Internal fixation instrument and treatment instrument

Abstract

Provided is an internal fixation instrument that is inserted from the pedicle of a vertebral arch into bone cement with which a vertebral body has been filled in advance, and that can be easily removed while maintaining the same level of internal fixation performance as that of a screw. The internal fixation instrument is inserted from the pedicle of a vertebral arch into bone cement with which a vertebral body has been filled, and is provided with a cylindrical shaft and a connection part that is disposed at the distal end of the shaft and that can be connected to a screwdriver, the shaft having a helical groove on the proximal side thereof. More preferably, the internal fixation instrument has a screw thread on the distal end side of the shaft, and the lead of the screw thread and the lead of the groove are set to be equal to each other.

Description

Internal fixation and treatment devices The present invention relates to a cylindrical internal fixation device for medical use and a treatment instrument for operating the same, and is particularly suitable for use in surgery for internal fixation of an affected vertebral body. Vertebroplasty and spinal fixation are known as treatments for spinal compression fractures. The spine is composed of stacked vertebral bodies and the vertebral arch, pedicle, articular process, etc. that support them. The vertebral body is a cylindrical bone that sandwiches the nucleus pulposus and the annulus fibrosus that surrounds it from above and below, and is supported by two pedicles extending from the vertebral arch. The vertebral arch is connected to the top and bottom by the upper and lower articular processes, supports the vertebral body through the pedicle, and forms the spine. Compression fracture is a disease in which the vertebral body is crushed and damaged by vertical compression. Vertebroplasty is a surgery to reconstruct the crushed vertebral body, and for example, a surgical method is used in which medical cement is filled into the vertebral body. Spinal fixation is a surgical method in which the crushed vertebral body and the healthy vertebral bodies above and below it are fixed with an instrument. Screws are screwed into the crushed vertebral body and the healthy vertebral bodies above and below it from the pedicle, and the heads of the screws are connected to rods that are crossed in the vertical direction to fix them. If symptoms are mild, vertebroplasty is used, but if symptoms are severe, spinal fusion surgery is required. A variety of screws have been proposed for use in these treatments. Patent Document 1 discloses a medical screw having a longitudinal through hole along the central axis and a side opening communicating with the through hole. An injection tool such as a syringe is attached to the head of the screw, and bone cement or a physiologically activating substance is injected from the through hole through the opening in the rough surface into the surrounding bone, thereby reinforcing the surrounding bone (

