Treatment instrument

Abstract

The present invention is a treatment instrument that includes an inner fixation instrument, an outer cylinder, and a cement separation instrument that are inserted into the vertebral body from a pedicle, the treatment instrument being configured as follows. The inner fixation instrument has a head, a shaft, and a first through-hole. The outer cylinder has a connection part that is connected to the head of the inner fixation instrument at the proximal end, a shaft, and a second through-hole that communicates with the first through-hole when connected to the inner fixation instrument. The cement separation instrument comprises a motion direction conversion mechanism that has a shaft inserted into a through-hole communicating therewith, has a separation instrument-side screw thread on the outer periphery of the shaft, and is engaged with a screw thread provided in the first or second through-hole, whereby the rotational force for rotation around a center axis is converted into a rectilinear force that causes the distal end of the cement separation instrument to travel straight along the central axis, with the inner fixation instrument or the outer cylinder connected to the inner fixation instrument acting as a fulcrum. As a result, it is possible to provide a treatment instrument with which the inner fixation instrument embedded in the body during a vertebral body formation operation can be easily removed even if it becomes necessary to remove the inner fixation instrument in the future.

Description

treatment equipment

[0001] The present invention relates to a treatment device used in percutaneous vertebroplasty, and is particularly suitable for use in surgery in which cement is filled inside the affected bone in advance and an internal fixation device (screw) that is screwed into the cement from the outside of the bone is removed.

[0002] Vertebroplasty and spinal fusion are known treatments for spinal compression fractures. The spine consists of stacked vertebral bodies, the vertebral arches that support and connect them vertically, the pedicles, and the upper and lower articular processes. The vertebral bodies are cylindrical bones that sandwich the nucleus pulposus and the surrounding annulus fibrosus from above and below, and are supported by two pedicles extending from the vertebral arches. The vertebral arches are connected vertically by the upper and lower articular processes, and support the vertebral bodies via the pedicles, forming the spine. Compression fractures are diseases in which the vertebral bodies are crushed and damaged by vertical compression.

[0003] Percutaneous vertebroplasty is a surgical procedure for reconstructing a collapsed vertebral body, typically by filling the vertebral body with artificial bone or medical cement (referred to herein as "bone cement" or simply "cement"). Vertebroplasty is performed through a small percutaneous incision, minimizing invasiveness and reducing the burden on the patient, thereby contributing to a reduction in hospital stays and ultimately medical and nursing care costs. While percutaneous vertebroplasty has shown favorable outcomes in many cases, there have been reported complications, such as instability of the filled cement resulting in dislocation, resulting in insufficient improvement of the vertebral body and intervertebral instability, and the need for additional surgery. To prevent these complications, a method has been proposed in which screws are inserted through the pedicle into the cement mass after filling and before hardening to internally fixate (reconstruct) the fractured vertebrae (a procedure combining vertebroplasty and pedicle plasty) (Yoshiaki Yonezawa et al., "Percutaneous vertebroplasty for osteoporotic vertebral pseudarthrosis: Combined use of PMMA and intravertebral screws," Fracture Research Paper, Vol. 28, pp. 444-448, 2006, Japanese Society for the Treatment of Fractures). This technique has been successfully applied to many patients. This technique may also be effective not only for vertebroplasty for compression fractures, but also for spinal fusion for osteoporotic spinal degenerative diseases and spinal reinforcement in lumbar artificial disc replacement.

[0004] Spinal fusion is a surgical procedure for fixing the affected intervertebral space in cases of degenerative spinal disease, and for compression fractures, it is a surgical procedure for fixing the healthy vertebrae above and below using spinal fusion implants. In spinal fusion, screws are inserted into the pedicles of multiple vertebrae, and the heads of the screws are connected to rods that run vertically between each other to fix the affected intervertebral space or fractured vertebra. Depending on the condition of the affected vertebra, spinal fusion, artificial disc replacement, or vertebroplasty are selected or combined for each disease.

[0005] Various medical devices have been proposed for use in these treatments.

[0006] Patent Document 1 discloses a screwdriver for driving a screw from a pedicle to a vertebral body. The screwdriver is composed of a shank for rotating the pedicle screw, a clamping sleeve that supports the shank so that it can rotate around the shank, and an adapter sleeve that is attached to the clamping sleeve and transmits rotation from the handle. The adapter sleeve is detachable, and when removed, the shank and clamping sleeve remain connected to the pedicle screw, thereby improving the surgeon's view of the surgical area (paragraphs 0014 and 0015).

[0007] Patent Document 2 discloses a medical screw that can be easily removed from a fracture site after being screwed in. This medical screw is hollow from the head along the central axis, has a threaded portion on the outside, and has a reverse internal threaded portion that runs in the opposite direction to the threaded portion near the inner hollow tip. When screwing in this medical screw, a hex wrench (Figure 3) that engages with the hexagonal groove on the head is used, and when removing it, a removal tool (Figure 6) is used, which has a reverse external threaded portion at the tip that engages with the reverse internal thread.

[0008] Patent Documents 3 and 4 disclose a treatment instrument including a cylindrical driver capable of driving a screw into bone and an inner tube that can be inserted into the driver. The screw, driver, and inner tube are integrated and inserted into the vertebral body through the pedicle. A balloon catheter and a cement filling tube are sequentially inserted in place of the inner tube to fill the bone cement, and the screw can be screwed into the filled bone cement mass by operating the driver. The head of the screw has a hexagonal hole that can be fitted with, for example, a hexagonal wrench at the tip of the driver. If it becomes necessary to remove the screw from the bone cement mass in the future, the tip of the driver can be connected to the head of the screw and the screw can be rotated to remove it.

[0009] JP 2016-19728 A JP 2016-209295 A Japanese Patent No. 7300133 A Japanese Patent No. 7329895 A

[0010] The screwdriver disclosed in Patent Document 1 also functions as a cement injection cannula, allowing cement to be injected into the pedicle screw via the shank without changing the instrument (paragraphs 0058-0068). However, as stated in paragraph 0068, "cement can be injected into the pedicle screw 30 with the cannula inserted via the shank 2 immediately after the pedicle screw is screwed in, without changing the instrument," it is not intended to screw the screw into the cement mass after cement injection. Therefore, it is obvious that the removal of a screw threaded into a cement mass is not at all considered. In other words, if the cement mass that has adhered to and integrated with the tip of the screw becomes loose with the surrounding bone, even if an attempt is made to rotate the screw alone to remove it from its insertion trajectory, the cement mass cannot be separated from the screw. Instead, the screw and bone cement mass will rotate together while the bone cement remains integrated, forcing the screw to be forcibly removed backward, destroying the intact vertebrae (pedicle and vertebral arch). This was an extremely dangerous procedure that could have resulted in damage to the surrounding vital organs, the spinal nerves and nerve roots.

[0011] The treatment instruments shown in Patent Documents 3 and 4 integrate a screw, driver, and inner cylinder, and insert the screw into the vertebral body through the pedicle, then remove the inner cylinder and use a balloon catheter to form a cavity in the vertebral body, fill the cavity with bone cement using a cement filling tube, and then operate the driver to screw the screw into the filled bone cement.If it becomes necessary to remove the screw in the future, the driver can be fitted into the screw head again and the screw can be rotated and removed.

[0012] The present inventor, an orthopedic surgeon, noticed a problem with the treatment instruments disclosed in Patent Documents 3 and 4: their structural stability was insufficient when removing screws. He noticed that because the screw head is simply fitted with the tip of a driver, the connection may become disconnected, resulting in the unnecessary step of blindly reinserting the screw inside the muscle. He also considered the risk of stripping the hexagonal socket of the screw head. Furthermore, the inventor noticed several issues that make screw removal difficult when it becomes necessary. He noticed that when using the treatment instruments disclosed in Patent Documents 3 and 4 to remove a screw from bone cement within a vertebral body, it was not possible to apply sufficient force to separate the screw from the bone cement. The need for screw removal can occur early after surgery, such as when interference with spinal nerves is discovered, or it can occur several weeks to several months after surgery when deep infection develops at the fracture site. The basic premise is that when removing a screw integrated with bone cement, the screw must be removed from the posterior and the bone cement from the anterior and lateral sides of the vertebral body, respectively, to avoid damaging important organs (spinal nerves, nerve roots, large blood vessels anterior to the vertebral body, and remaining bone, such as normal pedicles and vertebral arches). When screw and bone cement removal is required, it is necessary to consider the possibility that neither the screw nor the bone cement has adhered to the surrounding bone and has loosened internally. In this situation, the bone cement and the screw are strongly adhered once integrated. Therefore, if an attempt is made to remove the screw by rotating it from the posterior alone, there is a risk that the internal bone cement will rotate with the screw within the vertebral body, making it impossible to separate the screw and bone cement for removal. Forcing removal without separating the screw and bone cement risks damaging the important organs surrounding the spine, as mentioned above.

[0013] The medical device disclosed in Patent Document 2 is a screw removal tool. It is a medical screw removal tool for joining fractured bones (paragraph

[0001] ). The invention addresses the problem of removing a metallic medical screw (claim 1) for joining fractured bones, but does not anticipate the removal of a screw threaded into bone cement. Even when applied to removing a screw threaded into bone cement, the screw at the tip of the removal tool is threaded into a thread located deep within the screw's hollow, and the screw is rotated to remove it. Therefore, the risk of stripping is unlikely. However, if the bone cement is not firmly attached to the surrounding bone and is loosened internally, the bone cement may rotate (spin freely) as the screw rotates, potentially preventing the screw from being removed.

[0014] The object of the present invention is to provide a treatment instrument that, when removing an internal fixation device such as a screw that has been screwed from a pedicle into bone cement filled in a vertebral body during vertebroplasty, can safely separate and remove the internal fixation device from the bone cement even when the bone cement has not bonded to the surrounding bone and has become loose inside. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

[0015] According to one embodiment of the present invention, the following is true.

[0016] That is, the treatment instrument of the present invention includes an internal fixation instrument that is inserted into the vertebral body from the pedicle, an outer cylinder, and a cement separation instrument, and is configured as follows.

[0017] The internal fixation device has a head, a first shaft extending from the head to a proximal end, and a through-hole passing through the central axis of the first shaft.

[0018] The outer tube has a connection portion connected to the head of the internal fixation device at its proximal end, a second shaft extending from the distal end to the proximal end, and a second through hole that communicates with the first through hole when connected to the internal fixation device.

[0019] The cement separation instrument has a third shaft inserted into the first through hole and the second through hole.

[0020] The treatment instrument is equipped with a motion direction conversion mechanism that converts the rotational force of the cement separation instrument, which is inserted into the first through hole and rotates around the central axis of the first through hole, into a linear force that moves the cement separation instrument straight along the central axis, using the internal fixation instrument or the outer tube connected to the internal fixation instrument as a fulcrum.

[0021] Here, the term "internal fixation device" refers to a device that is inserted from the pedicle side into bone cement filled inside a vertebral body to fix the bone cement. It refers to a device that includes the above-mentioned screw, and includes devices in which self-tapping threads or the like are not formed on the proximal side of the shaft. "Proximal" is a medical term referring to the side closer to the centerline of the patient's body, and "distal" refers to the farther side. The term "cement" refers to a medical bone cement, whose main components are, for example, calcium phosphate and polymethylmethacrylate, and which hardens over time.

