Patent Description:
Conventionally, an auxiliary tool called a sheath introducer is used when a catheter is inserted into a body lumen such as a patient's blood vessel. A sheath introducer includes a sheath for connecting a patient's body lumen to the outside of the body, and a dilator to be inserted into the sheath for expanding a hole formed on a body surface. For example, <CIT> describes a sheath introducer <NUM> including a sheath <NUM> and a dilator <NUM> (see <FIG> and others).

The above sheath introducer <NUM> is used as follows: the patient's skin is first perforated at a predetermined location using an introducer needle, a guide wire is inserted into a body lumen such as a blood vessel through the resulting hole, a base end of the guide wire is inserted into a front end of the sheath introducer <NUM> where the dilator <NUM> is already inserted into the sheath <NUM>, and the sheath introducer <NUM> is then inserted into the body lumen along the guide wire. During this, a front end of the dilator <NUM> will expand the diameter of the hole formed on the skin. Subsequently, the dilator <NUM> is withdrawn from the sheath introducer <NUM>, and then a catheter is inserted into the sheath introducer <NUM> and is inserted into a body lumen such as a blood vessel.

Such a sheath introducer is usually designed to be inserted through the patient's skin, and generally short and linear as described in <CIT>. Meanwhile, an alternative procedure is performed as follows: an introducer needle is pushed out of a front end of an endoscope inserted through the patient's mouth or nose instead of through the patient's skin to perforate the wall of a digestive tract such as a patient's stomach at a predetermined location, and a guide wire is inserted through the resulting hole, and a front end of a dilator is inserted into a base end of the guide wire, and the dilator is then inserted into the wall of the digestive tract along the guide wire to increase the diameter of the hole formed on the wall of the digestive tract.

<CIT> discloses a dilator comprising a hollow shaft having an outer diameter of a front end smaller than that of a base end; and spirally-arranged projections projecting outwardly provided on an outer peripheral surface of the shaft.

<CIT> discloses a dilator comprising a hollow shaft having an outer diameter of a front end smaller than that of a base end; and a spiral ridge integrally formed on an outer peripheral surface of the shaft.

<CIT> discloses a dilator comprising a hollow shaft having an outer diameter of a front end smaller than that of a base end; and a thread integrally formed on an outer peripheral surface of the shaft.

A dilator for use in such a procedure is designed to be inserted through the patient's mouth or nose, and thus needs to be relatively long and generally configured so as to be used in a curved state, considering that it is to be passed through the digestive tract.

However, an increased length of a dilator may have a problem in that a rotational force (torque) and pushing force (pushability) from the user's hand cannot be transmitted to a front end of the dilator, which in turn may preclude increasing the diameter of a hole formed on the wall of a digestive tract. In particular, a curved dilator further had a problem in that the deterioration of these properties becomes more significant.

The present invention is made in view of these circumstances. An object of the present invention is to provide a dilator capable of easily increasing the diameter of a hole formed on the wall of a digestive tract and the like and also capable of maintaining pushability and torquability even when a shaft is longer and curved.

The technical object is solved by the subject-matter of any of claims <NUM>, <NUM> and <NUM>. Preferred embodiments of the present invention are the subject-matter of dependent claims.

The present invention can provide a dilator capable of ensuring front-end flexibility and maintaining pushability and torquability even when the shaft is longer and curved, and capable of easily increasing the diameter of a hole formed on a wall of a digestive tract and the like.

Below, the embodiments of the present invention will be described with reference to the figures. It is noted that the dimensions of the dilators shown in the figures are merely provided to facilitate understanding of the embodiments, and do not necessarily correspond to the actual dimensions.

The first embodiments of the present invention will be described with reference to the figures.

<FIG> shows an overall view of a dilator according to a first embodiment of the present invention, and <FIG> shows a front end portion with a view of an inner cavity of the dilator (a multilayer body) according to the first embodiment, and <FIG> shows a cross-sectional view at III-III in <FIG>.

In <FIG>, the left side in the figure corresponds to the front end side (the distal side) which is to be inserted into the body, and the right side corresponds to the base end side (the hand side, the proximal side) which is to be operated by an operator such as a surgeon.

In <FIG>, a dilator <NUM> includes: a multilayer body <NUM> including a hollow coil body <NUM> including a plurality of metal wires 3a, 3b, 3c, 3d, 3e, 3f, <NUM>, <NUM>, 3j, and <NUM> wound around into a hollow shape and a coil body <NUM> including a single metal wire 5a wound around a surface of the hollow coil body <NUM> in a direction (clockwise, facing to the front end) opposite to the hollow coil body <NUM> (counterclockwise, facing to the front end); and a connector <NUM> having a hollow shape connected to a base end of the multilayer body <NUM>.

Here, the multilayer body <NUM> has a cylindrical hollow shape at a base end portion P3, has a tapered hollow shape at an intermediate portion P2, and has a cylindrical hollow shape at a front end portion P1.

It is noted that the metal element wires 3a, 3b, 3c, 3d, 3e, 3f, <NUM>, <NUM>, 3j, and <NUM> correspond to the "first wires," and the hollow coil body <NUM> corresponds to the "first layer body," the "shaft," and the "first coil.

In addition, the metal wire 5a corresponds to the "second wire," and the coil body <NUM> corresponds to the "second layer body," the "spirally-arranged protruding portion," and the "second coil.

Further, the intermediate portion P2 of the hollow coil body <NUM> corresponds to the "tapered hollow portion" and the "portion having an increasing outer diameter (tapered shape). " Further, the connector <NUM> corresponds to the "grip portion.

The hollow coil body <NUM> is formed such that the metal wires 3a, 3b, 3c, 3d, 3e, 3f, <NUM>, <NUM>, 3j, and <NUM> of <NUM> stainless steel wires are wound around into a hollow shape as shown in <FIG>. The hollow coil body <NUM> has a cylindrical hollow shape at the base end portion P3, has a tapered hollow shape at the intermediate portion P2, has a cylindrical hollow shape at the front end portion P1, and has an outer diameter decreasing toward a front end. That is, the hollow coil body <NUM> has a hollow shape having an outer diameter of a front end smaller than that of a base end.

In <FIG>, the dotted lines represent the common inscribed lines of the hollow coil body <NUM>. An inner cavity <NUM> is formed in the inner side of the common inscribed lines of the hollow coil body <NUM> (see <FIG>).

It is noted that, while metal wires made of stainless steel are used as the wires of the hollow coil body <NUM> in the present embodiment, they are not limited to stainless steel wires. They may be wires made of a superelastic alloy such as nickel-titanium. Further, they are not limited to metal wires and may be resin wires.

The coil body <NUM> is configured such that a metal element wire 5a of a single stainless steel wire is wound around in a direction (right-hand side, facing to the front end) opposite to the hollow coil body <NUM> (counterclockwise, facing to the front end). Here, the metal wire 5a is wound around closely at the base end side and is wound around with gaps between adjacent winding at the intermediate portion P2 and the front end portion P1. The coil body <NUM> provides a spirally-arranged protruding portion protruding outwardly (the outermost surface of the dilator <NUM>, the outermost portion) on an outer peripheral surface <NUM> of the hollow coil body <NUM>. The spirally-arranged protruding portion has gaps between adjacent portions (adjacent portions of a metal wire) along an axis A of the hollow coil body <NUM>. Further, the coil body <NUM> is provided at the intermediate portion P2 which corresponds to a portion having an increasing outer diameter of the hollow coil body <NUM>.

