Bone fixation device

Abstract

To reliably prevent backward deviation of a bone fixator after surgery, without causing the complication and upsizing of an internal mechanism.SOLUTION: In a bone fixation device 10, an engagement member 16B, which comprises an engagement part 16Bs engaged to hold a bone fixator 23, is arranged to be movable in a direction along an axis line 11x in the movement range of reaching a transverse hole 13 through a shaft hole 16Aa of an engagement member 16A after getting out to a tip side from a position on a base end side with respect to the engagement member 16A within a shaft hole 18a of a drive member 18. The engagement part 16Bs is constituted to be movable between non-holding arrangement in which the engagement part does not hold the bone fixator 23 and holding arrangement in which the engagement part is engaged with the bone fixator 23 so as to hold it.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a bone fixation device used for fixing bones.

Background Art

[0002] Conventionally, various bone fixation devices used for fixing bones have been known. As such a bone fixation device, a bone fixator having a bone engagement portion that engages with a bone, such as a screw, a nail, or a pin, may be used alone. However, many devices are used that include such a bone fixator and an implant body configured to insert the bone fixator and disposed at a predetermined position with respect to the bone. For example, taking a bone fixation device used for treating a fracture in the proximal part of the femur as an example, an intramedullary nail body corresponding to the implant body is inserted into the medullary cavity of the femur, and a lag screw (screw) corresponding to the bone fixator is inserted into a transverse hole provided in the intramedullary nail body, so that a bone fixation device used for fixing a fracture site in the proximal part of the femur is known (see, for example, Patent Documents 1 and 2 below).

[0003] In the above bone fixation device, a bone fixator such as a lag screw is inserted into a transverse hole of an intramedullary nail body disposed in the medullary cavity of the femur and screwed toward the head of the femur, so that the tip of the bone fixator is engaged on the side of the head of the bone rather than the fracture site in the proximal part, and at the same time, the tip of an engagement member disposed in the axial hole of the intramedullary nail body by screw connection or the like is engaged with the outer peripheral surface of the bone fixator, whereby the bone fixator can be held in a predetermined manner with respect to the intramedullary nail body. In this case, it may be required to provide a plurality of transverse holes in the intramedullary nail body and hold a plurality of bone fixators inserted through these transverse holes. For example, in a fracture of the proximal part of the femur, in order to prevent the femoral head from rotating with respect to the shaft of the femur, it is necessary to introduce a plurality of bone fixators from the outside (lateral side) of the shaft of the femur through the intramedullary nail body to the femoral head.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Patent No. 6058958 [Patent Document 2] Patent No. 6510297 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Incidentally, in the bone fixation device described above, as described in Patent Documents 1 and 2, in order to hold the multiple bone fixation devices inserted through the multiple transverse holes provided in the intramedullary nail body, multiple engaging members are built into the outer circumference of each bone fixation device, and means for positioning each of these engaging members are required. However, because the diameter of the intramedullary nail body inserted into the medullary cavity is small, it is difficult to build in multiple engaging members and to provide means for positioning each of these engaging members in a way that ensures reliable operation without complicating or increasing the size of the device. As a result, some of the bone fixation devices cannot be held or fixed at all, or sufficient holding force cannot be provided to some of the bone fixation devices, leading to problems such as the bone fixation devices falling out of the femoral head (posterior displacement or backout) after surgery.

[0006] Specifically, it is required that multiple bone fixation devices be held in the same or different engagement modes, but it is difficult to provide an engagement mode suitable for each bone fixation device due to structural and dimensional constraints. In fact, due to reasons such as insufficient axial length or operating stroke of any of the engaging members built into the intramedullary nail body, or deterioration of the operating balance due to misalignment of the axial axis of the engaging part of the engaging member, the reliability of holding the bone fixation device corresponding to that engaging member is impaired, and there is a tendency for it to easily dislodge backward.

[0007] Therefore, the present invention solves the above problems, and its objective is to reliably prevent posterior displacement (backout) of the bone fixation device after surgery without complicating or increasing the size of the internal mechanism. [Means for solving the problem]

[0008] The bone fixation device of the present invention comprises a first bone fixation device and a second bone fixation device, respectively, which are introduced into the bone; an implant body disposed inside the bone, which is provided on the tip side in the direction along the axis of the implant body through which the first bone fixation device is inserted, and a second transverse hole provided on the proximal end side in the direction along the axis of the implant body through which the second bone fixation device is inserted; a first engaging member configured to be movable in the direction along the axis of the implant body and which holds the first bone fixation device inserted through the first transverse hole to the implant body; a first driving member that engages the first engaging member with the first bone fixation device by driving the first engaging member in the direction along the axis of the implant body; and a second engaging member configured to be movable in the direction along the axis of the implant body and which holds the second bone fixation device inserted through the second transverse hole to the implant body. Here, the first engaging member and the first driving member each have an axial hole, and the second engaging member is arranged to be movable in a direction along the axis within a range of movement from a position in the axial hole of the first driving member that is closer to the base end than the first engaging member, outwards towards the tip end, through the axial hole of the first engaging member, and reaching the second transverse hole, and is equipped with an engaging portion that engages to hold the second bone fixator, and the engaging portion is configured to be movable between a non-holding configuration that does not hold the second bone fixator and a holding configuration that engages with and holds the second bone fixator.

[0009] According to the present invention, the second engaging member is configured to be movable within a range of motion that extends from a position closer to the base end than the first engaging member within the shaft hole of the first driving member, through the shaft hole of the first engaging member, and reaches the second transverse hole. As a result, the ranges of motion of the first engaging member and the second engaging member in the direction along the axis overlap with each other radially, and the second engaging member has a range of motion that extends even further toward the base end than the first engaging member, and moreover, this range of motion overlaps radially with respect to the first driving member. As a result, it becomes possible to secure a large length and operating stroke (range of motion) of the second engaging member in the direction along the axis without complicating or enlarging the structure in the direction along the axis or radially in the internal mechanism. Therefore, in the non-retaining configuration, the second engaging member can be retracted from the second transverse hole or prevented from protruding significantly from the second transverse hole, making it easier to insert the second bone fixator. In the retaining configuration, engagement clearance is obtained in the direction along the axis, making it possible to reliably engage and retain the second bone fixator. Furthermore, the overlap of the radially inner and outer engaging structures suppresses uneven distribution of the retaining action.

[0010] In the present invention, it is preferable that the base end of the second engaging member in the non-retaining position is positioned on the base end side relative to the base end of the first engaging member, and that when the second engaging member moves toward the retaining position, the displacement along the axis between the base end of the second engaging member and the base end of the first engaging member is reduced. According to this, when the base end of the second engaging member in the non-retaining position is positioned on the base end side relative to the base end of the first engaging member, and the displacement is reduced when the second engaging member moves toward the retaining position, the length and operating stroke of the second engaging member can be further increased compared to when the second engaging member in the non-retaining position is at the same position as the first engaging member or further toward the tip. This makes it possible to further improve the retaining performance of the second engaging member on the second bone fixator while ensuring the compactness of the internal mechanism along the axis.

[0011] In the present invention, it is preferable that the first drive member has an operating portion formed on the base end side and configured to enable operation for driving the first engaging member, and a housing portion that opens on the tip side and can accommodate at least the base end portion of the second engaging member, forming the shaft hole of the first drive member which communicates with the shaft hole of the first engaging member. With this, the first drive member can be easily operated by accessing the operating portion from the base end side, and the range of movement of the second engaging member can be widened by housing at least the base end portion of the second engaging member in the housing portion from the tip side. In this case, it is preferable that the shaft hole of the first drive member penetrates in a direction along the axis, and that the operating portion and the housing portion are formed by the shaft hole of the first drive member.

[0012] In the present invention, it is preferable that the second engaging member is positioned by restricting its movement toward the base end by a restricting portion provided on the first driving member. By positioning the second engaging member by the restricting portion provided on the first driving member, the second engaging member is reliably positioned toward the base end of the range of movement with respect to the first driving member. Here, it is preferable that the restricting portion of the first driving member is set toward the base end than the engaging drive portion of the first driving member that engages with and drives the first engaging member. In this way, the positional relationship between the first engaging member and the second engaging member can be easily set by the shape of the first driving member. At this time, it is even more preferable to provide a second elastic member that supports the second engaging member by an elastic force toward the base end. According to this, by supporting the second engaging member with the above elastic force, the second engaging member can be reliably held in the position restricted by the restricting portion.

