Fracture fixing device

Abstract

The utility model relates to the technical field of medical accessories, in particular to a fracture fixing device. A fracture fixing device comprises a long-strip-shaped bone fracture plate, and a plurality of connecting holes are formed in the bone fracture plate in the length direction of the bone fracture plate. A first connecting part is arranged at one end of the auxiliary plate; a first connecting piece is further included, and the first connecting part is detachably connected with one of the connecting holes selectively through the first connecting piece; a second connecting part is arranged at the other end of the auxiliary plate, and the second connecting part can be detachably connected with the bone tissue of the patient through the second connecting piece; the extension length of the auxiliary plate is shorter than that of the bone fracture plate in the length extension direction of the bone fracture plate, and the extension length of the auxiliary plate is configured to be a preset length. The fracture fixing device solves the technical problem in the prior art, and the fracture fixing device is urgently needed, can reduce the wound area of a patient in the comminuted fracture operation process, and meanwhile has a reliable fixing function.

Description

Technical Field

[0001] The utility model relates to the technical field of medical accessories, in particular to a fracture fixing device. Background Art

[0002] In surgical fracture surgery, comminuted fractures are a more serious type of fracture. The fracture site will break into three or more pieces, and the broken bones are difficult to reposition and fix during surgery. The following are the general fixation methods:

[0003] Two bone plates are used to be distributed on the upper and lower sides or the left and right sides of the bone tissue, and any one of the bone plates should respectively cover the comminuted fractured bone tissue part and the non-fractured bone tissue part adjacent to the comminuted fractured bone tissue part, and a plurality of bone holes are drilled on the fractured bone tissue and the non-fractured bone tissue respectively, and screw holes are provided on the bone plates, and screws are used to thread the screw holes on the bone plates with the bone holes on the bone tissue, so that the fractured bone tissue and the non-fractured bone tissue are connected through the bone plates; that is, in the prior art, two bone plates are required to connect and fix the fractured bone tissue and the non-fractured bone tissue.

[0004] However, since the bone plate is a long strip-shaped plate structure with a length of L, which is usually about tens of millimeters, during the operation, the doctor needs to cut a wound with a length of L in the skin tissue corresponding to the upper and lower sides, or the left and right sides of the patient's bone tissue, and then implant the two bone plates into the upper and lower sides, or the left and right sides of the bone tissue respectively, which undoubtedly increases the patient's surgical trauma; and if only one bone plate is used to fix the fractured bone tissue, the fractured bone tissue and the non-fractured bone tissue are only connected through the bone plate on one side, which may easily lead to unstable fixation, and the fractured bone tissue may easily fall off during the patient's walking or postoperative recovery process; and in order to avoid this situation, the number of bone holes drilled in the bone tissue is usually increased, and more fasteners are used to establish a detachable connection between the bone plate and the bone tissue, which will cause greater destructiveness to the bone tissue and easily cause the already fractured and broken bone tissue to further break.

[0005] In summary, the technical problem existing in the prior art is that it is urgent to propose a fracture fixation device that can reduce the size of the patient's skin trauma during comminuted fracture surgery and also has a reliable fixation effect. Utility Model Content

[0006] In view of the existing technology, it is urgently necessary to propose a technical problem of a fracture fixation device, which can reduce the size of the patient's skin trauma during comminuted fracture surgery and also has a reliable fixation effect.

[0007] The utility model is realized by the following technical solutions:

[0008] A fracture fixation device comprises a long strip-shaped bone fracture plate, on which a plurality of connection holes are arranged along the length direction thereof;

[0009] It also includes an auxiliary plate, one end of which is provided with a first connecting portion; it also includes a first connecting member, the first connecting portion can be selectively detachably connected to one of the connecting holes through the first connecting member;

[0010] The other end of the auxiliary plate is provided with a second connection portion, and also includes a second connection member, and the second connection portion can be detachably connected to the patient's bone tissue through the second connection member;

[0011] Along the length extension direction of the bone fracture plate, the extension length of the auxiliary plate is shorter than the extension length of the bone fracture plate, and the extension length of the auxiliary plate is configured as a preset length.

