JP7239970B2 - bone fixation system - Google Patents

Description

The present invention relates to bone fixation systems.

As a bone fixation system for fixing a fracture of a condyle of a tubular bone such as a femur, a bolt having a head portion engaging a washer abutting against the surface of the bone and a rod portion provided with an external thread, and the surface of the bone. There is known a nut having a female thread that engages a washer that abuts on the male thread and is screwable with the male thread (see, for example, Patent Documents 1 and 2 below). Further, as another bone fixation system, an insertion rod is inserted into the condyle and has male threads on both ends, and an elastic engaging part that engages with a washer that contacts the surface of the bone and can be elastically engaged with the male thread. and a pair of nuts respectively engaged with both ends of the insertion rod (see, for example, Patent Document 3 below).

In each of the bone fixation systems described above, in order to firmly fix a bone fragment even in a complicated fracture mode that occurs in the condyle, the fractured condyle is penetrated and fixed by clamping from both sides with the above-mentioned washers. I'm trying Such a bone fixation system holds and fixes each bone fragment of a fractured portion by connecting two fixtures to each other, and is not limited to Patent Documents 1 to 3, and includes various structures. Are known.

JP-A-10-85233 Japanese Patent Publication No. 2004-527276 International Publication No. 2016/144589

By the way, in the bone fixation system having the bolt and nut, the bolt and nut are connected by screwing the male thread of the rod portion and the female thread of the nut, so that the condyles are clamped from both sides by tightening the screws. Sometimes the axial force prevents the screw from loosening and the fracture is retained. However, as time elapses after surgery, the fractured part loses its compressed state due to redislocation in the postoperative process, so the axial force due to the screw engagement decreases or disappears. As a result, there is a problem that the threaded engagement becomes easy to loosen and dislocation of the bone fracture cannot be suppressed.

On the other hand, in the above-described bone fixation system having a structure in which a pair of nuts are elastically engaged with both ends of the insertion rod, the elastic engaging portion of the nut is elastically engaged with the male thread of the insertion rod so that the nut is attached to the insertion rod. Although it has the advantage that it can be easily installed simply by pressing it in the axial direction, it is the same as the above in that it is screwed, so as in the above, loosening due to a decrease in axial force cannot be avoided. .

Therefore, the present invention is intended to solve the above problems, and its object is to provide a connection structure in a bone fixation system that can prevent loosening of screw joints due to a decrease in axial force and can suppress dislocation of a fractured part after surgery. to do.

In order to solve the above problems, the bone fixation system of the present invention includes: a first fastener having a first bone engaging portion and a first screw coupling portion; a second bone engaging portion; a second fastener with a threaded connection and a second threaded connection that is threadably connectable, the threaded connection between said first threaded connection and said second threaded connection; A bone fixation system in which the first fastener and the second fastener are coupled. At this time, the first fixture further comprises a first engaging joint, and the second fixture is adapted to allow relative spiral movement as the depth of the threaded joint increases or decreases. It further comprises a second engagement joint that can be engaged with the first engagement joint. The first engagement coupling portion and the second engagement coupling portion are provided between the first fixture and the second fixture arranged along the direction of the relative spiral motion. At engagement positions corresponding to a plurality of holding positions, the first fixture and the second fixture are configured to be engaged and coupled to each other in such a manner that a holding force is generated between the first fixture and the second fixture at the holding positions. , relatively move between the plurality of engagement positions while engaging and disengaging with the relative spiral motion.

In the present invention, the first engagement coupling portion and the second engagement coupling portion are elastic engagements provided in at least one of the first engagement coupling portion and the second engagement coupling portion. It is preferable that they are configured so that they can be engaged and coupled by their structure.

In the present invention, the first fixture has a first end and an end opposite to the first end provided with the first bone engaging portion, and a second fastener having a second end and an end opposite the second end provided with the second bone engaging portion; and the second fixture are configured so that the first end and the second end can be connected by inserting them into each other in a posture facing each other in the axial direction of the screw connection. preferably.

In the present invention, the first threaded joint and the first engaging joint are arranged in order in the axial direction of the threaded joint, and the second threaded joint and the second engaging joint are arranged in sequence. are preferably arranged in the axial direction in an order corresponding to the arrangement order of the first screw coupling portion and the first engaging coupling portion.

In this case, the first threaded coupling portion comprises a male thread, the second threaded coupling portion comprises a female thread that can be screwed onto the male thread, and the first engaging coupling portion comprises the first thread. The second engaging coupling portion is provided on the first end side of the coupling portion, and the second engaging coupling portion is provided on the side opposite to the second end side of the second screw coupling portion. It is desirable that the one engaging coupling portion has a diameter smaller than that of the second threaded coupling portion. In this case, it is further desirable that the first fixture is longer in the axial direction than the second fixture.

Also, the first threaded joint has a male thread, the second threaded joint has a female thread that can be screwed to the male thread, and the first engaging joint has a structure similar to that of the first threaded joint. The second engaging coupling portion is provided on the side opposite to the second end side of the second screw coupling portion, and the first It is desirable that the engaging coupling portion has a diameter smaller than that of the first threaded coupling portion. In this case, it is further desirable that the first fixture is longer in the axial direction than the second fixture.

In the present invention, when connecting the first fixture and the second fixture, after the screw connection between the first screw joint and the second screw joint is started, the It is desirable that the engaging connection between the first engaging connection and the second engaging connection is initiated.

In the present invention, it is preferable that the first engagement coupling portion and the second engagement coupling portion are configured to be engaged and coupled in the axial direction of the screw coupling at the engagement position. In this case, one of the first engagement coupling portion and the second engagement coupling portion has an annular portion around the axis provided at the engagement position. It is desirable that a plurality of engaging structures be arranged in the direction, and that the other engaging coupling portion has an engaging end portion that can be engaged with the annular portion in the axial direction.

