Patent Publication Number: US-7717924-B2

Title: Medical retrieval device

Description:
CROSS-REFERENCE TO RELATED CASES 
   This is a continuation of U.S. application Ser. No. 09/588,373, filed Dec. 22, 1999, now U.S. Pat. No. 6,800,080 which is a continuation of U.S. application Ser. No. 09/084,135, filed May 22, 1998, and issued as U.S. Pat. No. 6,096,053, which is a continuation-in-part of U.S. application Ser. No. 08/642,756, filed May 3, 1996, and issued as U.S. Pat. No. 5,935,139. Also, U.S. Pat. No. 5,160,336 is incorporated herein by reference. 

   TECHNICAL FIELD 
   The present invention deals with a retrieval device for removing material from a body. 
   BACKGROUND INFORMATION 
   Biological material, such as stones, can reside at least in the kidney, ureter, or biliary duct. Stones can be extremely painful and require medical treatment. Removal of stones from the body has been accomplished by two methods in the past. The first method is stone removal through conventional surgery; a treatment with obvious disadvantages, risks and drawbacks. The second method is to remove stones under the guidance of an endoscope. In this method a grasping device is guided through the body tract to the site of the stone and is used to grasp and remove the stone under endoscopic guidance. Grasping devices which have been used in the past for the removal of stones include basket devices that have generally straight legs that bow outward from the center of the basket. 
   SUMMARY OF THE INVENTION 
   The invention provides a device and method for retrieval of material from a body. More particularly, the invention relates to a device and method for immobilizing a stone in the body with a basket of the device so the stone can be effectively fragmented and then allowing the stone and/or the pieces thereof to be removed via the basket which is formed, pursuant to the invention, of multiple, spiral-shaped, generally parallel, non-overlapping, and non-intersecting legs that are flexible and relatively closely spaced to each other (e.g., no more than about 2 mm apart). 
   The retrieval device of the invention includes the basket, a sheath movable relative to the basket, and a handle. The basket has spiral-shaped legs disposed around a central axis. The spiral-shaped legs have improved flexibility and moveability. In an intermediate section of the basket, the spiral-shaped legs are disposed substantially parallel to one another around the central axis. The legs do not intersect. Intersecting legs tend to restrain basket leg flexibility. 
   In one aspect, the invention relates to a device for retrieving material from a body. The device includes a sheath having a lumen extending therethrough and having a distal end. The device also includes a basket movable relative to the sheath from a retracted position in which the basket is withdrawn within the lumen of the sheath and an expanded position in which the basket is extended beyond the distal end of the sheath and open. The basket comprises a first portion and a second portion with two or more legs extending from the first portion to the second portion. The basket further comprises an intermediate portion between the first and second portions in which the legs are, when the basket is expanded, spirally arranged, substantially parallel, and non-intersecting. The intermediate portion of the basket is displaced radially outward relative to the first and second portions when the basket is in the expanded position. When in the expanded position, the basket can provide a support surface for the material when it is being fragmented, and it can further be used to capture the fragmented material. 
   Embodiments of this aspect of the invention can include the following features. For example, in one embodiment, the legs of the intermediate portion of the basket may be spaced about 0.0787 inches to 0.394 inches apart. In another embodiment, an elongate member may extend within the lumen of the sheath and may be operably attached to the basket such that movement of the elongate member relative to the sheath results in the basket moving between the expanded and retracted positions. 
   In another aspect, the invention features a method for fragmenting and retrieving material (e.g., a stone) from a body tract. This method involves inserting into a body tract a device such as the device described above. The method further includes immobilizing material in the body tract by moving the basket from the retracted position to the expanded position whereby the material is blocked, and then fragmenting the material in the body tract while using the expanded basket to limit movement of the material during fragmentation. The expanded basket can then be manipulated to capture at least some of the fragmented material within the basket. The captured fragmented material is then recovered from the body by withdrawing the device from the body tract. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of an expandable device according to the present invention. 
       FIG. 2  is a side view of the expandable device of  FIG. 1  deployed in a duct or tract or vessel of a body. 
       FIGS. 3 and 4  illustrate different configurations obtainable using the expandable device according to the present invention. 
       FIG. 5A  shows an end view of the expandable device according to the present invention. 