[0012] Further, the second connecting portion includes a body;

[0013] A through channel is arranged on the main body along the axial direction, and a limited position surface is arranged on the inner wall of a section of the through channel along the axial direction of the through channel;

[0014] The second connecting member includes a rod and a head, the rod penetrates the through-channel, the head points to the direction of the rod, and the head is restricted in the through-channel by a limiting surface and cannot be separated; and the circumferential outer surface of the head is arc-shaped or spherical, and the limiting surface is an arc-shaped or spherical shape matching the circumferential outer surface of the head; the circumferential outer surface of the head is rotatably in contact with the limiting surface;

[0015] Another section of the inner wall of the through-channel is also provided with an internal thread, and the second connecting part also includes a nut, the outer surface of the nut is provided with an external thread, and the nut is threadedly connected to the inner wall of the through-channel; along the axial direction of the nut, one end of the nut is provided with an extrusion surface, and the extrusion surface can be in close contact with the circumferential outer surface of the head.

[0016] Furthermore, the extrusion surface is an arc-shaped surface. When the axis of the head forms an angle with the axis of the through-channel and the extrusion surface is in close contact with the head, the extrusion surface and the circumferential outer surface of the head have multiple contact positions.

[0017] Furthermore, the auxiliary plate also includes a first bending portion, which is arranged between the first connecting portion and the second connecting portion, and the first bending portion is made of a plastically deformable material.

[0018] Furthermore, there are a plurality of second connection parts, and a second bending part is provided between any two adjacent second connection parts, and the second bending part is made of a plastically deformable material.

[0019] Furthermore, the auxiliary plate is a thin plate structure, and its thickness is processed to a preset thickness.

[0020] Furthermore, at least one Kirschner wire through hole is provided on the auxiliary plate.

[0021] Furthermore, the connecting hole includes a first threaded hole and a first through hole, and a hole center line of the first threaded hole and a hole center line of the first through hole are parallel to each other.

[0022] Furthermore, the nut is provided with a first channel, and the cross section of the first channel is a hexagonal inner corner; the first channel penetrates the nut along the axial direction of the nut.

[0023] Furthermore, a guide surface is provided at the edge of the through-channel along the axial direction of the through-channel; the internal thread is located between the guide surface and the limit surface along the axial direction of the through-channel; and the guide surface is convergent in the direction from the internal thread to the limit surface.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] 1. In the present invention, a bone plate, an auxiliary plate, and screws respectively matched with the bone plate and the auxiliary plate can be used to fix the bone tissue at the comminuted fracture site and the bone tissue at the non-fracture site; in the present invention, a wound with a length of L is cut on the patient's skin, the bone plate is implanted, and then a small window with a preset length is cut on the patient's skin, and the auxiliary plate is implanted, and along the length extension direction of the bone plate, the preset length is much smaller than the length L, that is, in the present invention, there is no need to cut wounds with a length of L on the skin of both sides of the patient to complete the fixation of the fracture site as in the prior art, and only a wound with a length of L is cut on the patient's skin, and then a small window with a preset length is cut to complete the implantation; at the same time, using the present invention Although the fracture fixation device of the utility model adopts an auxiliary plate that is shorter than the bone plate in the prior art and replaces one of the bone plates in the prior art, the first connecting part at one end of the auxiliary plate establishes a firm connection with the bone plate through the first connecting piece, and the second connecting part at the other end of the auxiliary plate establishes a firm connection with the bone tissue at the patient's fracture site through the second connecting piece. During the patient's postoperative rehabilitation and activities, the connection between the patient's bone tissue at the fracture site and the bone plate established by the auxiliary plate is still reliable. In summary, the utility model solves the technical problems existing in the prior art: there is an urgent need to propose a fracture fixation device that can reduce the patient's trauma area during comminuted fracture surgery and also has a reliable fixation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the fracture fixation device of the utility model;

[0027] Figure 2 for Figure 1 Schematic diagram of the enlarged structure of the A area in the middle;

[0028] Figure 3 is a structural schematic diagram of the second connecting portion;

[0029] Figure 4 is a cross-sectional schematic diagram of the body;

[0030] Figure 5 It is a schematic diagram of the matching between the body and the nut.

