JP7851019B2 - external fixator - Google Patents

Description

This invention relates to an external fixator that maintains the joint space between a first bone portion and a second bone portion in a joint, such as the knee joint.

For example, in the treatment of knee arthritis, bone drilling is sometimes performed to create a hole in the injured knee joint using a drill or the like, in order to induce bleeding from the bone marrow and form bone marrow mesenchymal cells in the injured knee joint. If the injured knee joint is subjected to impact or other trauma in the early postoperative period, it can damage the immature tissue. Therefore, the inventor of this application has developed an external fixator that maintains the joint space between the first and second bone portions of the knee joint through the repulsive force between a first permanent magnet and a second permanent magnet, and this technology has already been published (see Patent Documents 1 and 2). A brief explanation of the configuration of the prior art external fixator is as follows:

The external fixator comprises a first pin attached to a first bone portion and a second pin attached to a second bone portion. The external fixator includes a first retaining member provided on one end of the first pin for maintaining the joint space of the knee joint; the first retaining member has a first permanent magnet. The external fixator also includes a second retaining member provided on one end of the second pin for maintaining the joint space of the knee joint; the second retaining member has a second permanent magnet with the same polarity as the first permanent magnet and facing it.

In the external fixator described in Patent Document 1, the first retaining member (referred to as the first magnet portion in Patent Document 1) and the second retaining member (referred to as the second magnet portion in Patent Document 1) are connected by a connecting member so that the position of the second retaining member (referred to as the second magnet portion in Patent Document 1) can be adjusted relative to the first retaining member on a virtual plane perpendicular to the longitudinal direction of the second pin (first pin). In the external fixator described in Patent Document 2, the movement of the first permanent magnet and the second permanent magnet in the second direction perpendicular to the first direction, which is their repulsive direction, is restricted by a first restricting portion. The movement of the second permanent magnet and the second permanent magnet in the third direction perpendicular to the first and second directions is restricted by a second restricting portion.

Patent No. 5753695 Patent No. 6114746

Incidentally, as mentioned above, in the external fixator described in Patent Document 1, the first retaining member and the second retaining member are connected by a connecting member. In the external fixator described in Patent Document 2, the movement of the first permanent magnet and the second permanent magnet in two directions is restricted by the first restricting part and the second restricting part. Therefore, the movement of the second retaining member is constrained by the first retaining member. As a result, for example, when a twisting motion is applied to the knee joint so that the toes point inward or outward, the second retaining member has difficulty following the movement of the second pin, and further improvements to the external fixator are desired.

Therefore, one aspect of the present invention aims to stably maintain the joint space of a joint, such as the knee joint, even when twisting or other movements are applied to the joint.

An external fixator according to one aspect of the present invention is an external fixator for holding the joint space between a first bone portion and a second bone portion in a joint, comprising: a first pin attached to the first bone portion; a second pin attached to the second bone portion; a first retaining member integrally provided on one end of the first pin and having a first permanent magnet for holding the joint space; and a second retaining member integrally provided on one end of the second pin and having a second permanent magnet with the same polarity as the first permanent magnet and facing it, configured separately from the first retaining member, for holding the joint space.

According to one aspect of the present invention, the joint space of a joint can be stably maintained even when twisting or other movements are applied to the joint.

This is a schematic front view showing an external fixator according to the first embodiment. This is a schematic side view showing an external fixator according to the first embodiment. This is a schematic side view showing the state of the external fixator according to the first embodiment when the knee joint is bent. This is a schematic front view showing the state of the external fixator according to the first embodiment when the knee joint is twisted. This is a schematic front view showing an external fixator according to a modified example of the first embodiment. This is a schematic front view showing an external fixator according to the second embodiment. This is a schematic side view showing an external fixator according to the second embodiment. This is a schematic front view showing an external fixator according to the third embodiment. This is a schematic side view showing an external fixator according to the third embodiment.

The first to third embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment]
The configuration of the external fixator 10 according to the first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic front view showing the external fixator 10 according to the first embodiment. Figure 2 is a schematic side view showing the external fixator 10 according to the first embodiment.

(Overview of the external fixator 10)
As shown in Figure 1, the external fixator 10 according to the first embodiment is a medical device used to treat arthritis such as knee arthritis, and holds the joint space ARc between the first bone BF and the second bone BS in the knee joint AR, which is an example of a joint. By holding the joint space ARc of the knee joint AR, the external fixator 10 absorbs the impact or load applied to the injured part of the knee joint AR. The first bone BF in the knee joint AR is the femur, and the second bone BS in the knee joint AR is the tibia.