[0022] The effects obtained by the embodiment are briefly described below.

[0023] In other words, in vertebroplasty, when removing an internal fixation device such as a screw that has been screwed from the pedicle into the bone cement filled in the vertebral body, even if the bone cement has not adhered to the surrounding bone and has become loose inside, a treatment instrument can be provided that can safely separate and remove the internal fixation device from the bone cement.

[0024] FIG. 1 is an explanatory diagram schematically showing the cross-sectional structure of a treatment instrument of Embodiment 1. FIG. 2 is an explanatory diagram showing an example of the operation of the treatment instrument of the present invention. FIG. 3 is an explanatory diagram schematically showing the cross-sectional structure of a treatment instrument of Embodiment 2. FIG. 4 is an explanatory diagram showing an example of the configuration of a cap. FIG. 5 is an explanatory diagram showing another example of the configuration of the cap. FIG. 6 is an explanatory diagram schematically showing the cross-sectional structure of a treatment instrument of Embodiment 3. FIG. 7 is an explanatory diagram showing an example of the configuration of a cement molding instrument and a tip portion of a cement separating instrument. FIG. 8 is an enlarged view showing an example of the configuration of the tip portion of the cement separating instrument. FIG. 9 is an enlarged view showing another example of the configuration of the tip portion of the cement separating instrument. FIG. 10 is a cross-sectional view schematically showing one example of the configuration of an internal fixation instrument. FIG. 11 is a front view of the internal fixation instrument of FIG. 10. FIG. 12 is a cross-sectional view schematically showing another example of the configuration of the internal fixation instrument. FIG. 13 is a front view of the internal fixation instrument of FIG. 12. FIG. 14 is a cross-sectional view schematically showing an example of the configuration of an inclined portion of a shaft of an internal fixation instrument. FIG. 15 is a cross-sectional view schematically showing one configuration example of a connection portion between the internal fixation device and the outer tube. FIG. 16 is a cross-sectional view schematically showing another configuration example of a connection portion between the internal fixation device and the outer tube. FIG. 17 is an explanatory diagram showing an example of the procedure of a surgical procedure for removing the internal fixation device using the treatment device of embodiment 1. FIG. 18 is an explanatory diagram showing another example of the procedure of a surgical procedure for removing the internal fixation device using the treatment device of embodiment 1. FIG. 19 is an explanatory diagram showing an example of the procedure of a surgical procedure for removing the internal fixation device using the treatment device of embodiment 2. FIG. 20 is a cross-sectional view showing an example of the configuration of a connection portion of an improved driver with the internal fixation device and the cap. FIG. 21 is an explanatory diagram schematically showing the cross-sectional structure of the treatment device of embodiment 4. FIG. 22 is an explanatory diagram showing an example of the procedure of a surgical procedure for removing the internal fixation device using the treatment device of embodiment 4.

[0025] 1. Overview of the Embodiments First, an overview of the representative embodiments disclosed in the present application will be described. Reference numerals in parentheses in the drawings used in the overview of the representative embodiments merely illustrate components included in the concept of the components to which they are attached.

[0026] Throughout this specification, ordinal numbers such as first shaft, second shaft, and third shaft are used to indicate which instrument the shaft belongs to, and when it is clear which instrument the shaft refers to, for example, when it can be clearly distinguished by its symbol, the ordinal numbers are omitted. The same applies to through-holes, connecting parts, fitting parts, screw threads, etc.

[0027] [1] Treatment instrument having a motion direction conversion mechanism for pushing out a cement separation instrument (Figs. 1, 3, 21) The present invention is a treatment instrument (10) including an internal fixation instrument (1) inserted into a vertebral body from the pedicle, an outer tube (2), and a cement separation instrument (8), and is configured as follows.

[0028] The internal fixation device has a head (11), a first shaft (14) extending from the head to a proximal end, and a through hole (19) passing through the central axis of the first shaft.

[0029] The outer tube has a connection portion (21) connected to the head of the internal fixation device at its proximal end, a second shaft (24) extending from the distal end to the proximal end, and a second through hole (29) communicating with the first through hole when connected to the internal fixation device.

[0030] The cement separation instrument has a third shaft (84) that is inserted into the first through hole and the second through hole.

[0031] The treatment instrument is equipped with a motion direction conversion mechanism (22 or 18, 82) that converts the rotational force of the cement separation instrument, which is inserted into the first through hole and rotates around the central axis of the first through hole, into a linear force that moves the cement separation instrument straight along the central axis, with the internal fixation instrument or the outer tube connected to the internal fixation instrument as a fulcrum.

[0032] This makes it possible to provide a treatment instrument that, when removing an internal fixation device such as a screw that has been screwed from the pedicle into the bone cement filled in the vertebral body during vertebroplasty, can safely separate and remove the internal fixation device from the bone cement even if the bone cement has not adhered to the surrounding bone and has become loose inside.

[0033] [2] A motion direction conversion mechanism is implemented on the outer tube (Figures 1 and 2). In the treatment instrument of [1], the third shaft of the cement separation instrument can be inserted into the communicating first and second through holes and has a separation instrument side thread (82) on its outer periphery, and the motion direction conversion mechanism is formed by the outer tube side thread (22) formed in the second through hole of the outer tube engaging with the separation instrument side thread of the third shaft of the cement separation instrument.

[0034] This allows the rotational force of the internal fixation device rotating around the central axis of the through-hole to be converted into a linear force that moves the cement separation device linearly along the central axis, with the outer cylinder as a fulcrum. Furthermore, even if the through-hole of the internal fixation device is clogged with bone cement, bone fragments, scars, or other foreign matter (not shown), the cement separation device can be inserted by drilling or otherwise removing the foreign matter from the through-hole of the internal fixation device in advance, allowing the internal fixation device to be safely separated from the bone cement and removed.

[0035] [3] A tip portion of the cement separation instrument that protrudes from the tip of the internal fixation instrument (Figs. 1 and 2) In the treatment instrument of [2], the third shaft of the cement separation instrument has a tip portion (81) that protrudes from the tip of the internal fixation instrument when inserted into the communicating first and second through holes.

[0036] This makes it possible to apply a linear force to the bone cement and separate it from the internal fixation device, even if the bone cement is located beyond the tip of the internal fixation device.

[0037] [4] Implementation of a motion direction change mechanism in the internal fixation device (Figs. 3 and 21) In the treatment device of [1], the third shaft of the cement separation device has a separation device side thread (82) on its outer periphery, and the motion direction change mechanism is formed by the engagement of the internal fixation device side thread (18) provided in the first through hole of the internal fixation device with the separation device side thread.

[0038] The outer tube (2) may be any instrument that satisfies the requirements defined in [1]. For example, the driver (3) shown in Fig. 21 has a fitting portion (33, corresponding to the connecting portion 21) that is connected to the head of the internal fixation device (1) at its proximal end, a third shaft (34, corresponding to the second shaft 24) that extends from the distal end to the proximal end, and a third through-hole (39, corresponding to the second through-hole 29) that communicates with the first through-hole (19) when connected to the internal fixation device (1), and corresponds to the outer tube (2) defined in [1].

[0039] This allows the fulcrum of the linear force that moves the cement separation instrument in a straight line to be located inside the internal fixation instrument, allowing the internal fixation instrument to be separated from the bone cement and removed more safely.

[0040] [5] A tip portion of the cement separating instrument that protrudes from the tip of the internal fixation instrument (Fig. 3) In the treatment instrument of any one of [2] to [4], the third shaft of the cement separating instrument further has a tip portion (81) that protrudes from the tip of the internal fixation instrument when inserted into the first and second through holes that communicate with each other.

[0041] This makes it possible to apply a linear force to the bone cement and separate it from the internal fixation device, even if the bone cement is located beyond the tip of the internal fixation device.

[0042] [6] Cap (Figs. 4 and 5) In the treatment device according to any one of [1] to [5], the treatment device further includes a cap (9). The cap is inserted into the opening in the head of the internal fixation device.

[0043] This prevents the head of the internal fixation device from becoming blocked by bone cement, bone fragments, scar tissue, or other foreign matter.

[0044] [7] The shaft of the cap closes the through hole of the internal fixation device (Figs. 4 and 5). In the treatment device of [6], the cap has a fourth shaft (94) that is inserted into the first through hole of the internal fixation device.

[0045] This allows the shaft of the cap to close the through-hole of the internal fixation device, preventing the through-hole of the internal fixation device from being blocked by bone cement, bone fragments, scars, or other foreign matter.

[0046] [8] Tapping structure at the tip of the shaft of the cap (Fig. 5) In the treatment instrument of [7], the fourth shaft has a tapping structure at the tip.

[0047] This allows the cap to be passed through the internal fixation device and secured to the bone cement.

[0048] [9] The rotation direction in which the separation instrument generates a propulsive force toward the bone cement is opposite to the rotation direction of the connection between the internal fixation instrument and the outer tube (Figs. 15 and 16). In the treatment instrument of any one of [1] to [8], the internal fixation instrument has a tapping screw thread (15) on the outer periphery of the first shaft, which can be screwed into the pedicle in the same direction as the rotation that causes the cement separation instrument to move straight along the central axis by the motion direction conversion mechanism, and the connection part of the outer tube is connected to the head (11) of the internal fixation instrument by a screw in the opposite direction to the tapping screw thread.

[0049] As a result, when rotating the cement separation instrument to separate the bone cement from the internal fixation instrument, the surgeon can apply force in the opposite direction to hold the outer tube connected to the internal fixation instrument so that it does not rotate in the same direction as the cement separation instrument, preventing the internal fixation instrument from rotating together with the cement separation instrument in the spine. In other words, the connection between the internal fixation instrument and the outer tube does not loosen when the internal fixation instrument is rotated in the direction of removal, and this rotation is converted into a linear force that moves the separation instrument in a straight line, helping to separate it from the bone cement and stabilizing the internal fixation instrument, allowing it to be separated and removed more safely.

[0050]

[10] + Driver + Cement Filling Instrument + Cement Molding Instrument (Fig. 6) The treatment instrument of [3] or [5] further includes a driver (3), a cement filling instrument (5, 6), and a cement molding instrument (7).

[0051] The internal fixation device has a first fitting portion (13) on the head, and the second through-hole of the outer cylinder allows the driver to pass through. The driver has a second fitting portion (33) that fits with the first fitting portion of the internal fixation device when the internal fixation device and the outer cylinder are connected and the driver is inserted into the second through-hole, and has a third through-hole (39) that communicates with the first through-hole when fitted.

[0052] The cement filling instrument can be inserted into the first and third through-holes that communicate when the internal fixation instrument and the outer cylinder are connected, the driver is inserted into the second through-hole, and the first and second fitting portions are fitted together to connect the internal fixation instrument to the internal fixation instrument, and bone cement can be injected into the vertebral bone from the proximal end of the internal fixation instrument. The cement filling instrument is configured to include a filling tube (5) and a pushing rod (6), for example, as shown in Figure 6. Alternatively, although not shown, a syringe filled with bone cement may be connected to the head of the filling tube instead of the pushing rod, and the bone cement may be filled into the vertebral bone.

