Patent Publication Number: US-11653942-B2

Title: Retrieval devices and related methods of use

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefits of priority of U.S. Provisional Application No. 62/137,556, filed on Mar. 24, 2015, the disclosure of which is herein incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     Various aspects of the present disclosure relate generally to retrieval devices and related methods. More specifically, the present disclosure relates to devices and methods for retrieving objects within a patient. 
     BACKGROUND 
     Retrieval devices are often used to remove organic material (e.g., blood clots, tissue, and biological concretions such as urinary, biliary, and pancreatic stones) and inorganic material (e.g., components of a medical device or other foreign matter), which may obstruct or otherwise be present within a patient&#39;s body cavities or passages. For example, concretions can develop in certain parts of the body, such as in the kidneys, pancreas, ureter, and gallbladder. Minimally invasive medical procedures may be used to remove these concretions through natural orifices, or through an incision, such as during a percutaneous nephrolithotomy (“PNCL”) procedure. Further, lithotripsy and ureteroscopy, for example, may be used to treat urinary calculi (e.g., kidney stones) in the ureter of a patient. 
     Retrieval devices may include end effectors for manipulating objects. Exemplary end effectors may have an open-end design or a closed-end design. For example, an end effector of the open-end design may have a plurality of arms that support a front loop through which an object may enter the end effector. After the end effector is closed around the object, the object may escape through the front loop under certain conditions. An exemplary end effector of the closed-end design may have difficulty capturing objects that are not positioned on a side of the end effector. Thus, there remains a need for retrieval devices with improved capabilities. 
     SUMMARY 
     Aspects of the present disclosure relate to, among other things, retrieval devices and related methods. Each of the aspects disclosed herein may include one or more of the features described in connection with any of the other disclosed aspects. 
     In one aspect of the present disclosure, a retrieval device may include a sheath having a distal end. The retrieval device may also include an end effector movable relative to the distal end of the sheath. The end effector may include first and second arms. The first arm may include a first opening at a distal portion of the first arm. The second arm may include a second opening at a distal portion of the second arm. The end effector may also include a third arm. The third arm may be slidably received in the first and second openings. A distal portion of the third arm may form at least part of a loop. The loop may extend through the first and second openings. 
     Aspects of the retrieval device may include one or more of the features below. The end effector may include a fourth arm slidably received in the first and second openings. Distal portions of the third and fourth arms may form the loop. The loop may be selectively expandable and contractible by sliding the third and fourth arms through the first and second openings. The third arm may be configured to slide through the first and second openings in one direction, and the fourth arm may be configured to slide through the first and second openings in an opposite direction, to selectively expand and contract the loop. The third arm may include a pair of proximal portions connected by a curved distal portion. The fourth arm may include a pair of proximal portions connected by a curved distal portion. The curved distal portion of the third arm may form one side of the loop, and the curved distal portion of the fourth arm may form an opposite side of the loop. The retrieval device may include a handle assembly configured to move the end effector relative to the distal end of the sheath. The end effector may be coupled to the handle assembly by a drive member. A first portion of the drive member may be formed by one of proximal portions of the first and second arms and a cable, a second portion of the drive member may be formed by a proximal portion of the third arm, and one of the first and second portions of the drive member may be movable relative to the other of the first and second portions of the drive member. 
     In another aspect of the present disclosure, a retrieval device may include a sheath having a distal end. The retrieval device may also include an end effector movable relative to the distal end of the sheath. The end effector may include a distal end. The end effector may also include an open end configuration, wherein first and second openings on first and second arms of the end effector receive a third arm of the end effector, and a distal portion of the third arm defines a central opening at the distal end of the end effector. The end effector may also include a closed end configuration, wherein a size of the central opening is reduced by the third arm drawing the first and second arms together at the distal end of the end effector. 
     Aspects of the retrieval device may include one or more of the features below. In the closed end configuration, distal ends of the first and second arms may be adjacent one another. In the closed end configuration, distal ends of the first and second arms may contact each other. The end effector may include a fourth arm. The first and second openings on the first and second arms of the end effector may receive the fourth arm of the end effector. A distal portion of the fourth arm may define at least part of central opening at the distal end of the end effector. In the open end configuration, curved ends of the third and fourth arms may define opposite sides of the central opening. Distal portions of the third and fourth arms may overlap at the distal end of the end effector. The end effector may be movable between an expanded state and a contracted state. The end effector may have the open end configuration in the expanded state and the closed end configuration in the contracted state. Distal tips of the first, second, third, and fourth arms may interlock with each other in the closed end configuration. 
