JP2015092886A - Bone fixation structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bone fixation structure by a screw in which an axial force obtained by the screw can be finely adjusted subsequently.SOLUTION: An axial side screw body 20 is formed in a rod-like member inserted into a bone. A first thread part 22 engaged with the bone is formed and a second thread part 24 is formed in the vicinity of the end exposed from the bone. A head side screw body 30 is screwed with the second thread part 24 and is radially expanded to the axial side screw body 20. Furthermore, the head side screw body 30 is made to include a head side abutment surface 38 coming into abutment with the bone. Thereby, the axial force can be finely adjusted subsequently by the adjustment of the head side screw body 30, independently of the engagement with the bone by the first thread part 22 of the axial side screw body 20.

Description

  The present invention relates to a bone fixing structure for fixing a screw body such as a screw to a bone.

  Conventionally, a screw is used to join fractured bones or attach a plate to the bone. When the screw is directly coupled to the bone, a tapped hole is formed in the fractured part, and a screw made of metal or ceramic is screwed into the tapped hole to join and fix the fractured part (for example, Patent Document 1). reference).

  The plate is used to avoid stress concentration on the bone by the head of the screw and to fix the relative position of the divided bone (for example, see Patent Document 2). In this case, the plate is fixed to the bone by screwing the screw into the bone through the opening formed in the plate.

  These screws use so-called tapping screws, and can be fastened even if a female screw is not cut in the bone. In addition, the screw is not limited to the surgical work application at the time of fracture, and may be used for correcting bone.

Japanese Patent Laid-Open No. 10-85232 Japanese Patent Publication No. 8-126650

  In the case of the conventional bone fixing structure, it is difficult to finely adjust the fastening force by the screw. The tightening force can be increased by screwing the screw strongly. However, if the screw is loosened when the tightening force is too strong, there is a problem that the engagement between the screw and the bone tends to be loose.

  In particular, when a plate is fixed to a bone using a screw, it is convenient if the fastening force between the bone and the plate can be adjusted afterwards. However, if the screw is tightened or loosened to make a fine adjustment, there is a backlash between the bone and the screw. Therefore, in reality, it is difficult to finely adjust the degree of adhesion between the bone and the plate afterwards.

  In view of such circumstances, the present invention intends to provide a bone fixing structure capable of finely adjusting a fastening force between a bone and a screw afterwards.

  The above object can be achieved by the following means based on the earnest studies of the inventors.

  The present invention that achieves the above object is a rod-like member to be inserted into a bone, wherein a first screw portion that engages with the bone is formed, and a second screw portion is provided in the vicinity of an end portion that is exposed from the bone. A shaft-side screw body that is formed; and a head-side screw body that is screwed with the second screw portion of the shaft-side screw body and extends in a radial direction with respect to the shaft-side screw body. The side screw body is a bone fixing structure characterized by having a head side abutting surface that abuts against the bone.

  In relation to the bone fixing structure, the shaft-side screw body has a shaft-side extension portion that extends radially in the vicinity of an end portion where the second screw portion is formed, and the shaft-side extension portion. Has a shaft-side contact surface that contacts the bone, and the head-side contact surface of the head-side screw body contacts the bone at a radially outer side than the shaft-side contact surface. Features.

  The present invention that achieves the above object is a rod-like member that is inserted into a bone and a hole of a plate attached to the bone, and is formed with a first threaded portion that engages with the bone and is exposed from the bone A shaft-side screw body in which a second screw portion is formed in the vicinity of the head portion, and a head-side screw that engages with the second screw portion of the shaft-side screw body and extends radially with respect to the shaft-side screw body And the head-side screw body has a head-side contact surface that contacts the surface of the plate opposite to the bone.

  In relation to the bone fixing structure, the shaft-side screw body has a shaft-side extension portion that extends radially in the vicinity of an end portion where the second screw portion is formed, and the shaft-side extension portion. Has a shaft-side contact surface that contacts a surface of the plate opposite to the bone, and the head-side contact surface of the head-side screw body is radially outward from the shaft-side contact surface. The plate abuts against the plate.

  In relation to the bone fixing structure, the plate is slidable in the axial direction with respect to the shaft-side screw body, and according to the screwing degree of the head-side screw body and the shaft-side screw body. The head-side contact surface presses the plate toward the bone, thereby increasing the binding force between the plate and the bone.

