Extensible intramedullary nail

Abstract

The application provides a prolongable intramedullary nail, and relates to the technical field of medical devices. The prolongable intramedullary nail comprises a mother needle, a child needle shell and a child needle core; the child needle core is inserted into the child needle shell, and the child needle shell is slidably inserted into the mother needle; the proximal end of the child needle core is connected with the child needle shell through a connecting piece; the distal end of the child needle shell is provided with a child needle distal end which is threadedly connected with the patient's bone, and the child needle distal end is provided with a hollow nail, the axis of the hollow nail is perpendicular to the axis of the child needle shell, and the child needle distal end is provided with a transmission assembly for pushing the hollow nail out of the child needle distal end, and the child needle core is in transmission connection with the transmission assembly. The technical effect of good use effect is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medical devices, in particular to an extendable intramedullary nail. BACKGROUND

[0002] The extendable intramedullary nail system is a commonly used internal fixation system for correcting lower limb deformities in children at present, and is mainly applied to lower limb deformities in children caused by osteogenesis imperfecta, sequelae of rickets, congenital tibial pseudoarthrosis and the like. The commonly used extendable intramedullary nail system at present is the Fassier-Duval system, the distal end of the child nail of which is designed to be driven into the epiphysis, and the distal end of the child nail is fixed in the epiphysis by using the mutual embedding and friction force of the thread and the epiphysis, so that the child nail moves to the distal end along with the growth of the growth plate, the overlapping part of the child nail and the parent nail is reconstructed and reduced, and thus the entire femur or tibia is maintained stable by internal fixation. However, in the clinical practice and literature reports, the child nail still appears to be loose in some cases (13%), and moves to the proximal end along with the growth of the growth plate. Especially when the tibial deformity correction is applied to children of a smaller age, because the space of the distal epiphysis is smaller, part of the thread at the distal end of the child nail remains in the growth plate or even the metaphysis, which significantly weakens the control force of the epiphysis on the child nail, and the possibility of proximal migration of the child nail is significantly increased.

[0003] Other extendable intramedullary nail internal fixation systems mainly include the Sheffield system and the Dyna locking system. The distal end of the child nail of the Sheffield system is a fixed T-shaped structure, and the distal joint needs to be opened during the operation to install and remove the T-shaped structure at the distal end of the child nail, thereby causing damage to the articular cartilage. The Dyna locking system needs to drive a Kirschner wire into the distal epiphysis to pass through the hole at the distal end of the child nail to fix the child nail. The Kirschner wire may be withdrawn or loose, and the Kirschner wire may pass through the growth plate and enter the metaphysis. The possible reasons include that the smooth Kirschner wire does not have enough holding force on the cancellous bone of the epiphysis, and the relative positions of the nail hole and the Kirschner wire at the distal end of the nail change during the growth of the bone, which is easy to cause relative sliding and thus lead to the withdrawal or proximal cutting of the Kirschner wire into the metaphysis.

[0004] The commonly used extendable intramedullary nail fixation systems all have the problem of fixing the distal end of the child nail.

[0005] Therefore, it is an important technical problem for those skilled in the art to provide an extendable intramedullary nail with good use effect. SUMMARY

[0006] The present application aims to provide an extendable intramedullary nail to alleviate the technical problem of poor use effect in the prior art.

[0007] In a first aspect, an embodiment of the present application provides an extendable intramedullary nail, comprising a parent nail, a child nail shell and a child nail core.

[0008] The sub-needle needle core is inserted into the sub-needle shell, and the sub-needle shell is slidingly inserted into the female needle;

[0009] The proximal end of the sub-needle needle core is connected to the sub-needle shell through a connecting piece;

[0010] The distal end of the sub-needle shell is provided with a sub-needle distal end which is threadedly connected to the patient's bone, and a hollow nail is arranged in the sub-needle distal end, and the axis of the hollow nail is perpendicular to the axis of the sub-needle shell;

[0011] A transmission assembly is arranged in the sub-needle distal end for pushing the hollow nail out of the sub-needle distal end, and the sub-needle needle core is in transmission connection with the transmission assembly.

