TECHNICAL FIELD

The present invention relates to femur fixation apparatuses.

BACKGROUND

Bone fixation treatments using bone fixation apparatuses are widely performed for proximal femur fractures or femoral trochanter fractures. Because reduction at an early stage in bone fixation treatment and fixation methods have a huge effect on postoperative process, bone fixation apparatuses with a firm fixing force are needed for maintaining reduced positions. For better treatments, it is preferable that the number of anti-rotation members to use and insertion angles thereof be chosen according to conditions of bone fracture.

In this regard, a femur fixation apparatus disclosed in Patent Document 1 includes an intramedullary nail to be inserted into a femoral shaft, a lag screw and three anti-rotation pins to be inserted through the intramedullary nail, and a set screw (adjuster) installed in the intramedullary nail. Among the three anti-rotation pins, one anti-rotation pin is inserted through the intramedullary nail so as to be parallel with the lag screw, and the remaining two anti-rotation pins are inserted through the intramedullary nail such that they are oblique to the lag screw and that tip end sections of the anti-rotation pins intersect each other in a plan view. That is, the set screw having a sliding part with a relatively long length widens the choice of the number of the anti-rotation pins to use and the choice of insertion angles thereof, enabling excellent osteosynthesis.

In the configuration of Patent Document 1, however, because the anti-rotation pins are not fixed to the intramedullary nail, there is a danger that the anti-rotation pins loosen and come off (back out).

On the other hand, there have been proposed femur fixation apparatuses with urging members or resilient members for fixing lag screws or anti-rotation pins in place. For example, in a femur fixation apparatus disclosed in Patent Document 2, a second element of a rock mechanism which uses urging force of a coil spring is engaged with an abutting configuration of an implant (lag screw) to prevent inward movement of the lag screw.

Intramedullary fixation systems disclosed in Patent Documents 3 and 4 include an intramedullary nail body, a first engaging member accommodated in the intramedullary nail body, a second engaging member accommodated in the first engaging member, and a bone screw (an anti-rotation pin) to be inserted through the intramedullary nail body and the first engaging member. In these systems, a coil-shaped elastic member fitted around the second engaging member holds the second engaging member in an initial position. When an end cap is inserted into the intramedullary nail body, a distal end thereof presses down the second engaging member to hold the bone screw, thereby preventing the bone screw from coming off the intramedullary nail body.

A bone fixing system disclosed in Patent Document 5 includes an intramedullary nail body, an insert accommodated in the intramedullary nail body, and a plurality of bone screws to be inserted through the intramedullary nail body and the insert. The insert is formed with a plurality of openings arranged along an axis line, and each bone screw is inserted through the corresponding opening. When an end cap is screwed into the intramedullary nail body, the end cap presses down the insert toward a distal end, and each bone screw is pressed by a corresponding pair of elastic engaging parts toward the distal end and sandwiched in a transverse direction perpendicular to an axis direction of the intramedullary nail body. As a result, the bone screw is fixed to the intramedullary nail body.

RELATED ART

Patent Documents

Patent Document 1: Japanese Patent No. 6293980Patent Document 2: Japanese Patent Application Publication No. 2012-507355Patent Document 3: Japanese Patent Application Publication No. 2014-64613Patent Document 4: Japanese Patent Application Publication No. 2016-195746Patent Document 5: Japanese Patent Application Publication No. 2018-33616

SUMMARY

Problems to be Solved by Invention

Patent Document 2 discloses a configuration to fix in place the lag screw with the urging force of the coil spring. If the same lock mechanism as that of Patent Document 2 is employed for fixing in place a lag screw having no abutting configuration, however, there is a problem that fixing force is insufficient.

Because the configurations of Patent Documents 3 and 4 require the coil spring fitted around the first engaging member, the coil-shaped elastic member fitted around the second engaging member, and a deformable area defined by the slit formed in the second engaging member, there is a problem that the first engaging member has only a limited area where the bone screw can be inserted. Also, in the system of Patent Document 5, because the bone screw is sandwiched by the pair of elastic engaging parts in the transverse direction, in order to make a plurality of bone screws insertable in an alignment with one another in the transverse direction through the intramedullary nail body, the bone screws need to be thinner, making the bone screws weak and easy to break.

It is an object of the invention to provide a femur fixation apparatus that firmly fixes an anti-rotation member in place.

Means to Solve the Problems

A femur fixation apparatus according to one aspect of the invention includes: an intramedullary nail extending in a first direction; a first anti-rotation member configured to be inserted through the intramedullary nail; and an adjuster fitted in the intramedullary nail, wherein: the adjuster includes a rotation part and a sliding part extending in the first direction; the sliding part is unrotatable and slide-movable in the first direction relative to the intramedullary nail and has a first end on a first side in the first direction and a second end on a second side opposite to the first side in the first direction; the rotation part is rotatably and threadedly engaged in the intramedullary nail and rotatably connected to the first end of the sliding part; the sliding part is formed with a first space through which the first anti-rotation member is inserted; the sliding part has a first urging member extending from a side wall of the first space into the first space; and when the rotation part is rotated in a predetermined direction relative to the intramedullary nail, then the adjuster moves toward the second side relative to the intramedullary nail, and the first urging member presses toward the second side and fixes in place the first anti-rotation member.

A femur fixation apparatus according to another aspect of the invention includes: an intramedullary nail extending in a first direction; a lag screw configured to be inserted through the intramedullary nail; an anti-rotation member configured to be inserted through the intramedullary nail; and an adjuster fitted in the intramedullary nail, wherein: the adjuster includes a rotation part and a sliding part extending in the first direction; the sliding part is unrotatable and slide-movable in the first direction relative to the intramedullary nail and has a first end on a first side in the first direction and a second end on a second side opposite to the first side in the first direction; the rotation part is rotatably and threadedly engaged in the intramedullary nail and rotatably connected to the first end of the sliding part; the sliding part has a support part and a movable part movable in the first direction relative to the support part; the movable part has a main part and a spring part, the main part having a first end on the first side and a second end on the second side, the spring part extending from the second end of the main part toward the second side, the spring part being deformable in the first direction; the support part and the main part of the movable part are respectively formed with a first space and a second space through which the anti-rotation member is inserted; and when the movable part is pressed toward the second side, then the spring part is compressed, and the main part moves relative to the support part toward the second side, thereby fixing in place the anti-rotation member inserted through the first space and the second space.

Effects of the Invention

According to the femur fixation apparatus of one aspect of the invention, the sliding part has the first urging member extending from the side wall of the first space into the first space, and the first urging member presses, from the first side toward the second side, the first anti-rotation member inserted through the intramedullary nail and passing through the adjuster. Thus, it is possible to prevent the first anti-rotation member from coming out the intramedullary nail.

According to the femur fixation apparatus in the another aspect of the invention, when the movable part of the sliding part is pressed toward the second side, then the spring part is compressed, and the main part of the movable part moves relative to the support part toward the second side, thereby fixing the anti-rotation member in place. In this manner, it is possible to prevent the anti-rotation member from coming out the intramedullary nail.