[0053] ~

[0057] , Figs. 6-8). Patent Document 2 discloses a medical screw that can be easily removed from the fracture site where it is screwed in. The medical screw has a hollow section formed from the head to the tip along the central axis, and a screw thread is formed on the side, and is screwed into the bone. A reverse screw thread (reverse internal thread) is provided near the inner tip of the hollow section of the screw, and it is possible to remove the screw by using a removal tool with a tip that engages with the reverse internal thread. More specifically, the removal tool is inserted from the hollow section, and the tip is engaged with the reverse internal thread of the screw to form one unit, and the removal tool is rotated to remove the screw from the body. US Publication No. 2011 / 0040337A1 JP 2016-209295 A The present inventor found that the development of medical instruments and screws suitable for the above-mentioned combined vertebroplasty and pedicle plasty was insufficient, and invented a treatment instrument that solves this problem, and filed an international application under PCT / JP2022 / 036147. This invention is a treatment instrument integrated with a screw having a through hole along the central axis and a tappable thread on the side, and is configured so that bone cement can be injected into the affected area through the through hole of the screw with a driver connected to the head of the screw, and then the screw can be screwed into the bone cement. After injecting the bone cement, there is no need to attach the driver again, and the driver can be operated as it is, so the screw can be quickly screwed in before the bone cement hardens. The inventors have noticed that when it becomes necessary to remove the screw after the bone cement has hardened, there is a risk that the screw will be too tightly bitten into the bone cement and will not be able to be removed properly. Normally, it is almost unthinkable that the screw will need to be removed after surgery, but it cannot be said that there will be no complications such as postoperative infections at the affected area, and the inventors have thought that making it possible to remove the screw would contribute to the treatment of postoperative complications. On the other hand, in conventional screws such as those disclosed in Patent Document 1, it is not assumed that the screw will be screwed into bone cement that has been injected beforehand, but rather that after the screw is screwed in, cement or the like is injected around the screw from an opening in the side wall to reinforce the surrounding bone. Therefore, it is basically the bone that engages with the threads of the screw, and it is considered that the screw can be relatively easily removed by rotating the screw in the reverse direction. However, if it is expected that removal will be difficult, a screw and removal tool designed for removal, such as those described in Patent Document 2, will be used. The inventors have further studied the risk of the screw being too tightly bitten into the bone cement and becoming unable to remove the screw, and have found that such a risk becomes apparent when the bond between the bone cement and the screw is stronger than the adhesion between the bone cement and the diseased tissue such as the surrounding bone. In that case, they have found that using the removal tool as described in Patent Document 2 does not solve the problem. The removal tool as described in Patent Document 2 can strongly connect the screw and the driver and transmit a strong force to the screw, so it helps removal when the surrounding area is diseased tissue such as the patient's bone, but when the bond between the bone cement and the screw is stronger than the adhesion between the bone cement and the diseased tissue such as the surrounding bone, as described above, there is a risk that the bone cement will separate from the surrounding diseased tissue instead of the screw coming out of the bone cement, and it does not help removal. An object of the present invention is to provide an internal fixation device which is inserted from the pedicle into bone cement which has been filled in advance in the vertebral body, and which can be easily removed while maintaining the same level of internal fixation performance as a screw. Means for solving these problems will be described below, but other problems and novel features will become apparent from the description of this specification and the accompanying drawings. According to one embodiment of the present invention, the following is true. That is, it is an internal fixation device that is inserted from the pedicle into bone cement filled in the vertebral body, and is equipped with a cylindrical shaft and a connection portion at the distal end of the shaft that can be connected to a driver, and the shaft has a spiral groove on the proximal side. Here, proximal is the side closer to the centerline of the patient's body, and distal is the medical term for the far side. Bone cement is a medical cement that is mainly composed of calcium phosphate and polymethylmethacrylate, and hardens over time. The effects obtained by the embodiment are briefly described below. That is, it is possible to provide an internal fixation device that is inserted from the pedicle into bone cement that has been filled in advance within the vertebral body, and that can be easily removed while maintaining the same level of internal fixation performance as a screw. FIG. 1 is a top view, a front view, and a bottom view showing a configuration example of the internal fixation device of the present invention. FIG. 2 is an explanatory diagram showing an example of use of the internal fixation device of the present invention from a bird's-eye view. FIG. 3 is an explanatory diagram showing the solution principle of the present invention. FIG. 4 is an explanatory diagram showing a procedure of a usage example of the internal fixation device of the present invention. FIG. 5 is an explanatory diagram showing a cross-sectional structure to show a configuration example of the treatment device of the second embodiment of the present invention. FIG. 6 is an explanatory diagram showing an overview to show a configuration example of the tip of the inner tube. FIG. 7 is an explanatory diagram showing a cross-sectional structure to show a configuration example of the tip of the inner tube. FIG. 8 is an explanatory diagram showing a schematic diagram of a treatment procedure (first half) using the treatment device of the present invention. FIG. 9 is an explanatory diagram showing a schematic diagram of a treatment procedure (second half) using the treatment device of the present invention. 1. Overview of the embodiment First, a summary of representative embodiments disclosed in the present application will be described. Reference numerals in parentheses in the summary of the representative embodiments refer only to components included in the concept of the components to which they are attached. [1] An internal fixation device with a spiral groove on the shaft (Figure 1) A representative embodiment disclosed in the present application is an internal fixation device (1) that is inserted from the pedicle into bone cement filled in the vertebral body, and is equipped with a cylindrical shaft (2) and a connection portion (3) at the distal end of the shaft that can be connected to a driver, and the shaft has a spiral groove (4) on the proximal side. This makes it possible to provide an internal fixation device that is inserted from the pedicle into bone cement that has been filled in advance within the vertebral body, and that can be easily removed while maintaining the same level of internal fixation performance as a screw. [2] The groove is deeper at the tip In the internal fixation device of [1], the groove is deeper on the proximal side of the shaft than on the distal side. As a result, when the internal fixation device (1) is screwed in, bone cement smoothly enters the groove (4) and is firmly fixed, while when removing the device, the force required for removal can be reduced by applying a rotation in the opposite direction to that used for screwing in. [3] The tip of the shaft is narrower In the internal fixation device (1) of [1] or [2], the shaft has a tapered portion (7) at the proximal end, the diameter of which gradually decreases from the central portion. This reduces the force required to screw in and remove the internal fixation device (1). [4] A screw thread on the distal side of the shaft In any one of the internal fixation devices (1) of [1] to [3], the shaft has the groove on the proximal side and a convex thread (5) on the distal side. This firmly fixes the screw thread (5) to the pedicle and provides a stable hold for the bone cement. [5] The groove and thread have the same lead In the internal fixation device (1) of [4], the groove (4) and the thread (5) are formed with equal leads to each other. As a result, as in [1], when the internal fixation device (1) is screwed in, the bone cement smoothly enters the groove (4) and is firmly fixed, while the force required for removal can be reduced by applying a rotation in the opposite direction to that used for screwing in. The lead is the distance traveled in the direction of the central axis per unit number of rotations. By aligning the leads of the groove (4) and the thread (5), strong resistance is not applied to one side, and the resistance is distributed. Here, "equal" does not stipulate equality in mathematical strictness, but rather an error is allowed to the extent that the resistance is appropriately distributed. [6] Grooves have fewer threads than threads. In the internal fixation device (1) of [5], the number of grooves is smaller than the number of threads. This allows the bonding strength between the internal fixation device (1) and bone cement to be appropriately designed while strengthening the fixation with the pedicle by the thread (5). As mentioned in [5] above, it is preferable to make the lead of the groove (4) and the thread (5) equal. In that case, a new problem arises of appropriately setting the contact area with the object, but this problem can be solved by designing the number of threads independently. [7] Treatment instrument for operating the internal fixation instrument of the present invention (Figs. 5, 6, and 7) A representative embodiment disclosed in the present application is a treatment instrument (100) including a cylindrical driver (40) connectable to an internal fixation instrument (1) that is inserted from the pedicle into bone cement filled in a vertebral body, and an inner cylinder (30) that can be inserted into the driver, and is configured as follows. The internal fixation device includes a cylindrical shaft (2) and a connection portion (3) at the distal end of the shaft that can be connected to the driver, and has a through hole (6) through which the inner cylinder can pass along the central axis from the distal end to the proximal end. The shaft has a spiral groove (4) on the proximal side. The driver has a through hole through which the inner cylinder can pass from the head to the tip along the central axis, and can be fitted into the connection part (3) of the internal fixed device and connected to the internal fixed device by moving the driver along the central axis, and can transmit a rotational force around the central axis to the internal fixed device. The inner tube has a connection portion (35) that is inserted into the through hole of the driver from the distal end of the driver and connected to the driver at the distal end, and a tip portion (32) that protrudes proximally beyond the tip of the internal fixation device connected to the driver, and has an elastic tongue (31) with a convex portion (33) at its tip portion. When the inner tube is inserted into the driver and the internal fixation device, the tongue is bent toward the central axis and the inner tube can move in the central axis direction within the through holes of the driver and the internal fixation device. Also, when the inner tube is inserted into the through hole of the driver, connected to the driver at the distal end, and further connected to the internal fixation device, the protrusion comes into contact with the tip of the internal fixation device. This provides a treatment instrument (100) suitable for inserting the internal fixation instrument (1) of [1] to [6] from the pedicle into the bone cement filled in the vertebral body. When the driver (40) with the inner tube (30) inserted therein is connected to the internal fixation instrument (1), they are integrated. This integration is achieved by connecting the driver (40) and the internal fixation instrument (1) at the connection part (3) of the internal fixation instrument, and by connecting the inner tube to the distal end of the driver and contacting and holding the protruding part of the tongue against the tip of the internal fixation instrument. [8] Fixation by inserting guide pins In the treatment instrument (100) of [7], the inner tube has a through hole through which a guide pin (15, not shown in Figures 5 to 7) can pass from the distal end to the proximal end along the central axis, and when the inner tube is inserted into the through hole of a driver (40) and connected to the driver at the distal end and further connected to the internal fixation instrument (1), the guide pin is further inserted into the inner tube, thereby restricting the multiple tongues from bending in the direction of the central axis, and bringing the convex portion into contact with the tip of the internal fixation instrument, restricting the movement of the inner tube back along the central axis toward the through hole of the internal fixation instrument. This will further strengthen the integration described in [7]. [9] Tapping thread at the tip of the inner cylinder In the treatment instrument (100) of [7] or [8], the inner cylinder has a screw thread (34) that can be tapped onto the outer circumferential surface of the tip portion. As a result, when the integrated treatment instrument (100) described in [7] is operated to insert the internal fixation instrument (1) from the pedicle into the vertebral body, the internal fixation instrument can be smoothly delivered to the vertebral body even if the diameter of the bone hole formed in the pedicle is small.