(1st pin 12)
As shown in Figures 1 and 2, the external fixator 10 is equipped with a rod-shaped first pin 12 that is attached to the first bone portion BF, and the first pin 12 is inserted through a through hole BFh formed in the first bone portion BF by a drill or the like. The first pin 12 is positioned to pass through or near the center of rotation of the knee joint AR. Male threaded portions 12s are formed on both ends of the first pin 12. Multiple male threaded portions 12t are formed on the middle side of the first pin 12 for fixing the first pin 12 to the first bone portion BF. Preferably, the first pin 12 is made of a material containing titanium, which has excellent biocompatibility.

(2nd pin 14)
As shown in Figures 1 and 2, the external fixator 10 is equipped with a rod-shaped second pin 14 that is attached to the second bone portion BS. The second pin 14 is inserted through a through hole Bsh formed in the second bone portion BS by a drill or the like. Male threaded portions 14s are formed on both ends of the second pin 14. Multiple male threaded portions 14t are formed on the middle side of the second pin 14 for fixing the second pin 14 to the second bone portion BS. It is desirable that the second pin 14 be made of a material containing titanium, which has excellent biocompatibility.

(First holding member 16, first permanent magnet 18)
As shown in Figures 1 and 2, the external fixator 10 is equipped with first retaining members 16 integrally provided on both ends of the first pin 12, and each first retaining member 16 is a member for holding the joint space ARc of the knee joint AR. The side view shape of each first retaining member 16 is formed to be circular, and each first retaining member 16 has a curved portion 16c that curves in a convex arc shape (an example of a convex shape) toward the second pin 14 side. An insertion hole 16h is formed in the center of each first retaining member 16 for inserting one end or the other end of the first pin 12.

Furthermore, the curved portion 16c of each first retaining member 16 does not need to be curved in a convex arc shape, as long as it is curved convexly toward the second pin 14. As long as each first retaining member 16 has a curved portion 16c, the plan view shape of each first retaining member 16 may be a shape other than a circle, such as a semicircle or a sector.

Each first retaining member 16 has an arc-shaped mounting groove (mounting recess) 16d formed in its curved portion 16c, and an arc-shaped first permanent magnet 18 is fixed to each mounting groove 16d. In other words, each first retaining member 16 has an arc-shaped first permanent magnet 18 on the curved portion 16c side. Each first permanent magnet 18 may be a ferrite magnet, alnico magnet, rare earth magnet, rubber magnet, or plastic magnet, and preferably a neodymium magnet among the rare earth magnets. The main body portion 16m of each retaining member 16, excluding the first permanent magnet 18, is made of a non-magnetic material such as ceramic, non-magnetic stainless steel, or plastic. In Figure 1, the north pole side of the first permanent magnet 18 is shown with diagonal hatching, and the south pole side of the first permanent magnet 18 is shown with dot hatching.

Furthermore, the first permanent magnet 18 may be fixed without forming a mounting groove 16d in the curved portion 16c of each first retaining member 16. The method of attaching the first permanent magnet 18 to the main body portion 16m of each first retaining member 16 may be by screw attachment, adhesive attachment, or any other known attachment method. Each first retaining member 16 may also be constructed from a permanent magnet so that each first retaining member 16 has a first permanent magnet 18.

Each first retaining member 16 is fixed to the first pin 12 by being clamped between multiple fixing nuts 20 that are screwed onto the male threaded portion 12s of the first pin 12. Each first retaining member 16 can be positioned in the longitudinal direction of the first pin 12 by changing the screwing positions of the multiple fixing nuts 20. Each first retaining member 16 is rotatably adjustable around the axis of the first pin 12.

(Second holding member 22, second permanent magnet 24)
As shown in Figures 1 and 2, the external fixator 10 is equipped with second retaining members 22 integrally provided on both ends of the second pin 14, and each second retaining member 22 is a member for holding the joint space ARc of the knee joint AR. The side view shape of each second retaining member 22 is circular. Each second retaining member 22 has a curved portion 22c that curves in a convex arc shape (an example of a convex shape) toward the first pin 12 side, and each curved portion 22c faces the curved portion 16c of each first retaining member 16. An insertion hole 22h is formed in the center of each second retaining member 22 for inserting one end or the other end of the second pin 14. Note that each second retaining member 22 does not need to have a curved portion 22c as long as it has a portion that faces the curved portion 16c of each first retaining member 16.

Each second retaining member 22 has an arc-shaped mounting groove (mounting recess) 22d formed in its curved portion 22c, and an arc-shaped second permanent magnet 24 is fixed to each mounting groove 22d. In other words, each second retaining member 22 has an arc-shaped second permanent magnet 24 on the side facing the curved portion 16c of each first retaining member 16. Each second permanent magnet 24 may be a ferrite magnet, alnico magnet, rare earth magnet, rubber magnet, or plastic magnet, and is preferably a neodymium magnet among the rare earth magnets. The main body portion 22m of each retaining member 22, excluding the second permanent magnet 24, is made of a non-magnetic material such as ceramic, non-magnetic stainless steel, or plastic. In Figure 1, the north pole side of the second permanent magnet 24 is shown with diagonal hatching, and the south pole side of the second permanent magnet 24 is shown with dot hatching.