     In another aspect of the present disclosure, a method of retrieving an object with a retrieval device may include maneuvering a distal end of a sheath of the retrieval device to a target area containing the object. The method may also include extending an end effector distally out of the distal end of the sheath. The method may also include expanding the end effector. The method may also include passing at least a portion of the object through an opening on the end effector. The opening may include a loop formed at least in part by distal portions of first and second arms of the end effector and a distal portion of a third arms of the end effector. The third arm may be received in first and second openings in the first and second arms. Alternatively, the opening may include a gap formed between the first and second arms, the first and third arms, and the second and third arms. The method may also include contracting the end effector around the object to exert a holding force on the object. Contracting the end effector may include reducing a size of the opening on the end effector. 
     Aspects of the retrieval device may include one or more of the features below. The end effector may be inherently biased to expand when extended distally out of the distal end of the sheath. Contracting the end effector may include retracting at least a portion of the end effector into the distal end of the sheath. Contracting the end effector may include retracting at least a portion of the third arm into the distal end of the sheath. Contracting the end effector may include bringing the distal portions of the first and second arms toward a central longitudinal axis of the end effector. Contracting the end effector may include bringing the distal portions of the first and second arms into contact by pulling at least a portion of the third arms in a proximal direction. 
     In another aspect of the present disclosure, a retrieval device may include a sheath having a distal end. The retrieval device may also include an end effector movable relative to the distal end of the sheath. The end effector may include a first arm, the first arm including a first opening at a distal portion of the first arm. The end effector may also include a second arm slidably received in the first opening, wherein a distal portion of the second arm forms at least part of a loop, and wherein the loop extends through the first opening. 
     It may be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary aspects of the present disclosure and together with the description, serve to explain the principles of the disclosure. 
         FIG.  1    is a schematic side view of a retrieval device including an end effector in an extended position and an expanded state, in accordance with aspects of the present disclosure. 
         FIG.  2    is a side view of the end effector of the retrieval device of  FIG.  1    in an intermediate state with the end effector in a partially extended/retracted position and a partially expanded/contracted state, in accordance with aspects of the present disclosure. 
         FIG.  3    is a side view of the end effector of the retrieval device of  FIG.  1    in a retracted position and a contracted state, in accordance with aspects of the present disclosure. 
         FIG.  4    is a side view of the end effector of the retrieval device of  FIG.  1    in the extended position and the expanded state, and near an object to be retrieved, in accordance with aspects of the present disclosure. 
         FIG.  5    is a side view of the end effector of the retrieval device of  FIG.  1    in a partially contracted/expanded state around the object, in accordance with aspects of the present disclosure. 
         FIG.  6    is a side view of the end effector of the retrieval device of  FIG.  1    in another partially contracted/expanded state around an object, in accordance with aspects of the present disclosure. 
         FIG.  7    is a side view of the end effector of the retrieval device of  FIG.  1    in another partially contracted/expanded state around an object, in accordance with aspects of the present disclosure. 
         FIG.  8    is a schematic side view of another retrieval device including an end effector in an extended position and an expanded state, in accordance with aspects of the present disclosure. 
         FIG.  9    is a side view of the end effector of the retrieval device of  FIG.  8    in an extended position and a contracted state, in accordance with aspects of the present disclosure. 
         FIG.  10    is a side view of the end effector of the retrieval device of  FIG.  9    in a retracted position and a contracted state, in accordance with aspects of the present disclosure. 
         FIG.  11    is a close-up view of a closed distal end of the end effector of the retrieval device of  FIG.  1   , with the end effector in a contracted state, in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     The present disclosure is drawn to retrieval devices and related and methods. Reference will now be made in detail to aspects of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. The term “distal” refers to a portion farthest away from a user when introducing a device into a patient. By contrast, the term “proximal” refers to a portion closest to the user when placing the device into the patient. 
     Exemplary Aspects 
       FIGS.  1 - 7    show aspects of a retrieval device  10 , with  FIGS.  4 - 7    showing the retrieval device  10  retrieving an object  12 . The retrieval device  10  may include an end effector assembly. According to one aspect, the end effector assembly may include an end effector  16  configured to engage the object  12 . The end effector assembly may also include a drive member  18  configured to move the end effector  16 . The end effector  16  may be selectively extended from and retracted into a distal portion of an outer sheath  42  by the drive member  18  for capturing and or releasing objects. 