[0013] In the present invention, it is preferable that the first drive member comprises an engagement drive unit that drives the second engagement member by contacting the first engagement member on the outer circumference side of the second engagement member. With this, since the engagement drive unit of the first drive member contacts and drives the first engagement member on the outer circumference side of the second engagement member, it becomes possible to reliably drive the first engagement member by the first drive member without increasing the radial dimensions. In particular, when the implant body is an intramedullary nail body, insertion into the medullary cavity may be performed along a guide pin that has been introduced in advance, so the second engagement member is arranged on the outer circumference of the axial hole into which the guide pin is introduced, and furthermore, there is only the contact point between the engagement drive unit of the first drive member and the first engagement member on the outer circumference side thereof, so a radial double structure is sufficient, which makes it easier to reduce the radial thickness around the axis, and thus it becomes possible to reliably hold the second bone fixation device without increasing complexity or size. Here, it is desirable that the contact range between the engagement drive unit and the first engagement member be configured in an annular shape. This increases the contact area between the first drive member and the first engaging member, enabling more reliable driving. In this case, for example, the engaging drive portion of the first drive member is configured in a cylindrical or annular shape, and the contact point of the first engaging member with the engaging drive portion is also configured in a cylindrical or annular shape.

[0014] In the present invention, it is preferable that the first drive member is rotatably arranged inside the implant body and configured to be able to drive the first engaging member toward the tip when subjected to rotational operation. With this configuration, since the first drive member is built into the implant body, the first drive member can be easily operated by inserting an operating tool into the implant body. For example, when a target device is used that is connected to the proximal end of the implant body, it is sufficient that the target device has a structure that allows a rotational operating tool for rotating the first drive member to be inserted into the implant body, so that the first drive member can be easily operated with the target device connected to the implant body.

[0015] In this case, it is preferable that the first drive member is configured to be movable in a direction along the axis by receiving the rotation operation, and when it moves toward the tip side, it presses the first engaging member against the bone fixator. Here, it is preferable that the first drive member is screwed inside the implant body and moves in a direction along the axis in accordance with the change in screwing depth. This allows the first engaging member to be driven by the movement of the first drive member itself, thus simplifying the internal mechanism. In this case, it is preferable that the implant body has a retaining member that holds the first drive member, and that the movement of the first drive member toward the proximal end is restricted by the retaining member. In this case, it is further preferable that the first drive member is configured to be movable in a direction along the axis by screwing it into the retaining member.

[0016] In the present invention, it is preferable that the first engaging member is configured to be movable in a direction along the axis between a separation configuration in which it is separated from the first bone fixator and an engagement configuration in which it engages with the first bone fixator. Furthermore, the first engaging member is restricted from rotating about the axis. Moreover, it is preferable that the first engaging member has an insertion space (insertion hole) between the tip portion that engages with the first bone fixator and the base portion that engages with the first drive member, through which the second bone fixator introduced into the second transverse hole can be inserted. It is also preferable that the first engaging member is provided with a first elastic member that supports the first engaging member with an elastic force directed toward the base end. Here, it is preferable that the movement of the first engaging member toward the base end is restricted by a restricting portion provided on the implant body. It is preferable that the restricting portion is composed of a holding member that holds the first engaging member inside the implant body.

[0017] In the present invention, it is preferable to further provide a second drive member that drives the second engaging member to engage the second engaging member with the second bone fixation device. Here, it is preferable that the second drive member is attached to the proximal end of the implant body to drive the second engaging member. In this case, the second drive member can be an end cap that is attached to the proximal end of the implant body (closing the proximal opening). In these cases, it is even more preferable that the second drive member drives the second engaging member through the axial hole of the first drive member.

[0018] In the present invention, it is preferable that the implant body has a proximal opening and an operating hole along the axis that intersects and communicates with the first transverse hole and the second transverse hole, and that the first engaging member and the second engaging member are arranged to be movable in the direction along the axis inside the operating hole and are configured to be positionable in the direction along the axis.

[0019] In the present invention, it is preferable that the first engaging member is configured to be positionable at a predetermined position by a driving action generated inside the operating hole by the first driving member. In this case, it is preferable that the implant body includes a fixing member as the second driving member that directly or indirectly fixes the second engaging member inside the operating hole. This fixing member can be configured, for example, as an end cap that seals a proximal opening provided on the proximal end side of the operating hole of the implant body.

[0020] In the present invention, it is preferable that the first drive member is disposed inside the operation hole, engages with the first engagement member, and is configured to be able to drive the first engagement member in a direction along the axis. In this case, it is desirable to further include a holding member that holds the first drive member from the proximal end side inside the operation hole and has an opening that allows access to the first drive member from the side of the end opening. The holding member can be configured to hold the first engagement member from the proximal end side in addition to or instead of the function of the holding member with respect to the first drive member described above.

[0021] In the present invention, it is preferable that the second drive member is configured to engage with the second engagement member by being attached to the operation hole and be able to drive the second engagement member in a direction along the axis. In this case, the first drive member disposed inside the operation hole is provided with an axial hole that penetrates in the direction along the axis, and it is desirable that the second drive member drives the second engagement member through the axial hole of the first drive member. When a holding member for holding the first drive member and / or the first engagement member is provided, an opening that penetrates in the direction along the axis is provided in the holding member, and the second drive member drives the second engagement member through the opening.

Advantages of the Invention

[0022] According to the present invention, there is a remarkable effect that it is possible to reliably prevent the backing out of the bone fixture after surgery without causing complication or enlargement of the internal mechanism.

Brief Description of the Drawings

[0023] [Figure 1] It is a front view (a) and a side view (b) showing an implant body of the bone fixation device according to the first embodiment. [Figure 2]Side view and end views (a), longitudinal and cross-sectional views (b), enlarged cross-sectional view (c) of the bone fixture 15 of the same embodiment, and side view (d) of the bone fixture 23. [Figure 3] Partial longitudinal sectional view (a) showing the internal structure of the main part of the same embodiment, and B-B cross-sectional view (b). [Figure 4] Longitudinal sectional view (a) showing the main structural part when the bone fixture 23 (extra screw) is in the off state in the slide-free state with respect to the bone fixture 15 (lag screw), longitudinal sectional view (b) showing the main structural part when the bone fixture 23 is in the locked S state, and explanatory view (c) showing the positional relationship with the engaging member 16B along the axis of the bone fixture 23. [Figure 5] Longitudinal sectional view (a) showing the main structural part when the extra screw is in the off state in the slide-locked state with respect to the bone fixture 15 (lag screw), longitudinal sectional view (b) showing the main structural part when the bone fixture 23 (extra screw) is in the locked L state, and explanatory view (c) showing the positional relationship with the engaging member 16B along the axis of the bone fixture 23. [Figure 6] Explanatory view (a) showing the engagement holding state when the bone fixture 15 is in the off state and the bone fixture 23 is in the off state, explanatory view (b) showing the engagement holding state when the bone fixture 15 is in the slide-free state and the bone fixture 23 is in the off state, and explanatory view (c) showing the engagement holding state when the bone fixture 15 is in the slide-locked state and the bone fixture 23 is in the off state. [Figure 7] Explanatory view (a) showing the engagement holding state when the bone fixture 15 is in the off state and the bone fixture 23 is in the off state, explanatory view (b) showing the engagement holding state when the bone fixture 15 is in the slide-free state and the bone fixture 23 is in the locked L state, and explanatory view (c) showing the engagement holding state when the bone fixture 15 is in the slide-locked state and the bone fixture 23 is in the locked S state. [Figure 8] Longitudinal sectional view showing the assembled structure of the engaging members 16A, 16B, the driving member 18, and the holding member 19 in an enlarged manner. [Figure 9]These are enlarged longitudinal section views (a) of end cap 21A and (b) of end cap 21B. [Modes for carrying out the invention]

[0024] Next, embodiments of the present invention will be described in detail with reference to the attached drawings. First, the schematic configuration of an embodiment of the bone fixation device according to the present invention will be described with reference to Figures 1 to 3.

[0025] Figure 1 shows a front view (a) and a side view (b) of the implant body 11 of the intramedullary fixation device, which is the bone fixation device of this embodiment. In the illustrated example, this implant body 11 is an intramedullary nail used when inserted into the medullary cavity of a long bone. In the implant body 11, the front view refers to the side that faces the front of the patient when attached to the patient, and the side view refers to the side that faces the patient. The implant body 11 has a shape that extends along an axis 11x. The implant body 11 is used in a position where this axis 11x is inserted into the medullary cavity of the bone. The implant body 11 has a proximal region 11A and an distal region 11B, and the axis 11x is slightly bent between the proximal region 11A and the distal region 11B.