Further, for the metal wire 5a used in the present embodiment, the amount of gap between adjacent windings of the metal wire is gradually decreased at a cylindrical hollow portion of the base end portion P3 toward the base end side thereof. This configuration enables the stiffness of the dilator <NUM> (the multilayer body <NUM>) along the axis direction to be gradually changed so that the dilator <NUM> (multilayer body <NUM>) can easily enter into the inside even when an approach pathway meanders.

It is noted that the metal wire 5a is formed such that the amount of gap between adjacent windings of the metal wire is gradually decreased at the cylindrical hollow portion of the base end portion P3 toward the base end side thereof, but the configuration shall not be limited to this. Even when the amount of gap between adjacent windings of the metal wire is constant from the front end portion P1 toward the base end portion P3, the front-end flexibility of the dilator <NUM> (multilayer body <NUM>) can be ensured, and the pushability and torquability of the dilator <NUM> (multilayer body <NUM>) can be maintained in a case where the dilator <NUM> (multilayer body <NUM>) is longer and curved. Further, the screw effect of the single metal wire 5a enables the dilator <NUM> to be advanced not only by a pushing operation but also by a rotational operation. Further, the diameter of a pre-formed hole can easily be increased by the coil body <NUM> provided at a portion where the hollow coil body <NUM> has an increasing outer diameter, i.e., at the intermediate portion P2.

Further, with regard to the metal wire 5a, the amount of gap between adjacent windings of the metal wire is gradually decreased at the cylindrical hollow portion of the base end portion P3 toward the base end side thereof. This configuration can have the following effect: the stiffness of the dilator <NUM> (the multilayer body <NUM>) in the axis direction can be gradually changed so that the dilator <NUM> (multilayer body <NUM>) can easily enter into the inside even when an approach pathway meanders.

Further, a shaft composed of the hollow coil body <NUM> (the first coil) including a plurality of metal wires wound around into a hollow shape can improve the flexibility of the shaft and the transmissibility of torque via the shaft. Further, a spirally-arranged protruding portion composed of the coil body <NUM> (the second coil) including the single metal wire 5a wound around on the outer peripheral surface <NUM> of the hollow coil body <NUM> can easily be formed, can ensure the flexibility of the front end of the dilator <NUM> and can improve the torquability by virtue of the elasticity of the second coil. Further, each wire of the hollow coil body <NUM> and the coil body <NUM> is wound around in a direction opposite to each other. Therefore, even when the dilator <NUM> is rotated in a direction to open the hollow coil body <NUM>, a force is applied in a direction to close the coil body <NUM> to prevent the opening of the hollow coil body <NUM>. This allows a force applied to the connector <NUM> of the dilator <NUM> to be transmitted to the front end side.

It is noted that the metal wire 5a is made of stainless steel in the present embodiment, but the material shall not be limited to stainless steel. A metal wire made of a superelastic alloy such as nickel-titanium may be used. Further, it shall not be limited to a metal wire, and a resin wire may be used.

In the present embodiment and other embodiments described hereinafter, the length of a dilator is, for example, <NUM>, preferably <NUM> to <NUM>, the length of the front end portion P1 is, for example, <NUM>, preferably <NUM> to <NUM>, and the length of the intermediate portion P2 is, for example, <NUM>, preferably <NUM> to <NUM>. The inner diameter of the hollow coil body <NUM> at the front end is, for example, <NUM>, preferably <NUM> to <NUM>, and the inner diameter of the hollow coil body <NUM> at the base end is, for example, <NUM>, preferably <NUM> to <NUM>. The outer diameter of the coil body <NUM> at the front end is, for example, <NUM>, preferably <NUM> to <NUM>, and the outer diameter of the coil body <NUM> at the base end is, for example, <NUM>, preferably <NUM> to <NUM>. Further, the diameters of the metal wires 3a to <NUM> and 3j to <NUM> are, for example, <NUM>, preferably <NUM> to <NUM>, and the diameter of the metal wire 5a is, for example, <NUM>, preferably <NUM> to <NUM>.

The front end of the connector <NUM> is connected to the base end of the hollow coil body <NUM> and the base end of the coil body <NUM>. The connector <NUM> is made of a resin and has a hollow shape which has an inner cavity communicating with the inner cavity <NUM> of the hollow coil body <NUM>.

Next, an example of an operating mode of the above dilator will be described.

First, a target object is punctured using an introducer needle. After the puncture, a guide wire is inserted through an inner cavity of the introducer needle, and the introducer needle is withdrawn thereafter. Then, the front end of the dilator <NUM> according to the present embodiment is inserted from the base end of the guide wire into the punctured portion. Subsequently, the diameter of a hole at the punctured portion can be increased by pushing and rotating the dilator <NUM> inward.

<FIG> shows a front end portion of a dilator (a multilayer body) according to a second embodiment. In <FIG>, the left side in the figure corresponds to the front end side (the distal side) which is to be inserted into the body, and the right side corresponds to the base end side (the hand side, the proximal side) which is to be operated by an operator such as a surgeon.

It is noted that the dilator (the multilayer body) according to the present embodiment basically has the same structure as the dilator <NUM> (the multilayer body <NUM>) according to the first embodiment. Therefore, the same number is given to the same member, and a detailed description will be omitted.

In <FIG>, a dilator <NUM> includes: a multilayer body <NUM> including the hollow coil body <NUM> including the plurality of wires 3a, 3b, 3c, 3d, 3e, 3f, <NUM>, <NUM>, 3j, and <NUM> wound around into a hollow shape, the coil body <NUM> including the single metal wire 5a wound around the surface of the hollow coil body <NUM> in a direction (clockwise, facing to the front end) opposite to the hollow coil body <NUM> (counterclockwise, facing to the front end); and a connector <NUM> having a hollow shape and being connected to the base end of the multilayer body <NUM>. However, the dilator <NUM> differs from the dilator <NUM> in that the multilayer body <NUM> of the dilator <NUM> has a forefront portion <NUM> at the front end of the hollow coil body <NUM> while the multilayer body <NUM> of the dilator <NUM> does not have the forefront portion <NUM> at the front end of the hollow coil body <NUM>. According to the present embodiment, the hollow coil body <NUM> having the forefront portion <NUM> provided at the front end corresponds to the "shaft.

The forefront portion <NUM> is formed by casting a solder material (a silver-tin solder material, a gold-tin solder material, and the like) into the front end of the hollow coil body <NUM> and has a substantially cylindrical hollow shape. Further, the surface of forefront portion <NUM> is flat while the surface of the front end of the multilayer body <NUM> is an uneven.

The dilator <NUM> having the aforementioned configuration in which the forefront portion <NUM> having a flat surface is connected to the front end of the multilayer body <NUM> can further improve insertability into a punctured portion by first pressing the dilator against the punctured portion, and then pushing and rotating the dilator thereinto.