     The end effector  16  may include arms  20 ,  24 ,  26 , and  28 . Arm  20  may include struts  21  and  22  that may be linked by a curved distal portion or end  32 . According to one aspect, the arm  20  may be composed of a single continuous member. Alternatively, the arm  20  may be composed of two or more wire segments joined together to form the curved end  32 . The single continuous member may include, for example, a wire having a U, teardrop, or petal shape. A gap between the struts  21  and  22  may decrease as the struts  21  and  22  extend proximally away from the curved end  32 . The wire may be made of a shape-memory material such that the wire may return to its original shape and/or maintain the gap in the absence of a deforming force. For example, the wire may be made of Nitinol. Additionally or alternatively, the wire may be treated to possess an internal bias causing the arm  20  to move radially outwardly away from a longitudinal axis of the end effector  16  in the absence of a constraining force. Alternatively, the wire may be formed of any suitable material including, but not limited to, metals, polymers, or a combination of materials. 
     The arm  28  may be similar to the arm  20 , and may include struts  29  and  30  that may be linked by a curved distal portion or end  34 . According to one aspect, the arms  20  and  28  may have the same material, dimensional, and/or shape characteristics. The arms  20  and  28  may form opposing sides of the end effector  16 . 
     The arms  24  and  26  may form other opposing sides of the end effector  16 . The arm  24  may include an opening, loop, or eyelet  36  at its distal end. The arm  26  may also include an opening, loop, or eyelet  38  at its distal end. The arms  24  and  26  may be made of wires. For example, at least one of the arms  24  and  26  may include a single wire bent at its distal end to form an eyelet. Alternatively, at least one of the arms  24  and  26  may include a wire with a ring secured to its distal end. Alternatively, each of the arms  24  and  26  may include a sheath (not shown), having a wire (not shown) extending therethrough. One length of the wire may extend through the sheath and out of a distal end of the sheath. Outside of the sheath the wire may be bent and inserted back into the distal end of the sheath, leaving part of the bent portion of the wire exposed. The exposed part of the wire may form an eyelet. The sheath may be made of any suitable material, including a polymer such as polyimide, or polyethylene terephthalate. 
     The arms  24  and  26  may be more rigid than the arms  20  and  28 . For example, the arms  24  and  26  may be made of the same material as the arms  20  and  28 , but the arms  24  and  26  may be made thicker than the arms  20  and  28 . Additionally or alternatively, the arms  24  and  26  may be made of a material having a higher stiffness coefficient than the material of the arms  20  and  28 . For example, the arms  24  and  26  may be made of stainless steel, while the arms  20  and  28  may be made of Nitinol. Additionally or alternatively, the arms  24  and  26  may be stiffened by enclosing each of them within a stiffening sheath (not shown). The arms  24  and  26  may possess an internal bias causing the arms  24  and  26  to move radially outwardly away from a longitudinal axis of the end effector  16  in the absence of a constraining force. 
     The arms  20  and  28  may extend through the eyelets  36  and  38  of the arms  24  and  26 . For example, the struts  22  and  30  may extend through the eyelet  38 , and the struts  21  and  29  may extend through the eyelet  36 . The curved end  32  may extend between the eyelets  36  and  38  on one side of the eyelets  36  and  38 . The curved end  34  may extend between the eyelets  36  and  38  on the opposite side of the eyelets  36  and  38 . As seen in  FIGS.  1  and  4   , the struts  21 ,  22 ,  29 , and  30  may curve toward the eyelets  36  and  38 . The curved struts  21 ,  22 ,  29 , and  30  may form opposing sides of the end effector  16 . The curved ends  32  and  34  may oppose each other and at least partially overlap, such that the curved ends  32  and  34  may form a front loop  40  of the end effector  16 . The front loop  40  may define a central opening therein. The arms  20  and  28  may be slidable through the eyelets  36  and  38  to change the curvature of the struts  21 ,  22 ,  29 , and  30 , to change distances between the struts  21 ,  22 ,  29 , and  30 , and/or to change a diameter of the central opening of the front loop  40 . 
     The end effector  16  may be movable between an extended position, where the end effector  16  is extended distally out of a distal end of the outer sheath  42 , and a retracted position, where the end effector  16  is withdrawn proximally into a lumen  44  of the outer sheath  42  through the distal end of the outer sheath  42 . The lumen  44  may extend longitudinally through the outer sheath  42 . The outer sheath  42  may include, for example, a hollow tube. The outer sheath  42  may be made of a polymer material. 
     In the extended position of the end effector  16 , the arms  20 ,  24 ,  26 , and  28  may expand radially outwardly into an expanded state, as shown in  FIGS.  1  and  4   . In the retracted position of the end effector  16 , the arms  20 ,  24 ,  26 , and  28  may contract radially inwardly into a collapsed or contracted state, as shown in  FIG.  3   . The end effector  16  may also be moved to partially extended/retracted positions, and/or partially expanded/retracted states, as shown in  FIGS.  2  and  5 - 7   . The end effector  16  may have an open end configuration in the expanded state and a closed end configuration in the collapsed or contracted state. 