In the present invention, it is preferable that the annular portion is an annular groove or an annular projection, and the engaging end portion is an elastic projection or an elastic recess. In particular, it is desirable that the annular portion is an annular groove, and the engaging end portion is engageable with the annular groove. Here, it is more desirable that the engaging end portion is configured by an elastic engaging end. In this case, it is preferable that the elastic engaging end is provided on a ring-shaped elastic engaging body around the axis. At this time, it is more preferable that the elastic engaging end is divided into a plurality of parts by a notch or the like so as to be arranged around the axis. Further, the elastic engaging body may be an expandable/contractible elastic body, for example, a C-ring-shaped elastic body having cutouts at predetermined positions around the axis.

In the present invention, the holding force at the holding position based on the locking force of the engagement coupling at the engagement position between the first engagement coupling portion and the second engagement coupling portion, The retaining force resisting movement in the direction of the relative helical movement in the direction of increasing the depth of the threaded connection is relatively small, and the depth of the threaded connection in the direction of the relative helical movement decreases. Preferably, said holding force against directional movement is relatively large.

In the present invention, each of the first bone engaging portion and the second bone engaging portion may have a structure that engages the bone in some way. It may be a washer, a head portion (bolt head) that is larger than the shaft portion, or a screw or nail that engages by screwing into the bone. Also, the first bone engaging portion and the second bone engaging portion may be bone plates.

In the present invention, it is configured to be connectable to one of the first fixture and the second fixture in a rotationally engaged state, and rotate the one fixture around the axis of the screw connection. It is preferable to further comprise a tool for rotating operation. In this case, the tool moves along the axis through the inside of the one fixture in accordance with the depth of the threaded connection while being connected to the one fixture. It is desirable to have a detection shaft having a tip with which the end abuts, and a display section for displaying the position of the end of the other fixture according to the position of the detection shaft. Further, it is further preferable that the presence or absence of the engagement connection can be confirmed by the position of the detection shaft that interlocks with the end portion of the other fixture in the display section. Furthermore, it is preferable that the display section displays the position of the proximal end of the detection shaft.

According to this invention, in the bone fixation system, the retention force obtained from the locking force of the engagement connection between the first engagement connection portion and the second engagement connection portion reduces the axial force. Even if there is, loosening of the screw connection between the first screw connection portion and the second screw connection portion can be prevented, so dislocation of the fractured portion can be suppressed.

FIG. 3A is a side view (a) and an end view (b) of a first fixture, and a side view (c) and an end view (d) of a second fixture showing the overall configuration of an embodiment of a bone fixation system; It is the side view (a), end view (b), and sectional drawing (c) which show the 1st fixing tool of the same embodiment. It is the sectional view (b) and end view (c) which show the enlarged vertical side view (a), the elastic engaging body which expands, and shows the 2nd fixing tool of the same embodiment. Fig. 10(a) to (d) show states in which the first fixture and the second fixture of the same embodiment are connected at different depth positions of screw connection. FIG. 10 is a side view (a) and cross-sectional view (b) showing a tool for engaging and manipulating the first fixture; FIG. 10 is a side view (a) and cross-sectional view (b) showing a tool for engaging and manipulating the second fixture;

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. First, referring to FIGS. 1 to 3, the overall configuration of an embodiment of a bone fixation system according to the present invention will be described. As shown in FIG. 1, the bone fixation system 10 of this embodiment includes a first fastener 11 constituting a medical bolt and a first fastener 11 for a first end 11a of the first fastener 11. and a second fixture 12 constituting a nut for medical use, which is mounted in an axially facing posture with two ends 12a facing each other.

As shown in FIG. 2, the first fixture 11 includes a first end portion 11a, a head portion 11b provided at the end opposite to the first end portion 11a, and a first end portion. It has a shaft portion 11c extending between 11a and head portion 11b. The first end portion 11a is provided with a first screw connection portion _11a1 , and a first engaging connection portion _11a2 is formed on the edge side of the first screw connection portion _11a1 . be. Here, the first engaging coupling portion _11a2 and the first screw coupling portion _11a1 are arranged in order ( coaxial). The first threaded coupling portion _11a1 has male threads 11t formed at a predetermined pitch in the axial direction. Also, the first engaging coupling portion _11a2 has an engaging structure 11g including a plurality of annular grooves corresponding to a plurality of holding positions in the axial direction. Here, in the illustrated example of the engaging structure 11g, the inclination angle (40 degrees in the illustrated example) of the inner side surface 11g1 of each annular groove on the side of the first end _11a (left side in the drawing) with respect to the plane orthogonal to the axial direction is large, and the inclination angle (5 degrees in the example shown) of the inner side surface 11g2 on the side opposite to the first end _11a (right side in the drawing) of each annular groove with respect to the plane orthogonal to the axial direction is small.

A socket portion 11d having, for example, a hexagonal hole shape, which can be engaged with a rotating operation tool 13 shown in FIG. It is formed. The first fixture 11 preferably has an axial hole therethrough so that it can be guided by a guide pin, as shown. A first bone engaging portion 11f is attached to the head portion 11b. The first bone engaging portion 11f is mounted on the outer surface of the head portion 11b so that the angle can be changed (the angle is freely changed). Moreover, it is preferable that the first bone engaging portion 11f is configured to be rotatable around the axis with respect to the head portion 11b. The first bone engaging portion 11f includes an annular main body _11f2 having a flange portion _11f1 projecting around the periphery, and an elastic groove _11f3 formed in the inner surface of the opening of the main body _11f2 . ring _11f4 . The elastic ring _11f4 is configured in a C-ring shape with a notch in the illustrated example. This elastic ring _11f4 has a retaining function to prevent the first bone engaging portion 11f from coming off from the head portion 11b toward the first end portion 11a, or a retaining function to retain it on the head portion 11b. Fulfill. The main body _11f2 of the first bone engaging portion 11f is configured to prevent the head portion 11b from coming off to the side opposite to the first end portion 11a. Here, in order to facilitate the angle change operation between the head portion 11b and the first bone engaging portion 11f, the outer surface of the head portion 11b and the inner surface of the main body _11f2 and the elastic ring _11f4 facing the outer surface of the head portion 11b are arranged. Preferably, each of the inner surfaces of is configured spherically with corresponding irregularities.

