WO2008063883A1

WO2008063883A1 - Umbrella stone extractor

Info

Publication number: WO2008063883A1
Application number: PCT/US2007/083871
Authority: WO
Inventors: Thomas Gregory Self; David F. Waller
Original assignee: Wilson-Cook Medical Inc.
Priority date: 2006-11-21
Filing date: 2007-11-07
Publication date: 2008-05-29

Abstract

A system and method for a medical extractor device is provided including a fabric-bordered stone-engaging structure for extracting an object such as a stone. The device may be configured to require active opening force for opening the stone-engaging structure, or may be configured such that the stone-engaging structure is biased open.

Description

UMBRELLA STONE EXTRACTOR

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Application Ser. No. 60/860,287, filed Nov. 21 , 2006, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention relates generally to medical devices, and relates more specifically to devices and methods for minimally invasive surgical extraction of stones (calculi) such as bile stones.

BACKGROUND

[0003] The gall bladder is an organ that stores bile secreted by the liver. The cystic duct from the gall bladder merges with the common hepatic duct, forming the common bile duct A number of medical conditions are associated with various disorders, diseases, and injuries associated with the bile duct.

[0004] Choledocholithiasis is a medical condition associated with the entry of a biliary calculus (bile stone) into the bile duct. Obstruction of the bile duct can be excruciatingly painful for a patient suffering therefrom, and can cause nausea, fever, vomiting, and jaundice. Complete, persistent obstruction of the common bile duct can cause cholangitis, a life threatening infection of the biliary tree, which is a medical emergency. An obstruction of the common bile duct can also lead to an obstruction of the pancreatic duct, which may cause pancreatitis. [0005] Several methods of treatment are used to remove the gall bladder and stones, including open surgery or laparoscopic surgery. Less invasive treatments may be used as well. For example, the stones may be removed endoscoptcally, without having to create any external incisions. In this technique, an endoscope is directed through the patient's esophagus to a location adjacent the Sphincter of Oddi, where the bile duct opens into the duodenum. Typically, a sphincterotome is used to cannulate and widen the sphincter opening to ease access into the bile duct for stone retrieval. A number of existing devices utilize a basket deployable from a lumen of a catheter that is directed into the bile duct to capture stones for removal.

[0006] One such device is a basket device 100 comprising a wire basket 104 mounted on the distal end of an elongate basket wire 102, which is guided through a catheter 110 to a location such that the basket 104 can be directed around a stone 106 (See FIGS, 1A-1C). Once the basket 104 is around the stone 106, the basket 104 is retracted toward the catheter 110 to draw the stone out. However, the stone 106 may be lost between the wires that form the basket 104, particularly if - during manipulation - the stone breaks into smaller pieces (See FIG. 1 D) so that it can be removed or allowed to pass. If the basket 104 is part of a lithotripsy device, it may be the user's intent to break the stone 106 into smaller pieces. However, multiple passes with a basket must then be made to capture and extract any stone fragments that are too large to pass safely and/or naturally out of the passage, or that are otherwise desired to be retrieved (e.g., for analysis).

[0007] Thus it would be advantageous to provide a stone-retrieval device that includes structure less likely to lose a stone, and - particularly if functioning as a mechanical lithotriptor - that is less likely to lose large pieces of a fragmented stone.

[0008] Another such device is a stone extraction balloon device 150, which is shown in FIGS. 2A-2C. The balloon device 150 includes an endoscopically-introduced catheter 152 with a distally mounted balloon such as a latex balloon 154. As shown in FIG. 2A, in a "capture and drag" stone-removal procedure for removing a biliary calculus, the balloon-end of the catheter 152 is directed along a wire guide 156 into a passage (shown here as the common bile duct) 160 and past a stone 164 (or stones) to be rθmoved. This typically is preceded by cannulation of the sphincter of Oddi {where the common bile duct 160 meets the duodenum 162), to provide easier access into the bile duct. As depicted in FIG. 2B₁ the balloon 154 is then inflated. Then, in the manner illustrated in FIG. 2C, the device 150 is drawn proximally, pulfing the stone 164 into the duodenum 162, where it can then be captured or allowed to pass through elimination. It would be advantageous to provide a non-balloon device for effecting a "capture and drag" stone-removal procedure.