  In relation to the bone fixing structure, the head-side contact surface of the head-side screw body is an inclined surface whose axial center is convex toward the first screw portion.

  In relation to the bone fixing structure, the lead of the second screw portion in the shaft side screw body is smaller than the lead of the first screw portion.

  In relation to the bone fixing structure, a through hole into which the K wire is inserted is formed over the entire longitudinal direction of the shaft side screw body.

  According to the bone fixing structure of the present invention, it is possible to obtain an excellent effect that the fastening force can be finely adjusted afterwards by the head side screw body independently of the state of engagement with the bone by the shaft side screw body.

It is a perspective view showing the bone fixation structure concerning a 1st embodiment of the present invention. (A) is a top view and a front view of a head-side screw body used in the same bone fixing structure, and (B) is a top view and a front view of a shaft-side screw body used in the same bone fixing structure. (A) is a fragmentary sectional view which shows the state which fixed the plate by the same bone fixing structure, (B) is a fragmentary sectional view which shows the state which fixed bone directly by the same bone fixing structure. (A) is a top view and a front view of a head-side screw body used in the same bone fixing structure according to the second embodiment of the present invention, and (B) is an upper surface of a shaft-side screw body used in the same bone fixing structure. It is a figure and a front view. It is a fragmentary sectional view which shows the state which fixed the plate by the same bone fixing structure. It is a fragmentary sectional view showing the state where bone was directly fixed by the same bone fixation structure. (A) is a front view which shows the axial side screw body and the head side screw body of the application example of the same bone fixation structure, (B) is a fragmentary sectional view which shows the state which fixed the plate by the application example. (A) is a front view which shows the axial side screw body and head side screw body of the bone fixation structure which concern on 3rd Embodiment, (B) is a fragmentary sectional view which shows the state which fixed the plate by the bone fixation structure. is there. It is a front view which shows the application example of the same bone fixation structure.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows a bone fixing structure 1 according to a first embodiment applied when fixing a fractured rib. The bone fixing structure 1 includes a plate 10 attached to the rib, and an axial screw body 20 and a head screw body 30 for fixing the plate 10 to the rib. Hereinafter, the plate 10, the shaft-side screw body 20, and the head-side screw body 30 will be described as an example applied to the radius, but may be applied not only to the radius but also to the humerus, the femur, and the like.

  The plate 10 has a main body portion 10A disposed on the proximal side of the rib and a head portion 10B disposed on the distal side. The main body portion 10A is provided with a total of five insertion holes 12A and is fixed to the ribs using the bone fixing structure 1. The head portion 10B is expanded in the planar direction as compared with the main body portion 10A, and three insertion holes 12B are provided along the distal edge of the radius. Here, the state where the shaft-side screw body 20 and the head-side screw body 30 are arranged with respect to one distal screw hole 12B is illustrated, but for all the insertion holes 12A, 12B The shaft-side screw body 20 and the head-side screw body 30 may be installed, or may be installed only for an arbitrary insertion hole.

  FIG. 2A shows the head-side screw body 30 and FIG. 2B shows the shaft-side screw body 20 in an enlarged manner.

  The shaft-side screw body 20 is a rod-like member that is inserted into the insertion holes 12A and 12B of the plate 10 and the ribs, and a first screw portion 22 for engaging with the ribs is formed on the distal end side. The first screw portion 22 is a tapping male screw, and enters the bone as it is and does not cut the female screw with respect to the rib.

  In the vicinity of the end portion of the base end exposed from the rib, a second screw portion 24 serving as a male screw is formed. A shaft-side tool coupling portion 26 is formed on the end face of the base end. In this embodiment, the shaft-side tool coupling portion 26 is a hexagonal recess, and is coupled to a hexagonal bar spanner (not shown). The shaft side screw body 20 is screwed into the rib by the hexagonal bar wrench.

  Further, the lead of the second screw portion 24 is smaller than the lead of the first screw portion 22. Thereby, the 1st screw part 22 turns into a tapping element for couple | bonding with a rib with a big lead, and the 2nd screw part 24 turns into a screw element for finely adjusting fastening force with a small lead.