     The drive member  18  may be used to move the end effector  16  relative to the outer sheath  42 . According to one aspect, proximal ends of the arms  20 ,  24 ,  26 , and  28  may be fixedly coupled to a distal end of the drive member  18 . For example, the drive member  18  may include a cable or flexible cylindrical member. 
     Alternatively, proximal portions of the arms  20 ,  24 ,  26 , and  28  may form at least part of the drive member  18 . According to one aspect, two or more proximal portions of the arms  20 ,  24 ,  26 , and  28  may be fixedly coupled, thus linking movement of those proximal portions. For example, proximal portions of the arms  20  and  28  may be fixedly coupled. Additionally or alternatively, proximal portions of the arms  24  and  26  may be fixedly coupled. It is also contemplated that proximal portions of the arms  20 ,  24 ,  26 , and  28  may all be fixedly coupled. 
     According to another aspect, two or more proximal portions of the arms  20 ,  24 ,  26 , and  28  may be uncoupled, allowing relative movement between those proximal portions. For example, proximal portions of the arm  20  and/or the arm  28  may be uncoupled from proximal portions of the arms  24  and  26 . Additionally or alternatively, proximal portions of the arms  20 ,  24 ,  26 , and  28  may all be uncoupled. Any combination of fixedly coupling and/or uncoupling of the proximal portions may be employed. For example, proximal portions of the arms  20  and  28  may be fixedly coupled, and proximal portions of the arms  24  and  26  may be fixedly coupled, while proximal portions of the arms  20  and  28  may be uncoupled from proximal portions of the arms  24  and  26 . Additionally or alternatively, proximal portions of the arms  20  and  28  may be uncoupled from each other and from proximal portions of the arms  24  and  26 , while proximal portions of the arms  24  and  26  may be fixedly coupled. 
     The retrieval device  10  may also include a handle assembly  45 . The handle assembly  45  may include a sheath control portion  46  and an end effector control portion  48 . The outer sheath  42  may be fixedly coupled to the sheath control portion  46 . The drive member  18  may be fixedly coupled to the end effector control portion  48 . One of the sheath control portion  46  and the end effector control portion  48  may be movable relative to the other. For example, the sheath control portion  46  may be moved distally relative to the end effector control portion  48 , or the end effector control portion  48  may be moved proximally relative to the sheath control portion  46 , to retract and contract the end effector  16 . The sheath control portion  46  may be moved proximally relative to the end effector control portion  48 , or the end effector control portion  48  may be moved distally relative to the sheath control portion  46 , to extend and expand the end effector  16 . The end effector control portion  48  may include one or more knobs, buttons, tabs, and/or any other suitable control structures (not shown) controlled by a user&#39;s hand or finger. 
     According to one aspect, when the drive member  18  includes one or more portions that are movable relative to one or more other portions of the drive member  18 , the end effector control portion  48  may be configured to move the relatively movable portions individually or as a group, to control movement of the end effector  16 . The end effector control portion  48  may include knobs, buttons, tabs, and/or any other suitable control structures (not shown), one such structure being fixedly coupled to, and configured to control, each of the proximal portions of the arms  20 ,  24 ,  26 , and  28  that is movable relative to any of the other proximal portions. It is contemplated that the control structures may be moved individually or in unison to manipulate the end effector  16 . For example, a part of the end effector control portion  48  may be coupled to proximal portions of the arms  20  and  28 , and another part of the end effector control portion  48  may be coupled to proximal portions of the arms  24  and  26 , such that the parts of the end effector control portion  48  may be relatively movable to move the arms  20  and  28  relative to the arms  24  and  26 . Additionally or alternatively, the end effector control portion  48  may include two parts, one coupled to the proximal portion of the arm  20  and the other coupled to the proximal portion of the arm  28 , such that the arms  20  and  28  may be relatively movable. The end effector control portion  48  may include any suitable number of parts for moving the arms  20 ,  24 ,  26 , and  28 . 
