Abstract:
To provide a valve cusp sizer which is small and easy to handle. The present invention relates to a valve cusp sizer  100  for determining the size of a valve cusp depending on the size of a cardiac valve. The valve cusp sizer  100  includes a front surface  10  formed in an arcuate surface form to be abutted against an organism, a back surface  20  positioned on an opposite surface side of the front surface  10,  and a pinching portion  30  protruding from the back surface  20.  By removing a grip member and a grip member attachment portion from a conventional valve cusp sizer in this manner, and by forming the pinching portion  30  to be held by a clamp, tweezers, or the like, it is possible to dramatically miniaturize the valve cusp sizer while maintaining necessary functions of the valve cusp sizer.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a valve cusp sizer for measuring the size of a valve cusp composing a cardiac valve. The valve cusp sizer is used for forming a valve cusp material of the cardiac valve from an artificial membrane or a biomembrane, for example, during an aortic valvuloplasty or an aortic valve reconstructive operation. 
       BACKGROUND ART 
       [0002]    A heart works as a pump that sends a blood to the whole body by way of an aorta. For example, a cardiac valve (aortic valve), that is formed at the exit where the blood flows out from a left ventricle to the aorta, is composed of cup-shaped three valve cusps of a thin membrane. In a state that a fluid pressure of a blood flow is low, inner membranes of the valve cusps are joined to each other to close the cardiac valve, thereby blocking the blood flow. Whereas, when the fluid pressure of the blood flow is increased, the inner membranes of the valve cusps are spaced apart from each other to open the cardiac valve, thereby allowing the blood to flow from the heart into the aorta. Each of the valve cusps has commissure portions corresponding to a left end and a right end thereof, and each of the valve cusps is integrated with an inner wall of the aorta at the commissure portions. 
         [0003]    When arteriosclerosis, etc. proceed along with aging, calcium is deposited to the valve cusps and thereby calcifying and hardening the valve cusps. This phenomenon causes a disease of an aortic valve stenosis in which the movement of the valve cusps is restricted and the valve cusps open insufficiently. As a result, the left ventricle wall becomes thicker to be enlarged. When the thickness of a wall of the cardiac muscle is excessively increased, nutrition and oxygen delivered by the blood flow supplied from the coronary arteries are insufficient. This results in a myocardial ischemia (a state of insufficient nutrition and oxygen) of the heart. Particularly, if the myocardial ischemia is caused when the oxygen demand is increased, for example, during activity, it may possibly cause symptoms such as chest pain and syncope. 
         [0004]    As a result of an earnest study, the present inventor has established an aortic valvuloplasty, instead of a conventional valve replacement, as therapeutics for such a disease. The aortic valvuloplasty is a technique as follows. That is, among the valve cusps hardened due to deposition of calcium, valve cusps that can be used by decalcification are left as much as possible, and only valve cusps that cannot be used are excised to be repaired by replacing the excised valve cusps with another aortic valve formed of autologous biomembrane, etc. In this case, since the valve cusps are formed by an autologous pericardium to be used as a new aortic valve, there is no problem of causing rejection or blood clotting reaction (thrombus) and purchasing an expensive prosthetic valve is not required. In the aortic valvuloplasty, a new valve cusp conforming to the diameter of a patient&#39;s aorta is required to be cutout from a planar pericardium. However, there has been a problem how to determine the size of the new valve cusp conforming to the diameter of the patient&#39;s aorta. 
         [0005]    Therefore, the inventor of the present invention developed a valve cusp forming instrument for measuring the size of a patient&#39;s valve cusp accurately and forming a valve cusp conforming to the diameter of the patient&#39;s aorta (see Patent Document 1). Patent Document 1 discloses a valve cusp forming instrument for using in the aortic valvuloplasty. The valve cusp forming instrument includes a plurality of valve cusp sizers and templates. An example of valve cusp sizer is shown in  FIG. 2  of Patent Document 1. A photograph of an actual valve cusp sizer is shown in  FIG. 8  of the present application. As shown in  FIG. 8  and the like, the conventional valve cusp sizer has a sizer block and a grip member attached to the sizer block. The sizer block has an arcuate surface formed by cutting a column at an angle conforming to the central angle for the commissure portions of the valve cusp. The sizer block is also provided with contact probe portions for positioning both ends of the arcuate surface to the commissure portions of the valve cusp. In the valve cusp forming instrument disclosed in Patent Document 1, each of a plurality of differently-sized sizer blocks are connected to a plurality of grip members to be gripped by hands, as shown in  FIG. 1  of Patent Document 1. 
