Rear insertion type offset nail

Abstract

To solve the problem that, when anatomically fixing and intramedullary nail in femoral neck fracture (fracture from a neck to a stem), there is the risk of fixing force reduction, pain or delay of rehabilitation and a breakdown of the fixture since a tip of an inner fixture member 10 cannot be inserted to a bone head center 23 which is distributed unevenly behind a femoral neck.SOLUTION: There is a through hole having an offset structure, which corrects a displacement between a central axis of a femoral neck and a central axis of a femoral stem, and a forward twisting angle at which a tip of an inner fixture member can be inserted to a bone head center which is distributed unevenly behind the femoral neck in a view from a side face. Most effects can be obtained in an intramedullary nail having a forward curved structure.SELECTED DRAWING: Figure 13

Description

Detailed Description of the Invention [Technical field]

[0001] The present disclosure relates to an internal fixation device for fixation of bone fractures in the field of orthopedic surgery, and in particular to an internal fixation device for femoral neck to shaft fractures. [Background technology]

[0002] As shown in Figure 1, in a femoral neck fracture, the femur 1 is divided into a femoral head 4 side and a femoral shaft 5 side by a fractured portion 3 of the femoral neck 2, and the greater trochanter 6 and lesser trochanter 7 are located on the femoral shaft 5 side. As shown in Figures 2 to 4, a conventional internal fracture fixation device 8 for femoral neck fractures has an intramedullary nail 9 that is placed in the medullary cavity of the femoral shaft 5, and an internal fixation member 10 such as a lag screw that connects the femoral head 4 and the femoral shaft 5. The internal fixation member 10 is inserted into the through hole 11 of the intramedullary nail 9 from the tip side, the tip side is fixed in the femoral head 4, and the rear end side is supported by the through hole 11. In addition, the femur 1 is anatomically lordotic (convex forward when viewed from the side) as shown in Fig. 5, and a corresponding lordotic intramedullary nail 9 is provided. This is advantageous for anatomical reduction. Also, from an anatomical perspective, in the case of Japanese people, the femoral neck 2 is turned forward by an average of 15 degrees when viewed from above compared to the reference line, so the average value of angle 26 is 15 degrees (Figure 6). Correspondingly, the through hole 11 of the intramedullary nail 9 is provided with a 15 degree anteversion (FIG. 7). This allows the internal fixation member 10 to be inserted in the four directions of the femoral head with a 15 degree anteversion. In addition, the internal fixation member 10 (Figure 8) has a groove 12 carved into it to prevent the internal fixation member 10 from rotating relative to the intramedullary nail 9, and a structure 14 such as a screw that can be fixed to the body of the intramedullary nail 11 with a protrusion 13 and whose tip can enter the groove is attached (Figure 9).The internal fixation member 10 does not rotate relative to the intramedullary nail 9, but has an anti-rotation structure that allows it to slide in the long axis direction.

[0003] Furthermore, in 2016, we added an offset structure to the above-mentioned technology to create an offset nail (Patent Document 1). This is the following structure. The horizontal line is indicated by horizontal line 15. As shown in Figure 10-A, when viewed from the cross section where the internal fixation member 10 is inserted, a deviation 19 of about 4 mm occurs between the central axis 17 of the femoral neck and the central axis 18 of the intramedullary nail 9. This is due to the anatomical characteristics of the same area. For this reason, as shown in Fig. 10-B, the internal fixation member 10 enters from the rear of the narrow femoral neck 2, and pushes the rear wall of the bone fragment on the femoral neck side (the femoral head side) backward as shown by the arrow 20, causing the bone on the femoral head side to shift backward as shown by the arrow 21 (Fig. 10-C). This backward shift on the femoral head side is called the intramedullary type, and the outcome is poor. Furthermore, if the bone fragment on the femoral head 4 side was rotated clockwise as shown by the arrow in Fig. 10-D, the tip of the internal fixation member 10 could have been fixed to the femoral head center 23, but the fracture would have become intramedullary type, and the reduction would have been even more rotated than normal. To solve this problem, an intramedullary nail (offset nail 16) was created with a forward convex offset structure 22 (Fig. 11) that shifts the through hole 11 toward the neck center axis 17 relative to the vertical axis of the intramedullary nail 9. In the case of this offset nail 16, the internal fixation member 10 such as a lag screw can be fixed closer to the central axis 17 (dashed line) of the neck compared to one without the offset structure 22 (FIG. 10-E). This prevented the bone fragment on the femoral neck side, which is the femoral head side, from being pushed backward, which prevented the occurrence of the intramedullary type, which was previously seen as a cause of poor results. In this way, we added technology (5) to the internal fixation devices that already existed as conventional technology and that were equipped with any of (1) to (4).

