CN114767244B - Femoral head hollow screw - Google Patents

Abstract

The present invention relates to the field of medical devices, and in particular, to a hollow femoral head screw. The hollow femoral head screw comprises a main body, a loading part and at least one Kirschner wire; the main body is provided with at least one channel, the channel runs from the proximal end of the main body to the distal end of the main body, and the channel is used to accommodate the Kirschner wire; the loading part is used to drive the Kirschner wire in the channel to move under the action of an external force, so that the Kirschner wire extends out of the channel from the distal end of the main body, and the Kirschner wire extending out of the channel protrudes from the outer peripheral surface of the main body. The hollow femoral head screw can reduce the nail channel formed when fixing the femur, and can thus reduce the damage to the blood vessels in the femoral head.

Description

Femoral head cannulated screw

Technical Field

The invention relates to the field of medical devices, and in particular to a hollow femoral head screw.

Background Art

Femoral neck fracture is a common fracture, among which the proportion of young and middle-aged people is increasing year by year. Young and middle-aged patients have the following characteristics, which lead to a very high incidence of traumatic femoral head necrosis. First, femoral neck fractures in young and middle-aged people are mostly caused by high-energy violent factors, such as car accidents and falls from heights, accompanied by severe damage to surrounding tissues; second, femoral head necrosis is a long and slow process, and young and middle-aged people have a long survival period after fracture and high-intensity activities. Over time, the vast majority of young and middle-aged patients are likely to develop into the stage of femoral head necrosis.

The main cause of femoral head necrosis is the destruction of blood supply, including the damage caused by the fracture itself and iatrogenic damage during treatment. Traditional treatment methods often use three hollow screws arranged in a "pin" shape for internal fixation. Although the fixation strength is achieved, the three screws themselves are huge in size, and the screw channels created during the insertion process cause great damage to the residual vascular network of the femoral head; on the other hand, after a femoral neck fracture, the inserted screws often loosen, which can also lead to complications such as femoral neck shortening.

Summary of the invention

The purpose of the present invention includes, for example, providing a hollow femoral head screw, which can reduce the screw channel formed when fixing the femur, thereby reducing the damage to the blood vessels in the femoral head.

The embodiments of the present invention can be implemented as follows:

The present invention provides a femoral head hollow screw, which comprises a main body, a loading part and at least one Kirschner wire;

The main body is provided with at least one channel, which runs from the proximal end of the main body to the distal end of the main body, and the channel is used to accommodate the Kirschner wire;

The loading component is used to drive the Kirschner wire in the channel to move under the action of external force, so that the Kirschner wire extends out of the channel from the distal end of the main body, and the Kirschner wire extending out of the channel protrudes from the outer peripheral surface of the main body.

In an optional embodiment, the channel includes a first segment and a second segment, and the first segment extends along the axis direction of the main body;

The second segment extends obliquely or curvedly in a direction away from the axis of the main body, and the proximal end of the second segment is connected to the distal end of the first segment, and the distal end of the second segment is located on the outer peripheral surface of the main body;

The second segment is used to guide the Kirschner wire to bend or bend.

In an optional embodiment, the femoral head cannulated screw includes three Kirschner wires;

The main body is provided with three channels, which are arranged in an array on the inner periphery of the main body relative to the axis of the main body, and the three Kirschner wires are matched with the three channels in a one-to-one correspondence.

In an optional embodiment, the loading member includes a loading portion rotatably connected to the main body, and the loading portion is threadedly connected to the Kirschner wire;

The loading part is used to rotate relative to the main body under the action of external force, thereby driving the Kirschner wire to slide relative to the channel.

In an optional embodiment, the loading portion is rotatably connected to the proximal end of the channel to be threadedly connected to a portion of the K-wire located outside the proximal end of the channel.

In an optional embodiment, the outer peripheral surface of the loading portion is provided with a first external thread;

A threaded section for matching with the external thread is provided on one side of the Kirschner wire facing the main body axis, or a second external thread matching with the first external thread is provided on the outer peripheral surface of the Kirschner wire.