     A user may insert the distal portion of the retrieval device  10  into a patient and toward a target area within the patient containing an object the user wants to retrieve. For example, distal portions of the outer sheath  42  and the drive member  18 , and the end effector  16 , may be inserted directly into the patient and maneuvered to the target area. Alternatively, an introducer (not shown), such as a sheath or endoscope, may be inserted into the patient. The distal end of the introducer may be maneuvered to the target area. The retrieval device  10  may be inserted into a lumen of the introducer, maneuvered through the lumen, and at least partially extended from a distal end of the introducer into the target area. Alternatively, the retrieval device  10  may be pre-loaded into the introducer outside of the patient&#39;s body, such that the introducer and the retrieval device  10  may be inserted into the patient and maneuvered to the target area together. Maneuvering of the introducer and/or retrieval device  10  to the target area may be assisted by the use of any suitable visualization device, such as an imaging device at the distal end of the introducer. 
     During insertion of the retrieval device  10  into the patient, and/or maneuvering of the retrieval device  10  to the target area, the end effector assembly  16  may be in the retracted position and contracted state shown in  FIG.  3   . The reduced profile of the retracted and contracted end effector assembly  16  may make it easier to insert and maneuver the end effector assembly  16  through tortuous anatomy and/or small anatomical openings to the target area. The end effector assembly  16  may be retracted and contracted by moving the end effector control portion  48  proximally relative to the sheath control portion  46 . For example, beginning with the end effector  16  extended and expanded, as shown in  FIGS.  1  and  4   , moving the end effector control portion  48  proximally relative to the sheath control portion  46  may move the drive member  18  proximally relative to the outer sheath  42 , thus drawing a proximal portion of the end effector  16  into a distal end of the outer sheath  42 . As the end effector  16  is drawn into the outer sheath  42 , the end effector  16  may deform, as shown in  FIG.  2   . One or more of the arms  20 ,  24 ,  26 , and  28  may become straighter. The arms  20 ,  24 ,  26 , and  28  may move towards each other. The front loop  40  formed by the curved ends  32  and  34  may bend and/or fold. This may continue until the end effector  16  is housed within the outer sheath  42  in the manner shown in  FIG.  3   . 
     The distal end of the outer sheath  42  may be positioned near the object to be retrieved. The end effector  16  may be extended and expanded by moving the end effector control portion  48  distally relative to the sheath control portion  46 . The end effector  16  may, for example, move from the state shown in  FIG.  3    to the state shown in  FIG.  2   . As the end effector  16  is extended out of the outer sheath  42  the end effector  16  may expand radially outwardly due to its shape memory characteristics and/or inherent biasing. One or more of the arms  20 ,  24 ,  26 , and  28  may become more curved. The arms  20 ,  24 ,  26 , and  28  may move away from each other. The loop formed by the curved ends  32  and  34  may expand and/or flatten out. This may continue until the end effector  16  and the outer sheath  42  are expanded in the manner shown in  FIG.  1   . 
     The user may maneuver the end effector  16  to position the object  12  within the end effector  16 . With the end effector  16  extended and expanded, the front loop  40  may be at its widest diameter, and gaps between the arms  20 ,  24 ,  26  and  28  may be at their widest widths, facilitating entry of the object  12  into the end effector  16  through the front loop  40  or one of the gaps. In some instances, the entire object  12  may enter the end effector  16  ( FIG.  6   ). In other instances, only part of the object  12  may enter the end effector  16  ( FIG.  7   ). 
     The user may capture the object  12  in the end effector  16  by exerting a holding force on the object  12  using one or more parts of the end effector  16 . According to one aspect, the user may move the end effector control portion  48  proximally relative to the sheath control portion  46  to move the drive member  18  proximally relative to the outer sheath  42 , thus drawing the end effector  16  into the outer sheath  42 . As the end effector  16  is drawn into the outer sheath  42 , the end effector  16  may deform, as shown in  FIG.  5   . One or more of the arms  20 ,  24 ,  26 , and  28  may become straighter. The arms  20 ,  24 ,  26 , and  28  may move towards each other. The front loop  40  formed by the curved ends  32  and  34  may bend and/or fold. These movements may decrease the diameter of the front loop  40  and the widths of the gaps between the arms  20 ,  24 ,  26 , and  28 , limiting ways in which the object  12  may escape from within the end effector  16 . As withdrawal of the end effector  16  into the outer sheath  42  continues, the arms  20 ,  24 ,  26 , and  28  may forcibly engage the outer surface of the object  12 . The diameter of the front loop  40  may decrease until the front loop  40  closes, with eyelets  36  and  38  drawn together into close proximity or into contact, giving the end effector  16  a closed distal end as shown in  FIG.  6   .  FIG.  11    shows a close-up view (looking proximally from within end effector  16 ) of the closed distal end of  FIG.  6   . Tensile forces on the arms  20  and  28  may draw the reverse-bends of the arms  20  and  28  in opposite directions, bringing the reverse-bends toward each other. This movement of the arms  20  and  28  may draw the eyelets  36  and  38 , and the rest of the arms  24  and  26 , together. The closed distal end forms when further opposing movement of the reverse-bends of the arms  20  and  28  becomes obstructed by the portions of the eyelets  36  and  38  between the reverse-bends of the arms  20  and  28 . The reverse-bends of the arms  20  and  28  may exert clamping forces on the eyelets  36  and  38 , causing the reverse-bends of the arms  20  and  28  to interlock with the eyelets  36  and  38 . Additional tensile forces on the arm  20  may bring the struts  21  and  22  closer together, thus increasing the curvature of the reverse-bend of the arm  20 . Similarly, additional tensile forces on the arm  28  may bring the struts  29  and  30  closer together, thus increasing the curvature of the reverse-bend of the arm  28 . As such, the reverse-bends of the arms  20  and  28  and the eyelets  36  and  38  may forcibly engage to an even greater degree. 