[0026] Transverse holes 12 and 13 are formed in the proximal region 11A, and transverse holes 14A and 14B are formed in the distal region 11B. In addition, an axial hole 11a corresponding to the above-mentioned operating hole is formed in the proximal region 11A along the axis 11x from the proximal opening 11b. This axial hole 11a intersects with and communicates with the transverse holes 12 and 13. In this embodiment, the axial hole 11a is also formed continuously in the distal region 11B and is a through hole that also has a distal opening. A keyway 11c is provided in the proximal opening 11b of the axial hole 11a. The keyway 11c engages with the keyed end of an insertion device (not shown) used when introducing the implant body 11 into the bone, and allows the implant body 11 and the insertion device to be connected only in a predetermined positional relationship.

[0027] In this embodiment, the transverse holes 12 and 13 are provided with axes 12x and 13x that intersect obliquely with axis 11x. Here, transverse hole 12 corresponds to a first transverse hole provided on the tip side, and transverse hole 13 corresponds to a second transverse hole provided on the base side. In the illustrated example, axes 12x and 13x are parallel to each other. Furthermore, the transverse holes 14A and 14B are provided with axes 14ax, 14bx, and 14by that are perpendicular to axis 11x. Transverse holes 14A and 14B are holes for inserting cortical screws (cortical threads) for lateral fastening (not shown).

[0028] The bone fixation device 10 of this embodiment is used with the bone fixation device 15 shown in Figures 2(a) and (b) inserted through the transverse hole 12 of the implant body 11 shown in Figure 1. The bone fixation device 15 has a shape that extends from the tip to the proximal end along the axis 15x. The bone fixation device 15 is provided with a through-hole 15a that allows a guide pin or other guide to be inserted. The bone fixation device 15 also includes a bone engagement portion 15s at its tip that engages with bone. In the illustrated example, the bone fixation device 15 is a lag screw, and the bone engagement portion 15s is composed of a tapping screw that is screwed into the bone. Generally, the bone fixation device 15 is not limited to bone screws such as lag screws, but can also be composed of nails driven into the bone, hooks that bite into the bone, pins that are press-fitted into the bone, etc. Therefore, the bone engagement portion 15s described above may also be composed of a blade-shaped portion, an expanding portion formed to expand within the bone by manipulation, a hook portion that protrudes into the bone by manipulation, a pointed end with a sharp shape that bites into the bone, or simply the tip of a pin.

[0029] Furthermore, the bone fixation device 15 includes a connecting portion 15b to which a tool (not shown) engages at its proximal end and to which an instrument is connected. In the illustrated example, this connecting portion 15b comprises a tool engagement structure 15g that engages with a tool such as a wrench, and an instrument connecting structure 15h consisting of a screw structure (female thread) or the like that is connected to the tip of various instruments used when inserting or tractioning the bone fixation device 15 during surgery. Preferably, the connecting portion 15b has a function to define the orientation around the axis when connecting to a tool or instrument. In the illustrated example, the tool engagement structure 15g is composed of a hexagonal socket with a keyway 15k, and by engaging a tool, such as a hexagonal wrench with a key (not shown), with this socket in a rotational position in which the key fits into the keyway, the relative orientation of the tool around the axis with respect to the bone fixation device 15 is defined.

[0030] When a tool or instrument is connected to the tool engagement structure 15g described above, the angle of the handle portion of the tool or instrument (for example, the T-handle portion of a wrench) directly reflects the angle of the bone fixation device 15, making it possible to confirm the angle of the bone fixation device 15 outside the body. For example, when a surgeon passes the tool through a reference instrument such as a sleeve, which has a predetermined angle relationship with the implant body 11, and then introduces the bone fixation device 15 connected to the tip of the tool into the bone, the surgeon can determine the angle of the bone fixation device 15 at hand by the angle of the tool relative to the reference instrument.

[0031] The bone fixation device 15 includes a shaft-shaped axial portion between the tip and base portions. Engaging portions 15c and 15d are formed on the outer surface of this axial portion. In the illustrated example, the engaging portions 15c and 15d are recessed grooves, each having a shape that extends in the direction along the axis 15x. In the illustrated example, the engaging portion 15c has a relatively shallow groove shape, while the engaging portion 15d has a relatively deep groove shape. The dashed line inside the engaging portion 15d in Figure 2(c) indicates the position and shape of the contour of the inner bottom surface of the engaging portion 15c to show the difference in groove depth. The inner bottom surfaces of the engaging portions 15c and 15d have an arc-shaped contour when viewed in the width direction. In the illustrated example, two engaging portions 15c and 15d are each formed, arranged alternately at 90-degree intervals around the axis 15x. In the illustrated example, the engaging portions 15c and 15d are configured such that their formation ranges in the direction along the axis 15x are common and identical (completely coincidental).

[0032] Figure 2(d) shows a bone fixation device 23, which corresponds to a second bone fixation device inserted through the transverse hole 13. This bone fixation device 23 has a shaft hole 23a that penetrates along the axis 23x and has a bone engagement portion 23s at its tip. A shaft portion 23b extends from the bone engagement portion 23s, and a head portion 23c is located at the base end of this shaft portion 23b. The head portion 23c has a shape that is larger than the shaft portion 23b. This bone fixation device 23 corresponds to a screw, pin, rod, etc., for preventing rotation of the epiphysis (e.g., femoral head) held in the diaphysis by the bone fixation device 15. For this reason, the bone fixation device 23 is generally formed to be thinner and slightly shorter than the bone fixation device 15, as shown in the figure. This is to ensure that the bone fixation device 15 is introduced near the center of the femoral neck, while allowing the bone fixation device 23 for preventing rotation of the femoral head to pass through the femoral neck without obstruction, and to reduce the possibility of fracture due to a decrease in the rigidity of the implant body 11 caused by an increase in the outer diameter of the shaft portion 23b of the bone fixation device 23. As described above, the bone fixation device 23 is formed to be slender, so the outer surface of the shaft portion 23b is usually made smooth. For this reason, sufficient holding force and a stable engagement state are necessary to engage with the smooth shaft portion 23b and hold the bone fixation device 23, and therefore the holding function of the engagement member 16B is extremely important.

[0033] As shown in Figure 3(a), an engaging member 16A (first engaging member) is housed within the axial hole 11a of the implant body 11, and is equipped with an engaging portion 16s that engages with the bone fixation device 15. A more detailed structure of the engaging member 16A is shown in Figure 8. The engaging member 16A has an axial hole 16Aa that penetrates along the axis 11x of the implant body 11. The proximal end 16Ab of the engaging member 16A is formed in a flange shape that protrudes outward. The proximal end 16Ab is supported from the tip side by an elastic member 17A (first elastic member), which consists of a coil spring or the like and is housed between the proximal end 16Ab and an inner surface step formed within the axial hole 11a of the implant body 11, and is biased toward the proximal end of the implant body 11. The engaging member 16A is arranged to be movable along the axis 11x inside the axial hole 11a. In this configuration, the engaging member 16A, in the initial position shown in Figure 3 (the separated arrangement described above), is prevented from protruding into the transverse hole 12 by the elastic member 17A. In practice, as shown in the illustrated example, the engaging portion 16As is positioned slightly retracted from the transverse hole 12 into the shaft hole 11a. Therefore, the bone fixation device 15 can be easily inserted into the transverse hole 12 without interference from the engaging portion 16As. In this separated arrangement, the engaging member 16A is restricted from the base end by the tip portion 19c of the retaining member 19, which will be described later.

[0034] Furthermore, as shown in Figure 3(b), the engaging member 16A includes a rotation-restricting portion 16Ae, which is composed of a hexagonal prism-shaped cross-section. This rotation-restricting portion 16Ae fits into a hexagonal hole-shaped rotation-restricting portion 11e, which is formed on a part of the inner surface of the shaft hole 11a in the direction of the axis 11x. The inner surface shape of the shaft hole 11a, other than the rotation-restricting portion 11e, is configured, for example, to be an inscribed circle with a hexagonal cross-section, so as to accommodate the rotation-restricting portion 16Ae. As a result, although the engaging member 16A is movable along the axis 11x, it is restricted from rotating around the axis 11x by the rotation-restricting portion 11e, and its angular orientation is kept constant. The configuration for restricting the rotation of the engaging member 16A around the axis 11x is not limited to the above structure; a structure using a restricting pin may also be used, as long as the rotation of the engaging member 16A around the axis is prevented by some kind of restricting portion. Furthermore, please also refer to Figure 8, which is an enlarged view of a portion of Figure 3(a), for details of the engaging member 16A, the engaging member 16B, the elastic members 17A and 17B, the driving member 18, and the holding member 19 described below.

