Patent Abstract:
A surgical device for cutting a portion of a body comprising a knife capable of moving from a first position to a second position which is spaced apart from the first position; a smart memory material (SMM) capable of going from one physical state to another physical state; and an activating apparatus which is in communication with the smart memory material and which can cause the change in the physical state of the smart memory material, which change in state causes the movement of the knife thereby facilitating cutting of the desired body portion.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a division of U.S. patent application Ser. No. 11/977,005, filed Oct. 23, 2007, which is a divisional application of U.S. patent application Ser. No. 10/366,170, filed Feb. 13, 2003 and issued as U.S. Pat. No. 7,287,682 on Oct. 10, 2007, which is a continuation-in-part application to U.S. patent application Ser. No. 10/348,087 filed Jan. 20, 2003, all hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention pertains to a surgical device for attaching staples to a portion of a body. The invention also pertains to a surgical device for cutting a portion of a body. 
         [0003]    The invention also pertains to smart memory materials that can change from one physical phase to another physical phase upon application of a stimulus and the use of those materials in a surgical device. 
       BACKGROUND OF THE INVENTION 
       [0004]    Medical stapling devices for endoscopic or laparoscopic surgery employ very complex mechanisms. Frequently, the devices rely on a set of cam bars and the like to eject the surgical staples from the staple cartridge. (See U.S. Pat. No. 3,499,591.) Complex linkages contained within the body of the device are used to articulate the staple cartridge and an anvil into position during the surgical procedure. (See U.S. Pat. No. 6,250,532.) The range of motion, flexibility and size of such stapling devices are restricted by these mechanisms. Examples of complicated apparatus for applying surgical staples to attach an object to body tissue is described in U.S. Pat. Pub. 2002/0117534, published Aug. 29, 2002. The apparatus requires complex mechanical actuating mechanisms for rotating and articulating the surgical device and then to cause the staple to be ejected from a store of staples. A flexible connection (fire wire) with a high level of fatigue life is needed between the push rod and the pusher plate at the pivot point of the articulated joint. In a similar fashion, see U.S. Pat. No. 6,250,532. The devices described in the patents contain complex linkages to eject the staples from the staple cartridge/magazine limiting the range-of-motion for the articulated end of the device. In some of the devices, cam bars are used to deploy the staples. The ability of the cam bars to deflect or flex is limited to approximately +/−45° of movement. Additional, when operating at the extremes of this travel, early fatigue failure of the cam bars is possible. 
         [0005]    The power required to actuate the device of the invention disclosed herein is supplied to the staple cartridge through very small and flexible wires. Because of the small size and flexibility, the required space and packaging requirements are significantly less in comparison to the cam bars described in the patents of the prior art. 
         [0006]    Polymeric materials having smart memory characteristics are described in “Shape Memory Polymers”: A. Yondlen, S. Kelch Angen, Chem Int. Ed. 2002, 41(12), pp. 2034-2057. The use of smart memory materials is discussed in U.S. Pat. No. 5,509,923. See also U.S. Pat. No. 6,388,043, herein incorporated by reference. 
         [0007]    An apparatus for endoscopically applying body staples to body tissue is described in U.S. Pat. No. 5,484,095. 
         [0008]    Other patents which are generally related to surgical devices or smart memory materials are recited below. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 ISSUED/ 
               
               
                   
                 PATENT NO./ 
                 PUBLISHED 
               
               
                   
                 PUBLICATION NO. 
                 APPL&#39;N. DATE 
               
               
                   
                   
               
             
             
               
                   
                 U.S. Pat. No. 5,236,437* 
                 Aug. 17, 1993 
               
               
                   
                 U.S. Pat. No. 5,242,458 
                 Sep. 7, 1993 
               
               
                   
                 U.S. Pat. No. 5,411,519 
                 May 2, 1995 
               
               
                   
                 U.S. Pat. No. 5,431,323* 
                 Jul. 11, 1995 
               
               
                   
                 U.S. Pat. No. 5,467,911 
                 Nov. 21, 1995 
               
               
                   