     In some instances, the object  12  may only be partially within the end effector  16 , inhibiting full closing of the distal end of the end effector  16 , as will be described in more detail below with reference to  FIG.  7   . It is also contemplated that during retraction of end effector  16 , the distal end of the outer sheath  42  may exert a force on the object  12  and/or arms  20 ,  24 ,  26 , and  28 , further increasing the force of engagement between the object  12  and the arms  20 ,  24 ,  26 , and  28 . The user may then withdraw the retrieval device  10  from within the patient to remove the object  12  from the patient&#39;s body. 
     If part of the object  12  remains outside of the end effector  16  during its capture, at least some of the arms  20 ,  24 ,  26 , and  28  may still be used to capture the object  12 . For example, the front loop  40  may be positioned around an intermediate region of the object  12 . As the end effector  16  is drawn into the outer sheath  42 , the front loop  40  may fold ( FIG.  5   ) due to pivoting movement of the curved ends  32  and  34  about the eyelets  36  and  38 . The curved ends  32  and  34  may pivot to a point where the curved ends  32  and  34  and/or eyelets  36  and  38  may forcibly engage the intermediate portion of the object  12 . Continued movement of the end effector  16  into the outer sheath  42  may close the front loop  40  tighter around the intermediate portion of the object  12 , as shown in  FIG.  7   . The user may then withdraw the retrieval device  10  from within the patient to remove the object  12  from the patient&#39;s body. 
     The ability to move one or more of the arms  20 ,  24 ,  26 , and  28  individually may assist with capturing the object  12 . For example, the user may retract the arms  20  and  28  into the outer sheath  42  without retracting the arms  24  and  26  into the outer sheath. This may be possible when the drive member  18  includes proximal portions of the arms  20 ,  24 ,  26 , and  28 , and the end effector control portion  48  is configured to move the proximal portions of the arms  20  and  28  relative to the proximal portions of the arms  24  and  26 . As the arms  20  and  28  are retracted, the front loop  40  may fold along a line extending between the eyelets  36  and  38  ( FIG.  5   ) due to pivoting movement of the curved ends  32  and  34  about the eyelets  36  and  38 . The curved ends  32  and  34  may pivot to a point where the curved ends  32  and  34  may clamp onto an object like first and second jaws of a forceps. The user may have the ability to reposition the object to make it easier to fully capture the object with the end effector  16 . 
     Additionally or alternatively, as the arms  20  and  28  are retracted further into the outer sheath  42 , the curved ends  32  and  34  may and/or eyelets  36  and  38  may engage the object  12  with increased force. If part of the object  12  is situated within the front loop  40 , the curved ends  32  and  34  may forcibly engage the object  12  as shown in  FIG.  7   . The stiffness of the arms  24  and  26  may assist with holding the curved ends  32  and  34  such that the front loop  40  may be substantially planar and/or may extend substantially perpendicular to a central longitudinal axis of the end effector  16 , as the curved ends  32  and  34  engage the object. If the object  12  is within the end effector  16 , retraction of the arms  20  and  28  may bring the arms  20 ,  24 ,  26 , and  28  radially inwardly to engage the object  12 , and may close the front loop  40  such that the end effector  16  may be provided with the interlocked closed distal end as shown in  FIGS.  6  and  11   . This may allow the end effector  16  to capture the object  12  with at least a portion of the end effector  16  in the extended position. 