[0035] The engaging portion 16As is provided on both sides of the axial hole 16Aa along the axis 12x of the transverse hole 12 at the tip (lower end in the figure) of the engaging member 16A. The tip of the engaging portion 16As has an arc-shaped contour along a plane perpendicular to the axis 12x (in the width direction). This arc-shaped contour of the tip of the engaging portion 16As matches the arc-shaped contour of the inner bottom surface of the engaging portion 15c of the bone fixation device 15 along a plane perpendicular to the axis 15x. This is also shown by a dashed line in Figure 2(c) which depicts the bone fixation device 15. As a result, when the engaging portion 16As is fitted to the inner bottom surface of the side engaging portion 15c, the contact area between the two can be increased. This increases the resistance to sliding motion of the bone fixation device 15 in the direction along the axis 15x, thereby increasing the restraining force against sliding motion in the slide-locked state, and thus ensuring a secure lock.

[0036] As described above, a bone fixation device 23 (see Figure 2(d)) such as a screw, pin, or nail, different from the bone fixation device 15, can be inserted into the transverse hole 13 of this embodiment. The engaging member 16A has an insertion hole 16Ac formed therein to allow the bone fixation device 23 to be inserted into the transverse hole 13. This insertion hole 16Ac is formed in a shape that extends in the direction along the axis 11x (e.g., oval or elliptical in the illustrated example) so as to allow the insertion of at least the bone fixation device 23 to be inserted into the transverse hole 13 within the operating range Ld of the engaging member 16A in the direction along the axis 11x. Here, the operating range Ld is, for example, the range from a position in which the engaging portion 16As does not protrude into the transverse hole 12 (for example, a slightly recessed position as shown in Figure 3(a), corresponding to the separation arrangement described above) to the position in which it protrudes the most into the transverse hole 12 when the slide-free state shown in Figure 4 is achieved (corresponding to the engagement arrangement described above). In the illustrated example, for the engaging member 16A, the base end portion 16Ab contacts the tip portion 19c of the holding member 19, setting the base end limit position of the operating range Ld. Furthermore, the tip end limit position of the illustrated operating range Ld is set based on the relationship between the range along the axis 11x of the irregularly shaped (hexagonal) cross-section of the engaging member 16A (the range formed along the axis 11x of the rotation-restricting portion 16Ae) and the range along the axis 11x of the irregularly shaped (hexagonal) cross-section of the inner surface of the axial hole 11a of the implant body 11 (the range formed along the axis 11x of the rotation-restricting portion 11e). This is the limit position of movement set by restriction caused by the cylindrical portion of the engaging member 16A adjacent to the rotation-restricting portion 16Ae reaching into the rotation-restricting portion 11e of the axial hole 11a. However, unlike the illustrated example, the operating range Ld may be restricted by other restricting structures such as stepped portions. The operating range Ld in the illustrated example is 1.9 mm.

[0037] The base end portion 16Ab of the engaging member 16A is contacted by the engaging drive portion 18h of the driving member 18 from the base end side (upper in the figure) of the axis 11x, and the elastic member 17A biases it from the tip side (lower in the figure) by elastic force. As a result, the engaging member 16A is held in a state where it is sandwiched between the elastic member 17A and the driving member 18. The driving member 18 has an axial hole 18a that penetrates along the axis, and the opening edge of this axial hole 18a is the base end portion 18b. A tool engaging portion 18c, such as a hexagonal socket, is formed on the inner surface of the base end side of the axial hole 18a, which is inside the base end portion 18b. The driving member 18 has a male screw 18d on its outer circumference, which screws into a female screw 19e formed on the inner surface of the opening 19a of the holding member 19. Therefore, when the drive member 18 is rotated by operating the tool engagement portion 18c with a tool (not shown), the drive member 18 moves in the direction of the axis 11x. The male screw 19d provided on the outer circumference of the retaining member 19 is screwed into the female screw 11d formed on the inner surface of the shaft hole 11a, and is further restricted from moving toward the tip side of the axis 11x by abutting against the inner surface step of the shaft hole 11a, thereby holding the retaining member 19 in a position along the axis 11x. In the illustrated example, the inner surface of the opening 19a of the retaining member 19 has a smaller diameter at the base end so that the drive member 18 cannot move toward the base end (upward in the illustration) beyond the position shown in Figure 3(a). Specifically, the drive member 18 is screwed into the female screw 19e provided on the tip side, but is configured so that it cannot move toward the tool engagement portion 19b which has a more limited cross-section. In other words, the retaining member 19 has the function of holding the drive member 18 by restricting it from the base end side.

[0038] The drive member 18 has a housing portion 18e at the tip end of the shaft hole 18a. This housing portion 18e opens towards the tip end and communicates with the shaft hole 16Aa of the engaging member 16A. Inside the housing portion 18e of the drive member 18 and the shaft hole 16Aa of the engaging member 16A, an engaging member 16B, which corresponds to a second engaging member, is arranged. The engaging member 16B has a shaft hole 16Ba that penetrates in the axial direction, engaging portions 16Bs provided at the tip end, and a base end portion 16Bb provided at the base end. Furthermore, the portion of the engaging member 16B that is at the tip end, excluding a part of the base end end, has a spiral slit, making it an elastic portion 16Bc that can expand and contract in the direction along the axis 11x. As a result, the engaging member 16B moves toward the tip, and when its engaging portion 16Bs comes into contact with the shaft portion 23b of the second bone fixation device, the bone fixation device 23, the bone fixation device 23 is held in place by a holding force corresponding to the amount of elastic deformation of the elastic portion 16Bc. The engaging member 16B is positioned inside the engaging member 16A so as to be movable in a direction along the axis 11x, with its angular orientation around the axis 11x restricted by the engaging member 16A via the regulating pin 22, that is, without rotation around the axis 11x.

[0039] The housing portion 18e of the shaft hole 18a and the shaft hole 16Aa have substantially the same size (inner diameter or internal dimension) and constitute a continuous guide passage for the engaging member 16B. In the illustrated example, this guide passage is columnar (preferably cylindrical). Specifically, the engaging member 16B is configured to be movable in a direction along the axis 11x, with a range of movement from the inside of the shaft hole 18a of the drive member 18, outward towards the tip, through the inside of the shaft hole 16Aa of the engaging member 16A, to the transverse hole 13. In the illustrated example, the engaging member 16B has an outer circumferential surface with a radius dimension substantially corresponding to the inner circumferential surface of the housing portion 18e and the shaft hole 16Aa, so that it is guided in the direction along the axis 11x by the housing portion 18e and the shaft hole 16Aa. Therefore, the engaging member 16B is guided in the direction along the axis 11x within the guide passage. The above-described guide passage limits the movement range of the engaging member 16B from a position closer to the base end than the engaging member 16A to a position where it reaches the transverse hole 13. Here, the position where the engaging member 16B is closer to the base end than the engaging member 16A is the position where the engaging member 16B is positioned within the housing portion 18e, where the base end 16Bb can be positioned closer to the base end than the tip 19c, because the base end 16Ab of the engaging member 16A is restricted to the base end side by contacting the tip 19c of the holding member 19. Furthermore, the engaging member 16B is supported by an elastic member 17B positioned between it and the engaging member 16A, biasing it toward the base end side in the direction along the axis 11x relative to the engaging member 16A. In this specification, the term "axial hole" is used to mean a through hole along the axial direction, but any axial hole may be formed as a so-called axial hole that does not penetrate along the axial direction. Also, in this specification, the term "axial hole" is used to include both through holes and non-through holes.

[0040] In the state shown in Figure 3(a), the drive member 18 is positioned at the most proximal end, and the engaging member 16A is also in isolation, unable to move further toward the proximal end by contacting the tip portion 19c of the holding member 19. At this time, the engaging drive portion 18h of the drive member 18 is located in a position approximately corresponding to the tip portion 19c, and therefore does not affect the position of the proximal end portion 16Ab of the engaging member 16A. Furthermore, the proximal end portion 16Bb of the engaging member 16B is located within the housing portion 18e of the drive member 18. More specifically, the engaging member 16B has a restricting portion 18g where the opening edge of the opening 18f on the proximal end side of the housing portion 18e of the drive member 18 contacts the proximal end portion 16Bb, and further movement toward the proximal end is restricted by this opening edge. In this case, the base end portion 16Bb of the engaging member 16B is positioned on the base end side of the base end portion 16Ab of the engaging member 16A by a base end difference Le, which is the distance in the direction along the axis 11x between the opening 18f of the driving member 18 and the engaging driving portion 18h.