[0053] The cement molding instrument has a molding portion (72) that protrudes from the proximal end of the internal fixation instrument and is inserted into the first and third through holes that communicate when the internal fixation instrument and the outer cylinder are connected, the driver is inserted into the second through hole, and the first and second fitting portions are fitted together to connect with the internal fixation instrument.

[0054] The tip of the cement separating instrument is inserted into a hole formed by the molding part of the cement molding instrument in the bone cement mass injected into the vertebral body by the cement filling instrument.

[0055] This makes it possible to prevent bone cement from flowing back into the through-hole of the internal fixation device or from remaining behind by making the tip of the cement filling device (filling tube) protrude further than the tip of the internal fixation device. Furthermore, the tip of the cement separating device can be stably fitted into a predetermined hole formed in the bone cement, which helps separate the internal fixation device from the bone cement and allows the internal fixation device to be removed more safely.

[0056]

[11] Tapping thread at the tip of the cement separating instrument (Figs. 7 to 9) In the treatment instrument of

[10] , the forming part of the cement forming instrument is cylindrical, or a cylindrical tapered type whose diameter decreases toward the tip, or a conical or hemispherical type, and the tip of the cement separating instrument has a tapping thread (85) that fits into the hole formed and molded by the forming part of the cement forming instrument.

[0057] This allows the tip of the cement separation instrument to protrude beyond the tip of the internal fixation instrument, in the event of loosening between the internal fixation instrument and the surrounding bone cement, not only to transmit a thrust (propulsive force) to separate the bone cement from the internal fixation instrument, but also to transmit a rotational force to the bone cement in the direction of separation of the bone cement from the internal fixation instrument. At this time, the surgeon holds the bone cement separation instrument and rotates the outer cylinder in the direction of removal of the internal fixation instrument to prevent the bone cement from rotating within the vertebral body. If the hole formed by the molding part of the cement separation instrument is circular in plan view and the tip of the cement separation instrument does not have the self-tapping thread defined in

[11] above, simply fitting the tip of the cement separation instrument into the formed hole will not be enough to prevent the free rotation of the bone cement mass. Providing the self-tapping thread at the tip of the cement separation instrument can prevent the bone cement mass from rotating within the vertebral body, facilitating separation of the internal fixation instrument from the bone cement mass and allowing for safer removal of the internal fixation instrument.

[0058]

[12] Spiral grooves / ridges on the outer periphery of the internal fixation device (Fig. 7) In the treatment device of

[11] , the internal fixation device has spiral grooves (17) or spiral ridges on the outer periphery of the first shaft.

[0059] This allows the strength of fixation of the internal fixation device to be adjusted by taking into account the balance between the risk of bone cement mass dislodging and the strength of removal. Furthermore, the tapping thread at the tip of the cement separation device may be formed with the same lead as the spiral groove or thread. This allows the force generated by the rotational force of the bone cement separation device to be transmitted more effectively in the direction of separating the bone cement and the internal fixation device, making it easier to remove the internal fixation device.

[0060]

[13] A spherical portion at the tip of the cement separating instrument (Fig. 9) In the treatment instrument of any one of

[10] to

[12] , the tip of the cement separating instrument has a spherical portion at the tip.

[0061] This reduces the risk of breaking the bone cement when it is pressed to separate it from the internal fixation device.

[0062]

[14] Detailed specifications of the internal fixation device (inclined portion) (Figs. 10 to 14) In the treatment device according to any one of [1] to

[13] , the internal fixation device has a blunt tip and an inclined portion (16) that tapers toward the proximal side of the shaft.

[0063] This weakens the strength of the fixation of the internal fixation device to the bone cement mass, helps separate the internal fixation device from the bone cement mass, and makes it easier to remove the internal fixation device.In addition, in the procedure of introducing a balloon catheter into the vertebral body and inflating the balloon to form a cavity (space) before filling the vertebral body with bone cement, it is possible to reduce the risk of damaging the balloon with the tip of the internal fixation device and also to weaken the resistance to removal from the bone cement.

[0064]

[15] Detailed specifications of the internal fixation device (multi-stage inclined portion) (Fig. 14) In the treatment device of

[14] , the inclined portion includes first and second inclined portions having successively different inclination angles toward the proximal side of the shaft.

[0065] This allows the strength of the internal fixation device to be adjusted by changing the thickness thereof, making it even easier to remove the internal fixation device.

[0066]

[16] Detailed specifications of the internal fixation device (screw groove / thread on outer periphery) (Fig. 11) In the treatment device of

[14] or

[15] , the inclined portion has a spiral groove (17) or thread on the outer periphery.

[0067] This allows the strength of fixation of the internal fixation device to be adjusted by taking into consideration the balance between the risk of dislodging the bone cement mass and the strength of removal.

[0068]

[17] Detailed specifications of the internal fixation device (island-shaped grooves / ridges on the outer periphery) (illustration omitted) In the treatment device of

[14] or

[15] , the inclined portion has a recess or a protrusion on the outer periphery.

[0069] This allows the strength of fixation of the internal fixation device to be adjusted by taking into consideration the balance between the risk of dislodging the bone cement mass and the strength of removal.

[0070] 2. Details of the embodiment The embodiment will be described in further detail.

[0071] [First Embodiment] Fig. 1 is an explanatory diagram showing a schematic cross-sectional structure to illustrate a configuration example of a treatment device according to a first embodiment.

[0072] The treatment instrument 10 of the present invention comprises an internal fixation instrument 1 that is inserted into the vertebral body through the pedicle, an outer cylinder 2, and a cement separation instrument 8.

[0073] The internal fixation device 1 has a head 11, a shaft 14 extending from the head 11 to the proximal end, and a through-hole 19 passing through the central axis of the shaft 14. For example, it is a medical screw. Details will be described later. The outer cylinder 2 has a connecting portion 21 that connects at its proximal end to the connecting portion 12 provided on the head 11 of the internal fixation device 1, a shaft 24 that extends from the distal end to the proximal end, and a through-hole 29 that communicates with the through-hole 19 of the internal fixation device 1 when connected to the internal fixation device 1. The cement separation device 8 has a shaft 84 that is inserted into the through-hole 19 of the internal fixation device 1.

[0074] This treatment instrument 10 is equipped with a motion direction conversion mechanism that converts the rotational force of the cement separating instrument 8, which is inserted into the through-hole 19 of the internal fixation instrument 1 and rotates around its central axis, into a linear force that moves the cement separating instrument 8 straight along the central axis, with the internal fixation instrument 1 or the external cylinder 2 connected to it as a fulcrum.

[0075] This makes it possible to provide a treatment instrument 10 that, when removing an internal fixation instrument 1 such as a screw that has been screwed from the pedicle into bone cement filled in the vertebral body during vertebroplasty, can safely separate and remove the internal fixation instrument 1 from the bone cement without damaging the surrounding tissues within the bone, even if the bone cement has not adhered to the surrounding bone and is loosened within the bone.

[0076] The motion direction conversion mechanism is typically a screw structure. By rotating the cement separation instrument 8, the cement separation instrument 8 moves linearly in the direction of the rotation axis. The cement separation instrument 8 applies a linear force in the same direction as the insertion direction to separate the internal fixation instrument 1 inserted into the bone cement from the bone cement. Ideally, the fulcrum of this force is located on the internal fixation instrument 1, but it may also be on the outer cylinder 2 connected to the internal fixation instrument 1, or on another instrument connected on the same central axis. Figure 1 shows an example in which a screw structure functioning as a motion direction conversion mechanism is provided inside the through-hole 29 of the outer cylinder 2.

[0077] An outer tube side thread 22 (which may be simply referred to as a "thread 22" when it is clear that the thread is provided on the outer tube 2) is provided within the through-hole 29 of the outer tube 2, and a separation-tool side thread 82 (which may be simply referred to as a "thread 82" when it is clear that the thread is provided on the cement separation tool 8) is provided on the outer periphery of a shaft 84 of the cement separation tool 8. The cement separation tool 8 is inserted into the communicating through-holes 19 and 29, and the thread structure in which the separation-tool side thread 82 provided on the outer periphery of the shaft 84 meshes with the outer tube side thread 22 provided within the through-hole 29 of the outer tube 2 functions as a motion direction conversion mechanism. That is, when the cement separation tool 8 is rotated, the thread structure converts the rotational force into a linear force along the central axis of rotation, which acts as a force that moves the shaft 84 of the cement separation tool 8 linearly toward the distal end within the through-hole 19 of the internal fixation tool 1.

[0078] A handle 88 may be provided at the distal end of the cement separation instrument 8. The handle 88 may be welded or glued to the shaft 84, or may be configured to be detachable. A handle 88 may also be provided on the outer cylinder 2. When the cement separation instrument 8 is rotated, the outer cylinder 2 can be prevented from rotating along with the rotation.

[0079] FIG. 2 is an explanatory diagram showing an example of the operation of the treatment instrument 10. The diagram shows the internal fixation instrument 1 being screwed into a bone hole formed from the pedicle 91 toward the vertebral body 92 using the tapping screw thread 15 formed on the distal side of the shaft 14 of the internal fixation instrument 1. The left side shows the state before removal of the internal fixation instrument 1, and the right side shows the state during removal. The diagram is schematic, and the length, size, and shape, including the aspect ratio, are exaggerated or omitted for the purpose of explanation. The distal end portion of the internal fixation instrument 1 is shown enlarged below. Furthermore, the positions of the separation instrument side thread 82 and the outer tube side thread 22, which are the motion direction conversion mechanism, are also changed from FIG. 1 to positions closer to the internal fixation instrument 1.

[0080] Referring to the left side of FIG. 2 , the tip of the internal fixation device 1 is embedded in bone cement 50 in a vertebral body 92. A groove 17, which will be described later in the “Details of the Internal Fixation Device” section, is formed at the tip of the internal fixation device 1, and bone cement 50 fills the groove 17. The groove 17 may be a spiral groove, a concentric groove, or an island-like recess. The internal fixation device 1 and the outer tube 2 are connected by connecting portions 12 and 21, and through-holes 19 and 29 (not shown in the figure) communicate with each other. The cement separation device 8 is configured so that, when inserted through the through-holes 19 and 29 that communicate when the internal fixation device 1 and the outer tube 2 are connected, the separation device side thread 82 engages with the thread 22 provided in the through-hole 29 of the outer tube 2. However, in the left-hand view, the separation device side thread 82 has not yet reached the position where it engages with the outer tube side thread 22.

[0081] The right side of Fig. 2 shows a state in which the threads 82 of the cement separation instrument 8 are screwed into the outer tube threads 22. When the cement separation instrument 8 is rotated from the state shown on the left side of Fig. 2, it is linearly pushed proximally along the central axis, and the tip of the cement separation instrument 8 advances linearly through the through-hole 19 of the internal fixation instrument 1 and then protrudes from the tip, applying a linear pushing force to the bone cement 50. This force separates the internal fixation instrument 1 from the bone cement 50. If part of the bone cement 50 has entered the through-hole 19 of the internal fixation instrument 1, that part of the bone cement 50 is pushed out and separated. Alternatively, although not shown, the bone cement in the through-hole 19 of the internal fixation instrument 1 may be removed in advance to the state shown in the figure by scraping it out with a sharp drill large enough to insert into the through-hole.

