Intramedullary nailing

Abstract

To provide an intramedullary nail capable of suppressing failure following steps of therapy with respect to bone fracture on a position on a femur proximal side, capable of being arranged at an ideal position in a femur for connecting bone pieces and firmly fixing the bone pieces.SOLUTION: There is provided an intramedullary nail 1 being one embodiment of the intramedullary nail of the invention is a member which is combined with a lag screw 2, a sub pin 3, a locking screw 4, a locking screw 5, a set screw and an end cap in use. Each member is a member forming a bone junction tool A. The intramedullary nail 1 is configured so that, in a direction viewing a distal side from a proximal side along a longitudinal direction of a femur, and in a view point viewing from a direction where a rear condyle is provided on a lower side, (confronting state), a bending direction of a curved part 110 of a shaft part 11 is an angle which is externally rotated by 5° according to an externally curved shape of the femur F.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present invention relates to an intramedullary nail, and more particularly to an intramedullary nail that can prevent problems during the surgical procedure for fractures at the proximal side of the femur, and can be placed at an ideal position in the femur to connect and firmly fix bone fragments. [Background technology]

[0002] Conventionally, in the field of fracture treatment requiring surgical operation, a bone setting device has been used that combines an intramedullary nail, which is inserted along the longitudinal axis of the bone to be treated, with a lag screw that has a male thread formed around the shaft, and is particularly used in bone setting surgery for fractures on the proximal side of the femur.

[0003] Many different forms of intramedullary nails used in such bone fixation procedures have been known in the art. For example, an intramedullary nail that is driven into the femur from the proximal end has been proposed to repair trochanteric fractures, subtrochanteric fractures, intertrochanteric fractures, or femoral neck fractures (see, for example, Patent Document 1).

[0004] In addition, in a procedure using an intramedullary nail that is driven into the femur from the proximal end, a hole is drilled in the femur from the proximal side to the distal side with a reamer, and the intramedullary nail is inserted into the hole.

[0005] In addition, a lag screw is inserted through a screw hole formed in the proximal portion of the intramedullary nail, and its tip is positioned near the center of the femoral head.

[0006] The inserted lag screw is pressed and fixed via a set screw attached to the top of the intramedullary nail. In this way, the bone fragments at the fractured site can be connected and firmly fixed via the intramedullary nail and lag screw. Also, by positioning the tip of the lag screw within the femoral head, it is possible to apply appropriate pressure to the fractured site and promote bone union.

[0007] In addition, for conventional intramedullary nails, a structure has been proposed in which the direction of the screw hole for inserting the lag screw is set to correspond to the anteversion angle, which is the angle at which the neck of the femur is tilted forward, in order to improve compatibility with the femur.

[0008] Here, the "anteversion angle" is the angle θ between the femoral neck axis S1, which is the axis connecting the center of the head F1 of the femur F and the center of the neck F2 (the position equidistant to the outer edge), and the femoral condyle axis S2, which is the axis connecting the medial condyle F3 and the lateral condyle F4 (posterior condyles) at the distal part of the femur F, as shown in Figure 1(a).

[0009] Figure 1(a) is a view of the right femur from the proximal side to the distal side, showing the structure of the femoral head and its surrounding area. Also, the symbol H in Figure 1(a) indicates the hip joint.

[0010] Although there are individual differences, this anteversion angle is generally a shape in which the neck of the femur is tilted forward (tilted to the upper left as seen in FIG. 1(a)), that is, an angle in which the femoral neck axis S1 opens forward relative to the femoral condyle axis S2. Note that, depending on the individual, the neck of the femur may also be tilted backward (retroversion angle).

[0011] Because the femoral head is also tilted forward due to the inclination of the anteversion angle, conventional intramedullary nails have been designed with the screw hole direction determined in advance based on the inclination of the anteversion angle. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Special table 2017-535401 Summary of the Invention [Problem to be solved by the invention]

[0013] Here, in bone setting procedures using conventional intramedullary nails, including intramedullary nails in which screw holes are formed taking into account the inclination of the anteversion angle, the following problems arise.

[0014] First, as a premise, when viewed from the side, the shape of the femur is such that, as shown in Figure 2(a), the shaft F5 located between the proximal and distal femur has a curved shape (symbol C1, hereinafter referred to as the "lordotic shape") with the apex P of the curve on the anterior side.

[0015] Here, Fig. 2(a) shows the shape of the right femur in a composition (side view) in which the right femur is viewed from the inside to the outside of the human body along the coronal plane of the human body, and Fig. 2(b) shows the shape of the right femur in a composition (front view) in which the right femur is viewed from the front to the rear of the human body along the sagittal plane of the human body.

[0016] FIG. 1(b) illustrates a coronal plane K1, a sagittal plane K2, and a transverse plane K3, which are planes that cross the human body. Here, the coronal plane K1 is a plane that divides the body into front and back. The sagittal plane K2 is a plane that passes through the body from front to back and divides it into left and right, or a plane parallel to this. The transverse plane K3 is a plane that divides the body into top and bottom. In this specification, when specifying a direction, the terms coronal plane, sagittal plane, and transverse plane, or the direction along these planes may be used as necessary.

[0017] Figures 2(a) and 2(b) also show the medullary cavity center M extending along the longitudinal direction inside the femur, the positions M1 of both ends of the medullary cavity center, and a position M2 in the medullary cavity center that corresponds to the apex P of the lordotic shape (the position in the medullary cavity center that is the apex of the curve).

[0018] Generally, this lordotic shape is a shape of the femur bent in a range from a position just below the lesser trochanter (position indicated by reference character L1 in FIG. 2(b)) to a position just above the patella Q (position indicated by reference character L2 in FIG. 2(b)) (see FIG. 2(b)). In this specification, the "lordotic shape" of the femur does not refer to the bending of the entire length of the femur, but refers to the bending in the range from the position just below the lesser trochanter to a position just above the patella Q, which is the range that should be secured by the intramedullary nail.

[0019] Furthermore, as shown in FIG. 3, in the femur, in a frontal view seen from the proximal side to the distal side along the longitudinal direction of the femur and from the direction in which the posterior condyle is located downward (hereinafter, the perspective seen from the same direction will be referred to as the "frontal view"), the direction of curvature in the above-mentioned lordotic shape is inclined with respect to reference line B, which is a line that is approximately perpendicular to reference line A connecting the posterior condyles (medial condyle F3 and lateral condyle F4) and passes through position M1 at both ends of the center of the medullary cavity (indicated by symbol C2 in FIG. 3, the lateral curvature shape described below).

[0020] More specifically, in a frontal view of Figure 3, the inclination of the direction of curvature in the lordotic shape relative to the reference line B is represented by the angle θ between the reference line C connecting positions M1 at both ends of the center of the spinal cavity and position M2 in the center of the spinal cavity corresponding to the apex P of the lordotic shape, and the reference line B.

[0021] The reference line A shown in Fig. 3 is a line located on the reference plane X, which is a plane on which the posterior condyles of the femur (medial condyle F3 and lateral condyle F4) and the posterior edge F6 of the greater trochanter of the femur (posterior side of the greater trochanter) are located in the same plane, as shown in Fig. 4(a). The reference line A is a line corresponding to the femoral condyle axis S2 described above. The femur shown in Fig. 3 is a left femur.

[0022] Figure 4(b) is a diagram showing the position of the posterior condyles (medial condyle F3 and lateral condyle F4) and the position of the posterior edge F6 of the greater trochanter of the femur when viewed from the outside to the inside of the body along the coronal plane of the human body, and Figure 4(c) is a diagram showing the position of the posterior condyles (medial condyle F3 and lateral condyle F4) when viewed from the distal side to the proximal side along the longitudinal direction of the left femur.

[0023] Generally, in the shape of the femur, when viewed from the front as shown in Fig. 3, the direction of curvature in the lordotic shape does not often coincide with reference line B. That is, the direction of curvature in the lordotic shape is not located in a direction approximately perpendicular to reference line A (the 12 o'clock direction in Fig. 3), and the shape is tilted either outward or inward when viewed from reference line B (a shape tilted in the clockwise or counterclockwise direction in Fig. 3).

[0024] When viewed from the front, with regard to the inclination of the direction of curvature in the lordotic shape relative to the reference line B, as shown in Figure 3, a shape in which the direction of curvature in the lordotic shape is inclined outward when viewed from the reference line B (a shape inclined in the counterclockwise direction in Figure 3) is called an "external curvature shape."

[0025] Also, unlike Fig. 3, when viewed from the front, the direction of curvature in the lordotic shape with respect to the reference line B is tilted inward when viewed from the reference line B (a shape tilted in a clockwise direction in Fig. 3) and is referred to as an "internal curvature shape." Note that "internal / external" here refers to the direction along the coronal plane of the human body.

[0026] FIG. 5 also shows, as an example of an internal curve shape, a reference plane X on which the posterior condyles (medial condyle F3 and lateral condyle F4) of the right femur and the posterior edge F6 of the greater trochanter of the femur are located on the same plane, and an inclined plane Y which indicates a state in which the direction of curvature in the lordotic shape is inclined inward when viewed from the reference line B.

[0027] As shown in FIG. 5, the inclined surface Y is a surface that is inclined with respect to the reference surface X, and the direction of curvature in the lordotic shape is inclined obliquely.

[0028] Thus, the shape of the femur is often characterized by an inclination of the direction of curvature in the lordotic shape relative to the reference line B, which is an outward curve or an inward curve.

[0029] As described above, the shape of the femur has a lordotic shape when viewed from the side. Also, when viewed from the front, the shape is often an outward curve due to the inclination of the direction of curvature in the lordotic shape with respect to the reference line B, and depending on the person, it may be an inward curve (hereinafter, simply referred to as an "outward curve" and an "inward curve").

[0030] Given this shape of the femur, conventional intramedullary nails are not shaped to correspond to the external or internal curvature of the femur.

