Internal fixation devices and therapeutic devices

Abstract

This device provides an internal fixation device that is inserted from the pedicle into bone cement pre-filled within the vertebral body, maintaining an internal fixation performance comparable to that of a screw, while being easily removable. [Solution] An internal fixation device that is inserted from the pedicle and supports bone cement filled into the vertebral body, comprising a cylindrical shaft that can be rotated by connecting a screwdriver to its distal end. The shaft has an inclined portion whose diameter gradually decreases towards the proximal end, the inclined portion has a spiral groove into which the bone cement filling the surrounding area enters, and the distal side has a convex screw thread for engaging with the pedicle.

Description

Technical Field

[0001] The present invention relates to a medical cylindrical internal fixation device and a treatment instrument for operating the same, and in particular, it can be suitably used for internal fixation surgery of a vertebral body which is an affected part.

Background Art

[0002] As treatment methods for spinal compression fractures, vertebroplasty and spinal fixation are known. The spine consists of stacked vertebral bodies and the vertebral arches, pedicles, articular processes, etc. that support them. The vertebral body is a cylindrical bone that sandwiches the nucleus pulposus and the annulus fibrosus surrounding it up and down, and is supported by two left and right pedicles extending from the vertebral arch. The vertebral arches are connected up and down by the upper and lower articular processes to support the vertebral body via the pedicles and form 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 of filling the vertebral body with medical cement is adopted. Spinal fixation is a surgical method of fixing the crushed vertebral body and the healthy vertebral bodies above and below it with an instrument. Screws are screwed into the crushed vertebral body and the healthy vertebral bodies above and below it from the pedicles respectively, and the heads of the screws are connected to a rod passed in the vertical direction to each other for fixation. If the symptoms are mild, vertebroplasty is adopted, but if the symptoms are severe, spinal fixation is necessary.

[0003] Various screws used in these treatments have been proposed.

[0004] Patent Document 1 discloses a medical screw provided with a longitudinal through-hole along the central axis and an opening on the side surface communicating with the through-hole. An injection instrument such as a syringe is attached to the head of the screw, and bone cement or a bioactive substance is injected into the surrounding bone through the opening on the rough surface from the through-hole, and the surrounding bone is reinforced (

[0053] ~

[0057] , Figs. 6-8).

[0005] Patent Document 2 discloses a medical screw that can be easily removed from a fracture site into which it has been screwed. The medical screw has a hollow section formed from the head to the tip along the central axis, and threads are formed on the side so that it can be screwed into the bone. Near the inner tip of the hollow section of the screw, there is a reverse thread (reverse internal thread section), and it is possible to pull it out by using an extraction tool that has a tip that engages with this reverse internal thread section. More specifically, the extraction tool is inserted from the hollow section, the tip engages with the reverse internal thread section of the screw and integrates with it, and the extraction tool is rotated to pull the screw out of the body. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] US release 2011 / 0040337A1 [Patent Document 2] Japanese Patent Publication No. 2016-209295 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The inventors of this invention have identified a problem in the lack of sufficient development of medical instruments and screws suitable for surgical procedures that combine vertebroplasty and pedicleoplasty as described above. To solve this problem, they have invented a treatment instrument and filed an international application as PCT / JP2022 / 036147. This invention is a treatment instrument integrated with a screw having a through hole along its central axis and tappable threads on its side. The instrument is configured so that a screwdriver can be attached to the head of the screw, bone cement can be injected into the affected area through the through hole of the screw, and then the screw can be screwed into the bone cement. After injecting the bone cement, there is no need to reattach the screwdriver, and the screwdriver can be operated as is, so the screw can be quickly screwed in before the bone cement hardens.

[0008] The inventors noticed that if it becomes necessary to remove a screw after the bone cement has hardened, there is a risk that the screw may be too tightly embedded in the bone cement, making it difficult to remove. While it is generally unlikely that a screw will need to be removed after surgery, complications such as postoperative infections at the surgical site cannot be completely ruled out. Therefore, the inventors believed that enabling screw removal would be beneficial in treating postoperative complications.

[0009] On the other hand, conventional screws, such as those described in Patent Document 1, are not designed to be screwed into pre-injected bone cement. Instead, after screwing the screw in, cement or the like is injected around it through an opening in the side wall to reinforce the surrounding bone. Therefore, the screw's threads are primarily engaged with bone, and it is thought that the screw can be removed relatively easily by rotating the screw in the reverse direction.

[0010] If removal is still expected to be difficult, a screw and removal tool designed for removal, such as those described in Patent Document 2, will be used.

[0011] The inventors of the present invention have conducted a more in-depth investigation into the risk of screws becoming too strongly embedded in bone cement, making them difficult to remove. They have found that this risk becomes apparent when the bond between the bone cement and the screw is stronger than the fusion between the bone cement and the surrounding bone or other affected tissue. In such cases, they have found that using a removal jig, such as the one described in Patent Document 2, does not solve the problem. While such a removal jig can strongly connect the screw and the driver and transmit strong force to the screw, thus assisting removal when the surrounding area is the patient's bone or other affected tissue, if the bond between the bone cement and the screw is stronger than the fusion between the bone cement and the surrounding bone or other affected tissue, as described above, the bone cement may separate from the surrounding affected tissue instead of the screw coming out of the bone cement, thus not assisting removal.