Furthermore, the second permanent magnet 24 may be fixed without forming a mounting groove 22d in the curved portion 22c of each second retaining member 22. The method of attaching the second permanent magnet 24 to the main body portion 22m of each second retaining member 22 may be by screw attachment, adhesive attachment, or any other known attachment method. Each second retaining member 22 may also be constructed from a permanent magnet so that each second retaining member 22 has a second permanent magnet 24.

Each second permanent magnet 24 is positioned to face each first permanent magnet 18 with the same polarity. Specifically, each second permanent magnet 24 and each first permanent magnet 18 are positioned so that their north poles face each other. Each second retaining member 22 is configured to be separate and independent from each first retaining member 16. In other words, each second retaining member 22 is configured to operate independently without being connected to each first retaining member 16, following the movement of one end or the other end of the second pin 14. Note that each second permanent magnet 24 and each first permanent magnet 18 may be positioned so that their south poles face each other.

Each second retaining member 22 is fixed to the second pin 14 by being clamped between multiple fixing nuts 26 that are screwed onto the male threaded portion 14s of the second pin 14. Each second retaining member 22 can be positioned in the longitudinal direction of the second pin 14 by changing the screwing positions of the multiple fixing nuts 26. Each second retaining member 22 is rotatably adjustable around the axis of the second pin 14.

(Effects and Benefits)
The effects of the first embodiment will be explained with reference to Figures 3 and 4. Figure 3IIIA is a schematic diagram showing the state of the external fixator 10 when the knee joint AR is bent at 45 degrees. Figure 3IIIB is a schematic diagram showing the state of the external fixator 10 when the knee joint AR is bent at 90 degrees. Figure 4 is a diagram showing the state of the external fixator 10 when the knee joint AR is twisted.

In the external fixator 10, as described above, each second permanent magnet 24 is arranged so as to face each first permanent magnet 18 with the same polarity. Therefore, the repulsive force between the two sets of first permanent magnets 18 and second permanent magnets 24 can stably hold the joint space ARc of the knee joint AR. This reduces the impact or load applied to the injured area of the knee joint AR, allowing the knee joint AR to move, for example, as shown in IIIA and IIIB of Figure 3, thereby enhancing the therapeutic effect of knee arthritis.

In the external fixator 10, as described above, each second retaining member 22 is configured independently of each first retaining member 16. Therefore, each second retaining member 22 can operate independently without being connected to each first retaining member 16, following the movement of one end or the other end of the second pin 14. This allows the joint space ARc of the knee joint to be stably held by the repulsive force between the two sets of first permanent magnets 18 and second permanent magnets 24, even when twisting or other movements are applied to the knee joint AR, as shown in Figure 4. As a result, the impact or load applied to the damaged area of the knee joint AR can be stably reduced, allowing the knee joint AR to move, as shown in Figures IIIA and IIIB, for example, and further enhancing the therapeutic effect of knee arthritis.

In the external fixator 10, as described above, each first retaining member 16 has a curved portion 16c that curves in a convex arc shape toward the second pin 14 side. Each first retaining member 16 has an arc-shaped first permanent magnet 18 on the side of the curved portion 16c. Therefore, while avoiding interference between the first retaining member 16 and the second retaining member 22, the knee joint AR can be moved, for example, as shown in IIIA and IIIB of Figure 3, while stably holding the joint space ARc of the knee joint AR.

In the external fixator 10, as described above, each first retaining member 16 is adjustable in the longitudinal direction of the first pin 12, and each second retaining member 22 is adjustable in the longitudinal direction of the second pin 14. Therefore, the external fixator 10 can be attached to the knee joint AR so that each first retaining member 16 and each second retaining member 22 are positioned appropriately according to the size of the knee joint AR, thereby increasing the versatility of the external fixator 10.

[Modification of the first embodiment]
Referring to Figure 5, the configuration of the external fixator 10A according to a modified example of the first embodiment will be described. Figure 5 is a schematic front view showing the external fixator 10A according to a modified example of the first embodiment. For the sake of explanation, the same reference numerals are used for components that have the same function as those described in the first embodiment, and their descriptions will not be repeated.

As shown in Figure 5, in the external fixator 10A according to a modification of the first embodiment, the first retaining member 16 is integrally provided only on one end of the first pin 12. The other end of the first pin 12 is designed not to protrude outward from the skin of the foot. Similarly, the second retaining member 22 is integrally provided only on one end of the second pin 14. The other end of the second pin 14 is designed not to protrude outward from the skin of the foot.