                 U.S. Pat. No. 5,484,095 
                 Jan. 16, 1996 
               
               
                   
                 U.S. Pat. No. 5,509,923 
                 Apr. 23, 1996 
               
               
                   
                 U.S. Pat. No. 5,636,780 
                 Jun. 10, 1997 
               
               
                   
                 U.S. Pat. No. 5,645,209 
                 Jul. 8, 1997 
               
               
                   
                 U.S. Pat. No. 5,681,330 
                 Oct. 28, 1997 
               
               
                   
                 U.S. Pat. No. 5,711,472 
                 Jan. 27, 1998 
               
               
                   
                 U.S. Pat. No. 5,797,959 
                 Aug. 25, 1998 
               
               
                   
                 U.S. Pat. No. 5,810,881 
                 Sep. 22, 1998 
               
               
                   
                 U.S. Pat. No. 6,019,758 
                 Feb. 1, 2000 
               
               
                   
                 U.S. Pat. No. 6,159,146 
                 Dec. 12, 2000 
               
               
                   
                 U.S. Pat. No. 6,250,532 B1 
                 Jun. 26, 2001 
               
               
                   
                 U.S. Pub. 2001/0007057 A1 
                 Pub. Jul. 5, 2001 
               
               
                   
                 U.S. Pub. 2001/0030219 A1 
                 Pub. Oct. 18, 2001 
               
               
                   
                 U.S. Pub. 2002/0072759 1 
                 Pub. Jun. 13, 2002 
               
               
                   
                 U.S. Pub. 2002/0096550 1 
                 Pub. Jul. 25, 2002 
               
               
                   
                 U.S. Pub. 2002/0117534 A1 
                 Pub. Aug. 29, 2002 
               
               
                   
                 U.S. Pat. No. 6,488,196 B1 
                 Dec. 3, 2002 
               
               
                   
                   
               
             
          
         
       
