Bone screw extraction tool

Abstract

To provide a tool capable of surely extracting a bone screw even if a hexagonal hole formed in a head is deformed or the bone screw is fixed in a state where the screw extends from the head.SOLUTION: The device is provided with an outer cylinder 10 having a tip part 11 capable of being fixed to a screw hole 55 provided on a plate 50 and a base end part 12 on which a male screw 14R by a right screw is formed, an inner shaft 20 having a saw-toothed sharp tip 211 and arranged inside the outer cylinder 10 in a state that a base end part 22 is extended from a base end opening of the outer cylinder 10 and a male screw 24L by a left screw is formed on a tip side part 211 of the base end part 22, a first nut 30 on which a female screw 41R screwed with the male screw 14R of the outer cylinder 10 is formed and a second nut 40 on which a female screw 42L screwed with the male screw 24L of the inner shaft 20 is formed.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a bone screw extraction tool. [Background technology]

[0002] The present applicant has proposed a barrel-screw type bone screw as a treatment device (implant) for fixation or joining with a compression adjustment function for femoral neck fractures (see Non-Patent Document 1 below).

[0003] Barrel-screw type bone screws consist of a barrel with a head and a hollow screw that is inserted slidably inside the barrel, and multiple bone screws are fixed (embedded) in the femoral neck with or without the use of a plate with screw holes.

[0004] In some cases, such as when fixation or union of a femoral neck fracture is complete, it may be necessary to remove the bone screw from the femoral neck. Here, bone screws fixed to the femoral neck using a plate are usually removed by inserting a hexagonal driver into the hexagonal hole formed in the head of the bone screw and loosening the bone screw (male thread) that is threaded into the female thread formed in the screw hole of the plate. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] "Prima Hip Screw System," Pharmaceuticals and Medical Devices Agency, Pharmaceutical and Medical Device Information Website, [searched July 30, 2024], Internet <URL:https: / / www.info.pmda.go.jp / downfiles / md / PDF / 530180 / 530180_22300BZX00471000_A_01_03.pdf> Summary of the Invention [Problem to be solved by the invention]

[0006] However, in cases where the hexagonal hole formed in the head of the bone screw (barrel) is deformed (stripped), or the bone screw is fixed with the hollow screw extending from the head, it may not be possible to loosen the bone screw with a tool such as a hexagonal driver, making it difficult to remove the bone screw.

[0007] The present invention has been made based on the above circumstances. An object of the present invention is to provide a bone screw removal tool that can reliably remove a bone screw even when the hexagonal hole formed in the head is deformed and the driver cannot function, or when the bone screw is fixed with the screw protruding from the head. [Means for solving the problem]

[0008] (1) The bone screw removal tool of the present invention is a tool for removing a bone screw fixed to a bone, a cylindrical or columnar first member set so that a tip portion thereof is fixed to the bone screw directly or via a plate; a columnar or tubular second member having a sharp tip that can bite into the head of the bone screw, the second member being set inside or outside the first member so that the sharp tip abuts against the head; The device is characterized by comprising a slide operation part for axially moving the second member relative to the first member.

[0009] With this extraction tool, the distal end of the first member is fixed to the bone screw to be extracted, fixing the axial position of the first member relative to the bone screw, and the first and second members are set so that the sharp tip of the second member abuts against the head of the bone screw. By operating the slide operating part to move the second member axially (toward the distal end) relative to the first member, the sharp tip of the second member presses strongly against the head of the bone screw, thereby causing the sharp tip to bite into the head. In this state, by rotating the extraction tool in a direction that loosens the bone screw, the rotational torque is transmitted to the head, loosening the bone screw, and as a result, the bone screw can be extracted even if the hexagonal hole formed in the head is deformed and the driver cannot function.