         [0006]    The aortic valvuloplasty is disclosed in Shigeyuki OZAKI “Jiko Shinmaku Wo Shiyou Shita Daidoumyakuben Keiseijutsu [Aortic valvuloplasty using autologous pericardium]”  Jinko Zoki,  Vol. 39 (2010), No. 3, 157-161. (see Non-Patent Literature 1 below.) Non-Patent Literature 1 discloses a valve cusp sizer including a sizer block and a grip member as described above (see  FIG. 2  of Non-Patent Literature 1). 
       PRECEDING TECHNICAL DOCUMENT 
       [0007]    Patent Document: 
         [0008]    Patent Document 1: Japanese Patent No. 5106019. 
       Non-Patent Literature: 
       [0009]    Non-Patent Literature 1: Shigeyuki OZAKI “Jiko Shinmaku Wo Shiyou Shita Daidoumyakuben Keiseijutsu [Aortic valvuloplasty using autologous pericardium]”  Jinko Zoki,  Vol. 39 (2010), No. 3, 157-161. 
       SUMMARY OF THE INVENTION 
     Technical Problem 
       [0010]    The conventional valve cusp sizer, however, has such a structure that the grip member is attached to each of the differently-sized sizer blocks. This structure makes the entire size of the conventional valve cusp sizer large and makes it hard to handle the conventional valve cusp sizer. That is, as shown in  FIG. 8  of the present invention, a long-extended grip member is necessary for the conventional valve cusp sizer, and an attachment portion for the grip member is necessary to be reserved in a sizer head. Accordingly, it is difficult to insert the sizer head of the conventional valve cusp sizer into a base of the narrow aorta. Further, it is necessary to take care not to injure a vessel wall by contacting the sizer head with the vessel wall. 
         [0011]    In addition, since the conventional valve cusp sizer has the structure that the grip member is attached to each of the differently-sized sizer blocks, the capacity of a container in which a plurality of types of valve cusp sizers are accommodated becomes large as shown in, for example,  FIG. 1  of Patent Document 1. In a case that the container is too large, it is difficult to keep the container at an operator&#39;s hand. Therefore, the plurality of types of valve cusp sizers are kept at a place far from an operation field, and a delivery of the valve cusp sizers is needed between the operator and an assistant each time when another size of valve cusp sizer is needed. Such a delivery of the valve cusp sizers results in a loss of operative time. 
         [0012]    Accordingly, at the present time, a valve cusp sizer which is small and easy to handle is required. 
       Solution to Problem 
       [0013]    The inventor of the present invention diligently studied solutions for the above described problems of the conventional invention and obtained the following knowledge. That is, by removing a grip member and a grip member attachment portion from a conventional valve cusp sizer, and by forming a pinching portion to be held by a clamp, tweezers, or the like, it is possible to dramatically miniaturize the valve cusp sizer while maintaining necessary functions of the valve cusp sizer. The present inventor thought that the problems of the prior arts would be solved based on such knowledge, and completed the present invention. Specifically, the present invention has a structure described below. 
         [0014]    The present invention relates to a valve cusp sizer. The valve cusp sizer is a surgical instrument used for determining (measuring) the size of a valve cusp conforming to the size of a cardiac valve. 
