KR101471627B1 - Locking angle adjustable bone plate system - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate system, and more particularly, to a plate system capable of adjusting the angle of a lock screw.
The present plate system capable of adjusting the locking angle according to the present invention includes a plate for fixing the bone and a locking screw. The plate includes a top surface, a bottom surface facing the bone, and a screw formed in at least one hole penetrating the top surface and the bottom surface. The locking screw is formed with a screw for fastening the head to the hole-formed screw. The screw of the head is formed in a tapered portion in a truncated cone shape so that the diameter decreases along the axial direction. In addition, when the screw formed in the head and the screw formed in the hole of the plate are fastened, the central axis of the locking screw can be inclined at a predetermined angle with respect to the center axis of the plate hole, There is a gap between the screw of the plate hole and the screw of the plate hole. The clearance between the screw of the screw head and the screw of the plate hole is larger than the height of each of the ridges of the screw formed in the hole of the plate, .

Description

LOCKING ANGLE ADJUSTABLE BONE PLATE SYSTEM [0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a present plate system, and more particularly, to a plate plate system capable of adjusting the angle of a locking screw.

This plate system for fracture treatment is well known. This plate system pushes the end of the fracture and pulls the fractured bone to closely contact to promote fracture healing. The present plate system includes a main plate and a main screw. The plate may include a threaded hole and an unthreaded hole. The screw has a locking screw with a screw on the head and a non-locking screw with no screw on the head. Both the locking screw and the non-locking screw have a threaded shaft for engagement with the bone.

The threaded shaft of the non-locking screw can be inserted into the bone and coupled at various angles. However, since the non-locking screw is not threaded on the head and is not secured to the plate, the angle between the plate and the screw during and / or after surgery can be changed. In addition, the dynamic load acting on the fractured bone and the plate after surgery can result in screw loosening or inadequate fracture treatment.

The locking screw can engage with the threaded head and the threaded hole of the main plate to fix the angle at which the shaft of the screw is engaged with the bone. The center axis of the lock screw is inserted and screwed so as to be coaxial with the center axis of the threaded hole of the main plate. In addition, it is possible to prevent the screw coupled to the bone from being loosened or loosened by the dynamic load acting on the fractured bone and the plate after the operation. However, the locking screw is bonded to the plate to limit its ability to compress bone fragments that affect fracture treatment.

That is, the non-locking screw can be inserted into the bone at various desired angles and can compress the bone fragments, but has a disadvantage of loosening, and the locking screw can fix the angle of bonding of the bone fragments, There is a disadvantage that the ability is limited.

U.S. Patent No. 6,669,701 discloses this plate with at least one combination hole that can be used with both locking and non-locking screws. The combination hole disclosed in the above patent has a generally circular outer peripheral surface and has a threaded portion and a portion extending in the longitudinal direction and not threaded. The non-locking screw may be inserted at various angles into the non-threaded portion of the mating hole to join the fractured bone piece and provide a compressive force, or a locking screw may be inserted into the threaded portion of the mating hole to form a fractured bone It can be used to combine pieces and fix the combined angle. The present plate disclosed in the patent has a disadvantage in that the adjustment of the angle of engagement of the locking screw to the bone is limited.

Korean Patent Laid-Open No. 10-2010-0058483 discloses a plate plate system capable of adjusting the angle at which a locking screw is coupled to a bone. The present plate system disclosed in the above patent includes a locking plate, a non-locking screw and an angle adjustable locking screw, and a main plate with holes that can be used with the screws. The holes of the main plate have discontinuous columns of a plurality of gears or threaded portions arranged around the circumference and the columns of the plurality of gears or threaded portions are engageable with a screw formed in the locking screw or angle adjustable locking screw head Consists of. In addition, the angle-adjustable head of the locking screw has a spherical portion having a radius of curvature, and a thread is formed on the outer surface of the spherical portion. However, the angle-adjustable locking screw disclosed in the above patent has a drawback that it is difficult to form a thread on the spherical portion of the head portion. It is also difficult to process a plurality of discontinuous threaded columns around the circumference of the hole of the plate.

U.S. Patent No. 6,669,701 entitled " BONE PLATE " Korean Patent Laid-Open No. 10-2010-0058483, entitled "

Although the present plate system as described above has been disclosed, there is a demand for a new plate plate system which is still inexpensive and easy to produce in the market, and can be conveniently used by the surgeon for the purpose of treatment.