[0010] (2) A bone screw removal tool according to the first aspect of the present invention is a tool for removing a bone screw fixed to a bone using a plate; an outer cylinder as the first member, the outer cylinder having a tip portion configured to be fastened to a screw hole provided in the plate and a base portion formed with a right-handed male screw; the second member, an inner shaft having a sawtooth-shaped sharp tip, the inner shaft being disposed inside the outer cylinder with a base end portion of the inner shaft extending from a base end opening of the outer cylinder, and a left-handed male screw formed on a tip side portion of the base end; a first nut, as the slide operation part, on which a first female thread is formed that threadably engages with the male thread formed on the base end part of the outer cylinder, and a second female thread is formed that threadably engages with the male thread formed on the base end part of the inner shaft; a second nut having an internal thread formed on a tip side of the first nut member, the internal thread being engaged with the external thread formed on the base end of the outer cylinder; The present invention is characterized by comprising:

[0011] With this type of extraction tool, the tip of the outer tube is fixed to the screw hole formed in the plate, fixing the axial position of the outer tube relative to the bone screw; the outer tube and the inner shaft are set so that the sharp tip of the inner shaft abuts against the head of the bone screw; and with the rotation of the inner shaft stopped, when the first nut member is rotated clockwise, the inner shaft will move towards the tip relative to the outer tube, causing the sharp tip of the inner shaft to strongly press against the head of the bone screw, thereby allowing the sharp tip to bite into the head. In this state, by rotating the extraction tool in the direction that loosens the bone screw (counterclockwise, i.e., in the direction that the left-handed screw moves forward), the rotational torque is transmitted to the head and the bone screw is loosened, so that the bone screw can be extracted even if the hexagonal hole formed in the head is deformed and the driver can no longer function.

[0012] (3) In the bone screw removal tool according to the first aspect of the present invention, The screw hole of the plate is countersunk, and a second female screw with a right-hand thread is formed on the inner peripheral surface of the countersunk hole, A male thread that can be threadably engaged with the second female thread is formed at the tip of the outer cylinder, It is preferable that the tip portion of the outer cylinder is fixed to the screw hole (counterbore portion) of the plate by threading the male screw and the second female screw together.

[0013] According to the extraction tool having such a configuration, the tip end of the outer cylinder can be securely fixed to the screw hole of the plate.

[0014] (4) In the bone screw removal tool according to the first aspect of the present invention, It is preferable that a recess be formed in the distal end of the inner shaft, extending from a distal end opening toward the proximal end.

[0015] With this type of extraction tool, even if the bone screw is fixed with the screw extending from the head, the bone screw can be extracted while the screw is housed in the recess formed in the inner shaft.

[0016] (5) The bone screw extraction tool according to the second aspect of the present invention is a bone screw extraction tool, wherein the bone screw to be extracted is a barrel-screw type bone screw in which a screw is inserted inside a barrel having a head; the first member being a removal driver having a tip portion configured to be fastened to a base end portion of the screw extending from the head, and a large-diameter base portion capable of preventing the extraction of an extractor bolt (described later); The second member is an extractor having a sawtooth sharp tip and a base end portion formed with a right-handed internal thread, and is disposed outside the removal driver; The slide operation unit is characterized in that it includes an extractor bolt having a male thread formed thereon that screws into the female thread formed on the base end of the extractor.

[0017] With this type of extraction tool, the tip of the removal driver is fixed to the screw extending from the head, fixing the axial position of the removal driver relative to the bone screw, and the removal driver and extractor are set so that the sharp tip of the extractor abuts against the head of the bone screw. With the rotation of the extractor stopped, when the extractor bolt is rotated counterclockwise, the extractor will attempt to move toward the tip relative to the extractor bolt and removal driver, and the sharp tip of the extractor will press strongly against the head of the bone screw, thereby allowing the sharp tip to bite into the head. In this state, by rotating the removal tool in the direction that loosens the bone screw (counterclockwise), the rotational torque is transmitted to the head and the bone screw is loosened, thereby making it possible to remove the bone screw even if the hexagonal hole formed in the head is deformed and the driver cannot function, or if the bone screw is fixed with the screw extending from the head.

[0018] (6) In the bone screw removal tool according to the second aspect of the present invention, a left-handed internal thread is formed at the base end of the screw, a male thread is formed at the distal end of the removal driver so as to be able to be threaded with the female thread formed at the proximal end of the screw; It is preferable that the distal end of the removal driver be fixed to the proximal end of the screw by threading the male thread and the female thread together.

[0019] According to the removal tool having such a configuration, the tip end of the removal driver can be securely fixed to the base end of the screw.

