Patent Description:
The human heart has four chambers and also has four valves, which are a mitral valve, a tricuspid valve, an aortic valve and a pulmonary valve respectively. The mitral valve is located between a left atrium and a left ventricle and guarantees, like a one-way valve, that blood circulation flows from the left atrium to the left ventricle by a certain flow amount. The mitral valve is composed of five parts, namely valve leaflet, an annulus, a papillary muscle, chordae tendineae and a commissure. When the mitral valve is closed normally, two valve leaflets are located on the same plane and closed tightly, so that blood reflux of the left ventricle can be completely blocked. Functional completeness of the mitral valve requires an appropriate size of a mitral valve annulus, a complete structure of valve leaflets, papillary muscle contraction for stretching the chordae tendineae to play a formation role of the valve leaflets, muscle contraction of the left ventricle for producing an appropriate close force and normal ventricular form and function. Reflux of the mitral valve may be caused if any one of these factors is abnormal, and blood flows back to the left atrium from the left ventricle.

<CIT> discloses an insertion instrument for anchor assembly. The insertion instrument is configured to eject a pair of anchor bodies across an anatomical gap so as to approximate the gap. The insertion instrument can include a single cannula that retains the pair of anchor bodies in a stacked relationship, or a pair of adjacent cannulas that each retain respective anchor bodies. The insertion instrument can be actuated so as to eject the anchor bodies into respective target anatomical locations.

<CIT> provides devices and methods of treating a tricuspid valve regurgitation. Specifically, one aspect of the present teachings provides devices and methods of identifying a suitable location on the tricuspid annulus, placing a wire across the tricuspid annulus at such an identified location, deploying a tissue anchor across such an identified location, deploying two or more tissue anchors and coupling the tissue anchors with a flexible tensioning member, and applying tension to a flexible tensioning member that is coupled with the two or more tissue anchors, plicating tissues between each pair of the two or more tissue anchors, and reducing the circumference of the tricuspid annuls. As a result, a regurgitation jet is reduced or eliminated.

<CIT> discloses a pull wire locking catheter for mitral valve repair. The pull wire locking catheter is mainly used for adjusting and locking a pull wire implanted after mitral valve regurgitation diseases, valve ring expansion and chordae tendineae rupture under ultrasound or radiography in real time, and complete reversible operation can be realized. Operation of a surgeon can be simplified, and the pull wire locking catheter has excellent therapeutic effects on mitral valve regurgitation.

<CIT> discloses devices and methods for locking and/or cutting tethers during a tissue modification procedure. In some variations, a tether may be used to tighten tissue by bringing two pieces or sections of the tissue together. The tether, which may be under tension, may be locked to maintain the tension, and excess tether may be severed, using one or more of the devices and/or methods. The devices and/or methods may be used, for example, in minimally invasive procedures.

<CIT> discloses apparatus for connecting the ends of a suture stitch, which includes a piston and cylinder combination with one end of the suture secured to the cylinder. The other end of the suture initially includes a needle for penetrating two tissues to be approximated and then passing the needle and its attached suture through aligned openings in the cylinder sidewalls. The portion of the suture passing through the cylinder is trapped therein by the depression of the piston to engage the bottom inside surface of the cylinder which locks that end of the suture in place.

With social development and aging of population, an incidence rate of mitral valve reflux is in a tendency of obvious increase, the mitral valve reflux has become a common heart valve disease at present, which is mainly caused by incomplete closing of the mitral valve annulus, and thus a ring contraction apparatus for repair of incomplete closing of the mitral valve annulus needs to be provided.

Thus, a technical problem to be actually solved by the present application is to provide a ring contraction apparatus for repair of incomplete closing of a mitral valve annulus. The invention is defined in the independent claim.

As such, a ring contraction apparatus for a mitral valve annulus provided by the present application includes:.

Optionally, in the ring contraction apparatus for the mitral valve annulus, the locking mechanism includes:.

Optionally, in the ring contraction apparatus for the mitral valve annulus, a locking hole through which the ends of the traction wires pass is formed in a side wall of the locking body.

Optionally, in the ring contraction apparatus for the mitral valve annulus, a first mounting hole is also arranged in the side wall of the locking body;.