[0041] The opening 18f of the drive member 18 is exposed on the proximal end side within the opening 19a of the retaining member 19, so that the tool engagement portion 18c of the drive member 18, which is exposed within the opening 19a of the retaining member 19, can be accessed from the outside. That is, the surgeon can engage a tool (not shown, e.g., a hex wrench) with the tool engagement portion 18c of the drive member 18 through the opening 19a and rotate the drive member 18. In addition, a tool engagement portion 19b, such as a hexagonal hole, is formed on the inner surface of the opening 19a of the retaining member 19 in order to screw the retaining member 19 into the female thread 11d of the implant body 11 and attach it to a predetermined position. Furthermore, the inner edge of the proximal end portion 16Bb of the engagement member 16B (the opening edge of the shaft hole 16Ba) is positioned on the inner circumference side of the opening 18f of the drive member 18. As a result, the stepped portions 21Af and 21Bf provided on the tip portions 21Aa and 21Ba of the end caps 21A and 21B, which will be described later, can engage with the inner edge of the base end portion 16Bb of the engaging member 16B from the base end side through the shaft hole 18a (opening 18f).

[0042] When the surgeon rotates the drive member 18 via the tool engagement portion 18c using a tool (not shown), the drive member 18 moves in a direction along the axis 11x due to the change in the screwing depth of the male screw 18d and the female screw 19e. When the drive member 18 moves toward the tip from the state shown in Figure 3(a), the engagement drive portion 18h also moves the engagement member 16A toward the tip. However, as described above, the rotation of the engagement member 16A is restricted, so although the drive member 18 rotates, the engagement member 16 does not rotate but moves downward along the axis 11x inside the shaft hole 11a. This movement of the engagement member 16A allows the engagement portion 16As to protrude into the transverse hole 12, and the amount of protrusion can also be changed. As the drive member 18 moves toward the tip, the engaging member 16B also moves toward the tip with its base end 16Bb in contact with the restricting portion 18g (the opening edge of the opening 18f). However, due to the distance along the axis 11x between the restricting position by the restricting portion 18g and the contact position by the engaging drive member 18h, the base end 16Bb is maintained in a position positioned toward the base end by the base end difference Le relative to the base end 16Ab of the engaging member 16A.

[0043] In this embodiment, when the engaging portion 15d of the bone fixation device 15 is positioned opposite the engaging portion 16As of the engaging member 16A, the surgeon can move the engaging member 16A downward to the limit of movement position at the tip of the operating range Ld by rotating the drive member 18. At this time, the tip of the engaging portion 16As is located on the free line FL shown in Figure 4 within the groove of the engaging portion 15d. However, due to the setting of the limit of movement position, the tip of the engaging portion 16As does not contact the inner bottom surface of the groove of the engaging portion 15d. Therefore, although the rotation of the bone fixation device 15 is restricted around the axis 15x, it is in a slide-free state that allows it to move along the axis 15x relative to the implant body 11. Here, when the engaging member 16A reaches the limit of movement position of the operating range Ld, an axial force in the direction along the axis 11x is applied to the screw structure between the male screw 18d of the drive member 18 and the female screw 19e of the retaining member 19. This axial force suppresses loosening of the threaded structure between the drive member 18 and the retaining member 19.

[0044] On the other hand, when the engaging portion 15c is positioned opposite the engaging portion 16As, if the surgeon moves the engaging member 16A downward in the figure by the above operation, the tip of the engaging portion 16As abuts against the inner bottom surface of the groove of the engaging portion 15c before it abuts against the limit position of the movement range Ld. At this time, the tip of the engaging portion 16As is located on the lock line LL shown in Figure 5. As a result, the bone fixation device 15 is put into a slide-lock state in which not only rotation around the axis 15x is restricted, but movement in the direction along the axis 15x is also restricted. Here, when the engaging portion 16As abuts against the inner bottom surface of the engaging portion 15c, an axial force in the direction along the axis 11x is applied to the screw structure between the drive member 18 and the retaining member 19 via the engaging member 16A. This axial force suppresses loosening of the screw structure between the drive member 18 and the retaining member 19.

[0045] In the illustrated example of the bone fixation device 15, the engaging portions 15c and 15d of the bone fixation device 15 are formed as grooves, with the bone engaging portion 15d being deeper than the bone fixation device side engaging portion 15c. As a result, the engaging portion 16As of the engaging member 16A, which is positioned at a specific position along the axis 11x on the implant body 11 (corresponding to the above-mentioned engaging arrangement), engages with the engaging portion 15d, thereby allowing the bone fixation device 15 to slide freely relative to the implant body 11. Furthermore, the engaging portion 16As of the engaging member 16A, which is positioned at a specific position along the axis 11x on the implant body 11 (corresponding to the above-mentioned engaging arrangement), engages with the engaging portion 15c, thereby locking the bone fixation device 15 relative to the implant body 11.

[0046] In this embodiment, since the engaging member 16A is always biased toward the base end by the elastic member 17A, even if the position of the driving member 18 along the axis 11x is moved toward the base end, the restricting position of the engaging member 16A toward the base end is determined by its contact with the tip portion 19c of the retaining member 19, and is therefore the position shown in Figure 3(a). At this time, the base end portion 18b of the driving member 18 is also restricted toward the base end by the retaining member 19 as described above, so its restricting position toward the base end is the position shown in Figure 3(a). As a result, the restricting position toward the base end of the engaging member 16B, which is biased toward the base end by the elastic member 17B, is determined by the restricting portion 18g at the innermost part of the housing portion 18e when the driving member 18 is in the restricted position toward the base end. Therefore, the restricting position of the engaging member 16A can be set to a separated position in which the engaging portion 16As does not protrude into the transverse hole 12, and the restricting position of the engaging member 16B can be set to a non-retaining position in which the engaging portions 16Bs do not protrude into the transverse hole 13. The reason why the engaging member 16B is set to a non-retaining position is that the engaging member 16B has an elastic portion 16Bc which allows it to expand and contract in the direction along the axis 11x. Therefore, even if the engaging portions 16Bs protrude slightly into the transverse hole 13, the bone fixation device 23 can be inserted into the transverse hole 13 without any problems. However, in such a case, the bone fixation device 23 cannot substantially perform its retaining function, so the term "non-retaining position" is used instead of "separated position". However, it is also desirable that, in the off state shown in Figures 3(a) and 8, the engaging member 16B is positioned so that the engaging portions 16Bs do not protrude into the transverse hole 13 and are recessed towards the base end so as not to come into contact with (interfere with) the bone fixation device 23.

[0047] Figure 4(a) shows the case where the tool engagement portion 18c of the drive member 18 is operated to make the bone fixation device 15 slide-free by the engagement member 16A, and the engagement member 16B is in the proximal end restricting position (non-retaining position). At this time, the drive member 18 moves from the proximal end restricting position toward the tip, and as a result, the engagement portion 16As of the engagement member 16A in the engaged position is set to the free line FL that enables the slide-free state within the groove of the engagement portion 15d of the bone fixation device 15. Also, since the engagement member 16B is positioned in a position restricted by the restricting portion 18g of the drive member 18 which has moved slightly toward the tip, the proximal end portion 16Bb of the engagement member 16B is positioned proximal by a proximal difference Le than the proximal end portion 16Ab of the engagement member 16A. In this case, as shown in Figure 4(c), the engaging portions 16Bs of the non-retaining engaging member 16B are positioned at the very edge of contact with the outer circumferential surface of the shaft portion 23b of the bone fixation device 23. While this does not hinder the insertion of the bone fixation device 23 into the transverse hole 13, it prevents the bone fixation device 23 from performing its retaining function once inserted into the transverse hole 13.