[0020] (7) The bone screw removal tool of the present invention can be suitably used to remove, from the femur, a bone screw used for fixation or joining of a femoral neck fracture. [Effects of the Invention]

[0021] According to the bone screw removal tool of the present invention, it is possible to remove a bone screw even when the hexagonal hole formed in the head is deformed and the driver cannot function, or when the bone screw is fixed with the screw protruding from the head. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a perspective view showing a bone screw removal tool according to a first aspect of the present invention. [Figure 2] FIG. 2 is a perspective view showing components of the extraction tool shown in FIG. 1. [Figure 3A] 2 is an explanatory diagram schematically illustrating the structure of the removal tool shown in FIG. 1 (in a state where the tip of the inner shaft is positioned inside the outer cylinder). FIG. [Figure 3B] 2 is an explanatory diagram schematically illustrating the structure of the removal tool shown in FIG. 1 (in a state where the tip of the inner shaft extends from the tip opening of the outer cylinder). FIG. [Figure 4] 2 is an explanatory view showing a state in which the extraction tool shown in FIG. 1 is used. FIG. [Figure 5]FIG. 10 is a front view showing a bone screw removal tool according to a second aspect of the present invention. [Figure 6] FIG. 6 is a front view showing the components of the extraction tool shown in FIG. 5. [Figure 7A] FIG. 6 is an explanatory diagram schematically illustrating the structure of the removal tool shown in FIG. 5 (in a state where the sharp tip of the extractor is positioned on the proximal end side of the tip portion of the removal driver). [Figure 7B] FIG. 6 is an explanatory diagram schematically illustrating the structure of the removal tool shown in FIG. 5 (in a state where the sharp tip of the extractor is positioned on the tip side of the tip portion of the removal driver). [Figure 8] 6 is an explanatory view showing a state in which the extraction tool shown in FIG. 5 is used. FIG. [Figure 9] FIG. 10 is a perspective view showing an example of the shape of the sharp tip of the second member. DETAILED DESCRIPTION OF THE INVENTION

[0023] First Embodiment 1 to 4, a bone screw removal tool 100 according to this embodiment (first invention) is a tool for removing a bone screw 90 fixed to a bone using a plate 50. The removal tool 100 comprises an outer tube 10 (first member) having a distal end 11 configured to be fastenable to a counterbore of a screw hole 55 provided in the plate 50 and a proximal end 12 on which a right-handed male thread 14R is formed; the inner shaft 20 (second member) formed with the outer cylinder 10; a first nut 30 (slide operation portion) formed with a first female thread 31R that screws together with the male thread 14R formed on the base end 12 of the outer cylinder 10 and a second female thread 32L that screws together with the male thread 24L formed on the base end 22 of the inner shaft 20; and a second nut 40 formed on the tip side of the first nut member 30 with a female thread 41R that screws together with the male thread 14R formed on the base end 12 of the outer cylinder 10.

[0024] As shown in FIG. 4, the bone screw 90 to be removed by the removal tool 100 is a barrel-screw type bone screw in which a hollow screw 92 is inserted inside a barrel 91 having a head 93, and the base end 922 of the hollow screw 92 extends from the head 93. A right-handed male thread 95R is formed at the base end of a barrel 91 constituting the bone screw 90. A hexagonal hole (not shown) is formed in a head 93 of the barrel 91.

[0025] The plate 50 is provided with a screw hole 55 through which the bone screw 90 is inserted, and this screw hole 55 is formed with a female thread 551R that screws together with a male thread 95R formed on the bone screw 90 (at the base end of the barrel 91), and the female thread 551R screws together with the male thread 95R, thereby firmly fixing the bone screw 90 to the screw hole 55 of the plate 50. The screw hole 55 of the plate 50 is countersunk, and a second female thread 552R with a right-handed screw is formed on the inner circumferential surface of the countersunk hole formed by the countersunk processing.

[0026] The extraction tool 100 of this embodiment is made up of an outer cylinder 10 (first member), an inner shaft 20 (second member), a first nut 30 (slide operation portion), and a second nut 40.

[0027] The outer tube 10 constituting the removal tool 100 is a cylindrical first member having an inner diameter larger than the outer diameter of the head 93, and has a tip end 11 formed with a right-handed male thread 13R, and a base end 12 formed with a right-handed male thread 14R.