[0031] That is, a conventional intramedullary nail 300 in which a screw hole is formed taking into consideration the inclination of the anteversion angle has a shape as shown in, for example, Figs. 6(a) to 6(e).

[0032] 6(a) and 6(b) show the shape of the intramedullary nail 300 as viewed from the front (as viewed from the front to the rear when inserted into the femur). Reference numeral 300a denotes a shaft. FIG. 6(b) also shows a lag screw 301 and a locking screw 302 that are used in combination with the intramedullary nail 300.

[0033] Fig. 6(c) shows the shape of the intramedullary nail 300 when viewed from the side (when inserted into the femur, viewed from the medial-lateral direction along the coronal plane of the human body), Fig. 6(d) shows the shape of the intramedullary nail 300 when viewed from the front (when inserted into the femur, viewed from the proximal side to the distal side), and Fig. 6(e) shows an image of the intramedullary nail 300 inserted straight in the longitudinal direction of the femur (when viewed from the front).

[0034] As shown in Figs. 6(a) and 6(b), the shaft 300a of this intramedullary nail 300 has a shape that extends straight along the vertical direction in the figures.

[0035] 6(c), in the shape of the intramedullary nail 300 viewed from the side, a curved portion is formed in the shaft 300a. This curved portion is shaped to adapt the shape of the shaft 300a of the intramedullary nail 300 to the lordotic shape of the femur described above, and when inserted into the femur, it becomes a portion curved from the front to the back along the sagittal plane of the human body.

[0036] Also, as shown in FIG. 6(d), in the intramedullary nail 300, when viewed from the front, the direction of the screw hole for inserting the lag screw 301 is formed at an angle indicated by the symbol θ1, taking into account the inclination of the anteversion angle.

[0037] Here, the intramedullary nail 300 has a curved portion formed in the shaft 300a in accordance with the lordotic shape of the femur, and the direction of curvature of this curved portion is perpendicular (the line marked with the symbol Y1) to the reference line A connecting the posterior condyles (the medial condyle F3 and the lateral condyle F4) when viewed from the front, as shown in Figure 6(e).

[0038] In other words, when the intramedullary nail 300 is inserted straight into the longitudinal direction of a femur having an external curve shape (when the longitudinal direction of the shaft 300a is aligned with the longitudinal direction of the femur), the external curve shape C2 of the femur, i.e., the reference line C, and the bending direction of the curved portion of the shaft 300a (line marked Y1) do not coincide with each other (see FIG. 6(e)).

[0039] In reality, as described later, if the intramedullary nail 300 is inserted straight into a femur having an external curvature, the femoral cortical bone and the intramedullary nail 300 may come into contact during insertion, making it difficult to insert the nail further distally. For this reason, Fig. 6(e) is an image showing the positional relationship assuming that the intramedullary nail 300 has been inserted to a predetermined position (optimum depth) on the distal side.

[0040] In this manner, the direction of curvature of the curved portion of the shaft 300a of the intramedullary nail 300 is different from the direction of curvature of the femur in its lateral curvature shape.

[0041] Therefore, when using the intramedullary nail 300 to perform a procedure on a femur having an externally curved shape, if the tip of the intramedullary nail 300 is inserted from the proximal side to the distal side of the femur (the direction indicated by symbol D in FIG. 7(a)), the tip of the intramedullary nail 300 will come into contact with the cortical bone of the femur midway through the shaft, making insertion difficult, due to the difference in the direction of curvature of the externally curved shape of the femur and the direction of curvature of the curved part of the shaft 300a (see FIG. 7(a)).

[0042] Then, in order to avoid a state in which it becomes difficult to insert the intramedullary nail 300 further, the intramedullary nail 300 is externally rotated (rotated outwardly based on the femur) together with the target device (not shown) supporting the intramedullary nail 300 (rotated in the direction indicated by symbol R1 in FIG. 7(b)) so that the tip of the intramedullary nail 300 does not come into contact with the femoral cortical bone, and is inserted further distally (in the direction indicated by symbol D in FIG. 7(b)).

[0043] The right diagram of FIG. 7(a) and the right diagram of FIG. 7(b) are each a schematic enlarged view showing the positional relationship between the tip of the intramedullary nail 300 and the cortical bone inside the femur.

[0044] Here, when the intramedullary nail 300 is externally rotated and inserted into the distal side of the femur, the direction in which the screw hole for inserting the lag screw 301 is formed also rotates due to the external rotation of the intramedullary nail 300. That is, the direction in which the screw hole is formed at the angle indicated by the symbol θ1 (see FIGS. 6(d) and 6(e)) in consideration of the inclination of the antetorsion angle is inclined further forward.

[0045] As a result, when the lag screw 301 is inserted into the rotated screw hole, the tip of the lag screw 301 is positioned forward of the center of the femoral head F1, as shown in Fig. 8(a). Note that in Fig. 8(a), the arrow marked with the symbol f indicates the direction toward the forward side.

[0046] That is, in consideration of preventing inversion or rotation of the femoral head after surgery via the lag screw 301, it is preferable to position the tip of the lag screw 301 so as to be located near the center of the femoral head F1, but by externally rotating the intramedullary nail 300, the position of the tip of the lag screw 301 shifts forward from the desired position near the center of the femoral head F1. In other words, with the intramedullary nail 300, there was a risk that the lag screw 301 would be placed in an inappropriate position.

[0047] In addition, in order to cope with such a deviation in position where the tip of the lag screw 301 is positioned forward from the vicinity of the center of the femoral head F1, an operation is performed to reduce the position of the tip of the lag screw 301 to the vicinity of the center of the femoral head F1 by compressing the femur from the outside (compressing in the direction indicated by symbol P1 in FIG. 8(b)). This compression forcibly shifts the position of the femoral head F1 forward.

[0048] Furthermore, when the femur was compressed from the outside and the femoral head F1 was forcibly shifted forward, a problem occurred in that the compression caused gaps to appear between the bone fragments to be fixed (see the area indicated by symbol P2 in Figure 8(b)).

[0049] In addition, by applying pressure and shifting the femoral head forward, the shaft of the bone would move back and forth in an attempt to return to its original shape, causing the knee to internally rotate (turn inwards), which could affect walking, resulting in a condition known as hyper-antetorsion.

[0050] In addition, since the intramedullary nail 300 has a screw hole formed at a certain angle in the direction of the screw hole according to the angle of the anteversion angle, the angle is changed by compression from this preset certain angle, and this change in angle can also cause a decrease in the walking ability of the user. Note that Figures 8(a) and 8(b) show the right femur.

[0051] As described above, when used on a femur having an external curvature, conventional intramedullary nails could cause problems during insertion, or the intramedullary nail or lag screw could not be placed in an ideal position within the femur, making it impossible to adequately fix the bone fragments and promote bone union in fractures on the proximal side of the femur.

[0052] The present invention has been devised in consideration of the above points, and has as its object to provide an intramedullary nail that can prevent malfunctions that occur during treatment for fractures at the proximal side of the femur, and that can be positioned in an ideal position within the femur to connect and firmly fix bone fragments. [Means for solving the problem]

[0053] In order to achieve the above object, the intramedullary nail of the present invention is an intramedullary nail that is used when a proximal side of a femur is fractured by being inserted into the femur from the proximal side to reposition and fix each bone fragment, and that includes a tubular main body having a through hole formed therein, constituting one end side of the main body and having a screw hole intersecting the through hole formed therein, a shaft portion connected to the proximal main body portion, constituting an intermediate portion of the main body, and having an outer circumferential diameter smaller than but equal to the outer circumferential diameter of the proximal main body portion and extending toward the other end side of the main body, and a distal main body portion connected to the shaft portion and constituting the other end side of the main body, wherein the shaft portion has a curved portion formed therein that is curved from the front side to the rear side of the femur when viewed along the medial-lateral direction of the femur, and the curved portion is curved in a direction parallel to the longitudinal direction of the femur when the intramedullary nail is inserted into the femur. a first reference line which is a line on a reference plane which is a plane on which the posterior condyles of the femur and the posterior edge of the greater trochanter are located on the same plane when viewed from the proximal side to the distal side and from the direction in which the posterior condyle is located below, and which is a line connecting the two posterior condyles; and a second reference line which is a line which is approximately perpendicular to the first reference line when viewed from the front and which passes through a first axis which is the axis of the one end side of the shaft portion, and a first curve corresponding line which is a line connecting the first axis on the second reference line and an apex of the curved portion when viewed from the front, the first angle is an angle formed by the second reference line and the first curve corresponding line when viewed from the front, when the apex of the curved portion is located in the medial direction when viewed from the second reference line, the first angle is a predetermined internal curve angle, or when the apex of the curved portion is located in the outward direction when viewed from the second reference line, the first angle is a predetermined external curve angle.

[0054] The terms "front, back, inside, and outside" are all terms defined in terms of directions along a plane that crosses the human body. That is, the front-back direction is a direction along the sagittal plane, which is one of the planes that cross the human body, and the inside-out direction is a direction along the coronal plane, which is one of the planes that cross the human body. In addition, in the direction along the sagittal plane, the front side as seen from the human body is referred to as "front or anterior" and the rear side as seen from the human body is referred to as "rear or posterior". In addition, in the direction along the coronal plane, the direction toward the center of the human body is referred to as "inner or medial" and the direction away from the center of the human body is referred to as "outer or lateral". In addition, in the terms "proximal, distal" here, the direction closer to the center of the human body in the longitudinal direction of the bone is referred to as "proximal" and the direction away from the center of the human body is referred to as "distal".

[0055] Here, by forming a curved portion in the shaft portion that curves from the front side to the rear side of the femur when viewed from the medial-lateral direction of the femur, it becomes easier to make the shape of the shaft portion conform to the lordotic shape of the femur seen in a lateral view of the femur when the intramedullary nail is placed at a desired position inside the femur. Note that the "lordotic shape" of the femur here refers to a shape in which the diaphysis curves forward with the apex of the curve on the front side when the femur is viewed from the side in the medial-lateral direction along the coronal plane of the human body.