[0031] Markings in the figure: bone plate (1), connecting hole (101), first threaded hole (102), first through hole (103)

[0032] An auxiliary plate (2), a first connecting portion (201), a second connecting portion (202), a main body (203), a through channel (204), a limiting surface (205), an internal thread (206), a nut (207), an extrusion surface (208), a first bending portion (209), a second bending portion (210), a Kirschner wire through hole (211), and a guide surface (212). DETAILED DESCRIPTION

[0033] The following is a further non-restrictive detailed description of the utility model technical solution in conjunction with the preferred embodiment and its accompanying drawings. In the description of the utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or position relationship based on the orientation or position relationship shown in the accompanying drawings. In addition, the terms "first" and "second" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the utility model, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the utility model, and cannot be understood as limitations on the utility model.

[0034] Example 1

[0035] like Figure 1-2As shown, a fracture fixation device includes a long strip of bone fracture plate 1, on which a plurality of connecting holes 101 are arranged along the length direction thereof; further includes an auxiliary plate 2, on one end of which a first connecting portion 201 is arranged; further includes a first connecting member, and the first connecting portion 201 can be selectively detachably connected to one of the connecting holes 101 through the first connecting member; a second connecting portion 202 is arranged at the other end of the auxiliary plate 2, and further includes a second connecting member, and the second connecting portion 202 can be detachably connected to the patient's bone tissue through the second connecting member; along the length extension direction of the bone fracture plate 1, the extension length of the auxiliary plate 2 is shorter than the extension length of the bone fracture plate 1, and the extension length of the auxiliary plate 2 is configured to be a preset length.

[0036] Combination Figure 1-2 As shown, the bone plate 1 is a long strip-shaped plate structure. In this embodiment, the length of the bone plate 1 is L. The designer has a plurality of connecting holes 101 on the bone plate 1. In this embodiment, the connecting hole 101 includes a first threaded hole 102 and a first through hole 103. The center line of the first threaded hole 102 is parallel to the center line of the first through hole 103. The purpose of this arrangement is that the connecting hole 101 can be threadedly connected to a screw with a thread through the first threaded hole 102, and can also be connected to a fixing pin without a thread through the first through hole 103 by interference fit, so as to achieve the purpose of matching different connecting parts.

[0037] The first connection part 201 at one end of the auxiliary plate 2 can be detachably connected to the bone plate 1 through a first connection piece, and the second connection part 202 at the other end can be detachably connected to the bone tissue at the fracture site of the patient through a second connection piece, that is, the auxiliary plate 2 plays a role in establishing a connection relationship between the bone tissue at the fracture site of the patient and the bone plate 1; at the same time, along the length extension direction of the bone plate 1, the extension length of the auxiliary plate 2 is shorter than the extension length of the bone plate 1, and the extension length of the auxiliary plate 2 is configured as a preset length. In this embodiment, the preset length is much smaller than L, and the specific value of the preset length is not limited.

[0038] The first connecting member and the second connecting member may be one of the connecting members in the prior art, such as a screw or a bolt; preferably, in the present embodiment, the first connecting member and the second connecting member are both screws.

[0039] When in use, first, a wound with a length of L is cut longitudinally on the patient's skin, and a bone plate 1 is placed along the extension direction of the patient's bone tissue. The bone plate 1 needs to cover the bone tissue part of the comminuted fracture and the non-fractured bone tissue part adjacent to the comminuted fractured bone tissue part respectively, and the bone plate 1 and the bone hole on the non-fractured bone tissue are fixed to each other by screws; then, a small window with a preset length is cut on the side of the patient's skin, and the auxiliary plate 2 is implanted through the small window, and the first connecting part 201 of the auxiliary plate 2 is detachably connected to one of the connecting holes 101 of the bone plate 1 through a first connecting piece, and the second connecting part 202 of the auxiliary plate 2 is detachably connected to the bone hole on the fractured bone tissue through a second connecting piece; the number of auxiliary plates 2 can be one or two, depending on the specific fracture situation. Usually, a maximum of two auxiliary plates 2 are used to achieve the purpose of firm fixation.