       FIGS. 5B and 5C  illustrate another embodiment of the present invention. 
       FIGS. 5D-5H  illustrate other embodiments of the present invention. 
       FIG. 6  illustrates one embodiment of the present invention wherein the expandable element is formed by embedding material in a sheath. 
       FIG. 7  illustrates another embodiment of an expandable device according to the present invention. 
       FIGS. 8A ,  8 B,  8 C and  8 D illustrate another embodiment of an expandable device according to the present invention in which the expanded diameter of the expandable element is variable. 
       FIG. 9A  illustrates another embodiment of the present invention in which the expandable element is formed in a guide wire with detachable proximal handles. 
       FIGS. 9B and 9C  illustrate another embodiment of the present invention in the form of a guidewire. 
       FIGS. 10A and 10B  illustrate another embodiment which is similar to that of  FIGS. 5B and 5C . 
       FIG. 10C  is an end-view of the basket in  FIG. 10B . 
       FIGS. 11A and 11B  illustrate another embodiment which is a variation of the embodiment shown in  FIGS. 8A-8D . 
       FIGS. 12A-E  illustrate the clinical application of the embodiment of the invention illustrated in  FIGS. 11A and 11B . 
       FIGS. 13A-B  illustrate another embodiment of the invention including the basket with spiral-shaped legs. 
       FIGS. 14A-E  illustrate a clinical application of the embodiment of the invention illustrated in  FIGS. 13A and 13B . 
   

   DESCRIPTION 
     FIG. 1  illustrates an expandable device  10  according to the present invention. In the embodiment shown in  FIG. 1 , expandable device  10  includes a sheath or catheter  12 , cannula  14  and mesh portion  16 . Catheter  12  preferably has, at its proximal end, a handle  18 . Cannula  14  is also provided, at its proximal end, with a handle  20 . 
   Catheter  12  is preferably made of commonly available materials which provide sufficient strength and springiness for adequate operation, but which are soft enough to avoid substantial trauma or irritation to the tract or duct in which catheter  12  is deployed. Materials which may commonly be used to form catheter  12  include polyethylene, nylons, Pebax, Teflon, urethanes, silicones, and other suitable polymer materials. The material is preferably biocompatable and inert to body fluids. 
   In the preferred embodiment, cannula  14  is a stainless steel tube or may simply be a solid wire or a coil which extends the entire length of catheter  12  and is connected to the interior of a distal tip  22 . Cannula  14  is axially movable within the lumen of catheter  12 . 
   Mesh portion  16 , in the preferred embodiment, is simply an expandable element which allows fluid flow therethrough and is preferably formed of a deformable mesh or net material, or of braided or woven fibers or metal wires, but can also be formed of a plurality of spirally arranged wires or fibers. The material is preferably formed of polymer fibers, such as nylon. In the embodiment in which mesh portion  16  is formed of a polymer mesh or netting material, the mesh size is preferably very small, and the holes in the meshing are on the order of several thousandths of an inch. It has been found that such a relatively tight mesh allows the passage of fluid therethrough, but does not allow any substantial particulate passage therethrough. In one preferred embodiment, a mesh net is formed wherein each strand of the mesh net is approximately 0.005 inches in diameter and the foramina in the net are several thousandths of an inch (e.g., 0.001 to 0.010 inches) across. 
   In the embodiment in which mesh portion  16  is formed of metal wires, the wires preferably comprise 0.006 inch diameter stainless steel wires. There are preferably at least three wires worked into overlapping spiral patterns. This is shown and discussed in greater detail with respect to  FIGS. 5B and 5C . 
   Mesh portion  16  is expandable in a radial direction by manipulating cannula  14  relative to catheter  12 . For instance, if cannula  14  is partially withdrawn from catheter  12  in the direction indicated by arrow  24 , tip  22  is drawn closer to sheath  12  thereby exerting a compressive force on mesh portion  16 . This causes mesh portion  16  to bulge outwardly in the radial direction. The further tip portion  22  is brought toward sheath  12 , the greater is the radial outward displacement of mesh portion  16 . 
     FIG. 2  illustrates expandable device  10  deployed in a duct or tract  26  of a body. Similar items are similarly numbered to those shown in  FIG. 1 .  FIG. 2  also shows an object, such as a kidney stone or a gall stone  28 , which resides in tract  26 . In order to remove stone  28 , expandable device  10  is used. 