Optionally, in the ring contraction apparatus for the mitral valve annulus, the locking plug includes a base and a first annular boss formed on a periphery of a far end of the base, and the first annular boss applies an extrusion force to the elastomer; and
the far end of the elastomer is blocked onto a side of a proximal end of the first annular boss in a case that the elastomer is restored.

Optionally, in the ring contraction apparatus for the mitral valve annulus, a second annular boss protruding inwards is arranged on an inner wall of a far end of the locking body;.

Optionally, in the ring contraction apparatus for the mitral valve annulus, the locking mechanism further includes a conveying mechanism; the conveying mechanism includes an outer tube, a hanging sheath slidably arranged in the outer tube and a push inner tube slidably arranged in the hanging sheath;
a far end of the hanging sheath is detachably connected with a proximal end of the locking body, and a far end of the push inner tube is inserted into or is in sleeving fit with a proximal end of the locking plug; and both the locking body and the locking plug are located in the outer tube before the locking body is released.

Optionally, in the ring contraction apparatus for the mitral valve annulus, the puncturing mechanism includes:.

Optionally, in the ring contraction apparatus for the mitral valve annulus, a notch sinking inwards is formed in a side wall of the notch channel of the puncture needle; and in the folded state, the far ends of the fixing knots sleeve the notch, and the second ends of the traction wires are winded on the outer walls of the fixing knots after passing through the notch.

Optionally, in the ring contraction apparatus for the mitral valve annulus, each fixing knot is in a spiral shape or a round tube shape; and/or
a fixing head end is arranged on an end face of a far end of the outer sheath and is in a trumpet shape from its proximal end to its far end.

The technical solutions of the present application have the following advantages.

In order to more clearly describe specific implementations of the present application or technical solutions in the prior art, accompanying drawings needing to be used in the description of the specific implementations or the prior art will be briefly introduced below. Apparently, the accompanying drawings in the following description are some implementations of the present application. Those ordinarily skilled in the art may also obtain other accompanying drawings according to these accompanying drawings without making creative efforts.

The technical solutions of the present application will be clearly and completely described in the following with reference to the accompanying drawings. Apparently, the described embodiments are merely some rather than all of the embodiments of the present application. All other embodiments obtained by those ordinarily skilled in the art based on the embodiments of the present application without making creative efforts fall within the protection scope of the present application.

In description of the present application, it needs to be noted that unless otherwise specified and limited clearly, terms "mount", "connect" and "connection" are to be understood in a broad sense, for example, it may be a fixed connection, a detachable connection or an integrated connection; and it may be a direct connection, an indirect connection through an intermediate medium or communication between interiors of two elements. Specific meanings of the above terms in the present application may be understood by those ordinarily skilled in the art according to specific conditions.

Besides, technical features involved in different implementations of the present application described below may be combined mutually without a conflict between one another.

This embodiment provides a ring contraction apparatus for a mitral valve annulus, as shown in <FIG>, including at least two fixing mechanisms, a puncturing mechanism <NUM> and a locking mechanism <NUM>.

Any one of the fixing mechanisms includes a fixing knot <NUM> and a traction wire <NUM>, the traction wire <NUM> is mounted on the fixing knot <NUM>, two ends of the traction wire <NUM> are located outside a proximal end of the fixing knot <NUM>, the puncturing mechanism <NUM> is used for puncturing the fixing knot <NUM> and the traction wire <NUM> of any one of the fixing mechanisms onto an annulus, so that the fixing knot <NUM> is located on one side (for example, located on a side of a left atrium) of the annulus and the two ends of the traction wire are located on the other side (for example, located on a side of a left ventricle) of the annulus, as shown in <FIG>. Traction wires <NUM> of two adjacent fixing mechanisms are driven by a traction force to approach each other so as to shorten a distance between two adjacent fixing knots <NUM>, so that an annulus portion between the two adjacent fixing knots <NUM> is bent or creased, a circumferential length of the annulus is reduced, as shown in <FIG>, and thus a size of an inner hole of the annulus is reduced; and after the distance between the two fixing knots <NUM> is adjusted in place, the locking mechanism <NUM> is used to lock end parts of the traction wires <NUM> in the two adjacent fixing mechanisms to the annulus, so that the annulus is kept in a state in which the inner hole is shrunken, and as the size of the inner hole of the annulus is reduced, the annulus is closed more easily, thereby solving the problem of incomplete closing of the annulus and achieving a repair effect.