[0082] At this time, the internal fixation device 1 is removed while also destroying the bone cement 50 that has entered the groove 17 or recess at the tip of the internal fixation device 1. As shown in the enlarged view at the bottom left of Fig. 2, the bone cement 50 has entered and hardened in the groove 17 at the tip of the internal fixation device 1, preventing the bone cement 50 from dislodging. However, by separating the internal fixation device 1 with a linear force, the portion that has entered the groove 17 is destroyed and separated from the main body of the bone cement 50, as shown in the enlarged view at the bottom right of Fig. 2. At this time, in the drawing, the internal fixation device 1 is pushed distally (toward the back) in a linear direction during separation. However, depending on the loosening state of the internal fixation device 1, the pedicle 91, and the surrounding bone cement 50, the bone cement 50 may be pushed forward toward the anterior side of the vertebral body and separated (not shown). After the bone cement 50 has been separated from the internal fixation device 1, the cement separation device 8 is temporarily removed, and a driver (not shown; see, for example, the driver 3 described later in Embodiment 3) that engages with the head of the internal fixation device 1 is inserted into the through-hole 29 of the outer tube 2 and engaged with the head 11 of the internal fixation device 1. A rotational force is then applied to the internal fixation device 1 in the removal direction, thereby removing the internal fixation device 1 without resistance from the spine. Alternatively, the internal fixation device 1 may be removed by rotating it using the connected outer tube 2 in the direction opposite to the direction in which the tapping screw threads 15 were screwed into the pedicle 91, thereby using not only the linear force of the cement separation device 8 but also a rotational force. On the other hand, when the internal fixation device 1 is removed using only a linear force without using a rotational force, the tapping groove formed in the bone tunnel in the pedicle 91 is destroyed during removal.

[0083] When a hole formed in a predetermined shape by the cement molding part 72 at the tip of the cement molding instrument 7, which will be described later in embodiment 3, is formed in the bone cement 50 at the tip of the internal fixation instrument 1, the tip of the cement separating instrument 8 may be shaped to fit into that hole. Since a rotational force and a linear force can be applied to the bone cement 50, the rotational force of the cement separating instrument 8 can be transmitted to the bone cement 50 more effectively.

[0084] Alternatively, the tip of the cement separation instrument 8 may be a conical or hemispherical protrusion with a tapping screw thread. Figures 8 and 9 are enlarged views showing examples of the configuration of the tip portion of the cement separation instrument 8. As shown in Figure 8, the tip 81 of the cement separation instrument 8 includes a truncated conical region on which a helical screw thread is formed and a conical end portion at the tip. The truncated cone on which the helical screw thread is formed is inclined, for example, by ±10° around the central axis, for a total of 20°, and the end portion is inclined, for example, by ±45°, for a total of 90°. Figure 9 shows the tip 81 of another cement separation instrument 8 including a truncated conical region on which a helical screw thread is formed and a spherical portion at the tip. The truncated cone on which the helical screw thread is formed is inclined, for example, by ±5° around the central axis, for a total of 10°, and the end portion is hemispherical. The hemispherical end portion reduces the risk of damaging the bone cement 50 when the bone cement 50 is pushed to separate it from the internal fixation device 1. 8 and 9 are merely examples, and the angles and sizes can be changed as appropriate.

[0085] [Details of the Internal Fixation Device] The internal fixation device 1 constituting the treatment device 10 of the present invention will be described in more detail. The internal fixation device 1 is, for example, a medical screw, and is configured to be inserted from the pedicle into bone cement 50 filled in the vertebral body.

[0086] FIG. 10 is a cross-sectional view showing a schematic configuration example of the internal fixation device 1. The internal fixation device 1 comprises a head 11 and a shaft 14. The head 11 is provided with a connecting portion 12 to which the outer tube 2 is connected and a fitting portion 13 into which the fitting portion 33 of the driver 3 is fitted. The shaft 14 has a self-tapping thread 15 on the distal side (the side closer to the head). The self-tapping thread 15 is formed for tapping a bone hole formed in the pedicle to screw the internal fixation device 1 into place. The self-tapping thread 15 does not need to be formed to a position that contacts the head 11; it is sufficient that it engages with at least a portion of the pedicle into which it is screwed. The tip of the internal fixation device 1 is preferably blunted, and the shaft 14 preferably has a tapered portion 16 that tapers toward the proximal side. The procedure for inserting the internal fixation device 1 involves inserting a balloon catheter through the through-hole 19 of the internal fixation device 1, inflating the balloon, and then deflating and withdrawing it. The blunting of the tip of the internal fixation device 1 reduces the risk of damaging the balloon during this step. For example, the degree of blunting can be designed such that, for the tip of the internal fixation device 1 with an inner diameter of 3.7 to 3.9 mm and a wall thickness of 0.15 to 0.25 mm, the inner radius of curvature is 0.075 to 0.10 mm and the outer radius of curvature is 0.075 to 0.10 mm. Furthermore, the inclined portion 16 can reduce the resistance to separation when the internal fixation device 1 is separated from the bone cement.

[0087] FIG. 11 is a front view of the internal fixation device 1 of FIG. 10 . The shaft 14 of the internal fixation device 1 or its inclined portion 16 may have a spiral groove 17 formed on the outer periphery. The procedure for inserting the internal fixation device 1 includes a step of inserting the internal fixation device 1 into bone cement 50. At this time, the bone cement 50 has not yet hardened, so the internal fixation device 1 enters the spiral groove 17 when it is screwed in. Even if the internal fixation device 1 is first inserted to its final depth and then the bone cement 50 is filled, the tip of the internal fixation device 1 is covered with the filled bone cement 50, causing the same phenomenon. This reduces the risk of the bone cement 50 becoming dislodged. On the other hand, because the groove 17 is spiral, the internal fixation device 1 can be removed by rotating it along the groove. The resistance when removing the internal fixation device 1 is not as great as that of grooves with a chevron-shaped thread or an island-shaped groove.

[0088] It is more preferable that the spiral groove 17 of the internal fixation device 1 be formed with the same lead as the self-tapping thread 15. This allows the spiral groove 17 of the internal fixation device 1 to be smoothly inserted into the bone cement 50. When the internal fixation device 1 is screwed into (removed from) the bone cement 50, the distance traveled in the rotational and linear directions (depth direction) is determined by the lead of the self-tapping thread 15. Therefore, if the rotational and linear directions are the same, it is advantageous, particularly when removing the internal fixation device 1 after the bone cement 50 has hardened. Specifically, when removing the internal fixation device 1 from the bone cement 50 after the bone cement 50 has hardened, the self-tapping screw 15 on the distal side of the internal fixation device 1 and the spiral groove 17 at the tip have the same lead, so that the rotational force in the removal direction is more fully transmitted, reducing the risk of damaging the bone around the self-tapping thread 15 on the distal side of the internal fixation device 1 and preventing the internal fixation device 1 from spinning freely inside the bone, allowing for more stable removal. The spiral groove 17 of the internal fixation device 1 may be shallow on the proximal side and gradually deepen toward the distal side. This allows the bone cement 50 to more smoothly enter the groove when the internal fixation device 1 is screwed into the bone cement 50. The number of threads of the spiral groove 17 of the internal fixation device 1 may be smaller than the number of threads of the self-tapping screw thread 15. By reducing the number of threads of the groove 17, it is possible to adjust the amount of bone cement that enters the groove 17, thereby minimizing the risk of the internal fixation device 1 being accidentally detached from the bone cement 50 inside the body while maintaining an appropriate pull-out strength between the bone cement 50 and the internal fixation device 1 so that the internal fixation device 1 does not become unable to be removed. The number of threads of the spiral groove 17 can be adjusted taking into consideration prevention of dislodgment and resistance during removal, for example, by varying the number of threads on the proximal and distal sides of the shaft 14.

[0089] A concentric groove or an island-shaped recess may be formed at the distal end of the internal fixation device 1 instead of the spiral groove 17. As described above, if the spiral groove 17 is formed with the same lead as the tapping thread 15, the internal fixation device 1 penetrates into the bone cement 50 along the same trajectory as when the tapping thread 15 is screwed into the pedicle while tapping. This allows the bone cement 50 to more smoothly penetrate into the groove 17. However, when the bone cement 50 has not yet hardened and has a low viscosity, the bone cement 50 can penetrate even into a concentric groove or an island-shaped recess. This shape is formed to prevent the bone cement 50 from slipping out, but on the other hand, it also acts to make it difficult to remove the internal fixation device 1. It is recommended that the shape be appropriately designed and selected taking into consideration the trade-off between preventing the bone cement 50 from slipping out and facilitating the removal of the internal fixation device 1. For example, when the internal fixation device 1 can be inserted deeply into the bone cement 50, there is no need to be particularly concerned about preventing dislodgement, so it is sufficient to form shallow spiral grooves 17 or sparsely form island-shaped recesses. On the other hand, when it is expected that the internal fixation device 1 will not be inserted deeply, it is preferable to form deep grooves so that prevention of dislodgement takes priority.

[0090] FIG. 12 is a cross-sectional view schematically illustrating another configuration example of the internal fixation device 1, and FIG. 13 is a front view of the internal fixation device 1 of FIG. 12. The internal fixation device 1 does not have either a tapping thread 15 or a spiral groove 17. The bone hole formed in the pedicle may have a diameter large enough to allow the shaft 14 to pass through but not the head 11. Alternatively, the shaft 14 may be used to widen the bone hole before passing through. When the shaft 14 is inserted into the bone hole formed in the pedicle, the head 11 stops at the entrance of the bone hole, and the inclined portion 16 at the tip of the shaft 14 inserted through the bone hole is inserted into the bone cement 50 filled in the vertebral body. When the bone cement 50 hardens, the inclined portion 16 is fixed, and the hardened bone cement mass and the head 11 of the internal fixation device 1 sandwich both sides of the bone hole in the pedicle, supporting the bone cement 50 from the pedicle side and fixing it in the vertebral body. Unlike the examples of FIGS. 10 and 11, the shaft 14 of the internal fixation device 1 does not have grooves 17 or the like formed therein, and therefore the force of adhesion between the bone cement 50 and the internal fixation device 1 is weaker.

[0091] When the internal fixation device 1 can be inserted deeply into the bone cement 50, the risk of dislodging the bone cement mass is low and the force required for removal can be reduced even if an internal fixation device 1 with weak fixing strength is used as shown in Figures 12 and 13. On the other hand, when the internal fixation device 1 cannot be inserted deeply into the bone cement 50, it becomes more important to prevent dislodging of the bone cement mass, so an internal fixation device 1 having a spiral groove 17 or the like at the tip as shown in Figures 10 and 11 can be selected.

[0092] Furthermore, in order to adjust the adhesive strength with the bone cement 50, various configurations can be adopted for the inclined portion 16 of the internal fixation device 1.