[0056] In addition, regarding the curved portion, when the intramedullary nail is inserted into the femur, a first reference line is a line on a reference plane that is a surface on which the posterior condyles of the femur and the posterior edge of the greater trochanter are located on the same plane when viewed from the front in a direction from the proximal side to the distal side along the longitudinal direction of the femur and from a direction in which the posterior condyle is located below, and is a line connecting the two posterior condyles, and a second reference line is a line that is approximately perpendicular to the first reference line when viewed from the front and passes through the first axis that is the axis of one end of the shaft portion. When the apex of the curved portion is located inwardly as viewed from the second reference line, the first angle is a predetermined inward curve angle, so that the inclination of the bending direction of the curved portion of the shaft portion with respect to the second reference line can be easily adapted to the inward curve shape of the femur. That is, the bending direction of the lordotic shape of the femur is inwardly inclined as viewed from the front with respect to the reference line B, which is a line that is approximately perpendicular to the reference line A connecting the posterior condyles (medial and lateral condyles) of the femur and passes through the positions of both ends of the center of the medullary cavity, as viewed from the front. The bending direction of the curved portion of the shaft portion is inclined in the same direction as the so-called "inward curve shape" in which the bending direction of the lordotic shape of the femur is inclined inwardly as viewed from the reference line B. This allows the intramedullary nail to be placed in an optimal position without any difficulty, even in a femur having an internal curvature. In the following, the "front view seen from the direction from the proximal side to the distal side along the longitudinal direction of the femur and from the direction in which the posterior condyle is located below" will be simply referred to as "front view." Also, the first axis, which is the axis on one end side of the shaft part, means the axis (center of the circular cross section) at the boundary with the one end side of the shaft part formed with the same diameter, that is, the distal part of the main body.

[0057] In addition, regarding the curved portion, when the intramedullary nail is inserted into the femur, a first reference line is a line on a reference plane that is a surface on which the posterior condyles of the femur and the posterior edge of the greater trochanter are located on the same plane when viewed from the front in a direction from the proximal side to the distal side along the longitudinal direction of the femur and from a direction in which the posterior condyle is located below, and is a line connecting the two posterior condyles, and a second reference line is a line that is approximately perpendicular to the first reference line when viewed from the front and passes through the first axis that is the axis of one end of the shaft portion. When the apex of the curved portion is located in the outward direction as viewed from the second reference line, the first angle is a predetermined outward curve angle, so that the inclination of the bending direction of the curved portion of the shaft portion with respect to the second reference line can be easily adapted to the outward curve shape of the femur. That is, the bending direction of the lordotic shape of the femur is inclined outward as viewed from the front with respect to the reference line B, which is a line that is approximately perpendicular to the reference line A connecting the posterior condyles (medial and lateral condyles) of the femur and passes through the positions of both ends of the center of the medullary cavity, and the bending direction of the curved portion of the shaft portion is inclined in the same direction as the so-called "outward curve shape" in which the bending direction of the lordotic shape of the femur is inclined outward as viewed from the reference line B. This allows the intramedullary nail to be placed in an optimal position without any difficulty, even in a femur having an outwardly curved shape.

[0058] Furthermore, when the specified inward curve angle at the first angle is within the range of 1° to 25°, it becomes easier to adapt the bending direction of the curved portion of the shaft portion to the angle of inclination commonly seen in inward curve shapes.

[0059] Furthermore, when the specified outward curve angle at the first angle is within the range of 1° to 25°, it becomes easier to adapt the bending direction of the curved portion of the shaft portion to the angle of inclination commonly seen in outward curve shapes.

[0060] In addition, when the screw hole is inserted into the femur, in the range of the second angle, which is the angle between the first reference line and the direction of the screw hole, in a frontal view, the screw hole is positioned so that the direction of the screw hole is inclined backward with respect to the first reference line. If the second angle is within the range of 0° to 2°, the direction of the screw hole can be adjusted to the shape of the femur in which the so-called posterior torsion angle is inclined backward from the first reference line in the range of 0° to 2°. That is, the lag screw can be easily adapted to the angle of the posterior torsion angle. As a result, even if the neck or head of the femur is inclined backward in a frontal view, the tip of the lag screw can be easily positioned near the center of the head. In addition, by setting the second angle within the range of 0° to 2°, it is easy to adapt to the angle of inclination often seen in the angle of the posterior torsion angle.

[0061] In addition, when the screw hole is inserted into the femur, in the range of the second angle, which is the angle between the first reference line and the direction of the screw hole, in a front view, the screw hole is positioned so that the direction of the screw hole is inclined forward with respect to the first reference line. If the second angle is within the range of 0° to 35°, the direction of the screw hole can be adjusted to the shape of the femur in which the so-called anteversion angle is inclined forward from the first reference line in the range of 0° to 35°. That is, the lag screw can be easily adapted to the angle of the anteversion angle. As a result, even if the neck or head of the femur is inclined forward in a front view, the tip of the lag screw can be easily positioned near the center of the head. In addition, by setting the second angle within the range of 0° to 35°, it is easy to adapt to the angle of inclination often seen in the angle of the anteversion angle.

[0062] Furthermore, when the curved portion is formed to fit the femur curved forward with a radius of curvature within a range of 514 mm to 1358 mm in the range from the position just below the lesser trochanter to the position just above the patella when viewed from the medial-lateral direction of the femur, the shape of the shaft portion can be made to fit the lordotic shape of the femur as seen in a lateral view of the femur more easily. In other words, by setting the curved portion of the shaft portion to the lordotic shape of the femur with a radius of curvature within a range of 514 mm to 1358 mm, the intramedullary nail can be comfortably positioned in an optimal position on the femur.

[0063] In addition, since the main body is formed with a total length in the range of 265 mm to 400 mm and the curved portion is formed in the shaft portion, when the distance from the third reference line, which is a line corresponding to the position of the second axis, which is the axis of the proximal part of the main body, to the center position of the tip of the distal part of the main body is 13 mm or more in a viewpoint along the medial-lateral direction of the femur, the position of the tip of the intramedullary nail can be more easily arranged at an appropriate position inside the femur (femoral medullary cavity) in accordance with the lordotic shape of the femur when the femur is viewed from the side. That is, for example, it is easy to prevent the intramedullary nail from coming into contact with the cortical bone during the insertion of the intramedullary nail into the femur, or the tip of the intramedullary nail from protruding outward from the distal end of the femur when the tip of the intramedullary nail is inserted to a desired position on the distal side of the femur. As a result, the compatibility of the intramedullary nail with the femoral medullary cavity can be improved.

[0064] In addition, when the curved portion is composed of four curved portions, namely, a first bend portion, a second bend portion, a third bend portion, and a fourth bend portion, and when viewed from the perspective along the medial-lateral direction of the femur, the curve start position of the first bend portion is 120 mm from one end of the proximal portion of the main body, and the curvature radius of the range between the curve start position of the first bend portion and the curve start position of the second bend portion is 457 mm, the first bend portion can be adapted to the bone shape of the femur at the start of the curve of the lordotic shape in the process of advancing the tip of the intramedullary nail to an optimal depth beyond the position corresponding to the apex of the lordotic shape in the center of the medullary cavity of the femur. This reduces the contact between the intramedullary nail and the anterior cortical bone in the proximal portion of the femur, and allows the tip of the intramedullary nail to be smoothly inserted toward the distal direction of the femur. It also reduces the risk of fracture in the proximal femur and the risk of preventing the nail from being inserted to the optimal depth, which means the height at which the screw hole can be positioned near the center of the femoral head in the coronal direction.

[0065] In addition, when the curved portion is composed of four bend portions, namely, a first bend portion, a second bend portion, a third bend portion, and a fourth bend portion, and when viewed from the perspective along the medial-lateral direction of the femur, the curve start position of the second bend portion is 150 mm from one end of the proximal portion of the main body, and the curvature radius of the range between the curve start position of the second bend portion and the curve start position of the third bend portion is 475 mm, it becomes easier to form a shape corresponding to the position corresponding to the apex of the lordotic shape at the center of the medullary cavity of the femur. This makes it possible to easily insert the intramedullary nail into the position corresponding to the apex of the lordotic shape at the center of the medullary cavity of the femur and the position in the vicinity thereof. In addition, it becomes easier to adapt the portion beyond the second bend portion to the lordotic shape of the femur, and the intramedullary nail can be placed in an optimal position without difficulty.

[0066] In addition, when the curved portion is composed of four bend portions, namely, a first bend portion, a second bend portion, a third bend portion, and a fourth bend portion, and when viewed from the perspective along the medial-lateral direction of the femur, the curve start position of the third bend portion is 175 mm from one end of the main body proximal portion, and the curvature radius of the range between the curve start position of the third bend portion and the curve start position of the fourth bend portion is 637 mm, the third bend portion is easily shaped to correspond to the position (start point of posterior curvature) where the bone starts to drop from the front side to the rear side in the lordotic shape of the femur. This makes it easier to guide the intramedullary nail to the center of the femoral medullary cavity by avoiding excessive contact between the tip of the intramedullary nail and the anterior cortical bone in the distal part of the femur. In addition, the portion beyond the third bend can be easily adapted to the lordotic shape of the femur, allowing the intramedullary nail to be positioned in an optimal position without any strain.

[0067] In addition, when the curved portion is composed of four bends, namely, a first bend, a second bend, a third bend, and a fourth bend, and when viewed from the inside-outside direction of the femur, the start position of the curve of the fourth bend is 205 mm from one end of the proximal portion of the body, and the radius of curvature of the range between the start position of the curve of the third bend and the start position of the curve of the fourth bend is 637 mm, the fourth bend can prevent the tip of the intramedullary nail from protruding from the anterior cortex in the area distal to the apex of the lordotic shape of the femur, which is a larger curvature range of the lordotic shape, and can insert the intramedullary nail into the center of the femoral medullary cavity. This makes it possible to insert the lag screw into the optimal position in addition to inserting it into the center of the femoral medullary cavity, and to firmly fix the fractured part.