[0028] The male thread 13R formed on the tip portion 11 can be threadably engaged with the second female thread 552R formed in the counterbore hole 555 of the screw hole 55 of the plate 50. The male thread 13R formed on the tip portion 11 and the second female thread 552R formed in the countersunk hole 555 of the screw hole 55 are threadedly engaged with each other, so that the tip portion 11 of the outer tube 10 is fixed to the countersunk portion of the screw hole 55 of the plate 50, and the axial position of the outer tube 10 relative to the bone screw 90 is fixed, so that the outer tube 10 cannot move in the axial direction or rotate.

[0029] The inner shaft 20 constituting the removal tool 100 is a columnar second member. A recess 215 is formed in the tip portion 21 of the inner shaft 20, and the base end portion 922 of the hollow screw 92 extending from the head 93 can be accommodated in this recess 215. The inner shaft 20 has a sharp, serrated tip 211 .

[0030] The inner shaft 20 is disposed inside the outer cylinder 10 with its base end 22 extending from the base end opening of the outer cylinder 10 . A left-handed male thread 24L having an outer diameter larger than the inner diameter of the outer tube 10 is formed in a tip side portion 221 of the base end portion 22, so that the base end portion 22 of the inner shaft 20 always extends from the base end opening of the outer tube 10. The base side portion 222 of the base end portion 22 is shaped like a hexagonal pillar. As shown in FIG. 2, the base end portion 22 refers to the portion from the base end of the inner shaft 20 to the tip position of the male thread 24L.

[0031] The first nut 30 constituting the removal tool 100 has a first female thread 31R (right-handed thread) that screws into the male thread 14R formed on the base end 12 of the outer tube 10, and a second female thread 32L (left-handed thread) that screws into the male thread 24L formed on the base end 22 of the inner shaft 20.

[0032] The first nut 30 and the outer tube 10 are threaded together with a right-handed thread (first female thread 31R, male thread 14R), and the first nut 30 and the inner shaft 20 are threaded together with a left-handed thread (second female thread 32L, male thread 24L). Therefore, when the first nut 30 is "rotated left" with the rotation of the outer tube 10 and the inner shaft 20 stopped, the outer tube 10 moves (advances) toward the tip relative to the first nut member 30, and the inner shaft 20 moves (retreats) toward the base end. FIG. 3A shows the state after the first nut 30 has been "rotated left," and as shown in the figure, the tip portion 21 (sharp tip 211) of the inner shaft 20 is located inside the outer cylinder 10.

[0033] Conversely, when the rotation of the outer tube 10 and the inner shaft 20 is stopped and the first nut 30 is rotated clockwise (rotation in the direction in which the right-handed screw moves forward), the outer tube 10 moves toward the base end (retreat) relative to the first nut member 30, and the inner shaft moves toward the tip end (advance). FIG. 3B shows the state after the first nut 30 has been "rotated right," and as shown in the figure, the tip portion 21 (sharp tip 211) of the inner shaft 20 extends from the tip opening of the outer cylinder 10.

[0034] The second nut 40 constituting the removal tool 100 is formed with a female thread 41R that threadably engages with a male thread 14R formed on the base end 12 of the outer tube 10 at the distal end side of the first nut member 30. By threading the base end 12 of the outer tube 10 (male thread 14R) and the second nut member 40 (female thread 41R) at the distal end side of the first nut member 30, it is possible to prevent the first nut member 30 from loosening when loosening the bone screw 90, for example.

[0035] According to the extraction tool 100 of this embodiment, the distal end portion 11 of the outer tube 10 is fixed to the countersunk portion of the screw hole 55 provided in the plate 50, and the axial position of the outer tube 10 relative to the bone screw 90 is fixed. At the same time, the outer tube 10 and the inner shaft 20 are set so that the sharp distal end 211 of the inner shaft 20 abuts against the head 93 of the bone screw 90. Then, the proximal end portion 222 of the proximal end portion 22 is gripped to stop the rotation of the inner shaft 20 (the countersunk portion of the screw hole 55). When the first nut member 30 is rotated "right," the inner shaft 20 tries to move distally relative to the outer cylinder 10, whose distal end 11 is fixed in the screw hole 55 of the plate 50 and which is unable to move proximally, and the sharp tip 211 of the inner shaft 20 presses strongly against the head 93 of the bone screw 90, thereby allowing the serrated sharp tip 211 to bite into the head 93, as shown in FIG. 4.