   Expandable device  10  is first introduced (such as through a proper scope) into the duct in the retracted profile position shown in  FIG. 1 . After mesh portion  16  has been advanced to a desired point, preferably beyond stone  28 , and preferably under endoscopic observation or guidance, handle  20  of cannula  14  is withdrawn from catheter  12  in the direction indicated by arrow  24 . This causes tip  22  to move toward sheath  12  and thereby exert a compressive force or mesh portion  16 . Mesh portion  16  bulges radially outwardly. Handle  20  is withdrawn from catheter  12  until the diameter of mesh portion  16  reaches a desired dimension. Typically, this dimension roughly corresponds to the lumen dimension of tract  26  so the outer periphery of mesh portion  16  contacts the inner periphery of tract  26 . Mesh portion  16  thus provides a backstop, or immobilization surface, for stone  28 . 
   After being so deployed, another instrument, such as a ballistic jack hammer-type instrument, a laser, or other treatment device  29 , is inserted closely adjacent stone  28  and is used to break stone  28  into fragments. Mesh portion  16  provides a relatively rigid-backstop so that a large amount of the force imparted on stone  28  is absorbed by stone  28  and is actually used in breaking stone  28 , rather than being dissipated in the backstop material. It should also be noted that mesh portion  16 , when in the expanded position shown in  FIG. 2 , provides a substantially disk-shaped object supporting surface which is used to support stone  28 . This leaves the vast majority of the surface of stone  28  accessible by the instrument being used to break stone  28 . 
   Once stone  28  is broken into pieces or fragments, those fragments are removed in any number of suitable ways. For instance, baskets can be deployed to remove the fragments. However, expandable device  10  is also useful in removing the fragments, or in sweeping the tract  26 . Once stone  28  is broken into fragments, mesh portion  16  is preferably maintained in the expanded position and expandable device  10  is withdrawn from tract  26 . Since mesh portion  16  is formed of a mesh size which allows fluid flow therethrough, but which does not allow any substantial particulate flow therethrough, this has the effect of sweeping tract  26  substantially clean of stone fragments. 
   Mesh portion  16  can also be formed to assume a substantially predetermined configuration upon being expanded. For example, the fibers in a woven mesh or net can be woven such that, when the compressive force is exerted on mesh portion  16  by sheath  12  and tip  22 , the resultant expansion yields a predetermined configuration. Further, where mesh portion  16  is formed of heat-settable or other suitable polymer materials, those materials can be heat-set or thermoset so that they obtain a predetermined configuration upon expansion. 
     FIGS. 3 and 4  illustrate two preferred predetermined configurations. In  FIG. 3 , mesh portion  16  is expanded to assume a substantially concave configuration relative to tip  22 . This, in some instances, is beneficial or advantageous such as when expandable device  10  is used to sweep or filter a duct or tract  26 .  FIG. 4  illustrates that mesh portion  16  assumes a substantially convex shape relative to tip  22 . This is beneficial when expandable device  10  is used in removing stones from a duct or tract  26 . For instance, in certain instances, stones can become impacted in the side tissue of a duct or tract  26 . In such an instance, the shape of mesh portion  16  shown in  FIG. 4  is useful in scraping or digging the stones out of the tissue defining the duct or tract. It should be noted, however, that in both  FIG. 3  and  FIG. 4 , the shape assumed by mesh portion  16  is only a fairly shallow dish or bowl shape. This allows mesh portion  16  to provide a stone supporting or immobilization surface which still allows a great deal of access to the surface of stone  28 . Therefore, if a device is introduced to break stone  28 , access to stone  28  is substantially uninhibited by mesh portion  16 . 
     FIG. 5A  illustrates an end view of mesh portion  16  when deployed in its expanded position.  FIG. 5A  shows that the preferred configuration of mesh portion  16  is substantially circular, or is a shape which is suitable to substantially conform to the interior of the duct or tract  26  in which mesh portion  16  is being deployed. 
     FIG. 5B  illustrates mesh portion  16  formed of a plurality of spirally arranged wires or fibers.  FIG. 5C  illustrates the shape of mesh portion  16  in the expanded position. 