     It is also contemplated that one or more the arms  20 ,  24 ,  26 , and  28  may be moved individually during one stage of capturing the object  12 , and moved in unison with one or more others during another stage of capture of the object  12 . For example, the arms  20  and  28  may be retracted while the arms  24  and  26  remain extended during a first stage of capturing the object  12 . This may allow for capturing of the object  12  with the end effector  16  in an extended position. In some instances, retracting an end effector to initiate closing of the end effector around an object may cause the object to fall out of the end effector. Initiating closing of the end effector  16  around the object  12  prior to retracting the end effector  16  may reduce the likelihood of the object  12  falling out of the end effector  16  as closing of the end effector  16  begins. During a second stage, the arms  20 ,  24 ,  26 , and  28  may be retracted in unison, allowing the distal end of the outer sheath  42  to engage the arms  20 ,  24 ,  26 , and  28  to increase the holding force on the object  12 . 
     While retraction and contraction of the end effector  16  into the outer sheath  42  may assist with capturing the object  12 , extension and expansion of the end effector  16  after capturing the object  12  may facilitate release of the object  12  from the end effector  16 . Releasing the object  12  may be performed by moving the parts of the end effector  16  in the opposite direction of that which has been described above for capturing the object  12 . With the end effector  16  in the extended position and expanded state, the open front loop  40  may facilitate release of the object  12 , as would the gaps between the arms  20 ,  22 ,  24 , and  28 . 
       FIGS.  8 - 10    show aspects of a retrieval device  110  having an end effector  116  configured to engage an object (not shown), such as the object  12  depicted in  FIGS.  4 - 7   . The retrieval device  110  may also include a drive member  118  configured to move the end effector  116 . The end effector  116  may, for example, be selectively extended from and retracted into a distal portion of an outer sheath  142  by the drive member  118 . 
     The end effector  116  may include arms  120 ,  124 , and  126 . The arms  120 ,  124 , and  126  may form sides of the end effector  116 . The arm  124  may include a sheath  125 , and a wire  127  extending through the sheath  125 . One length of the wire  127  may extend through the sheath  125  and out of a distal end of the sheath  125 . Outside of the sheath  125  the wire  127  may be bent and inserted back into the distal end of the sheath  125 , leaving part of the bent portion of the wire  127  exposed. The exposed part of the wire  127  may form an opening, loop, or eyelet  136  at the distal end of the arm  124 . The sheath  125  may be made of any suitable material, including a polymer such as polyimide, or polyethylene terephthalate. The wire  127  may be made of stainless steel or Nitinol. The wire  127  may possess an internal bias causing the arm  124  to move radially outwardly away from a longitudinal axis of the end effector  116  in the absence of a constraining force. Additionally or alternatively, the sheath  125  may possess an internal bias causing the arm  124  to move radially outwardly. For example, a wall of the sheath  125  may include one or more struts or coils (not shown), to supply the internal bias. The arm  126  may include a sheath  129  and a wire  131  similar to the arm  124 . Alternatively, one or more of the arms  124  and  126  may be similar to the arm  24  or the arm  26 , in that it may be provided without a sheath. 
     The arm  120  may include a sheath  133  similar to the sheaths  125  and  129 . The arm  120  may also include a wire  135  similar to the wires  127  and  131 . The wire  135  and the sheath  133  may differ from the others in that the wire  135  may be selectively extended from and retracted into a distal portion of the sheath  133  by the drive member  118 . In  FIG.  8   , the wire  135  is shown in an extended and/or expanded state. The wire  135  may extend through the eyelets  136  and  138 , forming the front loop  140 . The wire may be slidable through the eyelets  136  and  138  to pull the arms  124  and  126  radially inward when the wire  135  is retracted into the distal portion of the sheath  133  ( FIGS.  9  and  10   ), and to permit the arms  124  and  126  to move radially outward when the wire  135  is extended out of the distal portion of the sheath  133 . In an alternative example, the arm  120  may include the wire  135  without the sheath  133 . In such an example, portions of the wire  135  at the proximal end of the end effector  116  may be capable of spreading apart to a greater degree than when the sheath  133  is present. 
     The end effector  116  may be movable between an extended position, where the end effector  116  is extended distally out of a distal end of the outer sheath  142 , and a retracted position, where the end effector  116  is withdrawn proximally into a lumen  144  of the outer sheath  142  through the distal end of the outer sheath  142 . The outer sheath  142  may be similar to the outer sheath  42  ( FIGS.  1 - 7   ). In the extended position of the end effector  116 , the arms  120 ,  124 , and  126  may expand radially outwardly into an expanded state, as shown in  FIG.  8   . In the extended and expanded state, the end effector  116  may have an open end configuration, and may facilitate movement of an object into or out of the interior of the end effector  116  via openings formed between portions of the arms  120 ,  124 , and  126 . The arms  120 ,  124 , and  126  may be drawn together into a contracted state while the end effector  116  is in an extended state, as shown in  FIG.  9   . In this extended and contracted state, the end effector  116  may have a closed end configuration, and may forcibly engage an object to keep the object in the interior of the end effector  116 . The arms  120 ,  124 , and  126  may also be contracted and retracted as shown in  FIG.  10   . Such a movement may enhance the force of engagement between the arms  120 ,  124 , and  126  and the object due to the contracting force exerted on the arms  120 ,  124 , and  126  by the outer sheath  142 . It should be appreciated that the end effector  116  may also be moved to partially extended/retracted positions, and/or partially expanded/retracted states. 