[0004] To summarize the history, in conventional techniques ▲1▼ to ▲4▼, a curved intramedullary nail 9 was inserted into the femur 1, and then an internal fixation member 10 was inserted into the femoral head 4 via a through hole 11. In those days, there was no concept that the intramedullary type had poor results, so the proximal bone fragment on the femoral head 4 side did not need to be prevented from shifting backward relative to the distal bone fragment on the femoral shaft side, and fixation with some deviation was tolerated. Therefore, when inserting the internal fixation member 10 with a 15-degree anteversion, it was possible to insert it on the side of the neck central axis 17, or to rotate the proximal bone fragment on the femoral head 4 side as shown by the arrow to aim at the femoral head center 23. However, in recent years, it has been found that the intramedullary type has poor postoperative results, and we came up with the offset nail 16 in 2016. This allowed the position of the through hole 11 of the intramedullary nail 9 to be moved further forward, preventing the posterior wall from being pressed, suppressing the occurrence of intramedullary type, and enabling reduction and fixation without posterior displacement (Figure 15-C, Patent Document 1). Summary of the Invention Problems with the prior art

[0005] However, such internal fixation devices with functions (1) to (5) have the following problems. In actual anatomy, the femoral head center 23 seen from the side is located eccentrically to the rear of the neck (Fig. 10-A). This recognition and clinical significance are as follows, but have not been fully recognized and have not been reflected in the intramedullary nail structure of claims (1) to (5). In other words, when the central axis 17 of the neck is taken as the boundary as shown in Fig. 10-A, the rear component 25 is larger than the anterior component 24. In other words, the femoral head center 23 (in this case, the femoral head center means the distance between the anterior component 24 and the rear component 25, which are the same and directly below the cartilage of the femoral head, where the tip of the internal fixation member 10 is the fixation position) is located eccentrically to the rear of the neck. The definition of the anteversion angle is vague, but it is generally the angle 26 between the center line of the neck and the horizontal or reference line as shown in Fig. 6, and the average for Japanese people is 15 degrees. In other words, in the conventional technology, assuming that a nail is inserted into a human body, the through hole 11 is provided with a 15-degree anteversion so that the internal fixation member 10 can be fixed with a 15-degree anteversion (Fig. 7). However, it is difficult to insert the tip of the internal fixation member 10 into the femoral head center 23, which is offset backward when viewed from the side, and although it is along the neck center axis 17 as shown in Fig. 10-A, it is inserted offset forward when viewed from the femoral head (this is when there is an offset structure. If there is no offset structure, when the fracture is anatomically reduced, the internal fixation member 10 cannot be inserted into the femoral head center 23 in the first place. It is possible if the reduction is an intramedullary type with offset fixation and rotation (Fig. 10-D)). In this case, even with an offset nail 16, it seems possible to insert the tip of the internal fixation member 10 into the femoral head center 23 by rotating the intramedullary nail 9, but with an intramedullary nail with an anteversion, the intramedullary nail 9 fits into the medullary cavity two-dimensionally or three-dimensionally, so it is impossible to rotate it. In other words, insertion of the tip of the internal fixation part 10 into the center of the femoral head 23 in a through hole 11 with a 15 degree anteversion was possible in the situation shown in Fig. 10-D where the fracture was reduced to a position deviated from the anatomy, but was difficult when the reduction was neatly performed according to the anatomy (Fig. 10-E). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent 6204638

[0007] In consideration of these problems, the present invention aims to provide an internal fixation device for a fracture that satisfies the conventional offset nail requirements (1) to (5) and allows the tip of an internal fixation member 10 such as a lag screw to be inserted into the femoral head center 23 located eccentrically at the rear of the neck (Fig. 10-F). In other words, the present invention adds the function of fixing to the femoral head center. Means to solve the problem