It is an object of the present invention to provide a plate system in which a locking screw and a non-locking screw can be inserted into a hole of a main plate by selecting it as required and fastened to a bone. It is another object of the present invention to provide a plate system which can be coupled to a bone at a desired angle within a predetermined range and which can be manufactured at low cost in a shape in which the head portion and the main plate hole of the lock screw can be easily threaded do.

The present plate system capable of adjusting the locking angle according to the present invention includes a plate for fixing the bone and a locking screw. The plate includes a top surface, a bottom surface facing the bone, and a screw formed in at least one hole penetrating the top surface and the bottom surface. The locking screw is formed with a screw for fastening the head to the hole-formed screw. The locking screw further includes a threaded shaft extending along the axial direction in the head and coupled to the bone on the outer circumferential surface. Further, the screw of the head is formed in a tapered portion in a truncated cone shape so that the diameter decreases along the axial direction. In addition, when the screw formed in the head and the screw formed in the hole of the plate are fastened, the central axis of the locking screw can be inclined at a predetermined angle with respect to the center axis of the plate hole, There is a gap between the screw of the plate hole and the screw of the plate hole. The clearance between the screw of the screw head and the screw of the plate hole is larger than the height of each of the ridges of the screw formed in the hole of the plate, .

The bite for forming the screw in the head portion of the screw and the bore for forming the screw in the hole of the plate may be different from each other in order to form the clearance between the screws to be fastened as described above. That is, the screw of the head is machined by a bite having a sharper nose end so that the depth of the crest having the maximum diameter among the crests of the screw formed in the tapered portion of the head is smaller than the height of each of the ridges of the screw formed in the hole of the plate Can be largely formed. The ratio of the width of the end of the nose of the bite for machining the screw to the plate hole with respect to the width of the end of the nose of the bite for machining the screw in the screw head is set to be 1.2 - It is desirable to process the bytes in the 1.8 range.

In the present plate system according to the present invention, the diameter of the thread of the screw formed in the hole of the plate is substantially the same as the diameter of the maximum diameter of the threads of the screw formed in the tapered portion of the head of the locking screw Diameter of the screw formed in the plate hole is larger than the diameter of the acid having the smallest diameter among the mountains formed in the tapered portion of the head.

In some embodiments, the tapered portion of the head is tapered in the form of a multi-tapered frustum so that the diameter decreases, and the screw may be formed in the tapered portion in the multi-tapered frustum shape. The hole of the plate may include a tapered upper portion and a lower tapered lower portion, and the screw of the plate hole may be formed on the inner peripheral surface of the lower portion of the hole. In addition, the plate hole may further include a tapered and threaded intermediate portion between the upper portion and the lower portion in the form of a truncated cone. The lower surface of the plate may have a concave curved surface. In addition, it is preferable that the screw formed in the head of the screw and the screw formed in the hole of the plate are formed of double threads.

According to the present invention, there is provided a present plate system capable of selecting a locking screw and a non-locking screw as needed, and inserting the locking screw into the hole of the present plate to be fastened to the bone.

The present plate system capable of adjusting the locking angle according to the present invention enables the locking screw to be coupled to the bone at a desired angle within a predetermined range, and allows a surgeon to conveniently perform fracture surgery. That is, one locking screw can be used to lock the plate in a predetermined direction or lock in various directions.

In addition, in the present plate system capable of adjusting the locking angle according to the present invention, the head portion of the locking screw and the main plate hole can be manufactured at low cost in a shape that can be easily machined.