     FIGS. 5D ,  5 E,  5 F,  5 G and  5 H also show alternative predetermined shapes for mesh portion  16  in the expanded position.  FIG. 5D  shows a generally spherical shape.  FIG. 5E  shows a substantially square or rectangular box shape and  FIG. 5F  shows a pyramid or cone shape which can have a substantially square or curved base cross-section.  FIGS. 5G and 5H  show a hemispherical shape directed toward, and away from, lip  22 . All of these shapes of mesh portion  16  can have concave or convex surfaces, as desired, and can be made of mesh netting, woven or braided fibers or wires, or any other suitable materials. Any other suitable shapes can also be used. 
     FIG. 6  is a cross-sectional view of another embodiment of expandable device  10 . In some applications of expandable device  10 , the outer diameter of expandable device  10  is crucial. In such applications, it is advantageous to provide mesh portion  16  embedded within the material defining catheter  12 . When using this embodiment, no separate means are required to attach mesh portion  16  to the outer or inner surface of sheath  12 . Therefore, any radial dimension which is added by such Attachment means is eliminated. 
     FIG. 6  shows that mesh portion  16  is formed of a mesh material which runs substantially the entire length of catheter  12  and is embedded therein. This can be accomplished by a multiple-extrusion process in which an inner first layer of the material forming catheter  12  is extruded, mesh material forming mesh portion  16  is disposed on the first extrusion, and then a second extrusion of material forming catheter  12  is performed to cover mesh portion  16  in all areas except where it is desired that mesh portion  16  be radially expandable. It should also be noted, however, that mesh portion  16  can be embedded in the material forming catheter  12  by simply taking a shorter length of mesh portion  16  and melting it into the wall of catheter  12 . 
   In other applications, mesh portion  16  is simply secured to sheath  12  using commonly known bonding methods for metals and plastics such as ultrasonic welding or adhesives. 
     FIG. 7  shows another embodiment of expandable device  10  according to the present invention. In  FIG. 7 , expandable device  10  is provided with two mesh portions  16 A and  16 B. Each of mesh portions  16 A and  16 B is formed substantially the same as mesh portion  16  described with respect to  FIGS. 1-6 . However, mesh portions  16 A and  16 B are separated by a spacer  30 . In the preferred embodiment, spacer  30  is formed of the same material as catheter  12  and is simply a generally tubular member disposed between mesh portions  16 A and  16 B. In such an embodiment, retraction of cannula  14  relative to catheter  12  causes a compressive force to be exerted both on mesh portion  16 A and mesh portion  16 B, through spacer  30 . This causes both mesh portions  16 A and  16 B to expand radially outwardly. In the embodiment shown in  FIG. 7 , mesh portions  16 A and  16 B, when expanded, provide generally opposing object support surfaces which are shown capturing or supporting a stone  28  therebetween. Of course, any appropriate expanded configuration can be obtained with mesh portions  16 A and  16 B. Further, two wires such as cannula  14  can be provided to accomplish independent expansion of mesh portions  16 A and  16 B. While  FIG. 7  shows mesh portions  16 A and  16 B simply trapping and holding stone  28  it should be noted that it is still possible to place an end effectuating device closely adjacent one of the mesh portions  16 A and  16 B to treat stone  28  through the mesh portion. 
     FIGS. 8A-8D  illustrate yet another embodiment of the present invention. In  FIGS. 8A-8D , expandable device  10  is disposed within a movable outer catheter sheath  32 . Outer sheath  32  preferably extends for a major portion of the length of expandable device  10  and is axially slidable along the outer periphery of expandable device  10 . Outer sheath  32  is preferably formed of a material similar to sheath  12  and has, disposed at its proximal end, a handle  34 . However, outer sheath  32  may be only a relatively short sheath (on the order of the axial length of mesh portion  16 ) having its axial movement controlled by other means (other than handle  34  such as a control wire or a coil. Sheath  32  can be manipulated relative to expandable device  10  to obtain a desired, and controlled, radial expansion of mesh portion  16 . 