[0048] Figure 4(b) shows the state when the bone fixation device 15 becomes slide-free by the engagement member 16A when the tool engagement portion 18c of the drive member 18 is operated, the end cap 21A is introduced into the shaft hole 11a from the proximal opening 11b of the implant body 11, and the male thread 21Ac of the end cap 21A is screwed into the female thread 11d to a predetermined depth, thereby engaging the stepped portion 21Af on the tip portion 21Aa side with the proximal end portion 16Bb of the engagement member 16B through the shaft hole 18a of the drive member 18 to the opening 18f, and the engagement member 16B is pushed down (held position). At this time, the engagement portion 16As of the engagement member 16A, which has been pushed down by the drive member 18, is set to the free line FL, as described above. Here, when the engaging portion 16As of the engaging member 16A is set to the free line FL, a small gap exists between the tip portion 16As of the engaging member 16A and the inner bottom surface of the engaging portion 15c of the bone fixation device 15. On the other hand, as shown in Figure 9(a), the engaging member 16B moves toward the tip by being pushed down by the stepped portion 21Af located on the tip portion 21Aa side of the end cap 21A, and is positioned in a holding position. At this time, the engaging portion 16Bs of the engaging member 16B is pressed against the outer circumferential surface of the shaft portion 23b of the bone fixation device 23, and the bone fixation device 23 is held in place by the elastic restoring force of the elastic portion 16Bc.

[0049] In this holding configuration, as shown in Figure 9(a), the relative position ΔS of the stepped portion 21Af with respect to the tip portion 19c of the holding member 19 results in a locked S (weak lock) state, and the elastic portion 16Bc is compressed more, resulting in a weaker elastic force being exerted on the bone fixator 23 than in the locked L state described later. As a result, the holding force of the bone fixator 23 by the implant body 11 is also reduced. This is because, although the bone fixator 23 itself is held by the engaging member 16B, the bone fixator 15 is in a slide-free state, so the bone fixator 23 is configured to slide accordingly. However, unlike this embodiment, only the presence or absence of holding of the bone fixator 23 is selectable, and it is also acceptable to not make a difference in holding force. In this case, the bone fixator 23 is held with a predetermined holding force by setting the engaging member 16B to the holding configuration.

[0050] As shown in Figure 9(a), the end cap 21A comprises a tip portion 21Aa that can be inserted into the shaft hole 18a of the drive member 18, a tool engagement portion 21Ab such as a hexagonal hole provided at the base end, a male thread 21Ac that screws into the female thread 11d of the shaft hole 11a of the implant body 11, and annular stepped portions 21Ad, 21Ae, and 21Af that are formed concentrically in the illustrated example. When the surgeon inserts the end cap 21A into the shaft hole 11a and screws the male thread 21Ac into the female thread 11d, the end cap 21A is positioned as the stepped portion 21Ad eventually comes into contact with the base end of the retaining member 19. At this time, by attaching the end cap 21A, the stepped portion 21Ad abuts against the base end of the retaining member 19, so that the retaining member 19 is held down from above as shown in the figure, preventing its screw portion from loosening, and the axial force generated between the retaining member 19 also provides an anti-loosening effect for the end cap 21A. As a result, the vertical positions of the engaging members 16A, 16B and the driving member 18 are also indirectly restricted, so that the bone fixation device 15 is held in place of the implant body 11. As mentioned above, there is a small gap between the engaging portion 16As of the engaging member 16A and the bone fixation device 15, so even if a load is placed on the bone fixation device 15 due to walking movements during rehabilitation after surgery, the engaging member 16A is less likely to be subjected to force, and the screw of the driving member 18 is also less likely to loosen, so the end cap 21A is in a non-contact state with the driving member 18. However, as with the end cap 21B described later, the end cap 21A may abut against the driving member 18 when attached.

[0051] Figure 5(a) shows the case where the tool engagement portion 18c of the drive member 18 is operated to position the engagement member 16A in a position where the bone fixation device 15 is in a slide-lock state, and the engagement member 16B is in a regulating position on the proximal end. At this time, the drive member 18 moves from the regulating position on the proximal end toward the tip, and as a result, the engagement portion 16As of the engagement member 16A in the engagement position is set to the locking line LL that realizes the slide-lock state of the bone fixation device 15. Also, since the engagement member 16B is positioned in a position regulated by the regulating portion 18g of the drive member 18 which has moved slightly toward the tip, the proximal end portion 16Bb of the engagement member 16B is positioned proximal by a proximal difference Le compared to the proximal end portion 16Ab of the engagement member 16A. In this case, as shown in Figure 5(c), the engaging portions 16Bs of the non-retaining engaging member 16B are positioned at the very edge of contact with the outer circumferential surface of the shaft portion 23b of the bone fixation device 23. While this does not hinder the insertion of the bone fixation device 23 into the transverse hole 13, it prevents the bone fixation device 23 from performing its retaining function once inserted into the transverse hole 13.

[0052] Figure 5(b) shows the state when the bone fixation device 15 is in a slide-lock state by the engaging member 16A when the tool engaging portion 18c of the drive member 18 is operated. The end cap 21B is introduced into the shaft hole 11a from the proximal opening 11b of the implant body 11, and the male thread 21Bc of the end cap 21B is screwed into the female thread 11d to a predetermined depth. This causes the stepped portion 21Bf on the tip portion 21Ba side to engage with the proximal end portion 16Bb of the engaging member 16B through the shaft hole 18a of the drive member 18 to the opening 18f, thereby pushing the engaging member 16B down. At this time, the engaging portion 16As of the engaging member 16A, which has been pushed down by the drive member 18, is set to the locking line LL, as described above. When the engaging portion 16As of the engaging member 16A is set to the locking line LL, the tip portion 16As of the engaging member 16A and the bone fixation device 15 are in contact. On the other hand, the engaging member 16B is moved toward the tip by being pushed down by the stepped portion 21Bf located on the tip portion 21Aa side of the end cap 21A, and is positioned in a holding position. At this time, the engaging portion 16Bs of the engaging member 16B is pressed against the outer circumferential surface of the shaft portion 23b of the bone fixation device 23, and the bone fixation device 23 is held in place by the elastic restoring force of the elastic portion 16Bc.

[0053] In this holding configuration, as shown in Figure 9(b), the relative position ΔL of the stepped portion 21Bf with respect to the tip portion 19c of the holding member 19 creates a locked L (strongly locked) state, and the elastic portion 16Bc is compressed more significantly, resulting in a stronger elastic force being exerted on the bone fixator 23 than in the aforementioned locked S state. As a result, the holding force of the bone fixator 23 by the implant body 11 also increases. This is because, although the bone fixator 23 itself is held by the engaging member 16B, the bone fixator 15 is in a slide-lock state, so the bone fixator 23 is configured to be less likely to slide in accordance with this. However, unlike this embodiment, only the presence or absence of holding of the bone fixator 23 is selectable, and it is also acceptable to not make a difference in holding force. In this case, the bone fixator 23 is held with a predetermined holding force by setting the engaging member 16B to the holding configuration.

[0054] As shown in Figure 9(b), the end cap 21B comprises a tip portion 21Ba that can be inserted into the shaft hole 18a of the drive member 18, a tool engagement portion 21Bb such as a hexagonal hole provided at the base end, a male thread 21Bc that screws into the female thread 11d of the shaft hole 11a of the implant body 11, and, in the illustrated example, annular stepped portions 21Bd, 21Be, and 21Bf that are formed concentrically. When the surgeon inserts the end cap 21B into the shaft hole 11a and screws the male thread 21Bc into the female thread 11d, the end cap 21B is positioned as the stepped portion 21Be eventually comes into contact with the base end portion 18b of the drive member 18. At this time, by attaching the end cap 21B, the stepped portion 21Be comes into contact with the base end portion 18b of the drive member 18, so that the drive member 18 is held down from above as shown in the figure, preventing the screw portion from loosening, and the axial force generated between the drive member 18 and the end cap 21B also provides an anti-loosening effect. As a result, the vertical positions of the engaging members 16A, 16B and the drive member 18 are also indirectly restricted, so the holding state of the bone fixation device 15 with respect to the implant body 11 is stabilized. As mentioned above, the tip portion 16As of the engaging member 16A and the bone fixation device 15 are in contact, so although the engaging member 16A and the drive member 18 are subjected to force due to the load on the bone fixation device 15 during walking after surgery, the drive member 18 is pressed by the end cap 21B, so the loosening of the screw of the drive member 18 is prevented.

[0055] In Figure 9, for the sake of clarity, the stepped portions 16Ad-16Af and 16Bd-16Bf are indicated by dashed lines with reference numerals, showing their positions along the axis 11x of each stepped portion. The positions of each stepped portion can be arbitrarily set to suitably achieve the positioning of the end caps 21A and 21B and the driving state of the engaging member 16B.