     
         [0009]    It is an object of the present invention to employ a surgical device for cutting a portion of a body where the surgical device has a knife that is capable of moving from a first to a second position which positions are spaced apart and to utilize a smart memory material which functions as described above; namely, utilizing an activating apparatus which is a communication with the smart memory material and by virtue of the change in the physical state can cause the movement of the knife thereby facilitating the cutting of the desired body portion. 
         [0010]    It is also an object of the present invention to describe a method of performing a surgical operation employing the above-described surgical device for cutting a portion of the body. 
       SUMMARY OF THE INVENTION 
       [0011]    Described is a surgical device for cutting a portion of a body comprising a knife capable of moving from a first position to a second position which is spaced apart from the first position; a smart memory material (SMM) capable of going from one physical state to another physical state; and an activating apparatus which is in communication with the smart memory material and which can cause the change in the physical state of the smart memory material, which change in state causes the movement of the knife thereby facilitating cutting of the desired body portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a top view of the surgical device of the present invention. 
           [0013]      FIG. 2  is a side-sectional view of the surgical device of the present invention showing movement of the anvil in an open phantom view. 
           [0014]      FIG. 3  is a side-sectional view of the surgical device of the present invention showing the smart memory material aligned with a store of staples. 
           [0015]      FIG. 4  is a schematic view of the surgical device of the present invention in a ready state. 
           [0016]      FIG. 5  is a schematic view of the surgical device of the present invention in an engaged state depicting the attachment of the staples and movement of the surgical knife. 
           [0017]      FIG. 6  is a side-sectional view of one embodiment of the surgical device of the present invention in the ready state. 
           [0018]      FIG. 6A  is a side-sectional view of one embodiment in the engaged state; namely, the staples are secured towards the anvil. 
           [0019]      FIG. 7  is a side-sectional view of the surgical device of the present invention depicting the surgical knife in a recessed area. 
           [0020]      FIG. 8  is a side-sectional view of the surgical device of the present invention showing the surgical knife in an engaged position, out of the recessed area. 
           [0021]      FIG. 9  is a side-sectional view of a second embodiment of the surgical device of the present invention in a ready state. 
           [0022]      FIG. 10  is a side-sectional view of the second embodiment of the surgical device of the present invention in an engaged view with the staples secured. 
           [0023]      FIG. 11  is a sectional view through lines  11 - 11  of  FIG. 3 . 
           [0024]      FIG. 12  is a sectional view along the lines  12 - 12  of  FIG. 3 . 
           [0025]    An alternative embodiment of the invention is shown in  FIGS. 13-15  and  17 - 19 .  FIG. 13  is a side-sectional view of an alternative embodiment of the present invention. 
           [0026]      FIG. 14  is a side-sectional view of an alternative embodiment of the present invention wherein the surgical knife is in a first position prior to a surgical cutting operation. 
           [0027]      FIG. 15  is a side-sectional view of an alternative embodiment of the present invention wherein the surgical knife is in a second position from the first position of  FIG. 14  wherein the surgical knife has moved from the first position to the second position. 
           [0028]      FIG. 16  is another embodiment of the invention. 
           [0029]      FIG. 17  is a sectional view taken along the lines  17 - 17  of  FIG. 13 . 
           [0030]      FIG. 18  is a sectional view taken along the lines  18 - 18  of  FIG. 13 . 
           [0031]      FIG. 19  is a perspective view of a wedge with surgical knife utilized in the present invention. 
           [0032]      FIG. 20  is an alternative embodiment of the wedge with surgical knife utilized in the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Definitions: 
       [0033]    Smart memory material (SMM) means a material or composition that can move from a first to a second physical state and then back to its desired original physical state by activation or stimuli. The change in state may result in an increase in volume of the SMM. 
         [0034]    An “activating apparatus” means an apparatus that can stimulate the SMM thereby changing the state. The stimuli can be the application of heat and/or electrical current to SMM or some other mechanism that can effectuate the change in physical state. One example of physical state change is going from a martensite phase to an austenite phase. 
         [0035]    The application of smart memory material can simplify a surgical stapling device into four basic components: a staple cartridge, an anvil for staple closure, an energy/power source (remote or local) and a switch/trigger (remote or local). The staple cartridge contains the surgical staple, a surgical blade and a SMM actuator/driver. The actuator/driver is used to drive the surgical staple from the cartridge, through the tissue and into contact with the anvil to initiate closure of the staples. The actuator/driver is also used to drive the surgical blade to create an incision in the tissue. The energy/power source is to supply the thermal energy or magnetic field to elicit a response of the smart materials actuator/driver and is triggered by the switch. 
         [0036]    The flexibility of this concept provides several advantages over current devices as follows:
       Staple actuator/driver can be located in the staple cartridge with staple   Surgical blade and actuator/driver may be incorporated in staple cartridge   Staple cartridge and anvil may be affixed to any device/handle for positioning during procedure   Staple cartridge and anvil mechanism may be adapted to endoscopic or laparoscopic surgical procedures   Staple cartridge is not limited in length by a mechanical actuation device   The staple cartridge may be of various cross sections to fit the surgical application   The surgical device may work with any form or size staple   Staple cartridge may contain one, two, . . . to n staples in one, two, . . . n rows   Staple cartridge may be configured to staple in linear, circular, concave, convex, parabolic or zigzag patterns, and the like   The device facilitates driving individual staples from the staple cartridge sequentially, alternately and any combination thereof, and the like   The device facilitates driving multiple staples or sets of staples in one operation   The device facilitates driving sets of staples from a staple cartridge in a variety of configurations: single, multiple or alternating rows   The device may be utilized to tack surgical incisions       
 
