Pedicle screw

Abstract

The present invention provides a pedicle screw, the screw body is a threaded rod with external threads, the threaded rod is stepped, has multiple straight sections, adjacent straight sections are connected by inclined sections, and the diameter of the threaded rod gradually decreases from close to the screw head to away from the screw head. In the present invention, a stepped screw rod design is adopted, which can reduce the decrease in the screw holding force after a small amount of screw withdrawal during surgery compared to a traditional tapered screw rod.

Description

Technical Field

[0001] The invention relates to the field of medical instruments, and in particular to a pedicle screw. Background Art

[0002] Pedicle fixation using a pedicle screw system is a surgical method for treating common spinal diseases such as lumbar fractures, spinal stenosis, and lumbar spondylolisthesis. During the operation, a Kirschner wire is inserted into the lumbar segment that needs to be treated for positioning, and a pedicle screw of appropriate thickness is screwed in after accurate positioning. The screw design of some existing pedicle screws is usually conical. In actual operation, after the pedicle screw is screwed in, the screwing depth of the pedicle screw often needs to be readjusted for various reasons. For example, if it is withdrawn half a turn to a full turn and slightly screwed out, a gap will appear at the screw-bone interface, reducing the holding force between the screw-bone interface, which can easily cause the inserted pedicle screw to loosen and affect the patient's recovery. Summary of the invention

[0003] In view of the technical problem that the holding force between the screw and the bone interface is easily reduced when the position of the traditional pedicle screw is adjusted, the present invention proposes a pedicle screw that can ensure that most of the screw-bone interface remains in close contact after a small amount of screw withdrawal without significant loss of holding force.

[0004] To achieve the above-mentioned purpose, the pedicle screw proposed in the present invention has a screw body which is a threaded rod with an external thread, the threaded rod is stepped and has multiple straight parts, the adjacent straight parts are connected by inclined parts, and the diameter of the threaded rod gradually decreases from close to the screw head to away from the screw head.

[0005] Among them, compared with the traditional conical screw, after a small amount of screw withdrawal, there is a gap between the entire threaded rod and the bone interface. In this scheme, a stepped threaded rod is used. After a small amount of screw withdrawal during the operation, a gap only appears between the inclined part and the bone interface. After a small amount of screw withdrawal, the holding force between the screw and the bone interface can be effectively avoided. Significant decrease, the time for pedicle screw loosening can be extended, and the pain of patients can be alleviated. In addition, the adjacent straight parts are transitioned by the inclined part. During the screw insertion process, the extrusion of the inclined part can compact the bone, further improving the holding force of the screw-bone interface.

[0006] Preferably, in the pedicle screw, the threaded rod is divided into a first threaded rod portion and a second threaded rod portion that are connected to each other. The first threaded rod portion is close to the screw head and has a straight portion. After insertion, the first threaded rod portion is located at the pedicle position and is used to hold the pedicle cortex; the second threaded rod portion has at least two straight portions, and the straight portions are connected and transitioned by inclined portions. After insertion, the second threaded rod portion is located at the vertebral body position, and the second threaded rod portion is stepped. This design is more reasonable in terms of bone loss and stress distribution.

[0007] Preferably, in the pedicle screw, the first threaded rod portion and the second threaded rod portion are connected by an inclined surface portion.

[0008] Preferably, in the pedicle screw, both the straight portion and the inclined portion of the threaded rod have external threads.

[0009] Preferably, in the pedicle screw, the axial length ratio of the inclined portion to the straight portion is 1:10 to 1:1.

[0010] Preferably, in the pedicle screw, the straight portion and the inclined portion are divided into rounded transitions.

[0011] Compared with the prior art, the present invention has the following beneficial effects: the stepped threaded rod design can reduce the decrease in the screw holding force after a small amount of screw withdrawal during surgery, compared with the traditional tapered screw rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the structure of the pedicle screw in the present invention;

[0013] Figure 2 It is a schematic diagram of a small amount of pedicle screw withdrawal in the present invention;

[0014] Figure 3 It is a schematic diagram of a small amount of pedicle screw withdrawal in the prior art.