In an optional embodiment, the loading member further includes a connecting portion;

The connecting part is threadedly connected to the main body, the connecting part is coaxial with the loading part, and the loading part is rotatably connected to the connecting part.

In an optional embodiment, the connecting portion is threadedly connected to the inner peripheral wall of the main body.

In an optional embodiment, the loading member further includes a first driving rod and a second driving rod;

The first driving rod is used to drive the connecting part to rotate relative to the main body, or to drive the connecting part and the loading part to rotate relative to the main body;

The second driving rod is used for driving the loading part to rotate relative to the connecting part.

In an optional embodiment, the loading portion is provided with a first square hole and a second square hole; the first square hole is used to cooperate with the first driving rod, and the second square hole is used to cooperate with the second driving rod;

The connecting portion is provided with a third hole, and the third hole is used to cooperate with the first driving rod;

The first square hole is coaxial with the third square hole and is connected.

The beneficial effects of the embodiments of the present invention include:

The hollow femoral head screw comprises a main body, a loading part and at least one Kirschner wire; the main body is provided with at least one channel, which runs from the proximal end of the main body to the distal end of the main body, and the channel is used to accommodate the Kirschner wire; the loading part is used to drive the Kirschner wire in the channel to move under the action of external force, so that the Kirschner wire extends out of the channel from the distal end of the main body, and the Kirschner wire extending out of the channel protrudes from the outer peripheral surface of the main body. The hollow femoral head screw can reduce the nail channel formed when fixing the femur, and can reduce the damage to the blood vessels in the femoral head.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

FIG1 is a schematic structural diagram of a femoral head hollow screw from a first viewing angle according to an embodiment of the present invention;

FIG2 is a schematic structural diagram of a hollow femoral head screw from a second viewing angle according to an embodiment of the present invention;

FIG3 is a half-section schematic diagram of a hollow femoral head screw from a first viewing angle according to an embodiment of the present invention;

FIG4 is a half-section schematic diagram of a main body at a first viewing angle in an embodiment of the present invention;

FIG5 is a schematic diagram of the connection between the loading component and the Kirschner wire in an embodiment of the present invention;

FIG6 is a cross-sectional view of a loading portion and a connecting portion in an embodiment of the present invention;

FIG7 is a schematic diagram of the structure of a Kirschner wire in an embodiment of the present invention;

FIG. 8 is a schematic diagram showing the connection between the first driving rod, the second driving rod and the operating handle in an embodiment of the present invention.

Icons: 200-hollow femoral head screw; 210-main body; 220-loading member; 230-Kirschner wire; 211-channel; 212-first segment; 213-second segment; 221-loading part; 222-connecting part; 223-first driving rod; 224-second driving rod; 225-first square hole; 226-second square hole; 227-third party hole; 228-operating handle.

DETAILED DESCRIPTION

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, or is the orientation or position relationship in which the product of the invention is usually placed when used. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

In addition, the terms “first”, “second”, etc., if used, are merely used to distinguish between the descriptions and should not be understood as indicating or implying relative importance.

It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

Please refer to FIGS. 1 to 5 , where FIGS. 1 to 3 show the structure of a hollow femoral head screw in an embodiment of the present invention, FIG. 4 shows the structure of a main body in an embodiment of the present invention, and FIG. 5 shows the structure of a loading member in an embodiment of the present invention. This embodiment provides a hollow femoral head screw 200, which includes a main body 210, a loading member 220, and at least one Kirschner wire 230.

The main body 210 is provided with at least one channel 211, which runs from the proximal end of the main body 210 to the distal end of the main body 210, and the channel 211 is used to accommodate the Kirschner wire 230;

The loader 220 is used to drive the K-wire 230 in the channel 211 to move under the action of external force, so that the K-wire 230 extends out of the channel 211 from the distal end of the main body 210 , and the K-wire 230 extending out of the channel 211 protrudes from the outer peripheral surface of the main body 210 .