         [0050]    The surgical device herein is designed in such a way that it may be attached to any type of handle or device to articulate/manipulate its position and/or orientation. If the handle or device has the ability to articulate +/−180° (yaw) and rotate 360°, the desired development can be articulate through these extremes. This is possible because of the simplicity of the interface between the staple cartridge and the handle/device. The interface need only contain a method to hold the staple cartridge and an electrical connector. The electrical connector can be nothing more than electrical contains that are engaged by the staple cartridge when it is attached to the handle/device. The electrical connector is used to supply a voltage via small wires from the switch which is connected to the energy source. The electrical connector, integral to the staple cartridge, connects to the SMM contained in the cartridge to eject the staple when the voltage is supplied via the switch. 
         [0051]    In the various embodiments, similar components use the same reference numerals. 
         [0052]    For a first embodiment  FIGS. 1 and 2  show the top sectional and side cross section of one embodiment for a surgical (stapling) device  20 . The surgical (stapling) device  20  has an energy source  21 , contained in the body  27  of the device, a switch  22  that triggers the energy source, an anvil  23 , a handle  26  to actuate the anvil  23  and a staple-actuator cartridge  24 . There is also upper cover  33  and lower cover  35 . 
         [0053]    The handle  26  is pivoted about pin  25 . The anvil  23  pivots about pin  28  and is connected to the handle  26  by pin  29 , which rides in a slot  30  in the body  27 . As handle  26  is rotated from the opened ( FIG. 2 ) to the closed position ( FIGS. 1 and 3 ), the anvil  23  is then rotated from an open position to a closed position to clamp tissue (not shown) between the surface of the anvil  23  and the upper surface  31  of the staple-actuator cartridge  24 . 
         [0054]    The energy source  21 , in a generic sense, is any source of power that initiates or elicits a response in a smart memory material. Examples are not limited to but include a voltage being applied directly to SMM to create a current that generates heat, a voltage being applied to a coil to generate heat or a magnetic field to stimulate the smart memory material. The energy source may also encompass any electrical, fluid, magnetic or chemical reaction that can be used to elicit a response from a smart memory material. The energy source may be a heating or cooling source. 
         [0055]    In the staple-actuator cartridge  24 , there is a plurality of staples  40  contained in a plurality of slots  41 , as shown in  FIGS. 6 and 6A . The plurality of staples  40  may be configured in single row or parallel rows (not shown). In the staple-actuator cartridge  24 , a plurality of staples  40  are located in a plurality of slots  41  against the forward walls  42  and aft walls  43  of slots  41 . The forward walls  42  and aft walls  43  act, as guides for staples  40  and pushers  49 . The staples  40  are located in the downward position  44  against upper surface  45  of pushers  49 . The plurality of pushers  49 , is generally equivalent to the number of slots  41  and plurality of staples  40  having grooves in which a driver  50  is contained. The driver  50  is formed from smart memory material, for the embodiment shown in  FIGS. 6 ,  6 A and runs from the forward end  51  of the staple-actuator cartridge  24  to the aft end  52  of the staple-actuator cartridge  24 . The SMM driver  50  is attached to the energy source  21  at connector  46 . 
         [0056]      FIGS. 4 and 5  show a block diagram for the control logic for the embodiment in  FIGS. 6 and 6A . 
         [0057]    When switch  22  is moved from the neutral position to the forward position, the energy source  21  will apply a voltage to the driver  50 . The voltage in this instance can only be applied after the safety interlock(s)  51  are closed. As the voltage passes into driver  50 , the resistance of the smart memory material will begin to generate heat. As the heat (energy) increases, the smart memory material will begin to go into a phase change such as from martensite to austenite. As this phase change occurs, driver  50  will begin to contract, causing the plurality of pushers  49  to move upward. As the plurality of pushers  49  move upward the plurality of staples  40  will begin to be ejected from the staple-actuator cartridge  24  and make contact with anvil  23 . As driver  50  continues to contact, a force sufficient to completely drive the plurality staples  40  from the staple-actuator cartridge  24  and against anvil  23  to cause the plurality staples  40  to deform into their closed position  41  as shown in  FIGS. 5 and 6A , securing the tissue (not shown). By closed position is meant that the legs of the staple are crimped, preferably together in slots  61  securely fastening the tissue to itself or to a mesh or substrate (not shown). 