<FIG> shows a front end portion of a dilator (a multilayer body) according to a third embodiment, <FIG> shows a front end portion with a view of an inner cavity of the dilator (the multilayer body) according to the third embodiment, and <FIG> shows a cross-sectional view at VII-VII in <FIG>.

In <FIG>, a dilator <NUM> includes: a multilayer body <NUM> including a hollow coil body <NUM> including a plurality of metal wires 21a, 21b, 21c, 21d, 21e, 21f, <NUM>, <NUM>, 21j, and <NUM> wound around into a hollow shape, a hollow coil body <NUM> including a plurality of metal wires 22a, 22b, 22c, 22d, 22e, 22f, <NUM>, <NUM>, 22j, <NUM>, <NUM>, 22n, 22p, 22q, 22r, and <NUM> wound around with gaps between adjacent winding on an outer periphery of the hollow coil body <NUM> at a position apart from a front end toward the base end of the hollow coil body <NUM> in the same direction (counterclockwise, facing to the front end) as the hollow coil body <NUM>, a coil body <NUM> including a plurality of metal wires 23a (only one of the metal element wires 23a is indicated by a reference number in <FIG>) wound around with gaps between adjacent winding an outer periphery of the coil body <NUM> at a position apart from a front end toward the base end of the coil body <NUM> in a direction (clockwise, facing to the front end) opposite to the coil <NUM> (counterclockwise, facing to the front end), a coil body <NUM> including a single element wire 25a wound around with gaps between adjacent winding on the outer periphery of the coil body <NUM> at the front end side of a front end of the coil body <NUM>, and a coil body <NUM> including a single element wire 24a wound around with gaps between adjacent winding on the outer periphery of the coil body <NUM> at the front end side of the front end of the coil body <NUM> in the same direction as the metal wire 25a; and a connector <NUM> having a hollow shape and connected to a base end of the multilayer body <NUM>.

Here, the multilayer body <NUM> has a cylindrical hollow shape at the base end side of the base end portion P3 as in the multilayer body <NUM> and the multilayer body <NUM>. However, the multilayer body <NUM> has a stepped and cylindrical hollow shape in the vicinity of the front end portion while the multilayer body <NUM> and the multilayer body <NUM> have front-end tapered shapes.

It is noted that the metal wires 21a, 21b, 21c, 21d, 21e, 21f, <NUM>, <NUM>, 21j, and <NUM> correspond to the "first wires," and the hollow coil body <NUM> corresponds to the "first layer body.

Further, the metal wires 22a, 22b, 22c, 22d, 22e, 22f, <NUM>, <NUM>, 22j, <NUM>, <NUM>, 22n, 22p, 22q, 22r, and <NUM> corresponds to the "second wires," and the coil body <NUM> corresponds to the "second layer body" and the "portion having an increasing outer diameter.

Further, the metal wire 24a corresponds to the "third wire," and the coil body <NUM> corresponds to the "third layer body.

Further, the metal wires 23a correspond to the "fourth wires," and the coil body <NUM> corresponds to the "fourth layer body. " The hollow coil body <NUM> and the coil body <NUM> correspond to the "shaft" and the "first coil.

Further, the metal wire 25a corresponds to the "fifth wire," and the hollow coil body <NUM> corresponds to the "fifth layer body. " The hollow coil body <NUM> and the hollow coil body <NUM> correspond to the "spirally-arranged protruding portion" and the "second coil.

The hollow coil body <NUM> is formed such that the metal wires 21a, 21b, 21c, 21d, 21e, 21f, <NUM>, <NUM>, 21j, and <NUM> of <NUM> stainless steel wires are twisted into a hollow shape as shown in <FIG>. The hollow coil body <NUM> has a cylindrical hollow shape from the front end to the connector <NUM>.

In <FIG>, the dotted line (the innermost among the three dotted lines) represents the common inscribed line of the hollow coil body <NUM>. An inner cavity <NUM> is formed in the inner side of the common inscribed line of the hollow coil body <NUM> (see <FIG>).

Further, the coil body <NUM> is formed such that the metal wires 22a, 22b, 22c, 22d, 22e, 22f, <NUM>, <NUM>, 22j, <NUM>, <NUM>, 22n, 22p, 22q, 22r, and <NUM> of <NUM> stainless steel wires are twisted on a surface of the coil body <NUM> as shown in <FIG>. The coil body <NUM> also has a cylindrical hollow shape from the front end to the connector <NUM>.

In <FIG>, the dotted line (the intermediate among the three dotted lines) represents the common inscribed line of the coil body <NUM>.

Further, the coil body <NUM> is formed such that the metal wires 23a of <NUM> stainless steel wires are twisted on a surface of the coil body <NUM>. The coil body <NUM> also has a cylindrical hollow shape from the front end to the connector <NUM>.

In <FIG>, the dotted line (the outermost among the three dotted lines) represents the common inscribed line of the hollow coil body <NUM>. The coil body <NUM> is twistedly formed on the surface of the hollow coil body <NUM>. This means that the hollow coil body <NUM> and the coil body <NUM> which correspond to the shaft have a hollow shape having an outer diameter of a front end smaller than that of a base end.

Further, the coil body <NUM> is formed such that the metal wire 24a of a single stainless steel wire is formed on the surface of the coil body <NUM>, and the coil body <NUM> is formed such that the metal wire 25a of a single stainless steel wire is formed on the surface of the coil body <NUM>.

According to the present embodiment, each element wire in the hollow coil body <NUM>, the coil body <NUM>, and the coil body <NUM> is wound around closely, and in the coil body <NUM> and the coil body <NUM>, a wire is wound around with gaps between adjacent winding (see <FIG>). The coil body <NUM> provides a spirally-arranged protruding portion protruding outwardly (the outermost surface of the dilator <NUM>, the outermost portion) on an outer peripheral surface <NUM> of the hollow coil body <NUM>, and the coil body <NUM> provides a spirally-arranged protruding portion protruding outwardly (the outermost surface of the dilator <NUM>, the outermost portion) on an outer peripheral surface 22T of the coil body <NUM>. The spirally-arranged protruding portion has gaps between adjacent portions (adjacent portions of a metal wire) along an axis A of the hollow coil body <NUM>. Further, the coil body <NUM> is provided on the coil body <NUM> as a portion in which the shaft has an increasing outer diameter.

It is noted that metal wires made of stainless steel are used for the wires of the hollow coil body <NUM>, the coil body <NUM>, the coil body <NUM>, the coil body <NUM>, and the coil body <NUM> in the present embodiment, but they are not limited to stainless steel wires. They may be those made of a superelastic alloy such as nickel-titanium. Further, they are not limited to metal wires and may be resin wires.

The dilator <NUM> (the multilayer body <NUM>) according to the present embodiment can ensure the front-end flexibility of the dilator <NUM> (the multilayer body <NUM>) and can maintain the pushability and torquability of the dilator <NUM> (the multilayer body <NUM>) even when the dilator <NUM> (the multilayer body <NUM>) is longer and curved. Further, the screw effect of the single metal wire 24a and the single metal wire 25a enables the dilator <NUM> to be advanced not only by a pushing operation but also by a rotational operation. Further, the diameter of a pre-formed hole can easily be increased by the coil body <NUM> provided at the coil body <NUM> which corresponds to a portion where the shaft has an increasing outer diameter.