[0036] By rotating the first nut member 30 clockwise until it can no longer be rotated, the serrated sharp tip 211 is engaged with the head 93, and then rotating the proximal portion 222 of the inner shaft 20 (counterclockwise) in this state, the removal tool 100 rotates in the direction that loosens the bone screw 90, and the rotational torque is reliably transmitted to the head 93, loosening the bone screw 90. Note that by threading the first nut member 30 onto the proximal end 12 (external thread 14R) of the outer cylinder 10, and further threading the second nut member 40 (internal thread 41R) so that it abuts against the distal side of the first nut member 30, it is possible to prevent the first nut member 30 from loosening when loosening the bone screw 90. This allows the bone screw 90 to be removed even if the hexagonal hole formed in the head 93 is deformed and the driver is no longer functional.

[0037] Furthermore, the base end 922 of the screw 92 extending from the head 93 is housed in the recess 215 formed in the tip 21 of the inner shaft 20 during the removal operation, so the bone screw 90 can be removed even when the base end 922 of the screw 92 extends from the head 93.

[0038] Second Embodiment The bone screw removal tool 200 according to this embodiment (second invention) shown in Figures 5 to 8 is a tool for removing a barrel-screw type bone screw 90, which has a hollow screw 92 inserted inside a barrel 91 having a head 93, and has a left-handed internal thread 94L formed at the base end 922 of the hollow screw 92. This removal tool 200 comprises a removal driver 60 (first member) having a tip portion 61 configured to be fixed to the base end 922 of the hollow screw 92 by forming a male thread 64L that can be threaded with a female thread 94L formed on the base end 922 of the hollow screw 92 extending from the head 93, and a large-diameter base end 62 that enables the extractor bolt 80 described below to be prevented from coming out; an extractor 70 (second member) that has a base end 72 formed with a serrated sharp tip 711 and a right-handed female thread 74R and is positioned outside the removal driver 60; and an extractor bolt 80 (slide operating part) that has a male thread 81R that threads with the female thread 74R formed on the base end 72 of the extractor 70.

[0039] The bone screws 90 removed by the removal tool 200 of this embodiment have the same configuration as those removed by the removal tool 100 of the first embodiment, and multiple bone screws are fixed (embedded) in the femoral neck (FEMUR) without using a plate. The bone screw 90 includes a hollow screw 92 having a base end 922 formed with a left-handed internal thread 94L.

[0040] The removal tool 200 is made up of a removal driver 60 (first member), an extractor 70 (second member), and an extractor bolt 80 (slide operation portion).

[0041] The removal driver 60 constituting the removal tool 200 is a columnar first member having a tip portion 61, a cylindrical small-diameter shaft portion 63, and a hexagonal columnar large-diameter base end portion 62.

[0042] A left-handed male thread 64L is formed on the distal end 61 of the removal driver 60. The male thread 64L formed on the distal end 61 can be threadably engaged with a female thread 94L formed on the proximal end 922 of the hollow screw 92. By threading the male thread 64L and the female thread 94L together, the distal end 61 of the removal driver 60 is fixed to the proximal end 922 of the hollow screw 92. This fixes the axial position of the removal driver 60 relative to the bone screw 90, and the removal driver 60 cannot move axially or rotate.

[0043] The outer diameter (the diameter of the circumscribed circle of the hexagonal cross-sectional shape) of the large-diameter base end 62 of the removal driver 60 is larger than the inner diameter of the extractor bolt 80 (hollow bolt), so that the extractor bolt 80, which moves toward the base end outside the removal driver 60, will not come loose toward the base end.

[0044] The extractor 70 constituting the removal tool 200 is a cylindrical second member that has a sawtooth sharp tip 711, a small diameter cylindrical portion 73, and a cylindrical base end portion 72 whose diameter (outer diameter and inner diameter) is larger than that of the small diameter cylindrical portion 73, and is positioned outside the removal driver 60.