1 is a cross-sectional view of one embodiment of a plate according to the present invention;
Fig. 2 is a schematic view showing steps of machining holes and screws of the plate of the embodiment shown in Fig. 1
3 is a schematic view showing a nose portion of a bite for threading a hole in a plate of the embodiment shown in Fig.
4 is a front view of an embodiment of a locking screw according to the present invention;
5 is a schematic view showing the step of machining the locking screw of the embodiment shown in Fig. 4
6 is a schematic view showing the nose portion of the bite for threading the head of the locking screw of the embodiment shown in Fig. 4
Fig. 7 is an explanatory view showing a state in which a screw formed in the hole of the plate shown in Fig. 1 and a screw formed in the head of the locking screw shown in Fig. 4 are fastened by a concentric axis;
Fig. 8 is an explanatory view showing a state where the screw formed in the hole of the plate shown in Fig. 1 and the screw formed in the head of the locking screw shown in Fig.
Figure 9 is a perspective view of another embodiment of the plate according to the invention
Fig. 10 is an explanatory view showing a state where the screw formed in the hole of the plate shown in Fig. 9 and the screw formed in the head of the locking screw shown in Fig. 4 are fastened in the forward direction
Fig. 11 is an explanatory view showing a state where a screw formed in the hole of the plate shown in Fig. 9 and a screw formed in the head of the locking screw shown in Fig. 4 are fastened in the oblique direction
12 is a schematic view showing a state where a non-locking screw is inserted into a screw-formed hole of the plate shown in Fig. 9

In general, the present plate system includes a plate and a screw. The plate has a threaded hole and an unthreaded hole. The locking screw is a screw with a threaded head, typically used for threaded holes. The locking screw is fastened to the threaded hole to provide high resistance to shear stress and torsion, and the screw and plate are combined to ensure stability. Normally, the non-locking screw is used in an unscrewed hole and can be inserted at any angle. Non-locking screws provide optimal compression of the fractured end.

The present plate system according to the present invention, unlike the known conventional plate system, can be fastened to the threaded hole of the plate at any angle.

1 is a cross-sectional view of one embodiment of a plate 10 for use in a present plate system in accordance with the present invention. A plurality of holes are formed in the plate 10, and the holes are formed with screws and no screws. Fig. 1 is a sectional view of a hole-formed portion of the plate 10. Fig. The plate 10 has a top surface 11 and a bottom surface 12 disposed facing the bone and an aperture 13 is formed through the top surface 11 and the bottom surface 12. The plate 10 is preferably made of a biocompatible material, such as titanium, but is not limited thereto. Screws 14 are formed on the inner circumferential surface of the hole 13 and the screw 14 includes a crest 14a and a crest 14b connecting a crest 14c and a crest. The screw 14 of the present embodiment may be a double-thread or a single-row screw.

The hole 13 and the screw 14 of the plate 10 shown in Fig. 1 will be described in more detail with reference to Fig. Fig. 2 (a) shows the hole machining state of the plate 10 before forming the screw in the hole 13. The hole 13 before machining the thread has a tapered upper portion 16 and a tapered intermediate portion 16 which extend at different angles in the upper portion 16 so that the inner circumferential surface is inclined at an angle with respect to the central axis X And a lower portion 13a extending from the middle portion and penetrating the upper surface 11 and the lower surface 12 perpendicularly. Referring to FIG. 2 (b), the upper portion 16 is not threaded but the lower portion 13a and the middle portion 13b are threaded. The diameters d2 of the screws 14 formed in the middle portion 13b and the lower portion 13a are the same and the diameters of the threads of the screws formed in the intermediate portion 13b tapered with respect to the upper surface are the same Is larger than the diameter (d1) of the screw of the screw formed in the vertical lower portion. In some embodiments, intermediate portion 13b may be omitted. 3 (c) shows a state in which the plate 10 is bent so that the lower surface 12 is more closely attached to the bone. The plate 110 of the embodiment shown in Fig. 3 (c) will be described later.

Fig. 3 shows the nose of the hole drilling bit 19 for forming the screw 14 in the hole 13 of the plate 10. Fig. The nose end 19a of the threaded bite 19 has a constant width w1. When the width of the nose end 19a is narrower than the angle A of the same thread, a screw is formed with a deep valley (mountain is high), and when the width is wide, a screw is formed with a low valley (mountain is low). In this embodiment, the screw 14 is machined into the hole 13 of the plate 10 using the nose angle A of the threaded bite 19 of 60 占 and the width w1 of 0.16 mm .

4 is a front view of one embodiment of a locking screw 20 used in the present plate system in accordance with the present invention. The locking screw 20 of this embodiment includes a head 21 and a shaft 26 extending axially in the head. The screw 20 is preferably manufactured using a biocompatible material, for example, titanium, but is not limited thereto. The head (21) is provided with a screw (24) for engagement with a screw (14) formed in the hole of the plate (10). The screw 24 includes a trough 24a and a trough 24b connecting the trough 24c and the trough. The screw 24 of the present embodiment is formed with a double-threaded screw so as to be fastened to the screw 14 formed in the hole 13 of the plate 10. The shaft 26 is formed with a screw 27 to be engaged with the bone and a flute 28 is formed at the end of the shaft 26 so as to allow self-tapping or self-drilling. .