[0056] As a result of the above configuration, as shown in Figure 6, by operating (rotating) the tool engagement portion 18c of the drive member 18, the bone fixator 15 (lag screw) can be set to one of the following states: an off state in which it is not engaged with the engagement portion 16As of the engagement member 16A (separated arrangement) (see Figure 6(a)), a slide-free state in which rotation is restricted but sliding is possible due to the groove arrangement of the engagement portion 16As of the engagement member 16A (engaged arrangement) (see Figure 6(b)), or a slide-lock state in which both rotation and sliding are restricted due to contact with the engagement portion 16As of the engagement member 16A (engaged arrangement) (see Figure 6(c)). On the other hand, by attaching an end cap without stepped portions 21Af, 21Bf instead of the end cap 21A or 21B, the bone fixator 23 (extra screw) can be set to an off state in which it is not engaged with the engagement portion 16Bs of the engagement member 16B (non-retaining arrangement) in any of the above cases.

[0057] On the other hand, as shown in Figure 7, regardless of the state the bone fixation device 15 (lag screw) is in, attaching the end cap 21A or 21B allows it to be held in a locked L state (see Figure 7(b)) or locked S state (see Figure 7(c)) by the engaging portion 16Bs of the engaging member 16B (holding arrangement). Since both the end caps 21A and 21B are positioned by the stepped portions 21Ad and 21Be contacting the holding member 19 and the driving member 18, adjustment of the mounting position is unnecessary during installation, thus simplifying the work and improving the driving accuracy of the engaging member 16B.

[0058] The embodiment described above provides the following effects. First, the engaging member 16B (second engaging member) is configured to move within a range of motion that extends from a position closer to the base end than the engaging member 16A within the housing portion 18e of the shaft hole 18a provided in the driving member 18 (first driving member) that drives the engaging member 16A (first engaging member), through the shaft hole 16Aa provided in the engaging member 16A, and reaches the transverse hole 13 (second transverse hole). As a result, the ranges of motion of the engaging member 16A and the engaging member 16B in the direction along the axis 11x overlap radially in and out, and the engaging member 16B has a range of motion that extends even further toward the base end than the engaging member 16A, and moreover, this range of motion is configured to overlap radially in and out with respect to the driving member 18. As a result, it becomes possible to secure a large length and operating stroke (range of movement) of the engaging member 16B in the direction along the axis 11x without complicating or enlarging the internal mechanism's structure in the direction along the axis 11x or in the radial direction. Therefore, in the non-retaining configuration, it is possible to retract the engaging member 16B from the transverse hole 13 or prevent it from protruding significantly from the transverse hole 13, making it easier to insert the bone fixation device 23. In the retaining configuration, engagement clearance is obtained in the direction along the axis 11x, making it possible to reliably engage and retain the bone fixation device 23. Furthermore, the overlap of the radially inner and outer engaging structures suppresses uneven distribution of the retaining force on the bone fixation devices 15 and 23.

[0059] In this embodiment, in particular, the base end 16Bb of the engaging member 16B in the non-retaining position is positioned on the base end side relative to the base end 16Ab of the engaging member 16A. When the engaging member 16B moves toward the retaining position, the positional displacement along the axis 11x between the base end 16Bb of the engaging member 16B and the base end 16Ab of the engaging member 16A is reduced. This makes it possible to increase the length and operating stroke of the engaging member 16B without increasing the range of the internal mechanism along the axis 11x. As a result, it is possible to further improve the retaining performance of the engaging member 16B on the bone fixation device 23 while ensuring the compactness of the internal mechanism along the axis 11x.

[0060] Furthermore, the drive member 18 has a tool engagement portion 18c, which is an operating portion formed on the base end side and configured to enable operation for driving the engagement member 16A, and a housing portion 18e, which opens on the tip side and constitutes the shaft hole 18a of the drive member 18 that communicates with the shaft hole 16Aa of the engagement member 16A, and is capable of accommodating at least the base end portion of the engagement member 16B. This allows operation of the drive member 18 from the base end side while also allowing the housing of the engagement member 16B from the tip side, thereby ensuring the aforementioned effects while avoiding increased complexity and size of the structure centered on the drive member 18.

[0061] Furthermore, the shaft hole 18a of the drive member 18 penetrates in a direction along the axis 11x, and the tool engagement portion 18c and housing portion 18e, which are the operating portions, are formed by the shaft hole 18a of the drive member 18. This makes it possible to further simplify the structure of the drive member 18 while allowing access to the engagement member 16B from the outside of the base end.

[0062] Furthermore, the engaging member 16B is positioned by restricting its movement toward the proximal end by a restricting portion 18g provided on the drive member 18, which corresponds to the first drive member. This establishes a reference position for the engaging member 16B in its non-retaining configuration, thereby reliably preventing contact with the engaging portion 16Bs when inserting the bone fixation device 23 into the transverse hole 13, and also stabilizing the engagement state of the engaging portion 16Bs and ensuring a secure retention state in the retaining configuration of the engaging member 16B.

[0063] Furthermore, the drive member 18 has an engagement drive unit 18h that engages with and drives the engaging member 16A, and the restricting unit 18g of the drive member 18 is set on the base end side of the engagement drive unit 18h. This makes it possible to position the engaging member 16B restricted by the restricting unit 18g on the base end side of the engaging member 16A driven by the engagement drive unit 18h, and the positional relationship between the engaging members 16A and 16B can be defined solely by the shape and structure of the drive member 18, thus enabling simplification and miniaturization of the structure.

[0064] Furthermore, the device is further equipped with an elastic member 17B, which is a second elastic member that supports the engaging member 16B with an elastic force directed toward the proximal end. This allows the engaging member 16B to be biased toward the proximal end and maintain a non-retaining position unless an external force is applied, and also facilitates the insertion of the bone fixation device 23 into the transverse hole 13.

[0065] Furthermore, the drive member 18 includes an engagement drive unit 18h that drives the engagement member 16A by contacting the outer circumference of the engagement member 16B. As a result, the drive member 18 is configured to drive the engagement member 16A by contacting the outer circumference of the engagement member 16B, which allows for a simple configuration without complicating the internal mechanism and also suppresses the increase in size of the internal mechanism.

[0066] Furthermore, in the above case, by configuring the contact area between the engaging drive unit 18h and the engaging member 16A to be annular, it is possible to achieve high-precision and reliable operation while avoiding complexity and size increases of the internal mechanism.

[0067] Furthermore, the drive member 18 is rotatably positioned inside the implant body 11 and is configured to be able to drive the engagement member 16A toward the tip by being rotated by a rotational operation. This ensures high precision and reliable operation while maintaining good operability.

[0068] Furthermore, the drive member 18 is configured to move in a direction along the axis 11x when it receives the rotational operation, and when it moves toward the tip, it presses the engaging member 16A against the bone fixation device 15. This allows the internal mechanism to be made even simpler and more compact.

[0069] Furthermore, by further providing end caps 21A and 21B, which are second drive members that engage the engaging member 16B with the bone fixation device 23 by driving the engaging member 16B toward the tip side in the direction along the axis 11x, the holding operation of the bone fixation device 23 can be achieved with good operability.

[0070] In this case, the second drive members, the end caps 21A and 21B, are attached to the proximal end of the implant body 11, thereby driving the engaging member 16B. This allows the bone fixation device 23 to be held in place using the same procedure as the normal end cap attachment procedure.

[0071] The device further includes end caps 21A and 21B, which are second drive members that engage the engaging member 16B with the bone fixation device 23 by driving the engaging member 16B toward the tip in the direction along the axis 11x. These end caps 21A and 21B engage and drive the engaging member 16B through the axial hole 18a of the drive member 18. As a result, by simply attaching the end caps 21A and 21B, the engaging member 16B can be changed from a non-retaining position to a retaining position without the drive member 18 becoming an obstacle, and the bone fixation device 23 can be held. This makes it possible to configure the operation for holding the bone fixation device 23 to be extremely easy while avoiding complexity and size increase of the internal mechanism.

[0072] In this case, the second drive member, which consists of end caps 21A and 21B, is positioned by contacting a part of the internal mechanism of the implant body 11 (drive member 18 and retaining member 19). This makes it easier to attach the second drive member and ensures that its operation is accurate and reliable, and moreover, it prevents postoperative problems caused by loosening or deformation of screws by pressing on a part of the internal mechanism as described above.