[10] The proximal end of the internal fixation device is blunt. In the treatment instrument (100) of [7] or [8], the internal fixation instrument has a blunt proximal end. This makes it possible to reduce the risk of damaging the balloon (11) even when a balloon catheter (12) is inserted into the through hole (6) of the internal fixation device (1) and the balloon (11) is passed through it.

[11] The internal fixation device has a groove on the proximal side and a thread on the distal side. In the treatment instrument (100) of [7] or [8], the shaft of the internal fixation instrument has the groove on the proximal side and a convex screw thread (5) on the distal side. As a result, similar to [4], the screw thread (5) is firmly fixed to the pedicle and the bone cement is stably held in place.

[12] The groove and thread have the same lead In the treatment instrument (100) of

[11] , the groove and the thread of the internal fixation instrument are formed with equal leads to each other. As a result, similar to [5], when the internal fixation device (1) is screwed in, the bone cement smoothly enters the groove (4) and is firmly fixed, while when removing the device, the force required for removal can be reduced by applying a rotation in the opposite direction to that used when screwing in the device.

[13] Grooves have fewer threads than threads. In the treatment instrument (100) of

[12] , the number of grooves of the internal fixation instrument is smaller than the number of threads of the screw. This makes it possible to appropriately design the bonding strength between the internal fixation device (1) and bone cement while strengthening the fixation with the pedicle by the screw threads (5), similarly to [6]. 2. Details of the embodiment The embodiment will now be described in further detail. [Embodiment 1] 1A, 1B and 1C are a top view, a front view and a bottom view showing an example of the configuration of an internal fixation device of the present invention. The back view and the left and right side views are omitted because they are the same as the front view (b) except that the groove 4 and the thread 5 are arranged at positions extended from the front view (b). The internal fixation device 1 includes a cylindrical shaft 2 and a connecting portion 3 at the distal end of the shaft 2 that can be connected to a driver, and the shaft 2 has a spiral groove 4 on the proximal side. The shaft 2 is preferably cylindrical as illustrated in the figure and has a through hole 6 that penetrates from the distal end to the proximal end along the central axis. The through hole 6 can be configured to allow a guide pin to pass through. As described later, the through hole 6 may be configured to allow a bone drilling tool, a balloon catheter, a bone cement injector, or the like to pass through. The connecting portion 3 is configured as a hexagonal column-shaped recess to engage with, for example, a hexagonal wrench as illustrated in the figure so that the entire internal fixation device 1 can be rotated by engaging with a driver (not shown). Fig. 2 is an explanatory diagram showing an example of use of the internal fixation device 1 from a bird's-eye view. When a patient is in a standing position, the spine is composed of multiple vertebral bodies 20 stacked one on top of the other, and Fig. 2 shows one of the vertebral bodies as seen through from above and below. The vertebral bodies 20 are supported by a pair of left and right pedicles 21, which are connected by a vertebral arch 22. The area surrounded by the vertebral bodies 20, the pedicles 21, and the vertebral arch 22 is the spinal canal 23. A compression fracture is a disease in which a vertebral body is compressed and collapsed by a force in the vertical direction. In a treatment using the internal fixation device 1 of the present invention, as described later with reference to Fig. 4, a space is returned to the vertebral body 20, bone cement 10 is injected, and the internal fixation device 1 is inserted (screwed) before the bone cement hardens to support the vertebral body from the pedicle 21 side. The internal fixation device 1 is inserted from the pedicle 21 into the bone cement 10 that has been filled in the vertebral body 20 beforehand, and when the bone cement 10 hardens, it is supported by the internal fixation device 1 from the pedicle 21 and fixed in the vertebral body 20. 3 is an explanatory diagram showing the principle of the solution of the present invention. The upper side (a) shows a cross section of the state of joining of the bone cement 10 and the shaft 2 having the groove 4, and the lower side (b) shows a cross section of the state of joining when it is assumed that the shaft 2 has a thread instead of the groove 4. Since it is different from the thread 5 on the distal side of the shaft 2, the reference number 5 is not attached. Here, the groove 4 is recessed in the central axis direction from the outer circumferential surface of the shaft 2, and the thread is convex outward from the outer circumferential surface of the shaft 2. In the case where the shaft 2 has a thread (b), when the thread is screwed into the bone cement 10, the thread taps the bone cement 10, that is, the thread advances while pushing the bone cement 10 around the protruding part, so that the surface of the thread is in close contact with the bone cement 10. When the thread taps the bone cement 10, in addition to the driving force applied to the shaft 2, a driving force is also applied from the rotational force of the tapping. On the other hand, when the shaft 2 has the groove 4 (a), the groove 4 does not have the effect of tapping the bone cement 10, so that the bone cement 10 penetrates into the groove 4 solely due to the viscosity of the bone cement 10. Therefore, even if the viscosity is high, the bone cement 10 does not necessarily reach the bottom of the groove 4, and a gap may remain as illustrated in the figure. In this way, the action of the thread and the groove on the bone cement is completely different, and as a result, the degree of adhesion is also significantly different. By forming the groove 4 in the shaft 2, it becomes easier to remove compared to when a thread is formed, but it can be made more difficult to remove compared to when only the shaft 2 is formed. Therefore, by appropriately adjusting the length, number, and depth of the groove 4, it is possible to realize an appropriate ease of removal. Although the groove 4 shown in the figure is a triangle with a pointed bottom, its shape can be any shape, and the angle of the bottom can be any angle, such as an acute angle or an obtuse angle other than the right angle shown in the example, and the bottom can be flat or arc-shaped. Also, the thread used for comparison has a sharp tip, but the above-mentioned solution principle is the same even if the corners are smoothly chamfered. The depth of the groove 4 of the internal fixation device 1 may be uniform, but it is more preferable to make the proximal side (tip side) deeper than the distal side (head side) of the