BRIEF SUMMARY

[0009] . In one aspect, the present invention includes a medical extraction device having a proximal handle, an elongate sheath extending distally from the handle, and a stone-engaging structure distally attached to a distal portion of one of the drive cable or the elongate sheath. The sheath includes a lumen extending therethrough, and a drive cable extending from the proximal handle through the lumen. The stone- engaging structure includes a plurality of longitudinal ribs having a flexible material disposed therebetween and forming a canopy. The handle includes a first handle member and a second handle member that is axiaily movable relative to the first handle member. The first handle member is connected to the elongate sheath and the second handle member is connected to the drive cable. The handle has a first mode of operation comprising a direct axial sliding movement of the first handle member relative to the second handle member that results in corresponding relative movement of the elongate sheath and drive cable. [0010] In another aspect, the present invention includes a stone extraction device embodiment that has a proximal handle, an elongate sheath extending distally from the handle, and a stone-engaging structure distally attached to a drive cable, which extends through a lumen running through the elongate sheath. The stone-engaging structure includes a plurality of longitudinal ribs having a flexible material disposed therebθtween and forming a canopy. The handle includes a first handle member and a second handle member that is axially movable relative to the first handle member. The first handle member is connected to the elongate sheath, and the second handle member is connected to the drive cable; the handle has a first mode of operation comprising a direct axial sliding movement of the first handle member along the second handle member that results in corresponding relative movement of the elongate sheath and drive cable.

[0011] In yet another aspect, the present invention includes a stone extraction device having a proximal handle, an elongate sheath extending distally from the handle - with a lumen extending therethrough, a drive cable extending through the lumen of the elongate sheath, and a stone- engaging structure distally attached to the elongate sheath. The stone- engaging structure includes a plurality of longitudinal ribs having a flexible material disposed therebetween and forming a canopy, and the ribs preferably are formed such that the stone-engaging structure is biased in a closed configuration. The drive cable includes a distally-disposed opener member that is configured to contact an inner surface of the stone- engaging structure in a manner that, upon an actuation of the drive cable, spreads the ribs apart to open the stone-engaging structure. The handle includes a first handle member and a second handle member that is movable relative to the first handle member. The first handle member is connected to the elongate sheath, and the second handle member connected to the drive cable such that the handle has a first mode of operation wherein a direct axial sliding movement of the first handle member along the second handle member results in corresponding relative movement of the elongate sheath and drive cable. [0012] In still another aspect, the present invention includes a method for extracting an object, Steps of the method include: (a) providing an extractor device comprising: a proximal handle; an elongate sheath extending distally from the handle, with a lumen extending therethrough; a drive cable extending from the proximal handle through the lumen; and a stone-engaging structure distally attached to a distal portion of one of the drive cable or the elongate sheath, wherein the stone-engaging structure comprises a plurality of longitudinal ribs having a flexible material disposed therebetween and forming a canopy; and wherein the handle comprises a first handle member and a second handle member axially movable relative to the first handle member, the first handle member connected to the elongate sheath, the second handle member connected to the drive cable; and wherein the handle has a first mode of operation comprising a direct axial sliding movement of the first handle member relative to the second handle member that results in corresponding relative movement of the elongate sheath and drive cable such that sliding movement in a first direction generally opens the stone-engaging structure and sliding movement in a second direction generally closes the stone-engaging structure; (b) providing a passage containing an object to be extracted; (c) directing a distal stone-engaging structure end of the extractor device to a location in the passage adjacent to and distal of the object to be extracted; (d) moving the first handle member relative to second handle member such that drive cable moves relative to the elongate sheath in a manner causing the stone-engaging structure to open to an outer diameter that is greater than a difference between an outer diameter of the object to be extracted and an inner diameter of the passage; and (e) and engaging the stone-engaging structure with the object to be extracted.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIGS. 1 A-1 D depict the function of a lithotriptor basket;

[0014] FIGS. 2A-2C show the function of a balloon stone extraction device;

[0015] FIGS. 3A-3B illustrate a first extraction device embodiment, shown with its basket in a closed configuration; [0016] FIGS. 3C-3D illustrate the device of FIGS. 3A-3B, shown with its basket in an open configuration, and being used in a sweep extraction method;

[0017] FIGS. 3E-3F show the device of FIGS. 3A-3B with its basket in an open configuration for use in a capture extraction method;

[0018] FIG. 3G shows the device of FIGS. 3A-3B and 3E-3F with its basket closed around a stone as used in a capture extraction method;

[0019] FIG. 4A depicts a second extraction device embodiment, shown with its basket retracted in a closed configuration;

[0020] FIG. 4B. illustrates the device of FIG. 3A, shown with its basket in an open configuration in a capture extraction method;

[0021] FIG. 4C shows the device of FIGS. 4A-4B with its basket closed around a stone; and

[0022] FIG. 4D depicts the device of FIGS. 4A-4B, shown with its basket in an open configuration, and being used in a sweep extraction method.