[0040] As can be seen from the background technology, in the prior art, the bone tissue at the comminuted fracture site can only be fixed by using two bone plates and screws matching the bone plates; the technical problem existing in the prior art is that it is urgent to propose a fracture fixation device that can reduce the patient's trauma area during comminuted fracture surgery and at the same time has a reliable fixation effect.

[0041] In this embodiment, a bone plate, an auxiliary plate, and screws respectively matched with the bone plate and the auxiliary plate can be used to fix the bone tissue at the comminuted fracture site and the non-fractured bone tissue; in this embodiment, a wound with a length of L is cut on the patient's skin, the bone plate is implanted, and then a small window with a preset length is cut on the patient's skin, and the auxiliary plate is implanted, and along the length extension direction of the bone plate, the preset length is much smaller than the length L, that is, in this embodiment, there is no need to cut wounds with a length of L on the skin of both sides of the patient to complete the fixation of the fracture as in the prior art, only a wound with a length of L is cut on the patient's skin, and then a small window with a preset length is cut to complete the implantation process; at the same time, the fracture of the present embodiment can be fixed by cutting a wound with a length of L on the patient's skin. Although the fixation device adopts an auxiliary plate that is shorter than the bone plate in the prior art and replaces one of the bone plates in the prior art, the first connection part 201 at one end of the auxiliary plate 2 establishes a firm connection relationship with the bone plate 1 through the first connection piece, and the second connection part 202 at the other end of the auxiliary plate 2 establishes a firm connection relationship with the bone tissue at the patient's fracture site through the second connection piece. During the patient's postoperative rehabilitation and activities, the connection relationship established between the patient's bone tissue at the fracture site and the bone plate 1 by the auxiliary plate 2 is still reliable. In summary, this embodiment solves the technical problems existing in the prior art: it is urgently necessary to propose a fracture fixation device, which can reduce the patient's trauma area during comminuted fracture surgery and also has a reliable fixation effect.

[0042] Furthermore, in actual surgical operations, it is easy to encounter that after the first connecting part 201 at one end of the auxiliary plate 2 establishes a connection relationship with the bone plate 1 through the first connecting piece, the auxiliary plate 2 is attached to the bone tissue, and before the second connecting part needs to establish a connection with the bone hole at the fracture through the second connecting piece, the hole center line of the second connecting piece is not aligned with the hole center line of the bone hole at the fracture, that is, the situation of non-overlap occurs. Generally, there is an angle between the hole center line of the second connecting piece and the hole center line of the corresponding bone hole at the fracture. This will result in the second connecting piece being unable to be inserted into the bone hole corresponding to the second connecting piece without adjusting the position of the auxiliary plate 2; if the angle between the second connecting piece and the second connecting part 202 is adjustable and can be fixed after adjustment, then during the operation, the second connecting piece can be rotated relative to the second connecting part so that the hole center line of the second connecting piece and the hole center line of the corresponding bone hole coincide with each other; therefore, how to make the angle between the second connecting piece and the second connecting part 202 adjustable and can be fixed after adjustment is a technical problem that needs to be solved in the next step, and this technical problem is solved by the following technical solution.

[0043] like Figure 3 to Figure 5 As shown, the second connecting part 202 includes a body 203; a through channel 204 is axially arranged on the body 203, and a limited surface 205 is arranged on the inner wall of one section of the through channel 204 along the axial direction of the through channel 204; the second connecting member includes a rod and a head, the rod penetrates the through channel 204, the head points to the direction of the rod, and the head is restricted in the through channel 204 by the limited surface 205 and cannot be separated; and the outer surface of the head is arc-shaped or spherical, and the limited surface 205 is An arc or spherical shape that matches the circumferential outer surface of the head; the circumferential outer surface of the head is rotatably in contact with the limiting surface 205; another section of the inner wall of the through channel 204 is also provided with an internal thread 206, and the second connecting part 202 also includes a nut 207, the outer surface of the nut 207 is provided with an external thread, and the nut 207 is threadedly connected to the inner wall of the through channel 204; along the axial direction of the nut 207, one end of the nut 207 is provided with an extrusion surface 208, and the extrusion surface 208 can be in close contact with the circumferential outer surface of the head.