[0012] In combination with the first aspect, the embodiments of the present application provide a possible implementation manner of the first aspect, wherein the connecting piece is a trapezoidal top hat, the upper end of the connecting piece is threadedly connected to the sub-needle shell, and the lower end of the connecting piece is threadedly connected to the sub-needle needle core.

[0013] In combination with the first aspect, the embodiments of the present application provide a possible implementation manner of the first aspect, wherein the distal end of the sub-needle shell is provided with a clamping piece, a clamping groove is formed in the outer wall of the sub-needle needle core and is matched with the clamping piece, and when the sub-needle needle core is connected to the sub-needle shell through the connecting piece, the clamping groove is located above the clamping piece.

[0014] In combination with the first aspect, the embodiments of the present application provide a possible implementation manner of the first aspect, wherein the clamping groove is a ring groove.

[0015] The clamping piece comprises a steel ball and a spring, a recess for containing the spring is formed in the sub-needle shell, and the steel ball abuts against the spring.

[0016] In combination with the first aspect, the embodiments of the present application provide a possible implementation manner of the first aspect, wherein the transmission assembly comprises a passive bevel gear, a transmission shaft, a driving transmission tooth and a passive transmission tooth.

[0017] The distal end of the sub-needle needle core is provided with a driving bevel gear which can mesh with the passive bevel gear.

[0018] The transmission shaft is inserted into the passive bevel gear, the axis of the transmission shaft coincides with the axis of the passive bevel gear, and the transmission shaft rotates synchronously with the passive bevel gear.

[0019] The driving transmission tooth is inserted into the transmission shaft, the axis of the driving transmission tooth coincides with the axis of the transmission shaft, and the driving transmission tooth rotates synchronously with the transmission shaft.

[0020] The main drive tooth is engaged with the passive drive tooth, the hollow nail is slidingly inserted on the passive drive tooth, and the pointed end of the hollow nail is threadedly connected with the sub-needle shell.

[0021] In combination with the first aspect, the embodiments of the present application provide a possible implementation manner of the first aspect, wherein the outer wall of the hollow nail is provided with a guide strip, and the extension direction of the guide strip is parallel to the axis of the hollow nail.

[0022] The passive drive tooth is provided with a notch adapted to the guide strip.

[0023] In combination with the first aspect, the embodiments of the present application provide a possible implementation manner of the first aspect, wherein the passive drive tooth comprises a first drive tooth and a second drive tooth, and the number of the hollow nails is two, which are a first hollow nail and a second hollow nail.

[0024] The first drive tooth and the second drive tooth are both arranged in the distal end of the sub-needle, the first drive tooth is engaged with the main drive tooth, and the second drive tooth is engaged with the first drive tooth.

[0025] The first hollow nail is slidingly inserted in the first drive tooth, and the second hollow nail is slidingly inserted in the second drive tooth.

[0026] In combination with the first aspect, the embodiments of the present application provide a possible implementation manner of the first aspect, wherein the proximal end of the sub-needle needle core is provided with an internal hexagonal groove.

[0027] In combination with the first aspect, the embodiments of the present application provide a possible implementation manner of the first aspect, wherein the distal end of the sub-needle is provided with an external thread.

[0028] In combination with the first aspect, the embodiments of the present application provide a possible implementation manner of the first aspect, wherein the proximal end of the sub-needle needle core is provided with an indication mark for indicating the pointing direction of the hollow nail.