[0093] 14 is a cross-sectional view schematically showing an example of the configuration of the inclined portion 16 of the shaft 14 of the internal fixation device. The shaft 14 may be configured to include multiple inclined portions 16 with different inclination angles. For example, the inclination angle may be configured to gradually increase toward the proximal side of the shaft 14. This makes it possible to adjust the thickness of the internal fixation device 1 and further facilitate removal of the internal fixation device 1 while maintaining its strength.

[0094] FIG. 14A shows a cross section of the entire internal fixation device 1, and (B) to (D) show various modified examples with enlarged views of the proximal side of the shaft 14. L0 indicates the length of the shaft 14 inserted into the bone cement 50 during a typical surgical procedure. L0 is approximately 2 cm. Even with a design where L0 = 2 cm, the insertion depth may be shallower (e.g., 0.5 cm) in some cases. The shaft 14 in (B) has a long, single-step taper (inclined portion 16). The long, inclined portion 16 has a uniform inclination angle throughout L0. The shaft 14 in (C) has a short, single-step taper (inclined portion 16) on the proximal side. When L0 = 2 cm, for example, L1 = 0.7 cm. The shaft 14 in (D) has an inclined portion 16 with a length L1 on the proximal side with a large inclination angle and an adjacent inclined portion 16 with a length L2 on the distal side with a smaller inclination angle. The number of taper steps and length can be changed as appropriate.

[0095] The configuration of the inclined portion of the shaft 14 is designed to provide appropriate stability, strength, and ease of insertion and removal, taking into consideration a variety of situations, such as when the bone cement 50 is not sufficiently filled, or when the bone cement 50 has hardened more than expected before the internal fixation device 1 is inserted. In this case, as shown in Figures 10 and 11, the number of spiral grooves 17 formed on the outer periphery of the shaft 14, or whether to use a chevron-shaped or trapezoidal protruding thread instead of the grooves 17, are also considered as important factors that affect the stability, strength, and ease of insertion and removal.

[0096] 15 and 16 are cross-sectional views schematically showing configuration examples of the connection portions 12 and 21 between the internal fixation device 1 and the outer tube 2. In the configuration example shown in Fig. 15, the connection portion 12 of the internal fixation device 1 is disposed on the outer periphery side, and the connection portion 21 of the outer tube 2 is disposed on the inner periphery side. In the configuration example shown in Fig. 16, the connection portion 12 of the internal fixation device 1 is disposed on the inner periphery side, and the connection portion 21 of the outer tube 2 is disposed on the outer periphery side. A screw thread is formed on each of the connection portions 12 and 21, and they are connected by being rotated and inserted.

[0097] If the internal fixation device 1 has a self-tapping thread 15 that can be screwed into the pedicle, the threads formed on the connection portions 12 and 21 should be configured with threads in the opposite direction to the self-tapping thread 15. For example, when the self-tapping thread 15 is screwed into the bone hole of the pedicle by rotating the internal fixation device 1 clockwise, a counterclockwise force must be applied to remove the device. Since the connection portions 12 and 21 must not loosen due to this counterclockwise force, they should be configured with threads in the opposite direction to the self-tapping thread 15. Furthermore, the rotation of the cement separation device 8 at this time should be clockwise, the same direction as the screwing of the self-tapping thread 15 into the bone hole of the pedicle. When the screwing direction of the tapping thread 15 of the internal fixation device 1 is clockwise, rotating the internal fixation device 1 counterclockwise applies a rotational force in the direction of removal, and when the cement separation device 8 is turned clockwise, which is the opposite of the counterclockwise rotation of the internal fixation device 1, this is converted into a force that moves linearly toward the tip of the internal fixation device 1, and both the rotational force and the linear force act to separate the internal fixation device 1 from the bone cement 50. Because the outer tube 2 connected to the internal fixation device 1 serves as a fulcrum, by the surgeon applying a counterclockwise force to the outer tube 2 connected to the internal fixation device 1, the internal fixation device 1 can be prevented from rotating clockwise together with the cement separation device 8. Furthermore, once the internal fixation device 1 has been separated from the bone cement 50, the tapping thread 15 of the internal fixation device 1 can be removed from the bone hole in the pedicle by turning the outer tube 2 counterclockwise, providing good alignment.

[0098] In summary, the connection between the internal fixation device 1 and the outer cylinder 2 does not loosen when the internal fixation device 1 is rotated in the direction of removal, and by applying a rotation to the cement separation device 8 in the opposite direction to the internal fixation device 1, the rotation applied to the cement separation device 8 is converted into a linear force that moves the cement separation device 8 in a straight line, which helps to separate the cement from the bone cement 50 and allows the internal fixation device 1 to be separated and removed more safely.

[0099] The "details of the internal fixation device" described here are not limited to the first embodiment, but can be similarly applied to other embodiments.

[0100] [Procedure for surgical procedure for removing the internal fixation device] FIG. 17 is an explanatory diagram showing an example of a procedure for surgical procedure for removing the internal fixation device 1 using the treatment device 10 of the first embodiment.

[0101] Step 1 ([1]): The skin is incised to expose the head of the internal fixation device 1 through the wound incision 93.

[0102] Step 2 ([2]): Connect the outer tube 2 to the head of the internal fixation device 1. At this time, if the tapping screw threads 15 on the outer periphery of the internal fixation device 1 are screwed clockwise into the pedicle 91 and fixed, and if threads in the opposite direction are formed on the connection parts 12 and 21, turn the outer tube 2 counterclockwise to connect it to the head of the internal fixation device 1. If the internal fixation device 1 can be removed by turning the connected outer tube 2 in the opposite direction (counterclockwise) to the direction in which the internal fixation device 1 was screwed in, remove it as is, and proceed to closure in Step 6 ([6]) without performing the subsequent steps.

[0103] Step 3 ([3]): The cement separation instrument 8 is inserted into the through-hole (the through-hole where the first through-hole 19 and the second through-hole 29 communicate) formed by connecting the internal fixation instrument 1 and the outer cylinder 2. Although not shown, if the through-hole 19 of the internal fixation instrument 1 is blocked with bone cement, bone fragments, scars, or other foreign matter, the foreign matter inside the through-hole 19 of the internal fixation instrument 1 can be excavated and removed in advance using a drill or the like, thereby making it possible to pass the cement separation instrument 8 through the through-hole.

[0104] Step 4 ([4]): The inserted cement separation instrument 8 is rotated to screw the threads 82 into the threads 22 of the outer cylinder 2, and the tip of the cement separation instrument 8 is advanced into the through-hole 19 of the internal fixation instrument 1. By advancing it further, the tip of the cement separation instrument 8 comes into contact with the bone cement 50. By further rotating the cement separation instrument 8 and advancing it deeper, the internal fixation instrument 1 is separated from the bone cement 50. The outer cylinder 2 connected to the internal fixation instrument 1 is rotated and pulled out, but if the tapping threads of the pedicle are not strong, it is also possible to pull out the instrument while destroying the inner wall of the pedicle bone tunnel.

[0105] Step 5 ([5]): The internal fixation device 1 is removed while the outer tube 2 and the cement separating device 8 remain connected. Although not shown in the drawings, after the internal fixation device 1 is separated from the bone cement 50, the cement separating device 8 can be removed once, and a driver or the like (for example, the driver 3 described later in embodiment 3) that engages with the head of the internal fixation device 1 can be inserted through the through-hole 29 of the outer tube 2 and engaged with the head of the internal fixation device 1. By applying a rotational force to the internal fixation device 1 in the removal direction, the internal fixation device 1 can be removed from the spine without resistance, although this is not shown in the drawings.

[0106] Step 6 ([6]): The wound opening 93 is sutured and closed.

[0107] As described above, the cement separating instrument 8 of the present invention is pushed out from the internal fixation instrument 1 using the outer tube 2 connected to the internal fixation instrument 1 as a fulcrum. This allows the internal fixation instrument 1 to be separated from the bone cement 50 and removed without being affected by the strength of adhesion (adhesion) between the bone cement 50 and the surrounding body tissues. If it is necessary to remove the bone cement 50 from the vertebral body 92, after removing the internal fixation instrument 1 in step 5 ([5]), another skin incision is used to approach the anterior and lateral sides of the vertebral body, and the bone cement 50 is removed from the anterior and lateral sides. In steps 3 and 4 ([3] to [4]), the bone cement 50 is separated from the internal fixation instrument 1 by a linear force using the outer tube 2 connected to the internal fixation instrument 1 as a fulcrum. Therefore, the separating force acts only between the internal fixation instrument 1 and the bone cement 50. By having the surgeon hold the outer tube 2 connected to the internal fixation instrument 1, the risk of the internal fixation instrument 1 being moved by a strong force in the direction of removal within the vertebral body 92 is reduced.

[0108] FIG. 18 is an explanatory diagram showing another example of the procedure for the surgical procedure for removing the internal fixation device 1 using the treatment device 10 of embodiment 1. Steps 1 and 2 ([1] and [2]) are the same as those in the example described above with reference to FIG. 17 . Steps 3 ([3]) and after are different. In the example of FIG. 17 , the internal fixation device 1 is pushed out distally (toward the back) in a straight line during separation. However, depending on the loosening state of the internal fixation device 1 and the surrounding bone cement 50, the internal fixation device 1 may remain in position, and the bone cement 50 may be pushed out anterior to the vertebral body and separated ( FIG. 18 [3]). That is, step 3 ([3]) and after are as follows.

[0109] Step 3 ([3]): The cement separating instrument 8 is inserted into the through-hole (the through-hole communicating with the first through-hole 19 and the second through-hole 29) formed by connecting the internal fixation device 1 and the outer tube 2, and when the cement separating instrument 8 is rotated while the outer tube 2 restrains the rotation of the internal fixation device 1, the tip of the cement separating instrument 8 protrudes from the tip of the internal fixation device 1 and pushes the bone cement 50, separating it and pushing it out in front of the vertebral body 92 (the opposite side from the pedicle 91).

[0110] Step 4 ([4]): Remove the cement separation instrument 8.

[0111] Step 5 ([5]): The outer cylinder 2 is rotated to remove the internal fixation device 1 from the pedicle 91.

[0112] Step 6 ([6]): The wound opening 93 is sutured and closed.

[0113] In steps 4 and 5 ([4] to [5]), the cement separating instrument 8 may not be removed first, but the outer tube 2 and the internal fixation instrument 1 may be removed together while remaining connected.

[0114] [Embodiment 2] In the treatment instrument 10 of embodiment 1, the motion direction conversion mechanism is configured by a screw structure (the outer tube side thread 22 and the separation instrument side thread 82) provided on the outer tube 2 and the cement separation instrument 8, but it can also be configured by a screw structure (the internal fixation instrument side thread 18 and the separation instrument side thread 82) provided on the internal fixation instrument 1 and the cement separation instrument 8.

