cumbersome and can lead to accidental disengagement of the surgical snare from the medical device during the removal process since both hands may be needed to maintain the snare in a closed configuration about the medical device. Additionally, most surgical snares have large, clunky handles that the surgeon uses to manipulate the capture mechanism of the snare. In addition to being cumbersome, these handles also inhibit the introduction of a larger retrieval catheter over the surgical snare. Larger retrieval catheters are often required when attempting to extract large medical devices from a patient&#39;s body. 
       SUMMARY 
       [0008]    In one form of the present disclosure, a surgical snare is provided comprising an operating wire and an outer sheath comprising a lumen extending therethrough, wherein the operating wire is disposed within the lumen. Also, a frictional locking member is operably coupled to the outer sheath, wherein the frictional locking member prevents longitudinal movement of the operating wire with respect to the outer sheath when no external force is applied, but allows longitudinal movement of the operating wire within the outer sheath when an external force is applied. Additionally, the longitudinal movement of the operating wire with respect to the outer sheath may be prevented by frictional forces between the frictional locking member and the operating wire. The frictional locking member may comprise a helical wire wrapped around flexible tubing or a rigid tube comprising at least one crimp. The surgical snare may also have the operating wire comprise an expandable loop at a distal end of the operating wire. The surgical snare may also comprise a handle attached to a proximal end of the operating wire. The surgical snare may also comprise a retrieval catheter comprising a catheter lumen, wherein the outer sheath and frictional locking member are movably disposed within the catheter lumen. 
         [0009]    In another form of the present disclosure, a retrieval device is provided comprising a retrieval member, a tube comprising a channel therethrough, the channel receiving the retrieval member, and a fastening member operably coupled to the tube. Additionally, the fastening member frictionally engages with the retrieval member, thereby preventing longitudinal movement of the retrieval member along the channel of the tube when no external force is applied. The retrieval device may also comprise a handle attached to a proximal end of the tube. The retrieval device may also further comprise a catheter comprising a lumen, wherein the tube and the fastening member are disposed within the lumen. 
         [0010]    In still another form of the present disclosure, a method for retrieving a medical device is provided. The method comprises providing a surgical snare comprising an operating wire comprising an expandable loop at a distal end of the operating wire, an outer sheath comprising a lumen extending therethrough, the operating wire disposed within the lumen and longitudinally movable within the lumen, and a locking member operably coupled to the sheath. The method further comprises inserting the surgical snare into a patient&#39;s body with the expandable loop in a released state and feeding the surgical snare into the patient&#39;s body until the expandable loop is adjacent to the medical device. The method further comprises securing the expandable loop around the medical device by sliding the outer sheath along the operating wire until the expandable loop is in an engaged state, wherein the expandable loop has a smaller circumference while in the engaged state than when the expandable loop is in the released state. Further, the locking member frictionally engages the operating wire to thereby maintain the expandable loop in the engaged state without providing an external force. The method may further comprise retracting the surgical snare and the medical device from the patient&#39;s body. The method may alternatively comprise providing a retrieval sheath comprising a retrieval sheath lumen, feeding the retrieval sheath over the surgical snare by placing the surgical snare within the retrieval sheath lumen until the medical device is within a distal portion of the retrieval sheath lumen, and retracting the surgical snare and the medical device through the retrieval sheath lumen from the patient&#39;s body. 
         [0011]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0012]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0013]      FIG. 1  is a drawing of a surgical snare with an operating wire in a released state; 
           [0014]      FIG. 2  is a drawing of a surgical snare with an operating wire in an engaged state; 
           [0015]      FIG. 3  is a drawing of a surgical snare with a basket in a released state; 
           [0016]      FIG. 4  is a detailed view of one embodiment of the locking member; 
           [0017]      FIG. 5A  is a detailed view of another embodiment of the locking member; 
           [0018]      FIG. 5B  is a detailed view of another embodiment of the locking member; 
           [0019]      FIG. 6  is a detailed view of an alternative embodiment of the locking member; and 
           [0020]      FIG. 7  is a drawing of a surgical snare with a retrieval catheter. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. It should also be understood that various cross-hatching patterns used in the drawings are not intended to limit the specific materials that may be employed with the present disclosure. The cross-hatching patterns are merely exemplary of preferable materials or are used to distinguish between adjacent or mating components illustrated within the drawings for purposes of clarity. 