It is noted that when the amounts of gap between adjacent windings of the metal wire 25a and the metal wire 24a are formed so as to be gradually reduced toward the base end side in the present embodiment, the following effect can be observed: the stiffness of the dilator <NUM> (the multilayer body <NUM>) along the axis direction can be gradually changed so that the dilator <NUM> (the multilayer body <NUM>) can easily enter into the inside even when an approach pathway meanders.

Further, the shaft composed of the hollow coil body <NUM> and the coil body <NUM> (the first coil) each including a plurality of metal wires wound around into a hollow shape can improve the flexibility of the shaft and the transmissibility of torque via the shaft. Further, the spirally-arranged protruding portion composed of the coil body <NUM> (the second coil) including a single wire wound around on the outer peripheral surface <NUM> of the hollow coil body <NUM> and the coil body <NUM> (the second coil) wound around on the outer peripheral surface 22T of the coil body <NUM> can be easily formed, can ensure the flexibility of the front end of the dilator <NUM> by virtue of the elasticity of the second coil, and can improve the torquability. Further, each wire of the hollow coil body <NUM> and the coil body <NUM>, and each element wire of the coil body <NUM> and the coil body <NUM> are wound around in directions opposite to each other. Therefore, even when the dilator <NUM> is rotated in a direction to open the hollow coil body <NUM> and the coil body <NUM>, a force is applied in a direction to close the coil body <NUM> and the coil body <NUM> to prevent the opening of the hollow coil body <NUM> and the coil body <NUM>. This allows a force applied to the connector <NUM> of the dilator <NUM> to be transmitted to the front end side.

<FIG> shows a front end portion of a dilator (a multilayer body) according to a fourth embodiment. In <FIG>, the left side in the figure corresponds to the front end side (the distal side) which is to be inserted into the body, and the right side corresponds to the base end side (the hand side, the proximal side) which is to be operated by an operator such as a surgeon.

In <FIG>, a dilator <NUM> includes: a multilayer body <NUM> including a hollow coil body <NUM> including a plurality of metal wires 31a, 31b, 31c, 31d, 31e, 31f, <NUM>, <NUM>, 31j, and <NUM> wound around into a hollow shape, a coil body <NUM> including a single metal wire 32a wound around on an outer periphery of the hollow coil body <NUM> from a front end of the hollow coil body <NUM> in a direction (clockwise, facing to the front end) opposite to the hollow coil body <NUM>, a coil body <NUM> including a plurality of metal wires 33a (only one of the metal wires 33a is indicated by the reference number in <FIG>) wound around with gaps between adjacent winding on an outer periphery of the coil body <NUM> at a position apart from a front end toward the base end of the coil body <NUM> in a direction (counterclockwise, facing to the front end) opposite to the coil <NUM> (clockwise, facing to the front end), and a coil body <NUM> including a single metal wire 35a wound around with gaps between adjacent winding on the outer periphery of the coil body <NUM> at the front end side of a front end of the coil body <NUM> in the same direction (clockwise, facing to the front end) as the coil body <NUM> (clockwise, facing to the front end); and a connector <NUM> having a hollow shape and being connected to a base end of the multilayer body <NUM>.

Here, the multilayer body <NUM> has a stepped and cylindrical hollow shape as in the multilayer body <NUM> according to the third embodiment, but it differs from the multilayer body <NUM> in that the coil body <NUM> in the multilayer body <NUM> according to the present embodiment is formed integrally and continuously while the coil body <NUM> and the coil body <NUM> in the multilayer body <NUM> according to the third embodiment are formed as separate members. That is, in the coil body <NUM>, the metal wire 32a is wound around closely at the base end side while wound around with gaps between adjacent winding at the front end side as shown in <FIG>.

It is noted that the hollow coil body <NUM> and a portion of the coil body <NUM> where the wire is wound around closely correspond to the "shaft" and the "first coil. " A portion of the coil body <NUM> where the wire is wound around with gaps between adjacent winding and the coil body <NUM> correspond to the "spirally-arranged protruding portion" and the "second coil. " Further, the portion of the coil body <NUM> where the wire is wound around closely corresponds to the "portion having an increasing outer diameter.

The hollow coil body <NUM> is formed such that the metal wires 31a, 31b, 31c, 31d, 31e, 31f, <NUM>, <NUM>, 31j, and <NUM> of <NUM> stainless steel wires are twisted into a hollow shape as in the hollow coil body <NUM>. The hollow coil body <NUM> has a cylindrical hollow shape from the front end to the connector <NUM>.

Further, the coil body <NUM> is formed such that the metal wire 32a of a single stainless steel wire is wound around a surface of the coil body <NUM>. The coil body <NUM> also has a cylindrical hollow shape from the front end to the connector <NUM>.

Further, the coil body <NUM> is formed such that the metal wires 33a of <NUM> stainless steel wires are twisted on a surface of the coil body <NUM>. The hollow coil body <NUM> also has a cylindrical hollow shape from the front end to the connector <NUM>. A closely wound around portion of the coil body <NUM> is twistedly formed on the surface of the hollow coil body <NUM>. This means that the hollow coil body <NUM> and the closely wound around portion of the coil body <NUM> which correspond to the shaft have a hollow shape having an outer diameter of a front end smaller than that of a base end.

Further, the coil body <NUM> is formed such that the metal wire 35a of a single stainless steel wire is formed on the surface of the coil body <NUM>.

According to the present embodiment, each wire in the hollow coil body <NUM> and the coil body <NUM> is wound around closely (see <FIG>). The portion of the coil body <NUM> where the wire is wound around with gaps between adjacent winding provides a spirally-arranged protruding portion protruding outwardly (the outermost surface of the dilator <NUM>, the outermost portion) on an outer peripheral surface <NUM> of the hollow coil body <NUM>, and the coil body <NUM> provides a spirally-arranged protruding portion protruding outwardly (the outermost surface of the dilator <NUM>, the outermost portion) on an outer peripheral surface 32B of the closely wound around portion of the coil body <NUM>. These spirally-arranged protruding portions each have gaps between adjacent portions (adjacent portions of a metal wire) along an axis A of the hollow coil body <NUM>. Further, the coil body <NUM> is provided at the closely wound around portion of the coil body <NUM> which corresponds to a portion where the shaft has an increasing outer diameter.

It is noted that metal wires made of stainless steel are used for the wires of the hollow coil body <NUM>, the coil body <NUM>, the coil body <NUM>, and the coil body <NUM> in the present embodiment, but they are not limited to stainless steel wires. They may be those made of a superelastic alloy such as nickel-titanium. Further, they are not limited to metal wires and may be resin wires.

The dilator <NUM> (the multilayer body <NUM>) according to the present embodiment can ensure the front-end flexibility of the dilator <NUM> (the multilayer body <NUM>) and can maintain the pushability and torquability of the dilator <NUM> (the multilayer body <NUM>) even when the dilator <NUM> (the multilayer body <NUM>) is longer and curved. Further, the screw effect of the single metal wire 32a and the single metal wire 35a extending contiguously toward the front end from the base end of the coil body <NUM> can further be improved when the multilayer body <NUM> is rotated. This enables the dilator <NUM> to be easily advanced not only by a pushing operation but also by a rotational operation. In addition, the coil body <NUM> is provided in the closely wound around portion of the coil body <NUM> which corresponds to a portion where the shaft has an increasing outer diameter. Therefore, the diameter of a pre-formed hole can be increased more easily.