[0029] Beneficial effects:

[0030] The embodiments of the present application provide an extendable intramedullary nail, which comprises a mother needle, a sub-needle shell and a sub-needle needle core; the sub-needle needle core is inserted in the sub-needle shell, the sub-needle shell is slidingly inserted in the mother needle; the proximal end of the sub-needle needle core is connectable with the sub-needle shell through a connecting piece; the distal end of the sub-needle shell is provided with a sub-needle distal end threadedly connected with the patient's bone, the sub-needle distal end is provided with a hollow nail, and the axis of the hollow nail is perpendicular to the axis of the sub-needle shell; the sub-needle distal end is provided with a drive assembly for pushing the hollow nail out of the sub-needle distal end, and the sub-needle needle core is drivingly connected with the drive assembly.

[0031] In specific use, the medical staff first inserts the sub-needle core into the sub-needle shell, then connects the sub-needle shell and the sub-needle core through the connecting piece, drives the sub-needle shell into the patient's long bone epiphysis, and passes through the growth plate into the epiphysis, then the medical staff removes the connecting piece, so that the sub-needle core moves towards the distal end of the sub-needle, so that the sub-needle core can push the hollow nail in the distal end of the sub-needle, so that the hollow nail is connected with the epiphysis of the patient, thereby fixing the distal end of the sub-needle, avoiding the sub-needle from cutting into the epiphysis or cutting into the epiphysis, then selecting a suitable length of the mother needle to insert and wrap the sub-needle shell, and the proximal end of the mother needle is screwed into and fixed to the proximal end of the bone. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0033] Figure 1 The schematic diagram of the extendable intramedullary nail provided by the embodiment of the present application;

[0034] Figure 2 The principle diagram of the transmission assembly in the extendable intramedullary nail provided by the embodiment of the present application;

[0035] Figure 3 The top view of the extendable intramedullary nail provided by the embodiment of the present application (in which the connecting piece is not shown).

[0036] FIG.

[0037] 100 - mother needle;

[0038] 200 - sub-needle shell; 210 - connecting piece; 220 - clamping piece;

[0039] 300 - sub-needle core; 310 - clamping groove; 320 - driving bevel gear; 330 - indicating mark;

[0040] 400 - distal end of sub-needle;

[0041] 500 - hollow nail;

[0042] 600 - transmission assembly; 610 - driven bevel gear; 620 - transmission shaft; 630 - driving transmission tooth; 640 - first transmission tooth; 650 - second transmission tooth. DETAILED DESCRIPTION

[0043] The technical solutions of the present application will be described clearly and completely in the following description of the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0044] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0045] In addition, the terms "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features referred to. Therefore, the features defined with "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0046] In the present application, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0047] The present application will be described in further detail below through specific embodiments and in conjunction with the drawings.

[0048] Reference is made to Figure 1 , Figure 2 and Figure 3As shown in the drawings, the embodiment of the present application provides an intramedullary nail which can be extended, comprising a mother needle 100, a child needle shell 200 and a child needle core 300; the child needle core 300 is inserted into the child needle shell 200, and the child needle shell 200 is slidingly inserted into the mother needle 100; the proximal end of the child needle core 300 is connected with the child needle shell 200 through a connecting piece 210; the distal end of the child needle shell 200 is provided with a child needle distal end 400 which is threadedly connected with the patient's bone, and the child needle distal end 400 is provided with a hollow nail 500, and the axis of the hollow nail 500 is perpendicular to the axis of the child needle shell 200; the child needle distal end 400 is provided with a transmission assembly 600 for pushing the hollow nail 500 out of the child needle distal end 400, and the child needle core 300 is drivingly connected with the transmission assembly 600.

[0049] In specific use, the medical staff first inserts the child needle core 300 into the child needle shell 200, and then connects the child needle shell 200 and the child needle core 300 through the connecting piece 210, drives the child needle shell 200 into the metaphysis of the patient's long bone, and penetrates the growth plate into the epiphysis, and then the medical staff removes the connecting piece 210, so that the child needle core 300 moves towards the child needle distal end 400, so that the child needle core 300 can push the hollow nail 500 in the child needle distal end 400 out, so that the hollow nail 500 is connected with the patient's epiphysis, thereby fixing the child needle distal end 400, avoiding the child needle from being cut off or cutting into the metaphysis, and then selecting a mother needle 100 with a proper length to insert and wrap the child needle shell 200, and the proximal end of the mother needle 100 is screwed into and fixed to the proximal end of the bone.