shaft 2. When the internal fixation device 1 is screwed into the bone cement 10 while rotating along the spiral of the groove 4, the proximal side (tip side) that comes into contact with the bone cement 10 is deeper first, so that the bone cement 10 enters deeper into the groove 4, and as it is screwed in, it is sent along the spiral of the groove 4 to the shallower distal side (head side) of the groove 4, so that the bone cement 10 smoothly enters the groove 4 and is firmly fixed. On the other hand, when removing the internal fixation device 1, it is separated from the bone cement 10 while rotating in the opposite direction along the spiral of the groove 4, so that the force required for removal can be reduced. It is more preferable that the shaft 2 of the internal fixation device 1 has a tapered portion 7 whose diameter gradually decreases from the center toward the proximal end. When the internal fixation device 1 is screwed into the bone cement 10, the resistance when the internal fixation device 1 is first inserted into the bone cement 10 is reduced, and the force required to remove the internal fixation device 1 is also reduced. The distal side (head side) of the shaft 2 of the internal fixation device 1 may be provided with a screw thread 5. The screw thread 5 is a helical convex portion that protrudes outward from the outer circumferential surface of the shaft 2, and has the function of tapping the surrounding bones and advancing the internal fixation device 1 (shaft 2) along the central axis as it rotates. As illustrated in Fig. 2, the screw thread 5 advances by tapping the pedicle 21, firmly fixing the internal fixation device 1 and stably supporting the bone cement 10 in the vertebral body 20 into which the shaft 2 is inserted. It is preferable that the threads 5 and the grooves 4 are formed with equal leads. The lead is the distance traveled along the central axis relative to the amount of rotation of the shaft 2, so it is desirable that the distance traveled by the threads 5 tapping the pedicle 21 while advancing the shaft 2 is equal to the distance traveled by the shaft 2 along the spiral of the grooves 4 when screwed into the bone cement 10. However, precise matching is not always necessary, and they can be intentionally made different. For example, by making the lead of the groove 4 larger than the lead of the thread 5, after the groove 4 at the tip of the shaft 2 is partially screwed into the bone cement 10 and the thread 5 starts tapping the pedicle, a force can be applied to move the bone cement 10 closer to the pedicle as the internal fixation device 1 (shaft 2) rotates. The number of threads can be different between the groove 4 and the thread 5. For example, the number of threads of the groove 4 may be smaller than the number of threads of the thread 5. This allows the bonding force between the internal fixation device 1 and the bone cement 10 to be appropriately designed while strengthening the fixation to the pedicle 21 by the thread 5. As described above, it is preferable to make the groove 4 and the thread 5 have the same lead. In that case, a new problem arises of appropriately setting the contact area with the object, but this problem is solved by designing the number of threads independently. By reducing the number of threads of the groove 4, the contact area with the bone cement 10 can be reduced, and the force required for removal can be weakened. On the other hand, by increasing the contact area between the pedicle 21 and the thread 5, the fixation of the internal fixation device 1 to the pedicle 21 can be strengthened. By optimizing the number of threads instead of the pitch, the relationship between the bone cement 10 and the groove 4 and the relationship between the pedicle 21 and the thread 5 can be independently optimized. Fig. 4 is an explanatory diagram showing a procedure of an example of using the internal fixation device 1 of the present invention. As shown in Fig. 2, the spine is composed of a plurality of vertebral bodies 20 stacked one on top of the other when the patient is in a standing position, and the vertebral bodies 20 are supported by a pair of left and right pedicles 21, which are connected by a vertebral arch 22. Fig. 4 shows a cross section from the patient's body surface (not shown) through one pedicle 21 to the vertebral body 20, with the body surface assumed to be on the upper side. Step A: The skin on the side where the affected vertebral body 20 can be accessed is incised, and a bone hole 19 is formed in the pedicle 21 to reach the vertebral body 20. The diameter of the bone hole 19 may be a size that allows the shaft 2 of the internal fixation instrument 1 to be inserted or a bone hole that allows a guide pin (described later) to be inserted, and the length is a length that generally reaches the vertebral body 20. Step B: The shaft 2 of the internal fixation device 1 is inserted into the formed bone hole 19. A guide pin (not shown) may be inserted into the vertebral body 20 from outside the body through the bone hole 19, and the internal fixation device 1 may be inserted along the guide pin. The part of the shaft 2 without any protrusions such as the thread 5 may be inserted into the bone hole 19, and the part with the thread 5 may stop outside the pedicle 21. A balloon catheter 12 is inserted into the through hole 6 of the shaft 2 of the internal fixation device 1, and its tip is brought into the vertebral body 20, and the balloon 11 at the tip is inflated to secure a space inside the vertebral body 20. At this time, a driver 14 (not shown) may be connected to the connection part of the head 3 of the internal fixation device 1, and the thread 5 may be slightly screwed into the pedicle 21 in advance. Before inserting the balloon catheter 12, a perforator or a bone drilling tool may be introduced into the vertebral body 20 from outside the body through the bone hole 19 to drill the bone from inside the vertebral body 20. It is more preferable that the tip of the internal fixation device 1 is smoothly chamfered. As described above, in step B, in which the balloon 11 is introduced into the vertebral body 20 through the through-hole 6 of the internal fixation device 1, inflated, and then removed, the risk of the balloon 11 touching and damaging the tip of the internal fixation device 1 can be reduced. Step C: Insert the cement injector 13, instead of the balloon catheter 12, into the through hole 6 of the shaft 2 of the internal fixation instrument 1, bring the tip of the cement injector 13 into the vertebral body 20, and inject the bone cement 10 from the tip of the cement injector 13 into the vertebral body 20. At this time, a driver 14 (not shown in [c]) may be connected in advance to the connection part of the head 3 of the internal fixation instrument 1, and the cement injector 13 may be introduced to the affected vertebral body 20 through a through hole provided along the central axis of the driver 14 and communicating with the through hole 6 of the connected internal fixation instrument 1, as described