[0045] A right-handed female screw 74R is formed on the base end 72 of the extractor 70. A fixing knob 75 is integrally formed on the outer periphery of the base end 72.

[0046] The extractor bolt 80 constituting the removal tool 200 is formed with a male thread 81R that screws into the female thread 74R formed on the base end 72 of the extractor 70, and is a hollow bolt that can accommodate the tip end 61 and small diameter shaft 63 of the removal driver 60. The head 85 of the extractor bolt 80 is used as a rotation knob.

[0047] The base end 72 (female thread 74R) of the extractor 70 is screwed into the extractor bolt 80 (male thread 81R), and the removal driver 60 (tip end 61 and small diameter shaft 63) is inserted into the extractor bolt 80 and the extractor 70 from the base end opening of the extractor bolt 80. After that, with the rotation of the removal driver 60 and the extractor 70 stopped, the extractor bolt 80 is rotated "right," and the extractor 70 moves in the base end direction relative to the extractor bolt 80 and the removal driver 60. FIG. 7A shows the state after the extractor bolt 80 has been "rotated to the right," and as shown in the figure, the tip 61 of the removal driver 60 extends from the tip opening of the extractor 70 (the sharp tip 711 of the extractor 70 is located on the proximal side of the tip 61 of the removal driver 60).

[0048] Conversely, when the extractor bolt 80 is rotated left while the rotation of the removal driver 60 and the extractor 70 is stopped, the extractor 70 moves in the distal direction relative to the extractor bolt 80 and the removal driver 60. Figure 7B shows the state after the extractor bolt 80 has been "rotated left," and as shown in the figure, the tip 61 of the removal driver 60 is located inside the extractor 70 (the sharp tip 711 of the extractor 70 is located on the tip side of the tip 61 of the removal driver 60).

[0049] According to the extraction tool 200 of this embodiment, the distal end 61 of the removal driver 60 is fixed to the proximal end 922 of the hollow screw 92, the axial position of the removal driver 60 relative to the bone screw 90 is fixed, and the removal driver 60 and the extractor 70 are set so that the sharp distal end 711 of the extractor 70 abuts against the head 93 of the bone screw 90. Then, with the rotation of the removal driver 60 and the extractor 70 stopped, the extractor bolt 80 is rotated counterclockwise. In contrast to the removal driver 60, which cannot move in the proximal direction because its tip end 61 is fixed to the proximal end 922 of the hollow screw 92, and the extractor bolt 80, which cannot move in the proximal direction because it is prevented from coming out by the large-diameter proximal end 62 of the removal driver 60, the extractor 70 attempts to move in the distal direction, and the sharp tip 711 of the extractor 70 presses strongly against the head 93 of the bone screw 90, thereby allowing the serrated sharp tip 711 to bite into the head 93, as shown in Figure 8.

[0050] By rotating the extractor bolt 80 counterclockwise until it can no longer be rotated, causing the serrated sharp tip 711 to bite into the head 93, and then rotating (counterclockwise) the large-diameter base end 62 of the removal driver 60, the extraction tool 200 rotates (counterclockwise) in the direction that loosens the bone screw 90, and the rotational torque is reliably transmitted to the head 93, thereby loosening the bone screw 90. This allows the bone screw 90 to be removed even if the hexagonal hole formed in the head 93 is deformed or if the bone screw is fixed with the hollow screw 92 extending from the head 93.

[0051] Although the embodiments of the present invention have been described above, the extraction tool of the present invention is not limited to these embodiments and can be modified in various ways. For example, the sharp tip of the second member (inner shaft and extractor) does not have to be serrated (Triangle) as long as it has a shape that can bite into the head of the bone screw, and may have a shape with a claw-like blade 911 (Under Blade) as shown in Figure 9. [Explanation of symbols]

