United States Patent [19]
`Morales
`
`US005893852A
`[11] Patent Number:
`[45]. Date of Patent:
`
`5,893,852
`Apr. 13, 1999
`
`[54] STENT CRIMPING TOOL AND METHOD OF
`USE
`
`WO 98/19633 5/1998 WIPO .
`
`OTHER PUBLICATIONS
`U.S. Patent Application Serial No. 08/795,335 filed Feb. 4,
`ºr. Application Serial No. 08/837,771 filed Apr. 22.
`tºº. Application Serial No. 08/089,936 filed Jul. 15.
`jºr Application Serial No. 08/962,632 filed Nov. 3.
`[21] Appl. No.: 09/069,011
`[22] Filed:
`Apr. 28, 1998
`The eXTraordinary Stent, C.R. Bard Brochure (Undated).
`[51] Int. Cl* … A61M 29/00
`Primary Examiner—Michael Buiz
`[52] U.S. Cl. … 60.6/108
`Assistant Examiner—Vikki Trinh
`[58] Field of Search ............................ 606/198, 191–195,
`Attorney, Agent, or Firm—Fulwider Patton Lee & Utecht.
`f
`606/1, 108; 29/515, 516
`LLP
`ABSTRACT
`[57]
`A stent crimping tool for firmly and uniformly crimping a
`conventional or radioactive stent onto a balloon catheter is
`constructed from a proximal section rotatably connected to
`a distal section, the two cylindrical sections forming the
`transparent housing. A cylindrical cavity having a tapered
`end is formed into the proximal section. Inside the cavity is
`affixed a transparent cylindrical collar having radial slots
`leading to a central passage extending along its axis, and a
`conical end that fits into the tapered end. Teeth made of
`trapezoidal shape flat plates each having an angular proxi
`mal edge and a radiused edge slide into their respective slots
`in the collar. A transparent screw feed having a hollow core
`and a slotted head that receives the radiused edge of each
`tooth/plate is threaded to the distal section. A balloon
`catheter is passed through a passage in the proximal section
`and the collar and an uncrimped stent positioned in the
`hollow core of the screw is loaded thereon. Rotating the
`distal section of the housing advances the screw and plates
`toward the tapered cavity, which has angled walls that force
`the plates to converge radially inward. This convergence
`causes the radiused edges of the plates to collectively crimp
`the stent onto the balloon.
`
`[75] Inventor: Stephen A. Morales, Mountain View,
`Calif.
`
`[73] Assignee: Advanced Cardiovascular Systems,
`Inc., Santa Clara, Calif.
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`696.289
`3/1902 Williams .
`4,468,224
`8/1984 Enzmann et al. .
`4,576,142
`3/1986 Schiff .
`4,644,936 2/1987 Schiff .
`4,681,092
`7/1987 Cho et al. .
`4,697,573 10/1987 Schiff.
`4,901,707 2/1990 Schiff.
`4,907.336 3/1990 Gianturco .
`5,132,066 7/1992 Charlesworth et al. .
`5,133,732 7/1992 Wiktor .
`5,183,085 2/1993 Timmermans .
`5,189,786 3/1993 Ishikawa et al. .
`5,437,083
`8/1995 Williams et al. .
`5,546,646 8/1996 Williams et al. .
`5,626,604 5/1997 Cottone, Jr. ......................... 60.6/108 X
`5,630,830 5/1997 Verbeek .
`5,653,691
`8/1997 Rupp et al. .
`5,738,674 4/1998 Williams et al. .
`5,746,764 5/1998 Green et al. .
`5,783,227
`7/1998 Dunham .
`5,785,715
`7/1998 Schatz .
`FOREIGN PATENT DOCUMENTS
`159065 2/1921 United Kingdom .
`WO 98/14120 4/1998 WIPO .
`
`
`
`22 Claims, 6 Drawing Sheets
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`Page 1 of 13
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`EDWARDS LIFESCIENCES EX. 1007
`Edwards Lifesciences v. Boston Scientific Scimed
`U.S. Patent No. 6,915,560
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`1
`STENT CRIMIPING TOOL AND METHOD OF
`USE
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`5,893,852
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`to ensure the proper crimping of a stent onto a catheter in a
`uniform and reliable manner.