         [0022]      FIGS. 1 and 2  show a surgical snare  2 .  FIG. 1  shows the surgical snare  2  in a released or fully expanded (open) state, while  FIG. 2  shows the surgical snare  2  in an engaged or partially contracted (closed) state. The surgical snare  2  has an operating wire  4  and an outer sheath  6 . The operating wire  4  is ideally made of a flexible, compliant, biocompatible material such as, but not limited to, stainless steel. The outer sheath  6  is ideally made of a flexible, biocompatible material such as, but not limited to, teflon. A portion of the operating wire  4  is disposed within a lumen (not shown) of the outer sheath  6 , and the operating wire  4  is longitudinally movable within the lumen. An expandable loop  8  may be on the distal end of the operating wire  4 . A locking member  10  is operably coupled with the outer sheath  6 . In this embodiment, the locking member  10  is a tube with a channel through which the operating wire  4  is movably disposed. The locking member  10  may be fixedly attached to the outer sheath  6 . Alternatively, the locking member  10  may be disposed adjacent to a proximal end thereof, thus making the locking member  10  and outer sheath  6  individually slidable along the operating wire  4 . Additionally, the locking member  10  may be integrally formed with the outer sheath  6 , wherein the outer sheath  6  and locking member  10  are one piece. The surgical snare  2  may also include a handle  12 . The handle  12  may be attached to the operating wire  4  to assist the physician in manipulating the operating wire  4  relative to the outer sheath  6 . 
         [0023]    The surgical snare  2  can alternate between a released state ( FIG. 1 ) and an engaged state ( FIG. 2 ). When in the released state, the circumference of the expandable loop  8  is larger than when the surgical snare  2  is in the engaged state. The surgical snare  2  is changed from the released state to the engaged state by pushing the outer sheath  6  in a distal direction relative to the operating wire  4  while pulling the operating wire  4  in a proximal direction relative to the outer sheath  6 . As the outer sheath  6  and operating wire  4  are pulled in opposite directions, the distal end of the outer sheath  6  will reach the expandable loop  8 . A portion of the expandable loop  8  will eventually be pulled into the lumen of the outer sheath  6  and the expandable loop  8  will start to contract, thus decreasing the circumference. Eventually, as the outer sheath  6  and operating wire  4  continue to be pulled in opposite directions, the expandable loop  8  will contract to a point where the surgical snare  2  is in the engaged state as shown in  FIG. 2 . The surgical snare  2  is ideally in the engaged state when inserted into a body lumen to prevent the expandable loop  8  from damaging or catching on the walls of the body lumen. Alternatively, the expandable loop  8  may be retracted so that the entire expandable loop  8  is within a distal portion of the outer sheath  6 , thus minimizing any damage to the walls of the body lumen. 
         [0024]    Generally, during the engaged state the surgical snare  2  has captured a medical device  9  that is located within a patient&#39;s body.  FIGS. 1 and 2  show the medical device  9  as a small catheter, however the surgical snare  2  can be used to retrieve various other medical devices including, but not limited to, a feeding tube, pacemaker lead, and stent. Additionally, the surgical snare  2  may be used to capture and remove gall stones, kidney stones or other objects that must be removed from a patient&#39;s body. The surgical snare  2  then must remain in the engaged state as the medical device  9  is retracted from the patient&#39;s body. However, the expandable loop  8  is generally manufactured so that it tends to elastically revert back to the released state when no external forces are applied. Thus, as is the case with current surgical snares, if the physician loses the grip on either the operating wire  4  or the outer sheath  6 , the expandable loop  8  will automatically expand back to the released position and lose capture of the medical device  9 . To prevent accidental release of the medical device  9 , the present invention includes a locking member  10  to maintain the surgical snare  2  in an engaged state without the physician having to apply any forces to the operating wire  4  or outer sheath  6 . 
         [0025]    While the embodiment of  FIGS. 1 and 2  show an expandable loop  8  at the proximal end of the operating wire  4 , other devices well known in the art can be substituted for the expandable loop  8  including, but not limited to, a basket. As shown in  FIG. 3 , a basket  11  replaces the expandable loop  8  at the distal end of the operating wire  4 . Rather than a simple loop as shown with the expandable loop  8 , a basket  11  may have additional loops to ensure a more secure capture of the medical device  9 .  FIG. 3  shows the basket  11  with two loops; however additional loops with various shapes or patterns may be used to ensure a more secure capture of the medical device  9 . The basket  11  functions similarly to the expandable loop  8 . As the outer sheath  6  is moved distally relative to the operating wire  4 , the loops of the basket  11  contract, thus securing the medical device  9  within the basket  11 . 