It should be noted that, first of all, it should be noted that, first of all, in the full text, the terms "distal end", "proximal end", etc. need to be explained. The explanation here is only for a better understanding of the present disclosure and cannot be understood as a limitation of the present disclosure. The "distal end" can be understood as the end of the femoral head hollow screw 200 that first enters the human body, and the "proximal end" can be understood as the end of the femoral head hollow screw 200 that enters the human body later.

Please refer to Figures 1 to 5, the working principle of the femoral head hollow screw 200 is:

During use of the hollow femoral head screw 200, after the main body 210 is driven into the femur, the Kirschner wire 230 in the channel 211 is driven to move by the loader 220, so that the Kirschner wire 230 extends out of the channel 211 from the distal end of the main body 210, and the Kirschner wire 230 extending out of the channel 211 protrudes from the outer peripheral surface of the main body 210, and can be fixed to the femur; thereby, the number of fixation points with the femur can be increased while reducing the screw channel, so that the damage to the blood vessels in the femoral head can be reduced while ensuring the fixation strength and improving the stability.

Further, please refer to Figures 1 to 5. In the present embodiment, when the channel 211 is set, in order to enable the channel 211 to accommodate the Kirschner wire 230 while guiding the Kirschner wire 230 to extend toward the periphery of the main body 210, the channel 211 includes a first segment 212 and a second segment 213. The first segment 212 extends along the axial direction of the main body 210; the second segment 213 extends obliquely or bends in a direction away from the axis of the main body 210, and the proximal end of the second segment 213 is connected to the distal end of the first segment 212, and the distal end of the second segment 213 is located on the outer peripheral surface of the main body 210; wherein the second segment 213 is used to guide the Kirschner wire 230 to bend or bend.

It should be noted that in the present embodiment, since the Kirschner wire 230 extends out of the channel 211 under the action of the loader 220, it will protrude from the outer peripheral surface of the main body 210. Since the Kirschner wire 230 in the first segment 212 extends along the axial direction of the main body 210, and the Kirschner wire 230 located in the second segment 213 will bend or bend deformed under the external force of the loader 220, the Kirschner wire 230 in the present embodiment is a unidirectional deformable Kirschner wire 230.

Further, please refer to Figures 1 to 5. In this embodiment, the femoral head hollow screw 200 includes three Kirschner wires 230; the main body 210 is provided with three channels 211, and the three channels 211 are arranged in an array on the inner periphery of the main body 210 relative to the axis of the main body 210, and the three Kirschner wires 230 are matched with the three channels 211 in a one-to-one correspondence. Thus, through such a setting, the three Kirschner wires 230 will extend out of the channels 211 in a direction protruding from the outer periphery of the main body 210 under the driving action of the loading member 220; and because the three channels 211 are arranged in an array relative to the axis of the main body 210, that is, after the three Kirschner wires 230 extend out of the channels 211, they are evenly distributed relative to the axis of the main body 210; and because the three Kirschner wires 230 move under the action of the same driving member, their extending actions are synchronized.

Further, please refer to Figures 1 to 6. Figure 6 shows the structure of the loading part and the connecting part in an embodiment of the present invention. In this embodiment, when driving the Kirschner wire 230 to move, a loading member 220 is used. When the loading member 220 is set, the loading member 220 includes a loading part 221 rotatably connected to the main body 210, and the loading part 221 is threadedly connected to the Kirschner wire 230; the loading part 221 is used to rotate relative to the main body 210 under the action of external force, thereby driving the Kirschner wire 230 to slide relative to the channel 211.

When the loading part 221 is arranged, in order to facilitate the operation of the loading part 221 , the loading part 221 is rotatably connected to the proximal end of the channel 211 to be threadedly connected to the portion of the K-wire 230 located outside the proximal end of the channel 211 .