         [0058]    Contained in the staple-actuator cartridge  24 , are driver  60 , pusher  61  and surgical blade  62  as shown in  FIGS. 5 ,  7  and  8 . When switch  22  is moved from the forward position through the neutral position into the rearward position, the energy source  21  will apply a voltage to driver  60 . The voltage in this instance preferably is applied after the safety interlock indicating completed staple ejection is closed. As the voltage passes into driver  60 , the resistance of the smart memory material will begin to generate heat. As the heat (energy) increases, the smart memory material will begin to go into a phase change from martensite to austenite. As this phase change occurs, driver  60  will begin to contract, causing pusher  61  to move upward. As driver  60  continues to contract, sufficient force is generated to drive pusher  61  upward, in turn driving surgical blade  62  into its upwardmost position as shown in  FIG. 8 . As the surgical blade  62  is driven upward, it can make an incision into the tissue between the rows of staples. 
         [0059]    An alternative embodiment is shown in  FIGS. 9 and 10 . In the staple-actuator cartridge  24 , there is a plurality of staples  40  contained in a plurality of slots  41 . From this point forward in this embodiment, the device will be described in the singular since for clarification. 
         [0060]    In the staple-actuator cartridge  24 , the staple  40  is located in slot  41  against the forward wall  70  and aft wall  71 . Staple  40  is located in the downward position  72 . The SMM driver  75  is folded in such a way as to form an “S” shaped forward leg  76  and aft leg  77 . The driver  75  is trapped between staple  40 , the reaction surface  80 , forward wall  70  and aft wall  71 . When the energy source  21  applies a voltage (energy) to the driver  75 , forward leg  76  and aft leg  77  will expand. As forward leg  76  and aft leg  77  expand, the upper segment (in the shape of a bar)  78  of the driver  75  reacts against the bottom leg  81  of staple  40  and reaction surface  80 . As the forward leg  76  and aft leg  77  expand, the forward end  82  and aft end  83  of upper bar  78  are guided by the forward wall  70  and aft wall  71  of staple-actuator cartridge  24 . As the forward leg  76  and aft leg  77  expand, the staple  40  is moved linearly until it contacts the surface of the anvil  23  to initiate closure of the staple  40 . The forward leg  76  and aft leg  77  expand until staple  40  is ejected from staple-actuator cartridge  24  and forward staple leg  85  and aft staple leg  86  are fully closed or crimped as shown in  FIG. 10 , securing the tissue and/or mesh or substrate (not shown). 
         [0061]    The surgical stapling device can be configured to eject the staples from the staple-actuator cartridge individually or in any combination. A solid-state logic controller in the stapling device handle can facilitate this feature which one of ordinary skill in the art can assemble. 
         [0062]    It is to be appreciated that the staple-actuator cartridge is not limited to linear forms. Because of the flexibility of the smart material (i.e., shape memory alloys and shape memory polymers), the staple-actuator cartridge can take on any form: circular, concave, convex, parabolic, zigzag or the like. The cross sectional shape of the staple-actuator cartridge can also be tailored to meet the surgical need. 
         [0063]    Another embodiment of the present invention is that depicted in  FIGS. 13-15 . 
         [0064]    The surgical device  100  has handle  106  and anvil  102 . The device contains the energy source  108  which is connected to the SMM material  110  retained within assembly  112  having a top portion  114  and a bottom portion  116 . The anvil  102  has an extension portion  118  that is engagement with the SMM material  110 . As the SMM material moves, the anvil  102  moves upward when viewing  FIG. 13  causing arm  120  to rotate upward. 