The second fixture 12, as shown in FIG. 3, has a second end 12a, a head portion 12b provided at the opposite end of the second end 12a, and a second end 12a. 12a and a shaft portion 12c extending between the head portion 12b. In the illustrated example, the shaft portion 12c is shorter than the shaft portion 11c because the second fastener 12 constitutes a nut corresponding to the first fastener 11 which constitutes a bolt. The second fixture 12 has an axial hole 12j extending therethrough in the axial direction. The inner surface of the shaft hole 12j is provided with a second screw coupling portion _12a1 in a region on the side of the second end portion 12a. The second threaded connection portion _12a1 has a female thread 12t that can be screwed to the male thread 11t. In this embodiment, the first end portion 11a of the first fixing member 11 is arranged to face the second end portion 12a of the second fixing member 12 in the axial direction. is inserted into the second end portion 12a, the screw connection can be made without any trouble.

Further, an enlarged hole portion 12k is formed in the shaft hole 12j in a region closer to the head portion 12b than the second screw connection portion _12a1 . The enlarged hole portion 12k has an inner diameter larger than the inner diameter of the internal thread 12t. A second engaging coupling portion _12b1 is formed inside the enlarged hole portion 12k. The second engaging coupling portion _12b1 has an elastic engaging body 12p including an elastic engaging end 12q that engages the annular groove of the engaging structure 11g. In the illustrated example, the elastic engaging end 12q of the elastic engaging body 12p is configured by a hook-shaped elastic projection protruding radially inward. However, this elastic engaging end 12q may be configured as an elastic recess when the engaging structure 11g of the first engaging coupling portion _11a2 is configured as an annular protrusion. A space is provided on the outer peripheral side of the elastic engaging end 12q so that the elastic engaging body 12p can be deformed radially outward. In the illustrated example, the outer surface 12q1 of the elastic engaging end 12q on the side of the second end 12a (left side in the drawing) has a large inclination angle (40 degrees in the illustrated example) with respect to _the plane perpendicular to the axial direction. The inclination angle (5 degrees in the example shown) of the outer side surface 12q2 on the side opposite to the end _12a (right side in the drawing) with respect to the plane perpendicular to the axial direction is small.

The elastic engaging member 12p is composed of a ring-shaped elastic body. Metals and synthetic resins can be used as the elastic body, and metals such as medical titanium alloys are particularly preferable. The elastic engaging end 12q is configured to be deformable and movable in radial and axial directions mainly by elastic deformation of the cylindrical portion of the elastic engaging body 12p. The elastic engaging member 12p is configured in a C-ring shape partially provided with a notch portion 12s. The elastic engaging end 12q protrudes radially inward from the edge of the ring-shaped elastic engaging body 12p on the second end 12a side. Further, a plurality of notches 12r are provided on the inner edge of the elastic engaging member 12p at intervals in the circumferential direction, so that the elastic engaging end 12q is divided around the axis. As a result, a plurality of elastic engaging ends 12q are formed around the axis of the elastic engaging body 12p. By providing the notch portion 12s and the notch portion 12r in this way, even though the elastic engaging member 12p is configured in a ring shape, when the engaging structure 11g moves between adjacent holding positions, This prevents plastic deformation of the elastic engaging member 12p and facilitates elastic deformation of each elastic engaging end 12q in the axial direction. The elastic engaging member 12p is supported by an annular holding frame 12u arranged in the enlarged hole portion 12k. The holding frame 12u is held on the inner surface of the enlarged hole portion 12k by an elastic locking ring 12w which is locked in a locking groove (annular groove) 12v formed in the enlarged hole portion 12k.

Further, a second bone engaging portion 12f is attached to the head portion 12b, which is configured in the shape of a washer (plate) and is formed so as to be able to engage with the surface of the bone. The second bone engaging portion 12f is mounted on the outer surface of the head portion 12b so that the angle can be changed (the angle is freely changed). Also, the second bone engaging portion 12f is preferably configured to be rotatable around the axis with respect to the head portion 12b. The second bone-engaging portion 12f includes an annular body _12f2 having a flange portion _12f1 projecting around the circumference and an elastic groove _12f3 formed in the inner surface of the opening of the body _12f2 . ring _12f4 . The elastic ring _12f4 is configured in a C-ring shape with a notch in the illustrated example. This elastic ring _12f4 has a retaining function to prevent the main body _12f2 of the second bone engaging portion 12f from coming off from the head portion 12b toward the second end portion 12a, or it has a holding function on the head portion 12b. perform a holding function. The main body _12f2 of the second bone engaging portion 12f is configured to prevent the head portion 12b from coming off to the side opposite to the second end portion 12a. Here, in order to smoothly change the angle between the head portion 12b and the second bone engaging portion 12f, the outer surface of the head portion 12b and the inner surface of the main body _12f2 or the elastic ring _12f4 facing the outer surface of the head portion 12b are arranged. Preferably, each of the inner surfaces of is configured spherically with corresponding irregularities.

In the case of this embodiment, when the depth of the threaded connection between the male thread 11t and the female thread 12t increases or decreases, the first fixture 11 and the second fixture 12 perform relative spiral motion around the axis. . At this time, the engagement operation between the engagement structure 11g and the elastic engagement end 12q is configured so as not to interfere with the relative spiral movement. Further, a holding force is generated at each of the plurality of holding positions arranged along the direction of the relative spiral motion by the locking force obtained at each engaging position by the engaging operation. In order to provide such a holding force, each annular groove of the first engagement joint portion 11a2 (engagement structure 11g) and the second engagement joint portion 12b1 (elastic engagement end 12q) are provided with the plurality of , and are configured to be disengageable from each other in order to move relative to each other between the engaging positions in accordance with the relative spiral motion. Here, the engaging structure 11g and the elastic engaging end 12q are engaged in the axial direction of the screw connection. 2 is rotatably attached to the second fixture 12, and the engaging structure 11g and the elastic engaging end 12q are engaged so as not to rotate with each other; It is different from the case where it is fixed and the engaging structure 11g and the elastic engaging end 12q are rotatably engaged with each other. Further, as in this embodiment, the elastic engaging member 12p is rotatably attached to the second fixture 12, and the engaging structure 11g and the elastic engaging end 12q are rotatably engaged with each other. It can be considered that each case is different. However, regardless of what motion trajectory the structure actually adopts, the structure is set along the direction of the relative spiral motion occurring between the first fixture 11 and the second fixture 12. A locking force corresponding to the holding force is applied at each engaging position corresponding to the plurality of holding positions.