   In the embodiment shown in  FIG. 8A , mesh portion  16  has an overall axial length L 1 . When outer sheath  32  is placed so that its distal end  36  is coterminus with the distal end of catheter  12  (as shown in  FIG. 8A ) the entire length L 1  of—mesh portion  16  is available for expansion. Therefore, when cannula  14  is withdrawn relative to catheter  12 , and when tip  22  and the distal end of catheter  12  exert a compressive force on mesh portion  16 , mesh portion  16  is free to expand throughout its entire length. This results in an expanded configuration, such as that shown in  FIG. 8B , which has a diameter d 1 . 
   However, where it is desired that the diameter of the expanded portion be reduced, outer sheath  32  is moved axially relative to expandable device  10  to cover a portion of mesh portion  16 . This is shown in  FIG. 8C . Therefore, with outer sheath  32  deployed as shown in  FIG. 8C , a smaller part of mesh portion  16  (having length L 2 ) is available for radial, expansion. When cannula  14  is withdrawn relative to catheter  12  to cause mesh portion  16  to expand, the expanded configuration obtained by mesh portion  16  has a diameter d 2  (shown in  FIG. 8D ) which is smaller than the diameter d 1  (shown in  FIG. 8B ). of course, the diameter of the expanded configuration of mesh portion  16  can be continuously varied simply by varying the degree to which outer sheath  32  overlaps, and thereby constrains the expansion of, mesh portion  16 . Sheath  32  could also be located distally of mesh portion  16  and pulled over mesh portion  16 , and pushed to expose mesh portion  16 . 
     FIGS. 9A-9C  show yet another preferred embodiment of the present invention. In the embodiment shown in  FIG. 9A , expandable device  40  is formed, in large part, as a conventional guide wire. Expandable device  40  includes an outer sheath  42  (which is often a coil) and an inner core  44  which is coupled at a distal tip  45  to outer coil  42 . As with conventional guide wires, inner core  44  is movable relative to outer coil  42 . However, unlike conventional guide wires, outer coil  42  is also provided with mesh or expandable portion  46 . In the embodiment shown in  FIG. 9A , mesh portion  46  is formed of braided fibers or wires or of mesh netting material. In another preferred embodiment shown in  FIGS. 9B and 9C , mesh portion  46  can simply be comprised of straightened or substantially linear wires which, when inner core  44  is withdrawn relative to coil  42 , bulge outwardly to form an object supporting surface for supporting an object (such as a stone) in a body tract.  FIG. 9C  shows an end view of the mesh portion  46  of  FIG. 9B  in the expanded position. 
   For expandable device  40  to operate both as a guide wire, and as an expandable device, the proximal end  48  of expandable device  40  is provided with removable handles  50  and  52 . Handle  50  is preferably a snap-on handle which can be releasably secured about the outer periphery of outer coil  42 . In addition, handle  52  is preferably a handle which can be releasably secured about the outer periphery of inner core  44 . 
   The present invention will preferably be formed with one of any number of outer diameters, but will most commonly have an outer diameter of 1.5 French to 10 French. In addition, the total length of the mesh portion will have any suitable dimension, but is preferably approximately 1-3 cm in length. 
   While it has been disclosed that the mesh portion of the present invention is expanded to immobilize stones or objects to prevent migration of those objects during various therapies, the present invention can also be used to manipulate or remove such objects. However, immobilization is typically used during pneumatic, mechanical, electrical, hydraulic, laser, or other forms of treatment of the stone. Further, it should be noted that the wires or fibers forming mesh portion  16  can have any suitable crosssection, such as flat wires, round wires or whatever is deemed appropriate. Since a low profile device is preferred in some applications, mesh portion  16  will be formed using as few wire crossovers (if any) as practicable in such applications, while still Maintaining desired stiffness for an adequate backstop. 
   Further, the present invention can be implemented in a multi-lumen catheter which can be used to deliver fluids, such as contrast fluid, saline-flushing fluid or caustic fluid which helps to break down the stone. 
   In another aspect of the invention, referring to  FIGS. 10A-B , an expandable retrieval device  10  comprises a sheath  12 , a basket  60 , a cannula  14 , and a handle  20 . The basket  60  has a first basket portion  11 , a second basket portion  13 , and an intermediate basket portion  15  interposed between the first basket portion  11  and second basket portion  13 , as also shown in  FIGS. 11A and 11B . The basket  60  can be placed in a radially-expanded position, as shown in  FIGS. 10A ,  10 B,  11 B, and  13 B and a retracted position, as shown in  FIGS. 11A and 13A . 