[0115] 3 is an explanatory diagram schematically illustrating a cross-sectional structure to illustrate a configuration example of the treatment instrument 10 of Embodiment 2. The shaft 84 of the cement separation instrument 8 has a separation instrument-side thread 82 on its outer periphery, and the motion direction conversion mechanism is formed by the engagement of the separation instrument-side thread 82 with the internal fixation instrument-side thread 18 formed in the through-hole 19 of the internal fixation instrument 1. This allows the fulcrum of the linear force that moves the cement separation instrument 8 linearly to be set within the internal fixation instrument 1, allowing the internal fixation instrument 1 to be safely separated and removed from the bone cement 50. When the internal fixation instrument 1 and the bone cement 50 are strongly fixed, a large force is required for separation. However, the internal fixation instrument 1 itself to be separated serves as the fulcrum, allowing a force that linearly separates the internal fixation instrument 1 and the bone cement 50 to be directly applied.

[0116] As in the first embodiment, when the internal fixation device 1 has a tapping thread 15 on its outer periphery and the thread structure connecting the internal fixation device 1 and the outer tube 2 is threaded in the opposite direction to the tapping thread 15 provided on the outer periphery of the internal fixation device 1, it is preferable that the thread structure formed by the internal fixation device-side thread 18 and the separation device-side thread 82 be threaded in the same direction as the tapping thread 15. For example, when the screwing direction of the tapping thread 15 of the internal fixation device 1 is clockwise, a rotational force in the removal direction is applied by rotating the outer tube 2 counterclockwise, which is the opposite direction to the clockwise direction in which the internal fixation device 1 rotates, and when the cement separation device 8 is turned clockwise, which is the opposite direction to the counterclockwise direction in which the internal fixation device 1 rotates, this is converted into a force that moves linearly toward the tip of the internal fixation device 1, and both the rotational force and the linear force act to separate the internal fixation device 1 from the bone cement 50.

[0117] Furthermore, even if the internal fixation device 1 does not have the self-tapping threads 15 on its outer periphery and is linearly inserted into the bone hole in the pedicle, or even if the self-tapping threads 15 are present but the bone hole in the pedicle is not strong enough to remove the internal fixation device 1 without rotating it, the thread structure formed by the internal fixation device-side threads 18 and the separation device-side threads 82 should be in the opposite direction to the thread structure connecting the internal fixation device 1 and the outer tube 2. When separating the internal fixation device 1, it is necessary to prevent the internal fixation device 1 from rotating with a force in the opposite direction to the direction in which the cement separation device 8 is rotated, and therefore, even if the outer tube 2 is connected to the internal fixation device 1 at that time, the direction in which the connection will not loosen.

[0118] The cement separation instrument 8 preferably has a tip portion 81 that protrudes from the tip of the internal fixation instrument 1 when the separation instrument-side threads 82 are screwed into the internal fixation instrument-side threads 18. When the cement separation instrument 8 protrudes from the tip of the internal fixation instrument 1, it pushes the bone cement 50 at the tip of the internal fixation instrument 1, assisting in separation. On the other hand, if the proximal side of the through-hole 19 of the internal fixation instrument 1 is filled with bone cement 50, the cement separation instrument 8 does not necessarily have to be long enough to protrude from the tip of the internal fixation instrument 1. Furthermore, although not shown, even if the through-hole 19 of the internal fixation instrument 1 is blocked with bone cement, bone fragments, scars, or other foreign matter, it becomes possible to insert the cement separation instrument 8 into the through-hole 19 by drilling and removing the foreign matter in advance.

[0119] It is more preferable that the treatment instrument 10 of the second embodiment further includes a cap 9 that is inserted into the opening of the head 11 of the internal fixation instrument 1. The same applies to the treatment instrument 10 of the first embodiment. This makes it possible to prevent the head 11 of the internal fixation instrument 1 and the through-hole 19 from being blocked by bone cement, bone fragments, scar tissue, or other foreign matter.

[0120] The cap 9 may include not only the head 11 of the internal fixation device 1 but also a shaft 94 to be inserted into the through-hole 19. The shaft 94 may have a thread 98 on its outer periphery that engages with the above-mentioned internal fixation device thread 18. In surgery to insert the internal fixation device 1 into the bone cement 50 inside the vertebral body from the pedicle, fitting the cap 9 after inserting the internal fixation device 1 reduces the risk of bone cement, bone fragments, or other foreign matter getting in and causing eschar, and also reduces the risk of the cap 9 coming off after surgery.

[0121] FIG. 4 is an explanatory diagram showing an example configuration of the cap 9. The cap 9 is configured to be inserted into the opening of the head 11 of the internal fixation device 1 to close the opening. The cap 9 is more likely to be stable in the inserted state if it has a shaft 94 that is inserted into the through-hole 19 of the internal fixation device 1. When the internal fixation device 1 is formed with threads 18 that engage with the threads 82 of the cement separation device 8, the shaft 94 may further be formed with threads 98 for cap fixation that engage with the threads 18 of the internal fixation device 1. Screwing the cap 9 can significantly reduce the risk of it coming off after surgery. In this case, the head of the cap 9 may be formed with a groove that can fit a Phillips or flathead screwdriver, a hex wrench, or the like, so that the threads 98 can be screwed into the threads 18 of the internal fixation device 1 to attach or loosen the cap 9.

[0122] The head of the cap 9 can be sized to tightly close the opening of the head 11 of the internal fixation device 1, or a gap large enough to allow the connection portion 21 of the outer tube 2 to be connected to the connection portion 12 may be left. If the head 11 of the internal fixation device 1 has an engaging portion 13 for a driver 3 (not shown) used to screw the internal fixation device 1 into the bone cement 50, it is advisable to close this portion. There is an option to use the driver 3 when removing the internal fixation device 1, and in that case, this can prevent the engaging portion 13 from being blocked by scar tissue or the like.

[0123] FIG. 5 is an explanatory diagram showing another configuration example of the cap 9. While the cap 9 in FIG. 4 is fixed to the internal fixation device 1, it may be configured to be fixed to the bone cement 50 instead of or in addition to this. A tip portion 99 is formed on the shaft 94 of the cap 9, protruding from the tip of the internal fixation device 1 when the cap 9 is attached to the internal fixation device 1. The tip portion 99 may be formed with a screw thread, a tapping screw thread, or a screw groove to be embedded in the bone cement 50, or may be formed with a simple island-shaped or ring-shaped convex or concave portion, or may be flat without any irregularities. Furthermore, as described in embodiment 3, when a cement molding device 7 is protruded from the tip of the internal fixation device 1 inserted into the bone cement 50 to form a hole in the bone cement 50 and mold it into a predetermined shape, the tip portion 99 of the cap 9 may also be formed to fit into the hole.

[0124] Although Figure 5 shows an embodiment in which the cap 9 does not have a thread 98 on the side thereof that engages with the thread 18 of the internal fixation device 1, the cap 9 may have a thread 98 on the side thereof, similar to the cap 9 in Figure 4 .

[0125] In the surgical procedure for implanting the internal fixation device 1, the cap 9 may be inserted after the internal fixation device 1 has been inserted with a driver into the bone cement 50 injected into the vertebral body, or may be inserted at the same time as the internal fixation device 1 is inserted into the bone cement 50. In this case, an improved driver 3 can be used so that the cap 9 can be rotated together with the internal fixation device 1 in a fitted state.

[0126] FIG. 20 is a cross-sectional view showing an example of the configuration of the connection portion of the improved driver 3 with the internal fixation device 1 and the cap 9. The upper side shows a front cross-section, and the lower side shows its X-X' cross-section. The improved driver 3 includes a fitting portion 33 that fits into the fitting portion 13 of the head 11 of the internal fixation device 1, as well as a cap driver 35 that rotates the cap 9. As shown in FIG. 20, the fitting portions 33 and 13 of the improved driver 3 and the internal fixation device 1 can be fitted together using, for example, a hex wrench, and the cap driver 35 can be configured, for example, as a Phillips head screwdriver that fits into a Phillips head screwdriver groove formed in the head of the cap 9 to rotate the cap 9. When the fitting portions 33 and 13 of the improved driver 3 and the internal fixation device 1 are fitted together, the Phillips head screwdriver that is the cap driver 35 fits into the Phillips head screwdriver groove in the head of the cap 9. The rotation of the improved driver 3 is transmitted to the cap 9 as well as the internal fixation device 1. The shapes of the fitting portions 33 and 13 and the cap driver 35 may be any shape as long as they are configured to fit together and transmit rotational force, and may be, for example, star-shaped, cross-shaped, or the shape of a flathead screwdriver. Using this improved driver 3, the cap driver 35 is fitted into the cap 9 inserted into the internal fixation device 1, and further, the fitting portion 33 is fitted into the fitting portion 13 of the head 11 of the internal fixation device 1, thereby rotating the cap 9 and the internal fixation device 1 together and screwing them into the bone cement 50.

[0127] [Procedure for surgical procedure for removing the internal fixation device] FIG. 19 is an explanatory diagram showing an example of a procedure for surgical procedure for removing the internal fixation device 1 using the treatment device 10 of the second embodiment.

[0128] Step 1 ([1]): The skin is incised to expose the head 11 of the internal fixation device 1 from the wound incision 93. At this time, the head of the cap 9 attached to the internal fixation device 1 is also exposed.

[0129] Step 2 ([2]): Remove the cap 9 from the internal fixation device 1. If it is screwed in as in the example shown in Figures 4 and 5, loosen the screw and remove the cap. Before or after removing the cap 9, connect the outer tube 2 to the head 11 of the internal fixation device 1.

[0130] Step 3 ([3]): The cement separating instrument 8 is inserted into the through-hole 19 of the internal fixation instrument 1 and the through-hole 29 of the outer cylinder 2. The threads 82 of the cement separating instrument 8 are engaged with the threads 18 provided in the through-hole 19 of the internal fixation instrument 1.

[0131] Step 4 ([4]): The inserted cement separation instrument 8 is rotated to screw the threads 82 into the threads 18 of the internal fixation instrument 1, and the tip of the cement separation instrument 8 is advanced into the through-hole 19. By advancing it further, the tip of the cement separation instrument 8 comes into contact with the bone cement 50. By further rotating the cement separation instrument 8 and advancing it deeper, the internal fixation instrument 1 is separated from the bone cement 50. When rotating the cement separation instrument 8, the surgeon may apply force to the outer cylinder 2 to prevent the internal fixation instrument 1 from rotating in the same direction as the cement separation instrument 8, or may actively rotate the outer cylinder 2 in the opposite direction to the rotation of the cement separation instrument 8, thereby applying a rotational force to the internal fixation instrument 1 via the outer cylinder 2 so that the internal fixation instrument 1 is removed from the pedicle 92 and bone cement 50.

[0132] Step 5 ([5]): With the cement separation instrument 8 still connected, the internal fixation instrument 1 is removed. Although not shown in the drawings, after the internal fixation instrument 1 has been separated from the bone cement 50, the cement separation instrument 8 may be removed, a driver 3 may be inserted and engaged with the head 11 of the internal fixation instrument 1, and the internal fixation instrument 1 may be removed from the spine by rotating the tapping screw threads 15 of the internal fixation instrument 1 in the removal direction using the driver 3.

[0133] Step 6 ([6]): The wound opening 93 is sutured and closed.