In order to enable the loading part 221 to be threadedly connected to the Kirschner wire 230, a first external thread is provided on the outer circumference of the loading part 221; a threaded section for cooperating with the external thread is provided on the side of the Kirschner wire 230 facing the axis of the main body 210 (as shown in Figure 7), or a second external thread cooperating with the first external thread is provided on the outer circumference of the Kirschner wire 230.

In order to make the loading part 221 rotatably connected to the main body 210, the loading part 220 further includes a connecting part 222; the connecting part 222 is threadedly connected to the main body 210, the connecting part 222 is coaxial with the loading part 221, and the loading part 221 is rotatably connected to the connecting part 222. It should be noted that in order to rotatably connect the loading part 221 and the connecting part 222, a rotating bearing can be provided, that is, a bearing is provided at the connection between the connecting part 222 and the loading part 221.

When the connection portion 222 is installed, the connection portion 222 is threadedly connected to the inner peripheral wall of the main body 210 .

It can be seen from the above content that in the present embodiment, the loading member 220 includes a loading portion 221 and a connecting portion 222, wherein the loading portion 221 is rotatably connected to the connecting portion 222, and its rotation axis coincides with the axis of the main body 210; and the connecting portion 222 is threadedly connected to the inner wall of the main body 210, thereby, when installing the connecting portion 222, the connecting portion 222 can be installed inside the main body 210 by threading the connecting portion 222 to the main body 210; and since the loading portion 221 is rotatably connected to the connecting portion 222, after the connecting portion 222 is connected to the main body 210, the loading portion 221 can be rotatably connected to the main body 210, and can be threadedly connected to the Kirschner wire 230 located outside the proximal end of the channel 211; and then the loading portion 221 can be operated to rotate at the proximal end of the main body 210, thereby driving the Kirschner wire 230 in the channel 211 to slide relative to the channel 211.

Further, please refer to FIG. 1 to FIG. 8 , FIG. 8 shows the structure of the first operating rod and the second operating rod in the embodiment of the present invention. As can be seen from the foregoing content, during the use of the femoral head hollow screw 200, the operation includes rotating the connecting portion 222 to install it in the main body 210, and rotating the loading portion 221 to drive the Kirschner wire 230 to move; therefore, in order to facilitate the operation of the loading portion 221 and the connecting portion 222, the loading member 220 further includes a first driving rod 223 and a second driving rod 224;

Among them, the first driving rod 223 is used to drive the connecting part 222 to rotate relative to the main body 210, or to drive the connecting part 222 and the loading part 221 to rotate relative to the main body 210; it should be noted that in this embodiment, the first driving rod 223 is used to drive the connecting part 222 and the loading part 221 to rotate relative to the main body 210. The purpose of this operation is to install the connecting part 222 in the main body 210; in other embodiments of the present invention, the first driving rod 223 can also be used only to drive the connecting part 222 to rotate relative to the main body 210.

The second driving rod 224 is used to drive the loading portion 221 to rotate relative to the connecting portion 222, so as to drive the K-wire 230 to move through such a setting.

Therefore, in order to enable the loading portion 221 and the connecting portion 222 to cooperate with the first driving rod 223 and the second driving rod 224, the loading portion 221 is provided with a first square hole 225 and a second square hole 226; the first square hole 225 is used to cooperate with the first driving rod 223, and the second square hole 226 is used to cooperate with the second driving rod 224; the connecting portion 222 is provided with a third hole 227, and the third hole 227 is used to cooperate with the first driving rod 223;

The first square hole 225 and the third square hole 227 are coaxial and connected.

Since the present embodiment adopts the operation mode that the first driving rod 223 drives the connecting part 222 and the loading part 221 to rotate relative to the main body 210, when the connecting part 222 is connected to the main body 210, the first driving rod 223 is inserted into the first square hole 225 and the third hole 227, so that the connecting part 222 and the loading part 221 are driven to rotate relative to the main body 210 through the rotation of the first driving rod 223, and then can be driven to connect to the main body 210;

Similarly, when driving the Kirschner wire 230 to move, the second driving rod 224 is inserted into the second square hole 226, and then the second driving rod 224 can drive the loading part 221 to rotate relative to the connecting part 222 and the main body 210, thereby driving the Kirschner wire 230 to move relative to the channel 211 of the main body 210, and then external force can be applied to the Kirschner wire 230, and the Kirschner wire 230 can be deformed along the extended contour of the second segment 213 in the second segment 213 under the action of the external force, so that after extending out of the channel 211, it can protrude from the outer peripheral surface of the main body 210.