         [0015]    The valve cusp sizer of the present invention includes a front surface  10  having an arcuate surface form to be abutted against an organism, a back surface  20  positioned on an opposite surface side of the front surface  10 , and a pinching portion  30  protruding from the back surface  20 . The front surface  10  is formed in the arcuate surface form so that a central part between left and right ends thereof projects toward a side of the organism. The pinching portion  30  is formed in a shape to be pinched by a surgical instrument. For example, if the pinching portion  30  is formed in a shape having flat surfaces at left and right sides thereof, the pinching portion  30  can be pinched by the surgical instrument. 
         [0016]    Since the valve cusp sizer has the above described structure in which the pinching portion  30  is provided on the back surface  20  thereof, the pinching portion  30  can be pinched by a clamp or tweezers. This structure makes it unnecessary for the valve cusp sizer to be provided with a grip member to be gripped by hands. This grip member is a member occupying the most part of the structure in the conventional valve cusp sizer. Since the grip member may be omitted, the valve cusp sizer of the present invention can be miniaturized dramatically. The valve cusp sizer miniaturized in this manner can be inserted easily into the base of the narrow aorta. Further, a risk of injuring the organism by contacting the valve cusp sizer with the vessel wall of the aorta can be reduced. Moreover, since the valve cusp sizer is miniaturized, a plurality of types (for example, 9 types) of differently-sized valve cusp sizers can be accommodated in a small container. This makes it possible to keep a set of the valve cusp sizers around the operator&#39;s hand during an operation such as aortic valvuloplasty, and results in shortening an operative time. 
         [0017]    In the valve cusp sizer of the present invention, the front surface  10  may preferably have left and right contact probe portions  11 ,  12  at the left and right ends thereof to be contacted with left and right commissure portions of the valve cusp. 
         [0018]    The above described structure, in which the contact probe portions  11 ,  12  are provided on the front surface  10 , makes it possible to determine (measure) the size of the patient&#39;s valve cusp more appropriately. 
         [0019]    In the valve cusp sizer of the present invention, the back surface  20  may preferably be formed in a shape projecting toward the same direction as the front surface  10  (for example, an arcuate surface form). 
         [0020]    The above described structure, in which the back surface  20  is formed in the shape projecting toward the same direction as the front surface  10 , further miniaturizes the valve cusp sizer. That is, since an attachment portion of a grip member is necessary for the conventional valve cusp sizer (see  FIG. 8 ) to be provided on the back surface  20  thereof, the back surface  20  projects toward a direction opposite to the front surface  10 . However, such a shape makes a head portion of the valve cusp sizer large and difficult to be inserted into the narrow aorta. Therefore, in the valve cusp sizer of the present invention, the attachment portion of the grip member has been removed from the back surface  20 , and the back surface  20  has been formed in the shape projecting toward the same direction as the front surface  10  (for example, an arcuate surface form). This structure makes it easy to insert the valve cusp sizer into a narrow portion of the organism. 
         [0021]    In the valve cusp sizer of the present invention, the pinching portion  30  may preferably be formed to have a length by which the pinching portion  30  does not protrude beyond left and right back ends  21 ,  22  of the back surface  20 . 
         [0022]    By defining the length of the pinching portion  30  not to exceed a certain length as the above described structure, the valve cusp sizer can be adjusted in an appropriate size. Namely, by adjusting the length of the pinching portion  30  so that the pinching portion  30  does not protrude beyond the back ends  21 ,  22  of the back surface  20 , it is possible to prevent the pinching portion  30  from touching the vessel wall and from interfering an insertion of the valve cusp sizer into the aorta. 
         [0023]    In the valve cusp sizer of the present invention, at least left and right side surfaces  31 ,  32  of the pinching portion  30  may preferably be formed by a slip stopper  71 , or a nonslip treatment  72  may preferably be applied to the at least left and right side surfaces  31 ,  32  of the pinching portion  30 . 
         [0024]    By making efforts to prevent slipping for the pinching portion  30  as the above described structure, the pinching portion  30  can be pinched by a clamp or tweezers easily. 