[0134] As described above, the cement separating instrument 8 of the present invention is pushed out using the internal fixation instrument 1 as a fulcrum, and therefore can separate and remove the internal fixation instrument 1 from the bone cement 50 without being affected by the strength of adhesion (adhesion) between the bone cement 50 and the surrounding body tissues of the internal fixation instrument 1. In the second embodiment, as in the first embodiment, if it is necessary to remove the bone cement 50 from the vertebral body 92, this is done after removing the internal fixation instrument 1 in step 5 ([5]). Since the bone cement 50 is separated from the internal fixation instrument 1 by a linear force using the internal fixation instrument 1 as a fulcrum in steps 3 and 4 ([3] to [4]), the separating force acts only between the internal fixation instrument 1 and the bone cement 50, and the risk of damaging the bones, spinal nerves, nerve roots, etc. around the internal fixation instrument or bone cement when removing the internal fixation instrument from the vertebral body 92 is reduced.

[0135] [Embodiment 3] Fig. 6 is an explanatory diagram showing a schematic cross-sectional structure to illustrate an example configuration of a treatment instrument 10 of embodiment 3. The treatment instrument 10 may further include a driver 3, a cement filling instrument, and a cement molding instrument 7. Fig. 6 shows an example of a cement filling instrument consisting of a filling tube 5 and a pushing rod 6, but the cement filling instrument may also be an instrument in which a syringe or other instrument for injecting and pushing out bone cement into the filling tube 5 is connected to the filling tube 5. Below, an example will be described in which the cement filling instrument consists of the filling tube 5 and the pushing rod 6.

[0136] The internal fixation device 1 has a fitting portion 13 on the head 11. A driver 3 can be passed through the through-hole 29 of the outer tube 2. The driver 3 has a fitting portion 33 that fits with the fitting portion 13 of the internal fixation device 1 when the driver 3 is inserted into the through-hole 29 with the internal fixation device 1 and outer tube 2 connected, and a through-hole 39 that communicates with the through-hole 19 of the internal fixation device 1 when they are fitted. A handle 38 is provided at the distal end. The fitting portions 13 and 33 are, for example, like a regular hexagonal groove and a regular hexagonal prism of a hexagonal wrench, and the rotation of the driver 3 can be transmitted to the internal fixation device 1 by fitting together.

[0137] The cement filling tool comprises a filling tube 5 and a pusher rod 6. The filling tube 5 is tubular, allowing the pusher rod 6 to pass through, and bone cement pre-filled in the tube can be pushed out from its tip by the pusher rod 6. Grips 58 and 68 are preferably provided at the distal ends of the filling tube 5 and the pusher rod 6, respectively. The filling tube 5 and the pusher rod 6 are configured to protrude from the tip of the internal fixation tool 1 through the through-holes 19 and 29 that communicate when the internal fixation tool 1 and the outer tube 2 are connected to each other, and also through the through-hole that communicates with the through-hole 39 of the driver 3 when the driver 3 is connected. The bone cement pre-filled in the filling tube 5 can be pushed out by the pusher rod 6 into the through-hole 19 of the internal fixation tool 1 or into the vertebral body proximal to the tip, and injected into the vertebral bone. When the cement filling device consists of a filling tube 5 and a cement injection device such as a syringe, the bone cement injected into the filling tube 5 can be pushed out by the cement injection device such as a syringe into the through-hole 19 of the internal fixation device 1 or into the vertebral body proximal to the tip, and then injected into the vertebral bone.

[0138] The cement molding instrument 7 is configured to be inserted into a through-hole 39 communicating with the through-hole 19 and protrude from the proximal end of the internal fixation instrument 1 when the internal fixation instrument 1 and the outer cylinder 2 are connected and the driver 3 is inserted into the through-hole 29 of the outer cylinder 2 to engage the fitting portions 13 and 33 and connect the internal fixation instrument 1. The protruding portion is provided with a molding portion 72 that forms a hole in the bone cement 50 at the tip of the internal fixation instrument 1 and molds it into a predetermined shape.

[0139] The tip 81 of the cement separation instrument 8 (not shown in FIG. 6; see FIG. 1 or FIG. 3) is inserted into the hole formed by the molding portion 72 of the cement molding instrument 7 in the bone cement mass injected into the vertebral body by the cement filling instrument (5, 6).

[0140] The molding part 72 of the cement molding instrument 7 may be, for example, a triangular, quadrangular, hexagonal, or other rectangular prism, a flat plate with a straight or cross-shaped cross section, or a combination thereof, and the tip 81 of the cement separating instrument 8 may be shaped to fit into a hole formed by the molding part 72, thereby preventing the bone cement mass from rotating within the vertebral body. Alternatively, the molding part 72 of the cement molding instrument 7 may be, for example, a hemispherical, cylindrical, conical, or truncated conical shape with a circular cross section, and may be formed with a screw thread or thread groove.

[0141] FIG. 7 is an explanatory diagram showing exemplary configurations of the distal end portions of the cement molding instrument 7 and the cement separating instrument 8. The molding 72 of the cement molding instrument 7 and the distal end portion 81 of the cement separating instrument 8 are shown protruding from the distal end of the internal fixation instrument 1. A spiral groove 17 may be formed at the distal end of the internal fixation instrument 1. A spiral ridge may be formed instead of a groove. Alternatively, as described in the "Details of the Internal Fixation Instrument" section, a concentric groove or an island-shaped recess may be formed. This allows the fixation strength of the internal fixation instrument 1 to be adjusted by taking into account the balance between the risk of bone cement mass dislodging and the strength of removal. The spiral groove 17 or ridge formed at the distal end of the internal fixation instrument 1 may be formed with the same lead as the tapping screw thread 15 (not shown in FIG. 7 ) provided on the distal side of the same internal fixation instrument 1. This allows the force generated by the rotational force of the bone cement separating instrument 8 to be more effectively transmitted in the direction of separating the bone cement from the internal fixation instrument 1, making it easier to remove the internal fixation instrument 1.

[0142] Although FIG. 7 illustrates the thread formed on the distal end 81 of the cement separation instrument 8 with the same lead as the spiral groove 17 formed in the distal portion of the internal fixation instrument 1, the lead may be different. The spiral groove 17 of the internal fixation instrument 1 is often formed with the same lead as not only the tapping thread 15 (not shown in FIG. 7 ) provided on the distal side, but also the thread 82 provided on the outer periphery of the shaft 84 of the cement separation instrument 8. When a large force is required to extrude the bone cement, it is important to set the lead of the thread 82 provided on the outer periphery of the shaft 84 of the cement separation instrument 8 more precisely so that a larger driving force can be transmitted to the distal end of the cement separation instrument 8 for a given torque value applied when rotating the cement separation instrument 8. Accordingly, the lead of the spiral groove 17 of the internal fixation instrument 1 is also set more precisely. The shape of the tapping thread 15 at the tip 81 of the cement separation instrument 8 may be larger than the lead of the thread 82 on the separation instrument side, as long as it can apply a force to grip and rotate the bone cement in addition to the driving force to push the bone cement.

[0143] In the example A in the upper row, the molding portion 72 of the cement molding instrument 7 and the tip portion 81 of the cement separating instrument 8 are both truncated cones of the same size, with a spiral thread formed around their periphery. This spiral thread may be formed with the same lead as the spiral groove 17 at the tip portion of the internal fixation instrument 1. Furthermore, it may be formed to follow the same path. By forming the spiral thread with the same lead, when the internal fixation instrument 1 is removed by rotating it in the reverse direction from fixation to the pedicle with the tapping screw thread 15, it can be removed from the bone cement 50 with the same amount of rotation and thrust distance applied to the bone cement by the tip of the cement separating instrument 8. This does not change the positional relationship between the pedicle and the bone cement mass, thereby reducing the risk of the bone cement mass moving to an unexpected position or direction and damaging surrounding body tissue.

[0144] In the example B in the middle row, the molding portion 72 of the cement molding instrument 7 and the tip portion 81 of the cement separating instrument 8 are both truncated cones of the same size, and are also formed with a spiral thread around the periphery, just like in example A. The thread of example A is chevron-shaped when viewed in a cross section perpendicular to the direction of rotation and advancement, but the thread of example B is trapezoidal when viewed in a cross section perpendicular to the direction of rotation and advancement.

[0145] In the example C in the lower row, the molding portion 72 of the cement molding instrument 7 and the tip portion 81 of the cement separating instrument 8 are both truncated cones of the same size, but differ in whether they have a thread or not. The molding portion 72 of the cement molding instrument 7 does not have a thread around its periphery, but a self-tapping thread is formed around the tip portion 81 of the cement separating instrument 8. The hole formed in the molding portion 72 of the cement molding instrument 7 is circular in plan view, and rotation cannot be suppressed. By providing a self-tapping thread on the tip portion 81 of the cement separating instrument 8, rotation of the bone cement mass can be suppressed.

[0146] Although examples of combinations of cement molding tools have been shown, these are merely examples, and any combination including sizes and shapes may be used.

[0147] [Embodiment 4] The outer cylinder 2 of Embodiment 2 described with reference to Fig. 3 can be replaced by a driver 3 of Embodiment 4. The driver 3 has a shaft 34, a fitting portion 33 that fits with the fitting portion 13 of the internal fixation device 1, and a through-hole 39 that communicates with the through-hole 19 of the internal fixation device 1 when fitted. A handle 38 may be provided at the distal end. The fitting portions 13 and 33 have a relationship similar to that of a regular hexagonal groove and a regular hexagonal prism of a hexagonal wrench, for example, and the rotation of the driver 3 can be transmitted to the internal fixation device 1 by fitting them together.

[0148] 21 is an explanatory diagram schematically illustrating the cross-sectional structure of the treatment instrument of Embodiment 4. As in Embodiment 2, the shaft 84 of the cement separation instrument 8 has a separation instrument-side thread 82 on its outer periphery, and the motion direction conversion mechanism is configured by the engagement of the separation instrument-side thread 82 with the internal fixation instrument-side thread 18 formed in the through-hole 19 of the internal fixation instrument 1. This allows the fulcrum of the linear force that moves the cement separation instrument 8 linearly to be set within the internal fixation instrument 1, allowing the internal fixation instrument 1 to be safely separated and removed from the bone cement 50. When the internal fixation instrument 1 or the bone cement 50 is strongly adhered, a large force is required for separation. However, the internal fixation instrument 1 itself to be separated serves as the fulcrum, allowing a force that linearly separates the internal fixation instrument 1 and the bone cement 50 to be directly applied. The structure of the cement separation instrument 8 is similar to that of the cement separation instrument 8 exemplified in Embodiment 2.

[0149] The driver 3 of this fourth embodiment has a shaft 34 and a through-hole 39 corresponding to the shaft 24 and through-hole 29 of the outer tube 2, respectively. The driver 3 has a fitting portion 33 at its proximal end that connects to the fitting portion 13 of the head 11 of the internal fixation device 1, corresponding to the connecting portion 21 of the outer tube 2. When inserted linearly along the central axis, the fitting portions 13 and 33 fit together and connect. This allows the cement separation device 8 to be rotated to protrude from the tip of the internal fixation device 1 and prevent rotation of the internal fixation device 1 when separating the bone cement. Furthermore, the internal fixation device 1 can be removed from the pedicle into which it has been threaded by rotating the internal fixation device 1 in the opposite direction to the threading of the tapping screw thread 15. Unlike the connection between the outer tube 2 and the internal fixation device 1, the connection between the driver 3 and the internal fixation device 1 is not linear along the central axis. However, after it leaves the pedicle, the connected internal fixation device 1 can be easily removed by pulling the cement separation device 8 linearly.