         [0065]    In the embodiment depicted in  FIG. 13 , a surgical blade  122  is attached to or a portion of a wedge  124  (best shown in  FIG. 19 ) which has attached thereto the SMM material  110 . The wedge has angled surface  126  to indicate the initiation of action. The wedge has a bottom surface  128  and a back side surface  130  which forms approximately a 90° angle at their juncture  132 . The wedge  124  has a top portion  134 , a front portion  136  and side  138 . Side  138  as can be seen from  FIG. 19  is substantially smaller than back side portion  130  reflecting the angled surface  126  from the back portion  134  to the front surface  136 . The wedge  124  has a groove  138  which rides a “T” shaped track. The wedge slides on the track during the cutting operation of the blade. In a resting or first position, the blade  122  is positioned at the front portion  140  of the surgical device which may take any configuration but is shown as a semicircular configuration for ease of insertion into the body portion for ease of handling during a clinical operation. The surgical device  100  has a bottom portion  142 . The SMM material  110  can be secured to the wedge  124  by any convenient mechanism such as by adhesion and the like, with or without the use of heat or other securing method. 
         [0066]    The surgical device  100  has a wedge receiving section  150  in which top portion  152  receives the blade  122  and bottom portion  154  which receives wedge segment  124 . The blade receiving slot  153  is shown in  FIG. 17 . 
         [0067]    As the wedge  124  moves from the position on the right as shown in  FIG. 13  to the end section  150 , the front portion of the wedge surfaces  136  &amp;  126  initiation movement against pushers  160  and therefore against the staples  162  and against the bottom surface  164  of the anvil thereby engaging body tissue. After the staples engage the tissue, the blade  122  will cut the tissue. 
         [0068]      FIGS. 14 and 15  are further details of the surgical device of  FIG. 13 .  FIG. 14  indicates that the surgical knife  122  is on the right portion of the apparatus of the surgical device where the SMM material  110 A is circled about pulley  170  which rotates about pivot point  104 . The surgical knife moves from the right to the left as shown in  FIG. 15  where the surgical knife  122  fits into the receiving segment  152 . As the surgical knife moves from the right to the left portion of the surgical device, the SMM material  110 A goes from a linear position as shown in  FIG. 14  to a curled position  174  in  FIG. 15 . In other words, by the application of heat the SMM material goes from a linear mode as depicted in  FIG. 14  into a more curled position where the curl is in segment  176  of the  FIG. 15 . The operation of  FIGS. 13-15  indicates that one SMM material  110  operates the anvil to an open or closed position. Another or different SMM material  110 A activates the movement of the surgical knife from the right portion of  FIG. 14  to the left portion of  FIG. 15 . While it is expected that these would be two separate operable SMM materials, it is obvious to one of skill in the art that the materials can be lengthened and there could be separate segments that would have the ability to operate both actions namely the movement of the anvil and the movement of the blade. For convenience, the electrical connections of  FIGS. 13-15  are not supplied in detail but would be clear to one of skill in the art. 
         [0069]      FIG. 16  is a schematic view of another alternative of the present invention. The surgical device  100  of  FIG. 16  is an alternative embodiment of the operation of the wedge  124  and surgical knife  122 . In  FIG. 16 , the heating mechanism  108  is attached to the SMM  110 A. The embodiment shown in  FIG. 16 , however, does not have the pulley arrangement as shown in  FIG. 15 . In the embodiment of  FIG. 16 , the surgical knife moves from the right portion of the surgical device  100  to the left portion of the surgical device stopping at receiving position  150 . The action of the SMM is primarily retained in the horizontal plane of the surgical device  100  without the SMM going around a pulley. In the embodiment of  FIG. 16 , the SMM is primarily in a linearly fashion and during the movement from one phase to another. The SMM can collect in a retaining box  180  in  FIG. 16 . 
         [0070]      FIG. 20  is an alternative embodiment of the wedge with surgical knife utilized in the present invention. 
         [0071]    The wedge  200  is comprised of sloping surfaces  202 A and  202 B.  FIG. 20  is comprised of  FIG. 20A  which is a perspective view of the wedge utilized in the present invention.  FIG. 20B  is a view of  FIG. 20A  from the back.  FIG. 20C  is a view of  FIG. 20A  from the front and  FIG. 20D  is an interior view of  FIG. 20A  showing the attachment of the SMM to the interior portion of the wedge. 
         [0072]    The wedge has exterior side surface  204  of bottom surface  206  and interior surface  208  exterior surfaces are  204 A and  204 B. The surgical knife has a cutting edge  210  and a back portion  212 . Extension  214  of the blade likewise has angles for movement of the wedge when it comes in contact with the pushers for movement of the staples. The angle for surface  214  is comparable to that for surfaces  202 A and B. The SMM  220  is attached to the interior surface  208 A and B of the extension  214  of the surgical knife. The wedge  200  has a front lip  230 . 
