United States Patent
`
`[19]
`
`Kleshinski
`
`5,776,162
`[11] Patent Number:
`
`[45] Date of Patent:
`Jul. 7, 1998
`
`USOOS7761 62A
`
`[54] VESSEL IMPLANTABLE SHAPE MEMORY
`APPLIANCE WITH SUPERELASTIC
`HINGED JOINT
`
`[75]
`
`Inventor: Stephen J. Kleshinski. Scituate. Mass.
`
`5.702.419
`
`............................. 606/198
`12/1997 Berry et a1.
`.
`.
`.
`.
`Primary Exammer—Michael Powell Burz
`Assistant Examiner—David O. Reip
`Attorney, A3671}. 07‘ Firm—Sixbey. Friedman. Leedom &
`Ferguson; Daniel W. Slxbey
`
`[73] Assignee: Nitinol Medical Technologies, Inc,
`Boston. Mass.
`
`[57]
`
`ABSTRACT
`
`[21] Appl. No.: 778,634
`'
`Jan. 3, 1997
`[22] Fllcdi
`[51]
`Int. Cl.6 .................................................... A61M 29/00
`[52] US. Cl. .............................. 606/198; 606/191; 623/1;
`623/12
`.
`[58] Field or Search """""""6'06/198200 662%1191i219151
`‘
`‘
`‘
`‘
`‘
`.
`References Cited
`US. PATENT DOCUMENTS
`
`[56]
`
`4’425’908
`5,395,390
`5545210
`5,601,593
`
`”1984 Slmon '
`3/1995 Simon et a1,
`
`.
`8/1996 Hess et a].
`2/1997 Freitag .................................... 606/198
`
`.
`
`A medical appliance of shape memory material is provided
`for implantation in a vascular passageway for engagement
`with the walls of the passageway. The appliance includes a
`body formed of thermal shape memory material having a
`temperature “Mfomfion level below WhiCh the body is in
`a mensmc State and is PM?” and compressma and
`above which the body is in an austenitic state and is
`self-expandable to a substantially rigid pre—cornpressed con-
`figuration. The shape memory material in the austenitic state
`is capable of being transformed by stress to the martensitic
`state. The body includes segments which expand outwardly
`away from the longitudinal axis of the body in the austenitic
`state thereof. and a superelastic hinged joint is formed in at
`least one of the segments by reducing the cross-sectional
`area of the segment in a localized area.
`
`16 Claims, 2 Drawing Sheets
`
`
`
`Edwards Lifesciences v. Boston Scientific
`
`IPR2017-00444 EX. 2030
`
`US. Patent N0. 6,915,560
`
`Page 1 of 7
`
`Page 1 of 7
`
`

`

`US. Patent
`
`Jul. 7, 1998
`
`Sheet 1 of 2
`
`5,776,162
`
`FIG!
`
`
`
`
`
`
`
`Page 2 of 7
`
`Page 2 of 7
`
`

`

`US. Patent
`
`Jul. 7, 1998
`
`Sheet 2 of 2
`
`5,776,162
`
`12
`
`.
`
`.
`
`.
`
`.
`
`3 Standard Wire Sample
`
`"“33?ng Wire
`—o—Hinged Wire
`Sample
`
`/’ “
`
`\—/i’_—\V/‘
`
`¥:D
`
`0
`\4"
`
`10
`
`6
`
`4 2
`
`A 8
`
`E 3 §
`
`O L
`
`“
`
`Page 3 of 7
`
`Page 3 of 7
`
`

`

`5.776.162
`
`1
`VESSEL IMPLANTABLE SHAPE MEMORY
`APPLIANCE WITH SUPERELASTIC
`HINGED JOINT
`
`BACKGROUND OF THE INVENTION
`
`In recent years. a number of medical devices have been
`designed which are adapted for compression into a small
`size to facilitate introduction into a vascular passageway and
`which are subsequently expandable into contact with the
`walls of the passageway. These devices. among others.