It is noted that when the amounts of gap between adjacent windings of the metal wire 32a and the metal wire 35a are formed so as to be gradually reduced toward the base end side in the present embodiment, the following effect can be observed: the stiffness of the dilator <NUM> (the multilayer body <NUM>) along the axis direction can be gradually changed so that the dilator <NUM> (the multilayer body <NUM>) can easily enter into the inside even when an approach pathway meanders.

Further, a shaft composed of the hollow coil body <NUM> including a plurality of metal wires wound around into a hollow shape, and the coil body <NUM> (the first coil) can improve the flexibility of the shaft and the transmissibility of torque via the shaft. Further, a spirally-arranged protruding portion composed of the coil body <NUM> (the second coil) including a single metal wire wound around the outer peripheral surface <NUM> of the hollow coil body <NUM> and the coil body <NUM> (the second coil) wound around the outer peripheral surface 32B of the coil body <NUM> can be easily formed, can ensure the flexibility of the front end of the dilator <NUM> by virtue of the elasticity of the second coil, and can improve the torquability. Further, each wire of the hollow coil body <NUM>, and each wire of the coil body <NUM> and the coil body <NUM> are wound around in directions opposite to each other. Therefore, even when the dilator <NUM> is rotated in a direction to open the hollow coil body <NUM>, a force is applied in a direction to close the coil body <NUM> and the coil body <NUM> to prevent the opening of the hollow coil body <NUM>. This allows a force applied to the connector <NUM> of the dilator <NUM> to be transmitted to the front end side.

<FIG> shows a front end portion of a dilator (a multilayer body) according to a fifth embodiment.

In <FIG>, a dilator <NUM> includes: a multilayer body <NUM> including a hollow coil body <NUM> including a plurality of metal wires 41a, 41b, 41c, 41d, 41e, 41f, <NUM>, <NUM>, 41j, and <NUM> wound around into a hollow shape, a hollow coil body <NUM> including a plurality of metal wires 42a, 42b, 42c, 42d, 42e, 42f, <NUM>, <NUM>, 42j, <NUM>, <NUM>, 42n, 42p, 42q, 42r, and <NUM> wound around with gaps between adjacent winding on an outer periphery of the hollow coil body <NUM> at a position apart from a front end toward the base end of the hollow coil body <NUM> in the same direction (counterclockwise, facing to the front end) as the hollow coil body <NUM> (counterclockwise, facing to the front end), a coil body <NUM> including a single metal wire 43a wound around on an outer periphery of the hollow coil body <NUM> from a front end of the hollow coil body <NUM> in a direction (clockwise, facing to the front end) opposite to the hollow coil body <NUM>, and a coil body <NUM> including a single metal wire 44a wound around with gaps between adjacent winding on the outer periphery of the coil body <NUM> at the front end side of the front end of the coil body <NUM> in the same direction (clockwise, facing to the front end) as the coil body <NUM> (clockwise, facing to the front end); and a connector <NUM> having a hollow shape and connected to a base end of the multilayer body <NUM>.

Here, the multilayer body <NUM> has a stepped and cylindrical hollow shape as in the multilayer body <NUM> according to the third embodiment, but it differs from the multilayer body <NUM> in that the coil body <NUM> in the multilayer body <NUM> according to the present embodiment is formed integrally and continuously while the coil body <NUM> and the coil body <NUM> in the multilayer body <NUM> according to the third embodiment are formed as separate members. That is, in the coil body <NUM>, the metal wire 43a is wound around closely at the base end side while wound around with gaps between adjacent winding at the front end side as shown in <FIG>.

It is noted that the hollow coil body <NUM> and the coil body <NUM> correspond to the "shaft" and the "first coil. " A portion of the coil body <NUM> wound around closely and the coil body <NUM> correspond to the "spirally-arranged protruding portion" and the "second coil. " Further, the coil body <NUM> corresponds to the "portion having an increasing outer diameter.

The hollow coil body <NUM> is formed such that the metal wires 41a, 41b, 41c, 41d, 41e, 41f, <NUM>, <NUM>, 41j, and <NUM> of <NUM> stainless steel wires are twisted into a hollow shape as in the hollow coil body <NUM>. The hollow coil body <NUM> has a cylindrical hollow shape from the front end to the connector <NUM>.

Further, the coil body <NUM> is formed such that the metal wires 42a, 42b, 42c, 42d, 42e, 42f, <NUM>, <NUM>, 42j, <NUM>, <NUM>, 42n, 42p, 42q, 42r, and <NUM> of <NUM> stainless steel wires are wound around on a surface of the coil body <NUM> in the same direction (counterclockwise, facing to the front end) as the hollow coil body <NUM>. The coil body <NUM> also has a cylindrical hollow shape from the front end to the connector <NUM>.

Further, the coil body <NUM> is formed such that the metal wire 43a of a single stainless steel wire is wound around on a surface of the coil body <NUM>. The hollow coil body <NUM> also has a cylindrical hollow shape from the front end to the connector <NUM>.

Further, the coil body <NUM> is formed such that the metal wire 44a of a single stainless steel wire is wound around the surface of the coil body <NUM> in the same direction (clockwise, facing to the front end) as the coil body <NUM> (clockwise, facing to the front end).

According to the present embodiment, each wire in the hollow coil body <NUM> and the coil body <NUM> is wound around closely (see <FIG>). The coil body <NUM> is twistedly formed on the surface of the hollow coil body <NUM>. This means that the hollow coil body <NUM> and the coil body <NUM> which correspond to the shaft collectively have a hollow shape having an outer diameter of a front end smaller than that of a base end. The coil body <NUM> provides a spirally-arranged protruding portion protruding outwardly (the outermost surface of the dilator <NUM>, the outermost portion) on an outer peripheral surface <NUM> of the hollow coil body <NUM>, and the coil body <NUM> provides a spirally-arranged protruding portion protruding outwardly (the outermost surface of the dilator <NUM>, the outermost portion) on an outer peripheral surface 42T of the coil body <NUM>. These spirally-arranged protruding portions each have gaps between adjacent portions (adjacent portions of a metal wire) along an axis A of the hollow coil body <NUM>. Further, the coil body <NUM> is provided on the coil body <NUM> which corresponds to a portion where the shaft has an increasing outer diameter.

The dilator <NUM> (the multilayer body <NUM>) according to the present embodiment can ensure the front-end flexibility of the dilator <NUM> (the multilayer body <NUM>) and can maintain the pushability and torquability of the dilator <NUM> (the multilayer body <NUM>) even when the dilator <NUM> (the multilayer body <NUM>) is longer and curved. Further, the screw effect of the single metal wire 43a and the single metal wire 44a extending contiguously toward the front end from the base end of the coil body <NUM> can further be improved when the multilayer body <NUM> is rotated. This enables the dilator <NUM> to be easily advanced not only by a pushing operation but also by a rotational operation. In addition, the diameter of a pre-formed hole can be increased more easily by the coil body <NUM> provided at the coil body <NUM> which corresponds to a portion where the shaft has an increasing outer diameter.