As for the locking mechanism <NUM>, preferably, as shown in <FIG>, the locking mechanism <NUM> includes a locking body <NUM> and a locking plug <NUM>. The locking body <NUM> has a first channel extending in a length direction of the locking body; the locking plug <NUM> is inserted into the first channel so as to clamp the traction wires <NUM> between the locking plug <NUM> and the locking body <NUM>, at the moment, the two ends of the traction wires <NUM> need to extend out of a proximal end of the locking body <NUM>, so as to lock the traction wires <NUM> onto the locking body <NUM>, and the adjusted distance between the two fixing knots <NUM> remains. During locking, the locking plug <NUM> only needs to be inserted into the locking body <NUM> from a proximal end to a far end.

Further preferably, as shown in <FIG>, a locking hole <NUM> through which the ends of the traction wires <NUM> pass is formed in a side wall of the locking body <NUM>. Before the locking plug <NUM> is inserted into the locking body <NUM>, the two ends of the traction wires <NUM> pass through the locking hole <NUM> after passing through the first channel and then adjust the distance between the two fixing knots <NUM> by applying a traction force to the traction wires <NUM>, after the distance is adjusted in place, the locking plug <NUM> is inserted into the locking body <NUM>, and by forming the locking hole <NUM>, the two ends of the traction wires <NUM> do not need to extend out of the proximal end of the first channel and only need to extend out of the locking hole <NUM>, which is also convenient for applying the traction force to the traction wires <NUM>.

Further preferably, as shown in <FIG> and <FIG>, a first mounting hole <NUM> is also formed in the side wall of the locking body <NUM>; the locking mechanism <NUM> further includes at least one elastomer <NUM>, a proximal end of the elastomer <NUM> is formed in the first mounting hole <NUM>, and a far end of the elastomer tends to extend into the first channel under an action of an own deformation amount; and the elastomer <NUM> swings towards an inside of the first mounting hole <NUM> under an extrusion force of an outer wall of the locking plug <NUM> in a case that the locking plug <NUM> is inserted towards the first channel, and after the locking plug <NUM> crosses the far end of the elastomer <NUM>, the elastomer <NUM> is restored and the far end of the elastomer is blocked onto the locking plug <NUM>, so as to limit the proximal end of the locking plug <NUM> onto the locking body <NUM> and avoid sliding out from the proximal end of the locking body <NUM>.

Specifically, as shown in <FIG>, the locking plug <NUM> includes a base <NUM> and a first annular boss <NUM> formed on a periphery of a far end of the base <NUM>, and the first annular boss <NUM> applies an extrusion force to the elastomer <NUM>; and the far end of the elastomer <NUM> is blocked onto a side of a proximal end of the first annular boss <NUM> in a case that the elastomer <NUM> is restored, so as to achieve a blocking force for the locking plug <NUM>. As a variation, only the far end of the base <NUM> and the first annular boss <NUM> may also be arranged, and an end surface of the first annular boss <NUM> is used as a proximal end surface of the locking plug <NUM>.

The locking body <NUM> and the elastomer <NUM> are integrally formed, preferably, a nickel-titanium alloy material, or other medical deformable alloy material or a memory alloy material is used. As for the elastomer <NUM>, preferably, the elastomer <NUM> is an elastic piece or a spring.

As for a material of the locking plug <NUM>, preferably, a rubber material is used for forming a rubber plug, or another medical high molecular material is used.

Further preferably, as shown in <FIG>, a second annular boss <NUM> protruding inwards is arranged on an inner wall of the far end of the locking body <NUM>; and a far end of the first annular boss <NUM> is maintained between the second annular boss <NUM> and the elastomer <NUM> under blocking of the second annular boss <NUM>. That is, after the locking plug <NUM> slides in place on the locking body <NUM>, under cooperation of the second annular boss <NUM> and the elastomer <NUM>, the locking plug <NUM> is limited on the locking body <NUM>, and the locking plug <NUM> cannot move relative to the locking body <NUM>, so as to further guarantee the locking effect on the traction wires <NUM>.

Shapes of the above first channel and the first mounting hole <NUM> are optimally round holes or certainly may also be holes in other shapes, such as, rectangular holes or elliptical holes or holes in other shapes.

