Abstract:
A stent loading device is configured to perform a method of loading a stent into a delivery tube that comprises loading a stent into an opening of a crimping device. The stent has an initial uncompressed diameter. The method further comprises crimping the stent via the crimping device in a manner reducing the diameter of the stent from the initial diameter. Still further, the method comprises forcing the stent out of the opening of the crimping device and into a passageway of a delivery tube while oscillating the crimping device. The passageway of the delivery tube has a diameter that is less than the initial diameter of the stent and receives the stent in its compressed state.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The application is a nonprovisional application and claims priority to U.S. Provisional Application Ser. No. 61/520,984, which was filed on Jun. 20, 2011, and which is hereby incorporated herein by reference in its entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       Appendix 
       [0003]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The present invention pertains to devices and methods of compressing and loading stents into delivery tubes, such as catheters. More particularly, the present invention pertains to devices and methods that utilize vibrations or oscillations to reduce the friction required to forcibly insert radially compressed stents into delivery tubes. Using the present invention, a wider range of sizes and lengths of stents can be loaded into delivery tubes without being damaged during the process. 
         [0006]    2. General Background 
         [0007]    Several types of stents are commonly used to prevent blood vessels from collapsing. Such stents are typically radially compressed prior to insertion and are placed in delivery tubes that allow the stents to be passed through blood vessels during placement to minimize the evasiveness of the implantation procedures. Once properly positioned, the stents are forced out of the delivery tubes and radially expand to thereby maintain a fluid passageway through the blood vessels. 
         [0008]    There are two primary types of stents. One type of stent is formed of traditional metal alloys and is radially expanded by inflating a balloon around which it was radially compressed. Once expanded, the balloon is deflated and withdrawn from the blood vessel. More recently, self-expanding stents have been used that utilize Shape Memory Alloys (SMA) to form stents that automatically expand when exposed to body temperature. An example of an SMA is nickel titanium alloy (typically referred to as nitinol). SMA stents are originally formed in their radially expanded state and must be radially compressed to be inserted into delivery tubes. When radially compressed, it can become difficult to load stents into delivery tubes without damaging the stents, due to the frictional forces resulting from the stents resiliency. Traditionally, radially compressed stents are either pulled or pushed into the delivery tubes. When frictional forces are high, the pushing or pulling forces can damage the stents. 
         [0009]    To prevent damage to unique geometry and long stents during loading procedures, a so called “inchworm” technique is often used to load such stents into delivery tubes. Using that technique, rather than compressing the entire stent, small portions of the stent are reduced in diameter and are pushed into a delivery tube one portion at a time. This method requires skilled operators and normally greatly extends the loading time, thereby making it undesirable. 
         [0010]    In view of the foregoing, prior art techniques of loading stents into delivery tubes have limitations and drawbacks. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention overcomes some of the difficulties associated with loading stents into delivery tubes. The invention induces vibrations or oscillations in the crimping head of a stent loading device, which greatly reduces the force required to push or pull compressed stents into delivery tubes. 
         [0012]    In one aspect of the invention, a method of loading a stent into a delivery tube comprises loading a stent into an opening of a crimping device. At this stage, the stent has an initial uncompressed diameter. The method further comprises crimping the stent via the crimping device in a manner reducing the diameter of the stent from the initial diameter. Still further, the method comprises forcing the stent out of the opening of the crimping device and into a passageway of a delivery tube while oscillating the diameter of the opening of the crimping device. The passageway of the delivery tube has a diameter that is less than the initial diameter of the stent and receives the stent in its compressed state. 
         [0013]    In another aspect of the invention, a stent loading device comprises a crimping device, a stent extractor, and a programmable control system. The crimping device has a crimping device having an opening that is configured and adapted to receive a stent, the opening of the crimping device having an adjustable diameter. The stent extractor is configured and adapted to move linearly relative to the opening of the crimping device in a manner such that the stent extractor can force a stent out of the opening of the crimping device. The programmable control system can control the diameter of the opening of the crimping device and can control the linear movement of the stent extractor relative to the opening of the crimping device. The programmable control system is programed to oscillate the diameter of the opening of the crimping device and to simultaneously cause the stent extractor to move linearly relative to the opening of the crimping device. 