[0012] The objective of the present invention is to provide an internal fixation device that can be inserted from the pedicle into bone cement pre-filled within the vertebral body, while maintaining an internal fixation performance comparable to that of a screw and being easily removable.

[0013] The means for solving these problems are described below, but other problems and novel features will become apparent from the description and accompanying drawings in this specification. [Means for solving the problem]

[0014] According to one embodiment of the present invention, the following applies:

[0015] In other words, it is an internal fixation device inserted from the pedicle into bone cement filled inside the vertebral body, comprising a cylindrical shaft and a connecting portion at the distal end of the shaft that can be connected to a screwdriver, and the shaft having a spiral groove on its proximal side.

[0016] Here, "proximal" refers to the side closer to the midline of the patient's body, and "distal" refers to the side further away; these are medical terms. Bone cement is a medical cement, for example, primarily composed of calcium phosphate and polymethyl methacrylate, and hardens over time. [Effects of the Invention]

[0017] The effects obtained by the above embodiment can be briefly described below.

[0018] In other words, it is possible to provide an internal fixation device that is inserted from the pedicle into bone cement pre-filled inside the vertebral body, maintaining an internal fixation performance comparable to that of a screw, while being easily removable. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 shows a top view, front view, and bottom view illustrating an example of the configuration of the internal fixing device of the present invention. [Figure 2] Figure 2 is an explanatory diagram showing an example of use of the internal fixation device of the present invention from an overhead view. [Figure 3] Figure 3 is an explanatory diagram showing the solution principle of the present invention. [Figure 4] Figure 4 is an explanatory diagram showing an example of use of the internal fixation device of the present invention in steps. [Figure 5] Figure 5 is an explanatory diagram schematically showing a cross-sectional structure in order to show a configuration example of a treatment device which is a second embodiment of the present invention. [Figure 6] Figure 6 is an explanatory diagram showing an example of the configuration of the distal end of the inner cylinder from an overhead view in order to show the configuration example of the distal end of the inner cylinder. [Figure 7] Figure 7 is an explanatory diagram schematically showing a cross-sectional structure in order to show an example of the configuration of the distal end of the inner cylinder. [Figure 8] Figure 8 is an explanatory diagram schematically showing the procedure (first half) of treatment using the treatment device of the present invention. [Figure 9] Figure 9 is an explanatory diagram schematically showing the procedure (second half) of treatment using the treatment device of the present invention.

Embodiments for Carrying out the Invention

[0020] 1. Outline of Embodiment First, an outline of a typical embodiment disclosed in the present application will be described. The reference signs in the drawings referred to with parentheses in the outline description of the typical embodiment merely exemplify those included in the concept of the components to which they are attached.

[0021] 〔1〕Internal fixation device having a spiral groove on the shaft (FIG. 1) A typical embodiment disclosed in the present application is an internal fixation device (1) inserted from the pedicle into bone cement filled in a vertebral body, which includes a cylindrical shaft (2) and a connection portion (3) connectable to a driver at the distal end of the shaft, and the shaft has a spiral groove (4) on the proximal side.

[0022] This makes it possible to provide an internal fixation device that can be inserted from the pedicle into bone cement pre-filled within the vertebral body, maintaining an internal fixation performance comparable to that of a screw, while being easily removable.

[0023] [2] The groove is deeper towards the tip. In the internal fixing device of [1], the groove is deeper on the proximal side of the shaft than on the distal side.

[0024] This allows bone cement to smoothly enter the groove (4) when the internal fixation device (1) is screwed in, resulting in strong fixation, while the force required for removal can be reduced by applying the opposite rotation to the screwing-in rotation.

[0025] [3] The tip of the shaft is tapered. In the internal fixing device (1) of [1] or [2], the shaft has a sloping portion (7) at its proximal end that gradually decreases in diameter from the central portion.

[0026] This reduces the force required when screwing in the internal fixing device (1) and the force required when removing it.

[0027] [4] Threaded end of the shaft In any one of the internal fixing devices (1) from [1] to [3], the shaft has the groove on the proximal side and the convex screw thread (5) on the distal side.

[0028] This firmly fixes the screw thread (5) to the pedicle, and the bone cement is stably retained.

[0029] [5] The groove and the screw thread have the same lead. In the internal fixing device (1) of [4], the groove (4) and the screw thread (5) are formed with equal leads to each other.

[0030] This allows bone cement to smoothly enter the groove (4) when the internal fixation device (1) is screwed in, as in [1], resulting in strong fixation, while the force required for removal can be reduced by applying rotation in the opposite direction to that used for screwing it in. Lead refers to the distance traveled in the axial direction of the central axis per unit number of rotations. By aligning the leads of the groove (4) and the screw thread (5), strong resistance is not applied to one side, and the resistance is distributed. Here, "equal" does not mean equality with mathematical rigor, but rather an error that allows for a reasonable distribution of resistance is acceptable.

[0031] [6] The groove has fewer threads than the screw thread. In the internal fixing device (1) of [5], the number of grooves is smaller than the number of screw threads.