It is noted that when the amounts of gap between adjacent windings of the metal wire 44a and the metal wire 43a are formed so as to be gradually reduced toward the base end side in the present embodiment, the following effect can be observed: the stiffness of the dilator <NUM> (the multilayer body <NUM>) along the axis direction can be gradually changed so that the dilator <NUM> (the multilayer body <NUM>) can easily enter into the inside even when an approach pathway meanders.

Further, a shaft composed of the hollow coil body <NUM> and the coil body <NUM> (the first coil) each including a plurality of metal wires wound around into a hollow shape can improve the flexibility of the shaft and the transmissibility of torque via the shaft. Further, a spirally-arranged protruding portion composed of the coil body <NUM> (the second coil) including a single metal wire wound around on the outer peripheral surface <NUM> of the hollow coil body <NUM> and the coil body <NUM> (the second coil) wound around on an outer peripheral surface 42B of the coil body <NUM> can be easily formed, can ensure the flexibility of the front end of the dilator <NUM> by virtue of the elasticity of the second coil, and can improve the torquability. Further, each wire of the hollow coil body <NUM> and the coil body <NUM>, and each element wire of the coil <NUM> and the coil body <NUM> are wound around in directions opposite to each other. Therefore, even when the dilator <NUM> is rotated in a direction to open the hollow coil body <NUM> and the coil body <NUM>, a force is applied in a direction to close the coil body <NUM> and the coil body <NUM> to prevent the opening of the hollow coil body <NUM> and the coil body <NUM>. This allows a force applied to the connector <NUM> of the dilator <NUM> to be transmitted to the front end side.

<FIG> shows a front end portion of a dilator (a multilayer body) according to a sixth embodiment.

In <FIG>, a dilator <NUM> includes: a multilayer body <NUM> including a hollow coil body <NUM> including a plurality of metal wires 51a, 51b, 51c, 51d, 51e, 51f, <NUM>, <NUM>, 51j, and <NUM> wound around into a hollow shape, a hollow coil body <NUM> including a plurality of metal element wires 52a, 52b, 52c, 52d, 52e, 52f, <NUM>, <NUM>, 52j, <NUM>, <NUM>, 52n, 52p, 52q, 52r, and <NUM> wound around with gaps between adjacent winding on an outer periphery of the hollow coil body <NUM> at a position apart from a front end toward the base end of the hollow coil body <NUM> in the same direction (counterclockwise, facing to the front end) as the hollow coil body <NUM> (counterclockwise, facing to the front end), and a coil body <NUM> including a single wire 53a wound around on the outer peripheries of the hollow coil body <NUM> and the coil body <NUM> from the front end of the hollow coil body <NUM> in a direction (clockwise, facing to the front end) opposite to the hollow coil body <NUM>; and a connector <NUM> having a hollow shape and connected to a base end of the multilayer body <NUM>.

Here, the multilayer body <NUM> has a stepped and cylindrical hollow shape as in the multilayer body <NUM> according to the third embodiment, but it differs from the multilayer body <NUM> in that the coil body <NUM> in the multilayer body <NUM> according to the present embodiment is formed integrally and continuously while the coil body <NUM>, the coil body <NUM>, and the coil body <NUM> in the multilayer body <NUM> according to the third embodiment are formed as separate members. That is, in the coil body <NUM>, the single metal wire 53a is wound around closely at the base end side and wound around with gaps between adjacent winding at the front end side of the coil body <NUM> and the front end side of the coil body <NUM>.

It is noted that the hollow coil body <NUM> and the coil body <NUM> correspond to the "shaft" and the "first coil. " The portion of the coil body <NUM> wound around with gaps between adjacent winding corresponds to the "spirally-arranged protruding portion" and the "second coil. " Further, the coil body <NUM> corresponds to the "portion having an increasing outer diameter.

The hollow coil body <NUM> is formed such that the metal wires 51a, 51b, 51c, 51d, 51e, 51f, <NUM>, <NUM>, 51j, and <NUM> of <NUM> stainless steel wires are twisted into a hollow shape as in the hollow coil body <NUM>. The hollow coil body <NUM> has a cylindrical hollow shape from the front end to the connector <NUM>.

Further, the coil body <NUM> is formed such that the metal wires 52a, 52b, 52c, 52d, 52e, 52f, <NUM>, <NUM>, 52j, <NUM>, <NUM>, 52n, 52p, 52q, 52r, and <NUM> of <NUM> stainless steel wires are wound around on a surface of the coil body <NUM> in the same direction (counterclockwise, facing to the front end) as the hollow coil body <NUM>. The coil body <NUM> also has a cylindrical hollow shape from the front end to the connector <NUM>.

Further, the coil body <NUM> is formed such that the metal wire 53a of a single stainless steel wire is wound around on the surfaces of the coil body <NUM> and the coil body <NUM>. The hollow coil body <NUM> also has a cylindrical hollow shape from the front end to the connector <NUM>.

According to the present embodiment, each wire in the hollow coil body <NUM> and the coil body <NUM> is wound around closely (see <FIG>). The coil body <NUM> is twistedly formed on the surface of the hollow coil body <NUM>. This means that the hollow coil body <NUM>, the coil body <NUM>, and the closely wound around portion of the coil body <NUM> which correspond to the shaft collectively have a hollow shape having an outer diameter of a front end smaller than that of a base end. The coil body <NUM> provides a spirally-arranged protruding portion protruding outwardly (from the outermost surface and the outermost portion of the dilator <NUM>) on an outer peripheral surface <NUM> of the hollow coil body <NUM> and an outer peripheral surface 52T of the coil body <NUM>. The above spirally-arranged protruding portion has gaps between adjacent portions (adjacent portions of a metal wire) along an axis A of the hollow coil body <NUM>. Further, the coil body <NUM> is provided at the coil body <NUM> which corresponds to a portion where the shaft has an increasing outer diameter.

It is noted that metal wires made of stainless steel are used for the wires of the hollow coil body <NUM>, the coil body <NUM>, and the coil body <NUM> in the present embodiment, but they are not limited to stainless steel wires. They may be those made of a superelastic alloy such as nickel-titanium. Further, they are not limited to metal wires and may be resin wires.

The dilator <NUM> (the multilayer body <NUM>) of the present embodiment can ensure the front-end flexibility of the dilator <NUM> (the multilayer body <NUM>) and can maintain the pushability and torquability of the dilator <NUM> (the multilayer body <NUM>) even when the dilator <NUM> (the multilayer body <NUM>) is longer and curved. Further, the screw effect of the single metal wire 53a extending contiguously toward the front end from the base end of the coil body <NUM> can further be improved when the multilayer body <NUM> is rotated. This enables the dilator <NUM> to be easily advanced not only by a pushing operation but also by a rotational operation. In addition, the diameter of a pre-formed hole can be increased more easily by the coil body <NUM> provided at the coil body <NUM> which corresponds to a portion where the shaft has an increasing outer diameter.

