JP6549774B2 - guide pin - Google Patents

Description

  The present invention relates to a guide pin.

  For reduction of a fractured bone fragment and drilling of a bone, generally, a Kirschner steel wire (commonly known as K wire) is used (see, for example, Non-Patent Document 1). Also known is a threaded Kirschner wire for maintaining bone penetration. Such Kirschner wire is commercially available at low cost and often used single-use (disposable).

On the other hand, in the case of revision surgery for loosening of the femoral stem after total hip arthroplasty, if the femur is thinning, IBG procedure (Impaction Bone Grafting) may be used. In the IBG procedure, a guide pin is used as a guide in filling the bone marrow cavity of the thinned femur with bone fragments. The guide pin is fixed to the center of the medullary cavity by using a cement plug or by directly inserting the guide pin into the bone cement when bone cement remains at the distal end of the medullary canal.

  By the way, when the above-mentioned commercially available Kirschner steel wire is used as a guide pin for the IBG procedure, problems such as a short length, a nonconforming diameter to a combination device, low strength and pliability, etc. occur. Therefore, guide pins for penetrating bone cement in the IBG procedure are individually designed for the IBG procedure, and are repeatedly used because of the high cost of single-piece manufacturing.

  Here, when designing a guide pin for an IBG procedure, if the configuration of a commercially available Kirschner steel wire is adopted as it is, there are the following problems. The shape of the general tip of a Kirschner wire, including a threaded Kirschner wire, has a nearly common configuration. Specifically, the tip end portion has a triangular pyramid shape, and in the case of a threaded Kirschner steel wire, the outer peripheral portion in the vicinity of the tip portion is threaded. When the guide pin for IBG procedure is designed by adopting such a Kirschner wire configuration as it is, the bone cement is cut at the tip of the triangular pyramid and the bone cement is cut when cutting the bone cement at the edge of the triangular pyramid. There is a problem that it is difficult. In addition, when the tip is dulled and re-polished due to repeated use, there is also a problem that the re-polishing load is large because it is necessary to reshape the three planes constituting the triangular pyramid.

"YDM Kirschner steel wire", [online], YDM Co., Ltd. [search on January 14, 2016], Internet <URL: http://www.ydm.co.jp/pdf/86443.pdf>

  An object of the present invention is to provide a guide pin which is excellent in machinability with respect to bone cement and which is easy to be re-polished.

  As a result of intensive studies to solve the above problems, the inventor has found a solution having the following constitution, and has completed the present invention.

(1) A plurality of groove portions located at the tip end portion and extending along the central axis, and a surface portion positioned between groove portions adjacent to each other among the plurality of groove portions, The guide pin according to claim 1, wherein each of the plurality of grooves is convex toward the central axis in a cross-sectional view perpendicular to the central axis.

  (2) The guide pin according to (1), wherein in the cross-sectional view, each of the plurality of groove portions has a curved shape that is convex toward the central axis side.

  (3) The guide pin according to (1) or (2), wherein in the cross-sectional view, each of the plurality of groove portions has a circular arc shape convex toward the central axis.

  (4) The guide pin according to any one of (1) to (3), wherein the number of the plurality of groove portions is three.

  (5) The guide pin according to any one of (1) to (4), wherein in the cross-sectional view, the surface portion is flat or curved outward convex.

  (6) The guide pin according to any one of (1) to (4), wherein in the cross-sectional view, the surface portion is an outwardly convex arc shape having the center axis as a center.

  (7) The guide pin according to any one of (1) to (6), further including a screw portion located on the outer peripheral portion on the tip end side.

  (8) The guide pin according to any one of the above (1) to (7), which is for an IBG procedure.

  ADVANTAGE OF THE INVENTION According to this invention, while it is excellent in the cutting property with respect to a bone cement, it is effective in the regrinding being easy.

It is a perspective view showing a guide pin concerning one embodiment of the present invention. It is an expanded sectional view which shows the front-end | tip part of the guide pin shown in FIG.

  Hereinafter, a guide pin according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

  The guide pin 1 of the present embodiment shown in FIG. 1 is a substantially cylindrical member extending along a central axis S for the IBG procedure. The central axis S is an axis passing through between the front end portion 1a and the rear end portion 1b of the guide pin 1, and means an axis serving as a rotation axis when the guide pin 1 is rotated.