[0032] This allows for a firm fixation to the pedicle by the screw threads (5) while appropriately designing the bonding force between the internal fixation device (1) and the bone cement. As described in [5] above, it is preferable to make the leads of the grooves (4) and the screw threads (5) equal. In this case, a new challenge arises in appropriately setting the contact area with the object, but this challenge can be solved by designing the number of threads independently.

[0033] [7] A therapeutic device for operating the internal fixation device of the present invention (Figures 5, 6, and 7) A typical embodiment disclosed in this application is a therapeutic device (100) comprising a cylindrical screwdriver (40) that can be connected to an internal fixation device (1) inserted from the pedicle into bone cement filled in the vertebral body, and an inner cylinder (30) that can be inserted into the screwdriver, and is configured as follows.

[0034] The internal fixing device comprises a cylindrical shaft (2) and a connecting 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 from the distal end to the proximal end along the central axis. The shaft has a spiral groove (4) on the proximal side.

[0035] 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 fixing device by moving along the central axis, thereby connecting with the internal fixing device and transmitting rotational force around the central axis to the internal fixing device.

[0036] The inner cylinder has a connecting portion (35) that is inserted into the through hole of the screwdriver from the distal end and connected to the screwdriver at the distal end, and a tip portion (32) that protrudes proximally to the tip of the internal fixing device connected to the screwdriver, and has an elastic tongue piece (31) with a convex portion (33) at its tip.

[0037] When the inner cylinder is inserted into the screwdriver and the internal fixing device, the tongue-shaped piece bends toward the central axis, allowing it to move in the central axis direction within the through-hole of the screwdriver and the internal fixing device. Furthermore, when the inner cylinder is inserted into the through-hole of the screwdriver, connected to the screwdriver at its distal end, and also connected to the internal fixing device, the protrusion contacts the tip of the internal fixing device.

[0038] This provides a treatment instrument (100) suitable for inserting the internal fixation device (1) of [1] to [6] into the bone cement filled in the vertebral body from the pedicle. When the driver (40) into which the inner cylinder (30) is inserted is connected to the internal fixation device (1), they are integrated. This integration is achieved by connecting the driver (40) and the internal fixation device (1) at the connection part (3) of the internal fixation device, and by connecting the inner cylinder to the distal end of the driver and pressing down on the tip of the internal fixation device by contacting the convex part of the tongue piece.

[0039] [8] Fixation by inserting guide pins In the treatment device (100) of [7], the inner cylinder 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. When the inner cylinder is inserted into the through hole of the screwdriver (40) and connected to the screwdriver at the distal end, and also connected to the internal fixation device (1), the guide pin is further inserted into the inner cylinder, thereby restricting the multiple tongue pieces from bending in the direction of the central axis, and the protrusions are brought into contact with the tip of the internal fixation device, thereby restricting the movement of the inner cylinder back along the central axis towards the through hole of the internal fixation device.

[0040] This strengthens the integration described in [7].

[0041] [9] The tip of the inner cylinder has tapping threads. In the treatment instrument (100) of [7] or [8], the inner cylinder is provided with a screw thread (34) on the outer surface of the tip that can be tapped.

[0042] This allows the internal fixation device (1) to reach the vertebral body smoothly, even when the diameter of the bone hole formed in the pedicle is small, by operating the integrated treatment device (100) described in [7] to insert the internal fixation device (1) from the pedicle into the vertebral body.

[0043]

[10] The proximal end of the internal fixation device is blunt In the treatment device (100) of [7] or [8], the internal fixation device has a blunt proximal end.

[0044] This reduces the risk of damaging the balloon when inserting the balloon catheter (12) into the through-hole (6) of the internal fixation device (1) and passing the balloon (11) through it.

[0045]

[11] The internal fixation device has a groove on the proximal side and a screw thread on the distal side. In the treatment device (100) of [7] or [8], the shaft of the internal fixation device has the groove on the proximal side and a convex screw thread (5) on the distal side.

[0046] As a result, similar to [4], the screw thread (5) is firmly fixed to the pedicle, and the bone cement is stably held.

[0047]

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

[11] , the groove and the screw thread of the internal fixation device are formed with equal leads.

[0048] This allows bone cement to smoothly enter the groove (4) and be firmly fixed when the internal fixation device (1) is screwed in, as in [5], while the force required for removal can be reduced by applying a rotation in the opposite direction to that used when screwing it in.

[0049]

[13] A groove has fewer threads than a screw thread. In the treatment device (100) of

[12] , the number of grooves in the internal fixation device is smaller than the number of threads in the screw.

[0050] This allows for a firm fixation to the pedicle by the screw threads (5), similar to [6], while also enabling an appropriate design of the bonding force between the internal fixation device (1) and the bone cement.

[0051] 2. Details of the Embodiment The embodiments will be described in more detail.

[0052] [Embodiment 1] Figure 1 shows a top view (a), a front view (b), and a bottom view (c) illustrating an example configuration of the internal fixing device of the present invention. The rear view and left and right side views are the same as the front view (b), except that the groove 4 and screw threads 5 are positioned as extensions from the front view (b), and are therefore omitted from the illustration.