Preferably, as shown in <FIG>, the above locking mechanism <NUM> further includes a conveying mechanism <NUM> for conveying the locking body <NUM> and the locking plug <NUM>; and the conveying mechanism includes an outer tube <NUM>, a hanging sheath <NUM> slidably arranged in the outer tube <NUM> and a push inner tube <NUM> slidably arranged in the hanging sheath <NUM>. A far end of the hanging sheath <NUM> is detachably connected with the proximal end of the locking body <NUM>, and a far end of the push inner tube <NUM> is inserted into an inner hole of a proximal end of the locking plug <NUM> or sleeves the proximal end of the locking plug <NUM>; and both the locking body <NUM> and the locking plug <NUM> are located in the outer tube <NUM> before the locking body <NUM> is not released.

Through movement of the outer tube <NUM>, the whole conveying mechanism is transapically conveyed to nearby the mitral valve annulus, the outer tube <NUM> stops moving, the hanging sheath <NUM> pushes the locking body <NUM> to cause the locking body <NUM> to extend out of the far end of the outer tube <NUM>, and the hanging sheath <NUM> is separated from the locking body <NUM>. The ends of the traction wires <NUM> are punctured in the locking hole <NUM>, the traction force is applied to the ends of the traction wires <NUM> so as to adjust the distance between the two fixing knots <NUM>, after the distance between the two fixing knots <NUM> is adjusted in place, the push inner tube <NUM> pushes the locking plug to be inserted into the locking body <NUM>, and then in view of the limiting effect of the elastomer <NUM>, the push inner tube <NUM> is withdrawn and is separated from locking, and finally, the whole conveying mechanism is withdrawn from a human body by withdrawing the outer tube <NUM>.

Preferably, as shown in <FIG>, two notch grooves <NUM> which are in symmetric distribution are arranged on the proximal end of the locking body <NUM>, and correspondingly, an ear hanger (not shown in Figure) suitable for being clamped into each ear hanger notch is arranged at the far end of the hanging sheath <NUM>; before releasing, the ear hanger remains clamped into the notch grooves <NUM> under a radial restraining force of the outer tube <NUM>; and when the hanging sheath <NUM> extends out of the outer tube <NUM>, the ear hanger is restored under an action of an own deformation amount, tends to swing outwards and exit from the notch grooves <NUM>, so that separation of the hanging sheath <NUM> from the locking body <NUM> is implemented.

As for the puncturing mechanism <NUM>, as shown in <FIG>, <FIG> and <FIG>, the puncturing mechanism <NUM> includes an outer sheath <NUM>, a puncture needle <NUM> and a push sheath <NUM>. The puncture needle <NUM> is slidably arranged in the outer sheath <NUM>, a notch channel <NUM> extending in a length direction of the puncture needle <NUM> is formed in an outer wall of a far end of the puncture needle <NUM>, and the push sheath <NUM> is slidably arranged in the outer sheath <NUM> to sleeve the puncture needle.

The fixing knots <NUM> have a folded state of being folded into the outer sheath <NUM> and a released state of being punctured onto the annulus. In the folded state, as shown in <FIG> and <FIG>, the fixing knots <NUM> sleeve an outer wall of the notch channel <NUM> of the puncture needle, a proximal end of the puncture needle and a far end of the push sheath <NUM> are distributed oppositely, a first end of each traction wire <NUM> is located in the notch channel <NUM>, and a second end of each traction wire <NUM> passes through the notch channel <NUM>, then is winded onto an outer wall of the fixing knot <NUM> from a far end of the fixing knot <NUM> and extends into the puncture needle via a proximal end of the notch channel <NUM> so as to overlap the first end and the second end; and end parts of the traction wires <NUM> which are in overlay distributed may extend out of the proximal end of the puncture needle, so that an operator conveniently applies the traction force to the traction wires <NUM>; or the first end and the second end are distributed in the puncture needle, connected with an operating mechanism and applying the traction force to the traction wires <NUM>.