above. Step D: The driver 14 is connected to the connection part of the head 3 of the internal fixation device 1, and the screw thread 5 is screwed into the pedicle 21. At this time, the tip (proximal end) of the internal fixation device 1, the part where the groove 4 of the shaft 2 is formed, is screwed into the bone cement 10. The driver 14 is removed from the internal fixation device 1, the opening is sutured, and the surgery is completed. In Fig. 4, the driver 14 is not shown in [B] and [C], but as described above, it is preferable to provide a through hole communicating with the through hole 6 of the internal fixation device 1 in the driver 14 so that steps B and C can be carried out with the driver 14 attached to the internal fixation device 1 from the beginning of step B. A drill needle, a bone excavator (not shown), a balloon catheter 12, and a cement injector 13 can be sequentially introduced into the vertebral body 20 through the through hole communicating from the driver 14 to the internal fixation device 1, and excavation of the bone in the vertebral body 20, expansion of the space by the balloon, and filling of the bone cement 10 can be performed with the driver 14 attached from the beginning. This can reduce the number of steps to replace the instruments, shorten the operation time, and minimize the time from filling the bone cement 10 to screwing in the internal fixation device 1, so that the internal fixation device 1 can be screwed in with plenty of time before the bone cement 10 hardens. [Embodiment 2] The internal fixation device 1 of the present invention is more preferably used in combination with the treatment device 100 according to the above-mentioned international patent application (PCT / JP2022 / 036147). Fig. 5 is an explanatory diagram showing the present embodiment 2 as an example of use of the internal fixation device 1. Note that Fig. 5 is drawn with the scale of the central axis direction (vertical direction on the page) compressed and the direction along the patient's body surface (horizontal direction on the page) emphasized. The treatment device 100 includes a cylindrical driver 40 that can screw the internal fixation device 1 into the pedicle 21, and an inner cylinder 30 that is inserted into the driver 40, and is configured as follows. The tip of the internal fixation device 1 is blunt so that a soft vertebral body excavation device such as a balloon can be inserted and removed, and the through hole 6 has a diameter that allows the inner cylinder 30 to pass along the central axis from the head 3 to the tip. The driver 40 is configured to be fitted into the connection part of the head 3 of the internal fixation device 1 by moving it along the central axis, and to be connected to the internal fixation device 1, so that a force in the rotational direction around the central axis can be transmitted to the internal fixation device 1. For example, the tip of the driver 40 may be formed in the shape of a hexagonal wrench (hexagonal column), and the connection part of the head 3 of the internal fixation device 1 may be formed with a hexagonal groove (recess). The shape of the tip of the driver 40 and the shape of the connection part of the head 3 of the internal fixation device 1 may be other than hexagonal, such as a star shape, as long as they are engaged simply by being inserted. If the driver 40 is slid along the central axis into the connection part of the head 3 of the internal fixation device 1, the tip of the driver 40 fits into the connection part of the head 3 of the internal fixation device 1, and the internal fixation device 1 can be screwed in by the driver 40, and the driver 40 can be easily removed by pulling out the driver 40. The inner cylinder 30 has a tip portion 32 that is inserted from the distal end of the driver 40 through the through holes of the driver 40 and the internal fixation device 1 and protrudes proximally beyond the tip of the internal fixation device 1. The inner cylinder 30 is connected integrally with the driver 40 and the internal fixation device 1 with the tip portion 32 protruding proximally beyond the tip of the internal fixation device 1. This makes it possible to provide a treatment instrument suitable for surgical procedures such as artificial disc replacement, spinal fixation, vertebroplasty, and pedicle plasty for spinal diseases. An example of a structure for integrating the internal fixation device 1, the driver 40, and the inner cylinder 30 will be described. As shown in FIG. 5, the driver 40 and the inner cylinder 30 are configured so that they can be connected at their distal ends. The distal end of the driver 40 is provided with a cylindrical connection part 45 having a male screw 46 thread on the outer circumferential surface, and the distal end of the inner cylinder 30 is provided with a groove-shaped connection part 35 capable of accommodating the cylinder, and a female screw 36 that engages with the male screw 46 is formed. The relationship of the projections and recesses and the relationship of the male screw and the female screw may be reversed, or other connection mechanisms may be used. Also, as exemplified in FIG. 5, the driver 40 is provided with a handle 47, and the inner cylinder 30 is provided with a handle 37, and it is preferable that they are integrated so that they are easy to grip when connected. Even if they are connected with a screw as in this example, a latch mechanism (not shown) may be further provided to prevent the connection from coming loose. As shown in FIG. 6, the tip (proximal end) of the inner tube 30 is divided into a plurality of tongues 31 in the direction along the central axis, and each of the plurality of tongues 31 has a protruding portion 33 in the direction away from the central axis. The protruding portion 33 has a notch function to prevent the internal fixation device 1 from slipping out of the inner tube 30 as described later, so the reference numeral 33 is referred to as a notch. The plurality of tongues 31 are formed, for example, by dividing the cylindrical inner tube 30 from the tip side with slits. The number of divisions is arbitrary, for example, four, six, two, three, etc. In addition, in order to provide appropriate elasticity, some processing (for example, heat treatment, processing to reduce thickness, processing to bond metal with high elasticity) may be performed. The elasticity of the tongues 31 is designed to have an appropriate deflection. For example, when the inner tube 30 passes through the through hole of the driver 40, the notch 33 is pressed against the inner wall of the through hole, bending in the direction of the central axis to allow the inner tube 30 to pass, and when the notch 33 comes out proximal to the tip of the internal fixation device 1, the bending returns to its original state and the notch 33 catches on the tip of the internal fixation device 1. If the notch 33 has a smooth shape, it can be configured so that even after the notch 33 comes out from the tip of the internal fixation device 1, the force