DETAILED DESCRIPTION

[0023] A first embodiment of a stone extractor 200 is illustrated in FIGS. 3A-3E. The stone extractor 200 includes a drive cable 204, circumscribed by and axially sϋdable within an outer sheath 206. The distal end of the extractor 200 includes a stone-engaging structure embodied as an umbrella basket 208, which is shown in FIG. 3A in a closed orientation, adjacent a biliary stone 211. The stone extractor 200 has a handle 202, which includes a three-ring handle design. The stem (thumb-ring) portion 210 is attached to the proximal end of the outer sheath 206.

[0024] The spool (finger-ring) portion 212 is attached to the proximal end 205 of the drive cable 204 such that axial movement of the stem 210 relative to the spool 212 causes corresponding axial movement of the drive cable 204 within the outer sheath 206. (Note: the finger ring portion is referred in to as a "spool" in the art as its longitudinal cross-section is shaped like the longitudinal section of a thread spool - albeit with optional finger rings extending from and connecting the top and bottom ends). A preferred drive cable will be sufficiently flexible to allow manipulation of the extractor through an endoscope and/or in other appropriate environments, while maintaining a longitudinal rigidity sufficient to allow longitudinal proximal/distal manipulation of a distal attachment (e.g., basket). In preferred embodiments, the handle will be constructed of materials known in the art to be durable and suited for multiple sterilizations such as metals, resins, composites, or combinations thereof. For a disposable handle, certain injection-molded polymers may be appropriate. [0025] The basket 208 is attached to the distal end of the outer sheath 206, preferably by a stainless steel band or other suitable fastening means (not shown). The basket 208 includes a frame 230 formed by a plurality of flexible ribs (230a, 23Ob₁ etc.), which preferably are made of nitinol, stainless steel, or another suitably durable and manipulable material. Attached to the frame 230 in umbrella-like fashion is a canopy 232, which preferably is formed from a non-latex fabric or mesh. This is shown more clearly in FIG. 3C, which illustrates the extractor 200 in an open orientation, adjacent the biliary stone 211. The ribs of the frame 230 are biased (have a default orientation) into the closed position shown in FIGS. 3A-3B. When the basket 208 is in the closed orientation, a proximal portion of each of the ribs 230a, 230b angles slightly outward at an acute angle relative to the central longitudinal axis of the outer sheath 206. A distal end portion of each rib 230a, 230b curves inward toward the central longitudinal axis of the outer sheath 206. The distal ends of the ribs 230 may include one or more elastomeric members 238 disposed between two or more of the ribs, which may aid closing the basket 208 in a capture operation such as is shown in FIGS. 3E-3G. [0026] FIG. 3B shows a detail central longitudinal section view of the closed basket 208 of the distal portion of FIG. 3A, and FIG. 3D shows a central longitudinal section view of the open basket 208 of the distal portion of FlG. 3C. The distal end of the drive cable 204 includes a generally conical opener body 209. When the basket 208 is in the closed orientation shown in FIGS. 3A-3B, the opener body 209 is distally disposed within a central or distal portion of the basket 208. During an actuation of the extractor 200, the handle 202 is actuated to draw the drive cable 204 proximally by drawing the spool 211 proximally relative to the stem 210. During this actuation, the angled proximal surface of the conical opener body 209 contacts and progressively spreads apart the ribs 230a, 230b, opening the canopy 232 of the basket 208 as shown in FIG. 3D. In a preferred embodiment, two or more of the ribs are provided with radio- opaque markers (not shown) near the distal end of each for use in orienting the basket 208. These markers may provide for added precision in orienting the basket 208 beyond an ability to fluoroscopically and/or endoscopically visualize the ribs and/or canopy.