`This crimping is often done by hand, which can be
`unsatisfactory due to the uneven application of force result
`ing in non-uniform or loosely applied crimps. In addition, it
`is difficult to visually judge when a uniform and reliable
`crimp has been applied.
`Some self-expanding stents are difficult to load by hand
`onto a delivery device such as a catheter. Furthermore, the
`more the stent is handled the higher the likelihood of human
`error, which would be antithetical to a properly crimped
`stent. Accordingly, there is a need in the art for a device for
`reliably crimping a stent onto a catheter.
`There have been attempts at devising a tool for crimping
`a stent onto a balloon delivery catheter. An example of such
`a tool comprises a series of plates having substantially flat
`and parallel surfaces that move in a rectilinear fashion with
`respect to each other. A stent carrying catheter is disposed
`between these surfaces, which surfaces crimp the stent onto
`the outside of the catheter by their relative motion and
`applied pressure. The plates have multiple degrees of free
`dom and may have force-indicating transducers to measure
`and indicate the force applied to the catheter during crimp
`ing of the stent.
`Another stent loading tool design is comprised of a
`tubular member housing a bladder. The tubular member and
`bladder are constructed to hold a stent that is to be crimped
`onto a balloon catheter assembly. Upon placement of the
`stent over the balloon portion of the catheter, a valve in the
`loading tool is activated to inflate the bladder. The bladder
`compresses the stent radially inward to a reduced diameter
`onto the balloon portion of the catheter to achieve a snug fit.
`In this way, the stent is crimped onto the distal end of a
`balloon catheter with a minimum of human handling. The
`foregoing stent crimping tools are disclosed in, for example,
`U.S. Pat. Nos. 5.437,083 and 5.546,646 to Williams et al.
`Yet another stent crimping tool is known in the art as the
`BARD XT, which is actually a stent loader. It is constructed
`from a rigid, tubular body with a ball at one end connected
`to a plurality of long, thin strips passing through the tubular
`body. An uncrimped stent is placed over the plurality of
`long, thin strips, which hold the stent in an expanded state.
`The balloon portion of a catheter is inserted into the cylin
`drical space formed by the plurality of strips. When the user
`pulls the ball while holding the tubular body against the
`stent, the strips are slid from beneath the stent and the stent
`is transferred onto the balloon portion.
`Still another conventional stent crimping tool is manu
`factured by JOHNSON & JOHNSON and appears similar to
`a hinged nutcracker. Specifically, the tool is comprised of
`two hand operated levers hinged at one end and gripped in
`the palm of the hand at the opposite end. A cylindrical
`opening holding a crimping tube is provided through the
`mid-portion of the tool to receive therein a stent loaded onto
`a balloon catheter. The crimping operation is performed by
`the user squeezing the handle thereby pressing the crimping
`tube which in turn pinches the stent onto the balloon
`catheter.
`While the prior art devices are suitable for crimping stents
`onto balloon catheters, they suffer from problems such as
`non-uniform crimping forces, resulting in non-uniform
`crimps. Consequently, they are unsuitable for use by phy
`sicians in a cath lab who desire to crimp the stent onto the
`balloon catheter.
`SUMMARY OF THE INVENTION
`Both PTCA and PTA procedures have become common
`place in treating stenoses or lesions in blood vessels and
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`BACKGROUND OF THE INVENTION
`The present invention relates to an apparatus for loading
`a tubular graft, such as a stent, onto the distal end of a
`catheter assembly of the kind used. for example, in percu
`taneous transluminal coronary angioplasty (PTCA) or per
`cutaneous transluminal angioplasty (PTA) procedures.
`In typical PTCA procedures, a guiding catheter is percu
`taneously introduced into the cardiovascular system of a
`patient through the brachial or femoral arteries and advanced
`through the vasculature until the distal end of the guiding
`catheter is in the ostium. A guide wire and a dilatation
`catheter having a balloon on the distal end are introduced
`through the guiding catheter with the guide wire sliding
`within the dilatation catheter. The guide wire is first
`advanced out of the guiding catheter into the patient’s
`coronary vasculature and the dilatation catheter is advanced
`over the previously advanced guide wire until the dilatation
`balloon is properly positioned across the arterial lesion.