         [0014]    In yet another aspect of the invention, a method of loading a stent into a delivery tube comprises loading a stent into an opening of a crimping device. At this stage, the stent has an initial uncompressed diameter. The method further comprises crimping the stent via the crimping device in a manner reducing the diameter of the stent from the initial diameter. Still further, the method comprises forcing the stent out of the opening of the crimping device and into a passageway of a delivery tube while oscillating the crimping device. The passageway of the delivery tube has a diameter that is less than the initial diameter of the stent and receives the stent in its compressed state. 
         [0015]    Further features and advantages of the present invention, as well as the operation of the invention, are described in detail below with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0016]      FIG. 1  depicts a perspective view of the preferred embodiment of a stent loading device in accordance with the invention, showing the front, left, and top sides thereof. 
           [0017]      FIG. 2  depicts a perspective view of the stent loading device shown in  FIG. 1 , showing the front, right, and top sides thereof. 
           [0018]      FIG. 3  is similar to  FIG. 2  with the front and top housing panels removed from the stent loading device. 
           [0019]      FIG. 4  depicts a perspective view of the crimping device showing the front, right, and top sides thereof. 
           [0020]      FIG. 5  is similar to  FIG. 4  with some components removed and some shown in exploded view. 
           [0021]      FIG. 6  depicts a perspective view of the crimping device showing the rear, left, and top sides thereof. 
           [0022]      FIG. 7  depict a cross-section of the crimping device, taken down the middle of the device between its left and right sides. 
       
    
    
       [0023]    Reference numerals in the written specification and in the drawing figures indicate corresponding items. 
       DETAILED DESCRIPTION 
       [0024]    A preferred embodiment of a stent loading device in accordance with the invention is shown in  FIGS. 1 and 2 . The stent loading device  10  comprises a housing  12 , a crimping device  14 , a stent extractor  16 , and a delivery tube holder  18 . The stent loading device  10  also comprises a programmable control system  20  (see  FIG. 3 ) that is operatively connected to the crimping device  14 , the stent extractor  16 , and the delivery tube holder  18 , and that comprises operating buttons  22 , a digital display  24 , and a central processing unit  26 . 
         [0025]    Like prior art stent loaders, the crimping device  14  is configured to receive a stent and to thereafter radially compress the stent. As such, the crimping device  14  has an adjustable diameter opening  28  (the cross-section of the opening actually has a dodecagon perimeter, and the term diameter as used herein should be interpreted to broadly cover any polygonal or segmented-arc perimeter opening). A plurality of movable wedge members  30  bound the opening  28  and are moved relative to each other by truss members  32 . The opposite ends of the truss members  32  extend into a slotted fixed plate  34  and a pivotable slotted plate  36 . The truss members  32  move radially in and out by pivoting the pivotable slotted plates  36  relative to the slotted fixed plates  34 . Each of the pivotable slotted plates  36  is fixed to a crank  38  that extends radially outward therefrom. The end of each crank  38  is attached to threaded linear actuator  40  that comprises a motor  42  that rotationally drives a threaded rod  43  (threads not shown). As the threaded rods  43  rotate, the cranks  38 , along with the pivotable slotted plates  36  pivot about the opening  28  of the crimping device  14  in a manner adjusting the diameter of the opening. Preferably, a load cell  44  operatively connects the threaded rod  43  to its respective crank  38  in a manner such that the crimping force can be interpolated. The motors  42  preferably each comprise an internal sensor (not shown) that measures the rotation of the respective threaded rod  43 . Data from the load cells  44  and other sensors are fed to the central processing unit  26  of the control system  20 . 