[0053] The internal fixation device 1 comprises a cylindrical shaft 2 and a connecting portion 3 at the distal end of the shaft 2 that can be connected to a screwdriver. The shaft 2 has a spiral groove 4 on its proximal side. Preferably, the shaft 2 is cylindrical, as illustrated in the figure, and has a through hole 6 that extends from the distal end to the proximal end along the central axis. The through hole 6 can, for example, pass a guide pin through it. Also, as will be described later, the through hole 6 may be configured to allow bone drilling instruments, balloon catheters, bone cement injectors, etc., to pass through it. The connecting portion 3 is configured as a hexagonal prism-shaped recess that engages with, for example, a hexagonal wrench, as shown in the figure, so that it can engage with a screwdriver (not shown) and rotate the entire internal fixation device 1.

[0054] Figure 2 is an explanatory diagram showing an overview of an example of the use of the internal fixation device 1. When a patient is standing, the spine is composed of multiple vertebral bodies 20 stacked vertically, and Figure 2 shows one of these vertebral bodies as if viewed from above or below. The vertebral body 20 is supported by a pair of pedicles 21 on the left and right, and these pedicles 21 are connected by a vertebral arch 22. The area enclosed by the vertebral body 20, pedicles 21 and vertebral arch 22 is the spinal canal 23. A compression fracture is a disease in which the vertebral body is compressed and collapsed by an upward or downward force. In treatment using the internal fixation device 1 of the present invention, as will be described later with reference to Figure 4, space is restored inside the vertebral body 20 and bone cement 10 is injected. Before it hardens, the internal fixation device 1 is inserted (twisted in) and supported from the pedicle 21 side. The internal fixation device 1 is inserted from the pedicle 21 into the bone cement 10 that has been pre-filled inside the vertebral body 20. Once the bone cement 10 hardens, it is supported by the internal fixation device 1 from the pedicle 21 and fixed inside the vertebral body 20.

[0055] Figure 3 is an explanatory diagram illustrating the solution principle of the present invention. The upper side (a) shows a cross-sectional view of the joining of the bone cement 10 and the shaft 2 having a groove 4, and the lower side (b) shows a cross-sectional view of the joining when the shaft 2 has screw threads instead of a groove 4. Since it is different from the screw threads 5 on the distal side of the shaft 2, it will not be denoted by the reference numeral 5. Here, the groove 4 is recessed in the direction of the central axis relative to the outer circumferential surface of the shaft 2, and the screw threads are convex outward relative to the outer circumferential surface of the shaft 2. When the shaft 2 has screw threads (b), when it is screwed into the bone cement 10, the screw threads tap the bone cement 10, that is, as the screw threads advance, they push and spread the surrounding bone cement 10 by the amount that they protrude, so the surface of the screw threads is in close contact with the bone cement 10. In addition, when the screw threads tap the bone cement 10, a thrust force is added not only from the thrust force applied to the shaft 2, but also from the rotational force of the tapping. On the other hand, when the shaft 2 has grooves 4 (a), the grooves 4 do not have a tapping effect on the bone cement 10, so the bone cement 10 penetrates the grooves 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 grooves 4, and gaps may remain as illustrated in the figure. Thus, the effect on bone cement is completely different between screw threads and grooves, and as a result, the degree of adhesion is also very different. By forming grooves 4 on the shaft 2, it is possible to make it easier to remove compared to when screw threads are formed, while making it more difficult to remove compared to when only the shaft 2 is present. Therefore, by appropriately adjusting the length, number, and depth of the grooves 4, the appropriate ease of removal can be achieved.

[0056] Note that while groove 4 in the diagram is a pointed triangle, its shape is arbitrary, the angle of the base is arbitrary, and it can be acute or obtuse, even more acute than the right angle shown in the example. Furthermore, the base can be flat or arc-shaped. Also, although the screw thread used for comparison has a sharp tip, the same solution principle applies even if the corners are smoothly chamfered.

[0057] The depth of the groove 4 of the internal fixation device 1 may be uniform, but it is preferable to make the proximal (tip) side deeper than the distal (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 (tip) side that first contacts the bone cement 10 is deeper, so the bone cement 10 enters deeper into the groove 4 and, as it is screwed in, is sent along the spiral of the groove 4 to the shallower distal (head) side of the groove 4, so that the bone cement 10 enters the groove 4 smoothly and is firmly fixed. On the other hand, when removing the device, the internal fixation device 1 rotates in the opposite direction along the spiral of the groove 4 to separate from the bone cement 10, so that the force required for removal can be reduced.

[0058] The shaft 2 of the internal fixation device 1 is more preferably provided with a sloping section 7 whose diameter gradually decreases from the central part towards the proximal end. When screwing the internal fixation device 1 into the bone cement 10, the resistance when initially inserting it into the bone cement 10 is reduced, and the force required when removing it is also reduced.

[0059] The distal end (head end) of the shaft 2 of the internal fixation device 1 is preferably provided with a screw thread 5. The screw thread 5 is a spiral projection that protrudes outward from the outer surface of the shaft 2, and has the function of tapping the surrounding bone as the internal fixation device 1 (shaft 2) rotates, thereby advancing along the central axis. As illustrated in Figure 2, the screw thread 5 taps the pedicle 21 as it advances, firmly fixing the internal fixation device 1 and stably supporting the bone cement 10 inside the vertebral body 20 into which the shaft 2 is inserted.