[0068] Further, when viewed from the front and before the start of insertion of the intramedullary nail into the femur, the direction in which the screw holes are formed is approximately parallel to the first reference line, and within a range of a third angle that is an angle formed by the second reference line and a second curve corresponding line that is a line connecting the first axis on the second reference line and the apex of the curved portion, the apex of the curved portion is located in the medial direction as viewed from the second reference line, and the third angle is within a range of 0° to 60°, or the apex of the curved portion is located outward as viewed from the second reference line. When the third angle is in the range of 0° to 27°, the intramedullary nail is inserted into the femur and rotated externally or internally by a predetermined angle during the insertion, so that when the intramedullary nail is placed at a desired position on the femur, the second curvature corresponding line can be inclined outward or inward with respect to the second reference line when viewed from the front, and the direction of the screw hole can be inclined forward or backward with respect to the first reference line. That is, the curved portion of the shaft portion can be curved externally or internally with respect to the external curvature shape or internal curvature shape of the femur, and the direction of the lag screw can be matched with the anteversion angle or posterior curvature angle of the femur, so that the intramedullary nail can be fitted to the femur. This allows the intramedullary nail to be fitted to the direction of curvature of the anteversion shape of the femur and the anteversion angle or posterior curvature angle, and can be placed at an optimal position without difficulty. Furthermore, before the intramedullary nail is inserted into the femur, the direction in which the screw holes are formed is approximately parallel to the first reference line when viewed head-on; in other words, the direction in which the screw holes are formed is not tilted in advance by a certain angle with respect to the anteversion angle. Therefore, even if the intramedullary nail is externally or internally rotated during insertion, the position of the tip of the lag screw can be prevented from shifting from near the center of the femoral head.

[0069] In addition, when the apex of the curved portion is located in the medial direction as viewed from the second reference line, and the third angle is 7°, the intramedullary nail is inserted into the femur and rotated outward by 12° midway, so that when the intramedullary nail is placed at a desired position on the femur, the second curve corresponding line is inclined outward by 5° (5° outward curvature) with respect to the second reference line when viewed from the front, and the direction of the screw hole is inclined forward by 12° with respect to the first reference line. That is, the curved portion of the shaft is outwardly curved by 5° with respect to the femur having a 5° outward curvature shape and an anterior torsion angle of 12°, and the direction of the lag screw can be adapted to an anterior torsion angle of 12°. This allows the intramedullary nail to be comfortably positioned at an optimal position by adapting it to the lordotic shape and anterior torsion angle of the femur. Furthermore, before the intramedullary nail is inserted into the femur, the direction in which the screw holes are formed is approximately parallel to the first reference line when viewed from the front, i.e., the direction in which the screw holes are formed is not tilted in advance by a certain angle with respect to the anteversion angle, so that even if the intramedullary nail is externally rotated by 12° during insertion, the position of the tip of the lag screw can be prevented from shifting forward from near the center of the femoral head. Furthermore, with this intramedullary nail, before it is inserted into the femur, the curved portion of the shaft is curved inward by 7° when viewed from the front.

[0070] Further, when viewed from the front and before the start of insertion of the intramedullary nail into the femur, in a range of a third angle that is an angle between a second curve corresponding line, which is a line connecting the first axis on the second reference line and the apex of the curved portion, and the second reference line, the apex of the curved portion is located in the medial direction as viewed from the second reference line, and the third angle is within a range of 1° to 25°, or the apex of the curved portion is located in the lateral direction as viewed from the second reference line, and the third angle is within a range of 1° to 25°, and the screw hole is located in the lateral direction as viewed from the first reference line, and the third angle is within a range of 1° to 25°. When the first reference line is used as a reference and the second reference line is used as a reference line, the second curvature corresponding line is inclined outward or inward, and the screw hole is inclined forward or backward with respect to the first reference line when the intramedullary nail is inserted into the femur without external or internal rotation and the intramedullary nail is placed at a desired position of the femur, the second curvature corresponding line can be inclined outward or inward with respect to the second reference line when viewed from the front, and the screw hole can be inclined forward or backward with respect to the first reference line. That is, the intramedullary nail can be adapted to the femur by externally or internally curving the curved portion of the shaft portion with respect to the external or internal curvature shape of the femur and by adjusting the direction of the lag screw with respect to the antetorsion angle or posterior torsion angle of the femur. This allows the intramedullary nail to be placed in an optimal position without strain, by adapting it to the direction of the lordotic curvature of the femur and the anteversion angle or retroversion angle. Also, it is possible to insert the intramedullary nail into the femur without external or internal rotation. Also, before the intramedullary nail is inserted into the femur, the direction of the screw hole is inclined in advance to the anterior or posterior side with respect to the first reference line when viewed from the front, so that simply inserting the intramedullary nail straight to the desired position allows the lag screw to correspond to the anteversion angle or retroversion angle, and the position of the tip of the lag screw can be prevented from shifting from the vicinity of the center of the femoral head.

[0071] In addition, when the apex of the curved portion is located in the outward direction as viewed from the second reference line, the third angle is 5°, the screw hole formation direction is inclined forward with respect to the first reference line, and the fourth angle is 12°, when the intramedullary nail is inserted into the femur without external rotation and the intramedullary nail is placed at a desired position of the femur, the second curve corresponding line can be inclined outward by 5° (5° outward curve) with respect to the second reference line when viewed from the front, and the screw hole formation direction can be inclined forward by 12° with respect to the first reference line. That is, the curved portion of the shaft can be outwardly curved by 5° with respect to the femur having a 5° outward curve shape and an anterior torsion angle of 12°, and the direction of the lag screw can be adapted to an anterior torsion angle of 12°. This allows the intramedullary nail to be comfortably positioned at an optimal position by adapting it to the lordotic shape and anterior torsion angle of the femur. In addition, the intramedullary nail can be inserted into the femur without external rotation. In addition, before the intramedullary nail is inserted into the femur, the direction of the screw hole is inclined 12° forward from the first reference line when viewed from the front. Therefore, simply inserting the intramedullary nail straight to the desired position allows the lag screw to accommodate an anterior twist angle of 12°, and the position of the tip of the lag screw can be prevented from shifting forward from the vicinity of the center of the femoral head. In addition, in this intramedullary nail, before insertion into the femur, the curved portion of the shaft is curved outward by 5° when viewed from the front. Effect of the Invention

[0072] The intramedullary nail of the present invention can prevent malfunctions that occur during the surgical procedure for fractures of the proximal femur, and can be placed in an ideal position within the femur to connect and firmly fix the bone fragments. [Brief description of the drawings]

[0073] [Figure 1] FIG. 1A is a schematic diagram showing the anteversion angle of the femur as viewed from the proximal to the distal side, and FIG. 1B is a schematic diagram showing the coronal, sagittal, and transverse planes that cross the human body. [Diagram 2]FIG. 1(a) is a schematic side view showing the shape of a right femur when viewed from the inside to the outside in the medial-lateral direction along the coronal plane of the human body (side view), and FIG. 1(b) is a schematic front view showing the shape of a right femur when viewed from the front to the back in the anterior-posterior direction along the sagittal plane of the human body (front view). [Diagram 3] FIG. 2 is a schematic diagram showing the outer curvature shape of the femur. [Figure 4] FIG. 1(a) is a diagram showing the state in which the posterior condyle of the femur and the posterior edge of the greater trochanter of the femur are positioned on the same plane (reference plane); FIG. 1(b) is a diagram showing the position of the posterior condyle and the position of the posterior edge of the greater trochanter of the femur when viewed from outside to inside along the medial-lateral direction; and FIG. 1(c) is a diagram showing the position of the posterior condyle when viewed from distal to proximal along the longitudinal direction of the femur. [Diagram 5] FIG. 2 is a schematic diagram showing the internal curvature shape of the femur. [Figure 6] 1A to 1D are diagrams showing the shape of a conventional intramedullary nail, and FIG. 1E is a diagram showing the positional relationship between the lateral curvature shape of the femur and the bending direction of the curved portion in the shaft. [Figure 7] FIG. 1(a) is a schematic diagram showing a conventional intramedullary nail inserted into a femur with its tip in contact with the femoral cortical bone, and FIG. 1(b) is a schematic diagram showing the conventional intramedullary nail being externally rotated and being inserted toward the distal side. [Figure 8] 1(a) is a schematic diagram showing a state in which the tip of the lag screw is positioned anterior to the center of the femoral head in a conventional intramedullary nail, and FIG. 1(b) is a schematic diagram showing a state in which a gap occurs between the bone fragments to be fixed when the femur is compressed from the outside. [Figure 9] FIG. 1A is a front view of a bone synthesis device having an intramedullary nail according to the first embodiment of the present invention, and FIG. 1B is a side view of the bone synthesis device looking from the front to the back, and FIG. [Figure 10] FIG. 2 is a view showing a state in which the bone setting tool is inserted into a desired position of the femur. [Figure 11]1A is a front view of the intramedullary nail as viewed from the front to the rear, and FIG. 1B is a side view of the intramedullary nail as viewed from the inside to the outside. [Figure 12] FIG. 2 is a schematic view of the intramedullary nail viewed from the base end to the tip end just before the intramedullary nail is inserted into the femur. [Figure 13] FIG. 2 is a schematic diagram showing the state in which the intramedullary nail has been inserted into the femur and externally rotated 12° from the front. [Figure 14] FIG. 1 shows the positions of four bend portions in the shaft of the intramedullary nail, where (aa) is a front view of the intramedullary nail looking from the front to the back, and (b) is a side view of the intramedullary nail looking from the outside to the inside. [Figure 15] FIG. 2 is a schematic enlarged view showing four bend portions. [Figure 16] 13 is a diagram showing the correspondence between the location where the bone begins to bend in the lordotic shape of the femur and the curvature start position of the first bend portion of the intramedullary nail. FIG. [Figure 17] 13 is a diagram showing the correspondence between the apex of the bone bend in the lordotic shape of the femur and the curvature start position of the second bend portion of the intramedullary nail. FIG. [Figure 18] FIG. 13 is a diagram showing the corresponding relationship between the anterior cortical bone of the femur and the curvature start position of the third bend portion of the intramedullary nail. [Figure 19] FIG. 13 is a diagram showing the correspondence between the range of greater curvature in the lordotic shape of the femur and the curvature start position of the fourth bend portion of the intramedullary nail. [Figure 20] Regarding a bone fixation device having an intramedullary nail which is the second embodiment of the present invention, (a) is a front view of the bone fixation device looking from the front to the back, and (b) is a side view of the bone fixation device looking from the outside to the inside. [Figure 21] 1A is a front view of the intramedullary nail as viewed from the front to the rear, and FIG. 1B is a side view of the intramedullary nail as viewed from the outside to the inside. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0074] Hereinafter, embodiments of the present invention will be described for the purpose of understanding the present invention. In the following, the terms "anterior (front)", "posterior (rear)", "internal (inner)", and "external (outer)" are all used as terms indicating the respective directions along a plane that crosses the human body, as described above. In the following, with regard to the intramedullary nail (or shaft), the part of the intramedullary nail that is proximal to the trunk of the patient to be treated is referred to as the "base end side", and the part of the intramedullary nail that is distal to the trunk of the patient to be treated is referred to as the "distal end side".