[0044] Preferably, the extrusion surface 208 is an arc-shaped surface. When the axis of the head forms an angle with the axis of the through-channel 204 and the extrusion surface 208 is in close contact with the head, the extrusion surface 208 and the circumferential outer surface of the head have multiple contact positions to increase the friction between the extrusion surface 208 and the circumferential outer surface of the head.

[0045] In this embodiment, when the extrusion surface 208 of the nut 207 is not in close contact with the circumferential outer surface of the head of the second connector, the circumferential outer surface of the head of the second connector is in sliding contact with the limiting surface 205 of the through-channel 204. When the rotation angle of the second connector meets the surgical requirements, that is, the center line of the hole of the second connector is aligned with the center line of the hole of the bone hole at the fracture site, the nut 207 is screwed in along the axial direction of the nut 207, so that the extrusion surface 208 is tightly pressed against the circumferential outer surface of the head, and the nut 207 and the through-channel 204 are screwed and fixed by threads, and then the friction force of the extrusion surface 208 of the nut 207 on the head of the second connector causes the second connector to be unable to rotate around the axis and unable to be axially disengaged. In this embodiment, along any radial direction of the through-channel 204, the angle between the axis of the second connector and the axis of the through-channel 204 can be adjusted between 0° and 18°. After adjustment, the second connector is fixed in the through-channel 204 by the nut 207 in an inseparable and immovable manner.

[0046] Therefore, this embodiment solves the technical problem of how to make the angle between the second connecting member and the second connecting portion 202 adjustable and fixable after adjustment.

[0047] Furthermore, since the shapes of the bone tissues of different patients are different, how to make the shape of the auxiliary plate 2 adjustable to match the shapes of the bone tissues of different patients is the next technical problem to be solved. This technical problem is solved by the following technical solution.

[0048] The auxiliary plate 2 further includes a first bending portion 209 . The first bending portion 209 is disposed between the first connecting portion 201 and the second connecting portion 202 . The first bending portion 209 is made of a plastically deformable material.

[0049] Furthermore, the number of the second connection parts 202 may be one or more. In the present embodiment, the number of the second connection parts 202 is several, and a second bending part 210 is provided between any two adjacent second connection parts 202. The second bending part 210 is made of a plastically deformable material.

[0050] In this embodiment, the first bending portion 209 is made of a plastically deformable material, such as titanium alloy. During the operation, the shape of the first bending portion 209 can be changed to match the bone tissue structure shape of different patients, which is more convenient. The working principle of the second bending portion 210 is basically the same as that of the first bending portion 209, which will not be elaborated here.

[0051] Furthermore, the present embodiment also includes the following technical solutions: the auxiliary plate 2 is a thin plate structure, and its thickness is processed to a preset thickness. Generally, the preset thickness can be configured according to specific circumstances. For example, in the present embodiment, the preset thickness is 1 to 2 mm. In the present embodiment, the auxiliary plate 2 is made into a thin plate structure, and the thickness of the thin plate structure is relatively thin, which can avoid pulling the skin tissue during the suturing process. At the same time, after suturing, the auxiliary plate 2 will not lift up the skin, causing an obvious bulge on the skin, which is more conducive to the patient's aesthetics.

[0052] Furthermore, at least one Kirschner wire through hole 211 is provided on the auxiliary plate 2. When the auxiliary plate 2 is implanted into the patient's body, the auxiliary plate 2 is first pre-positioned by penetrating the Kirschner wire through hole 211 and the Kirschner wire hole on the patient's bone tissue through the Kirschner wire. Then, the auxiliary plate is fixed using the first connecting member and the second connecting member, which makes surgical operations more convenient for medical staff.

[0053] Preferably, the nut 207 is provided with a first channel, and the cross-section of the first channel is a hexagonal inner corner, which is convenient for medical staff to use a hexagonal inner corner wrench to tighten it; the first channel passes through the nut 207 along the axial direction of the nut 207, which is convenient for medical staff to directly observe the position of the second connecting member through the first channel.