         [0026]    The stent extractor  16  comprises a quill rod  46  and is linearly moveable relative to the crimping device  14  along the axis of the crimping device&#39;s opening  28 . The movement of the stent extractor  16  is controlled by the control system  20 . The quill rod  46  has a diameter that is no greater than the compressed diameter of the stents being crimped. As such, the quill rod  46  can be moved into the opening  28  of the crimping device  14  when a stent is compressed in the crimping device and can therefore be used to push the stent out of the crimping device. 
         [0027]    The delivery tube holder  18  lies adjacent the opposite side of the crimping device  14  and is configured to hold a catheter or other form of delivery tube (not shown) that is adapted to hold a stent in a compressed state until the stent is implanted. Like the stent extractor  16 , delivery tube holder  18  is linearly moveable relative to the crimping device  14  along the axis of the crimping device&#39;s opening  28  such that a delivery tube can be positioned immediately adjacent the opening of the crimping device. As such, when the stent extractor  16  pushes a stent out of the crimping device  14 , the stent moves into a delivery tube in its compressed state. The delivery tube holder  18  preferably includes a cooling system that is configured to counteract heat caused by friction so as to maintain SMA stents at temperatures below their shape memory temperatures during the loading process (the crimping device  14  may also comprise such a cooling system). 
         [0028]    While the mechanical structure of the stent loading device  10  may not be novel, unlike prior art stent loading devices, the control system  20  of the device is programed to oscillate the diameter of the opening  28  of the crimping device  14  as it moves the stent extractor  16  to force a stent out of the crimping device and into a delivery tube held in the delivery tube holder  18 . To achieve that, the control system  20  causes the motors  42  of the threaded linear actuators  40  to rapidly change rotational direction. By doing this, the frictional forces between the crimping device  14  and a compressed stent held therein also oscillates and are therefore intermittently less than they otherwise would be. The reduced friction allows unique stent designs and longer length stents to be easily loaded without damaging the stents in the process. Oscillations in the frictional forces can also or alternatively be achieved by vibrating the crimping device  14  using pneumatic, acoustic, eccentric weight, or other common shakers/vibrators (not shown). Thus, “oscillating” the crimping device means moving portions of the crimping device relative to each other or shaking the entire crimping device. In either case, the frictional forces between a crimped stent and crimping device will also oscillate, thereby making it easier to force the stent out of the crimping device. However, direct oscillation of the diameter of the opening  28  of the crimping device  14  is preferred. The oscillations preferably occur at a rate in the range of 50 Hz to 1,000 Hz. The amplitude of the diametric oscillations is preferably between 0.001 and 0.006 inches. By programing the control system  20  to oscillate the rotation of the motors  42  of the threaded linear actuators  40  through a specific arc as measured by the internal sensors of the motors, the diameter of the opening  28  of the crimping device  14  can be precisely controlled, thereby preventing over-crimping the stents. In practice, the present invention reduces the forces required to push or pull compressed stents from the crimping device  14  by as much as fifty percent. 
         [0029]    It should be appreciated that a stent loading device or method in accordance with this invention could be utilized to load non-SMA stents (such as balloon expanded stents). It should also be appreciated that a stent loading device or method in accordance with this invention could pull (rather than push) stents from a crimping device. 
         [0030]    In view of the foregoing, it should be appreciated that the invention has several advantages over the prior art. 
         [0031]    As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents. 
         [0032]    It should also be understood that when introducing elements of the present invention in the claims or in the above description of exemplary embodiments of the invention, the terms “comprising,” “including,” and “having” are intended to be open-ended and mean that there may be additional elements other than the listed elements. Additionally, the term “portion” should be construed as meaning some or all of the item or element that it qualifies. Moreover, use of identifiers such as first, second, and third should not be construed in a manner imposing any relative position or time sequence between limitations. Still further, the order in which the steps of any method claim that follows are presented should not be construed in a manner limiting the order in which such steps must be performed, unless such and order is inherent.