The locking screw 20 shown in Fig. 4 will be described in more detail with reference to Fig. Fig. 5 (a) shows a state before the screw is machined on the locking screw 20. Fig. On the outer circumferential surface of the head 21 of the locking screw 20 is formed a screw 23 which is tapered at a constant angle with respect to the central axis Y. [ The threaded portion 23 is in the form of a truncated cone tapered so as to have a reduced diameter along the central axis Y thereof. The threaded portion 23 may include an upper threaded portion 23a and a lower threaded portion 23b that extends from the upper threaded portion 23a and is tapered to reduce the diameter. In some embodiments, the lower threaded portion 23b may be omitted. 5 (b) shows a state in which the screw 27 for engaging with the bone is machined on the shaft 26 of the screw 20. Referring to FIG. 5 (b), the upper threaded portion 23a has a maximum diameter D1 and a minimum diameter D2. 5 (c) shows a state in which the screw 24 of the head 21 is machined. The maximum diameter of the thread of the screw 24 machined on the head 21 is equal to the maximum diameter D1 of the threaded portion 23a. Fig. 5 (d) shows a state in which the flute 28 is machined at the end of the shaft 26. Fig. Fig. 5 (e) is a cross-sectional view showing that the upper surface 22 of the head is formed with a recess 22a for receiving a tool to insert a screw into the bone or to fasten the hole in the plate.

Figure 6 shows the nose of the threaded bite 29 for forming the screw 24 in the head 21 of the screw 20. [ The nose end 29a of the threaded bite 29 has a constant width w2. If the width w2 of the nose end portion 29a is narrower than the angle A of the same thread, a deep valley screw is formed. If the width w2 is wide, a shallow valley screw is formed. In this embodiment, the screw 24 of the screw head 20 is machined using the nose angle A of the threaded bite 29 of 60 占 and the width w2 of 0.1 mm.

FIG. 7 is an explanatory view showing a state where a screw formed in the hole of the plate shown in FIG. 1 and a screw formed in the head of the locking screw shown in FIG. 4 are fastened in the forward direction; The width w1 of the nose end portion of the hole screwing bite 19 in which the screw 14 of the hole 13 of the plate 10 of this embodiment is machined is smaller than the width w1 of the screw 20 of the screw 20 Is larger than the width (w2) of the nose end portion of the threaded bobbin 29 on which the screw 24 is machined. The height h1 of the thread of the head 21 of the screw 20 is higher than the height h2 of the thread of the hole 13 of the plate 10. [ Thus, when the screw 24 of the head 21 of the screw 20 and the screw 14 of the hole 13 of the plate 10 are fastened together on the concentric axis, There is a play. The center axis X of the hole 13 of the plate 10 and the center axis Y of the screw 20 are concentric with each other and the screw 20 is rotated so as to be fastened, The flanks of the holes 14 and the flanks of the hole 13 are brought into contact and the clearances C1 and C2 are formed between the crests of the screw 21 of the head 21 and the mountains of the screw 14 formed in the hole 13. [ . Further, since the head 21 is in the form of a tapered truncated cone, the clearance closer to the shaft 26 increases the size (volume) of the clearance (C2> C1). When the locking screw 20 is coaxially fastened, the first tooth 24c-1 of the locking screw 20 comes into contact with the middle portion 13b of the hole of the plate 10. [