`Once in position across the lesion, a flexible and expandable
`balloon is inflated to a predetermined size with a radiopaque
`liquid at relatively high pressures to radially compress the
`atherosclerotic plaque ofthe lesion against the inside of the
`artery wall and thereby dilate the lumen of the artery. The
`balloon is then deflated to a small profile so that the
`dilatation catheter can be withdrawn from the patient’s
`vasculature and the blood flow resumed through the dilated
`artery. As should be appreciated by those skilled in the art.
`while the above-described procedure is typical, it is not the
`only method used in angioplasty.
`In angioplasty procedures of the kind referenced above,
`restenosis of the artery may develop over time, which may
`35
`require another angioplasty procedure, a surgical bypass
`operation, or some other method of repairing or strengthen
`ing the area. To reduce the likelihood of the development of
`restenosis and to strengthen the area, a physician can implant
`an intravascular prosthesis for maintaining vascular patency,
`commonly known as a stent, inside the artery at the lesion.
`The stent is crimped tightly onto the balloon portion of the
`catheter and transported in its delivery diameter through the
`patient’s vasculature. At the deployment site, the stent is
`expanded to a larger diameter, often by inflating the balloon
`portion of the catheter. The stent also may be of the
`self-expanding type.
`Since the catheter and stent travel through the patient's
`vasculature, and probably through the coronary arteries, the
`stent must have a small delivery diameter and must be firmly
`attached to the catheter until the physician is ready to
`implant it. Thus, the stent must be loaded onto the catheter
`so that it does not interfere with delivery, and it must not
`come off the catheter until it is implanted.
`In procedures where the stent is placed over the balloon
`portion of the catheter, it is necessary to crimp the stent onto
`the balloon portion to reduce its diameter and to prevent it
`from sliding off the catheter when the catheter is advanced
`through the patient’s vasculature. Non-uniform crimping
`can result in sharp edges being formed along the now uneven
`surface of the crimped stent. Furthermore, nonuniform stent
`crimping may not achieve the desired minimal profile for the
`stent and catheter assembly. Where the stent is not reliably
`crimped onto the catheter, the stent may slide off the catheter
`and into the patient’s vasculature prematurely as a loose
`foreign body, possibly causing blood clots in the
`vasculature, including thrombosis. Therefore, it is important
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`3
`coronary arteries. In approximately 35% to 40% of the
`procedures, restenosis may develop requiring a further
`angioplasty, atherectomy or bypass procedure to return the
`patency of the vessel. Intravascular stents are now being
`deployed after PTCA and PTA procedures, and after
`atherectomies, in order to help prevent the development of
`restenosis. Importantly, such stents, mounted on the balloon
`portion of a catheter, must be tightly crimped to provide a
`low profile delivery diameter, and to ensure that the stent
`stays on the balloon until the balloon is expanded and the
`stent is implanted in the vessel. The present invention is
`directed to a crimping tool that can repeatedly provide a
`uniform and tight crimp to ensure the low profile diameter
`of the stent on the balloon portion of the catheter, and to
`ensure that the stent remains firmly attached until it is
`implanted in the vessel by expanding the balloon.
`In a preferred embodiment, the present invention is
`directed to a tool for crimping a stent onto a balloon catheter,
`comprising a housing including a proximal section and a
`distal section, wherein the proximal section includes a
`cylindrical cavity having a tapered end, and an opening in
`communication with the cavity; a cylindrical collar having a
`conical end conforming to the tapered end when the collar
`is positioned therein, wherein the collar further includes a
`plurality of slots extending radially and along a length
`thereof and intersecting at the conical end, and having a
`passage therethrough that is in communication with the
`opening in the proximal section; a plurality of teeth having
`a plate shape, each tooth/plate having an angular proximal
`edge, and being slidably disposed inside a corresponding
`slot in the collar, each plate having a radiused edge extend
`ing into the passage; and a screw feed extending into the
`passage wherein the screw feed includes radial slots that
`lead into a hollow core, and wherein the slots receive the
`respective radiused edges of the plates extending therein,
`and wherein the screw feed is threaded to the distal section
`of the housing.
`An uncrimped stent is manually loaded into the hollow
`core. At the opposite end of the tool, the balloon catheter is
`inserted through the opening into the cylindrical cavity at the
`proximal section of the housing, which leads into the hollow
`core of the screw holding the uncrimped stent.