[0027] The stone extractor may be used in a "sweep extraction method," or in a "capture and extract" method. The sweep extraction method is illustrated with reference to FIGS. 3C-3D. As depicted in FIGS. 3C-3D, the basket 208 may be advanced distally past the stone 211. Then, after it is opened by an actuation of the drive cable 204, the basket 208 can be drawn proximally to sweep the stone 211 down the bile duct and out into the duodenum. When intended for use with the sweep method, it is preferable that the ribs and basket are sized such that the maximum outer diameter of the expanded basket canopy is near to, equal to, or greater than a maximum inner diameter of the passage (e.g., bile duct) wherefrom a stone is to be removed so that - when open - the basket is unlikely to be drawn past a stone without sweeping it along. [0028] The capture and extract method is shown with reference to FIG. 3E-3G. As shown in FIGS. 3E-3F, once opened by an actuation of the drive cable 204 as described above, the basket 208 can be advanced to encompass a stone 211 (or a plurality of stones). Then, as illustrated in FIG. 3G, once the stone 211 is within the interior space of the basket 208, thθ handle 202 may be actuated to release the "opening pressure" of the opener body 209 on the ribs 230a, 230b such that - by dint of the ribs' bias - they close the canopy 232 around the stone 211. The stone 211 may then be extracted by withdrawing the extractor 200 from the bile duct, and released in the duodenum for elimination. When the extractor is to be used in a capture and extract method, it would be advantageous to provide optional, proximally-directed hook structures 208a at the distal rib ends to help retain a stone in the basket during extraction (see FIG. 3F₁ which is a central longitudinal section view of FIG. 3E). Either or both of the above methods may be repeated as needed to extract multiple stones. [0029] A second embodiment of a stone extractor 300 is illustrated in FIGS. 4A-4C. In addition to the handle 302, the stone extractor 300 includes a drive cable 304 that is circumscribed by and is axially slidable within an outer sheath 306. The distal end of the extractor 300 includes a stone-engaging structure embodied as an umbrella basket 308, which is shown in FIG. 4A withdrawn into the distal end of the outer sheath 306 in a closed orientation, and adjacent a biliary stone 311. The stone extractor 300 has a handle 302, which includes a three-ring handle design. The stem (thumb-ring) portion 310 is attached to the proximal end 305 of the outer sheath 306. The spool (finger-ring) portion 312 is attached to the drive cable 304 such that an axial movement of the spool 312 relative to the stem 310 causes a corresponding axial movement of the drive cable 304 within the outer sheath 306. In preferred embodiments, the handle will be constructed of materials known in the art to be durable and suited for multiple sterilizations such as metals, resins, composites, or combinations thereof. For a disposable handle, certain injection-molded polymers may be appropriate.

[0030] The basket 308 is attached to the distal end of the drive cable 304 (e.g. by a crimp, weld, retaining ring, or other suitable connecting means). The basket 308 includes a frame 330 formed by a plurality of flexible ribs (330a, 330b, etc.), which preferably are made of nitinol, stainless steel, or another suitably durable and manipulate material. Attached to the frame 330 in inverse umbrella-like fashion is a canopy 332, which preferably is formed from a non-latex fabric or mesh {e.g., nylon, PET, PTFE; latex may be used as well). This is shown more clearly in FIG. 4B, which illustrates the extractor 300 in an open orientation, partially encompassing the biliary stone 311. The ribs of the frame 330 are biased/pre-loaded such that their default orientation is into the open position shown in FlG. 4B. The basket 308 may be placed in a closed orientation by being drawn into the outer sheath 306. When the basket 308 is in the closed orientation, each of the ribs 330a, 330b is generally parallel with, or curves outward relative to, the central longitudinal axis of the outer sheath 306. A distal end portion of each rib 330a, 330b curves inwardly toward the central longitudinal axis of the outer sheath 306.

[0031] When the basket 308 is in the closed orientation shown in FIG. 4A, the opener body 309 is distally disposed within the basket 308. During an actuation of the extractor 300, the handle 302 is actuated to draw the outer sheath 306 proximally and/or extend the drive cable 304 distally. During this actuation, the outward bias/pre-load of the ribs 330a, 330b causes them to spread radially, opening the canopy 332 of the basket 308 as shown in FIG. 4B. In an alternative embodiment, the fabric between the ribs and forming the canopy may include a "shape memory fabric" (e.g., a nitinol wire weave) or similar construct known in the art such that the outward bias/pre-load of the basket originates from the fabric rather than, or in addition to, the ribs.