The above-described retaining function of the first bone engaging portion 11f and the second bone engaging portion 12f is achieved by the following structure. That is, the annular grooves 11f ₃ and 12f ₃ are deep groove portions 11f _3a and 12f _3a capable of accommodating the entirety of the elastic rings 11f ₄ and 12f ₄ in the width direction, and the deep groove portions 11f _3a and 12f _3a are provided with the first and shallow groove portions 11f _3b and 12f _3b continuously provided on the opposite side of the end portion 11a and the second end portion 12a. Here, when the deep groove portions 11f _3a and 12f _3a accommodate the elastic rings 11f ₄ and 12f ₄ , the maximum outer diameter portions of the head portions 11b and 12b can pass inside the elastic rings 11f ₄ and 12f ₄ . Even if the shallow groove portions 11f _3b and 12f _3b accommodate the elastic rings 11f ₄ and 12f ₄ , the maximum outer diameter portions of the head portions 11b and 12b cannot pass inside the elastic rings 11f ₄ and 12f ₄ . Therefore, the first bone engaging portion 11f and the second bone engaging portion 12f are arranged closer to the first end portion 11a and the second end portion 12a than the maximum outer diameter portions of the head portions 11b and 12b. After setting the elastic rings 11f ₄ and 12f ₄ in the annular grooves 11f ₃ and 12f ₃ , the first bone engaging portion 11f and the second bone engaging portion 12f face the head portions 11b and 12b. to the opposite side (right side in the drawing) to the first end portion 11a and the second end portion 12a. Then, the elastic rings 11f ₄ and 12f ₄ are pushed by the head portions 11b and 12b and moved to the side of the deep groove portions 11f _3a and 12f _3a (left side in the figure), where they are housed in the deep groove portions 11f _3a and 12f _3a . Therefore, since the maximum outer diameter portions of the head portions 11b and 12b can pass through the inner sides of the elastic rings 11f ₄ and 12f ₄ , the illustrated state can be achieved.

On the other hand, in the illustrated state, the first bone engaging portion 11f and the second bone engaging portion 12f are moved toward the first end portion 11a and the second end portion 12a of the head portions 11b and 12b (the left side in the drawing). ), the elastic rings 11f ₄ and 12f ₄ are pushed by the head portions 11b and 12b to move toward the shallow groove portions 11f _3b and 12f _3b (right side in the drawing), and as shown in the drawing, the shallow groove portions 11f 3b and 11f _3b , Since they are located within 12f _3b , the maximum outer diameter portions of the head portions 11b and 12b cannot pass inside the elastic rings 11f ₄ and 12f ₄ . Therefore, the first bone engaging portion 11f and the second bone engaging portion 12f cannot be removed from the first end portion 11a and the second end portion 12a of the head portions 11b and 12b. It should be noted that the function of preventing the first bone engaging portion 11f and the second bone engaging portion 12f from coming off toward the first end portion 11a and the second end portion 12a cannot be easily performed manually. It is sufficient if there is a holding force to the extent that it does not come off.

In the first fixture 11, the length in the axial direction of the male thread 11t of the first screw coupling portion _11a1 is _L11 , the outer diameter (the outer diameter of the thread of the male thread 11t) is _D11 , and the first Let L ₁₂ be the length in the axial direction of the engaging structure 11g consisting of the group of annular grooves of the engaging coupling portion 11a ₂ , and D ₁₂ be the outer diameter (the outer diameter of the groove-shaped outer reference surface of the annular groove 11d). Further, in the second fixture 12, the length in the axial direction of the second screw coupling portion _12a1 is _L21 , the inner diameter (the inner diameter of the screw thread of the female screw 12t) is _D21 , and the second engagement coupling portion G ₂₂ is the distance between the axial position of 12b ₁ (elastic engagement end 12q) and the second screw coupling portion 12a ₁ , the inner diameter of the second engagement coupling portion 12b ₁ (elastic engagement end 12q) is inner diameter) is _D22 . At this time, in the present embodiment, L ₂₁ +G ₂₂ >L ₁₂ holds, and as shown in _FIG. At the time when the screw connection with the second screw connection portion _12a1 is started, it can be constructed so that the engagement connection between the first engagement connection portion _11a2 and the second engagement connection portion _12b1 does not occur. . In this case, if the depth _of the screw connection is further increased after that, as shown in _FIG . Engagement coupling is initiated. Therefore, in this embodiment, there is always a connection state by screw connection, and in this connection state, an axial locking force is applied by the elastic engagement structure. Further, in a state where a locking force due to elastic engagement is generated at an engagement position corresponding to one of the holding positions along the direction of the relative spiral movement, the screw connection is always achieved, so the first fixation is achieved. In the presence of the locking force, the locking force is caused by the axial driving force generated through the threaded connection by the rotational operation of the tool 11 and the second fixture 12 to produce relative helical motion therebetween. Nevertheless, it is relatively easy to operate. The operability when the depth of the threaded connection is changed is further facilitated by dividing the elastic engaging end 12q in the circumferential direction by the notch portion 12s and the notch portion 12r as described above.

In addition, in the present embodiment, when D ₂₁ > D ₁₁ is established, when the first end portion 11a is inserted into the second end portion 12a, the first engagement coupling portion 11a ₂ (engagement structure 11g) does not interfere with the threads of the second threaded joint 12a ₁ (female thread 12t), so that the first threaded joint 11a ₁ (male thread 11t) and the second threaded joint 12a1 (female thread 12t) can be connected without any trouble. ) can be screwed together. In addition, in order to make such a configuration, D ₁₁ >D ₁₂ must be established because D ₁₂ >D ₂₁ must be satisfied in order to enable screw coupling.