`Ideally, the invention is held in the user's dominant had
`while the other hand advances a balloon catheter into the
`hollow core holding the stent. In the preferred embodiment,
`the present invention crimping tool is made from a trans
`parent or translucent material so that the user can watch the
`insertion of the balloon catheter. Looking into the hollow
`core of the screw feed, the user manually aligns and loads
`the uncrimped stent on to the balloon catheter.
`Alternatively, the present invention tool can be advanced
`over a guide wire. Next, the balloon catheter is advanced
`along the guide wire and fed into the hollow core holding the
`uncrimped stent. The stent is then loaded onto the balloon
`portion of the catheter.
`In the exemplary embodiment, a mandrel or a wire is
`inserted into the tool with the balloon catheter. The mandrel
`helps the balloon catheter maintain its shape during the
`crimping process. Otherwise, the crimp on the stent may be
`imperfect and there may be damage to the balloon catheter
`when the stent is crimped too far. In an alternative
`embodiment, a mandrel may be built into the tool so that it
`extends therefrom, and the catheter is guided onto the
`mandrel and into the correct position every time.
`With the stent loaded onto the balloon portion of the
`catheter, a surgeon or a technician in a cath lab can manually
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`yet precisely crimp the stent using the present invention tool.
`Holding the tool in his or her hands, the surgeon twists the
`distal section of the housing to perform the crimp.
`The rotational motion of the distal section of the housing
`is translated into linear displacement of the screw feed by the
`following process. First, the distal section and the proximal
`section are clipped together to permit relative rotation but to
`prevent relative linear displacement. Second, the collar is
`affixed to the proximal section so it cannot rotate, and the
`threaded screw feed likewise cannot rotate due to its linkage
`with the collar through the teeth/plates. Third, the rotation of
`the distal section causes the screw feed to rotate out of the
`distal section and to simultaneously advance linearly toward
`the proximal end of the tool.
`As this occurs, the angular proximal edge of each tooth/
`plate is carried by the advancing screw feed into engagement
`with the tapered end, resulting in contact and sliding dis
`placement of the teeth/plates radially inward toward a cen
`tral axis of the tool. In unison, the radiused edges of the
`teeth/plates converge on the underlying stent to crimp the
`stent onto the balloon catheter. The radiused edges of the
`plates thus act as crimping jaws.
`The present invention also features an optional visual
`indicator to assist the user in crimping the stent. Specifically.
`once the balloon catheter and the stent are aligned, the distal
`section is twisted or screwed until a marking on the exterior
`of the distal section reaches a red line painted on the exterior
`of the proximal section. The red line provides a visual cue
`to the user to stop twisting because the crimping step has
`been completed. Twisting the distal section beyond the red
`line creates a greater likelihood of damage to the balloon
`catheter due to excessive crimping.
`After the crimping step is performed, the user unscrews
`the distal section of the housing so that the balloon catheter
`and the crimped stent can freely slide through the passage in
`the tool. If the balloon catheter and crimped stent do not
`easily slip through the crimping tool, then the foregoing
`crimping procedure needs to be repeated. To be sure, the
`process is repeated until the crimped stent safely passes
`through the crimping tool and into the patient.
`The present invention represents an important step toward
`the handling of fragile stents. It also represents a significant
`reduction of the user's exposure to radioactive stents,
`because the walls of the present invention crimping tool are
`preferably thicker than % inch so that they provide adequate
`shielding from the radioactive stent.
`In addition, the radioactive stent can be packaged.
`shipped, and stored inside the present invention crimping
`tool for the length of its half life. When the stent is to be
`implanted, the user simply loads the stent—which is already
`inside the tool—onto the balloon catheter, twists and
`untwists the housing to crimp and release the stent, and feeds
`the crimped stent along the guide wire into the patient’s
`vasculature. Thus, some benefits of the present invention
`tool are that it provides safe storage for the stent prior to
`implantation, while conveniently transforming into a crimp
`ing tool that does not require direct handling of the fragile
`Stent.
`The present invention tool is highly versatile. First, it is
`ideal for handling stents because the tool has a larger
`diameter than the stent, but is still centered on the Stent's
`axis. Accordingly, the present invention tool allows physi
`cians to correctly crimp a stent onto a balloon.