Furthermore, the modified version of the first embodiment also exhibits the same effects and benefits as those of the first embodiment described above.

[Second Embodiment]
The configuration of the external fixator 28 according to the second embodiment will be described with reference to Figures 6 and 7. Figure 6 is a schematic front view showing the external fixator 28 according to the second embodiment. Figure 7 is a schematic side view showing the external fixator 28 according to the second embodiment.

(Overview of the external fixator 28)
As shown in Figure 6, the external fixator 28 according to the second embodiment is a medical device that holds the joint space ARc between the first bone portion BF and the second bone portion BS in the knee joint AR, and absorbs the impact or load applied to the knee joint AR. Similar to the external fixator 10 according to the first embodiment (see Figures 1 and 2), the external fixator 28 comprises a first pin 12, a second pin 14, two first retaining members 16 having a first permanent magnet 18, and a plurality of fixing nuts 20.

(Second holding member 30, second permanent magnet 32)
As shown in Figures 6 and 7, the external fixator 28 has rod-shaped second retaining members 30 integrally provided on both ends of the second pin 14, instead of the second retaining member 22 (see Figures 1 and 2). Each second retaining member 30 is a member for holding the joint space ARc of the knee joint AR and is formed in the shape of a rod. An insertion hole 30h is formed at the base end of each second retaining member 30 for inserting one end or the other end of the second pin 14.

Each second retaining member 30 has a mounting recess 30d at its tip, and a small piece-shaped second permanent magnet 32 is fixed to each mounting recess 30d. In other words, each second retaining member 30 has a small piece-shaped second permanent magnet 32 at its tip. Each second permanent magnet 32 may be a ferrite magnet, alnico magnet, rare earth magnet, rubber magnet, or plastic magnet, and preferably a neodymium magnet among the rare earth magnets. The main body portion 30m of each retaining member 30, excluding the second permanent magnet 32, is made of a non-magnetic material such as ceramic, non-magnetic stainless steel, or plastic. In Figure 6, the north pole side of the second permanent magnet 32 is shown with diagonal hatching, and the south pole side of the second permanent magnet 32 is shown with dot hatching. Each second retaining member 30 may also be made of a permanent magnet so that each second retaining member 30 has a second permanent magnet 32.

Furthermore, the second permanent magnet 32 may be fixed without forming a mounting recess 30d at the tip of each second holding member 30. The method of attaching the second permanent magnet 24 to the main body 30m of each second holding member 30 may be by screw attachment, adhesive attachment, or any other known attachment method.

Each second permanent magnet 32 is positioned to face each first permanent magnet 18 with the same polarity. Specifically, each second permanent magnet 32 and each first permanent magnet 18 are positioned so that their north poles face each other. Each second retaining member 30 is configured to be separate and independent from each first retaining member 16. In other words, each second retaining member 30 is configured to operate independently without being connected to each first retaining member 16, following the movement of one end or the other end of the second pin 14. Note that each second permanent magnet 32 and each first permanent magnet 18 may be positioned so that their south poles face each other.

Each second retaining member 30 is fixed to the second pin 14 by being clamped between multiple fixing nuts 34 that are screwed onto the male threaded portion 14s of the second pin 14. Each second retaining member 30 can be positioned in the longitudinal direction of the second pin 14 by changing the screwing positions of the multiple fixing nuts 34. Each second retaining member 30 is rotatably adjustable around the axis of the second pin 14.

Furthermore, similar to the external fixator 10A according to the modification of the first embodiment, the first retaining member 16 may be integrally provided only on one end of the first pin 12. The second retaining member 30 may be integrally provided only on one end of the second pin 14.

(Effects and Benefits)
The effects and advantages of the second embodiment will now be described.

In the external fixator 28, as described above, each second permanent magnet 32 is arranged so as to face each first permanent magnet 18 with the same polarity. Therefore, the repulsive force between the two sets of first permanent magnets 18 and second permanent magnets 32 can stably hold the joint space ARc of the knee joint AR. This reduces the impact or load applied to the injured area of the knee joint AR, allowing the knee joint AR to move and improving the therapeutic effect of knee arthritis.

In the external fixator 28, as described above, each second retaining member 30 is configured independently of each first retaining member 16. Therefore, each second retaining member 30 can move independently, without being connected to each first retaining member 16, following the movement of one end or the other end of the second pin 14. This allows the joint space ARc of the knee joint to be stably held even when twisting or other movements are applied to the knee joint AR, due to the repulsive force between the two sets of first permanent magnets 18 and second permanent magnets 32. As a result, the impact or load applied to the damaged area of the knee joint AR can be stably reduced, allowing the knee joint AR to move and further enhancing the therapeutic effect of knee arthritis.