It should be noted that, in this embodiment, in order to facilitate the operation of the first driving rod 223 and the second driving rod 224, the loading member 220 further includes an operating handle 228, and the first driving rod 223 and the second driving rod 224 are both detachably connected to the operating handle 228, that is, when the connecting portion 222 needs to be operated, the first driving rod 223 is connected to the operating handle 228 (as shown in B in FIG. 8); and when the loading portion 221 needs to be operated, the second driving rod 224 is connected to the operating handle 228 (as shown in A in FIG. 8);

In addition, when the first driving rod 223 is connected to the operating handle 228, the length of the second driving rod 224 can be greater than the length of the first driving rod 223, or the first driving rod 223 can be retractable, so that the second driving rod 224 can be removed when operating the connecting part 222; and when operating the loading part 221, after the second driving rod 224 is connected to the operating handle 228, at this time, the first driving rod 223 is also connected to the operating handle 228, and after the second driving rod 224 is matched with the second square hole 226, the first driving rod 223 only matches with the first square hole 225, so that the stability of the operation can be improved in this way.

Secondly, when setting the second square hole 226 , in order to improve the stability of the operation of the operating handle 228 , a plurality of second square holes 226 may be provided, and the plurality of second square holes 226 are arranged around the axis of the main body 210 .

In summary, please refer to FIG. 1 to FIG. 8 , taking the femoral head hollow screw 200 provided with three channels 211 and three Kirschner wires 230 as an example, the working steps of the femoral head hollow screw 200 are as follows:

Taking the center of the femoral neck as the entry point, the main body 210 is driven into the axial direction of the femoral neck to a depth of 0.5 cm below the articular surface of the femoral head, and the extension direction of the lowest channel 211 is parallel to the direction of the femoral shaft;

The first driving rod 223 is connected to the operating handle 228, and the first driving rod 223 is matched with the first square hole 225 and the third hole 227. The operating handle 228 is rotated to rotate the connecting portion 222 and the loading portion 221 relative to the main body 210, and then the connecting portion 222 is installed in the main body 210. At this time, since the loading portion 221 is rotatably connected to the connecting portion 222, the loading portion 221 is rotatably connected to the main body 210. It should be noted that the installation of the connecting portion 222 can also be performed before the main body 210 is driven into the femur.

Insert three matching unidirectional deformable Kirschner wires 230 into the channel 211 and threadably connect them to the loading part 221;

The second driving rod 224 is connected to the operating handle 228, and the second driving rod 224 is matched with the second square hole 226. The operating handle 228 is rotated to rotate the loading part 221 relative to the main body 210. Since the loading part 221 is threadedly connected to the three Kirschner wires 230, and the loading part 221 is rotatably connected to the main body 210, the rotation of the loading part 221 can drive the Kirschner wires 230 to move relative to the main body 210.

As the operating handle 228 is rotated, the Kirschner wire 230 can be gradually pushed forward, and the pushing distance can be adjusted according to the size of the femoral head so that the front of the Kirschner wire 230 reaches the designated position.

It should be noted that the femoral head hollow screw 200 needs to be removed after the fracture is completely healed. The operation steps at this time are opposite to the above steps, so they will not be repeated here.