[0075] In addition, when the femur is viewed from the side with reference to FIG. 2(a), a shape in which the shaft curves forward with the apex P of the curve on the front side is referred to as a "lordotic shape."

[0076] 3, a viewpoint seen from the proximal side to the distal side along the longitudinal direction of the femur and from the direction in which the posterior condyle is located below is referred to as a "front view." Also, with reference to FIG. 3, a line connecting the posterior condyles (medial condyle F3 and lateral condyle F4) in a front view is referred to as a "reference line A," and a line that is approximately perpendicular to this reference line A and passes through positions M1 at both ends of the center of the medullary cavity is referred to as a "reference line B."

[0077] Also, with reference to Figure 3, when viewed from the front, with respect to the inclination of the direction of curvature in the lordotic shape relative to the reference line B, a shape in which the direction of curvature in the lordotic shape is inclined outward when viewed from the reference line B is referred to as an "external curvature shape."

[0078] In addition, when viewed from the front, regarding the inclination of the curve of the lordotic shape with respect to the reference line B, a shape in which the direction of the curve of the lordotic shape is inclined inward when viewed from the reference line B is referred to as an "internal curve shape."

[0079] [First embodiment of the present invention] 9(a) and 9(b), an intramedullary nail 1, which is an example of an intramedullary nail to which the present invention is applied, is a member used in combination with a lag screw 2, a sub-pin 3, a locking screw 4, a locking screw 5, a set screw (not shown), and an end cap (not shown) during surgery. Each member constitutes a bone setting tool A.

[0080] 9(a) is a front view of the bone setting tool A seen from the front to the rear, and FIG.9(b) is a side view of the bone setting tool A seen from the outside to the inside.

[0081] In this embodiment, each component of the bone setting tool A is preferably made of a titanium alloy, but is not limited thereto, and may be made of known materials having excellent biocompatibility and high fatigue strength, such as alloys of aluminum and vanadium, stainless steel, various engineering plastics, etc. Also, each component of the bone setting tool may be made of a different material.

[0082] The intramedullary nail 1 is inserted from the tip side toward the distal side of the femur and is a member that connects bone fragments so that the bone fragments do not shift and adhere to each other or separate until the fractured area heals. The intramedullary nail 1 is also a member that holds a lag screw 2 or the like inserted in the bone.

[0083] The intramedullary nail 1 is a member for use in a left femur. Although the following description will be given based on the intramedullary nail 1, the intramedullary nail to which the present invention is applied can also be applied to an intramedullary nail for use in a right femur. The intramedullary nail for use in a right femur has a shape corresponding to the lordotic shape, anteversion angle (retroversion angle), and lateral curvature shape (medial curvature shape) of the right femur, but has the same basic structure as the intramedullary nail 1.

[0084] The lag screw 2 is a member that connects bone fragments together to prevent the bone fragments from slipping and adhering or from becoming separated until the fractured area heals.

[0085] The sub-pin 3 is a member that protrudes into the fracture site to connect the fractured bone fragments. The sub-pin 3 bites into the cancellous bone to generate resistance to the rotational force applied to the bone fragments of the bone to be treated, and cooperates with the lag screw 2 to prevent the bone fragments from rotating.

[0086] The locking screws 4 and 5 are members for fixing the lower end of the intramedullary nail 1 to the bone to be treated. In this embodiment, the locking screws 4 and 5 are used in only two places, but this is not limited to this, and the number of locking screws 4 and 5 can be appropriately used according to the number of transverse holes (reference numbers omitted) formed in the intramedullary nail 1, etc.

[0087] The bone setting tool A also has a set screw (not shown). The set screw is a member provided above and inside the long axis hole of the intramedullary nail 1, and by engaging with the lag screw 2, it holds the lag screw 2 so that it does not move backward and fall out, and also suppresses the rotation of the lag screw 2.

[0088] Fig. 10 is a diagram showing a state in which the bone setting tool A is inserted into a desired position (optimum depth) of the femur F. Fig. 10 is a front view of the femur F and the bone setting tool A, seen from the front to the rear. The femur shown in Fig. 10 is the left femur.

[0089] 10, the tip of the intramedullary nail 1 is inserted into the femoral shaft F5 at a position near the distal femur F7, and the tip of the lag screw 2 is inserted into the femoral proximal femur F8 at a position near the center of the femoral head F1.

[0090] The shape of the intramedullary nail 1 will now be described in detail.

[0091] Fig. 11(a) and Fig. 11(b) show only the intramedullary nail 1, with Fig. 11(a) being a view corresponding to Fig. 9(a) and Fig. 11(b) being a view corresponding to Fig. 9(b). Fig. 11(a) and Fig. 11(b) also show a simulated view, indicated by the reference symbol 2a, of the position of the tip of the lag screw 2 when the lag screw 2 is inserted into the intramedullary nail 1.

[0092] 11(a) and 11(b), the intramedullary nail 1 is composed of a proximal body portion 10, a shaft portion 11, and a distal body portion 12. The intramedullary nail 1 is a cylindrical body having a long axial hole (not shown) penetrating the inside along its longitudinal axis.

[0093] Moreover, the main body proximal part 10 is a member that constitutes the base end side of the intramedullary nail 1. The main body proximal part 10 is formed with a screw hole 100 for inserting the lag screw 2 and a pin hole 101 for inserting the sub-pin 3. The direction in which the screw hole 100 is formed will be described later.

[0094] Moreover, the screw hole 100 and the pin hole 101 are formed so as to intersect with a longitudinal hole passing through the inside of the intramedullary nail 1 .

[0095] Furthermore, a set screw (not shown) is built into the inside of the base end side of the main body proximal portion 10.

[0096] The proximal body portion 10 has a uniform diameter portion 10a formed with a substantially uniform outer diameter, and a reduced diameter portion 10b whose outer diameter gradually decreases toward the shaft portion 11. The axis of the end portion of the shaft portion 11 connected to the reduced diameter portion 10b of the proximal body portion 10, which constitutes a part of this cylindrical body (the axis of the starting position of the shaft portion 11), corresponds to the "first axis which is the axis of one end side of the shaft portion" in the claims of the present application.

[0097] Moreover, the shaft portion 11 is a portion that extends along the longitudinal direction of the intramedullary nail 1. Moreover, the shaft portion 11 is formed with a curved portion 110 (see FIG. 11(b)).

[0098] This curved portion 110 is a portion for positioning the intramedullary nail 1 along the lordotic shape and lateral curvature shape of the femur when the intramedullary nail 1 is inserted to a predetermined position in the femur. The details of the bending of the curved portion 110 will be described later.

[0099] Further, two lateral holes 111 and 112 are formed on the main body distal portion 12 side of the shaft portion 11. Each hole is a hole portion for inserting the locking screw 4 and the locking screw 5, respectively, and is formed to intersect with the long axis hole penetrating the inside of the intramedullary nail 1.

[0100] Furthermore, the lateral stop holes 111 and 112 are formed in different directions.

[0101] Here, the forming direction of the lateral stop hole 111 and the forming direction of the lateral stop hole 112 do not necessarily have to be different from each other. However, it is preferable that the forming direction of the lateral stop hole 111 and the forming direction of the lateral stop hole 112 are different from each other in order to fix the bone setting tool A more firmly to the bone to be treated by changing the direction in which the two locking screws 4 and 5 are inserted.

[0102] The distal body portion 12 is a member that constitutes the tip side of the intramedullary nail 1. The distal body portion 12 is formed so that the outer diameter gradually decreases toward the tip. The tip of the distal body portion 12 is an opening 120 of a long axial hole that penetrates the inside of the intramedullary nail 1.

[0103] Next, the formation direction of the screw holes 100 corresponding to the anteversion angle of the femur and the bending direction of the curved portion 110 of the shaft portion 11 corresponding to the lateral curvature shape of the femur will be described.

[0104] First, the direction in which the screw hole 100 for inserting the lag screw 2 in the intramedullary nail 1 is formed is in the left-right direction when the intramedullary nail 1 is viewed from the base end toward the tip end (a perspective equivalent to the above-mentioned frontal view) immediately before the intramedullary nail 1 is inserted into the femur (see Figure 12).

[0105] 12, the screw holes 100 are formed in the left-right direction in the figure (the direction connecting 3 o'clock and 9 o'clock in the circumferential direction of a clock). In addition, when it is assumed that there is a horizontal plane below the intramedullary nail 1, the angle between the horizontal plane and the direction in which the screw holes 100 are formed is 0° (approximately parallel).