`include stents for holding open a vascular passageway and
`blood clot filters which expand and are held in position by
`engagement with the inner wall of a vein. It has been found
`to be advantageous to form such devices of a shape memory
`material having a first. relatively pliable low temperature
`condition and a second. relatively rigid high-temperature
`condition. By forming such devices of temperature respon—
`sive material. the device in a flexible and reduced stress state
`
`may be compressed and fit within the bore of a delivery
`catheter when exposed to a temperature below a predeter-
`mined transition temperature. but at temperatures at or above
`the transition temperature. the device expands and becomes
`relatively rigid.
`Known self expanding medical devices have been formed
`of Nitinol. an alloy of titanium and nickel which provides
`the device with a thermal memory. The unique characteristic
`of this alloy is its thermally triggered shape memory. which
`allows a device constructed of the alloy to be cooled below
`a temperature level and thereby softened for loading into a
`catheter in a relatively compressed and elongated state. and
`to regain the memoried shape in an austenitic state when
`warmed to a selected temperature. above the temperature
`transformation level. such as human body temperature. The
`two interchangeable shapes are possible because of the two
`distinct microcrystalline structures that are interchangeable
`with a small variation in temperature. The temperature at
`which the device assumes its first configuration may be
`varied within wide limits by changing the composition of the
`alloy. Thus. while for human use the alloy may be focused
`on a transition temperature range close to 986° F.. the alloy
`readily may be modified for use in animals with different
`body temperatures.
`US. Pat. No. 4.425.908 to Simon discloses a blood clot
`
`filter formed of thermal shape memory material while US.
`Pat. Nos. 3.868.956 to Alfidi et al.. 4.503.569 to Dotter.
`4.512.338 to Balko et a1.. 5.354.308 and 5.395.390 to Simon
`et al. and European Application No. 0556.850A1 disclose
`stents of thermal shape memory material. Although these
`patented units operate effectively. it becomes necessary to
`provide devices in a large number of sizes to accommodate
`vessels of diflerent sizes or to vary the contact pressure
`between an expanded device and a vessel wall. With such
`prior units. when segments of different lengths expand into
`contact with a vessel wall. it has not been possible to achieve
`a substantially uniform contact pressure for all such seg-
`ments. Longer segments tend to contact the wall with a
`greater contact pressure than the shorter segments.
`
`SUMMARY OF THE INVENTION
`
`It is a primary object of the present invention to provide
`a vessel implantable appliance of shape memory material
`having temperature induced austenitic and martensite states
`with a hinged joint subject to stress induced martensite
`phase transformation.
`Another object of the present invention is to provide a
`novel and improved vessel implantable appliance of shape
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`2
`memory material wherein strain and flexion in the material
`are localized at a hinged joint. The shape memory material
`has a low temperature martensite state where the material is
`flexible and a high temperature austenitic state where the
`material returns to a predetermined state and becomes
`relatively rigid When the material is in the austenitic state.
`stress induced martensite can occur. and the hinged joint is
`designed so that stress induced martensite occurs at the joint.
`A further object of the present invention is to provide a
`novel and improved vessel implantable appliance of shape
`memory material wherein strain and flexion in the material
`are localized at a hinged joint. By having the joint subject to
`stress induced martensite phase transformation. and by
`locating the joint in sections of the appliance which expand
`into contact with a vessel wall during a temperature induced
`austenitic phase. the appliance section will exert a substan-
`tially constant force on the vessel wall over a large range of
`deflections. Also the potential for fatigue fractures of the
`material due to cyclic respiratory. cardiovascular or postural
`motions is reduced.
`
`A still further object of the present invention is to provide
`vena cava filters and stents of Nitinol which operate in a
`temperature induced austenitic state to exert a constant force
`on the walls of a vessel regardless of variations in vessel
`cross-sectional area or variations in the length of sections of
`the devices which contact the vessel walls.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a side view of a vena cava filter formed with
`superelastic hinged joints;
`FIG. 2 is an enlarged view of the superelastic hinged joint
`of FIG. 1;
`
`FIG. 3 is an enlarged View of the superelastic hinged joint
`of FIG. 2 in a flexed configuration;
`FIG. 4 is a chart showing the forces on a vessel wall
`exerted by standard appliances of Nitinol and the appliances
`of the present invention;
`FIG. 5 is a perspective view of a stent with the super-
`elastic hinged joints of the present invention: and
`FIG. 6 is a view of a cell of the stent of FIG. 5 with
`superelastic hinged joints.