for pulling out the inner tube 30 can pull the notch 33 into the through hole 6 of the internal fixation device 1, and the tongue piece 31 can be bent again in the direction of the central axis, allowing the inner tube 30 to be pulled out. 7 is an explanatory diagram showing a cross-sectional structure of the inner tube 30 to show a configuration example of the tip portion 32. As shown in (a) on the upper side, when the inner tube 30 is inserted into the internal fixation device 1 and the connected driver 40, the above-mentioned tongue piece 31 is bent toward the central axis, and can move in the central axis direction within the through hole. As shown in (b) on the lower side, when the inner tube 30 is inserted into the internal fixation device 1 and the connected driver 40, and the distal end is connected to the driver 40 as described above, the tip portion 32 protrudes proximally beyond the tip of the internal fixation device 1, and the tongue piece 31 is restored to its original bending state, so that the notch 33 comes into contact with the tip of the internal fixation device 1. In this state, when the guide pin 60 is inserted into the inner tube 30, the tongue piece 31 cannot bend in the direction of the central axis even if an attempt is made to pull out the inner tube 30, and the notch 33 protrudes outward beyond the diameter of the through hole 6 of the internal fixation device 1, restricting the movement of the inner tube 30 in the distal direction along the central axis, i.e., returning toward the through hole 6 of the internal fixation device 1, resulting in a stronger integration. Simply put, when the internal fixation device 1 tries to come out of the inner tube 30, the notch 33 comes into contact with the tip of the internal fixation device 1, restricting it from coming out. This makes the integration stronger. It is more preferable that the tip portion 32 of the inner cylinder 30 is provided with a thread 34 that can be tapped on the outer circumferential surface. The thread 34 is preferably formed at a position that smoothly connects with the inclined portion of the internal fixation device 1 when the internal fixation device 1, the driver 40, and the inner cylinder 30 are integrated as described above. A method of treatment for spinal diseases using the treatment instrument 100 of the present invention, such as artificial disc replacement, spinal fusion, vertebroplasty, and pedicle plasty, will be described. 8 and 9 are explanatory diagrams that show a typical procedure of treatment using the treatment instrument 100 of the second embodiment, with FIG. 8 showing the first half of the procedure and FIG. 9 showing the latter half. Although FIGS. 8 and 9 show vertebroplasty, the method of inserting the internal fixation instrument 1 into the vertebral body is similar to that of spinal fixation and vertebral body reinforcement surgery in artificial disc replacement (not shown). FIGS. 8 and 9 show a typical cross section of the affected area of ​​a patient, from the outside of the skin 24 through the pedicle 21 to the vertebral body 20, with the upper side being the distal side and the lower side being the proximal side. The scale of the central axis direction (vertical direction on the page) is compressed, and the direction along the patient's body surface (horizontal direction on the page) is emphasized. The pedicle 21 is located on both the left and right sides of the vertebral body 20, so the same treatment is performed on one vertebral body 20 from the left and right, but FIGS. 8 and 9 show one of them. First step ([1]): The subcutaneous tissue from the skin 24, which is the surface of the patient's back, to the affected vertebral body 20 is incised and perforated, and a guide pin 15 is introduced through the pedicle 21 to the vertebral body 20. Second step ([2]): The internal fixation device 1 and the driver 40 are connected, and the inner tube 30 is inserted into the through-hole on the inside thereof so that the tip of the internal fixation device 1 protrudes from the tip of the internal fixation device 1. The inner tube 30 is then placed over the guide pin 15, and inserted into the patient's body along the guide pin 15. Third step ([3]): With the internal fixation device 1, the driver 40, and the inner cylinder 30 connected together, they are further pushed in the proximal direction along the guide pin 15, and the tip of the inner cylinder 30 and the internal fixation device 1 are screwed into the pedicle 21. Fourth step ([4]): After the tip of the internal fixation device 1 is screwed in until it reaches the vicinity of the entrance of the vertebral body 20, the guide pin 15 is removed. At this time, the notch 33 of the inner tube 30 contacts the tip of the internal fixation device 1 and prevents the inner tube 30 from being pulled out naturally, but by pulling out the guide pin 15, the tongue piece 31 is easily bent in the central axis direction by the force of pulling out the inner tube 30, so that the inner tube 30 can be pulled out. Fifth step ([5]): Remove the inner cylinder 30. At this time, the driver 40 is simply inserted into the head 3 of the internal fixation device 1, so it is held down so that it does not come out. Although not shown in the figure, in this step, if necessary, a vertebral body excavation device may be introduced through the driver 40 and the through-hole of the internal fixation device 1 to excavate the inside of the vertebral body 20 in order to fill the vertebral body with cement for reinforcement. Sixth step ([6]): The balloon catheter 12 is introduced into the vertebral body 20 through the driver 40 and the through-hole of the internal fixation device 1, and the balloon 11 is inflated inside the vertebral body 20. For example, the balloon 11 is inflated by injecting a contrast agent through the balloon catheter 12 and applying pressure. The purpose is to return the vertebral body 20 to its original size when the vertebral body 20 has a compression fracture due to osteoporosis or the like. Seventh step ([7]): The balloon catheter 12 is removed from the driver 40 and the through-hole of the internal fixation device 1, and instead the cement injector 13 is inserted to inject the bone cement 10 into the vertebral body 20. Since the volume of cement that can be filled with the cement injector 13 at one time is about 1.5 ml, for example, in the case of vertebroplasty for a fracture, the cement is repeatedly pumped about three times from each side, a total of six to seven times, to fill about 10 ml of bone cement 10 into the vertebral body 20. When applied to spinal fixation surgery and vertebral reinforcement surgery in artificial disc replacement surgery other than vertebroplasty, the amount of cement filled is adjusted according to the condition of the bone. Eighth step ([8]): The driver 40 and the cement injector 13 are pulled out from the through hole of the internal fixation device 1. Ninth step ([9]): Using the driver 40, the internal fixation device 1 is screwed into the filled bone cement 10. Tenth step (