[0050] As shown in the drawings, Figure 1 , Figure 2 and Figure 3 , in the alternative embodiment of the present application, the connecting piece 210 adopts a trapezoidal top hat, the upper end of the connecting piece 210 is threadedly connected with the child needle shell 200, and the lower end of the connecting piece 210 is threadedly connected with the child needle core 300.

[0051] Specifically, through the arrangement of the connecting piece 210, the child needle core 300 can be fixed relative to the child needle shell 200, so as to move synchronously with the child needle shell 200.

[0052] As shown in the drawings, Figure 1 , Figure 2 and Figure 3 , in the alternative embodiment of the present application, the distal end of the child needle shell 200 is provided with a clamping piece 220, and the outer wall of the child needle core 300 is provided with a clamping groove 310 matched with the clamping piece 220, and when the child needle core 300 is connected with the child needle shell 200 through the connecting piece 210, the clamping groove 310 is located above the clamping piece 220.

[0053] Specifically, the connecting piece 210 is provided with an internal hexagonal groove, and medical staff can drive the sub-needle shell 200 to rotate through the internal hexagonal groove on the connecting piece 210, so that the sub-needle distal end 400 of the sub-needle shell 200 can be screwed into the patient's bone. Then the medical staff removes the connecting piece 210, so that the sub-needle core 300 can move towards the sub-needle distal end 400, so that the clamping groove 310 on the outer wall of the sub-needle core 300 is clamped with the clamping piece 220 arranged at the distal end of the inner wall of the sub-needle shell 200, thereby bearing the sub-needle core 300, so that the sub-needle core 300 can drive the transmission assembly 600, thereby extending or retracting the hollow nail in the sub-needle distal end 400.

[0054] Referring to Figure 1 , Figure 2 and Figure 3 , in an optional solution of the embodiment, the clamping groove 310 is a ring groove; the clamping piece 220 includes a steel ball and a spring, and the sub-needle shell 200 is provided with a groove for containing the spring, and the steel ball abuts against the spring.

[0055] Specifically, the clamping piece 220 adopts a spring and a steel ball, so that when the medical staff removes the connecting piece 210, the steel ball on the inner wall of the sub-needle shell 200 will be clamped into the clamping groove 310 on the outer wall of the sub-needle core 300 during the movement of the sub-needle core 300 towards the sub-needle distal end 400, thereby supporting the sub-needle core 300 and ensuring that the sub-needle core 300 can freely rotate.

[0056] Referring to Figure 1 , Figure 2 and Figure 3 , in an optional solution of the embodiment, the transmission assembly 600 includes a passive bevel gear 610, a transmission shaft 620, a driving transmission tooth 630 and a passive transmission tooth; the distal end of the sub-needle core 300 is provided with a driving bevel gear 320 capable of meshing with the passive bevel gear 610; the transmission shaft 620 is inserted on the passive bevel gear 610, the axis of the transmission shaft 620 coincides with the axis of the passive bevel gear 610, and the transmission shaft 620 rotates synchronously with the passive bevel gear 610; the driving transmission tooth 630 is inserted on the transmission shaft 620, the axis of the driving transmission tooth 630 coincides with the axis of the transmission shaft 620, and the driving transmission tooth 630 rotates synchronously with the transmission shaft 620; the driving transmission tooth 630 meshes with the passive transmission tooth, the hollow nail 500 is slidably inserted on the passive transmission tooth, and the pointed end of the hollow nail 500 is threadedly connected with the sub-needle shell 200.