Therefore, through the above operation, the three Kirschner wires 230 of the femoral head hollow screw 200 are fully deployed inside the femoral head. Compared with the traditional method of using three hollow screws, the fixation effect is basically the same, and it also has the effect of anti-rotation and pressurization. The three extended Kirschner wires 230 can also prevent femoral neck shortening; at the same time, since only one main body 210 is used, and only one screw channel is formed, the damage to the femoral head is smaller than that caused by three hollow screws, and the pressure inside the femoral head is also smaller, which is conducive to venous return, reduces the venous pressure of the femoral head, and plays a role in medullary decompression; and when the main body 210 is inserted, the direction of each channel 211 is confirmed, and the lowest channel 211 is parallel to the femoral shaft. When the three Kirschner wire 230 branches are extended, it can be ensured that the three Kirschner wire 230 branches are all in the avascular area of the femoral head. The main body 210 is located in the center of the femoral head, and only passes through part of the vascular communication branches of the epiphyseal artery network area, which does not affect the communication of the three groups of epiphyseal artery vascular networks in the femoral head.

Therefore, compared with other traditional hollow screws, the femoral head hollow screw 200 can avoid the vascular network in the femoral head while ensuring fixation, thereby reducing vascular damage in the femoral head.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (8)

1. A hollow femoral head screw, characterized in that: The femoral head hollow screw comprises a main body, a loading member and at least one Kirschner wire; The main body is provided with at least one channel, the channel runs from the proximal end of the main body to the distal end of the main body, and the channel is used to accommodate the Kirschner wire; The hollow femoral head screw includes three Kirschner wires; The main body is provided with three channels, which are arranged in an array on the inner periphery of the main body relative to the axis of the main body, and the three Kirschner wires are matched with the three channels in a one-to-one correspondence; The loading component is used to drive the Kirschner wire in the channel to move under the action of external force, so that the Kirschner wire extends out of the channel from the distal end of the main body, and the Kirschner wire extending out of the channel protrudes from the outer peripheral surface of the main body; the three Kirschner wires are synchronously extended under the driving action of the same loading component; The loading part includes a loading part and a connecting part, the loading part is rotatably connected to the main body, and the loading part is threadedly connected to the Kirschner wire, the connecting part is threadedly connected to the main body, the connecting part is coaxial with the loading part, and the loading part is rotatably connected to the connecting part, the loading part is provided with a first square hole and a second square hole, and the connecting part is provided with a third hole, wherein the first square hole is coaxial with the third hole and is connected. 2. The hollow femoral head screw according to claim 1, characterized in that: The channel includes a first segment and a second segment, wherein the first segment extends along the axis direction of the main body; The second segment extends obliquely or curvedly in a direction away from the axis of the main body, and the proximal end of the second segment is connected to the distal end of the first segment, and the distal end of the second segment is located on the outer peripheral surface of the main body; Wherein, the second segment is used to guide the bending deformation of the Kirschner wire. 3. The hollow femoral head screw according to any one of claims 1 or 2, characterized in that: The loading part is used to rotate relative to the main body under the action of external force, thereby driving the K-wire to slide relative to the channel. 4. The hollow femoral head screw according to claim 3, characterized in that: The loading part is rotatably connected to the proximal end of the channel so as to be threadedly connected to the portion of the Kirschner wire located outside the proximal end of the channel. 5. The hollow femoral head screw according to claim 3, characterized in that: The outer peripheral surface of the loading part is provided with a first external thread; A threaded section for cooperating with the external thread is provided on one side of the Kirschner wire facing the axis of the main body, or a second external thread cooperating with the first external thread is provided on the outer peripheral surface of the Kirschner wire. 6. The hollow femoral head screw according to claim 1, characterized in that: The connecting portion is threadedly connected to the inner peripheral wall of the main body. 7. The hollow femoral head screw according to claim 1, characterized in that: The loading member further includes a first driving rod and a second driving rod; The first driving rod is used to drive the connecting part to rotate relative to the main body, or to drive the connecting part and the loading part to rotate relative to the main body; The second driving rod is used to drive the loading part to rotate relative to the connecting part. 8. The hollow femoral head screw according to claim 7, characterized in that: The first square hole is used to cooperate with the first driving rod, and the second square hole is used to cooperate with the second driving rod; The third hole is used to cooperate with the first driving rod.