[0008] In FIG. 10-E, the angle between the reference line (horizontal line) 15 and the femoral head center 23 is 3 degrees. In this case, if the anteversion of the through hole 11 is 3 degrees, the offset nail 16 can prevent intramedullary type and insert the tip of the internal fixation member 10 into the femoral head center 23 (FIG. 10-F). In other words, the anteversion angle must be 3 degrees, not 15 degrees, when using an offset nail. This is the solution we present. In general, the femoral head center is 3-13 degrees posterior to the neck center axis 17, so this problem can be solved if the intramedullary nail 9 can insert the internal fixation member 10 in this direction. To achieve this, it is necessary to have a through hole 11 with an anteversion angle that allows the internal fixation member 10 to be inserted in a direction 3-13 degrees posterior from the intramedullary nail 9 with respect to the neck center axis (the claim states an anteversion of 0-14 degrees or 1-15 degrees posterior, but in actual surgery, 3-13 degrees posterior is optimal). In conventional terms, in the case of Fig. 10-F, the anteversion angle of the through hole is not 15 degrees as in the conventional technology, and in the case of the offset nail 16, the anteversion angle of the through hole 11 must be 3 degrees in order to capture the femoral head center 23. The anteversion angle is shown in Fig. 6, but since the definition is not clear, we have created items with different expressions as in claims 6 and 7. It states the same thing in the sense that the offset nail 16 has a through hole 11 with an anteversion angle shallower than the conventional 15 degrees so that the tip of the internal fixation member 10 can be inserted into the femoral head center 23 located eccentrically behind the neck central axis 17 in Fig. 10-A. As mentioned above, the definition of anteversion is vague, so in [Claim 7] it is defined as follows. The anterior wall of the femoral neck has a straight portion 27 that can be assumed to be parallel to the central axis of the neck. The angle made by this straight portion 27 of the anterior wall of the femoral neck and the horizontal line when lying in a supine position is defined as anteversion angle α28. The angle of through hole 11 is set to an angle that opens 1-15 degrees backward from this α (Figure 12). In other words, the anteversion angle set for through hole 11 is set to an angle that is 1-15 degrees less than anteversion angle α (this corresponds to the anteversion angle of 0-14 degrees in claim 1). In terms of novelty, the inclination of the through hole 11 is 3 degrees, as measured in FIG. 10-F. In other words, it is considerably shallower than the conventional 15 degrees, and is a novel angle that could not be achieved with conventional technology.

[0009] With this configuration, the tip of the internal fixation member 10 can be placed at the femoral head center 23 when viewed from the side, and the anterior component 24 and the posterior component 25 can be made equal, so that the load from the pelvis can be supported in a balanced manner. In addition, the risk of the femoral head being torn apart by the tip can be reduced (FIG. 15D).

[0010] The internal fracture fixation device according to at least some embodiments of the present invention basically comprises the structures (1) to (6) of claims (1) an internal fracture fixation device for treating a fracture from the femoral neck to the shaft, 2) an intramedullary nail, 3) an internal fixation member fitted into a through hole and supported by the intramedullary nail, 4) an anti-rotation structure, 5) an offset structure, and 6) an anteversion angle of the through hole of 1 to 14 degrees (although some of these are omitted depending on the embodiment). In particular, it is characterized in that the anteversion angle of the through hole is specified compared to the conventional technology.

[0011] According to this configuration, it is possible to suppress the intramedullary type in the offset nail when viewed from the side (after reducing it to the original anatomical state), and then insert the tip of the internal fixation member into the center of the femoral head when viewed from the side. This allows for a more balanced support of the load from the pelvis. The fixation force is also stronger, and since the tip of the internal fixation member (lag screw, etc.) can at least partially capture the center of the femoral head when viewed from the side, the connection with the femur is stronger than in the conventional type where the tip is offset from the femoral head and cannot do so, and the risk of the internal fixation member cutting through the femoral head is reduced. [Brief description of the drawings]

[0012] [Figure 1] Perspective view showing femoral neck fracture [Diagram 2] FIG. 1 is a perspective view showing a conventional internal fixation device for femoral neck fractures; [Diagram 3] A side view of an intramedullary nail according to the prior art [Figure 4] FIG. 1 is a perspective view showing a state in which a conventional internal fixation device for femoral neck fracture is used; [Diagram 5] FIG. 1 is a cross-sectional view showing a prior art intramedullary nail with a lordotic curve. [Figure 6] FIG. 1 is an explanatory diagram of anterior twist according to the prior art. [Figure 7] FIG. 1 shows an anteversion of a through hole according to the prior art [Figure 8] FIG. 1 shows a groove in an internal fixing member according to a conventional technique. [Figure 9] FIG. 1 shows a conventional anti-rotation structure. [Figure 10] Side views showing the relationship between reduction and internal fixation members according to the conventional and new techniques. [Figure 11] FIG. 1 shows an offset nail according to the prior art. [Figure 12] FIG. 1 is a diagram illustrating an anterior torsion angle according to the prior art. [Figure 13] FIG. 1 is an explanatory diagram of an intramedullary nail according to a first embodiment. [Figure 14] FIG. 3 is an explanatory diagram of an intramedullary nail according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] First Embodiment 13 shows an intramedullary nail 9 portion of the fracture internal fixation device for treating a femoral neck to shaft fracture according to the first embodiment. It satisfies the conditions (1) to (6) of claim 1, but the anteversion angle 26 of the through hole is 0-14 degrees.

[0015] The procedure for attaching the internal fixation device for fracture bone will be described below. First, the intramedullary nail 9 is inserted into the medullary cavity of the femoral shaft 5. The internal fixation member 10 is inserted through the through hole 11. This causes the tip of the internal fixation member 10 to be fastened to the femoral head center 23 when viewed from the side. In this manner, the internal fixation device for fracture bone is attached to the fractured portion 3.