[0052] 100 Removal tool 10 outer cylinder (first member) 11 Tip 12 Proximal end 13R Male thread formed at the tip 14R Male thread formed at the base end 20 Inner shaft (second member) 21 Tip 211 Sharp Tip 215 recess 22 Proximal end 221 Tip end of base end 222 Proximal end of proximal end 24L Male thread formed at the tip end of the base end 30 First nut member (slide operation portion) 31R First female thread 32L Second female thread 40 Second nut member 41R female thread 50 plates 55 screw holes 551R female thread 552R Second female thread 555 counterbore 200 Removal tool 60 Removal driver (first component) 61 Tip 62 Large diameter base end 63 Small diameter shaft 64L male thread 70 Extractor (second component) 711 Sharp Tip 72 Proximal end 73 Small diameter cylindrical part 74R female thread 75 Fixed knob 80 Extractor bolt (slide operation part) 81R male thread 85 Head (rotary operation knob) 90 Bone Screws 91 barrels 92 Hollow screw 922 Proximal end of hollow screw 93 head 94L Female thread formed at the base end of the hollow screw 95R Male thread formed at the base end of the barrel

Claims

1. A tool for removing a bone screw fixed in a bone, comprising: a cylindrical or columnar first member (10, 60) set so that its tip (11, 61) is fixed to the bone screw directly or via a plate; a columnar or tubular second member (20, 70) having a sharp tip (211, 711) that can bite into the head of the bone screw, and set inside or outside the first member (10, 60) so that the sharp tip (211, 711) abuts against the head; a slide operation unit (30, 80) for axially moving the second member (20, 70) relative to the first member (10, 60); A bone screw removal tool comprising:

2. A tool for removing bone screws secured to a bone using a plate; The first member is an outer cylinder (10) having a tip end (11) configured to be fastened to a screw hole (55) provided in the plate (50) and a base end (12) formed with a right-handed male screw (14R); the second member being an inner shaft (20) having a sawtooth sharp tip (211), a base end (22) of the inner shaft (20) described below being disposed inside the outer cylinder (10) in a state where it extends from a base end opening of the outer cylinder (10), and a left-handed male screw (24L) formed in a tip side portion (221) of the base end (22); a first nut (30) as the slide operation part, on which a first female thread (31R) that threadably engages with the male thread (14R) formed on the base end (12) of the outer cylinder (10) and a second female thread (32L) that threadably engages with the male thread (24L) formed on the base end (22) of the inner shaft (20) are formed; a second nut (40) having a female thread (41R) formed on the tip side of the first nut member (30) to be threadedly engaged with the male thread (14R) formed on the base end (12) of the outer cylinder (10); 2. The bone screw removal tool of claim 1, further comprising:

3. The screw hole (55) of the plate (50) is countersunk, and a second female screw (552R) with a right-hand thread is formed on the inner peripheral surface of the countersunk hole, A male thread (13R) that can be threadably engaged with the second female thread (552R) is formed on the tip end (11) of the outer cylinder (10), 3. The bone screw removal tool according to claim 2, wherein the distal end portion (11) of the outer cylinder (10) is fixed to the screw hole (55) of the plate (50) by threading the external thread (13R) and the second internal thread (552R) together.

4. 3. The bone screw removal tool according to claim 2, wherein a recess (215) extending from a distal opening toward a proximal end is formed in the distal end portion (21) of the inner shaft (20).

5. The bone screw to be removed is a barrel-screw type bone screw (90) having a barrel (91) with a head (93) and a screw (92) inserted therein; As the first member, a removal driver (60) having a tip portion (61) configured to be fastened to a base end portion (922) of the screw (92) extending from the head (93), and a large-diameter base end portion (62) capable of preventing the extraction of an extractor bolt (80) described below; The second member is an extractor (70) that has a sawtooth sharp tip (711) and a base end (72) on which a right-handed internal thread (74R) is formed, and that is disposed outside the removal driver (60); 2. The bone screw removal tool according to claim 1, wherein the slide operation part comprises an extractor bolt (80) having a male thread (81R) formed thereon that meshes with the female thread (74R) formed on the base end (72) of the extractor (70).

6. A left-handed female screw (94L) is formed at the base end (922) of the screw (92), A male screw (64L) that can be threaded with the female screw (94L) formed on the base end (922) of the screw (92) is formed on the tip end (61) of the removal driver (60), 6. The bone screw removal tool according to claim 5, wherein the distal end (61) of the removal driver (60) is fixed to the proximal end (922) of the screw (92) by threading the male thread (64L) and the female thread (94L) together.

7. 7. The bone screw removal tool according to claim 1, for removing a bone screw used for fixation or joining of a femoral neck fracture from a femur.

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