[0060] It is preferable that the screw threads 5 and grooves 4 are formed with equal leads. Since the lead is the distance traveled along the central axis relative to the amount of rotation of the shaft 2, it is desirable that the distance traveled as the screw threads 5 tap the pedicle 21 and the distance traveled as the shaft 2 moves along the spiral of groove 4 when it is screwed into the bone cement 10 are the same.

[0061] However, a precise match is not always required, and they can be intentionally made to be different. For example, by making the lead of groove 4 larger than the lead of thread 5, groove 4 at the tip of shaft 2 can be partially screwed into the bone cement 10, and after thread 5 begins tapping the pedicle, a force can be applied that brings the bone cement 10 closer to the pedicle as the internal fixation device 1 (shaft 2) rotates.

[0062] The number of grooves in groove 4 and thread 5 can be different. For example, the number of grooves in groove 4 should be smaller than the number of threads in thread 5. This allows for a stronger fixation to the pedicle 21 by thread 5, while also allowing for an appropriate design of the bonding force between the internal fixation device 1 and the bone cement 10. As mentioned above, it is preferable to have equal leads for groove 4 and thread 5. In this case, a new challenge arises: appropriately setting the contact area with the object. This challenge can be solved by designing the number of grooves independently. Reducing the number of grooves in groove 4 reduces the contact area with the bone cement 10, thereby reducing the force required for removal. On the other hand, increasing the contact area between the pedicle 21 and thread 5 strengthens the fixation of the internal fixation device 1 to the pedicle 21. By optimizing the number of grooves rather than the pitch, the relationship between the bone cement 10 and groove 4, and the relationship between the pedicle 21 and thread 5, can be optimized independently.

[0063] Figure 4 is an explanatory diagram illustrating a step-by-step example of the use of the internal fixation device 1 of the present invention. As shown in Figure 2, the spine is composed of multiple vertebral bodies 20 stacked vertically when the patient is standing, with a pair of pedicles 21 supporting the vertebral bodies 20, and these pedicles 21 are connected by a vertebral arch 22. Figure 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 at the top.

[0064] Step A: An incision is made in the skin on the side that provides access to the affected vertebral body 20, and a bone hole 19 is formed in the pedicle 21 leading to the vertebral body 20. The diameter of the bone hole 19 may be just large enough for the shaft 2 of the internal fixation device 1 to be inserted, or a bone hole large enough for the guide pin described later to be inserted, and its length is generally long enough to reach the vertebral body 20.

[0065] Step B: Insert the shaft 2 of the internal fixation device 1 into the formed bone hole 19. It is preferable to insert a guide pin (not shown) into the vertebral body 20 from outside the body through the bone hole 19 and insert the internal fixation device 1 along the guide pin. The part of the shaft 2 without protrusions such as the screw thread 5 should be inserted into the bone hole 19, and the part with the screw thread 5 should stop outside the pedicle 21. Insert the balloon catheter 12 into the through hole 6 of the shaft 2 of the internal fixation device 1, reach its tip into the vertebral body 20, and inflate the balloon 11 at the tip to create space inside the vertebral body 20. At this time, a screwdriver 14 (not shown) may be connected to the connection part of the head 3 of the internal fixation device 1 to pre-twist the screw thread 5 into the pedicle 21. Before inserting the balloon catheter 12, a puncture needle or bone excavator may be introduced into the vertebral body 20 from outside the body through the bone hole 19 to excavate bone from the inside of the vertebral body 20. Furthermore, it is preferable that the tip of the internal fixation device 1 is smoothly chamfered. As described above, in step B, where 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.

[0066] Step C: Instead of the balloon catheter 12, the cement injector 13 is inserted into the through-hole 6 of the shaft 2 of the internal fixation device 1, the tip of the cement injector 13 is brought into the vertebral body 20, and bone cement 10 is injected into the vertebral body 20 from the tip of the cement injector 13. At this time, a driver 14 (not shown in [c]) may be pre-connected to the connection part of the head 3 of the internal fixation device 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 device 1, as described above.

[0067] Step D: Connect the screwdriver 14 to the connection part of the head 3 of the internal fixation device 1 and screw the threaded part 5 into the pedicle 21. At this time, the tip (proximal end) of the internal fixation device 1, the part of the shaft 2 in which the groove 4 is formed, is screwed into the bone cement 10.

[0068] The screwdriver 14 is removed from the internal fixation device 1, the opening is sutured, and the surgery is completed.

[0069] In Figure 4, the driver 14 is not shown in [B] and [C], but as described above, it is preferable to provide a through-hole in the driver 14 that communicates with the through-hole 6 of the internal fixation device 1, 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 puncture needle, bone excavator (not shown), balloon catheter 12, and 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, allowing for bone excavation within the vertebral body 20, space expansion with a balloon, and filling with bone cement 10, all while the driver 14, which is attached from the beginning, remains attached. This reduces the number of steps required to change instruments, shortens the surgical time, and minimizes the time from filling with bone cement 10 to screwing in the internal fixation device 1, allowing the internal fixation device 1 to be screwed in with ample time before the bone cement 10 hardens.

[0070] [Embodiment 2] The internal fixation device 1 of the present invention is more preferably used in combination with the treatment device 100 described in the aforementioned international patent application (PCT / JP2022 / 036147).