  The head-side screw body 30 has a dimension that expands in the radial direction as compared with the shaft-side screw body 20, and has a connecting screw portion 34 in the center. The connecting screw portion 34 is a female screw, and is screwed into the second screw portion 24 of the shaft side screw body 20 to be fastened together. Further, a head-side tool coupling portion 36 is formed on the surface of the head-side screw body 30 opposite to the shaft-side screw body 20 (upper surface in FIG. 2). In the present embodiment, the head-side tool coupling portion 36 is a hexagonal recess, and is coupled to a hexagonal bar wrench (not shown) having a larger diameter than the shaft-side tool coupling portion 26 described above. In addition, this hexagon stick spanner has a hollow shape in order to avoid interference with the second screw portion 24 that gradually protrudes from the bottom surface of the head-side tool coupling portion 36 during the fastening operation (see FIG. 3A). It is preferable to do.

  Further, a head-side contact surface 38 is formed on the surface of the head-side screw body 30 on the shaft-side screw body 20 side (the lower surface in FIG. 2). The head-side abutting surface 38 abuts against the anticostal side surface (the upper surface in FIG. 1) of the plate 10. The head-side contact surface 38 contacts the bottom surface of the housing recess 14 formed around the insertion holes 12 </ b> A and 12 </ b> B of the plate 10, and transmits axial force to the plate 10.

  FIG. 3A shows an enlarged view of a bone fixing structure using the shaft-side screw body 20 and the head-side screw body 30.

  As a fixing procedure of the bone fixing structure of the first embodiment, first, the shaft side screw body 20 is screwed into the rib. Specifically, a hexagon wrench is coupled to the shaft side tool coupling portion 26 to rotate the shaft side screw body 20. As a result, the first screw portion 22 enters the female screw hole while machining the female screw hole, and the fastening is completed. At this time, the base end side of the shaft side screw body 20 is exposed to an extent that is slightly larger than the thickness of the plate 10.

  Thereafter, the position of the insertion holes 12A and 12B of the plate 10 is aligned with the shaft-side screw body 20 exposed from the rib, and the plate 10 is attached to the rib. That is, in this embodiment, the maximum outer shape of the second screw portion 24 is set smaller than the inner diameters of the insertion holes 12A and 12B of the plate 10 and the shaft-side screw body 20 is fixed to the ribs. It can be installed.

  Next, the head-side screw body 30 is coupled to the second screw portion 26 protruding from the insertion holes 12 </ b> A and 12 </ b> B of the plate 10. Specifically, a hexagonal bar wrench is engaged with the head-side tool coupling portion 36 and the head-side screw body 30 is rotated, so that the connecting screw portion 34 of the head-side screw body 30 is connected to the second screw portion 24. Screwed on. When the head-side screw body 30 is further rotated, the head-side screw body 30 is received in the receiving recess 14 of the plate 10 and the head-side contact surface 38 comes into contact with the bottom surface. As a result, the axial force generated in the head-side screw body 30 and the shaft-side screw body 20 is transmitted to the plate 10 via the head-side contact surface 38, and the plate 10 is pressed against the rib side. In other words, the ribs are attracted to the plate 10 side.

  The plate 10 is slidable in the axial direction (particularly in the distal end direction) with respect to the shaft-side screw body 20. As the head-side screw body 30 is tightened into the shaft-side screw body 20, the head-side contact surface 38 pushes the plate 10 toward the rib side, and the binding force / contact pressure between the plate 10 and the rib can be increased. .

  On the other hand, if the head-side screw body 30 is loosened, the adhesion between the plate 10 and the ribs can be reduced. At this time, the shaft-side screw body 20 does not need to be rotated, so that the shaft-side screw body 20 and the rib can be firmly engaged. Even if the head-side screw body 30 is fastened to the shaft-side screw body 20, the shaft-side screw body 20 does not rotate, so the relative positional relationship between the shaft-side screw body 20 and the ribs does not change. Therefore, it is possible to prevent the shaft-side screw body 20 from being excessively screwed and penetrating the ribs.

  In addition, although the case where the plate 10 is installed after the shaft side screw body 20 is screwed into the rib is shown here, the present invention is not limited to this. It is also preferable that the plate 10 is preliminarily attached to the ribs and the shaft-side screw body 20 is screwed into a desired position using the insertion holes 12A and 12B. In this case, the K wire hole 19 (refer FIG. 1) may be formed in the plate 10, and the plate 10 and the rib may be previously positioned using a K wire.