`
`DETAILED DESCRIPTION
`
`By forming the body of a medical device of a Nitinol alloy
`material. such as Nitinol wire. transition between the mar-
`tensitic and austenitic states of the material can be achieved
`by temperature transitions above and below a transition
`temperature or u'ansition temperature range. Such controlled
`temperature transitions have conventionally been employed
`to soften and contract the Nitinol body for a medical unit to
`facilitate insertion into a catheter and to subsequently
`expand and rigidin the body within a vascular or other
`passageway. In addition to temperature sensitivity.
`it has
`been found that Nitinol. when in the temperature induced
`austenitic state. is also subject to stress sensitivity which can
`cause the material to undergo a phase transformation from
`the austenitic state to the martensitic state while the tem-
`perature of the material remains above the transition tem-
`perature level. When suificient stress is applied to a Nitinol
`strand in the austenitic state to initiate a phase transition to
`the martensitic state. the material reaches a superelastic
`plateau which extends over approximately a 2% to 71/2%
`stress range. When the material in the martensitic state
`reaches the superelastic plateau. additional applied stress
`within the plateau range is taken up by the phase transfor-
`
`Page 4 of 7
`
`Page 4 of 7
`
`

`

`5.776.162
`
`3
`
`mation. This superelastic plateau can be utilized in the
`design of a Nitinol medical unit which will apply a substan-
`tially equal pressure to the walls of a body passageway
`regardless of variations in the length of segments of the unit
`which contact such walls. Also. a Nitinol medical unit of a
`single size can be used in body passageways of difierent
`diameters or cross-sectional areas while still applying a
`substantially equal pressure to the walls of these variously
`sized passageways.
`Referring now to FIGS. 1. 2 and 3. a blood clot filter 10
`is illustrated which is made from a set of Nitinol wires. The
`wires are held together by two small sleeves or coils 12 and
`14 of the same material. each coil being spot welded to hold
`it in place and approximately one-quarter of an inch in
`length. Coil 12 is adjacent the tip 13 of the wires. and coil
`14 is approximately two inches from tip 13 when the wires
`are fully extended. In the low temperature martensite phase
`of the material. the set of wires can be straightened and held
`in a straight form that can pass through a length of fine
`plastic tubing with an internal diameter of approximately 2
`mm (#8 French catheter). In its high temperature austenitic
`form. the filter 10 recovers a preformed filtering shape.
`In its normal expanded configuration or preformed filter-
`ing shape. filter 10 is a double filter. having a first filter
`basket 16 and a second filter basket 18. The two filter baskets
`provide peripheral portions which engage the inner wall of
`the vein at two longitudinally spaced locations. The two
`filter baskets are generally symmetrical about a longitudinal
`axis passing through filter tip 13.
`The mesh of first filter basket 16 is formed from the
`sections of wires between the two quarter-inch coils 12 and
`14. The mesh is made up a series of seven overlapping loops
`20 arranged to form a rosette approximately 25 mm in
`diameter. The loops are angled slightly relative to the
`longitudinal axis of filter 10 and this angle can be varied to
`accommodate somewhat smaller diameters if the device is to
`be constrained in a tube of less than 25 mm in caliber. The
`
`loops 20 effectively divide the cross—sectional area to be
`filtered. The rosetxe formed by loops 20 can expand or be
`compressed to fit various sizes of vein. The peripheral
`portions or tips of the loops 20 press outwardly against the
`inner wall of the vein. although without becoming irnbedded
`in the vein; loops 20 thereby help to keep filter 10 in place.
`First filter basket 16 is convex relative to filter tip 13.
`The mesh of second filter basket 18 is formed by the six
`circumferentially spaced free wire ends or legs 22. which tilt
`and bow outwardly of the longitudinal axis of filter 10. The
`six free ends or legs 22 that extend beyond the second
`quarter inch coil 14 diverge so that their tips form a circle 24
`at
`their maximum divergence. Each leg is also bowed
`outwardly slightly. The legs serve to orient
`the device
`relative to the longitudinal axis of the vena cava. Second
`filter basket 18 is convex relative to filter tip 13.