In the external fixator 28, as described above, each first retaining member 16 has an arc-shaped first permanent magnet 18 on the curved portion 16c side. Therefore, while avoiding interference between the first retaining member 16 and the second retaining member 22, the knee joint AR can be moved while stably holding the joint space ARc of the knee joint AR.

In the external fixator 28, as described above, each second retaining member 30 is formed in a rod shape. Therefore, the manufacturing of each second retaining member 30 is simplified, and the manufacturing cost of the external fixator 28 can be reduced.

In the external fixator 28, as described above, each first retaining member 16 is adjustable in the longitudinal direction of the first pin 12, and each second retaining member 30 is adjustable in the longitudinal direction of the second pin 14. Therefore, the external fixator 28 can be attached to the knee joint AR so that each first retaining member 16 and each second retaining member 30 are positioned appropriately according to the size of the knee joint AR, thereby increasing the versatility of the external fixator 28.

[Third Embodiment]
The configuration of the external fixator 36 according to the third embodiment will be described with reference to Figures 8 and 9. Figure 8 is a schematic front view showing the external fixator 36 according to the third embodiment. Figure 9 is a schematic side view showing the external fixator 36 according to the third embodiment.

(Overview of the external fixator 36)
As shown in Figure 8, the external fixator 36 according to the third embodiment is a medical device that holds the joint space ARc between the first bone portion BF and the second bone portion BS in the knee joint AR, and absorbs the impact or load applied to the knee joint AR. The external fixator 36 is equipped with a first pin 12 and a second pin 14, similar to the external fixator 10 according to the first embodiment (see Figures 1 and 2).

(First intermediate member 38)
As shown in Figures 8 and 9, the external fixator 36 includes first intermediate members (intermediate members) 38 integrally provided on both ends of the first pin 12, and each first intermediate member 38 extends in a direction perpendicular to the longitudinal direction of the first pin 12. Each first intermediate member 38 is composed of a single link member connected to one end or the other end of the first pin 12. An insertion hole 38h is formed at the base end of each first intermediate member 38 for inserting one end or the other end of the first pin 12. Each first intermediate member 38 is made of a non-magnetic material such as ceramic, non-magnetic stainless steel, or plastic. Alternatively, each first intermediate member 38 may be composed of multiple rotatably connected link members instead of a single link member.

Each first intermediate member 38 is fixed to the first pin 12 by being clamped between multiple fixing nuts 40 that are screwed onto the male threaded portion 12s of the first pin 12. Each first intermediate member 38 can be positioned in the longitudinal direction of the first pin 12 by changing the screwing positions of the multiple fixing nuts 40. Each first intermediate member 38 can be rotated around the axis of the first pin 12.

(First holding member 44, first permanent magnet 46)
As shown in Figures 8 and 9, the external fixator 36 includes a first retaining member 44 provided on the tip side of each first intermediate member 38 by mounting screws 42. In other words, each first intermediate member 38 is provided between one end or the other end of the first pin 12 and the first retaining member 44. The external fixator 36 includes first retaining members 44 integrally provided on both ends of the first pin 12 via the first intermediate members 38. Each first retaining member 44 is a member for holding the joint space ARc of the knee joint AR. The side view shape of each first retaining member 44 is formed to be circular, and each first retaining member 44 has a curved portion 44c that curves in a convex arc shape (an example of a convex shape) toward the second pin 14 side. An insertion hole 44h is formed in the central part of each first retaining member 44 for inserting one end or the other end of the first pin 12.

Furthermore, the curved portion 44c of each first retaining member 44 does not need to be curved in a convex arc shape, as long as it is curved convexly toward the second pin 14. As long as each first retaining member 44 has a curved portion 44c, the plan view shape of each first retaining member 44 may be a shape other than a circle, such as a semicircle or a sector.

Each first retaining member 44 has an arc-shaped mounting groove (mounting recess) 44d formed in its curved portion 44c, and an arc-shaped first permanent magnet 46 is fixed to each mounting groove 44d. In other words, each first retaining member 44 has an arc-shaped first permanent magnet 46 on the curved portion 44c side. Each first permanent magnet 46 may be a ferrite magnet, alnico magnet, rare earth magnet, rubber magnet, or plastic magnet, and preferably a neodymium magnet among the rare earth magnets. The main body portion 44m of each retaining member 44, excluding the first permanent magnet 46, is made of a non-magnetic material such as ceramic, non-magnetic stainless steel, or plastic. In Figure 8, the north pole side of the first permanent magnet 46 is shown with diagonal hatching, and the south pole side of the first permanent magnet 46 is shown with dot hatching.

Furthermore, the first permanent magnet 46 may be fixed without forming a mounting groove 44d in the curved portion 44c of each first retaining member 44. The method of attaching the first permanent magnet 46 to the main body portion 44m of each first retaining member 44 may be by screw attachment, adhesive attachment, or any other known attachment method. Each first retaining member 44 may also be constructed from a permanent magnet so that each first retaining member 44 has a first permanent magnet 46.