[0106] In addition, the direction of the curved portion 110 of the shaft portion 11 is such that, in a perspective of the intramedullary nail 1 seen from the base end side toward the tip end side (perspective corresponding to the above-mentioned front view), the "vertical line L3" passing through the axis of the start position of the shaft portion 11 and the "curve corresponding line L4" connecting the axis of the start position of the shaft portion 11 and the apex of the curve of the curved portion 110, the curve corresponding line L4 is located on the inside of the vertical line L3 as seen from the femur, and the angle between the vertical line L3 and the curve corresponding line L4 is 7° (see FIG. 12). This direction of the curved portion 110 is called a "7° inward curve".

[0107] In addition, Figure 12 illustrates the intramedullary nail 1 with a lag screw 2, a locking screw 4, and a locking screw 5 attached to it to make it easier to visualize the direction in which the screw hole 100 is formed and the direction in which the curved portion 110 of the shaft portion 11 bends just before the intramedullary nail 1 is inserted into the femur.

[0108] In an actual treatment, as described below, the intramedullary nail 1 is inserted into the femur, externally rotated, and with the intramedullary nail 1 in a predetermined position, the lag screw 2, locking screw 4, and locking screw 5 are inserted; therefore, no components are inserted into the intramedullary nail 1 before it is inserted into the femur.

[0109] Thus, the intramedullary nail 1 has the above-described direction of the screw hole 100 (0° substantially parallel to the horizontal plane) and the direction of curvature of the curved portion 110 of the shaft portion 11 (7° inward curvature).

[0110] During the treatment, the intramedullary nail 1 is inserted into the femur from its tip, and the operator externally rotates the intramedullary nail 1 by 12° when viewed from the front (rotating the intramedullary nail outwardly around the axis of the starting position of the shaft portion 11), so that the angle between the formation direction of the screw hole 100 and the reference line A is 12°. Also, the angle between the curve corresponding line L4 and the reference line B is 5°, and the bending direction of the curved portion 110 of the shaft portion 11 is a 5° outward bending direction (see FIG. 13). In FIG. 13, the axis of the starting position of the shaft portion 11 is indicated by the symbol G, and the apex of the bending of the curved portion 110 is indicated by the symbol E.

[0111] In other words, the intramedullary nail 1 can be inserted into the femur and externally rotated by 12°, so that it can be positioned to fit the femur having an anteversion angle of 12° and an external curvature shape of 5°.

[0112] That is, the intramedullary nail 1 can position the tip of the lag screw 2 near the center of the femoral head F1 of a femur having an anteversion angle of 12°. Also, the position of the tip of the lag screw 2 can be prevented from moving toward the anterior side of the femoral head F1.

[0113] Furthermore, the intramedullary nail 1 can adjust the direction of curvature of the curved portion 110 of the shaft portion 11 to the femur having a 5° external curvature shape, thereby improving the compatibility of the shaft portion 11 with the femur.

[0114] Here, the intramedullary nail to which the present invention is applied is not necessarily limited to a case where the angle between the horizontal plane and the direction in which the screw holes 100 are formed is set to 0° (approximately parallel) when viewed from the front, and the intramedullary nail is externally rotated 12° after insertion into the femur and placed in the femur. This point can be designed and placed according to the anteversion angle of the femur. Here, preferably, the angle between the horizontal plane and the direction in which the screw holes 100 are formed and the angle at which the intramedullary nail is externally rotated (or internally rotated) can be set within a range of -2° to 35° with respect to the reference line A, which is a commonly seen numerical range for the anteversion angle and the posterior rotation angle.

[0115] Furthermore, the intramedullary nail to which the present invention is applied is not necessarily limited to a case in which the direction of curvature of the curved portion 110 is inwardly curved by 7° when viewed from the front, and the intramedullary nail is externally rotated by 12° after insertion into the femur and placed in the femur. This point can be designed and placed in accordance with the external or internal curvature shape of the femur and its angle. Here, the direction and angle of the curvature of the curved portion 110 and the angle at which the intramedullary nail is externally (or internally) rotated can be set within a general numerical range for the femur, that is, within a range of an internal curvature shape of 1° to 25° or an external curvature shape of 1° to 25°.

[0116] In this way, the intramedullary nail 1 has distinctive features in the direction in which the screw hole 100 is formed (0°, approximately parallel to the horizontal plane) and in the direction of curvature of the curved portion 110 of the shaft portion 11 (7° internal curvature), thereby providing a structure that sufficiently enhances compatibility with femora having a certain anteversion angle and external curvature shape.

[0117] Furthermore, in the intramedullary nail to which the present invention is applied, for example, the intramedullary nail can be designed using the combination of values ​​shown in Tables 1 to 6 below, and by inserting this into the femur, it is possible to assume a position that is suitable for the femur having a desired anteversion angle or posterior rotation angle and an external or internal curvature shape.

[0118] [Table 1]

[0119] [Table 2]

[0120] [Table 3]

[0121] [Table 4]

[0122] [Table 5]

[0123] [Table 6]

[0124] Here, for each combination of values ​​shown in Tables 1 to 6, first, the direction in which the screw hole 100 is formed is formed to be 0°, approximately parallel to the horizontal plane, when viewed from the front, just before the intramedullary nail 1 is inserted into the femur.

[0125] Also, for example, in Table 1, if the curvature of the curved portion of shaft portion 11 before insertion into the femur is 0° (no external or internal curvature), then by inserting this into the femur and externally rotating it by 1°, an intramedullary nail will be obtained that has an antetorsion angle of 1° and corresponds to a femur that is externally curved by 1°.

[0126] Also, for example, in Table 3, if the curved portion of shaft portion 11 before insertion into the femur is bent at an internal curve of 2°, then by inserting this into the femur and externally rotating it by 1°, an intramedullary nail will be obtained that has an anteversion angle of 1° and corresponds to a femur that is internally curved by 1°.

[0127] Furthermore, for example, in Table 5, if the curvature of the curved portion of shaft portion 11 before insertion into the femur is 3° external curvature, then by inserting this into the femur and internally rotating it by 2°, an intramedullary nail will be obtained that corresponds to a femur with a posterior torsion angle of 2° and an external curvature of 1°.

[0128] In this manner, the intramedullary nail of the present invention can be inserted into the femur and positioned to accommodate a femur having a desired anteversion or posterior rotation angle and an external or internal curvature shape.

[0129] The combinations of the values ​​in Tables 1 to 3 above are applicable not only to the intramedullary nail for the left femur but also to the intramedullary nail for the right femur.

[0130] Furthermore, the direction of the screw hole 100 does not necessarily need to be 0°, which is approximately parallel to the horizontal plane, when viewed from the front, immediately before inserting the intramedullary nail 1 into the femur. For example, by changing the angle with respect to the horizontal plane, the bending direction and angle of the curved portion of the shaft portion 11 and the rotating direction and angle after insertion can be appropriately set according to the anteversion angle or posterior torsion angle and the lateral or medial curvature shape of the target femur.

[0131] Next, the direction of curvature of curved portion 110 of shaft portion 11 corresponding to the lordotic shape of the femur will be described.

[0132] First, the intramedullary nail 1 is formed to have a length of 265 mm from its base end 13 to its tip end 14. Also, the curved portion 110 of the shaft portion 11 has bends (curves) provided at four locations along the longitudinal direction, forming the overall curve.

[0133] In Fig. 14(a) and Fig. 14(b), the start positions of curvature of the first bent portion, the second bent portion, the third bent portion, and the fourth bent portion are indicated by symbols A to D. Fig. 14(a) is a front view of the intramedullary nail 1 as viewed from the front to the rear. Fig. 14(b) is a side view of the intramedullary nail 1 as viewed from the outside to the inside.

[0134] As shown in Fig. 14(b), the curved portion 110 of the shaft portion 11 of the intramedullary nail 1 is curved from the left side to the right side as a whole in the figure, and this curvature corresponds to the curvature from the front to the back in the lordotic shape of the femur. Note that Fig. 14(a) and Fig. 14(b) show an intramedullary nail for the left femur, but in the intramedullary nail for the right femur, the curved portion of the shaft portion corresponds to the curvature from the front to the back in the lordotic shape of the femur, just like the left intramedullary nail.

[0135] In addition, because the curved portion 110 of the intramedullary nail 1 is curved, when viewed from the side, the distance h between the reference line L5, which corresponds to the extension of the axis of the proximal body portion 10, and the center position of the tip 14 is 15 mm.

[0136] Additionally, the curvature start position A of the first bend is 120 mm away from the base end 13 of the intramedullary nail 1. Additionally, the curvature start position B of the second bend is 150 mm away from the base end 13 of the intramedullary nail 1. Additionally, the curvature start position C of the third bend is 175 mm away from the base end 13 of the intramedullary nail 1. Additionally, the curvature start position D of the fourth bend is 205 mm away from the base end 13 of the intramedullary nail 1.

[0137] 15, in the intramedullary nail 1, the radius of curvature between positions AB is 457.2055 mm, the radius of curvature between positions BC is 475.1435 mm, and the radius of curvature between positions CD is 637.797 mm. Also, the radius of curvature between positions AC is 439.8625 mm, and the radius of curvature between positions BD is 543.8545 mm.

[0138] In this way, in the intramedullary nail 1, four bends are formed to form the overall curve of the curved portion 110. In addition, by forming these four bends, the distance h between the reference line L5 and the center position of the tip 14 of the intramedullary nail 1 becomes 15 mm.

[0139] Here, the intramedullary nail 1 is not necessarily limited to a length of 265 mm from its base end 13 to its tip end 14, and the length can be set appropriately. In addition, it is preferable that the total length of the intramedullary nail to which the present invention is applied is set within a range of 265 mm to 400 mm. Furthermore, by setting the total length to 265 mm, it becomes easier to adapt to the approximately average length of the femur of elderly Japanese people, particularly females.