[0032] Likewise, this stone extractor embodiment 300 may be used in a "sweep extraction method," or in a "capture and extract" method. In a capture and extract method as shown in FIGS. 4B-4C, the basket 308- once opened - can be advanced to generally embrace the stone 311. A user may actively manipulate the outer diameter of the basket 308 by actuating the handle to advance or retract the outer sheath 306 around the ribs. Once the stone 311 is within the interior space of the basket 308, the handle 302 may be actuated to advance the outer sheath 306 distally, exerting an inward radial force on the ribs 33Oa₁ 330b such that they close the canopy 332 around the stone 311. The stone 311 may then be extracted by withdrawing the extractor 300. In one embodiment, the ribs 330a, 330b and outer sheath 306 may be provided with sufficient structural strength and the handle 302 may provide sufficient mechanical advantage that a retraction of the ribs into the outer sheath will reduce the internal volume of the canopy and provide force via the ribs on the stone 311 sufficient to break it into smaller pieces (in the fashion of a [ithotriptor), thereby reducing the overall outer diameter of the stone and canopy. In this operation, the canopy preferably will capture/retain the stone fragments both laterally (by the fabric of the canopy) and longitudinally (by the curvature of the ribs leaving, at the most, a small distal opening of the canopy when the proximal rib ends are drawn into the outer sheath). Additionally, when the extractor is to be used in a capture and extract method, it would be advantageous to provide optional, proximally-directed hook structures 308a at the distal rib ends to help retain a stone in the basket, particularly if the basket is to implement a lithotriptor-type functionality where it is intended that the stone's structure be at least partially disrupted.

[0033] In conjunction with, or independently of, using "capture and extract" method, the extractor 300 may be used in a "sweep extraction method," as shown in FIG. 4D. During a sweep extraction operation, the closed distal end of the extractor 300 (see FIG. 4A) is directed into a passage 313 containing a stone and distaily past the stone(s) 311 to be extracted (in all embodiments herein, the stone(s) are to be removed from a passage such as a common bile duct, but - for clarity of illustration - the passage is illustrated only in FiG. 4D). Then, as also shown in FIG. 4D, the basket 308 is opened in the same manner described above, and can then be drawn proximally to sweep/drag the stone(s) 311 along in the desired direction. The abovementioned curvature of the ribs preferably provides a generally atraumatic maximum outer diameter of the open basket. Those of skill in the art will appreciate that the outer diameter open basket 308 preferably is greater than the difference between the outer diameter of the stone 311 and the inner diameter of the passage 313 wherefrom the stone 311 is being extracted, thereby lessening the likelihood that the open basket 308 might bypass the stone 311 while trying to sweep it along.

[0034] Those of skill in the art will appreciate that variants of the above- described device embodiments and methods may be practiced within the scope of the present invention. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting. It should be understood that the following claims, including all equivalents, are intended to define the spirit and scope of this invention.

Claims

[0035] CLAIMS WE CLAIM:

1. A medical extraction device comprising: a proximai handle; an elongate sheath extending distaliy from the handle, with a lumen extending therethrough; a drive cable extending from the proximal handle through the lumen; and a stone-engaging structure distaliy attached to a distal portion of one of the drive cable or the elongate sheath; wherein the stone-engaging structure comprises a plurality of longitudinal ribs having a flexible material disposed therebetween and forming a canopy; and wherein the handle comprises a first handle member and a second handle member axially movable relative to the first handle member, the first handle member connected to the elongate sheath, the second handle member connected to the drive cable; and wherein the handle has a first mode of operation comprising a direct axial sliding movement of the first handle member relative to the second handle member that results in corresponding relative movement of the elongate sheath and drive cable.

2. The medical extraction device of claim 1 , wherein a movement of the elongate sheath relative to the drive cable causes the stone-engaging structure to move between an open configuration and a closed configuration.

3. The medical extraction device of claim 1 , wherein one end of the stone-engaging structure is attached to the elongate sheath.

4. The medical extraction device of claim 3, wherein a proximal portion of the ribs of the stone-engaging structure is attached to the elongate sheath and the ribs of the stone-engaging structure are biased into a closed configuration such that the ribs are generally parallel to each other.