`Each free end of a leg 22 is bent sharply outward at about
`a right angle to form a hook 26 of approximately 1.5 mm in
`length. The hooks are intended to engage the wall of the
`vena cava to prevent migration proximally or distally. The
`six legs 22 are of slightly different lengths to permit good
`packing within the delivery device. If legs 22 are all of a
`single length. the hooks may interfere with one another. so
`that the filter does not expand properly when delivered into
`the vein.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`The variable lengths of the legs 22 can result in each leg
`engaging the wall of the vena cava with a different contact
`pressure when the filter 10 is subjected to a temperature at
`or above the transition temperature. This is often
`
`65
`
`4
`undesirable. and to eliminate this variation in contact pres-
`sure a superelastic hinged joint 28 is provided in each of the
`legs 22. The hinged joint 28 is formed by reducing the
`cross-sectional area of the Nitinol wire forming a leg or
`other portion of the filter in a small
`localized area as
`illustrated in FIGS. 2 and 3 to localize stress deformation at
`the hinged joint. The cross-section of the hinged joint may
`be circular. rectangular. ovoid or some other desirable shape
`and the transition from the full wire cross-section to the
`reduced hinged joint cross section may be abrupt. tapered.
`rounded. or any combination of these. The force to be
`exerted by the legs 22 on the vessel wall is now determined
`primarily by the geometry of the hinged joint 28 and modern
`machining techniques allow this geometry to be precisely
`controlled.
`
`In the legs 22 of the filter 10. the hinged joints 28 should
`be of substantially the same cross-sectional geometry and
`located as shown between the coil 14 and the halfway point
`30 along the length of each leg. As will be noted in FIG. 1.
`the maximum inclination of each leg relative to the central
`longitudinal axis of the filter 10 occurs in this first half of the
`leg adjacent to the coil 14. and this area is subjected to
`greater stress as the leg expands and contacts the passage-
`way wall. By localizing stress deformation and flexion in the
`wire at a hinged joint 28 located in this first half of the leg.
`sufficient stress is applied so that the Nitinol wire at the
`hinged joint undergoes a phase transformation from the
`austenitic state to the martensitic state and reaches the
`superelastic plateau. As the hinged joints 28 experience
`stress variations within the range encompassed by the super-
`elastic plateau. they flex as shown in FIG. 3 and cause the
`legs 22 to provide a substantially uniform contact pressure
`against the passageway wall. Thus if the hinged joint 28 in
`each leg 22 is formed to have substantially the same cross-
`sectional area. each leg will engage the wall of the vena cava
`with substantially the same contact pressure regardless of
`the variations in leg length and deflection. This is illustrated
`by the chart of FIG. 4 which shows the contact pressure
`curve for legs without the hinged joint 28 versus the curve
`for legs with the hinged joint. Since the hinged joint is in the
`stress induced martensitic state while the remainder of the
`leg is in the austenitic state. flexure at the joint not only
`causes the leg to exert a constant force over a range of
`deflections. but alsoreduces the potential for fatigue frac-
`tures of the filter legs due to cyclic respiratory. cardiovas-
`cular or postural motions.
`To quantify the efl‘ect of adding a superelastic hinged joint
`to the filter leg. in—vitro force measurements were conducted
`on lengths of Nitinol wire with and without hinged joints.
`The wires were maintained at 37° C. in a water bath and
`were deflected through distances that are anatomically rel—
`evant. These deflections were correlated to equivalent caval
`diameters. Unhinged filter wire samples exerted forces that
`depend on deflection (see upper curve of FIG. 4). In this
`experiment. the force ranged between 7.5 and 10.5 gm over
`the expected range of vena cava sizes between 12 and 36
`mm diameter. In contrast. hinged joint wire samples exerted
`a force that was insensitive to deflection (lower curve of
`FIG. 4). in this instance at a value of 3.5 gm. The force level
`is determined by the diameter of the joint segments. the
`length of the segments. and their displacement from the
`pivot point.