Each first retaining member 44 is fixed to the first pin 12 via each first intermediate member 38. Each first retaining member 44 is position-adjustable in the longitudinal direction of the first pin 12 via each first intermediate member 38. Furthermore, each first retaining member 44 is rotatably adjustable around the axis of the first pin 12 via each first intermediate member 38. Each first retaining member 44 is position-adjustable in the longitudinal direction of each first intermediate member 38 via each mounting screw 40 and the elongated holes (not shown) in each first intermediate member 38. In other words, each first retaining member 44 is position-adjustable on a virtual plane perpendicular to the longitudinal direction of the first pin 12.

(Second intermediate member 48)
As shown in Figures 8 and 9, the external fixator 36 includes second intermediate members (intermediate members) 48 integrally provided on both ends of the second pin 14, and each second intermediate member 48 extends in a direction perpendicular to the longitudinal direction of the second pin 14. Each second intermediate member 48 is composed of a single link member connected to one end or the other end of the second pin 14. An insertion hole 48h is formed at the base end of each second intermediate member 48 for inserting one end or the other end of the second pin 14. Each second intermediate member 48 is made of a non-magnetic material such as ceramic, non-magnetic stainless steel, or plastic. Alternatively, each second intermediate member 48 may be composed of multiple rotatably connected link members instead of a single link member.

Each second intermediate member 48 is fixed to the second pin 14 by being clamped between multiple fixing nuts 50 that are screwed onto the male threaded portion 14s of the second pin 14. The position of each second intermediate member 48 can be adjusted in the longitudinal direction of the second pin 14 by changing the screwing positions of the multiple fixing nuts 50.

(Second holding member 54, second permanent magnet 56)
As shown in Figures 8 and 9, the external fixator 36 includes a second retaining member 54 provided on the tip side of each second intermediate member 48 by mounting screws 52. In other words, each second intermediate member 48 is provided between one end or the other end of the second pin 14 and the second retaining member 54. The external fixator 36 includes second retaining members 54 provided integrally on both ends of the first pin 12 via the second intermediate member 48. Each second retaining member 54 is a member for holding the joint space ARc of the knee joint AR. The side view shape of each second retaining member 54 is circular. Each second retaining member 54 has a curved portion 54c that curves in a convex arc shape (an example of a convex shape) toward the first pin 12 side, and each curved portion 54c faces the curved portion 44c of each first retaining member 44. Each second retaining member 54 has a through hole 54h formed in its central portion for inserting one end or the other end of the first pin 12. Note that each second retaining member 54 does not need to have a curved portion 54c, as long as it has a portion facing the curved portion 44c of each first retaining member 44.

Each second retaining member 54 has an arc-shaped mounting groove (mounting recess) 54d formed in its curved portion 54c, and an arc-shaped second permanent magnet 56 is fixed to each mounting groove 54d. In other words, each second retaining member 54 has an arc-shaped second permanent magnet 56 on the side facing the curved portion 44c of each first retaining member 44. Each second permanent magnet 56 may be a ferrite magnet, alnico magnet, rare earth magnet, rubber magnet, or plastic magnet, and preferably a neodymium magnet among the rare earth magnets. The main body portion 54m of each retaining member 54, excluding the second permanent magnet 56, is made of a non-magnetic material such as ceramic, non-magnetic stainless steel, or plastic. In Figure 8, the north pole side of the second permanent magnet 56 is shown with diagonal hatching, and the south pole side of the second permanent magnet 56 is shown with dot hatching.

Furthermore, the second permanent magnet 56 may be fixed without forming a mounting groove 54d in the curved portion 54c of each second retaining member 54. The method of attaching the second permanent magnet 56 to the main body portion 54m of each second retaining member 54 may be by screw attachment, adhesive attachment, or any other known attachment method. Each second retaining member 54 may also be constructed from a permanent magnet so that each second retaining member 54 has a second permanent magnet 56.

Each second permanent magnet 56 is positioned to face each first permanent magnet 46 with the same polarity. Specifically, each second permanent magnet 56 and each first permanent magnet 46 are positioned so that their north poles face each other. Each second retaining member 54 is configured to be separate and independent from each first retaining member 44. In other words, each second retaining member 54 is configured to operate independently without being connected to each first retaining member 44, following the movement of one end or the other end of the second pin 14. Note that each second permanent magnet 56 and each first permanent magnet 46 may be positioned so that their south poles face each other.