It is noted that when the amount of gap between adjacent windings of the metal wire 53a is formed so as to be gradually reduced toward the base end side in the present embodiment, the following effect can be observed: the stiffness of the dilator <NUM> (the multilayer body <NUM>) along the axis direction can be gradually changed so that the dilator <NUM> (the multilayer body <NUM>) can easily enter into the inside even when an approach pathway meanders.

Further, a shaft composed of the hollow coil body <NUM> and the coil body <NUM> (the first coil) each including a plurality of metal wires wound around into a hollow shape can improve the flexibility of the shaft and the transmissibility of torque via the shaft. Further, a spirally-arranged protruding portion composed of the coil body <NUM> (the second coil) including a single metal wire wound around the outer peripheral surface <NUM> of the hollow coil body <NUM> and the outer peripheral surface 52T of the hollow coil body <NUM> can be easily formed, can ensure the flexibility of the front end of the dilator <NUM> by virtue of the elasticity of the second coil, and can improve the torquability. Further, each wire of the hollow coil body <NUM> and the coil body <NUM> and the wire of the coil body <NUM> are wound around in directions opposite to each other. Therefore, even when the dilator <NUM> is rotated in a direction to open the hollow coil body <NUM> and the coil body <NUM>, a force is applied in a direction to close the coil body <NUM> to prevent the opening of the hollow coil body <NUM> and the coil body <NUM>. This allows a force applied to the connector <NUM> of the dilator <NUM> to be transmitted to the front end side.

<FIG> shows a front end portion of a dilator (a multilayer body) according to a seventh embodiment. In <FIG>, the left side in the figure corresponds to the front end side (the distal side) which is to be inserted into the body, and the right side corresponds to the base end side (the hand side, the proximal side) which is to be operated by an operator such as a surgeon.

In <FIG>, a dilator <NUM> includes: a multilayer body <NUM> including a hollow coil body <NUM> including a plurality of metal wires 61a, 61b, 61c, 61d, 61e, 61f, <NUM>, <NUM>, 61j, and <NUM> wound around into a hollow shape, a hollow coil body <NUM> including a plurality of metal wires 62a, 62b, 62c, 62d, 62e, 62f, <NUM>, <NUM>, 62j, <NUM>, <NUM>, 62n, 62p,62q, 62r, and <NUM> wound around with gaps between adjacent winding on an outer periphery of the hollow coil body <NUM> at a position apart from a front end toward the base end of the hollow coil body <NUM> in the same direction (counterclockwise, facing to the front end) as the hollow coil body <NUM> (counterclockwise, facing to the front end), and a coil body <NUM> including a single wire 63a wound around on the outer peripheries of the hollow coil body <NUM> and the coil body <NUM> from the front end of the hollow coil body <NUM> in a direction (clockwise, facing to the front end) opposite to the hollow coil body <NUM>; and a connector <NUM> having a hollow shape and being connected to a base end of the multilayer body <NUM>. However, the dilator <NUM> differs from the dilator <NUM> in that the multilayer body <NUM> of the dilator <NUM> has a forefront portion <NUM> at the front end of the hollow coil body <NUM> while the multilayer body <NUM> of the dilator <NUM> does not have the forefront portion <NUM> at the front end of the hollow coil body <NUM>.

The forefront portion <NUM> is formed by casting a solder material (a silver-tin solder material, a gold-tin solder material, and the like) into the front end of the hollow coil body <NUM>, and has a substantially cylindrical hollow shape. Further, the surface of the forefront portion <NUM> is a flat while the surface of the front end of the multilayer body <NUM> is an uneven.

The multilayer body <NUM> has a stepped and cylindrical hollow shape as in the multilayer body <NUM> according to the third embodiment, but it differs from the multilayer body <NUM> in that the coil body <NUM> in the multilayer body <NUM> according to the present embodiment is formed integrally and continuously while the coil body <NUM>, the coil body <NUM>, and the coil body <NUM> in the multilayer body <NUM> according to the third embodiment are formed as separate members. That is, in the coil body <NUM>, the single metal wire 63a is closely wound around at the base end side and is wound around with gaps between adjacent winding at the front end side of the coil body <NUM> and the front end side of the coil body <NUM>.

The hollow coil body <NUM> is formed such that the metal wires 61a, 61b, 61c, 61d, 61e, 61f, <NUM>, <NUM>, 61j, and <NUM> of <NUM> stainless steel wires are twisted into a hollow shape as in the hollow coil body <NUM>. The hollow coil body <NUM> has a cylindrical hollow shape from the front end to the connector <NUM>.

Further, the coil body <NUM> is formed such that the metal wires 62a, 62b, 62c, 62d, 62e, 62f, <NUM>, <NUM>, 62j, <NUM>, <NUM>, 62n, 62p, 62q, 62r, and <NUM> of <NUM> stainless steel wires are wound around on a surface of the coil body <NUM> in the same direction (counterclockwise, facing to the front end) as the hollow coil body <NUM>. The hollow coil body <NUM> also has a cylindrical hollow shape from the front end to the connector <NUM>.

Further, the coil body <NUM> is formed such that the metal wire 63a of a single stainless steel wire is wound around on the surfaces of the coil body <NUM> and the coil body <NUM>. The hollow coil body <NUM> also has a cylindrical hollow shape from the front end to the connector <NUM>.

According to the present embodiment, each wire in the hollow coil body <NUM> and the coil body <NUM> is wound around closely (see <FIG>). The coil body <NUM> is twistedly formed on the surface of the hollow coil body <NUM>. This means that the hollow coil body <NUM> and the coil body <NUM> which correspond to the shaft collectively have a hollow shape having an outer diameter of a front end smaller than that of a base end. The coil body <NUM> provides a spirally-arranged protruding portion protruding outwardly (the outermost surface of the dilator <NUM>, the outermost portion) on an outer peripheral surface <NUM> of the hollow coil body <NUM> and an outer peripheral surface 62T of the coil body <NUM>. The above spirally-arranged protruding portion has gaps between adjacent portions (adjacent portions of a metal wire) along an axis A of the hollow coil body <NUM>. Further, the coil body <NUM> is provided at the coil body <NUM> which corresponds to a portion where the shaft has an increasing outer diameter.

According to the dilator <NUM> (the multilayer body <NUM>), the forefront portion <NUM> having a flat surface is connected to the front end of the multilayer body <NUM>. This configuration can further improve insertability into a punctured portion by first pressing the dilator against the punctured portion, and then pushing and rotating the dilator inward. In addition, this configuration can ensure the front-end flexibility of the dilator <NUM> (the multilayer body <NUM>) and can improve the pushability and torquability of the dilator <NUM> (the multilayer body <NUM>) even when the dilator <NUM> (the multilayer body <NUM>) is longer and curved. Further, the screw effect of the single metal wire 63a extending contiguously toward the front end from the base end of the coil body <NUM> can further be improved when the multilayer body <NUM> is rotated. This enables the dilator <NUM> to be easily advanced not only by a pushing operation but also by a rotational operation. In addition, the diameter of a pre-formed hole can be increased more easily by the coil body <NUM> provided at the coil body <NUM> which corresponds to a portion where the shaft has an increasing outer diameter.