[0071] Figure 5 is an explanatory diagram showing this embodiment 2 as one example of the use of the internal fixation device 1. Note that Figure 5 is drawn with the scale in the central axis direction (vertical direction of the paper) compressed and the direction along the patient's body surface (horizontal direction of the paper) emphasized. The treatment device 100 includes a cylindrical screwdriver 40 that can screw the internal fixation device 1 into the pedicle 21, and an inner cylinder 30 that is inserted into the screwdriver 40, and is configured as follows.

[0072] The internal fixation device 1 has a blunt tip that allows for the insertion and removal of soft vertebral body drilling equipment such as balloons, and the through-hole 6 is sized to allow the inner cylinder 30 to pass through from the head 3 to the tip along the central axis.

[0073] The screwdriver 40 is configured to connect to the internal fixing device 1 by fitting into the connection part of the head 3 of the internal fixing device 1 when moved along the central axis, and to transmit rotational force around the central axis to the internal fixing device 1. For example, the tip of the screwdriver 40 may have the shape of a hexagonal wrench (hexagonal prism), and the connection part of the head 3 of the internal fixing device 1 may have a hexagonal groove (recess). The shape of the tip of the screwdriver 40 and the shape of the connection part of the head 3 of the internal fixing device 1 only need to interlock when inserted, and other shapes such as a star shape are also acceptable. By sliding the screwdriver 40 along the central axis to the connection part of the head 3 of the internal fixing device 1, the tip of the screwdriver 40 fits into the connection part of the head 3 of the internal fixing device 1, making it possible to screw in the internal fixing device 1 with the screwdriver 40, and it can be easily removed by pulling out the screwdriver 40.

[0074] The inner cylinder 30 is inserted from the distal end of the screwdriver 40 through the through-hole of the screwdriver 40 and the internal fixing device 1, and has a tip portion 32 that protrudes proximally to the tip of the internal fixing device 1. The inner cylinder 30 is integrally connected to the screwdriver 40 and the internal fixing device 1 with the tip portion 32 protruding proximally to the tip of the internal fixing device 1.

[0075] This makes it possible to provide treatment devices suitable for surgical procedures such as artificial disc replacement, spinal fusion, vertebroplasty, and pedicle formation for spinal diseases.

[0076] An example of a structure for integrating the internal fixing device 1, the driver 40, and the inner cylinder 30 will be described.

[0077] As shown in Figure 5, the screwdriver 40 and the inner cylinder 30 are configured to be connected at their distal ends. The distal end of the screwdriver 40 is provided with a cylindrical connecting portion 45 having male threads 46 on its outer surface, and the distal end of the inner cylinder 30 is provided with a groove-shaped connecting portion 35 that can accommodate the cylinder, and has female threads 36 that mesh with the male threads 46. The relationship between the concave and concave parts, and the relationship between the male and female threads, may be reversed, or other connection mechanisms may be used. Furthermore, as illustrated in Figure 5, it is preferable that the screwdriver 40 is provided with a handle 47 and the inner cylinder 30 is provided with a handle 37, so that they are integrated for easy gripping when connected. Even if the connection is made with screws as in this example, a latch mechanism (not shown) may be provided to prevent the connection from coming undone.

[0078] As shown in Figure 6, the tip (proximal end) of the inner cylinder 30 is divided into a plurality of tongue pieces 31 in the direction along the central axis, and each of the plurality of tongue pieces 31 has a protrusion 33 in the direction away from the central axis. The protrusion 33 has the function of a notch that restricts the internal fixing device 1 from coming out of the inner cylinder 30, as will be described later, so the reference numeral 33 is used to refer to a notch. The plurality of tongue pieces 31 are formed, for example, by dividing the cylindrical inner cylinder 30 with slits from the tip side. The number of divisions can be arbitrary, for example, 4 divisions, 6 divisions, 2 divisions, 3 divisions, etc. In addition, some processing (for example, heat treatment, processing to reduce thickness, processing to bond a highly elastic metal) may be applied to give it appropriate elasticity. The elasticity of the tongue pieces 31 is designed to have appropriate deflection. For example, when the inner cylinder 30 passes through the through hole of the driver 40, the notch 33 is pressed against the inner wall of the through hole, causing it to bend in the direction of the central axis and allowing the inner cylinder 30 to pass through. When the notch 33 emerges proximal to the tip of the internal fixing device 1, the bending returns to its original position, causing the notch 33 to catch on the tip of the internal fixing device 1. If the notch 33 has a smooth shape, even after the notch 33 emerges from the tip of the internal fixing device 1, the force pulling out the inner cylinder 30 can pull the notch 33 back into the through hole 6 of the internal fixing device 1, causing the tongue piece 31 to bend again in the direction of the central axis, thereby allowing the inner cylinder 30 to be pulled out.