[0140] In addition, the curved portion 110 of the shaft portion 11 of the intramedullary nail 1 does not necessarily have to be bent at four positions along the longitudinal direction to form an overall curve, and the curvature of the curved portion can be set appropriately. In addition, it is preferable that the curved portion is formed to correspond to a curvature with a curvature radius of 514 mm to 1358 mm in the range from the position just below the lesser trochanter to the position just above the patella, which is a general numerical range of the lordotic shape of the femur.

[0141] In addition, the intramedullary nail 1 is not necessarily limited to a distance h between the reference line L5 corresponding to the extension of the axis of the proximal body 10 and the center position of the tip 14 being 15 mm when viewed from the side due to the formation of the bend of the curved portion 110, but can be appropriately set. However, by setting the total length of the intramedullary nail 1 to 265 mm and the distance h to 15 mm, it becomes easier to position the tip of the intramedullary nail at an appropriate position inside the femur (femoral medullary cavity) in accordance with the approximately average length and lordotic shape of the femur of elderly Japanese people, especially women. In addition, in the present invention, it is preferable that the distance h between the reference line corresponding to the extension of the axis of the proximal body and the center position of the tip be set to 13 mm or more according to the total length of the intramedullary nail.

[0142] Furthermore, the relationship between the total length of the intramedullary nail and the distance h between the reference line L and the center position of the tip of the intramedullary nail can be set as follows, depending on the length of the femur of the patient to be treated. As an example, the total length of the intramedullary nail can be set to 300 mm to 320 mm and the distance h to 17 to 22 mm, or the total length of the intramedullary nail can be set to 340 mm to 360 mm and the distance h to 22 to 25 mm.

[0143] In addition, the distance from the base end of the intramedullary nail 1 to the start position of each bend and the value of the radius of curvature can be appropriately set for the four bends in the curved portion 110 of the shaft portion 11. However, by designing the intramedullary nail 1 as described above, the following effects are achieved.

[0144] First, the curvature start position A of the first bend portion is 120 mm away from the base end 13 of the intramedullary nail 1, and the radius of curvature between positions A and B is set to 457.2055 mm in side view. This makes it possible to adapt the first bend portion to the bone shape of the femur at the start of the lordotic curve as the tip 14 of the intramedullary nail advances to the optimal depth beyond the position corresponding to the apex of the lordotic curve in the center of the medullary cavity of the femur.

[0145] This reduces contact between the intramedullary nail 1 and the anterior cortical bone F9 in the proximal part of the femur, and enables the tip 14 of the intramedullary nail 1 to be smoothly inserted toward the distal direction of the femur. It also reduces the risk of fracture in the proximal part of the femur and the risk of preventing the intramedullary nail from being inserted to the optimal depth.

[0146] In this regard, in FIG. 16, reference symbol A indicates the curvature start position of the first bend portion, and reference symbol F9 indicates the anterior cortical bone in the proximal femur.

[0147] In addition, the curvature start position B of the second bend portion is 150 mm away from the base end 13 of the intramedullary nail 1, and the radius of curvature between positions BC is set to 475.1435 mm in side view, which makes it easier to form a shape that corresponds to the position corresponding to the apex of the lordotic shape at the center of the medullary cavity of the femur.

[0148] This makes it possible to easily insert the intramedullary nail into the position corresponding to the apex of the lordotic shape at the center of the medullary cavity of the femur and its neighboring positions. Also, the portion beyond the second bend portion can be easily adapted to the lordotic shape of the femur, allowing the intramedullary nail 1 to be comfortably positioned in an optimal position.

[0149] In this regard, in FIG. 17, reference symbol B indicates the curvature start position of the second bend portion, and reference symbol M2 indicates the position corresponding to the apex of the lordotic shape in the center of the medullary cavity of the femur.

[0150] In addition, the curvature start position C of the third bend portion is 175 mm away from the base end 13 of the intramedullary nail 1, and the radius of curvature between positions C and D is set to 637.797 mm in side view, which makes it easier to give the third bend portion a shape that corresponds to the position where the bone begins to drop from the anterior side to the posterior side in the lordotic shape of the femur (the starting point of the posterior curvature).

[0151] This makes it possible to avoid excessive contact between the tip 14 of the intramedullary nail 1 and the anterior cortical bone F10 in the distal portion of the femur, making it easier to guide the intramedullary nail to the center of the femoral medullary cavity.

[0152] In this regard, in FIG. 18, reference symbol C indicates the curvature start position of the third bend portion, and reference symbol F10 indicates the anterior cortical bone.

[0153] In addition, the curvature start position D of the fourth bend portion is 205 mm away from the base end 13 of the intramedullary nail 1, and the radius of curvature between positions C and D is set to 637.797 mm in side view. This makes it possible to prevent the tip 14 of the intramedullary nail 1 from protruding from the anterior cortex in the range T of the lordotic shape of the femur, which is the area distal to the apex of the lordotic shape of the femur, and makes it possible to insert the intramedullary nail into the center of the femoral medullary cavity.

[0154] This allows the lag screw to be inserted into the center of the femoral medullary cavity as well as into the optimal position, enabling the fracture site to be firmly fixed.

[0155] In this regard, in FIG. 19 , the symbol D indicates the start position of the curvature of the fourth bend portion, the symbol M2 indicates the position corresponding to the apex of the lordotic shape at the center of the medullary cavity of the femur, and the symbol T indicates the area distal to the apex of the lordotic shape of the femur, that is, the area with a greater curvature within the lordotic shape.

[0156] In this way, by setting the positions and curvatures of the four bends in the curved portion 110 of the shaft portion 11, the intramedullary nail 1 can be fully adapted to the shape of the lordotic curve of the femur.

[0157] Next, a procedure for inserting the intramedullary nail 1 according to the present invention into the femur will be simply described.

[0158] (1) A hole is drilled from the proximal to distal side of the shaft of the femur with a reamer, and the intramedullary nail 1 is inserted into the hole formed.

[0159] (2) The tip of the intramedullary nail 1 is inserted to a predetermined position inside the femur (femoral medullary cavity), and the intramedullary nail 1 is externally rotated 12° together with the target device to which the intramedullary nail 1 is attached. When viewed from the front, the direction in which the screw holes 100 are formed is aligned with the antetorsion angle of the femur, and the direction of the bend of the curved portion 110 of the shaft 10 is externally rotated 5°. In addition, the position of the screw hole 100 of the inserted intramedullary nail 1 is finely adjusted using an X-ray device.

[0160] (3) Drill a hole in the side of the femur corresponding to the intended insertion site of the lag screw 2, insert the lag screw 2 into the hole, and insert it through the screw hole 100 of the intramedullary nail 1 until the tip of the lag screw 2 reaches near the center of the femoral head F1.

[0161] (4) After the tip of the lag screw 2 reaches near the center of the femoral head F1, the engaging protrusion of the set screw built into the upper part of the long axial hole of the intramedullary nail 1 is inserted into the long groove of the lag screw 2 and pressed from above to fix the lag screw 2 in place.

[0162] (5) A hole is drilled on the side of the femur corresponding to the intended insertion site of the sub-pin 3, and the sub-pin 3 is inserted into the formed hole and passed through the pin hole 101 of the intramedullary nail 1 and the pin hole of the set screw placed in the intramedullary nail 1.

[0163] (6) An end cap is further attached to the top of the inserted set screw to make it difficult for the sub-pin 3 to come off the intramedullary nail 1.

[0164] By following the above steps, the bone setting tool A having the intramedullary nail 1 can be inserted into the femur to be treated, and the fracture site on the proximal side of the femur can be firmly fixed by the bone setting tool A.

[0165] The main effects of this embodiment are as follows.

[0166] First, in the intramedullary nail 1, the direction of curvature of the curved portion 110 of the shaft portion 11 can be set to an externally rotated angle of 5° in accordance with the external curvature shape of the femur F when viewed from the front. This allows the intramedullary nail 1 to be adapted to the external curvature shape of the femur F.

[0167] Furthermore, when inserting the intramedullary nail 1 into the femur F from the tip 14, the intramedullary nail 1 can be easily inserted by outwardly rotating the intramedullary nail 1 by 12°. Furthermore, by performing the outwardly rotating operation by 12°, the direction of curvature of the curved portion 110 of the shaft portion 11 can be curved outwardly by an angle of 5° when viewed from the front.

[0168] Furthermore, by performing this 12° external rotation operation, the angle that the direction in which the screw hole 100 is formed with respect to the reference line A can be set to 12° so that it corresponds to the anteversion angle of the femur F when viewed from the front.

[0169] Furthermore, during this 12° external rotation operation, the direction in which the screw hole 100 is formed is such that the tip of the lag screw 2 is positioned near the center of the femoral head F1, thereby preventing the tip of the lag screw 2 from being positioned on the anterior side of the femoral head F1.

[0170] This also makes it possible to avoid the task of compressing the femur from the outside and repositioning the tip of the lag screw 2 near the center of the femoral head F1 in response to a deviation in the tip of the lag screw 2. This prevents gaps from occurring between the bone fragments to be fixed due to compression, and prevents the knee from internally rotating and becoming excessively anteverted.

[0171] Furthermore, in the intramedullary nail 1, the curved portion 110 of the shaft portion 11 is formed with four bent portions, and by setting the position and curvature of each bent portion, the intramedullary nail 1 can be fully adapted to match the shape of the lordotic curvature of the femur.

[0172] [Second embodiment of the present invention] Next, an intramedullary nail 1a according to a second embodiment of the present invention will be described. In the following description, features different from the first embodiment of the present invention will be described, and the same reference numerals will be used for the same members as those in the first embodiment, and detailed description thereof will be omitted.

[0173] 20(a) and 20(b), an intramedullary nail 1a, which is an example of an intramedullary nail to which the present invention is applied, is a member used in combination with a lag screw 2, a sub-pin 3, a locking screw 4, a locking screw 5, a set screw, and an end cap during surgery. Each of these members constitutes a bone setting tool B.