   As illustrated in  FIG. 10B , the basket  60  is comprised of multiple spiral-shaped parallel legs  17  disposed around a central axis of the basket in the intermediate portion  15 . The legs  17  are non-intersecting. The legs  17  begin forming the basket  60  at the first portion  11  and end at the second portion  13 . In the disclosed embodiment, the legs  17  are twelve wires that extend within the cannula  14 . Other member of legs are possible such as 3, 4, 5, 6, etc. In general, the basket  60  has two or more legs, and preferably three or more. The basket legs may be made from stainless steel, nitinol or plastics. As shown in  FIG. 10C , an end-view of the basket  60  comprises a star configuration. 
   In the disclosed embodiment, each of the parallel spiral-shaped legs in the intermediate portion of the basket  60  is spaced about 0.05 inches to 0.394 inches apart from the nearest legs, preferably 0.0787 inches apart. In another embodiment, the parallel spiral-shaped legs are distanced about 0.118 inches to 0.236 inches apart, preferably 0.118 inches. 
   In one embodiment, the basket  60  is embedded in the wall of the sheath  12  as shown in  FIGS. 11A and 11B . The cannula  14  is operably attached to the second basket portion  13 . For example, the cannula may be attached to the tip  22  of the basket  60 . 
   As shown in  FIG. 11A , when the tip  22  of the basket  60  is axially-moved by withdrawing cannula  14  in the direction of the arrow, the second basket portion  13  is drawn closer to the sheath thereby exerting a compressive force on the basket  60  moving the basket between a retracted position to an expanded position shown in  FIG. 11B . When the basket is compressed against the end  34  of sheath  12 , the intermediate section  15  is displaced radially outward relative to the first  11  and second  13  portions when the basket  60  is in the expanded position ( FIG. 11B ). The further the tip  22  is brought toward the sheath  12 , the greater is the radial outward displacement of the intermediate portion  15  of basket  60 . 
   The spiral legs of basket  60  can be formed to assume a substantially predetermined configuration upon being expanded. That is, the spiral legs can be pre-formed such that when the compressive force is exerted on the basket  60  between the sheath  12  and the tip  22 , the resultant expansion of basket  60  yields a predetermined configuration. The preferred configuration of the basket  60  is shown in  FIG. 10B . Further, the spiral legs  17  can be formed of heat-settable or other suitable polymer materials, and those materials can be heat-set or thermoset so that the spiral legs  17  obtain the predetermined configuration upon expansion. Each of the spiral legs  17  of the basket  60  alternatively and preferably can be made of wire of rectangular cross-section, round wire, or other material (e.g., plastic) with these or other cross-sectional shapes. 
     FIGS. 12A-12E  illustrate an application of the basket  60  of  FIGS. 11A and 11B  in a clinical situation.  FIG. 12A  shows a stone  28 , such as a kidney or gall stone, located in a tract  26 . An operator (e.g., a physician), preferably under endoscopic guidance, advances the sheath  12  with basket  60  in its retracted position into the tract  26  until the basket  60  is advanced preferably beyond the stone  28 . Once the basket  60  is positioned beyond the stone  28 , as shown in  FIG. 12B , the tip  22  of the basket  60  is withdrawn by moving the cannula  14  in the direction of the arrow shown in  FIG. 12B . The spiral legs  17  of the intermediate portion  15  of basket  60  expand radially as the intermediate basket portion is compressed between the sheath  12  and second basket portion  13  and the basket is moved between a retracted position and an expanded position. The cannula  14  is withdrawn until the diameter of the radially expanded intermediate portion  15  reaches a desired dimension. The radially-expanded spiral legs  17  of the basket  60  serve as an obstruction to advancement of the stone  28 . The stone  28  can now be fragmented by intervention therapy such as by lithotripsy. The basket  60  in its expanded position is then maneuvered around the stone or stone fragments  28  as illustrated in  FIG. 12C . The stone or stone fragments  28  enter the basket  60  between the flexible and freely moveable spiral legs  17  as shown in  FIG. 12D . The basket  60  is substantially returned to its retracted position by moving the elongate member  14  in the direction of the arrow in  FIG. 12E . The stone or stone fragments  28  are entrapped in the basket  60  as shown in  FIG. 12E . The operator then removes the sheath  12  and the basket  60  with entrapped stone or stone fragments  28  from the tract  26 . 