     It is contemplated that the closed end configuration of the end effector  116  may be reached when the loop  140  has been pulled so tight that the eyelets  136  and  138  are drawn adjacent to or into contact with each other, and further closure of the loop  140  is prevented by the portions of the eyelets  136  and  138  within the loop  140 . This leads to an interlocking of the eyelets  136 ,  138  and  140  that forms the closed end configuration. 
     In an alternative example, one of arms  124  and  126  may be omitted, leaving the end effector  116  with two arms (the second arm being the arm  120 ). Operation of the end effector  116  in this example may be similar to operation in the example where both of the arms  124  and  126  are present, in that the exertion of a tensile force on the wire  135  of the arm  120  may close the loop  140 , and bring the one of the arms  124  and  126  toward the arm  120 . 
     The drive member  118  may be used to move the end effector  116  relative to the outer sheath  142 . For example, proximal ends of the arms  120 ,  124 , and  126  may be fixedly coupled to a distal end of the drive member  118 . The drive member  118  may include, for example, a cable or flexible cylindrical member. In one exemplary configuration, proximal ends of sheaths  125 ,  129 , and  133 , and wires  127  and  131  may be fixedly coupled to the distal end of a first portion of the drive member  118 . Alternatively, wires  127  and  131  may be fixedly coupled to the distal ends of sheaths  125  and  129 . The proximal end of the wire  135  may be coupled to the distal end of a second portion of the drive member  118 , the second portion being uncoupled from the first portion, so as to allow wire  135  to move relative to sheaths  125 ,  129 , and  133 , and wires  127  and  131 . 
     The retrieval device  110  may also include a handle assembly  145 . The handle assembly  145  may include a sheath control portion  146  and an end effector control portion  148 . The outer sheath  142  may be fixedly coupled to the sheath control portion  146 . The drive member  118  may be fixedly coupled to the end effector control portion  148 . One of the sheath control portion  146  and the end effector control portion  148  may be movable relative to the other. For example, the sheath control portion  146  may be moved distally relative to the end effector control portion  148 , or the end effector control portion  148  may be moved proximally relative to the sheath control portion  146 , to retract and contract the end effector  116 . The sheath control portion  146  may be moved proximally relative to the end effector control portion  148 , or the end effector control portion  148  may be moved distally relative to the sheath control portion  146 , to extend and expand the end effector  116 . The end effector control portion  148  may include one or more knobs, buttons, tabs, and/or any other suitable control structures (not shown) controlled by a user&#39;s hand or finger. 
     According to one aspect, when the drive member  118  includes one or more portions that are movable relative to one or more other portions of the drive member  118 , the end effector control portion  148  may be configured to move the relatively movable portions individually or as a group, to control movement of the end effector  116 . For example, a part of the end effector control portion  148  may be coupled to proximal portions of sheaths  125 ,  129 , and  133 , and wires  127  and  131 , and another part of the end effector control portion  148  may be coupled to the proximal portion of the wire  135 , such that the parts of the end effector control portion  148  may be relatively movable to move the wire  135  relative to sheaths  125 ,  129 , and  133 , and wires  127  and  131 , to contract the end effector  116  and/or to allow it to expand. 
     Alternatively, a part of the end effector control portion  148  may be coupled to proximal portions of sheaths  125  and  129 , and wires  127  and  131 , and another part of the end effector control portion  148  may be coupled to the proximal portions of the sheath  133  and the wire  135 , such that the parts of the end effector control portion  148  may be relatively movable to move the sheath  133  and wire  135  relative to sheaths  124  and  129 , and wires  127  and  131 , to contract the end effector  116  and/or to allow it to expand. In such a configuration, it should be appreciated that yet another part of the end effector control portion  148  may be configured to move the wire  135  relative to the sheath  133  to expand and contract the loop  140 . In any of the configurations described above, the steps associated with using the end effector  116  to retrieve and release an object are similar to the steps described with respect to end effector  16 . 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed systems and processes without departing from the scope of the disclosure. Other aspects of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the features disclosed herein. It is intended that the specification and examples be considered as exemplary only.