         [0025]    In the valve cusp sizer of the present invention, at least a part of the pinching portion  30  may preferably be inclined upwardly. An inclined state of the pinching portion  30  includes a state that the pinching portion  30  stands perpendicular to a placing surface on which the valve cusp sizer is placed. 
         [0026]    The valve cusp sizer of the present invention has a structure to be held from upside by an operator via a clamp or the like. Therefore, if a part of the pinching portion  30  is inclined upwardly as described above, the operator can easily pinch the pinching portion  30 . Further, if a part of the pinching portion  30  is inclined upwardly, it is possible to pinch the pinching portion  30  by a surgical instrument such as Kelly clamp in a state that a grip member of the surgical instrument is parallel to the inclination depending on the inclination angle. As a result, the valve cusp sizer is abutted against the commissure portions at an appropriate angle, thereby reducing a measurement error. 
         [0027]    Preferably, the valve cusp sizer of the present invention may not be provided with a grip member (see  FIG. 8 ) extending upwardly beyond the contact probe portions  11 ,  12  to be held by hands. 
       Effect of the Invention 
       [0028]    According to the present invention, a valve cusp sizer which is small and easy to handle can be provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  is a perspective view showing an example of a valve cusp sizer. 
           [0030]      FIG. 2  is a front view showing an example of the valve cusp sizer. 
           [0031]      FIG. 3  is a plan view schematically showing the valve cusp sizer. 
           [0032]      FIG. 4  is a cross sectional view on line A-A shown in  FIG. 2 . 
           [0033]      FIGS. 5( a ) and 5( b )  are perspective views showing examples of other valve cusp sizers. 
           [0034]      FIGS. 6( a ) to 6( c )  are cross sectional views showing examples of still other valve cusp sizers. 
           [0035]      FIG. 7  is cross sectional views showing examples of still other valve cusp size 
           [0036]      FIG. 8  is a photograph showing a conventional valve cusp sizer. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0037]    An explanation of an embodiment of the present invention will be made below with reference to the drawings. The present invention, however, is not limited to the embodiment explained below, and includes modifications appropriately modified by a person skilled in the art in a range obvious from the embodiment explained below. 
         [0038]    Note that, in the specification of the present application, “A to B” means “not less than A and not more than B”. 
         [0039]      FIG. 1  shows an exemplary valve cusp sizer  100  according to the present invention.  FIG. 1  schematically shows the valve cusp sizer  100  held by an instrument such as tweezers or a clamp. The valve cusp sizer  100  is a surgical instrument used in an aortic valvuloplasty and the like. A method for using the valve cusp sizer in the aortic valvuloplasty is disclosed in detail in Patent Document 1 and Non-Patent Literature 1. Therefore, an explanation of the aortic valvuloplasty is omitted in the specification of the present application. The disclosure of Patent Document 1 is incorporated into the specification of the present application. 
         [0040]    As shown in  FIG. 1 , the valve cusp sizer  100  has a front surface  10  to be abutted against an organism (specifically an inner wall of blood vessel of an aorta) of a patient. The front surface  10  is formed in an arcuate surface form such that a central part thereof projects toward a side of the organism of the patient. A left contact probe  11  is formed at a left end of the front surface  10 , and a right contact probe  12  is formed at a right end of the front surface  10 . The left and right contact probes  11 ,  12  are portions to be abutted against commissure portions positioned at left and right ends of a valve cusp. 
         [0041]    Specifically, for example, the valve cusp sizer  100  is inserted into the aorta after excising a valve cusp from an aortic valve composed of three valve cusps, and then the left and right contact probes  11 ,  12  of the valve cusp sizer  100  are abutted against the commissure portions of valve cusps remained at both positions adjacent to the excised valve cusp. The front surface  10  positioned between the left and right contact probes  11 ,  12  is provided to have various sizes. Namely, a plurality of types of valve cusp sizers provided for an operation is different in size of the front surface  10  positioned between the left and right contact probes  11 ,  12 . In the example shown in  FIG. 1 , the length of an arc between the left and right contact probes  11 ,  12  is about 35 mm (about plus/minus 2 mm is permissible). Thus, the valve cusp sizer  100  is labelled as “35”. Note that, an entire length of an arc forming the front surface  10  may be slightly larger than the length of the arc between the left and right contact probe portions  11 ,  12 . Although not shown in the diagrams, a plurality of sizes ranging about from 15 mm to 35 mm is provided for the size (the length of the arc) between the left and right contact probe portions  11 ,  12 . Accordingly, the size of patient&#39;s valve cusp can be measured (determined) by selecting the valve cusp sizer  100  having a suitable size, while letting the left and right contact probe portions  11 ,  12  of the valve cusp sizer  100  abut against the commissure portions of the valve cusps and changing the types of the valve cusp sizers  100 . 