`Second, it effectively establishes a reliable stent crimp on
`a balloon of any diameter. The reason is that the tool has an
`opening approximately twice the diameter of the stent to
`accommodate the stent and the balloon catheter.
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`Third, the radiused edge of each tooth/plate can be
`designed to press the stent and the balloon catheter down to
`a specified diameter. This dimension, of course, can be
`altered by changing the radius of the edges machined into
`the plates. Fourth, the present invention tool is intended to
`be used on a variety of stent lengths. The total length of a
`preferred embodiment tooth/plate is over thirty-five milli
`meters long, thereby accommodating the lengths of the
`stents currently on the market.
`The present invention crimping tool can be used with any
`stent system which is released without a delivery system.
`Although the present invention tool is intended to be a
`disposable device, the tool may eventually be sold alone
`because its design is robust enough to undergo many
`repeated uses.
`In summary, the present invention tool protects doctors
`from the dangers of beta radiation emitted from radioactive
`stents. Also, the present invention tool is capable of homo
`geneously and precisely crimping a stent onto a balloon
`20
`catheter. Such a crimping tool is highly useful to
`cardiologists, for example. Such physicians are constantly
`concerned with proper deployment of the stent within the
`patient that it is desirable to have a consistently and reliably
`crimped stent. The present invention tool is further a time
`saver, because the stent crimping procedure can be per
`formed fairly efficiently and quickly. These and other advan
`tages of the present invention will become apparent from the
`following detailed description thereof when taken in con
`junction with the accompanying exemplary drawings.
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a side elevational view, partially in section,
`depicting a stent that has been crimped onto a delivery
`catheter and disposed within a vessel.
`FIG. 2 is a cross-sectional view of a preferred embodi
`ment of the present invention stent crimping tool exposing
`the internal assembly of components.
`FIG. 3 is a side elevational, exploded view of the crimping
`tool shown in FIG. 2.
`FIGS. 4A and 4B are cross-sectional and rear elevational
`views, respectively, of a preferred embodiment proximal
`section of the housing.
`FIGS.5A and 5B are front elevational and side elevational
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`views. respectively, of a preferred embodiment collar show
`ing the orthogonal slots formed therein.
`FIGS. 6A and 6B are side-elevational and front eleva
`tional views, respectively, of a preferred embodiment distal
`section of the housing.
`FIGS. 7A, 7B. and 7C are top plan, front elevational, and
`side elevational views, respectively, of a preferred embodi
`ment tooth having an angular proximal edge.
`FIGS. 8A and 8B provide front elevational and side
`elevational views, respectively, of a preferred embodiment
`screw feed.
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`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`FIG. 1 illustrates intravascular stent 10 which is mounted
`onto delivery catheter 11. Stent 10 generally comprises a
`plurality of radially expandable cylindrical elements 12
`disposed coaxially and interconnected by members 13 dis
`posed between adjacent cylindrical elements 12. Delivery
`catheter 11 has an expandable portion or balloon 14 for
`expanding stent 10 within coronary artery 15 or other vessel
`such as saphenous veins, carotid arteries, arteries, and veins.
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`Artery 15, as shown in FIG. 1, has dissected lining 16 which
`has occluded a portion of the arterial passageway.
`Delivery catheter 11 onto which stent 10 is mounted is
`essentially the same as a conventional balloon dilatation
`catheter for angioplasty procedures. Balloon 14 may be
`formed of suitable materials such as polyethylene, polyvinyl
`chloride, polyethylene terephthalate and other like poly
`mers. In order for stent 10 to remain in place on balloon 14
`during delivery to the site of the damage within artery 15,
`stent 10 is compressed onto balloon 14.
`An optional retractable protective delivery and alignment
`sleeve 20 may be provided to further ensure that stent 10
`stays in place on balloon 14 of delivery catheter 11 and to
`prevent abrasion of the body lumen by the open surface of
`stent 10 during delivery to the desired arterial location. A
`removable tubular shape carrier (not shown) might be used
`in place of or in addition to sleeve 20 for the same purposes.
`Other means for securing stent 10 onto balloon 14 may also
`be used, such as providing collars or ridges on the ends of
`the working portion, i.e., the cylindrical portion of balloon
`14.