Further, when the inner diameter of the enlarged hole portion 12k is _D20 , it is preferable to set the inner diameter _D20 large so that _D20 > _D21 is established between the enlarged hole portion 12k and the inner diameter _D21 of the internal thread 12t. As a result, D ₂₀ -D ₂₂ becomes larger, so that it becomes easier to secure the elastic engaging end 12q and the space that allows it to be deformed toward the outer peripheral side. Here, since D ₂₀ - D ₂₂ = (D ₂₀ - D ₂₁ ) + (D ₂₁ - _{D 22} ), the accommodation margin of the elastic engagement structure in the radial direction is the first and second terms of this formula. is calculated by adding Therefore, as D ₂₀ increases, the first term of D ₂₀ -D ₂₁ increases, and an advantageous effect of increasing the accommodation margin of the elastic engagement structure is obtained. It is further facilitated to reduce the diameter of the fixture 12. When the above-mentioned condition of D ₁₁ >D ₁₂ is satisfied, the inner diameter D ₂₂ of the elastic engaging end 12q engaged with the engaging structure 11g is smaller than that of the male thread 11t by an amount corresponding to that of the female thread 12t. Since the diameter can be further reduced, the effect similar to the above can be obtained by increasing the second term. These effects are generally more complicated and larger in diameter than the structure required for screw connection. This is because there is a large margin for reducing the diameter of the second fixture 12 .

Furthermore, in the present embodiment, in the first fixture 11, the first screw coupling portion _11a1 and the first engaging coupling portion _11a2 are arranged adjacent to each other in the axial direction. , in the second fixture 12, the second screw coupling portion _12a1 and the second engaging coupling portion _12b1 are arranged adjacent to each other in the axial direction. In this way, although the length along the axial direction increases, the portion where the screw connection occurs and the portion where the (elastic) engagement connection occurs can be configured separately in the axial direction, thereby simplifying the structure. In addition, the first engaging coupling portion _11a2 is arranged on the first end portion 11a side, the first screw coupling portion _11a1 is arranged on the opposite side, and the second screw coupling portion is arranged on the second end portion 12a side. 12a- ₁ and the second engaging coupling portion 12b- ₁ are arranged on the opposite side. As a result, in the second fixture 12, the shaft portion 12c of which is shorter than that of the first fixture 11, the second engagement coupling portion _12b1 is provided on the side of the head portion 12b, which can be configured to have a larger outer diameter. Since it can be arranged, it also becomes easy to reduce the diameter of the second fixture 12 . In the bone fixation system, it is important to reduce the diameter of the implant in order to reduce the burden on the patient.

In this embodiment, in order to screw-couple the first threaded joint 11a ₁ (male thread 11t) of the first fixture 11 to the second threaded joint 12a ₁ (female thread 12t) of the second fixture 12, At the time of connecting operation, the first threaded joint 11a- ₁ and the second threaded joint 12a- ₁ must be helically moved relative to each other around the axis. Therefore, the first screw connection portion 11a ₁ and the second screw connection portion 12a ₁ are allowed to relatively spirally move around the axis, and at least the first engagement connection portion 11a _{2 (engagement connection portion 11a 2} The joint structure 11g) and the second engagement coupling portion 12b ₁ (elastic engagement end 12q) are engaged and coupled at the engagement positions corresponding to the plurality of holding positions without hindrance, whereby the engagement corresponding to the holding force is achieved. A stopping force must be generated. In order to do this, the first engagement coupling portion _11a2 and the second engagement coupling portion _12b1 are engaged with each other in such a manner as to generate a locking force component in the direction of the relative spiral motion. At the same time, it is necessary that the engagement mode has a structure that permits relative spiral motion. As described above, in the present embodiment, the engaging structure 11g and the elastic engaging end 12q are provided with a structure in which they engage with each other in the axial direction. Examples of the engagement direction in the aspect in which the component of the locking force is generated in the direction of the relative spiral motion include, in addition to the above-described axial direction as in the present embodiment, a direction around the axis and a direction, etc. Regardless of the direction of engagement, as long as the locking force generated by the engagement has a component along the direction of the relative helical movement, the first fixture 11 and the first fixture 11 can be held at a plurality of holding positions. A retention force is provided between the second fasteners 12 . Further, when the first fixture 11 and the second fixture 12 move relative to each other between a plurality of holding positions along the direction of the relative spiral motion, the axial line is moved at the engaging positions corresponding to the holding positions. The engaging structure 11g and the elastic engaging end 12q that are engaged in the direction move relatively while repeating the engaging and disengaging operation.

Further, in this embodiment, the engagement structure 11g and the elastic engagement end 12q are arranged in the above-described manner in order to allow the relative spiral motion without hindering the generation of the locking force at the plurality of engagement positions. In addition to the configuration that allows engagement and disengagement operations in the axial direction engagement connection mode, the second fixture 12 (female screw 12t) and the elastic engagement body 12p are configured to be rotatable relative to each other around the axis. It is fixed in the axial direction and rotatable around the axis. However, although different from this embodiment, the first fixture 11 (male screw 11t) and the engaging structure 11g may be fixed in the axial direction and rotatable around the axis. As described above, the second fixture 12 (second threaded coupling portion 12a ₁ ) and the second engagement coupling portion 12b ₁ are fixed in the axial direction and are rotatable about the axis. Alternatively, the first fixture 11 (first threaded coupling portion 11a ₁ ) and the first engagement coupling portion 11a ₂ are fixed in the axial direction and are rotatable about the axis. In some cases, there is an advantage that the restrictions on the structure for engagement coupling and the restrictions on the relationship between the structure and the structure for screw coupling can be reduced.