`In the past. Nitinol filters. stents. and other medical
`devices designed for expansion into contact with the wall of
`a vascular or other body passageway had to be sized to
`conform to the cross-sectional area of the passageway. for a
`device which was significantly larger than the passageway
`
`Page 5 of 7
`
`Page 5 of 7
`
`

`

`5.776.162
`
`5
`
`would exert excessive contact pressure on the walls thereof.
`To prevent this. each device had to be manufactured in a
`large number of sizes. By forming Nitinol medical devices
`with the superelastic hinged joint 28 in accordance with the
`present invention. a reduced number of device sizes are
`required. By placing a hingedjoint orjoints on each segment
`of the medical device which contacts the wall of a
`
`passageway. a single device can be used for passageways of
`varying cross-sectional areas. The increased stress on a
`segment resulting from contact with a smaller passageway
`would be localized at the hinged joint 28 and the hingedjoint
`would cause the segment to engage the walls of the smaller
`passageway with substantially the same contact pressure that
`would be applied to the walls of a larger passageway. Thus
`a single device could be effectively used with passageways
`of different cross-sectional areas so long as the stress range
`for the superelastic plateau of the hinged joint
`is not
`exceeded.
`
`In FIG. 1. superelastic hingedjoints 28 were formed in the
`legs 22 of the filter 10. These hinged joints could also be
`provided as shown in the Nitinol wire on opposite sides of
`each loop 20. as these loops also engage the walls of a vein.
`The superelastic hinged joints 28 may be effective when
`formed in the expandable section of any Nitinol medical
`device. For example. FIGS. 5 and 6 illustrate a stent 32
`which includes a skeletal frame 34. preferably formed from
`a single Nitinol wire 36. The wire includes a plurality of
`abutting straight portions 38 which are joined to each other.
`as by welding or by other attachment means. When the
`frame 34 is expanded in the austenitic state. it becomes
`relatively rigid. and substantially tubular in configuration.
`Ends 40. 42 of the single wire 36 are disposed in one of the
`straight portions 38. such that there are no exposed wire flee
`ends. disposed within or extending from the flame 34. The
`abutting and elongated straight portions of the wire facilitate
`the use of strong elongated welds to securely join the wire
`portions together. The wire 36 may be formed of any desired
`cross-sectional shape. In the flame. straight portions 38 of
`the joined wire segments are disposed. relative to the tubular
`configuration of the frame. circumferentially thereof. The
`wire abuts itself only at the straight portions 38 and does not
`cross itself at any point. Accordingly. the frame walls. that
`is. walls 44 of a tubular body portion 46 of the frame have
`a thickness equal to the diameter of the wire 36.
`The stent includes the body portion 46 and looped finger
`portions 48 extending generally axially from one. or both.
`ends of the body portion. The finger portions also expand
`radially outwardly against the wall of a vascular passageway
`in which the stent is located.
`
`The tubular body portion 46 comprises a mesh formed by
`the wire 36. the mesh comprising a plurality of intercon-
`nected cells 50 which are preferably of a polygonal con-
`figuration when viewed in plan. providing spaced. substan—
`tially parallel straight sides to form the aforementioned
`straight portions 38. The cells 50. when polygonal. are
`preferably of a hexagonal configuration. which readily pro-
`vides expansion and rigidity characteristics desirable in the
`structure and operation of the device. Preferably. the stent
`comprises six of the polygonal cells 50 circumferentially
`and an even number of the polygonal cells along its length.
`thereby facilitating formation of the stent by the single wire
`36.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`It is important to note that each cell 50 is formed by two
`straight portions 38 which are substantially parallel to the
`central longitudinal axis of the stent or stent section of which
`the cell is a part. Each end of the cell is closed by an end wall
`
`65
`
`6
`or end walls 52 which extend between adjacent ends of the
`straight portions; the end walls being disposed at an angle to
`the central longitudinal axis of the stent or stent section
`containing the cell. It is these end walls which expand and
`contract as the cell undergoes a phase transformation
`between the austenitic and martensitic states. The straight
`portions 38 remain parallel to the central longitudinal axis of
`the stent as the stent expands or collapses.