Each second retaining member 54 is fixed to the second pin 14 via each second intermediate member 48. Each second retaining member 54 is position-adjustable in the longitudinal direction of the second pin 14 via each second intermediate member 48. Furthermore, each second retaining member 54 is rotatably adjustable around the axis of the second pin 14 via each second intermediate member 48. Each second retaining member 54 is position-adjustable in the longitudinal direction of each second intermediate member 48 via each mounting screw 52 and the elongated holes (not shown) in each second intermediate member 48. In other words, each second retaining member 54 is position-adjustable on a virtual plane perpendicular to the longitudinal direction of the second pin 14.

Furthermore, similar to the external fixator 10A according to a modification of the first embodiment, the first retaining member 44 may be integrally provided on only one end of the first pin 12 via the first intermediate member 38. Similarly, the second retaining member 54 may be integrally provided on only one end of the second pin 14 via the second intermediate member 48.

(Effects and Benefits)
The effects and advantages of the third embodiment will now be described.

In the external fixator 36, as described above, each second permanent magnet 56 is arranged so as to face each first permanent magnet 46 with the same polarity. Therefore, the repulsive force between the two sets of first permanent magnets 46 and second permanent magnets 56 can stably hold the joint space ARc of the knee joint AR. This reduces the impact or load applied to the damaged area of the knee joint AR, allowing the knee joint AR to move and improving the therapeutic effect of knee arthritis.

In the external fixator 36, as described above, each second retaining member 54 is configured independently of each first retaining member 44. Therefore, each second retaining member 54 can move independently, without being connected to each first retaining member 44, following the movement of one end or the other end of the second pin 14. This allows the joint space ARc of the knee joint to be stably held even when twisting or other movements are applied to the knee joint AR, due to the repulsive force between the two sets of first permanent magnets 46 and second permanent magnets 56. As a result, the impact or load applied to the damaged area of the knee joint AR can be stably reduced, allowing the knee joint AR to move and further enhancing the therapeutic effect of knee arthritis.

In the external fixator 36, as described above, each first retaining member 44 has a curved portion 44c that curves in a convex arc shape toward the second pin 14 side. Each first retaining member 44 has an arc-shaped first permanent magnet 46 on the side of the curved portion 44c. Therefore, while avoiding interference between the first retaining member 44 and the second retaining member 54, the knee joint AR can be moved while stably holding the joint space ARc of the knee joint AR.

In the external fixator 36, as described above, each first retaining member 44 is adjustable in the longitudinal direction of the first pin 12, and each second retaining member 54 is adjustable in the longitudinal direction of the second pin 14. Therefore, the external fixator 36 can be attached to the knee joint AR so that each first retaining member 44 and each second retaining member 54 are positioned appropriately according to the size of the knee joint AR, thereby increasing the versatility of the external fixator 36.

In the external fixator 36, as described above, first retaining members 44 are integrally provided on both ends of the first pin 12 via a first intermediate member 38. Second retaining members 54 are integrally provided on both ends of the first pin 12 via a second intermediate member 48. Therefore, the degree of freedom in attaching the first retaining member 44 to the first pin 12 and the degree of freedom in attaching the second retaining member 54 to the second pin 14 can be increased.

In the external fixator 36, as described above, each first retaining member 44 is adjustable in position on a virtual plane perpendicular to the longitudinal direction of the first pin 12. Each second retaining member 54 is adjustable in position on a virtual plane perpendicular to the longitudinal direction of the second pin 14. Therefore, each first retaining member 44 can be easily positioned in an appropriate position relative to the first pin 12, and each second retaining member 54 can be easily positioned in an appropriate position relative to the second pin 14.

[Other Embodiments]
The external fixator 10 (10A, 28, 36) having the above configuration may be used, for example, to maintain the joint space between the first and second bone portions in joints other than the knee joint AR, such as the ankle joint, hip joint, elbow joint, and finger joint.

〔summary〕
An external fixator according to aspect 1 of the present invention is an external fixator for holding the joint space between a first bone portion and a second bone portion in a joint, comprising: a first pin attached to the first bone portion; a second pin attached to the second bone portion; a first retaining member integrally provided on one end of the first pin and having a first permanent magnet for holding the joint space; and a second retaining member integrally provided on one end of the second pin and having a second permanent magnet opposite to the first permanent magnet with the same polarity, configured separately from the first retaining member, and for holding the joint space.

According to the above configuration, since the second permanent magnet is opposite the first permanent magnet and has the same polarity, the repulsive force between the first and second permanent magnets can maintain the joint space of the joint. This reduces the impact or load applied to the damaged part of the joint, allowing the joint to move and enhancing the therapeutic effect of arthritis.

Furthermore, since the second retaining member is configured separately from the first retaining member, the second retaining member can operate independently of the first retaining member, following the movement of the second pin. This allows the joint space to be stably maintained by the repulsive force between the first and second permanent magnets, even when twisting or other movements are applied to the joint. As a result, the impact or load applied to the damaged part of the joint can be stably reduced, allowing the joint to move and further enhancing the therapeutic effect of arthritis.