[0079] Figure 7 is a schematic diagram illustrating the cross-sectional structure to show an example of the configuration of the tip portion 32 of the inner cylinder 30. As shown in (a) above, when the inner cylinder 30 is inserted into the connected screwdriver 40 and the internal fixing device 1, the tongue piece 31 described above bends toward the central axis, allowing it to move in the through hole in the central axis direction. As shown in (b) below, when the inner cylinder 30 is inserted into the connected screwdriver 40 and the internal fixing device 1 and connected to the screwdriver 40 at the distal end as described above, the tip portion 32 protrudes proximal to the tip of the internal fixing device 1, the bending of the tongue piece 31 returns, and the notch 33 comes into contact with the tip of the internal fixing device 1. In this state, when the guide pin 60 is inserted into the inner cylinder 30, even if you try to pull out the inner cylinder 30, the tongue piece 31 will not bend in the direction of the central axis, the notch 33 will protrude outward beyond the diameter of the through hole 6 of the inner fixing device 1, and the movement of the inner cylinder 30 distally along the central axis, i.e., towards the through hole 6 of the inner fixing device 1, will be restricted, resulting in a stronger integration. Simply put, if the inner fixing device 1 tries to come out of the inner cylinder 30, the notch 33 will come into contact with the tip of the inner fixing device 1 and restrict it from coming out. This makes the integration stronger.

[0080] It is preferable that the tip portion 32 of the inner cylinder 30 is provided with a screw thread 34 that can be tapped onto the outer surface. The screw thread 34 should be formed in a position that smoothly connects with the inclined portion of the inner fixing device 1 when the inner fixing device 1, the driver 40, and the inner cylinder 30 are integrated as described above.

[0081] This paper describes a treatment method for performing artificial intervertebral disc replacement, spinal fusion, vertebroplasty, and pedicle formation for spinal diseases using the treatment device 100 of the present invention.

[0082] Figures 8 and 9 are schematic diagrams illustrating the procedure using the treatment device 100 of this embodiment 2, with Figure 8 showing the first half of the procedure and Figure 9 showing the second half. Figures 8 and 9 illustrate vertebroplasty, but the method of inserting the internal fixation device 1 into the vertebral body is similar in spinal fusion surgery and vertebral reinforcement surgery in artificial disc replacement (not illustrated). Figures 8 and 9 schematically show a cross-section of the affected area of ​​the patient, with the upper side of the paper being distal and the lower side being proximal, from the outside of the skin 24 through the pedicle 21 to the vertebral body 20. The scale in the central axis direction (vertical direction of the paper) has been compressed, and the direction along the patient's body surface (horizontal direction of the paper) has been emphasized. Since there are pedicles 21 on both the left and right sides of the vertebral body 20, the same procedure is performed on one vertebral body 20 from both sides, but Figures 8 and 9 show one of them.

[0083] Step 1 ([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. Step 2 ([2]): The internal fixation device 1 and the screwdriver 40 are connected, and the inner cylinder 30 is inserted into the through-hole on the inside of the screwdriver 40 so that the tip of the inner cylinder 30 protrudes from the tip of the internal fixation device 1. The inner cylinder 30 is then placed over the guide pin 15 and inserted into the patient's body along the guide pin 15. Step 3 ([3]): With the internal fixation device 1, the screwdriver 40, and the inner cylinder 30 connected, push further in the proximal direction along the guide pin 15, and screw the inner cylinder 30 and the tip of the internal fixation device 1 into the pedicle 21. Step 4 ([4]): After screwing in the internal fixation device 1 until its tip reaches near the entrance of the vertebral body 20, the guide pin 15 is removed. At this time, the notch 33 of the inner cylinder 30 is in contact with the tip of the internal fixation device 1, preventing the inner cylinder 30 from coming out naturally. However, with the guide pin 15 removed, the tongue 31 easily bends in the direction of the central axis due to the force pulling out the inner cylinder 30, making it possible to pull out the inner cylinder 30. Step 5 ([5]): Remove the inner cylinder 30. At this time, the screwdriver 40 is simply inserted into the head 3 of the internal fixation device 1, so hold it in place to prevent it from coming out. Although not specifically shown in the diagram, in this step, if necessary, a vertebral body drilling device may be introduced through the screwdriver 40 and the through-hole of the internal fixation device 1 to drill into the vertebral body 20 in order to fill with cement for reinforcement. Step 6 ([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 contrast agent through the balloon catheter 12 and applying pressure. The purpose is to return the vertebral body 20 to its original size when it has suffered a compression fracture due to osteoporosis or the like. Step 7 ([7]): The balloon catheter 12 is withdrawn from the driver 40 and the through-hole of the internal fixation device 1, and the cement injector 13 is inserted in its place to inject bone cement 10 into the vertebral body 20. The amount of cement that can be filled in one go by the cement injector 13 is approximately 1.5 ml. For example, in the case of vertebroplasty for fracture, the cement is injected approximately 3 times from each side, for a total of 6 to 7 times, to fill the vertebral body 20 with approximately 10 ml of bone cement 10. When applied to vertebral reinforcement surgeries other than vertebroplasty, such as spinal fusion and artificial disc replacement, the amount of cement to be filled is adjusted according to the condition of the bone. Step 8 ([8]): Remove the cement injector 13 from the screwdriver 40 and the through-hole of the internal fixing device 1. Step 9 ([9]): Use the screwdriver 40 to screw the internal fixation device 1 into the filled bone cement 10. Step 10 (

[10] ): Remove the driver 40 and suture the incised skin 24 to complete the treatment.