[0057] Specifically, the proximal end of the sub-needle needle core 300 is provided with an internal hexagonal groove. Medical staff can rotate the sub-needle needle core 300 through a tool, so that the sub-needle needle core 300 can be rotated, the rotation of the sub-needle needle core 300 drives the driving bevel gear 320 to rotate, the rotation of the driving bevel gear 320 drives the driven bevel gear 610 to rotate, thereby driving the transmission shaft 620 inserted on the driven bevel gear 610 to rotate, the rotation of the transmission shaft 620 can drive the driving transmission teeth 630 to rotate, the rotation of the driving transmission teeth 630 can drive the driven transmission teeth to rotate, thereby driving the hollow nail 500 inserted on the driven transmission teeth to rotate, and the pointed end of the hollow nail 500 is screwed with the sub-needle shell 200, so that when the driven transmission teeth rotate, the hollow nail 500 can be driven to rotate, and through the screw connection between the hollow nail 500 and the sub-needle shell 200, the hollow nail 500 can be rotated and extended out of the sub-needle shell 200, so that the hollow needle is rotated into the patient's bone.

[0058] Referring to Figure 1 , Figure 2 and Figure 3 , in an optional solution of the embodiment, the outer wall of the hollow nail 500 is provided with a guide strip, the extension direction of the guide strip is parallel to the axis of the hollow nail 500; the driven transmission teeth are provided with a notch matched with the guide strip.

[0059] Specifically, the guide strip is arranged on the outer wall of the hollow nail 500, the driven transmission teeth drive the hollow nail 500 to rotate synchronously through the guide strip, and when the hollow nail 500 rotates with the driven transmission teeth, the hollow nail 500 can be screwed with the sub-needle shell 200 to rotate, so that the hollow needle moves out of the sub-needle shell 200.

[0060] Referring to Figure 1 , Figure 2 and Figure 3 , in an optional solution of the embodiment, the driven transmission teeth include a first transmission tooth 640 and a second transmission tooth 650, the number of the hollow nails 500 is two, which are a first hollow nail 500 and a second hollow nail 500; the first transmission tooth 640 and the second transmission tooth 650 are arranged in the sub-needle distal end 400, the first transmission tooth 640 is engaged with the driving transmission teeth 630, and the second transmission tooth 650 is engaged with the first transmission tooth 640; the first hollow nail 500 is slidingly inserted in the first transmission tooth 640, and the second hollow nail 500 is slidingly inserted in the second transmission tooth 650.

[0061] Specifically, through the arrangement of the first transmission tooth 640 and the second transmission tooth 650, the first transmission tooth 640 is engaged with the driving transmission teeth 630, and the second transmission tooth 650 is engaged with the first transmission tooth 640, so that the driving transmission teeth 630 can drive the first transmission tooth 640 to rotate, and the first transmission tooth 640 drives the second transmission tooth 650 to rotate.

[0062] The first transmission tooth 640 is fixed in the distal end 400 of the needle by a bearing which abuts the outer wall of the first transmission tooth 640.

[0063] Referring to Figs. Figure 1 , Figure 2 and Figure 3 , in an alternative embodiment of the present application, the distal end 400 of the needle is provided with external threads.

[0064] Specifically, the distal end 400 of the needle is provided with external threads so that the distal end 400 of the needle can be screwed into the bone of the patient.

[0065] Referring to Figs. Figure 1 , Figure 2 and Figure 3 Figure 1 Figure 2 Figure 3 , in an alternative embodiment of the present application, the proximal end of the needle core 300 is provided with an indicator 330 for indicating the pointing direction of the hollow nail 500.

[0066] Specifically, after the medical staff screws the distal end 400 of the needle shell 200 into the bone of the patient, the medical staff can know the pointing direction of the hollow nail 500 by observing the pointing direction of the indicator 330, so as to confirm whether the needle core 300 can be rotated to drive the hollow nail 500 to extend out of the distal end 400 of the needle.