[0016] In the fracture internal fixation device according to the first embodiment, since the through hole 11 is offset, the internal fixation member 10 can be inserted without pushing the proximal bone fragment including the femoral head 4 backward (without causing intramedullary mold), and since the through hole 11 is anteversion of 0-14 degrees as stated in claim 1, the tip of the internal fixation member 10 can be fixed to the femoral head center 23, which is biased toward the rear in the human body when viewed from the side. This improves the load balance and increases the fixation force. In addition, the pain of the fractured part 3 can be reduced compared to conventional devices, and since it is advantageous for early loading, rehabilitation can be advanced earlier than conventional devices. It can also reduce the risk of the femoral head 4 being torn apart.

[0017] <Second embodiment> The internal fixation device for fracture according to the second embodiment is defined as claim 2. That is, the offset structure 22 is not provided.

[0018] Since there is no offset structure 22, the internal fixation member enters the neck from the rear, which is a disadvantage. However, compared to existing technologies, it has the advantage that it is easier to aim at the femoral head center 23 without having to rotate the femoral head bone fragment on the side as shown in Figure 10-D.

[0019] This increases the fixing force and pull-out resistance between the tip of the internal fixation member 10 and the femoral head 4, and also reduces the risk of the femoral head 4 being torn apart.

[0020] <Third embodiment> Fig. 14 shows an internal fixation device for a bone fracture according to the third embodiment. This embodiment is defined as claim 5. In other words, there is no anti-rotation structure (4). However, when there are multiple internal fixation members 29 to be inserted into the femoral head as shown in Fig. 14, rotation between the internal fixation members and the intramedullary nail 9 is naturally prevented, so there is no need for an anti-rotation structure.

[0021] The fixing force and pull-out resistance between the internal fixation member and the femoral head 4 side and the femoral shaft 5 side are increased, and the load distribution range from the femoral head 4 to the tip of the internal fixation member 29 can be expanded. [Industrial Applicability]

[0022] It can be used primarily for femoral neck to shaft fractures in the field of orthopedic surgery. [Explanation of symbols]

[0023] 1:Femur 2: Femoral neck 3: Fractured part 4: Femoral head 5:Femoral shaft 6: Greater trochanter 7: Lesser trochanter 8:Fracture internal fixation device 9: Intramedullary nail 10: Internal fixing member 11:Through hole 12: Groove 13: Protrusion 14: Structure 15: Reference line 16: Offset Nail 17: Central axis 18: Central axis 19: Displacement 20: Arrow 21: Arrow 22: Offset structure 23: Center of the femoral head 24: Front component 25: Rear component 26: Angle 27: Straight part 28: Forward twist angle α 29: Internal fixation member

Claims

1. (1) It is an internal fixation device for treating fractures from the femoral neck to the shaft. (2) It is an intramedullary nail that is to be placed in the medullary cavity of the femoral shaft, and is made two-dimensionally or three-dimensionally so as to have a lordosis corresponding to the anatomical lordosis of the femur, with a through hole at the top. (3) It has a rod-shaped internal fixation member that is fitted into the through hole and supported by the intramedullary nail, and has a shaft portion to be inserted into the femoral neck, and a tip portion to be inserted into the femoral head. (4) It has a rotation prevention structure. That is, the internal fixation member has a rotation prevention groove carved in it, and the internal fixation member slides in the longitudinal direction by entering the groove, but a protrusion that can prevent the internal fixation member from rotating relative to the intramedullary nail can be connected to the intramedullary nail with a screw or the like. (5) It has a forward offset structure in which the central axis of the extension direction of the tip portion is offset from the central axis of the intramedullary nail in a direction approaching the central axis of the femoral neck. (6) When the internal fixation member is inserted into the through hole of the intramedullary nail, the through hole has an anterior torsion angle of 0 to 14 degrees so that the tip of the internal fixation member is directed to the center of the femoral head, which is eccentrically located posteriorly.

2. The above item 1 does not have the offset structure of (5).

3. The above 1 does not have the fore bay of ▲2▼.

4. The above 1 does not have the forebay (2) and offset structure (5).

5. The above 1-4 does not have the anti-rotation groove of ▲4▼.

6. The anterior torsion angle of the through hole 6 in 1-5 above is structured to be 1 to 15 degrees less than the average value of the anteversion angle of the anatomical femoral neck in each race or target group using this intramedullary nail.

7. In the above 1-5, the portion of the through hole (6) corresponding to the anteversion angle is configured to be anteversion such that the through hole (6) faces backward by 1 to 15 degrees compared to the straight portion of the anterior wall of the femoral neck in the cross section where the internal fixation member is inserted.

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