         [0042]      FIG. 2  shows a front view of the valve cusp sizer  100 . As shown in  FIG. 2 , in the front surface  10  of the valve cusp sizer  100 , the height H 1  of each of left and right ends, at which the contact probe portions  11 ,  12  are formed respectively, is higher than the height H 2  of a central part in a left-right direction. This structure makes it easy to measure the size of the valve cusp with upper ends of the contact probe portions  11 ,  12  abutting against the commissure portions. 
         [0043]    Further, as shown in  FIG. 1 , a back surface  20  exists on an opposite surface side to the front surface  10 . The valve cusp sizer  100  of the present invention is provided with a pinching portion  30  protruding from the back surface  20 . Namely, the pinching portion  30  protrudes from the back surface  20  in a direction opposite to a direction in which the front surface  10  exists. As shown in  FIG. 1 , it is preferable that the pinching portion  30  is positioned on a center line of the back surface  20  in the left-right direction. 
         [0044]    The pinching portion  30  is a part to be held by an operator via a surgical instrument such as the clamp or the tweezers. Thus, the pinching portion  30  may have a width (thickness), a height, and a length that can be held by the surgical instrument. It is preferable for the pinching portion  30  that at least surfaces (left and right side surfaces) to be contacted with the surgical instrument are flat surfaces. Basically, it is preferable that the pinching portion  30  is formed in a cuboid shape as shown in  FIG. 1 , although the shape of the pinching portion  30  is not limited thereto. The pinching portion  30  may be formed in another shape, although an illustration thereof is omitted. 
         [0045]    In the example of the valve cusp sizer  100  shown in  FIG. 1 , the valve cusp sizer  100  has a certain thickness between the front surface  10  and the back surface  20 . Therefore, the valve cusp sizer  100  has an upper surface  40 , a lower surface  50 , and side surfaces  60  each connecting the front surface  10  and the back surface  20 . The valve cusp sizer  100  of the present invention, however, may have such a structure that the thickness between the front surface  10  and the back surface  20  is extremely thin and the illustrated upper surface  40 , lower surface  50 , and side surfaces  60  cannot be identified. 
         [0046]    As shown in  FIG. 1 , the back surface  20  of the valve cusp sizer  100  is formed in a shape projecting in the same direction as that of the front surface  10 . Namely, the back surface  20  is formed in a shape recessed toward a side of the front surface  10 . For example, the back surface  20  is preferably formed in an arcuate surface form similar to the front surface  10 . Further, the back surface  20  and the front surface  10  may be parallel with each other. The back surface  20  may be formed in a polygonal form without being limited to the arcuate surface form. Moreover, even if the back surface  20  is a surface non-parallel to the front surface  10 , there are no problems in particular. 
         [0047]      FIG. 3  schematically shows a plan view viewing the valve cusp sizer  100  from a side of the upper surface  40 . In  FIG. 3 , additional lines to design the valve cusp sizer  100  is shown by dotted lines. As shown in  FIG. 3 , a basic form of the valve cusp sizer  100  is a fan shape (partial column) cut at an angle confirming to the central angle for the commissure portions of the aortic valve. In the illustrated example, it is assumed that the aortic valve consists of three valve cusps and the central angles for the three commissure portions of the aortic valve are the same 120 degrees. As shown in  FIG. 3 , the front surface  10  of the valve cusp sizer  100  is an arc form. The length of an arc between the left and right contact probe portions  11 ,  12  provided on the front surface  10  of the valve cusp sizer  100  is the length conforming to the central angle for the commissure portions. That is, in the example shown in  FIG. 3 , the arc between the left and right contact probe portions  11 ,  12  has the length conforming to the central angle of 120 degrees. 