`In order to implant stent 10, it is first mounted onto
`inflation balloon 14 on the distal extremity of delivery
`catheter 11. Stent 10 is crimped down onto balloon 14 to
`ensure a low profile. The present invention addresses this
`crimping procedure.
`The catheter-stent assembly can be introduced into the
`patient’s vasculature through processes known in the art.
`Briefly, guide wire 18 is disposed across the arterial section
`where an angioplasty or atherectomy has been performed
`requiring a follow-up stenting procedure. In some cases, the
`arterial wall lining may be detached so that guide wire 18 is
`advanced past detached or dissected lining 16 and the
`catheter-stent assembly is advanced over guide wire 18
`within artery 15 until stent 10 is directly under detached
`lining 16. Prior to inflation of balloon 14, delivery sleeve 20
`is retracted to expose stent 10. Depending on the balloon and
`stent assembly, a delivery sleeve may be unnecessary. Bal
`loon 14 of delivery catheter 11 is then inflated using an
`inflation fluid. Expansion of balloon 14 in turn expands stent
`10 against artery 15. Next, balloon 14 is deflated and
`catheter 11 is withdrawn leaving stent 10 to support the
`damaged arterial section. As mentioned above. in order to
`ensure proper seating of stent 10 on balloon 14, and to
`ensure proper deployment of stent 10 at the site of the
`damage within artery 15, the stent crimping procedure is
`important.
`FIG. 2 is a sectional view of a preferred embodiment of
`the present invention stent crimping tool 22. As recognized
`in this sectional view, the present invention stent crimping
`tool 22 is characterized by a preferably cylindrical housing
`made of two interlocking parts. Those parts are, namely,
`proximal section 24 and distal section 26 of the housing. The
`two parts are preferably interconnected by inserting a por
`tion of proximal section 24 into corresponding space 34
`formed into distal section 26, and engagement of lip 36
`within groove 38 of distal section 26. With this type of
`interconnection, relative rotation between proximal section
`24 and distal section 26 is possible while relative linear
`displacement is limited insofar as lip 36 is locked within
`groove 38.
`FIG. 2 thus provides a cross-sectional view of a preferred
`embodiment of the present invention in its assembled form.
`FIG. 3, on the other hand, is an exploded side elevational
`view of the major components of the present invention. In
`particular, FIG. 3 as well as FIG. 2 show the present
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`invention being comprised of, moving from one end to the
`opposite end: proximal section 24, teeth 30, collar 32 screw
`feed 28 and distal section 26. In FIG. 3. intravascular stent
`10, delivery catheter 11, and guide wire 18 have been
`omitted for clarity.
`FIGS. 4A and 4B provide a sectional and a rear eleva
`tional view, respectively, of proximal section 24. As seen in
`the drawings, proximal section 24 is preferably cylindrical
`in shape having cylindrical cavity 40, wherein cylindrical
`cavity 40 includes tapered end 42 leading to opening 44. In
`the preferred embodiment, tapered end 42 has a 45 degree
`taper from a central axis of proximal section 24. Also seen
`in FIGS. 4A and 4B is lip 36 which, as seen in FIG. 2, helps
`secure proximal section 24 to distal section 26. To facilitate
`assembly with collar 32, proximal section 24 has a five
`degree coarse thread 72 cut into the wall of cylindrical cavity
`40.
`FIGS. 6A and 6B provide a side elevational and an end
`view, respectively, of distal section housing 26. In the
`preferred embodiment shown here, distal section 26 has an
`ergonomic cylindrical shape with cylindrical cavity 40 and
`groove 38 used to catch lip 36. Distal section 26 also
`includes boss 46 with tubular passage 48 extending there
`through. The end portion of tubular passage 48 extending
`through boss 46 is tapped to a '4"–20 threads to accept a
`threaded screw.
`FIGS. 8A and 8B provide a front elevational and a side
`elevational view, respectively, of screw feed 28. As a device
`that translates rotational motion to linear motion, screw feed
`28 is comprised of head 50 and shaft 52, the latter being cut
`with %"-20 threads to match the corresponding threads
`formed in boss 46 of distal section 26.