FIG. 8 is an explanatory view showing a state where a screw formed in the hole of the plate shown in FIG. 1 and a screw formed in the head of the locking screw shown in FIG. 4 are fastened in an inclined direction; 8, the locking screw 20 of the present embodiment is configured such that the center axis Y of the screw 20 is inclined with respect to the center axis X of the hole 13 of the plate 10 within a predetermined angle? And can be fastened at an arbitrary angle. 8, the screw 24 is formed on the truncated conical head of the locking screw 20 so that the diameter of the thread is decreased as the shaft 24 is closer to the shaft direction. Therefore, as the shaft 24 is closer to the shaft 26, The clearance with the screw 14 becomes large. It can be tightened with the screw 14 formed in the lower portion 13a of the hole 13 which penetrates the upper surface 11 and the lower surface 12 of the plate 10 vertically. The maximum value of the angle? Capable of being tilted so as to be inclined is limited by the size of the clearances C1 and C2 and the size of the clearances C1 and C2 is determined by the width of the nose end of the hole- Is limited by the width of the nose end portion. Further, the size of the clearance is limited by the degree of inclination of the taper of the threaded portion in which the screw of the head is formed. The hole of the plate 10 relative to the width w2 of the nose end 29a of the threaded bite 29 for machining the screw 24 on the head 21 of the locking screw 20 The ratio of the width w1 of the nose end 19a of the threaded bobbin 19 for machining the thread 14 to the threaded bushing 13 can be in the range of 1.2 to 1.8. The width w1 of the nose end 19a of the threaded bobbin 19 is formed to be narrower than the width w2 of the nose end 29a of the threaded bobbin 29. [ 8, a part of the first mountain 24c-1 of the screw 24 of the lock screw 20 is inserted into the hole 13 of the plate 10 when the lock screw 20 is tightened so as to be inclined, 1 is inserted into the first valley 14a-1 of the screw 14 of the plate 10 and a part of the first peak 24c-1 comes into contact with the middle portion 13b of the hole 13 of the plate 10. [ If the locking screw 20 can be tilted, interference between the locking screws can be avoided during the procedure, and the fractured bone can be fixed in a direction effective for bone joining.

In some embodiments, the diameters d1 and d2 of the plate holes and the maximum diameter D1 of the screw head and the minimum diameter D2 of the screw head are configured to have the dimensions shown below . It is preferable that the diameter of the screw thread formed in the hole of the plate be equal to the maximum diameter of the screw of the screw formed in the taper of the head of the locking screw, as shown in the following table. In the embodiments having the dimensions shown in the table below, the nose angle A of the threaded bites 19 and 29 is 60 °, the nose end width w1 of the threaded bite 19 is 0.16, And the width w2 of the nose end portion of the threaded bobbin 19 was 0.1 mm. The maximum value of the inclined angle when the screw was formed in the hole of the plate having the dimensions shown in the following table and the lock screw head was approximately 10 °. The thickness of the plate was in the range of 1.6 - 2.0 mm.

Example
plate Locking screw D1 (mm) D2 (mm) d1 (mm) d2 (mm) One 3.6 3.3 3.6 3 2 4.3 3.9 4.3 3.5 3 5.0 4.65 5.0 4.3

9 is another embodiment of the plate 110 according to the present invention. A plurality of holes (113, 150) are formed in the plate (110). Among the holes, there are a hole 113 in which a screw 114 is formed and a hole 150 in which a screw is not formed. A locking screw 20 or a non-locking screw is inserted into the hole 113 formed with the screw 114 and a non-locking screw is inserted into the unthreaded hole 150. The shape and operation of the holes in which screws are not formed are widely used in the known plate system, and a detailed description thereof will be omitted. The plate 110 of this embodiment is bent so that the lower surface thereof is concavely curved with respect to the longitudinal axis line so as to closely contact the bone during the procedure. In addition, the upper surface of the plate 110 becomes a convexly curved shape by bending. Further, the central axes of the holes 113 and 150, which were parallel before bending, are shifted from each other by bending. Referring to FIG. 9, the edge of the plate 110 is formed in a curved shape so as to be thinner toward the edge, thereby reducing the foreign body feeling of the surgical site, and preventing secondary damage such as inflammation after the procedure.

Fig. 10 shows a state in which the locking screw 20 is coaxially fastened to the plate 110 of the embodiment shown in Fig. As shown in Fig. 2 (c), when the plate 110 is bent, the diameter d3 of the screw 14 and the diameter d4 of the bone vary. When the plate 110 is bent, the clearances C1 and C2 should not be removed between the screw 24 of the locking screw 20 and the screw 114 of the plate 110. [ If the bending is excessively excessive, the diameter of the ridge and the mountain of the screw 14 may change, making it impossible to fasten the locking screw or to tilt the screw.