  In the first embodiment, the case where the plate 10 is fixed to the rib is exemplified. However, the bone fixing structure is used when the head-side screw body 30 and the shaft-side screw body 20 are directly fixed to the bone. it can. Specifically, as shown in FIG. 3 (B), after the shaft side screw body 20 is fastened to the bone, the head side screw body 30 with respect to the second screw portion 24 of the shaft side screw body 20. Screw together. As a result, the head-side contact surface 38 of the head-side screw body 30 directly contacts the bone. This axial force can be freely adjusted by rotating only the head-side screw body 30 with respect to the second screw portion 24. Accordingly, the degree of adhesion between the divided bones can be finely adjusted by the amount of rotation of the head screw body 30.

  Next, the bone fixation structure 1 according to the second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, parts different from the first embodiment will be mainly described, and the same or similar parts as those in the first embodiment will be shared with the first embodiment in the text and the drawings. The description will be omitted.

  As shown in FIG. 4, in the vicinity of the base end of the shaft-side screw body 20, an extension portion 27 that extends in the radial direction as compared with the first screw portion 22 is formed. A shaft-side contact surface 27A is formed on the side surface of the first threaded portion of the extended portion 27 and contacts the bottom surface of the housing recess 14 of the plate 10. That is, in the shaft-side screw body 20 of the second embodiment, the extended portion 27 functions as a so-called head even by itself, and the plate 10 can be pressed against the rib side by the shaft-side contact surface 27A. A second screw portion 24 is formed on the outer peripheral surface of the extended portion 27.

  The head-side screw body 30 has a hexagonal outer shape, and can be rotated by engaging with a hexagon wrench. A connecting screw portion 34 is formed at the center and is screwed into the second screw portion 24.

  As shown in FIG. 5, in the bone fixing structure 1 of the second embodiment, the plate 10 can be temporarily fixed to the rib using the shaft side screw body 20. The shaft-side contact surface 27A of the extended portion 27 engages with the bottom surface of the housing recess 14 of the plate 10 to fix the plate 10 to the rib. Thereafter, the head-side contact surface that surrounds the outer side in the radial direction of the shaft-side contact surface 27A by screwing the head-side screw body 30 to the second screw portion 24 formed around the expansion portion 27. 38 also contacts the bottom surface of the housing recess 14. When the head-side screw body 30 is further tightened, the plate 10 is pushed into the rib side, so that the inner peripheral side shaft-side contact surface 27A is separated from the bottom surface of the plate accommodating recess 14. As a result, the contact pressure between the plate 10 and the rib can be finely adjusted by the head-side screw body 30. Also from this, it is preferable that the fastening force of the plate 10 by the extended portion 27 of the shaft-side screw body 20 is set low (or zero).

  The bone fixing structure of the second embodiment can also be used when the head-side screw body 30 and the shaft-side screw body 20 are directly fixed to the bone. Specifically, as shown in FIG. 6, when the shaft-side screw body 20 is fastened to the bone, the shaft-side contact surface 27A of the expansion portion 27 is brought into contact with or close to the bone, and thereafter The head side screw body 30 is screwed into the second screw portion 24. As a result, the head-side contact surface 38 that surrounds the radially outer side of the shaft-side contact surface 27A directly contacts the bone, and accordingly, the shaft-side contact surface 27A moves away from the rib. The contact force of the head-side contact surface 38 can be freely adjusted by rotating only the head-side screw body 30 with respect to the second screw portion 24.

  Furthermore, in the bone fixing structure of the second embodiment, the case where the shaft-side contact surface 27A of the shaft-side screw body 20 is a plane orthogonal to the shaft is illustrated, but the present invention is not limited to this. For example, as shown in FIG. 7A, the shaft-side contact surface 27A can be an inclined surface whose axial center side (center side) is convex toward the first screw portion 22 side. Corresponding to this, as shown in FIG. 7B, the bottom surface of the accommodating recess 14 of the plate 10 can also be an inclined surface whose axial center side is recessed toward the first screw portion 22. When the shaft-side contact surface 27A and the bottom surface of the housing recess 14 are brought into contact with each other, the centers are autonomously centered so that the centers thereof coincide with each other. Even if the shaft-side screw body 20 is slightly inclined with respect to the plate 10, the shaft-side contact surface 27 </ b> A and the housing recess 14 can be brought into surface contact.

  Next, with reference to FIG. 8, the bone fixation structure 1 of 3rd Embodiment of this invention is demonstrated. In the third embodiment, parts different from the first embodiment will be mainly described, and the same or similar parts as those in the first embodiment have the same reference numerals as those in the first embodiment in the text and the drawings. The description will be omitted.