In addition, in this embodiment, the first threaded joint 11a ₁ (male thread 11t) of the first fixture 11 is screwed to the second threaded joint 12a ₁ (female thread 12t) of the second fixture 12. Since the distance Gp between the flange portion 11f1 of the first bone engaging portion _11f and the flange portion 12f1 of the second bone engaging portion _12f can be appropriately set by the relative rotation operation, FIG. As shown in (b) to (d), it is possible to appropriately hold and fix the fractured part (for example, the condyle of the long bone) Bf from both sides according to the situation. At this time, the first engagement joint portion 11a ₂ (engagement structure 11g) and the second engagement joint portion 12b ₁ (elastic engagement end 12q) are elastically engaged with each other, thereby Since the holding function is exhibited at a plurality of engagement positions and the locking force in the axial direction is generated, the holding force in the direction of the relative helical movement based on the locking force is independent of the axial force. loosening can be prevented. In addition, since the locking force in the axial direction is applied superimposedly to the connected state by the screw connection, it is possible to obtain a large holding and fixing force as a whole. It can also withstand loads.

A bone fixation system 10 of the present embodiment comprising a first fixture 11 and a second fixture 12 has a through hole (not shown) made in the bone fracture Bf using a punch such as a drill or reamer, as shown in FIG. It can be installed by inserting the first fixture 11 into the through hole and connecting the second fixture 12 from the opposite side. In this case, the first fixture 11 is attached to the rotating tool 13 shown in FIG. 5, and the second fixture 12 is attached to the rotating tool 14 shown in FIG. .

The tool 13 includes a body shaft 13b having a rotary engaging portion (hexagonal head) 13a at its tip that engages the socket portion (hexagonal hole) 11d of the head portion 11b of the first fixture 11 around the axis, and the main body shaft 13b. It has a grip portion 13c provided at the proximal end of the body shaft 13b, and an engagement shaft 13e having a male threaded portion 13d that protrudes further toward the distal side of the rotary engagement portion 13a through a shaft hole penetrating the interior of the body shaft 13b. The engaging shaft 13e has an operating end 13f protruding from the proximal end of the grip portion 13c. The engaging shaft 13e is inserted movably and rotatably only toward the base end side in the axial direction with respect to the body shaft 13b. Therefore, by screwing the male threaded portion 13d at the tip of the engaging shaft 13e into the screw hole 11e in a state where the rotary engaging portion 13a of the tool 13 is engaged with the socket portion 11d, the main body shaft 13b and the engaging shaft 13e are connected. The first fixture 11 can be held and fixed to the tip of the tool 13 by .

The tool 14 has a body shaft 14b at its tip, which is provided with a rotary engaging portion (hexagonal head) 14a that engages around the axis with a socket portion (hexagonal hole) 12d provided in the head portion 12b of the second fixture 12. and a drive shaft 14c having a distal end portion which is inserted through the shaft hole of the main body shaft 14b and supports the engaging ball 14s from the inside of the rotary engaging portion 14a; and a detection shaft 14f having a tip portion 14e that passes through the shaft hole of the drive shaft 14c and protrudes further to the tip side than the rotation engaging portion 14a. The detection shaft 14f has a proximal end portion 14h disposed within a display portion 14g protruding from the proximal end of the grip portion 14d. The detection shaft 14f is inserted movably in the axial direction while being biased by an elastic member 14i such as a coil spring on the distal end side in the axial direction with respect to the main body shaft 14b.

The drive shaft 14c is configured to be pushed forward through the sliding ring 14k when the lock operation portion 14j screwed to the main body shaft 14b is moved forward, and the engagement ball 14s is pushed radially inward. It is configured such that the supporting portion of the engaging ball 14s is changed from the small diameter portion to the large diameter portion by moving the tip portion supported from the outer side toward the tip side. As a result, when the lock operating portion 14j is rotated and moved to the distal end side in a state in which the rotary engaging portion 14a is inserted into the socket portion 12d of the second fixture 12, the drive shaft 14c is also moved to the distal end side. Since the engaging ball 14s supported at the tip of the drive shaft 14c moves from the small diameter portion to the large diameter portion of the tip, the engaging ball 14s moves from the opening 14z provided in the rotary engaging portion 14a. protrudes outward and fits into a recess 12z (see FIG. 3A) provided on the inner surface of the socket portion 12d of the second fixture 12, so that the second fixture 12 is held and fixed to the tool 14. be done.

With the first fixture 11 held and fixed to the tool 13 and the second fixture 12 held and fixed to the tool 14 as described above, the first end portion 11a of the first fixture 11 and the , and the second end 12a of the second fixture 12 are axially opposed to each other through a through hole formed in the fractured portion Bf. At this time, it is also possible to guide the introduction of the first fixture 11 and the second fixture 12 by using the guide pin used when drilling the through-hole as it is. The bone fixation system 10 of the present embodiment can be applied alone to various fractures Bf. It can also be applied to the fractured part Bf into which the intramedullary nail is inserted. When the bone fixation system 10 is used by being inserted through the transverse hole of the intramedullary nail in this way, it is guided through the transverse hole by a guide pin or a guide sleeve positioned using a target device (not shown). Form matching through-holes.

A first end portion 11a of the first fixing device 11 and a second end portion 12a of the second fixing device 12 are set to face each other in the axial direction through a through hole formed in the fractured part Bf. Then, using the tools 13 and 14 at the same time, the first fixture 11 and the second fixture 12 are coaxially and relatively rotated to connect the first screw connection portion _11a1 and the second screw connection. The portion _12a1 is screwed together. After the screw connection _is started as shown in FIG. 4(a), as _shown in FIGS. are elastically engaged, and the elastic engaging end 12q of the elastic engaging body 12p engages at one of the engaging positions corresponding to the plurality of holding positions on the engaging structure 11g. Here, the fractured part Bf can be held by tightening the fractured part Bf by changing the screwing depth of the threaded connection according to the size of the gap Gp of the fractured part Bf.