5. The medical extraction device of claim 4, further comprising an opener element disposed on a distal portion of the drive cable; the opener element being configured to, upon a first actuation, exert a spreading force upon the ribs of the stone-engaging structure such that a distal portion of the ribs are spread apart from each other, thereby opening the stone-engaging structure and spreading the canopy to form an inner stone-engaging structure canopy cavity.

6. The medical extraction device of claim 5, wherein a second actuation of the opener element releases the spreading force upon the stone-engaging structure ribs such that the bias of the ribs at least partially closes the stone-engaging structure.

7. The medical extraction device of claim 1 , wherein the stone- engaging structure is distally attached to a distal portion of the drive cable and each of the plurality of ribs is biased to spread apart from others of the plurality of ribs.

8. The medical extraction device of claim 1 , wherein each of the plurality of ribs is curved such that an outer diameter of the distal and proximal stone-engaging structure ends formed thereby is smaller than an outer diameter of a stone-engaging structure portion between said distal and proximal stone-engaging structure ends.

9. The stone extraction device of claim 1 , further comprising an elastomeric member disposed between at least two of the ribs.

10. A stone extraction device comprising: a proximai handle; an elongate sheath extending distally from the handle, with a lumen extending therethrough; and a stone-engaging structure distally attached to a drive cable, the drive cabie extending through the lumen of the elongate sheath; wherein the stone-engaging structure comprises a plurality of longitudinal ribs having a flexible material disposed therebetween and forming a canopy; the handle comprising a first handle member and a second handle member axially movable relative to the first handle member, the first handle member connected to the elongate sheath, the second handle member connected to the drive cable; wherein the handle has a first mode of operation comprising a direct axial sliding movement of the first handle member along the second handle member that results in corresponding relative movement of the elongate sheath and drive cable.

11. The stone extraction device of claim 10, wherein the stone-engaging structure occupies a closed configuration when retracted into a portion of the elongate sheath.

12. The stone extraction device of claim 10, wherein one of the ribs or the flexible material is pre-loaded/biased so as to spread the ribs apart such that the stone-engaging structure occupies an open configuration when extended distally from the elongate sheath.

13. The stone extraction device of claim 10, wherein the drive cable, ribs, and the elongate sheath are constructed with sufficient strength that a stone captured in the stone-engaging structure may be at least partially crushed by drawing the stone-engaging structure at least partially into the sheath to reduce its internal volume.

14. The stone extraction device of claim 10, wherein each of the plurality of ribs is curved such that each of an outer diameter of the distal and proximal stone-engaging structure ends formed thereby is smaller than an outer diameter of a stone-engaging structure portion between said distal and proximal stone-engaging structure ends.

15. The stone extraction device of claim 10, further comprising an elastomeric member disposed between at least two of the ribs.

16. A stone extraction device comprising: a proximal handle; an elongate sheath extending distally from the handle, with a lumen extending therethrough; a drive cable extending through the lumen of the elongate sheath; and a stone-engaging structure distally attached to the elongate sheath; wherein the stone-engaging structure comprises a plurality of longitudinal ribs having a flexible material disposed therebetween and forming a canopy, said ribs being biased such that the stone-engaging structure is biased in a closed configuration; the drive cable comprising a distaily-disposed opener member that is configured to contact an inner surface of the stone-engaging structure in a manner that, upon an actuation of the drive cable, spreads the ribs apart to open the stone-engaging structure; the handle comprising a first handle member and a second handle member axially movable relative to the first handle member, the first handle member connected to the elongate sheath, the second handle member connected to the drive cable; wherein the handle has a first mode of operation comprising a direct axial sliding movement of the first handle member along the second handle member that results in corresponding relative movement of the elongate sheath and drive cable.

17. The stone extraction device of claim 16, wherein the opener member is generally conical in shape and is configured such that an apex portion of the cone is attached to the drive cable and a base portion of the cone contacts the ribs.

18. The stone extraction device of claim 17, wherein a proximal movement of the drive cable draws the opener member against the ribs in a manner that spreads them apart to open the stone-engaging structure.

19. The medical extraction device of claim 16, wherein each of the plurality of ribs is curved such that an outer diameter of the distal and proximal stone-engaging structure ends formed thereby is smaller than an outer diameter of a stone-engaging structure portion between said distal and proximal stone-engaging structure ends.

20. The stone extraction device of claim 16, further comprising an elastomeric member disposed between at least two of the ribs.