[0015] In the figure: 1-screw head, 2-nail body, 21-straight part, 22-inclined part, A1-first threaded rod part, A2-second threaded rod part. DETAILED DESCRIPTION

[0016] The pedicle screw of the present invention will be described in more detail below in conjunction with the schematic diagram, wherein a preferred embodiment of the present invention is shown, and it should be understood that those skilled in the art can modify the present invention described herein, and still achieve the beneficial effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art, and not as a limitation of the present invention.

[0017] like Figure 1 As shown, the pedicle screw includes a screw head 1 and a screw body 2, the screw body 2 is a threaded rod with external threads, and the threaded rod is stepped as a whole, with multiple straight sections 21, adjacent straight sections 21 are connected by inclined sections 22, the connection between the straight section 21 and the inclined section 22 adopts a rounded transition, and the straight section 21 and the inclined section 22 both have external threads. The diameter of the threaded rod gradually decreases from the direction close to the screw head 1 to the direction away from the screw head 1. In order to facilitate the placement of the screw, the end of the screw body 2 away from the screw head 1 can be a tip, of course, the tip can be passivated to reduce damage to the vertebral body.

[0018] Specifically, the threaded rod can be divided into two sections according to different insertion positions. Figure 2 The threaded rod is divided into a first threaded rod portion A1 and a second threaded rod portion A2 connected to each other. The first threaded rod portion A1 is close to the screw head 1 and has only one straight portion 21. After insertion, the first threaded rod portion A1 is located at the pedicle; the second threaded rod portion A2 is stepped and has at least two straight portions 21. The straight portions 21 are transitionally connected by an inclined portion 22. After insertion, the second threaded rod portion A2 is located at the vertebral body. As a preferred embodiment, the axial length ratio of the inclined portion 22 to the straight portion 21 is 1:10 to 1:1.

[0019] When the pedicle screw is withdrawn a small amount, the decrease in the holding force of the bone-screw cross section can be reduced. The principle can be found in Figure 2 and Figure 3 , Figure 3 It is shown that when the conical screw in the prior art is withdrawn a small amount, half a turn or one turn, a gap a appears between the screw and the bone interface over the entire length of the screw body; while the stepped screw proposed in this embodiment, when the screw is withdrawn a small amount, a small gap b appears only in the inclined surface part, that is, the shoulder part, and the screw and the bone are still in a tightly fitted state in the rest of the part, such as Figure 2 As shown. Therefore, according to Figure 2 and Figure 3 By comparison, it can be clearly seen that after a small amount of screw withdrawal during surgery, the stepped screw proposed in this embodiment can effectively reduce the amount of space between the screw and bone interface, thereby avoiding a significant decrease in the holding force of the bone-screw cross section.

[0020] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. A pedicle screw, wherein the screw body (2) is a threaded rod with external threads, characterized in that: The threaded rod is in a stepped shape, having a plurality of straight sections (21), adjacent straight sections (21) being connected by inclined sections (22), and the diameter of the threaded rod gradually decreases from close to the screw head (1) to away from the screw head (1); The threaded rod is divided into a first threaded rod portion (A1) and a second threaded rod portion (A2) which are connected to each other. The first threaded rod portion (A1) is close to the screw head (1) and has a straight portion (21). After implantation, the first threaded rod portion (A1) is located at the pedicle. The second threaded rod portion (A2) has at least two straight portions (21). The straight portions (21) are connected and transitioned by inclined portions (22). After implantation, the second threaded rod portion (A2) is located at the vertebral body. The axial length ratio of the inclined portion (22) to the straight portion (21) is 1:10 to 1:1; The first threaded rod portion (A1) and the second threaded rod portion (A2) are connected by an inclined surface portion (22); The straight portion (21) and the inclined portion (22) of the threaded rod both have external threads; After the pedicle screw is withdrawn a small amount during the operation, a gap only appears between the inclined surface part and the bone interface, which can effectively avoid a significant decrease in the holding force between the screw and the bone interface after the small amount of screw withdrawal operation.

2. The pedicle screw according to claim 1, characterized in that: The straight portion (21) and the inclined portion (22) are transitioned into rounded corners.

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