At this time, the inner side surface 11g- ₁ of the annular groove of the engaging structure 11g and the outer side surface 12q- ₁ of the elastic engaging end 12q facing the inner side surface 11g-1 are greatly inclined toward the axial direction as described above. When the fixing member 11 and the second fixing member 12 move relative to each other in a direction in which the depth of screw connection increases, the elastic engaging member 12p is easily deformed, and the elastic engaging end 12q easily moves to the outer peripheral side. . Therefore, since the locking force at each engagement position at this time becomes small, when the first fixture 11 and the second fixture 12 move relative to each other in the direction in which the screwing depth of the threaded connection increases. The holding force (resistance force) at each holding position is small. On the other hand, since the inner side surface _11g2 of the annular groove of the engaging structure 11g and the outer side surface 12q2 of the elastic engaging end 12q which faces the inner side surface _11g2 have a small inclination in the axial direction as described above, the first fixing member 11 and the second fixture 12 move relative to each other in the direction in which the screwing depth of the threaded connection decreases, the retaining force at each engagement position increases. resistance) increases. As a result, when tightening the first fixture 11 and the second fixture 12, the tightening torque required for screwing is small, but the holding force in the loosening direction of the screw connection is large. Even if the force is reduced or lost, loosening of the screw is less likely to occur. However, when removing the bone fixation system 10, it is possible to release the screw connection between the first fixture 11 and the second fixture 12, although some operation torque is required.

In addition, in the illustrated example, the form of the engagement connection between the first engagement connection portion 11a ₂ (engagement structure 11g) and the second engagement connection portion 12b ₁ (elastic engagement end 12q) is as follows: The inner diameter of the root of the annular groove of the engaging structure 11g and the inner diameter of the tip of the elastic engaging end 12q are substantially the same, so that they are rotatably engaged with each other with little elastic deformation in the radial direction of the elastic engaging structure. It is As a result, there is almost no sliding resistance during mutual rotation, so that the influence of friction of the engagement coupling portion is less likely to hinder the rotation operation for screw coupling. On the other hand, if the elastic engaging structure is designed to be engaged while elastically deformed in the radial direction, the inner surface of the engaging structure 11g and the tip of the elastic engaging end 12q are constantly pressed in the radial direction by elastic force. As a result, sliding resistance due to friction is generated at the engagement coupling portion, and static friction is also increased. Therefore, it is possible to further enhance the effect of preventing loosening of the screw connection. The engagement coupling structure (elastic engagement coupling structure in which at least one of a pair of mutually engaging structures has an elastic engagement structure) is attached to the engagement structure 11g and the elastic engagement end 12q in the illustrated example. Any structure can be used as long as it functions as a latch structure.

Further, as shown in FIG. 4(d), when the interval Gp corresponding to the fractured part Bf is smaller than the length of the first fixture 11, the first end 11a finally reaches the second fixture. It may protrude from the proximal end of 12. However, if the protruding amount is too large, there is a possibility that the patient may feel pain after surgery. Therefore, in the tool 14, the base end portion 14h of the detection shaft 14f, which is pushed toward the base end side by the protrusion of the first end portion 11a, is visually recognized as protruding from the display portion 14g. It enables it to know the protrusion amount of 11a. If the amount of protrusion is excessive, it is preferable to replace the first fixture 11 with a shorter one. Here, by appropriately setting the projection amount of the tip portion of the detection shaft 14f, the first end portion 11a of the first fixture 11 can be connected to the second fixture in a wider depth range of screw connection. 12 (shaft hole 12j) can be made contactable with the tip of the detection shaft 14f. In this way, by viewing the position of the base end portion 14h on the display portion 14g in a state where the second fixture 12 is held and fixed to the tool 14, the depth of the screw connection can be determined in a wider range at hand (display portion 14g). 14g). Also, whether or not the second engagement coupling portion 11b ₁ (elastic engagement end 12q) is engaged with the first engagement coupling portion 11a ₂ (engagement structure 11g) (for example, FIG. 4(c) or the state of FIG. 4A) can be known on the display section 14g by the position of the base end portion 14h of the detection shaft 14f pushed by the first end portion 11a. can also

It should be noted that the bone fixation system according to the present invention is not limited to the illustrated examples described above, and it goes without saying that various modifications can be made without departing from the gist of the present invention. For example, in the above embodiment, both the first bone engaging portion 11f and the second bone engaging portion 12f function as washers that engage with the surface of the bone, but the first bone engaging portion and the second bone-engaging portion may be of any type as long as it engages with the bone. It may be a bone plate or the like.

In the illustrated example, the first threaded joint and the first engagement joint, and the second threaded joint and the second engagement joint are arranged in the axial direction. If the rotatable construction condition for the screw connection is satisfied, for example, the first screw connection and the first engagement connection and the second screw connection and the second engagement connection are arranged along the axis. It is also possible to superimpose them in the same direction area (for example, to mutually change the angular positions around the axis).

Furthermore, in the illustrated example, with respect to the engaging structure 11g that constitutes the engaging positions corresponding to the plurality of holding positions, the elastic engaging end engages only with one corresponding engaging position of the engaging structure 11g. 12q. However, instead of this elastic engaging end 12q, in the second engaging joint portion, a plurality of ( A resilient) engagement end may be provided.

The present invention is also applicable to a system in which a nut with a pair of washers is mounted on an insertion rod with external threads on both ends, as disclosed in prior art US Pat. In this case, only one of the ends of the insertion rod may be provided with a structure for engagement coupling.