         [0026]      FIG. 4  shows a detailed cross-sectional view of one potential embodiment of the locking member  10 . Several teeth or ridges  14  may extend into the channel  16  of the locking member  10 . These ridges  14  contact the operating wire  4  and apply a frictional force thereto that is sufficient to inhibit movement of the operating wire  4 . As described above, when the surgical snare  2  is in the engaged state, the operating wire  4  tends to revert back into the released state or the tension force applied by the snare will tend to naturally ease or loosen. However, the ridges  14  of the locking member  10  create a frictional force against the operating wire  4  that is great enough to prevent the operating wire  4  from moving relative to the outer sheath  6  once the handle is released by the user. Thus, the locking member  10  retains the surgical snare  2  in the engaged state without the physician having to maintain a constant grip on both the operating wire  4  and the outer sheath  6 . The locking member  10  allows the physician to capture and remove the medical device  9  from a patient&#39;s body without fear of losing capture during retraction of the surgical snare  2 . However, the frictional forces between the operating wire  4  and the locking member  10  are not so great as to prevent the physician from manually moving the surgical snare  2  between an engaged and a released state. When the physician applies an external force to the operating wire  4  and the outer sheath  6 , the locking member  10  will still permit the operating wire  4  to longitudinally move relative to the outer sheath  6 . The frictional forces need to be great enough to overcome the expandable loop  8  tending towards a released state, but not so great as to prevent intentional manipulation by the physician. 
         [0027]    While the ridges  14  shown in  FIG. 4  have jagged edges, other shapes can be used to create friction between the operating wire  4  and the locking member  10 . For example, rounded bumps may also be used. Additionally, the ridges  14  may be made of a variety of materials, including, but not limited to, compressible rubbers and pliable plastics such as silicone or PVC. Ridges  14  may also be created by placing compressible tubing into inner lumen of locking member  10  then installing crimps into locking member  10  to create desired friction between compressible tube and operating wire  4 . The ridges  14  may also be made of a tacky or adhesive material to increase the friction between the locking member  10  and operating wire  4 . The ridges  14  may be made entirely of an adhesive material, or the adhesive material may be coated on the surfaces of the ridges  14  that contact the operating wire  4 . 
         [0028]    While  FIG. 4  shows the locking member  10  with ridges  14  to create the friction between the operating wire  4  and the locking member  10 , any number of ways to create a sufficient amount of friction may be used.  FIGS. 5A and 5B  show two other exemplary embodiments of the locking member  10 .  FIG. 5A  shows a locking member  15  composed of three layers. The locking member  15  is generally tubular in shape with a channel through which the operating wire  4  runs. The inner layer of the locking member  15  is a first flexible tube  16 , preferably made of silicone, although other materials may be used. The middle layer is a wire  18  wrapped helically around the flexible tube  16 . The wire  18  is ideally made of a harder material, such as a biocompatible metal, although other materials may be used. The outer layer of the locking member  15  is a second flexible tube  20  that is used to confine the wire  18 . While the second flexible tube  20  is also ideally made of silicone, other materials may be used. The wire  18  provides ridges on the inner surface of the locking member&#39;s channel which contact the operating wire  4 . These ridges create friction between the operating wire  4  and the locking member  15 , thus achieving a similar locking result as described above. 
         [0029]      FIG. 5B  shows another potential locking member  22 . The locking member  22  is made of a hard, non-compliant material such as stainless steel, but other materials may be used. Several crimps  24  are created on the locking member that decreases the circumference of the lumen of the locking member in those regions. The decreased circumference in those areas causes increased contact between the locking member  22  and the operating wire  4 . The increased contact increases the frictional forces between the locking member  22  and the operating wire  4  which allows the surgical snare  2  to remain in the engaged state without applying any external forces. 
         [0030]    The locking member  10  does not need to be located at the proximal end of the outer sheath  6  as shown in  FIGS. 1 and 2 . For example, the locking member may instead be located at the distal end of the outer sheath  6 , or even in the middle of the outer sheath  6 . Additionally, the locking member  10  does not need to be a separate and distinct component from the outer sheath  6 . For example, the locking member  10  in  FIG. 4  may be removed from the surgical snare  2  and the ridges  14  may be placed within the lumen of the outer sheath  6 . Thus, the requisite frictional forces are still being created to prevent longitudinal movement of the operating wire  4  within the outer sheath  6 , while eliminating the need for a separate locking device. 
         [0031]    In the embodiments discussed above, the frictional forces created by the locking member  10  are similar when the surgical snare  2  is being released and when the surgical snare  2  is being engaged. However, the locking member  10  may be designed to apply differing frictional forces to the operating wire  4  when it is moved in different directions relative to the outer sheath  6 . In other words, the locking member  10  may be designed to have a uni-directional coefficient of friction. For example,  FIG. 6  shows a locking member  10  similar to the locking member  10  in  FIG. 4 . However, in this embodiment, the ridges  14  are resilient flaps angled in a proximal direction. With this design, the ridges  14  compress against the inside wall of the locking member  10  when the operating wire  4  is moved proximally relative to the outer sheath  6 . However, once proximal movement of the operating wire  4  ceases, the ridges  14  spring outwardly to engage the operating wire  4  and prevent distal movement, thus maintaining the surgical snare  2  in the engaged state without the physician applying any external forces. Designing the ridges  14  in this way lowers the friction between the operating wire  4  and the locking member  10  while the operating wire  4  is manipulated from the released state to the engaged state, thus allowing the physician to more easily manipulate the surgical snare  2  from the released state to the engaged state, while still maintaining the advantages of the automatic locking member  10 . 