         [0048]    Note that, there is a case that the aortic valve consists of two valve cusps, although an illustration thereof is omitted. In this case, the number of the commissure portions of the aortic valve is two. If this case is assumed, the arc of the front surface  10  may be a form conforming to the central angle of 180 degrees. 
         [0049]    Further, as shown in  FIG. 3 , a center index  13 , a left index  14 , and a right index  15  are preferably formed on the upper surface  40  of the valve cusp sizer  100 . The center index  13  is formed at a center in the left-right direction. The left index  14  and the right index  15  are formed in the left contact probe portion  11  and the right contact probe portion  12  respectively on a side of the upper surface  40 . In the example shown in  FIG. 3 , the center index  13  and the left index  14  are provided at an interval conforming to 60 degrees, and the center index  13  and the right index  15  are similarly provided at the interval conforming to 60 degrees. Each of the indexes  13 ,  14 ,  15  serves as an index to be observed by an operator&#39;s sight, when the size of the cut valve cusp is measured by using the valve cusp sizer  100 . Each of the indexes  13 ,  14 ,  15  makes it easy for the operator to position the front surface  10  and the left and right contact probe portions  11 ,  12  of the valve cusp sizer  100 . 
         [0050]    In  FIG. 3 , left and right back ends of the back surface  20  formed in the arcuate surface form are indicated by characters  21 ,  22 . In this case, the pinching portion  30  protruding from the back surface  20  is preferably formed in such a length that the pinching portion  30  does not protrude beyond the left back end  21  and the right back end  22  of the back surface  20 . In  FIG. 3 , the left back end  21  and the right back end  22  of the back surface  20  are linked by a virtual line. In this case, the pinching portion  30  has such a length that the pinching portion  30  does not exceed the virtual line linking the left back end  21  and the right back end  22 . By forming the pinching portion  30  as described above, the pinching portion  30  can be placed inside a recess formed by the back surface  20 . Therefore, it is possible to prevent the pinching portion  30  from interfering an insertion of the valve cusp sizer  100  into the aorta. The length L of the pinching portion  30  is preferably at least not less than 5 mm or not less than 10 mm, while satisfying a condition that the pinching portion  30  does not protrude beyond the left and right back ends  21 ,  22  of the back surface  20 . If the length L of the pinching portion  30  is too short, it is difficult to pinch the pinching portion  30  by the clamp or tweezers. However, if the length L of the pinching portion  30  is not less than 5 mm, the pinching portion  30  can be appropriately pinched by the clamp or the like. 
         [0051]    In  FIG. 3 , the width of the pinching portion  30  is indicated by a character W. The width W of the pinching portion  30  may be determined so that the pinching portion  30  can be pinched easily by the clamp or tweezers. For example, the width W of the pinching portion  30  may be 3 mm to 20 mm, 4 mm to 15 mm, or 5 mm to 10 mm. 
         [0052]      FIG. 4  shows an outline of a cross section on a line A-A shown in  FIG. 3 . Namely,  FIG. 4  is a cross sectional view of the valve cusp sizer  100  at a part formed with the pinching portion  30 . As shown in  FIG. 4 , when comparing the height H 2  at the central portion of the front surface  10  with the height H 3  of the back surface  20 , the height H 3  of the back surface  20  is shorter than the height H 2  at the central portion of the front surface  10  (H 3 &lt;H 2 ). For example, the height H 3  of the back surface  20  is preferably about 20% to 80%, or 30% to 50% of the height H 2  at the central portion of the front surface  10 . Further, as shown in  FIG. 3 , the front surface  10  and the back surface  20  preferably stand up to be parallel surfaces each other. 