         [0073]    It is to be appreciated that the surgical device utilizing its smart memory material need not utilize the knife portion. In that case, the stapling device can operate as described herein. Alternatively, the surgical device need not utilize the staple portion. In which case the knife portion may be utilized as described herein. Preferably, however, the knife and stapling mechanism are utilized together as shown. 
         [0074]    The driver for ejecting the staples from the staple-actuator cartridge is not limited to smart memory alloy materials. A smart memory polymer can also provide the actuating force and displacement. Some smart memory materials include Nitinol (an acronym for Nickel Titanium Naval Ordnance Laboratory) which is a family of intermetallic materials, which contain a nearly equal mixture of nickel (about 55 wt. %) and titanium. Some of those alloy compositions are superelastic materials such as alloy N, S and C and others are actuator materials, such as alloy B, M, H and Flexinol (trademark of Nitinol Devices and Components for nickel titanium intermetallic alloys). 
         [0075]    Nitinol exhibits unique behavior. The two terms used to describe this behavior are “Shape Memory” and “Superelasticity”. 
         [0076]    SHAPE MEMORY: Shape memory effect describes the process of restoring the original shape of a plastically deformed sample by heating it. This is a result of a crystalline phase change known as “thermoelastic martensitic transformation”. Below the transformation temperature, Nitinol is martensitic. The soft martensitic microstructure is characterized by “self-accommodating twins”, a zigzag like arrangement. Martensite is easily deformed by de-twinning. Heating the material converts the material to its high strength, austenitic condition. The transformation from austenite to martensite (cooling) and the reverse cycle from martensite to austenite (heating) do not occur at the same temperature. There is a hysteresis curve for every Nitinol alloy that defines the complete transformation cycle. The shape memory effect is repeatable and can typically result in up to 8% strain recovery. 
         [0077]    SUPERELASTICITY: Martensite in Nitinol can be stress induced if stress is applied in the temperature range above Af (austenite finish temperature). Less energy is needed to stress-induce and deform martensite than to deform the austenite by conventional mechanisms. Up to 8% strain can be typically accommodated by this process. Since austenite is the stable phase at this temperature under no-load conditions, the material springs back to its original shape when the stress is removed. This extraordinary elasticity is also called “pseudoelasticity” or transformational “superelasticity”. The typical stress-strain curve of a properly processed Nitinol alloy shows the loading and unloading plateaus, recoverable strain available, and the dependence of the loading plateau on the ambient temperature as is well known in the art. The loading plateau increases with the ambient temperature. As the material warms above the austenite finish temperature, the distinctive superelastic “flag” curve is evident. Upon cooling, the material displays less elasticity and more deformation until it is cooled to where it is fully martensite; hence, exhibiting the shape memory property and recovering its deformation upon heating. Nitinol alloys are superelastic in a temperature range of approximately 50 degrees above the austenite finish temperature. Alloy composition, material processing, and ambient temperature greatly effect the superelastic properties of the material. For medical devices binary Nitinol alloys, when processed correctly, are at their optimum superelastic behavior at body temperature. 
         [0078]    Nitinol Devices &amp; Components manufactures binary Nitinol materials with Afs ranging from −15 degrees centigrade to +100 degrees centigrade for both superelastic and shape memory applications. 
         [0079]    Smart memory materials can also be metallic alloys of copper, zinc and aluminum or iron, nickel and aluminum, and the like. 
         [0080]    Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims, the inventions may be practiced otherwise than as specifically described. For example, numerous mechanisms may be available for articulating and modifying the size and configuration of the surgical device. Moreover, the reference numerals are merely for convenience and are not intended to be in any way limiting. Similarly, the components of the invention can be arranged relative to one another in a variety of configurations other than those shown.

Technology Classification (CPC): 0