[0067] In the initial position, i.e. when the medical staff does not rotate the needle core 300 alone, the direction indicated by the indicator 330 at the end of the needle core 300 is parallel to the indicating direction of the hollow nail 500.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features thereof; and such modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An extendable intramedullary nail, characterized in that, include: Mother needle (100), daughter needle outer shell (200) and daughter needle core (300); The sub-needle core (300) is inserted into the sub-needle housing (200), and the sub-needle housing (200) is slidably inserted into the main needle (100); The proximal end of the sub-needle core (300) can be connected to the sub-needle housing (200) via a connector (210); The distal end of the sub-needle housing (200) is provided with a sub-needle distal end (400) that is threadedly connected to the patient's bone. A hollow nail (500) is provided inside the sub-needle distal end (400), and the axis of the hollow nail (500) is perpendicular to the axis of the sub-needle housing (200). The distal end (400) of the sub-needle is provided with a transmission assembly (600) for pushing the hollow nail (500) out of the distal end (400) of the sub-needle, and the sub-needle core (300) is connected to the transmission assembly (600) in a transmission connection. The transmission assembly (600) includes a passive bevel gear (610), a transmission shaft (620), a driving transmission gear (630), and a passive transmission gear; The distal end of the sub-needle core (300) is provided with an active bevel gear (320) that can mesh with the passive bevel gear (610). The drive shaft (620) is inserted on the driven bevel gear (610), the axis of the drive shaft (620) coincides with the axis of the driven bevel gear (610), and the drive shaft (620) rotates synchronously with the driven bevel gear (610). The active transmission gear (630) is inserted on the transmission shaft (620), the axis of the active transmission gear (630) coincides with the axis of the transmission shaft (620), and the active transmission gear (630) rotates synchronously with the transmission shaft (620). The active transmission tooth (630) meshes with the passive transmission tooth, the hollow pin (500) is slidably inserted on the passive transmission tooth, and the pointed end of the hollow pin (500) is threadedly connected to the sub-pin housing (200). The connector (210) adopts a trapezoidal top cap. The upper end of the connector (210) is threaded to the sub-needle housing (200), and the lower end of the connector (210) is threaded to the sub-needle core (300). The distal end of the sub-needle housing (200) is provided with a retainer (220), and the outer wall of the sub-needle core (300) is provided with a slot (310) that is adapted to the retainer (220). When the sub-needle core (300) is connected to the sub-needle housing (200) through the connector (210), the slot (310) is located above the retainer (220).

2. The extendable intramedullary nail according to claim 1, characterized in that, The slot (310) is an annular groove; The clip (220) includes a steel ball and a spring. The outer shell (200) of the sub-needle has a groove for holding the spring, and the steel ball abuts against the spring.

3. The extendable intramedullary nail according to claim 1, characterized in that, The hollow nail (500) has a guide strip on its outer wall, and the extension direction of the guide strip is parallel to the axis of the hollow nail (500). The passive transmission gear has a notch that matches the guide bar.

4. The extendable intramedullary nail according to claim 3, characterized in that, The passive transmission gear includes a first transmission gear (640) and a second transmission gear (650), and there are two hollow pins (500), namely a first hollow pin (500) and a second hollow pin (500). The first transmission tooth (640) and the second transmission tooth (650) are both disposed in the distal end (400) of the sub-needle. The first transmission tooth (640) meshes with the active transmission tooth (630), and the second transmission tooth (650) meshes with the first transmission tooth (640). The first hollow nail (500) is slidably inserted into the first transmission tooth (640), and the second hollow nail (500) is slidably inserted into the second transmission tooth (650).

5. The extendable intramedullary nail according to any one of claims 1-4, characterized in that, The proximal end of the sub-needle core (300) is provided with an internal hexagonal groove.

6. The extendable intramedullary nail according to any one of claims 1-4, characterized in that, The distal end (400) of the sub-needle is provided with an external thread.

7. The extendable intramedullary nail according to any one of claims 1-4, characterized in that, The proximal end of the sub-needle core (300) is provided with an indicator (330) for indicating the direction of the hollow nail (500).

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