`Screw feed 28 further includes hollow core 54 that
`extends a length of head 50 and shaft 52. Hollow core 54
`serves as a chamber to hold stent 10. In addition, screw feed
`28 includes preferably four orthogonal slots 56. These slots
`56 are designed to receive and retain teeth 30.
`FIGS. 7A, 7B, and 7C provide a top plan, a front
`elevational, and a side elevational view, respectively, of a
`preferred embodiment tooth 30. Tooth 30 is essentially a flat,
`almost trapezoidal shape plate having angular proximal edge
`58 formed at preferably 45 degrees in one corner of the plate.
`Along angular proximal edge 58 and along distal edge 60
`are “T” formations. The “T” formation along distal edge 60
`of tooth 30 conforms and slides into complementary “T”
`45
`cuts in slots 56 of screw feed 28. A “T” formation is best
`seen in distal edge 60 of FIG. 7A, and a corresponding “T”
`cut is best seen formed in head 50 of FIG. 8B. The “T”
`formation along angular proximal edge 58 conforms and
`slides into a complementary “T” cut formed in orthogonal
`slot 66 of collar 32. As seen in FIG. 2, one function of the
`“T” formations is to slidably retain teeth 30 in their respec
`tive slots 56 when teeth 30 are assembled to screw feed 28.
`Radiused edge 62 extends into hollow core 54 of screw
`feed 28. As best seen in FIG.7B, at the crest of radiused edge
`62 is a groove having radius 74 that defines the final outside
`diameter of stent 10 after undergoing the crimping proce
`dure. In a preferred embodiment, this radius 74 is in the
`order of 0.007 inch. Needless to say, changing the size or
`shape of radius 74 changes the final outside diameter of the
`crimped stent.
`In an alternative embodiment (not shown), the radiused
`edge may have a contour. The contour from a cross-sectional
`point of view, either axially or radially, may have a
`rectangular, arcuate, diamond, saw tooth, sinusoidal, ridged,
`or like profile known in the art. Such radiused edges help
`improve stent retention.
`
`8
`FIGS. 5A and 5B provide a front elevational and a side
`elevational view of a preferred embodiment of collar 32. As
`best seen in those drawings, collar 32 has a generally
`cylindrical shape with a conical end 64 angled at approxi
`mately 45 degrees from a horizontal axis. Accordingly,
`conical end 64 and the cylindrical body of collar 32 are
`adapted to fit within tapered end 42 and cylindrical cavity
`40.
`As mentioned earlier, four orthogonal slots 66 are formed
`into collar 32 through which four teeth 30 pass. Angular
`proximal edge 58 of each tooth 30 is retained in collar 32 by
`“T” formations formed along angular proximal edge 58
`sliding inside “T” cuts formed in orthogonal slots 66.
`At a distal end of collar 32 are five degree coarse threads
`68 intended to match threads 72 in proximal housing 24.
`Threads 68 and 72 retain collar 32 immovably inside cylin
`drical cavity 40 of proximal housing 24. Collar 32 further
`includes tubular passage 70 in communication with opening
`44. Passage 70 extends the entire length of collar 32.
`All together, the foregoing structures are assembled
`according to that shown in FIGS. 2 and 3. More precisely,
`teeth 30 are slid into corresponding slots 66 of collar 32 and
`extend into slots 56 formed in head 50 of screw feed 28.
`Thus joined, screw feed 28 cannot rotate because it is linked
`via teeth 30 to collar 32, which is tightly screwed into
`proximal section 24.
`25
`Head 50 of screw feed 28 extends into passage 70 within
`collar 32 while threaded shaft 52 is screwed into boss 46 of
`distal section housing 26. Uncrimped intravascular stent 10
`is placed in hollow core 54. The major pieces of the housing
`are assembled as shown in FIG. 2 so that lip 36 latches or
`snaps into groove 38 while collar 32 is immovably mounted
`to cylindrical cavity 40 of proximal section housing 24.
`The next step is to load stent 10 onto delivery catheter 11.
`This is accomplished by inserting guide wire 18 into open
`ing 44 of proximal section 24 and through passage 70 of
`collar 32, extending out hollow core 54. The present inven
`tion tool 22 can then be advanced along guide wire 18.
`Balloon catheter 11 and a mandrel (not shown) are advanced
`over guide wire 18 into passage 70. In an alternative
`embodiment, the mandrel may be built into the present
`inventio