DESCRIPTION OF SYMBOLS 10... Bone fixation system 11... First fixing tool 11a... First end _11a1 ... First screw connection part _11a2 ... First engagement connection part 11b... Head part 11c... Shaft portion 11d Socket portion 11e Threaded hole 11f First bone engaging portion 11f ₁ Flange portion 11f ₂ Main body 11f ₃ Annular groove 11f ₄ Elastic ring 11t External thread 11g... Annular groove group 12... Second fixture 12a... Second end 12a1... Second screw coupling part _12b ... Head part _12b1 ... Second engaging coupling part 12c... Shaft portion 12d Socket portion 12f Second bone engaging portion 12f ₁ Flange portion 12f ₂ Main body 12f ₃ Annular groove 12f ₄ Elastic ring 12t Internal thread 12j Shaft hole 12k... Enlarged hole, 12p... Elastic engaging member, 12q... Elastic engaging end, 12r... Notch, 12s... Notch, 12u... Holding frame, 12v... Locking groove, 12w... Locking ring

Claims (13)

A first fastener comprising a first bone engaging portion and a first threaded connection; and a second bone engaging portion and a second threaded connection threadably connectable with the first threaded connection. and a threaded connection between the first threaded joint and the second threaded joint to connect the first fixture and the second fixture. A bone fixation system comprising:
The first fixture further comprises a first engagement coupling,
The second fixture is a second engagement coupling that can be engaged with the first engagement coupling portion in a manner that allows relative spiral movement when the depth of the threaded coupling increases or decreases. further comprising the
The threaded connection between the first threaded connection and the second threaded connection causes the first fastener and the second fastener to engage each other in a predetermined axial holding position of the threaded connection. While being held, when the first fixture and the second fixture are in the holding position, the first engagement coupling portion and the second engagement coupling portion correspond to the holding position. When they are engaged with each other at a predetermined engagement position, a locking force generated at the engagement position provides a holding force between the first fixture and the second fixture at the holding position. configured to
The first engagement joint and the second engagement joint are a plurality of fasteners between the first fixture and the second fixture arranged along the direction of the relative spiral motion. At the plurality of engagement positions respectively corresponding to the holding positions, the first fixture and the second fixture can be mutually engaged and coupled in such a manner that a holding force is generated between the first fixture and the second fixture at the holding positions. and relatively move between the plurality of engagement positions while engaging and disengaging with the relative spiral movement ,
the first threaded joint and the first engagement joint are arranged in sequence in the axial direction of the threaded joint;
the second threaded coupling portion and the second engagement coupling portion are arranged in the axial direction in an order corresponding to the arrangement order of the first threaded coupling portion and the first engagement coupling portion;
The first engagement coupling portion and the second engagement coupling portion are configured to be engaged and coupled in the axial direction of the screw coupling at the engagement position, and to allow the relative spiral movement. , having a configuration capable of engaging and disengaging the engagement coupling mode in the axial direction,
Either the first engagement coupling portion and the second engagement coupling portion are rotatable about the axis of the screw coupling, or the first engagement coupling is attached to the first fixture. is fixed in the axial direction and rotatable around the axis, or the second engaging coupling part is fixed in the axial direction and around the axis in the second fixture. can be rotated to
Bone fixation system. The first engagement coupling portion and the second engagement coupling portion have elastic engagement ends provided on at least one of the first engagement coupling portion and the second engagement coupling portion. configured to be engaged and coupled by an elastic engagement structure,
The bone fixation system according to claim 1. said first fastener having a first end and an end opposite said first end having said first bone engaging portion;
said second fastener having a second end and an end opposite said second end having said second bone engaging portion;
The first fixture and the second fixture can be connected by mutually connecting the first end and the second end in a posture facing each other in the axial direction of the screw connection. consists of
3. The bone fixation system according to claim 1 or 2. the first threaded connection comprises external threads;
the second threaded coupling portion includes a female thread that can be threadedly coupled to the male thread;
The first engaging coupling portion is provided on the first end side of the first screw coupling portion,
The second engagement coupling portion is provided on the side opposite to the second end side of the second screw coupling portion,
the outer diameter of the first engagement coupling is smaller than the inner diameter of the second threaded coupling;
The bone fixation system according to claim 3 . the first threaded connection comprises external threads;
the second threaded coupling portion includes a female thread that can be threadedly coupled to the male thread;
The first engaging coupling portion is provided on the first end side of the first screw coupling portion,
The second engagement coupling portion is provided on the side opposite to the second end side of the second screw coupling portion,
the outer diameter of the first engagement coupling portion is smaller than the outer diameter of the first threaded coupling portion;
The bone fixation system according to claim 3 . the first fixture is longer in the axial direction than the second fixture;
Bone fixation system according to claim 4 or 5 . When the first fixture and the second fixture are connected, the depth of the screw connection between the first screw connection portion and the second screw connection portion is increased. In the process of moving, after the screw connection is started, the engagement connection between the first engagement connection portion and the second engagement connection portion is started,
Bone anchoring system according to any one of claims 1-6 . In one of the first engagement coupling portion and the second engagement coupling portion, a plurality of annular portions around the axis provided at the engagement position are arranged in the axial direction. and the other engaging coupling portion includes an engaging end portion engageable with the annular portion in the axial direction,
Bone anchoring system according to any one of claims 1-7 . The annular portion is an annular groove, and the engagement end portion is an elastic engagement structure having an elastic engagement end engageable with the annular groove.
Bone fixation system according to claim 8 . The elastic engagement structure is composed of a ring-shaped elastic body, and is composed of an elastic engagement body having a plurality of the elastic engagement ends divided around an axis.
Bone anchoring system according to claim 2 or 9 . a holding force at the holding position based on a locking force of the engagement joint at the engagement position between the first engagement joint and the second engagement joint, the relative helical movement The retaining force resisting movement in the direction of increasing the depth of the threaded connection is said retaining force resisting movement in the direction of the relative helical movement in the direction of decreasing the depth of the threaded connection. less than force
Bone anchoring system according to any one of claims 1-10 . It is configured to be connectable in a state of rotational engagement with one of the first fixture and the second fixture, and the one fixture is rotated around the axis of the screw connection. further equipped with tools for
In a state where the tool is connected to the one fixture, the tool abuts against the end of the other fixture that moves along the axis through the interior of the one fixture according to the depth of the threaded connection. a detection shaft having a possible tip, and a display for displaying the position of the end of the other fixture according to the position of the detection shaft,
Bone fixation system according to any one of claims 1-11 . In the display unit, the presence or absence of the engagement connection can be confirmed by the position of the detection shaft that interlocks with the end of the other fixture.
13. The bone fixation system according to claim 12 .

Images