[0084] As described above, with the treatment device 100, the internal fixation device 1 can be screwed into the filled bone cement 10 immediately after filling the bone cement 10, making it suitable for surgical procedures such as spinal fusion, vertebral reinforcement surgery in artificial disc replacement, vertebroplasty, and pedicle formation.

[0085] The filled bone cement 10 is soft enough that the internal fixation device 1 can be screwed in without tapping using the threads 34 at the tip 32 of the inner cylinder 30. Similarly, the internal fixation device 1 can be screwed into the pedicle 21 without tapping using the tip 32 of the inner cylinder 30.

[0086] The treatment instrument 100 is also suitable for removing the internal fixation device 1. After incising the affected area and drilling to the screw head, the guide pin 15 is inserted into the internal fixation device 1, and the screwdriver 40 is introduced along the guide pin to the internal fixation device 1. By simply pushing the tip in, the screwdriver 40 can be connected. Then, by rotating the screwdriver 40, the internal fixation device 1 can be pulled out.

[0087] Although the present inventors have described the invention in detail based on embodiments above, it goes without saying that the present invention is not limited thereto and can be modified in various ways without departing from its essence. [Industrial applicability]

[0088] The present invention relates to a cylindrical internal fixation device for medical use, and is particularly suitable for use in internal fixation surgery of the vertebral body, which is the affected area. [Explanation of Symbols]

[0089] 1 Internal fixation device 2 shafts 3. Head (driver connection part) 4 grooves 5 Screw threads 6 Through hole 7 Slope 10 Bone cement 11 Balloons 12 Balloon catheter 13. Cement Injector 14 Driver 15 Guide pins 19 Bone hole 20 vertebral bodies 21 pedicle 22 vertebral arch 23 Spinal canal 24 Skin 30 Inner cylinder 31. Inner tube tongue 32 Tip of the inner cylinder 33 Notches 34 Threads at the tip of the inner cylinder 35. Connection point to the driver 36 Female thread 37. Handle of the inner cylinder 40 Driver 45 Connection part with inner cylinder 46 Male screw 47 Driver's handle 100 Treatment Equipment

Claims

1. An internal fixation device that is inserted through the pedicle and supports bone cement filled into the vertebral body, It has a cylindrical shaft that can be connected to the distal end of a screwdriver and rotated, The shaft has a sloping section in which the diameter gradually decreases towards the proximal end. The shaft has a spiral groove in the inclined portion for the bone cement filling the surrounding area to enter, The shaft has a convex screw thread on its distal side for engaging with the pedicle. Internal fixation device.

2. In claim 1, The groove has a certain lead structure that moves in the withdrawal direction along the convex screw threads formed by bone cement that has entered the groove and hardened when the internal fixation device is rotated in the direction of withdrawing the screw threads from the pedicle. Internal fixation device.

3. In claim 1, The groove and the screw thread are formed separately on the proximal and distal sides, respectively. Internal fixation device.

4. In claim 1, The groove is deeper on the proximal side than on the distal side of the shaft. Internal fixation device.

5. In claim 1, The groove and the screw thread are formed with equal leads to each other. Internal fixation device.

6. In claim 5, The number of grooves is smaller than the number of threads. Internal fixation device.

7. A therapeutic device comprising an internal fixation device as described in any one of claims 1 to 6, a cylindrical screwdriver connectable to the internal fixation device, and an inner cylinder that can be inserted into the screwdriver, The driver has a through hole through which the inner cylinder can pass from the head to the tip along the central axis, and is configured to be able to be fitted into the connection part of the internal fixing device and connected to the internal fixing device by moving along the central axis, and to be able to transmit rotational force around the central axis to the internal fixing device. The inner cylinder has a connecting portion that is inserted into the through hole from the distal end of the screwdriver and connected to the screwdriver at the distal end, and a tip portion that protrudes proximally to the tip of the internal fixing device connected to the screwdriver. treatment equipment.

8. In claim 7, The inner cylinder has an elastic tongue-shaped piece with a protrusion at its tip, When the inner cylinder is inserted into the screwdriver and the internal fixing device, the tongue piece bends toward the central axis, allowing it to move in the central axis direction within the through hole of the screwdriver and the internal fixing device. When the inner cylinder is inserted into the through-hole of the screwdriver, connected to the screwdriver at its distal end, and also connected to the internal fixing device, the protrusion contacts the tip of the internal fixing device. treatment equipment.

9. In claim 8, The inner cylinder has a through hole through which a guide pin can be passed from the distal end to the proximal end along the central axis. When the inner cylinder is inserted into the through-hole of the screwdriver, connected to the screwdriver at its distal end, and also connected to the internal fixing device, the guide pin is inserted into the inner cylinder, thereby restricting the tongue from bending in the direction of the central axis, and the protrusion contacts the tip of the internal fixing device, thereby restricting the movement of the inner cylinder back along the central axis towards the through-hole of the internal fixing device. treatment equipment.

10. In claim 9, The inner cylinder is provided with a screw thread on the outer surface of the tip portion that can be tapped. treatment equipment.

11. In claim 9, The aforementioned internal fixation device has a blunt proximal end. treatment equipment.

12. In claim 7, The inner cylinder is provided with a screw thread on the outer surface of the tip portion that can be tapped. treatment equipment.

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