[0073] The bone fixation device 10 of the embodiment described above is installed in the patient's body as follows. First, with a target device (not shown) connected to the proximal opening 11b of the implant body 11, it is introduced into the bone marrow, which has been previously opened using a reamer or the like, from the proximal part of the patient's femur. Next, the insertion instrument is attached using the guidance function of the target device, and the bone fixation device 15 is introduced by screwing it in after drilling. After that, the fracture site (femoral head) is held in a reduced state, and the drive member 18 is operated to hold the bone fixation device 15 via the engagement member 16A. Subsequently, the bone fixation device 23 is introduced into the femoral neck by screwing it in after drilling a transverse hole 13 using the insertion instrument, thereby preventing the fracture site from rotating, and the target device and insertion instrument are removed. After that, the end cap 21A or 21B is attached to the shaft hole 11a, and the bone fixation device 23 is held via the engagement member 16B.

[0074] In the surgical procedure described above, by simplifying and miniaturizing the internal mechanism consisting of engaging members 16A, 16B, a drive member 18, and a holding member 19, sufficient rigidity can be ensured while making the implant body 11 (intramedullary nail) more compact, thereby reducing the burden on the patient. In particular, in order to securely hold the fracture site in a reduced state after inserting the bone fixation device 15 into the femoral head at the fracture site by separating the engaging member 16A and passing it through the transverse hole 12 at the tip, it is necessary to first hold the bone fixation device 15 to the implant body 11 to a certain extent, and then, for example, pull the bone fixation device 15 to adjust the position of the fracture site relative to the diaphysis and achieve a reduced state. For this reason, in order to hold the fracture site with the bone fixation device 15, the drive member 18 is operated to set the engaging member 16A to the engaged position. At this point, guide pin insertion and drilling operations are performed to introduce the bone fixation device 23 to prevent rotation of the fracture site, and the bone fixation device 23 is inserted into the transverse hole 13 and introduced into the femoral neck. Therefore, even if the engaging member 16A is in the engaged position, it is important that the engaging member 16B is in the non-retaining position. The internal mechanism of this embodiment suitably achieves the above without imposing any constraints on the engaging member 16B. Once the bone fixation device 23 is introduced, the target device and insertion instrument are removed, and finally, the end cap 21A or 21B is selected and attached to the proximal opening 11b of the implant body 11. At this time, the retention mode of the bone fixation device 23 can be widely realized according to various requirements, not limited to the two types of lock L and lock S described above, by securing the length and range of movement of the engaging member 16B, while avoiding complexity and enlargement of the internal mechanism, thanks to the features of the internal mechanism of this embodiment.

[0075] It should be noted that the bone fixation device of the present invention is not limited to the embodiments described above, and various modifications can be made that fall within the scope of the present invention. For example, in the above embodiments, an end cap is used as the second drive member, but it is also possible to use a drive member that is operably built into the implant body, similar to the first drive member. For example, it is possible to provide another drive member that has a rotatable structure, is screwed into the female threads 11d and 19e, is configured to be movable in the direction along the axis 11x, and can engage with the engaging member 16B through the drive member 18.

[0076] Furthermore, in the above embodiment, the engagement mode between the engaging member 16A and the bone fixation device 15 is configured such that different holding modes occur with respect to the multiple engaging portions 15c and 15d provided on the bone fixation device 15. However, the present invention is not limited to such configurations and may be applied to structures where only a single holding mode is possible, or to structures where a different holding mode than the one described in the embodiment is possible. [Explanation of Symbols]

[0077] 10,30…Bone fixation device, 11,31…Implant body (intramedullary nail body), 11x…Axis, 11A…Proximal region, 11B…Proximal region, 11a…Axis hole, 11b…Proximal opening, 11c…Keyway, 11d…Female thread, 11e…Rotation restrictor, 12,13,14A,14B…Transverse hole, 12x,13x,14ax,14bx,14by…Axis, 15,23…Bone fixation device, 15 a,23a...shaft hole, 15x,23x...axis, 15s,23s...bone engagement part, 15b...connecting part, 15c,15d...engaging part, 15k...keyway, 16A...engaging member, 16Aa...shaft hole (shaft hole), 16As...engaging part, 16Ab...base end, 16Ac...through hole, 16Ae...rotation restricting part, 16B...engaging member, 16Ba...shaft hole (shaft hole), 16Bs...engaging part, 16Bb...base end, 1 6Bc...Elastic part, 17A...Elastic member, 17B...Elastic member, 18...Drive member, 18a...Shaft hole (shaft hole), 18b...Base end, 18c...Tool engagement part, 18d...Male thread, 18e...Housing part, 18f...Opening, 18g...Restricting part, 18h...Engaging drive part, 19...Retaining member, 19a...Opening, 19b...Tool engagement part, 19c...Tip part, 19d...Male thread, 19e...Female thread, 21A,2 1B…End cap, 21Aa,21Ba…Tip, 21Ab,21Bb…Tool engagement part, 21Ac,21Bc…Male thread, 21Ad,21Ae,21Af,21Bd,21Be,21Bf…Stepped section, LL…Lock line, FL…Free line, 23b…Shaft section, 23c…Head, Ld…Operating range, Le…Base end difference, ΔL,ΔS…Relative position of stepped sections 21Af,21Bf

Claims

1. A first bone fixation device and a second bone fixation device are introduced into the bone, The implant body comprises a first transverse hole provided on the tip side in the direction along the axis of the implant body through which the first bone fixation device is inserted, and a second transverse hole provided on the proximal end side in the direction along the axis of the implant body through which the second bone fixation device is inserted, and is positioned inside the bone, A first engaging member is configured to be movable in a direction along the axis of the implant body and holds the first bone fixation device, which is inserted through the first transverse hole, to the implant body, A first drive member that drives the first engaging member in a direction along the axis to engage the first engaging member with the first bone fixation device, The device comprises a second engaging member configured to be movable in a direction along the aforementioned axis, and which holds the second bone fixation device inserted through the second transverse hole relative to the implant body, The first engaging member and the first driving member each have a shaft hole, The second engaging member is arranged to be movable in a direction along the axis within a range of movement from a position where the base end of the second engaging member is located closer to the base end than the base end of the first engaging member within the shaft hole of the first driving member, extending towards the tip, passing through the shaft hole of the first engaging member, and reaching the second transverse hole; and is provided with an engaging portion that engages to hold the second bone fixator, and the engaging portion is configured to be movable between a non-holding configuration that does not hold the second bone fixator and a holding configuration that engages with and holds the second bone fixator. The second engaging member is positioned by restricting its movement toward the base end side by a restricting portion provided on the first driving member. Bone fixation device.

2. The base end of the second engaging member in the non-retaining position is positioned on the base end side relative to the base end of the first engaging member, and when the second engaging member moves toward the retaining position, the misalignment between the base end of the second engaging member and the base end of the first engaging member is reduced. The bone fixation device according to claim 1.

3. The first drive member is, An operating section formed on the base end side and configured to enable operation for driving the first engaging member, A housing portion that opens towards the tip side and can accommodate at least the base end portion of the second engaging member, which constitutes the shaft hole of the first driving member that communicates with the shaft hole of the first engaging member, Having, The bone fixation device according to claim 1 or 2.

4. The shaft hole of the first drive member penetrates in a direction along the axis, The operating section and the housing section are formed by the shaft hole of the first drive member. The bone fixation device according to claim 3.

5. The first drive member has an engagement drive unit that engages with the first engagement member and drives it, The restricting portion of the first drive member is set on the base end side of the engaging drive portion. The bone fixation device according to claim 1 or 2.

6. The system further comprises a second elastic member that supports the second engaging member by an elastic force directed toward the base end, The bone fixation device according to claim 1 or 2.

7. The first drive member includes an engagement drive unit that drives the second engagement member by contacting the first engagement member on the outer circumference side. The bone fixation device according to claim 1 or 2.

8. The contact area between the engagement drive unit and the first engagement member is configured in an annular shape. The bone fixation device according to claim 7.

9. The first drive member is rotatably positioned inside the implant body and is configured to be able to drive the first engagement member toward the tip by being rotated by a rotational operation. The bone fixation device according to claim 1 or 2.

10. The first drive member is configured to be movable in a direction along the axis when it receives the rotational operation, and when it moves toward the tip, it presses the first engaging member against the bone fixation device. The bone fixation device according to claim 9.

11. The device further comprises a second drive member that drives the second engaging member to engage the second engaging member with the second bone fixation device. The bone fixation device according to claim 1 or 2.

12. The second drive member is attached to the proximal end of the implant body to drive the second engaging member. The bone fixation device according to claim 11.

13. The device further comprises a second drive member that drives the second engaging member to engage the second engaging member with the second bone fixation device, The second drive member engages and drives the second engaging member through the shaft hole of the first drive member. The bone fixation device according to claim 4.

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