   Still referring to  FIGS. 12A-12E , the stone  28 , prior to being fragmented, is typically greater than about 10 mm in diameter. Once fragmented, the pieces of the stone  28  can be about 2 mm to 10 mm in diameter, and these pieces can then enter the basket  60  between the legs  17  because the distance between the legs is about 2 mm or less and because the legs are flexible. It is an important aspect of the invention that the basket  60  acts as both a stone immobilization device and a stone retrieval device. 
   In the preferred embodiment shown in  FIG. 13A , the expandable device  10  comprises the sheath  12 , and the basket  60  is moveable within the sheath  12 . In general, the basket moves relative to the sheath  12  between an expanded and retracted positions. When the basket  60  is enclosed in the sheath  12 , the basket  60  is in its retracted position, and it&#39;s in its expanded position when it extend from the distal end of the sheath  12  ( FIG. 13B ). The first basket portion  11  is attached to the cannula  14  (e.g., a solid wire or a plurality of wires) that is longitudinally disposed in the lumen of sheath  12 . When the sheath  12  is moved relative to the basket  60  in the direction of the arrow ( FIG. 13B ), the spiral legs  17  exit from the end of the sheath and the basket  60  expands radially, thereby moving the basket  60  from its retracted position to its expanded position. 
   The spiral legs  17  of basket  60  in  FIGS. 13A and 13B  can be formed to assume a substantially predetermined configuration upon being expanded. For example, the spiral legs  17  can be pre-formed such that when the spiral legs  17  are released from the end of the sheath  32 , the resultant expansion of basket  60  yields the configuration shown in  FIG. 10B . The spiral legs  17  can be formed of the materials mentioned previously. 
   The retrieval device  10  illustrated in  FIGS. 13A and 13B  may be used to retrieve a stone  28 , such as a kidney or gall stone, from a tract  26 .  FIGS. 14A-14E  illustrate an application of the basket  60  of  FIGS. 13A and 13B  in a clinical situation. As shown in  FIG. 14A , the sheath  12  with the basket  60  enclosed there within is advanced in the tract  26  until the basket  60  is advanced beyond the stone  28 . When the sheath  32  is retracted in the direction of the arrow as shown in  FIG. 14B , or alternatively when the cannula  14  is moved in a direction opposite to the arrow shown in  FIG. 14B , the spiral legs  17  are released from the end of sheath  12  causing the basket  60  to move between a retracted position to an expanded position. In accordance with the invention, the basket  60 , with its multiple, spiral-shaped, generally parallel, non-overlapping, flexible, and non-intersecting legs  17 , can now be used as an immobilization device and a retrieval device. Typically, and in accordance with the invention, it will first be used as a stone immobilization device or blocking device so the stone  28  can be fragmented, and then it is used to retrieve the stone or stone fragments  28  which will tend to enter the basket  60  because of the unique shape of the legs  17 . The basket  60  in the expanded position can be maneuvered around the stone fragments  28  as shown in  FIG. 14C . The stone or stone fragments  28  enter the basket  60  between the flexible, freely moveable spiral legs  17  as illustrated in  FIG. 14D . The sheath  12  is then moved relative to the spiral legs  17  as shown in  FIG. 14E  until the spiral legs  17  are snug about the stone/stone fragments  28 . The operator then removes the basket  60  with the entrapped stone/stone fragments  28  and the sheath  12  from the tract  26 . 
   In another aspect of the invention, the basket  60  shown in  FIGS. 11A ,  11 B,  13 A and  13 B with multiple, spiral-shaped, generally parallel, non-overlapping, flexible and non-intersecting legs  17  can be used to retrieve intact stones having a diameter of about 0.05 inches-0.394 inches. The basket  60  in the expanded position can be maneuvered around the stone  28  as illustrated in  FIG. 14C . The stone  28  enters between the flexible, spiral-shaped legs of the basket as illustrated in  FIG. 14D . The sheath  12  is moved relative to the spiral legs  17  as shown in  FIG. 14E  until the spiral legs  17  are snug about the stone  28 . The basket  60  is withdrawn from the body. 
   Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.