[0150] As described above, the instrument described as the outer tube 2 in embodiments 1 and 2 can be replaced by another instrument (for example, driver 3 in this embodiment 4) that has components corresponding to the shaft 24, through hole 29, and connecting portion 21.

[0151] Similar to the second embodiment, the treatment instrument 10 of the fourth embodiment preferably further includes a cap 9 that is inserted into the opening of the head 11 of the internal fixation instrument 1. This makes it possible to prevent the head 11 of the internal fixation instrument 1 and the through-hole 19 from being blocked by bone cement, bone fragments, scar tissue, or other foreign matter. A detailed description thereof will be omitted.

[0152] [Procedure for surgical procedure for removing the internal fixation device] FIG. 22 is an explanatory diagram showing an example of the procedure for surgical procedure for removing the internal fixation device 1 using the treatment device 10 of the fourth embodiment.

[0153] Step 1 ([1]): The skin is incised, and the head 11 of the internal fixation device 1 is exposed from the wound incision 93. At this time, if a cap 9 is attached to the internal fixation device 1, the head of the internal fixation device 1 is also exposed. The cap 9 is removed from the internal fixation device 1 in the same manner as in the other embodiments.

[0154] Step 2 ([2]): The fitting portion 33 at the tip of the driver 3 is fitted into and connected to the fitting portion 13 at the head of the internal fixation device 1. Although not shown in the figure, a guide pin may be inserted into the through-hole 19 of the internal fixation device 1, and the through-hole 39 of the driver 3 may be introduced along the guide pin, thereby guiding the fitting portion 33 into the fitting portion 13 at the head of the internal fixation device 1.

[0155] Step 3 ([3]): Since the through-hole 19 of the internal fixation device 1 and the through-hole 39 of the driver 3 are connected, the cement separating device 8 is inserted into the connected through-holes 19 and 39, and the threads 82 of the cement separating device 8 are engaged with the threads 18 provided in the through-hole 19 of the internal fixation device 1. At this time, the driver 3, instead of the outer tube 2, functions as a guide for inserting the cement separating device 8.

[0156] Step 4 ([4]): The inserted cement separation instrument 8 is rotated to screw the threads 82 into the threads 18 of the internal fixation instrument 1, and the tip of the cement separation instrument 8 is advanced into the through-hole 19. By advancing it further, the tip of the cement separation instrument 8 comes into contact with the bone cement 50. By further rotating the cement separation instrument 8 and advancing it deeper, the internal fixation instrument 1 is separated from the bone cement 50. When rotating the cement separation instrument 8, the surgeon may apply force to the driver 3 to prevent the internal fixation instrument 1 from rotating in the same direction as the cement separation instrument 8, or may actively rotate the driver 3 in the opposite direction to the rotation of the cement separation instrument 8, thereby applying a rotational force that removes the internal fixation instrument 1 from the pedicle 91 and bone cement 50.

[0157] Step 5 ([5]): With the cement separation device 8 still connected, the internal fixation device 1 is removed.

[0158] Step 6 ([6]): The wound opening 93 is sutured and closed.

[0159] As described above, the cement separating instrument 8 of the present invention is pushed out using the internal fixation instrument 1 as a fulcrum, and therefore can separate and remove the internal fixation instrument 1 from the bone cement 50 without being affected by the strength of adhesion (adhesion) between the bone cement 50 and the surrounding body tissues. In this embodiment 4, as in the first and second embodiments, if it is necessary to remove the bone cement 50 from the vertebral body 92, this is done after removing the internal fixation instrument 1 in step 5 ([5]). Since the bone cement 50 is separated from the internal fixation instrument 1 by a linear force using the internal fixation instrument 1 as a fulcrum in steps 3 and 4 ([3] to [4]), the separating force acts only between the internal fixation instrument 1 and the bone cement 50, and the risk of damaging the bones, spinal nerves, nerve roots, etc. around the internal fixation instrument 1 or the bone cement 50, which may occur when removing the internal fixation instrument from the vertebral body 92, is reduced.

[0160] While the invention made by the present inventor has been specifically described above based on the embodiments, the present invention is not limited thereto and, needless to say, can be modified in various ways without departing from the spirit and scope of the invention. For example, in the third embodiment, instead of the cement molding tool 7, the tip of the pusher rod 6 of the cement filling tool can be configured to protrude from the filling tube, and this portion can serve as the molding part 62 that forms a hole in the bone cement 50 at the tip of the internal fixation tool 1 and shapes it into a predetermined shape. Alternatively, instead of the cement molding tool 7, when the internal fixation tool 1 and the cap 9 are inserted into the bone cement in an integrated state, the tip of the cap 9 can be configured to protrude from the tip of the internal fixation tool 1 and form a hole in the bone cement and shape it into a predetermined shape.

[0161] The present invention relates to a treatment device used in percutaneous vertebroplasty, and is particularly suitable for use in surgery in which cement is filled inside the affected bone in advance and an internal fixation device (screw) that is screwed into the cement from the outside of the bone is removed.

[0162] REFERENCE SIGNS LIST 1 Internal fixation device 2 Outer tube 3 Driver 5 Filling tube 6 Pusher rod 7 Cement molding device 8 Cement separation device 9 Cap 10 Treatment device 11 Head 12, 21 Connection portion 13, 33 Fitting portion 14, 24, 34, 84, 94 Shaft 15, 85 Tapping thread 16 Inclined portion 17 Groove 18 Internal fixation device side thread 19, 29, 39, 49 Through hole 22 Outer tube side thread 35 Cap driving portion 82 Separation device side thread 98 (for cap fixation) thread 50 Bone cement 28, 38, 88 Handle 58, 68 Grip 62, 72 Molding portion 81, 99 Tip portion 90 Skin 91 Pedicle 92 Vertebral body 93 Retraction portion

Claims

1. A treatment instrument comprising an internal fixation instrument to be inserted into a vertebral body through a pedicle, an outer cylinder, and a cement separation instrument, wherein the internal fixation instrument has a head, a first shaft extending from the head to a proximal end, and a first through-hole passing through the central axis of the first shaft, the outer cylinder having a connecting portion connected to the head of the internal fixation instrument at its proximal end, a second shaft extending from its distal end to the proximal end, and a second through-hole that communicates with the first through-hole when connected to the internal fixation instrument, the cement separation instrument having a third shaft inserted into the communicating first and second through-holes, and the treatment instrument comprising a motion direction conversion mechanism that is inserted into the first and second through-holes that communicate with the cement separation instrument and converts a rotational force rotating around the central axis of the first through-hole into a linear force that moves the cement separation instrument in a straight line along the central axis, with the internal fixation instrument or the outer cylinder connected to the internal fixation instrument as a fulcrum.

2. A treatment instrument according to claim 1, wherein the third shaft of the cement separating instrument has a separating instrument side thread on its outer periphery, the outer cylinder has an outer cylinder side thread in the second through hole that engages with the separating instrument side thread, and the motion direction conversion mechanism is formed by the engagement of the outer cylinder side thread and the separating instrument side thread.

3. A treatment instrument according to claim 2, wherein the third shaft of the cement separation instrument has a tip portion that protrudes from the tip of the internal fixation instrument when inserted into the communicating first and second through holes.

4. A treatment instrument according to claim 1, wherein the third shaft of the cement separation instrument has a separation instrument side thread on its outer periphery, the internal fixation instrument has an internal fixation instrument side thread within the first through-hole that engages with the separation instrument side thread, and the motion direction conversion mechanism is formed by the engagement of the internal fixation instrument side thread and the separation instrument side thread.

5. A treatment instrument according to claim 4, wherein the third shaft of the cement separation instrument further has a tip portion that protrudes from the tip of the internal fixation instrument when inserted into the communicating first and second through holes.

6. The treatment device according to claim 1, further comprising a cap, the cap being inserted into the opening in the head of the internal fixation device.

7. A treatment device according to claim 6, wherein the cap has a fourth shaft that is inserted into the first through-hole of the internal fixation device.

8. A treatment instrument according to claim 7, wherein the fourth shaft has a tapping structure at its tip.

9. A treatment instrument according to any one of claims 1 to 8, wherein the internal fixation instrument has a tapping screw thread on the outer periphery of the first shaft that can be screwed into the pedicle in the same direction as the rotation that causes the cement separation instrument to move straight along the central axis by the motion direction conversion mechanism, and the connection part of the outer cylinder is connected to the head of the internal fixation instrument by a screw in the opposite direction to the tapping screw thread.

10. In claim 3 or claim 5, the treatment instrument further includes a driver, a cement filling instrument, and a cement molding instrument, wherein the internal fixation instrument has a first fitting portion at the head, and the second through-hole of the outer cylinder is capable of passing the driver, the driver has a second fitting portion that fits with the first fitting portion of the internal fixation instrument when the internal fixation instrument and the outer cylinder are connected and the driver is inserted into the second through-hole, and has a third through-hole that communicates with the first through-hole when fitted, and the cement filling instrument is inserted into the first and third through-holes that communicate when the internal fixation instrument and the outer cylinder are connected and the driver is inserted into the second through-hole and the first and second fitting portions fit together to connect with the internal fixation instrument, and is capable of injecting bone cement into the vertebral bone from the proximal end of the internal fixation instrument, the cement molding instrument has a molding portion protruding from the proximal end of the internal fixation instrument, which is inserted into the first and third through holes that communicate when the internal fixation instrument and the outer cylinder are connected and the driver is inserted into the second through hole to engage the first and second fitting portions and connect to the internal fixation instrument; and the tip of the cement separating instrument is inserted into a hole formed by the molding portion of the cement molding instrument in the bone cement mass injected into the vertebral body by the cement filling instrument.

11. A treatment instrument according to claim 10, wherein the molding portion of the cement molding instrument is cylindrical, or a cylindrical tapered type whose diameter decreases toward the tip, or a conical or hemispherical type, and the tip portion of the cement separating instrument has a tapping screw thread that fits into the hole formed and shaped by the molding portion of the cement molding instrument.

12. A medical device according to claim 11, wherein the internal fixation device has a spiral groove or ridge on the outer periphery of the first shaft.

13. The treatment instrument according to claim 10, wherein the tip of the cement separation instrument has a spherical portion at the tip.

14. A treatment instrument according to claim 1, wherein the internal fixation device has a blunt tip and a tapered portion that tapers toward the proximal side of the shaft.

15. A treatment device according to claim 14, wherein the inclined portion includes first and second inclined portions whose inclination angles increase sequentially toward the proximal side of the shaft.

16. A treatment device according to claim 14 or 15, wherein the inclined portion has a spiral screw groove or thread on its outer periphery.

17. A treatment device according to claim 14 or 15, wherein the inclined portion has a recess or a protrusion on the outer periphery.

Images