         [0053]    Since the height H 3  of the back surface  20  is shorter than the height H 2  of the front surface  10  as described above, the upper surface  40  connecting the front surface  10  and the back surface  20  is inclined. As shown in  FIG. 4 , the upper surface  40  is preferably formed to be a gradually curved surface so that the cross section thereof is a curved line. The upper surface  40 , however, may be a flat surface so that the cross section thereof is a straight line. On the other hand, the lower surface  50  connecting the front surface  10  and the back surface  20  is formed to be a flat surface so that the cross section thereof is a straight line. As the lower surface  50  is the flat surface as described above, it is easy to allow the valve cusp sizer  100  to self-stand. 
         [0054]    In the example shown in  FIG. 4 , the height H 3  of the back surface  20  is identical with the height H 4  of the pinching portion  30  (H 3 =H 4 ). The height H 4  of the pinching portion  30 , however, may be shorter or taller than the height H 3  of the back surface  20 . When considering easiness of pinching the pinching portion  30 , the height H 4  of the pinching portion  30  is preferably taller than the height H 3  of the back surface  20  (H 4 &gt;H 3 ). 
         [0055]    Subsequently, referring to  FIGS. 5 and 6 , examples of improved valve cusp sizer  100  will be explained. 
         [0056]      FIG. 5  shows examples of pinching portion  30  of the valve cusp sizer  100  to which non-slip improvement is applied. In the example shown in  FIG. 5( a ) , a slip stopper  71  is attached to the pinching portion  30 . For example, the slip stopper  71  is preferably formed of material having high coefficient of friction such as silicone rubber. Namely, the material forming the slip stopper  71  has preferably higher coefficient of friction than that of material forming a body portion of the valve cusp sizer  100 . Publicly known materials can be adopted appropriately as material of the slip stopper. In the example shown in  FIG. 5( a ) , the slip stopper  71  is a cap form having an opening and covers the entirety of the pinching portion  30 . However, since the pinching portion  30  is held by pinching the left and right side surfaces  31 ,  32  thereof, the slip stopper  71  may be positioned at least at the left and right side surfaces  31 ,  32 . For example, the slip stopper  71  can be attached only to the left and right side surfaces  31 ,  32 . The slip stopper  71  can be integrally formed with the pinching portion  30 . 
         [0057]    In the example shown in  FIG. 5( b ) , a nonslip treatment  72  is applied to the left and right side surfaces  31 ,  32  of the pinching portion  30 . An example of a nonslip treatment  72  may include making the side surfaces  31 ,  32  of the pinching portion  30  rough surfaces so that the coefficient of friction thereof is enhanced, or forming notches (concave and convex) on the side surfaces  31 ,  32  of the pinching portion  30  so that tips of the clamp or the tweezers easily fit therein. 
         [0058]    The slip stopper  71  or the nonslip treatment  72  shown in  FIGS. 5( a ) and 5( b )  respectively prevents the clamp or the tweezers from slipping when pinching the pinching portion  30 , and thereby enhancing safety in the operation in which the valve cusp sizer  100  according to the present invention is used. 
         [0059]      FIG. 6  shows examples of pinching portion  30  of the valve cusp sizer  100  which are improved to be held easily. In the example shown in  FIG. 6( a ) , the pinching portion  30  is inclined at a predetermined angle θ to the back surface  20  (including a case of standing perpendicular to a placement surface) to stand upwardly. For example, the angle θ may be 0° to 80°, 20° to 60°, or 30° to 45°. In the example shown in  FIG. 6( a ) , the valve cusp sizer  100  has such a structure that the pinching portion  30  rises to a flat surface in a state of the valve cusp sizer  100  being placed on the flat surface. The pinching portion  30  inclined in this manner makes it easy to hold the valve cusp sizer  100  from upside by the clamp or the tweezers. Further, the pinching portion  30  partly inclined upwardly makes it possible to hold the pinching portion  30  so that a grip member of the surgical instrument such as Kelly clamp is parallel to an inclined part of the pinching portion  30  depending on an inclination angle thereof. As a result, the valve cusp sizer can be abutted against the commissure portions at an appropriate angle, thereby reducing a measurement error. 