It is noted that when the amount of gap between adjacent windings of the metal wire 63a is formed so as to be gradually reduced toward the base end side in the present embodiment, the following effect can be observed: the stiffness of the dilator <NUM> (the multilayer body <NUM>) along the axis direction can be gradually changed so that the dilator <NUM> (the multilayer body <NUM>) can easily enter into the inside even when an approach pathway meanders.

Further, the shaft composed of the hollow coil body <NUM> and the coil body <NUM> (the first coil) each including a plurality of metal wires wound around into a hollow shape can improve the flexibility of the shaft and the transmissibility of torque via the shaft. Further, a spirally-arranged protruding portion composed of the coil body <NUM> (the second coil) including a single metal wire wound around on an outer peripheral surface <NUM> of the hollow coil body <NUM> and an outer peripheral surface 62T of the hollow coil body <NUM> can be easily formed, can ensure the flexibility of the front end of the dilator <NUM> by virtue of the elasticity of the second coil, and can improve the torquability. Further, each wire of the hollow coil body <NUM> and the coil body <NUM>, and the wire of the coil body <NUM> are wound around in directions opposite to each other. Therefore, even when the dilator <NUM> is rotated in a direction to open the hollow coil body <NUM> and the coil body <NUM>, a force is applied in a direction to close the coil body <NUM> to prevent the opening of the hollow coil body <NUM> and the coil body <NUM>. This allows a force applied to the connector <NUM> of the dilator <NUM> to be transmitted to the front end side.

<FIG> shows a front end portion of a dilator (a multilayer body) according to an eighth embodiment.

In <FIG>, a dilator <NUM> includes: a multilayer body <NUM> including a hollow coil body <NUM> including a plurality of metal wires 21a, 21b, 21c, 21d, 21e, 21f, <NUM>, <NUM>, 21j, and <NUM> wound around into a hollow shape, a coil body <NUM> including a plurality of metal wires 22a, 22b, 22c, 22d, 22e, 22f, <NUM>, <NUM>, 22j, <NUM>, <NUM>, 22n, 22p, 22q, 22r, and <NUM> wound around with gaps between adjacent winding on an outer periphery of the hollow coil body <NUM> at a position apart from a front end toward the base end of the hollow coil body <NUM> in a direction (clockwise, facing to the front end) opposite to the hollow coil body <NUM>, and a coil body <NUM> including a single metal wire 24a wound around with gaps between adjacent winding on the outer periphery of the coil body <NUM> at the base end side from a front end of the coil body <NUM>; and a connector <NUM> having a hollow shape and being connected to a base end of the multilayer body <NUM>.

Here, the multilayer body <NUM> has a stepped and cylindrical hollow shape as in the multilayer body <NUM> according to the third embodiment but has a two-layer structure where the coil <NUM> and the coil <NUM> are removed from the multilayer body <NUM>.

Even in a case where the dilator <NUM> (the multilayer body <NUM>) is longer and curved, the dilator <NUM> (the multilayer body <NUM>) according to the present embodiment can ensure the front-end flexibility of the dilator <NUM> (the multilayer body <NUM>), can maintain the pushability and torquability of the dilator <NUM> (the multilayer body <NUM>), and can enable the diameter of a pre-formed hole to be easily increased by the screw effect of the metal wire 24a upon rotation of the multilayer body <NUM>.

However, the multilayer body <NUM> according to the present embodiment has a two-layer structure while the multilayer body <NUM> according to the third embodiment has a three-layer structure. Therefore, the multilayer body <NUM> may have a somewhat inferior ability for increasing the diameter of a hole as compared with the multilayer body <NUM>.

It is noted that when the amount of gap between adjacent windings of the metal wire 24a is formed so as to be gradually reduced toward the base end side in the present embodiment, the following effect can be observed: the stiffness of the dilator <NUM> (the multilayer body <NUM>) along the axis direction can be gradually changed so that the dilator <NUM> (the multilayer body <NUM>) can easily enter into the inside even when an approach pathway meanders.

Hereinbefore, the embodiments of the present invention are described, but the present invention shall not be limited to these embodiments. Rather, various modifications may be made.

For example, the hollow coil body <NUM>, the hollow coil body <NUM>, the hollow coil body <NUM>, the hollow coil body <NUM>, the hollow coil body <NUM>, and the hollow coil body <NUM> are described as hollow coil bodies including <NUM> wires in the aforementioned embodiments, but the number of wires shall not be limited to <NUM>. The number may be one or more.

Further, the coil body <NUM>, the coil body <NUM>, the coil body <NUM>, and the coil body <NUM> are described as coil bodies including <NUM> wires in the aforementioned embodiments, but the number of wires shall not be limited to <NUM>. The number may be one or more.

Moreover, the coil body <NUM> and the coil body <NUM> are described as coil bodies including <NUM> wires in the aforementioned embodiments, but the number of wires shall not be limited to <NUM>. The number may be one or more.

Moreover, the forefront portion <NUM> of the second embodiment is described to be formed by casting a solder material into the front end of the multilayer body <NUM>. However, the outer periphery of the coil body <NUM> and/or the coil body <NUM> in the vicinity of the front end portion of the multilayer body <NUM> may be sanded to form the forefront portion <NUM> having a flat surface. This also applies to the forefront portion <NUM>.

Furthermore, the forefront portion <NUM> according to the second embodiment is fixed to the front end of the multilayer body <NUM>. However, similar effects as the multilayer body <NUM> according to the second embodiment or the multilayer body <NUM> according to the seventh embodiment may be produced even when the forefront portion is fixed to the front end of the multilayer body <NUM> according to the third embodiment, the front end of the multilayer body <NUM> according to the fourth embodiment, the front end of the multilayer body <NUM> according to the fifth embodiment, the front end of the multilayer body <NUM> according to the eighth embodiment,.

Further, the outer peripheries of the multilayer bodies <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> according to the first to eighth embodiments may be coated with a resin(s).

In the embodiments shown in <FIG>, shown are dilators each including a shaft having no surface coating. However, the shaft may have various types of coating on the side of the surface thereof (including a portion between the shaft and the spirally-arranged protruding portion). Examples of the coating include, for example, a protective film on the surface of the shaft (representative example: a plating film), an underlying film for improving adhesiveness between the shaft and the spirally-arranged protruding portion, and the like.

Preferably, the spirally-arranged protruding portions according to the embodiments as shown in <FIG> are not configured to serve as a blade. The dilators according to the present embodiments are intended for expanding a hole pre-formed on a target object (for example, the wall of a digestive tract such as the patient's stomach). Therefore, if the spirally-arranged protruding portion serves as a blade, living tissue at the inner surface of the hole may be damaged.

Claim 1:
A dilator (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) comprising:
a hollow shaft (<NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>) having an outer diameter of a front end smaller than that of a base end; and
a grip portion (<NUM>) connected to the base end of the shaft (<NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>), wherein,
a spirally-arranged protruding portion (<NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>; <NUM>) protruding outwardly is provided on an outer peripheral surface of the shaft (<NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>), and
the spirally-arranged protruding portion (<NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>; <NUM>) has gaps between adjacent portions along an axis of the shaft (<NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>), characterised in that the spirally-arranged protruding portion (<NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>; <NUM>) includes a coil (<NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>; <NUM>) including one or more wires wound around on the outer peripheral surface of the shaft (<NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>; <NUM>, <NUM>) .