  As shown in FIG. 8A, the head-side contact surface 38 of the head-side screw body 30 has a shaft center side (center side) protruding toward the shaft-side screw body 20 side (first screw portion 22 side). It becomes an inclined surface. More specifically, the head-side contact surface 38 has a shape that approximates or matches the surface of the partial sphere. Similarly, the bottom surface of the housing recess 14 of the plate 10 has an inclined surface in which the axial center side (center side) is concave on the axial side screw body 20 side (first screw portion 22 side). Has a shape that approximates or coincides with the surface of a partial sphere having the same radius as the head-side contact surface 38.

  As a result, as shown in FIG. 8B, even when the axial screw body 20 is fixed to the rib in a state of being inclined with respect to the plate 10, the head side contact of the head screw body 30 is performed. The surface 38 and the receiving recess 14 of the plate 10 can be brought into close contact with each other. At the same time, the looseness of the head-side screw body 30 can be suppressed by the frictional force of both. In the third embodiment, the case where the head-side contact surface 38 has a partial spherical shape is illustrated, but the present invention is not limited to this, and for example, a partial conical shape can be selected as appropriate.

  The bone fixing structures according to the first to third embodiments of the present invention have been described above. However, the present invention is not limited to these embodiments, and various modifications can be made without departing from the gist of the present invention. Can be added. For example, as shown in FIG. 9, it is also preferable to form a through hole 90 in the center of the shaft side screw body 20 in the longitudinal direction. If it does in this way, it will become possible to insert a K wire in this through-hole 90, and to perform a fastening operation | work.

DESCRIPTION OF SYMBOLS 1 Bone fixing structure 10 Plate 12A, 12B Insertion hole 14 Receiving recessed part 20 Shaft side screw body 22 1st screw part 24 2nd screw part 26 Shaft side tool coupling | bond part 27 Expansion part 27A Shaft side contact surface 30 Head side screw body 34 Connecting screw part 36 Head side tool coupling part 38 Head side contact surface 90 Through hole

Claims (8)

A shaft-like screw body that is a rod-like member inserted into a bone, wherein a first screw portion that engages with the bone is formed, and a second screw portion is formed in the vicinity of an end portion exposed from the bone;
A head-side screw body that is screwed with the second screw portion of the shaft-side screw body and extends in a radial direction with respect to the shaft-side screw body,
The head-side screw body has a head-side contact surface that contacts the bone,
Bone fixation structure. The shaft side screw body is
In the vicinity of the end where the second threaded portion is formed, a shaft side expansion portion that extends in the radial direction is formed, and the shaft side expansion portion has a shaft side contact surface that contacts the bone,
The head-side contact surface of the head-side screw body is in contact with the bone at a radially outer side than the shaft-side contact surface,
The bone fixing structure according to claim 1. A rod-like member inserted into a bone and a hole of a plate attached to the bone, wherein a first screw portion that engages with the bone is formed, and a second screw portion is formed in the vicinity of an end portion exposed from the bone A shaft-side screw body,
A head-side screw body that is screwed with the second screw portion of the shaft-side screw body and extends in a radial direction with respect to the shaft-side screw body,
The head-side screw body has a head-side contact surface that contacts a surface of the plate opposite to the bone,
Bone fixation structure. The shaft side screw body is
In the vicinity of the end where the second threaded portion is formed, a shaft-side extension portion that extends in the radial direction is formed, and the shaft-side extension portion is a shaft that contacts the surface of the plate opposite to the bone. Having a side abutment surface,
The head-side contact surface of the head-side screw body is in contact with the plate at a radially outer side than the shaft-side contact surface,
The bone fixing structure according to claim 3. The plate is interposed so as to be slidable in the axial direction with respect to the shaft side screw body,
The head-side contact surface presses the plate against the bone side according to the screwing degree of the head-side screw body and the shaft-side screw body, thereby increasing the coupling force between the plate and the bone. Characterized by the
The bone fixing structure according to claim 3 or 4. The head-side contact surface of the head-side screw body is an inclined surface in which the axial center side is convex toward the first screw portion side,
The bone fixation structure according to any one of claims 1 to 5. The lead of the second screw part in the shaft side screw body is smaller than the lead of the first screw part,
The bone fixing structure according to any one of claims 1 to 6. A through-hole into which a K wire is inserted is formed over the entire longitudinal direction of the shaft-side screw body,
The bone fixation structure according to any one of claims 1 to 7.

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