In the external fixator according to embodiment 2 of the present invention, in embodiment 1, the first retaining member may be integrally provided on both ends of the first pin, and the second retaining member may be integrally provided on both ends of the second pin.

According to the above configuration, the repulsive force between the two sets of first and second permanent magnets can stably maintain the joint space of the joint.

In the external fixator according to embodiment 3 of the present invention, in embodiment 1 or 2, the first pin is positioned on the first bone portion so as to pass through the rotation center of the joint or its vicinity, the first retaining member has a curved portion that is convex toward the second pin side, and the first retaining member may have the first permanent magnet on the side of the curved portion.

According to the above configuration, the joint can be moved while maintaining the joint gap of the joint, while avoiding interference between the first and second holding members.

In the external fixator according to embodiment 4 of the present invention, the second retaining member may be formed in a rod shape, as in embodiment 3.

According to the above configuration, the manufacturing of the second retaining member 30 is simplified, and the manufacturing cost of the external fixator can be reduced.

In the external fixator according to embodiment 5 of the present invention, in any of embodiments 1 to 4, the first retaining member may be position-adjustable in the longitudinal direction of the first pin, and the second retaining member may be position-adjustable in the longitudinal direction of the second pin.

According to the above configuration, the external fixator can be attached to the joint such that the first and second retaining members are positioned appropriately according to the size of the joint. This increases the versatility of the external fixator.

The external fixator according to embodiment 6 of the present invention may include an intermediate member provided between the first pin and the first retaining member, or between the second pin and the second retaining member, in any of embodiments 1 to 5.

According to the above configuration, the degree of freedom in mounting at least one of the first retaining member and the second retaining member to the first pin or the second pin can be increased.

In the external fixator according to embodiment 7 of the present invention, in any of embodiments 1 to 6, at least one of the first retaining member and the second retaining member may be position-adjustable on a virtual plane perpendicular to the longitudinal direction of the first pin or the second pin.

According to the above configuration, at least one of the first retaining member and the second retaining member can be easily positioned at an appropriate location relative to the first pin or the second pin.

[Additional Notes]
The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

10. External fixator (external fixator according to the first embodiment)
12 First pin 12s Male threaded portion 12t Male threaded portion 14 Second pin 14s Male threaded portion 14t Male threaded portion 16 First retaining member 16m Main body portion 16c Curved portion 18 First permanent magnet 20 Fixing nut 22 Second retaining member 22m Main body portion 22c Curved portion 24 Second permanent magnet 26 Fixing nut 10A External fixator (External fixator according to a modified example of the first embodiment)
28. External fixator (external fixator according to the second embodiment)
30 Second retaining member 30m Main body 32 Second permanent magnet 34 Fixing nut 36 External fixator (External fixator according to the third embodiment)
38. First intermediate member (intermediate member)
40 Fixing nut 42 Mounting screw 44 First retaining member 44m Main body 44c Curved section 46 First permanent magnet 48 Second intermediate member (intermediate member)
50 Fixing nut 52 Mounting screw 54 Second retaining member 54m Main body 54d Mounting groove 56 Second permanent magnet AR Knee joint (joint)
ARc Joint space BF 1st bone BS 2nd bone

Claims (6)

An external fixator that maintains the joint space between the first and second bone portions in a joint,
A first pin attached to the first bone portion,
A second pin attached to the second bone portion,
A first retaining member is integrally provided on one end of the first pin and has a first permanent magnet for holding the joint gap,
The second pin is integrally provided on one end side and has a second permanent magnet that is the same polarity as and opposite to the first permanent magnet, and is configured separately from the first retaining member, and comprises a second retaining member for holding the joint gap,
An external fixator wherein the first retaining member is adjustable in position in the longitudinal direction of the first pin, and the second retaining member is adjustable in position in the longitudinal direction of the second pin . The external fixator according to claim 1, wherein the first retaining member is integrally provided on both ends of the first pin, and the second retaining member is integrally provided on both ends of the second pin. The external fixator according to claim 1, wherein the first pin is positioned on the first bone portion so as to pass through the rotation center of the joint or its vicinity, the first retaining member has a curved portion that is convex toward the second pin side, and the first retaining member has the first permanent magnet on the side of the curved portion. The external fixator according to claim 3, wherein the second retaining member is formed in a rod shape. The external fixator according to claim 1, further comprising an intermediate member provided between the first pin and the first retaining member, or between the second pin and the second retaining member, at least in either case. The external fixator according to claim 1, wherein at least one of the first retaining member and the second retaining member is adjustable in position on a virtual plane perpendicular to the longitudinal direction of the first pin or the second pin.