[0054] Furthermore, along the axial direction of the through-channel 204, a guide surface 212 is provided at the edge of the through-channel 204, and along the axial direction of the through-channel 204, the internal thread 206 is located between the guide surface 212 and the limiting surface 205; and the guide surface 212 is convergent from the direction of the limiting surface 205 pointed by the internal thread 206. The provision of the guide surface 212 plays a guiding role in the process of inserting the nut 207 into the through-channel 204.

[0055] The above embodiments only express several implementation methods of the utility model, and the descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, which all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.

Claims

1. A fracture fixation device, characterized in that: It comprises a long strip-shaped bone fracture plate (1), on which a plurality of connection holes (101) are arranged along the length direction thereof; It also includes an auxiliary plate (2), one end of which is provided with a first connection portion (201); it also includes a first connection member, the first connection portion (201) can be selectively connected to one of the connection holes (101) via the first connection member in a detachable manner; The other end of the auxiliary plate (2) is provided with a second connection portion (202), and also includes a second connection piece, and the second connection portion (202) can be detachably connected to the patient's bone tissue through the second connection piece; Along the length extension direction of the bone fracture plate (1), the extension length of the auxiliary plate (2) is shorter than the extension length of the bone fracture plate (1), and the extension length of the auxiliary plate (2) is configured as a preset length.

2. The fracture fixation device according to claim 1, characterized in that: The second connecting portion (202) includes a body (203); A through channel (204) is axially arranged on the body (203), and a limited position surface (205) is arranged on a section of the inner wall of the through channel (204) along the axial direction of the through channel (204); The second connecting member comprises a rod and a head, the rod penetrates the through-channel (204), the head points in the direction of the rod, and the head is inseparably restricted in the through-channel (204) by a limiting surface (205); the circumferential outer surface of the head is arc-shaped or spherical, and the limiting surface (205) is an arc-shaped or spherical shape matching the circumferential outer surface of the head; the circumferential outer surface of the head is rotatably in contact with the limiting surface (205); Another section of the inner wall of the through-channel (204) is also provided with an internal thread (206), and the second connecting portion (202) further includes a nut (207), the outer surface of the nut (207) is provided with an external thread, and the nut (207) is threadedly connected to the inner wall of the through-channel (204); along the axial direction of the nut (207), one end of the nut (207) is provided with an extrusion surface (208), and the extrusion surface (208) can be in close contact with the circumferential outer surface of the head.

3. The fracture fixation device according to claim 2, characterized in that: The extrusion surface (208) is an arc-shaped surface. When the axis of the head and the axis of the through-channel (204) form an angle and the extrusion surface (208) is in close contact with the head, the extrusion surface (208) and the circumferential outer surface of the head have multiple contact positions.

4. The fracture fixation device according to any one of claims 1 to 3, characterized in that: The auxiliary plate (2) further comprises a first bending portion (209), the first bending portion (209) being arranged between the first connecting portion (201) and the second connecting portion (202), and the first bending portion (209) being made of a plastically deformable material.

5. The fracture fixation device according to claim 4, characterized in that: The number of the second connecting parts (202) is plural, and a second bending part (210) is provided between any two adjacent second connecting parts (202), and the second bending part (210) is made of a plastically deformable material.

6. The fracture fixation device according to claim 1, characterized in that: The auxiliary plate (2) is a thin plate structure, and its thickness is processed to a preset thickness.

7. The fracture fixation device according to claim 1, characterized in that: At least one Kirschner wire through hole (211) is also provided on the auxiliary plate (2).

8. The fracture fixation device according to claim 1, characterized in that: The connecting hole (101) comprises a first threaded hole (102) and a first through hole (103), and the hole center line of the first threaded hole (102) and the hole center line of the first through hole (103) are parallel to each other.

9. The fracture fixation device according to claim 2, characterized in that: The nut (207) is provided with a first channel, the cross section of which is a hexagonal inner corner; the first channel penetrates the nut (207) along the axial direction of the nut (207).

10. The fracture fixation device according to claim 2, characterized in that: A guide surface (212) is provided at the edge of the through-channel (204) along the axial direction of the through-channel (204); Along the axial direction of the through channel (204), the internal thread (206) is located between the guide surface (212) and the limit surface (205); and the guide surface (212) is in a convergent shape from the direction of the internal thread (206) pointing to the limit surface (205).

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