         [0060]      FIG. 6( b )  shows an example in which the pinching portion  30  is composed of a non-inclined part  35  and an inclined part  36 . The non-inclined part  35  is a part extended from the back surface  20 , and the inclined part  36  is a part extended from the non-inclined part  35 . The non-inclined part  35  of the pinching portion  30  extends without being inclined to the back surface  20 . The inclined part  36  of the pinching portion  30  is inclined at a predetermined angle θ to the back surface  20  (including a case of standing perpendicular to a placement surface) to stand upwardly. For example, the angle θ of the inclined part  36  may be 0° to 80°, 20° to 60°, or 30° to 45°. Since the pinching portion  30  is partly formed by the non-inclined part  35  in this manner, the valve cusp sizer  100  can self-stand stably. Further, since the pinching portion  30  is partly formed by the inclined part  36 , it is easy to hold the valve cusp sizer  100  from upside by using the clamp or the tweezers. 
         [0061]      FIG. 6( c )  shows another example in which an upper surface  33  of the pinching portion  30  is inclined. In the example shown in  FIG. 6( c ) , the upper surface  33  of the pinching portion  30  is an inclined surface so that the height H 4  of a back end of the pinching portion  30  is taller than the height H 3  of the back surface  20 . For example, the height H 4  (maximum height) of the pinching portion  30  may be 110% to 200% of the height H 3  of the back surface  20 . Further, an inclination angle θ of the upper surface  33  of the pinching portion  30  to back surface  20  may be 0° to 80°, 20° to 60°, or 30° to 45°. On the other hand, a lower surface  34  of the pinching portion  30  extends at right angles to the back surface  20 . Accordingly, in a state that the valve cusp sizer  100  is placed on a flat surface, the pinching portion  30  is not away from the flat surface. This structure of the pinching portion  30  improves the easiness of pinching the valve cusp sizer  100 , and ensures the stable self-standing of the valve cusp sizer  100 . 
         [0062]      FIG. 7  shows another example of pinching portion  30  of the valve cusp sizer  100  which are improved to be held easily. In the example shown in  FIG. 7 , the back surface  37  of the pinching portion  30  is inclined at a predetermined angle θ to the back surface  20  of the valve cusp sizer  100 . For example, the angle θ of the back surface  37  of the pinching portion  30  to the back surface  20  may be 10° to 80°, 20° to 60°, or 30° to 45°. The part of pinching portion  30  (the back surface  37 ) inclined upwardly makes it possible to hold the valve cusp sizer  100  from upside by the clamp or the tweezers so that a grip member of the surgical instrument such as Kelly clamp is parallel to an inclined part of the pinching portion  30  depending on an inclination angle thereof. 
         [0063]    In the above specification of the present application, explanation about the embodiments of the present invention has been made while referring to the diagrams to describe the contents of the present invention. The present invention, however, is not limited to the above embodiments, and includes modified or improved embodiments which are obvious for a person skilled in the art based on the described matters in the specification of the present application. 
       INDUSTORIAL APPLICABILITY 
       [0064]    The present invention relates to a valve cusp sizer for measuring the size of a valve cusp composing a cardiac valve. The present invention can be applied suitably to a field of medical instruments. 
       REFERENCE SIGNS LIST 
       [0065]      10 : front surface,  11 : left contact probe portion,  12 : right contact probe portion,  13 : center index,  14 : left index,  15 : right index,  20 : back surface,  21 : left back end,  22 : right back end,  30 : pinching portion,  31 : left side surface,  32 : right side surface,  33 : upper surface,  34 : lower surface,  35 : non-inclined part,  36 : inclined part,  37 : back surface,  40 : upper surface,  50 : lower surface,  60 : side surface,  71 : slip stopper,  72 : nonslip treatment,  100 : valve cusp sizer