[0174] Fig. 20(a) is a front view of the bone setting tool B seen from the front to the rear, and Fig. 20(b) is a side view of the bone setting tool B seen from the outside to the inside.

[0175] 21(a) and 21(b) show only the intramedullary nail 1a, with Fig. 21(a) being a view corresponding to Fig. 20(a) and Fig. 21(b) being a view corresponding to Fig. 20(b). Fig. 21(a) and Fig. 21(b) also show, with reference numeral 20a, a simulated position of the tip of the lag screw 2 when the lag screw 2 is inserted into the intramedullary nail 1a.

[0176] 21(a) and 21(b), the intramedullary nail 1a is composed of a proximal body portion 7, a shaft portion 8, and a distal body portion 9. The intramedullary nail 1a is a cylindrical body having a long axial hole (not shown) penetrating the inside along its longitudinal axis.

[0177] Further, the main body proximal portion 7 is formed with a screw hole 100a for inserting the lag screw 2 and a pin hole 101 for inserting the sub-pin 3. The direction in which the screw hole 100a is formed will be described later.

[0178] The screw hole 100a and the pin hole 101 are formed so as to intersect with a longitudinal hole passing through the inside of the intramedullary nail 1a.

[0179] Furthermore, a set screw (not shown) is built into the inside of the base end side of the main body proximal portion .

[0180] Moreover, the shaft portion 8 is formed with a curved portion 110a (see FIG. 21(b)).

[0181] The curved portion 110a is a portion for positioning the intramedullary nail 1a along the lordotic shape and lateral curvature shape of the femur when the intramedullary nail 1a is inserted to a predetermined position in the femur. The bending of the curved portion 110a will be described in detail later.

[0182] Furthermore, two lateral stop holes 111 and a lateral stop hole 112 are formed on the main body distal portion 9 side of the shaft portion 8.

[0183] Next, the formation direction of the screw holes 100a corresponding to the anteversion angle of the femur and the bending direction of the curved portion 110a of the shaft portion 8 corresponding to the lateral curvature shape of the femur will be described.

[0184] First, the direction in which the screw hole 100a, through which the lag screw 2 is inserted, in the intramedullary nail 1a is formed is such that, immediately before the intramedullary nail 1 is inserted into the femur, when the intramedullary nail 1a is viewed from the base end toward the tip end (a perspective equivalent to the above-mentioned frontal view), assuming that there is a horizontal plane below the intramedullary nail 1a, the angle between the horizontal plane and the direction in which the screw hole 100a is formed is 12° (it is diagonally upward at 12° from the horizontal plane; not shown).

[0185] In addition, the direction of the curved portion 110a of the shaft portion 8 is such that, in a perspective (corresponding to the above-mentioned frontal view) of the intramedullary nail 1a seen from the base end side toward the tip end side, the curved portion 110a is curved in such a way that the curved portion 110a is curved in such a way that the "vertical line L6 (not shown)" passing through the axis of the start position of the shaft portion 8 and the "curve corresponding line L7 (not shown)" connecting the axis of the start position of the shaft portion 8 and the apex of the curve of the curved portion 110a are located on the outside of the vertical line L6 as seen from the femur, and the angle between the vertical line L6 and the curve corresponding line L7 is 5°. This direction of the curved portion 110a is called a 5° outward curve.

[0186] Thus, the intramedullary nail 1a has the above-described direction in which the screw hole 100a is formed (12° with respect to the horizontal plane) and the direction in which the curved portion 110a of the shaft portion 8 is curved (5° outward curve).

[0187] During the treatment, the intramedullary nail 1a is inserted straight into the femur from its tip, and when viewed from the front, the angle of the direction in which the screw hole 100a is formed with respect to the reference line A is 12° without the operator externally rotating the intramedullary nail 1. In addition, the angle of the curve corresponding line L7 with respect to the reference line B is 5°, and the bending direction of the curved portion 110a of the shaft portion 8 is a 5° outward curve direction.

[0188] In other words, the intramedullary nail 1a can be inserted into the femur and can be positioned to fit the femur having an external curvature of 5° at an anteversion angle of 12° without external rotation.

[0189] That is, the intramedullary nail 1a can position the tip of the lag screw 2 near the center of the femoral head F1 of a femur having an anteversion angle of 12°. Also, the position of the tip of the lag screw 2 can be prevented from moving toward the anterior side of the femoral head F1.

[0190] Furthermore, in the intramedullary nail 1a, the direction of the curved portion 110a of the shaft portion 8 can be adjusted to match the femur having a 5° external curvature shape, thereby improving the compatibility of the shaft portion 8 with the femur.

[0191] In this way, the intramedullary nail 1a is characterized by the direction in which the screw hole 100a is formed (12° relative to the horizontal plane) and the direction of curvature of the curved portion 110a of the shaft portion 8 (5° lateral curvature), thereby providing a structure that sufficiently enhances compatibility with femora having a certain anteversion angle and lateral curvature shape.

[0192] Here, in the second embodiment of the present invention, it is not necessary that the angle between the horizontal plane and the direction in which the screw hole 100a is formed is 12° and the direction of curvature of the curved portion 110a is 5° outwardly curved in a frontal view immediately before the intramedullary nail 1 is inserted into the femur. For example, the angle between the horizontal plane and the direction in which the screw hole is formed can be set within a range of -2° to 35° in a frontal view in accordance with the anteversion angle or posterior torsion angle and the outward curvature or inward curvature shape of the target femur, and the direction of curvature of the curved portion can be an outward curvature shape in a range of 1° to 25° or an inward curvature shape in a range of 1° to 25°.

[0193] As described above, the intramedullary nail of the present invention can prevent problems that occur during the treatment of fractures at the proximal side of the femur, and can be placed in an ideal position within the femur to connect and adequately fix the bone fragments.

[0194] The invention made by the inventor has been specifically described above based on an embodiment, but it goes without saying that the present invention is not limited to the above embodiment and can be modified in various ways without departing from the gist of the invention. [Explanation of symbols]

[0195] A Bone joint device 1 Intramedullary nail 10 Proximal body 10a Same diameter part 10b Reduced diameter part 11 Shaft section 110 Curved part 12 Distal body 120 (long axis hole) opening 13 (of intramedullary nail) proximal end 14 Tip (of intramedullary nail) 100 screw hole 101 Pin hole 2 Lag screws 3 Sub-pin 4 Locking Screw 5 Locking Screw F Femur F1 (femoral) head F2 (femoral) neck F3 medial condyle F4 lateral condyle F5 (femoral) diaphysis F6 Posterior border of greater trochanter F7 (femur) distal F8 (proximal femur) F9 (anterior femur) cortical bone S1 Femoral neck axis S2 Femoral condylar axis M Center of the medullary cavity M1 Both ends of the center of the medullary cavity M2: The position of the center of the medullary cavity that corresponds to the apex of the lordotic curve L1 (of the femur) just below the lesser trochanter L2 (femur) - Position just above the patella L3 plumb line L4 Curved Corresponding Line L5: Line extending from the axis of the proximal part of the body in lateral view G Axis of the starting position of the shaft section B Bone joint device 1a Intramedullary nail 7 Proximal body 8 Shaft section 9 Distal body 100a screw hole 110a Curved section

Claims

1. an intramedullary nail for use in inserting into a proximal portion of a femur when a proximal side of the femur is fractured and in repositioning and fixing each bone fragment, the intramedullary nail comprising: a cylindrical body having a through hole formed therein, constituting one end side of the body, a body proximal portion having a screw hole formed therein for inserting a lag screw that intersects with the through hole and has a tip positioned within the femoral head of the femur; a shaft portion connected to the body proximal portion and constituting an intermediate portion of the body, the shaft portion having an outer circumferential diameter smaller than an outer circumferential diameter of the body proximal portion and extending toward the other end side of the body with the same diameter; and a body distal portion connected to the shaft portion and constituting the other end side of the body, The shaft portion has a curved portion that is curved from the front side to the rear side of the femur when viewed along the medial-lateral direction of the femur, When the intramedullary nail is inserted into the femur, In a direction of the shaft portion viewed from the one end side to the other end side, and with a horizontal line passing through a first axis, which is the axis of the same end side of the shaft portion, as a reference, the curved portion is located above the horizontal line, and a shaft vertical line that is a vertical line perpendicular to the horizontal line and passes through the first axis, and a first curve corresponding line that is a line connecting the first axis and the apex of the curve of the curved portion form a predetermined angle, and the horizontal line and a direction in which the lag screw is inserted in the screw hole form a second angle, The predetermined angle is an angle of 5° inclined in a counterclockwise direction with respect to the shaft vertical line, The second angle is 12° with respect to the horizontal line when the direction in which the lag screw is inserted in the screw hole is inclined toward the front side. Intramedullary nail.

2. The main body is formed with a total length in the range of 265 mm to 400 mm, By forming the curved portion in the shaft portion, the distance from a third reference line, which is a line corresponding to the position of a second axis, which is the axis of the main body proximal portion, to the center position of the tip of the main body distal portion, when viewed along the medial-lateral direction of the femur, is 13 mm or more. The intramedullary nail according to claim 1.

3. The curved portion is composed of four vent portions including a first vent portion, a second vent portion, a third vent portion, and a fourth vent portion, When viewed along the medial-lateral direction of the femur, The curvature start position of the first vent portion is 120 mm from one end of the main body proximal portion, The curvature start position of the second vent portion is 150 mm from one end of the main body proximal portion, The curvature start position of the third vent portion is 175 mm from one end of the main body proximal portion, The curvature start position of the fourth vent portion is 205 mm from one end of the main body proximal portion, The radius of curvature in the range between the curvature start position of the first vent portion and the curvature start position of the second vent portion is 457 mm; The radius of curvature of the range between the curvature start position of the second vent portion and the curvature start position of the third vent portion is 475 mm; The radius of curvature of the range between the curvature start position of the third vent portion and the curvature start position of the fourth vent portion is 637 mm. The intramedullary nail according to claim 1 or 2.

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