[0010] ): The driver 40 is withdrawn, the incised skin 24 is sutured, and the treatment is completed. As described above, according to the treatment instrument 100, the internal fixation instrument 1 can be screwed into the filled bone cement 10 immediately after the bone cement 10 is filled, and therefore the treatment instrument 100 is suitable for surgical procedures such as spinal fixation surgery, vertebral reinforcement surgery in artificial disc replacement surgery, vertebroplasty, and pedicle formation surgery. The filled bone cement 10 is soft enough that the internal fixation device 1 can be screwed in without tapping using the screw thread 34 of the tip portion 32 of the inner cylinder 30. Similarly, the internal fixation device 1 can be screwed into the pedicle 21 without tapping using the tip portion 32 of the inner cylinder 30. The treatment instrument 100 is also suitable for removing the internal fixation instrument 1. After incising the affected area and drilling a hole up to the head of the screw, the guide pin 15 is inserted into the internal fixation instrument 1, and the driver 40 is introduced along the guide pin 15 into the internal fixation instrument 1, and the driver 40 can be connected simply by pushing in the tip. After that, the internal fixation instrument 1 can be pulled out by rotating the driver 40. The invention made by the inventor has been specifically described above based on an embodiment, but it goes without saying that the invention is not limited thereto and can be modified in various ways without departing from the spirit of the invention. The present invention relates to a cylindrical internal fixation device for medical use, and is particularly suitable for use in surgery for internal fixation of an affected vertebral body. 1 Internal fixation device 2 Shaft 3 Head (driver connection part) 4 Groove 5 Thread 6 Through hole 7 Slope section 10. Bone cement 11. Balloon 12 Balloon catheter 13 Cement injector 14. Driver 15 Guide pin 19 Bone hole 20 vertebral body 21 pedicle 22 vertebral arch 23 Spinal canal 24 Skin 30 Inner cylinder 31 tongue of inner cylinder 32 Tip of inner cylinder 33 Notch 34 Thread at tip of inner cylinder 35 Driver connection 36 Female thread 37 Inner barrel handle 40 Driver 45 Connection with inner cylinder 46 Male thread 47 Driver's handle 100 Treatment equipment