`The cell structure and orientation within the stent 32 is
`very important to the proper expansion and compression
`characteristics of the stent. Since cell joinder is accom-
`plished solely at adjoining straight portions 38. the expan-
`sion of the stent radially and outwardly from the central
`longitudinal axis thereof places minimal stress on the con-
`nections between cells. The straight portions 38. being
`parallel to the longitudinal axis of the stent or stent section.
`do not significantly change in configuration as the stent is
`collapsed and expanded.
`Since the sole connection between cells is along these
`straight portions. the connection is not subjected to tension
`or shear force during expansion and compression of the stent
`in a manner which would tend to stress and break the
`connection. The end walls 52. which are inclined relative to
`the central long'tudinal axis of the stent or stent section. are
`the portions of the cell which provide the radial memory
`force during expansion. and the longitudinally oriented
`connections between the cells causes the cells to distribute
`
`this radial memory force evenly around the stent. It is the
`pliability of the end walls at temperatures below the tem~
`perature transformation level which cause the cell straight
`portions 38 to move together as the stent is compressed. and
`it is these same end walls which become relatively rigid but
`resiliently deformable to return the stent
`to its thermal
`memory shape at temperatures above the temperature trans-
`formation level. As these end walls maintain the straight
`portions 38 of the cells substantially parallel to the longi—
`tudinal axis of the stent in all configurations of the stent.
`these straight portions are not significantly biased or
`stressed.
`
`To adapt a stent 32 of a single size for use in vessels of
`different cross-sectional areas. the expandable portions of
`the stent. like those of the blood clot filter 10. are provided
`with superelastic hinged joints 28. As shown in FIGS. 5 and
`6. a hinged joint 28 can be formed at the apex between the
`wall sections 54 and S6 of each end wall 52 where maximum
`
`stress occurs. Alternatively. a hinged joint 28 can be formed
`in each wall section 54 and 56 in closely spaced relationship
`to the apex therebetween. Also. a hinged joint 28 can be
`formed in the Nitinol wires on either side of the end loop 58
`for each of the fingers 48.
`I claim:
`
`1. A medical appliance of shape memory material for
`implantation in a vessel for engagement with walls of the
`vessel comprising:
`a body formed of thermal shape memory material having
`a temperature transformation level below which said
`material
`is in a martensitic state and said body is
`relatively pliable and compressible and above which
`said material is in an austenitic state and said body is
`self—expandable to a substantially rigid. pre-
`compressed configuration. said shape memory material
`in the austenitic state being capable of transformation
`to the martensitic state in response to induced stress.
`said body having a longitudinal axis and including seg-
`ments which expand outwardly away from said longi-
`tudinal axis when said thermal shape memory material
`is in a thermally induced austenitic state.
`
`Page 6 of 7
`
`Page 6 of 7
`
`

`

`5.776.162
`
`7
`
`and at least one superelast hingedjoint formed in at least
`one of such segments to localize strain to which said
`segment is subjected at said joint. to permit said joint
`to undergo a stress induced phase transformation to a
`martensitic state while the remainder of said segment is
`in a temperature induced austenitic state. said joint
`being formed by reducing the cross—sectional area of
`said segment in a localized area of said segment.
`2. The medical appliance of claim 1 wherein said shape
`memory material is Nitinol.
`3. The medical appliance of claim 2 wherein said segment
`includes an elongate section of Nitinol wire. said superelas—
`tic joint being formed by reducing the cross- sectional area of
`said wire to cause strain at said joint when the wire is in the
`temperature induced austenitic state to induce a transforma—
`tion of said joint to the stress induced martensitic state while
`the remainder of the wire remains in the austenitic state.
`
`4. The medical appliance of claim 3 wherein the tempera-
`ture transformation level of said wire is about body tem—
`perature.
`5. The medical appliance of claim 2 which comprises a
`blood clot filter having a body including a plurality of wire
`portions. said filter having a leading end located on said
`longitudinal axis. said wire portions being confined together
`at said filter leading end to form a tip. and being confined
`together at a median place on said axis spaced from said
`filter leading end. said wire portions having free ends remote
`from said tip and said median place. said Wire portions
`between said median place and said free ends defining legs.