         [0032]    While a constant diameter operating wire  4  is commonly used with surgical snares, a varying diameter operating wire  4  may also be used in the present invention. With a varying diameter operating wire  4 , a portion of the operating wire  4  may have a small enough diameter such that the locking member  10  will not cause a significant amount of friction between the locking member  10  and the operating wire  4 . The smaller diameter portion of the operating wire allows the surgical snare to be easily manipulated without the increased friction caused by the locking member  10 . However, the operating wire  4  may also have a larger diameter for a portion of its length that corresponds to when the surgical snare  2  is in the engaged state. Because this portion of the operating wire  4  has a larger diameter, it will engage with the locking member  10  and create the requisite frictional forces necessary to retain the surgical snare  2  in the engaged state. 
         [0033]    In some instances, a surgical snare alone is insufficient to successfully remove a medical device from a patient&#39;s body. For example, when a larger medical device, such as a pacemaker lead, needs to be removed from a patient&#39;s body, a retrieval catheter must be used in addition to the surgical snare  2  described above. In  FIG. 7 , a retrieval catheter  30  is shown with a lumen  32 . The retrieval catheter  30  is large enough to fit the entire surgical snare  2  within its lumen  32 . In practice, the retrieval catheter  30  is used in conjunction with the surgical snare  2 . First, as described in more detail above, the surgical snare  2  is inserted into the patient&#39;s body and manipulated so that the expandable loop  8  captures the medical device  9 . At this point, the retrieval catheter  30  is inserted over the surgical snare  2  and into the patient&#39;s body until the medical device  9  is within a distal portion of the lumen  32 . The surgical snare  2 , along with the medical device  9 , can then be retracted from the patient through the lumen  32  of the retrieval catheter  30 . The retrieval catheter  30  remains within the patient&#39;s body during the retraction process to provide a contained and secure passageway for the medical device  9  to be retracted. Often, body tissue has grown onto and about the medical device  9 . Thus, the retrieval catheter  30  may also include a cutting member on the distal end of the retrieval catheter  30  to disrupt or cut the tissue that has grown around the medical device  9 . The cutting member is typically tubular in shape with scallops or helical ridges about the outside of the cutting member. Alternatively, the retrieval catheter  30  may be inserted into the patient&#39;s body lumen prior to the surgical snare  2 . The surgical snare  2  can then be guided through the retrieval catheter&#39;s lumen  32  to where the medical device  9  is located. 
         [0034]    Without the assistance of the retrieval catheter  30 , there would be a greater risk of damage to body tissue as the medical device  9  is retracted. For example, a larger medical device may bump or scrape the walls of the body lumen from which it is being retracted. In addition to damage to the patient&#39;s body, this unwanted bumping and scraping may also cause the surgical snare  2  to lose capture of the medical device  9 . Thus a retrieval catheter  30  is often advantageous when extracting a medical device from a patient&#39;s body by using a surgical snare  2 . 
         [0035]    However, retrieval catheters are difficult to use with conventional surgical snares. Surgical snares often have large, bulky handles that allow the physician to manipulate the surgical snare with one or two hands. These larger handles cannot fit within the lumen of the retrieval catheter. Thus, the handles must be removed before inserting the retrieval catheter. During removal of the handle, the surgical snare might accidentally lose capture of the medical device. Additionally, the physician will eventually have to release the grip on either the outer sheath or the operating wire of the surgical snare as the retrieval catheter is inserted over the surgical snare. When the physician releases the grip, the surgical snare may once again lose capture of the medical device. The present invention eliminates these problems. The handle  12  and the locking member  10  can be designed to be low profile members with small circumferences, thus allowing the retrieval catheter  30  to be easily fed over the entire surgical snare  2  without needing to remove the handle  12 . Additionally, the automatic locking member  10  secures the surgical snare  2  in the engaged state without the physician having to maintain contact with the surgical snare  2 . Thus, the retrieval catheter  30  can be fed over the surgical snare  2  without fear of losing capture of the medical device  9 . In one example, the handle  12  may include a rigid tube that is crimped, or otherwise mechanically attached, to the operating wire  4  near the proximal end of the operating wire  4 . Alternatively, instead of using the handle  12  shown in  FIG. 7 , a larger, conventional handle can also be used with the present invention to increase the ease of use of the surgical snare  2 . This larger handle can be removable so as to allow the retrieval catheter  30  to be fed over the surgical snare  2  once the medical device  9  has been captured. 
         [0036]    The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.