When the fixing knots <NUM> need to be released, as shown in <FIG>, an end face of the far end of the outer sheath <NUM> abuts against the annulus firstly, then the puncture needle and the push sheath <NUM> slide synchronously towards the far end, the push sheath <NUM> is used for pushing the fixing knots <NUM>, and it is guaranteed that when the puncture needle and the push sheath <NUM> are entirely punctured into the mitral valve annulus, the fixing knots <NUM> are located on a side of a mitral valve close to an atrium, as shown in <FIG>; due to existence of the notch channel <NUM>, the puncture needle is separated from the fixing knots <NUM>, and the puncture needle is withdrawn firstly, as shown in <FIG>; then the traction force is applied to the traction wires <NUM>, the fixing knots <NUM> are bent into a ring shape, as shown in <FIG>; then the entire outer sheath is withdrawn from the human body, and the fixing knots <NUM> and the traction wires <NUM> remain being on the mitral valve annulus, as shown in <FIG>, to complete a releasing process of the fixing knots <NUM>; and in the released state, the traction wires <NUM> sleeve side walls of the fixing knots <NUM>, the traction wires <NUM> are punctured into the annulus, and the fixing knots <NUM> are pulled by traction of the traction wires <NUM> to be bent into a ring shape.

Preferably, as shown in <FIG>, a notch <NUM> sinking inwards is formed in a side wall of the notch channel <NUM> of the puncture needle <NUM>; and in the folded state, the far ends of the fixing knots <NUM> sleeve the notch <NUM>, and the second ends of the traction wires <NUM> are winded on the outer walls of the fixing knots <NUM> after passing through the notch <NUM>, so that the fixing knots <NUM> and the traction wires <NUM> are conveniently positioned.

Further preferably, as shown in <FIG>, a fixing head end <NUM> is arranged on an end face of the far end of the outer sheath <NUM> and is in a trumpet shape from a proximal end to a far end of the fixing head end, so that an abutting area of the fixing head end <NUM> on the mitral valve annulus is increased, the annulus may be supported in a direction towards the atrium, and subsequent puncturing of the puncture needle <NUM> is convenient. Preferably, the fixing head end <NUM> is made of a medical high molecular material, has certain softness and can protect the annulus from being broken. For example, a nickel-titanium alloy or another memory alloy material may be used.

As for each fixing knot <NUM>, as shown in <FIG>, the fixing knot <NUM> may be a spiral tube, namely, a spring-like tube; or as shown in <FIG>, the fixing knot <NUM> may be directly a round tube. As for each fixing knot <NUM>, preferably, the fixing knot <NUM> uses polytetrafluoroethylene (ePTFE) or a nickel-titanium alloy or another medical high molecular or degradable material, has a certain deformation amount for conveniently forming the ring shape after subsequently puncturing in place, and a circular arc surface makes contact with human organ and does not damage the organ making contact with the circular arc surface.

Besides, preferably, the puncture needle <NUM> of the annulus is made of high-strength metal with a head being ground at a certain angle. The push sheath <NUM> is made of a metal material or a high molecular material, preferably, the traction wires <NUM> are made of polytetrafluoroethylene (ePTFE) or another high molecular material.

The ring contraction apparatus for the mitral valve annulus in the optimal implementation of this embodiment may achieve small incision insertion while the heart beats continuously, the dilated annulus is repaired, and a working process is explained by taking annulus repair between the left atrium and the left ventricle.

In an initial state, as shown in <FIG> or <FIG>, the fixing knots <NUM> and the traction wires <NUM> are located in the outer sheath <NUM>.

Firstly, as shown in <FIG>, it enters the left ventricle by cardiac apex puncturing, the outer sheath <NUM> is delivered to below the mitral valve annulus <NUM>, the fixing head end <NUM> abuts against the annulus, the annulus is pushed in a direction towards the left atrium, and a puncture point of the annulus is fixed by using an end surface of the far end of the fixing head end after adjusting the direction, as shown in <FIG>.

Then, the outer sheath <NUM> remains static, the puncture needle <NUM>, the fixing knots <NUM>, the traction wires <NUM> and the push sheath <NUM> push and puncture the annulus together forwards (in the direction towards the left atrium), the puncture needle <NUM>, the traction wires <NUM> and push sheath <NUM> are punctured on the annulus, and the fixing knots <NUM> are located on a side of the left atrium, as shown in <FIG>; then, the puncture needle <NUM> is withdrawn firstly, and then a push tube remains pushing the proximal ends of the fixing knots <NUM>, as shown in <FIG>; afterwards, the traction force is applied to the traction wires <NUM>, so the fixing knots <NUM> form the ring shape, and a part of the fixing knots <NUM> located at a left ventricle is knotted, so as to be fixed at an annulus puncture point, as shown in <FIG>; then, the outer sheath <NUM> is withdrawn to outside of a cardiac apex to complete puncturing of the first fixing knot <NUM>, as shown in <FIG>; and the same method is used, another fixing knot <NUM>, namely, the second fixing knot <NUM>, is implanted at the annulus away from the first fixing knot <NUM> by a distance L1, as shown in <FIG>.