`and a superelastic joint formed in each such leg between the
`median place and free end thereof.
`6. The medical appliance of claim 5 wherein said super-
`elastic joint is formed in each such leg between said median
`place and a point halfway between said median place and the
`free end of said leg.
`7. The medical appliance of claim 6 wherein said legs in
`the austenitic state of said Nitinol wire bow outwardly from
`said median place and include a foot extending at an angle
`at the free end of each said leg.
`8. The medical appliance of claim 6 wherein each wire
`portion between said filter tip and said median place forms
`a loop. said loops overlapping at least the adjacent two said
`loops to form a filter basket.
`9. The medical appliance of claim 8 wherein each such
`wire portion forming said loop includes a first wire section
`extending outwardly from said median place a second wire
`section extending outwardly from said filter tip and a curved
`section extending between said first and second wire sec-
`tions to form the end of said loop. a superelastic joint being
`formed in each said first. and second wire sections spaced
`from said curved section.
`10. The medical appliance of claim 6 wherein said filter
`includes coaxial first and second filter baskets. each said
`
`filter basket being generally symmetrical about said longi-
`tudinal axis and opening away from said filter leading end
`11. The medical appliance of claim 2 which comprises a
`stent including an elongate body member having a longitu—
`dinal axis with a skeletal frame of said wire formed to define
`an elongate chamber which extends through said body
`member. the skeletal frame being formed to assume a first
`expanded configuration relative to said longitudinal axis in
`
`8
`the austenitic state of said wire and to be collapsible toward
`said longitudinal axis to a second collapsed configuration in
`the martensitic state of said wire. said skeletal frame further
`
`being formed to define a plurality of interconnected open
`cells with each of said cells including two substantially
`parallel. spaced side walls which are substantially parallel to
`said longitudinal axis in both the first expanded configura-
`tion and the second collapsed configuration of said skeletal
`frame and end walls extending between said sidewalls at an
`angle to said longitudinal axis. and a superelastic joint
`formed in each of said end walls. said cells being arranged
`around said elongate chamber with sidewalls of adjacent
`cells arranged in adjacent coextensive relationship. said cells
`joined together by an attachment connecting adjacent. coex-
`tensive cell sidewalls.
`this being the only connection
`between said cells.
`
`12. The medical appliance of claim 11 wherein said cell
`end walls each include first and second wall sections. each
`said wall section having a first end joined to one of the
`sidewalls of said cell. said wall section extending at an angle
`to the sidewall to which the first end thereof is joined. and
`each said wall section having a second end opposite to said
`first end. the second ends of said first and second wall
`sections being joined. each said wall section having a
`superelastic joint formed therein.
`13. The medical appliance of claim 12 wherein said
`superelastic joint in each of said first and second wall
`sections is located adjacent the second ends thereof.
`14. The medical appliance of claim 11 wherein said wire
`forming said skeletal frame is configured to form finger
`portions extending axially from an end of said body member.
`each said finger portion including at least one superelastic
`joint formed therein.
`15. The medical appliance of claim 12 wherein each such
`finger portion is configured in the form of a loop having first
`and second spaced wire sections extending axially from an
`end of said body and a curved section extending between
`said first and second wire sections to form an outermost end
`
`of said loop. a superelastic joint being formed in each said
`first and second wire sections spaced from said curved
`section.
`
`16. The medical appliance of claim 2 which comprises a
`stent including a wire skeletal frame of generally tubular
`configuration. said skeletal frame comprising only a single
`Wire. said frame including straight axially-extending por—
`tions of said wire joined together along the lengths of said
`straight axially-extending portions. and disposed side by
`side defining a circumference of said stent. wherein said
`frame includes a substantially tubular body portion and
`finger portions extending from an end of said body portion.
`said finger portions extending axially of said body portion
`and comprising endless looped portions of said single wire.
`each such finger portion including first and second spaced
`wire sections extending axially from an end of said body
`portion and a curved section extending between said first
`and second wire sections to form an outermost end of said
`finger portion. a superelastic joint being formed in each said
`first and second wire sections spaced from said curved
`section.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`Page 7 of 7
`
`Page 7 of 7
`
`