Claims

1. An internal fixation device to be inserted from the pedicle into bone cement filled in a vertebral body, the internal fixation device comprising a cylindrical shaft and a connection portion at the distal end of the shaft that can be connected to a driver, the shaft having a spiral groove on the proximal side.

2. The internal fixation device according to claim 1, wherein the groove is deeper on the proximal side of the shaft than on the distal side.

3. An internal fixation device according to claim 1 or 2, wherein the shaft has a tapered portion at the proximal end, the diameter of which gradually decreases from the central portion.

4. An internal fixation device according to any one of claims 1 to 3, wherein the shaft has the groove on the proximal side and a convex thread on the distal side.

5. The internal fixation device according to claim 4, wherein the groove and the thread are formed with equal leads to each other.

6. The internal fixation device according to claim 5, wherein the number of grooves is smaller than the number of threads.

7. A treatment device including a cylindrical driver connectable to an internal fixation device that is inserted from the pedicle into bone cement filled in a vertebral body, and an inner tube that can be inserted into the driver, wherein the internal fixation device has a cylindrical shaft and a connecting portion at the distal end of the shaft that can be connected to the driver, and has a through hole through which the inner tube can pass from the distal end to the proximal end along a central axis, and the shaft has a spiral groove on the proximal side, the driver has a through hole through which the inner tube can pass from the head to the tip along the central axis, and is configured to be fitted into the connecting portion of the internal fixation device and connected to the internal fixation device by moving along the central axis, and to be able to transmit a rotational force around the central axis to the internal fixation device, the inner tube has a connecting portion that is inserted from the distal end of the driver into the through hole and connected to the driver at the distal end, and a tip portion that protrudes proximally beyond the tip of the internal fixation device connected to the driver, and the inner tube has an elastic tongue piece with a protrusion at its tip, When the inner tube is inserted into a driver and an internal fixation device, the tongue bends toward the central axis and the inner tube can move in the central axis direction within the through holes of the driver and the internal fixation device, and when the inner tube is inserted into the through hole of the driver and connected to the driver at its distal end and further connected to the internal fixation device, the convex portion comes into contact with the tip of the internal fixation device.

8. A therapeutic instrument as claimed in claim 7, wherein the inner tube has a through hole through which a guide pin can pass from the distal end to the proximal end along the central axis, and when the inner tube is inserted into the through hole of a driver and connected to the driver at its distal end and also connected to an internal fixation device, the guide pin is inserted into the inner tube to restrict the multiple tongues from bending in the direction of the central axis, and the convex portion is brought into contact with the tip of the internal fixation device, restricting the movement of the inner tube back along the central axis toward the through hole of the internal fixation device.

9. A medical device according to claim 7 or 8, wherein the inner cylinder is provided with a thread that can be tapped on the outer circumferential surface of the tip portion.

10. The medical device according to claim 7 or 8, wherein the internal fixation device has a blunt proximal end.

11. A treatment instrument according to claim 7 or 8, wherein the shaft of the internal fixation instrument has the groove on a proximal side and a convex screw thread on a distal side.

12. The medical device according to claim 11, wherein the groove and the thread of the internal fixation device are formed with equal leads to each other.

13. The medical device according to claim 12, wherein the number of grooves of the internal fixation device is smaller than the number of threads of the screw.

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