Afterwards, the locking mechanism <NUM> is delivered to the annulus by using the conveying mechanism, the outer tube <NUM> is conveyed to the mitral valve annulus <NUM> through transapical puncture, the outer tube <NUM> stops moving, the hanging sheath <NUM> moves to push the locking body <NUM> to a bottom of the mitral valve annulus <NUM>, the end parts of the traction wires <NUM> of the two adjacent fixing knots <NUM> pass through the locking hole <NUM> via the first channel of the locking body <NUM> to extend towards the proximal end; then, the traction force is applied to the traction wires <NUM> through three-dimensional ultrasound and contrast navigation, the distance between the two annulus fixing knots <NUM> is adjusted in real time till reflux disappears, for example, the distance between the two fixing knots <NUM> is finally adjusted to L2, a circumferential length of the mitral valve annulus <NUM> is shortened, and thus, narrowing of the annulus is achieved; at the moment, the locking plug <NUM> is pushed to the farthest end of the locking body <NUM> through the push inner tube <NUM>, the elastic piece plays a role in blocking the locking plug <NUM>, the traction wires <NUM> are fixed onto the locking body <NUM>, ring contraction of the mitral valve annulus <NUM> is completed once, as shown in <FIG>; and finally, the outer tube <NUM>, the hanging sheath <NUM> and the push inner tube <NUM> are entirely withdrawn from the human body.

As shown in <FIG>, a plurality of pairs of fixing knots <NUM> may be implanted on the mitral valve annulus <NUM> in the above same manner to further reduce a size of the annulus.

As for the set number of fixing mechanisms, the number of fixing mechanisms is an even number, a pair of fixing mechanisms may implement a ring contraction function of the annulus, and the specific set number is not limited and may be selected according to actual demands.

Besides, a knotting position of the two ends of the traction wires <NUM> of each fixing knot <NUM> above is close to a position of the annulus, and the traction wires <NUM> may also be knotted and fixed at a cardiac apex according to a lesion of a patient to complete implantation and securing of the ring contraction apparatus.

Claim 1:
A ring contraction apparatus for a mitral valve annulus, comprising
at least two fixing mechanisms; wherein any one of the fixing mechanisms comprises a fixing knot (<NUM>) and a traction wire (<NUM>), the traction wire (<NUM>) is mounted on the fixing knot (<NUM>), and two ends of the traction wire (<NUM>) are located outside a proximal end of the fixing knot (<NUM>);
a puncturing mechanism (<NUM>), used for puncturing the fixing knot (<NUM>) and the traction wire (<NUM>) of any one of the fixing mechanisms into the annulus, so that the fixing knot (<NUM>) is located on one side of the annulus and two ends of the traction wire (<NUM>) are located on the other side of the annulus, wherein the traction wires (<NUM>) of the two adjacent fixing mechanisms are configured to be driven by a traction force to approach each other so as to shorten a distance between the two adjacent fixing knots (<NUM>); and
a locking mechanism (<NUM>), used for locking ends of the traction wires (<NUM>) in the two adjacent fixing mechanisms onto the annulus in a case that the traction wires (<NUM>) of the two adjacent fixing mechanism are pulled in place; characterized in that,
the locking mechanism (<NUM>) comprises a locking body (<NUM>), having a first channel extending in a length direction of the locking body; and a locking plug (<NUM>), inserted into the first channel so as to clamp the traction wires (<NUM>) between the locking plug (<NUM>) and the locking body (<NUM>);
the locking mechanism (<NUM>) further comprises a conveying mechanism; the conveying mechanism comprises an outer tube (<NUM>), a hanging sheath (<NUM>) slidably arranged in the outer tube (<NUM>) and a push inner tube (<NUM>) slidably arranged in the hanging sheath (<NUM>);
a far end of the hanging sheath (<NUM>) is detachably connected with a proximal end of the locking body (<NUM>), and a far end of the push inner tube (<NUM>) is inserted into or is in sleeving fit with a proximal end of the locking plug (<NUM>); and both the locking body and the locking plug are located in the outer tube (<NUM>) before the locking body is released.