Fig. 11 shows a state in which the locking screw 20 is inclined at an angle &thetas; to the bending plate 110 of the embodiment shown in Fig. A part of the first mountain 24c-1 of the screw 24 of the lock screw 20 is inserted into the first valley 114a-1 of the screw 114 of the hole 110 of the plate 110, -1 is brought into contact with the middle portion 113b of the hole 113 of the plate 110. [

12 shows a state in which the non-locking screw 50 is inserted into the hole 113 in which the screw 114 of the plate 110 is formed. The non-locking screw is not threaded on the head 51 and when the shaft of the non-locking screw 50 is inserted and engaged in the bone, the inclined surface 52 of the screw head 51 is engaged with the plate 110 And contacts the middle portion 113b of the first arm 113 to maintain the inserted direction. That is, when the intermediate portion 113b is formed in the hole 113 of the plate 110 and the screw is formed, the locking screw and the non-locking screw can be selectively used as needed.

While the present invention has been described with reference to the preferred embodiments, those skilled in the art will recognize that numerous modifications and variations can be made without departing from the scope of the present invention. Accordingly, the above-described embodiments of the present invention are not intended to limit the scope of the present invention, and the scope of protection of the present invention is defined only by the claims.

10 plate
20 Lock Screw

Claims (10)

In a present plate system including a plate for fixing a bone and a locking screw,
Wherein the plate includes a top surface, a bottom surface facing the bone, and a screw formed in at least one hole penetrating the top surface and the bottom surface,
Wherein the locking screw comprises a head and a threaded shaft extending along the axial direction in the head and coupled to the bone on the outer circumferential surface, the head being formed in a frusto-conical tapered portion to decrease in diameter along the axial direction Screws,
And a screw thread formed on the tapered portion of the head so that the central axis of the locking screw can be inclined at a predetermined angle with respect to the center axis of the plate hole when the screw formed in the head and the screw formed in the hole of the plate are fastened, Wherein a depth of a valley having a maximum diameter is larger than the height of each of the mountains of the screw formed in the hole of the plate. The method according to claim 1,
Wherein the tapered portion of the head is adjustable in tapered locking angle in the form of a multi-tapered frustum so that the diameter decreases. The method according to claim 1,
Wherein the hole of the plate includes a tapered upper portion and a non-tapered lower portion, the screw of the plate hole being adjustable in the locking angle formed in the inner peripheral surface of the lower portion of the hole. The method of claim 3,
Wherein the plate hole further comprises a tapered and threaded intermediate portion between the upper portion and the lower portion in the form of a truncated cone. 5. The method according to any one of claims 1 to 4,
Wherein the diameter of the thread of the screw formed in the hole of the plate is substantially the same as the diameter of the maximum diameter of the threads of the screw formed in the tapered portion of the head of the locking screw,
Wherein a diameter of a crest of a screw formed in the plate hole is larger than a diameter of a crest having a minimum diameter among the crests formed in a tapered portion of the head. 5. The method of claim 4,
Wherein the lower surface of the plate has a concave curved shape. 5. The method of claim 4,
Wherein the screw formed in the head of the screw and the screw formed in the hole of the plate are two-thread screws. In a present plate system including a plate for fixing a bone and a locking screw,
Wherein the plate includes a top surface, a bottom surface facing the bone, and a screw formed in at least one hole penetrating the top surface and the bottom surface,
Wherein the locking screw comprises a head and a threaded shaft extending along the axial direction in the head and coupled to the bone on the outer circumferential surface, the head being formed in a frusto-conical tapered portion to decrease in diameter along the axial direction Screws,
The screw is screwed into the hole of the plate so that the central axis of the locking screw can be inclined at a predetermined angle with respect to the center axis of the plate hole and is fastened to the tapered portion of the head of the screw Wherein the formed screw is formed into a nose end of a threaded bite which is formed to have a narrower width than the nose end of the threaded bite for machining a screw in the hole of the plate. 9. The method of claim 8,
Wherein a ratio of a width of a nose end portion of a screw thread cutting bite for machining a screw to a width of a nose end portion of a screw thread cutting bite for machining a screw to the screw head is in a range of 1.2 to 1.8, Plate system. 10. The method according to claim 8 or 9,
Wherein the diameter of the thread of the screw formed in the hole of the plate is substantially the same as the diameter of the maximum diameter of the threads of the screw formed in the tapered portion of the head of the locking screw,
Wherein a diameter of a crest of a screw formed in the plate hole is larger than a diameter of a crest having a minimum diameter among the crests formed in a tapered portion of the head.

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