  The guide pin 1 of the present embodiment is located between the plurality of grooves 2 located at the tip 1 a and extending along the central axis S and the grooves 2 adjacent to each other among the plurality of grooves 2. And a surface portion 3 located on the Then, in a cross-sectional view perpendicular to the central axis S shown in FIG. 2 (hereinafter sometimes referred to as “cross-sectional view”), the plurality of groove portions 2 are all convex on the central axis S side. According to these configurations, the minus rake angle θ can be reduced, in other words, the minus rake angle θ can be brought close to plus, and as a result, the machinability with respect to bone cement can be improved. The rake angle θ is the angle between the groove 2 or its extension and the perpendicular L perpendicular to the workpiece 100 (bone cement) through the intersection 4 between the groove 2 and the surface 3 in a cross sectional view. Shall be meant. The rake angle θ can be, for example, 30 to 0 °. The rake angle θ of the present embodiment is 10 °, but is not limited thereto.

  Further, according to the above-mentioned configuration, when it is necessary to polish the small-area surface portion 3 along the circumferential direction A of the guide pin 1 when the tip portion 1a is dulled and re-polished due to repeated use, the triangular pyramid is The regrinding load can be made smaller than in the above-described Kirschner wire configuration in which three planes to be configured must be reworked respectively, and regrinding can be easily performed.

  On the other hand, in the present embodiment, the plurality of grooves 2 have the following configuration. That is, as shown in FIG. 1, each of the plurality of groove portions 2 linearly extends along the central axis S. Also, the plurality of grooves 2 are all located apart from each other. In other words, none of the plurality of grooves 2 merge.

  The grooves 2 cut into bone cement at the tip 1a of the guide pin 1 and function as rake faces when cutting the bone cement at the intersection 4 of the groove 2 and the surface 3 which are edges. In the present embodiment, in the cross-sectional view shown in FIG. 2, each of the plurality of groove portions 2 has a curved shape convex toward the central axis S side. According to such a configuration, the function as the rake face of the groove 2 can be improved.

  Examples of the above-described curved shape include a parabolic shape, an elliptical arc shape, and an arc shape. In the present embodiment, when viewed in cross section, each of the plurality of groove portions 2 has a circular arc shape that is convex toward the central axis S side. According to such a configuration, in addition to the effect of improving the function as the rake face of the groove portion 2, the effect of being excellent in processability when producing the guide pin 1 is also obtained.

  In the present embodiment, the number of grooves 2 is three. The number of grooves 2 and the number of surface portions 3 are the same. Therefore, in the present embodiment, the number of the surface portions 3 is also three, similarly to the number of the groove portions 2. Then, each of the three groove portions 2 and the three surface portions 3 is positioned so as to be 120 ° rotationally symmetric with respect to the central axis S. In addition, the number of each of the groove part 2 and the surface part 3 is not limited to three, For example, it is also possible to make it four etc.

  In the cross sectional view, the surface portion 3 may be flat or curved outward convex. As the curvilinear shape, the same shape as exemplified in the groove portion 2 described above can be mentioned. In the present embodiment, in cross section, the surface portion 3 has an outwardly convex arc shape centering on the central axis S. In addition, as above-mentioned, as for the some groove part 2 of this embodiment, all are circular arc shape convex on the central axis S side in a cross sectional view. Therefore, it can be said that the guide pin 1 has a configuration in which a part of the cone including the edge of the triangular pyramid at the tip of the conventional Kirschner wire is cut away by a concave curved surface having a circular arc shape in cross section.

  The guide pin 1 can have, for example, a diameter of 2 to 5 mm, a total length of 200 to 500 mm, and a length of the tip 1 a of 2 to 9 mm, but is not limited thereto. Moreover, as a constituent material of the guide pin 1, for example, stainless steel (SUS) or the like can be mentioned. Examples of SUS include SUS316, SUS630, and SUS420J2. When employing SUS630 or SUS420J2, heat treatment may be performed.

  Although the preferred embodiments according to the present invention have been illustrated above, it is needless to say that the present invention is not limited to the above-described embodiments, and can be arbitrary without departing from the scope of the present invention.

  For example, in the embodiment described above, the groove 2 has a circular arc shape convex on the central axis S side in a cross sectional view, but the groove 2 has another shape other than the circular arc as long as the groove 2 is convex on the central axis S side Can be As another shape, for example, a combination of a straight line and an arc may be mentioned.

  The guide pin 1 may be threaded at the outer peripheral portion 5 (see FIG. 1) on the tip 1a side. In other words, the guide pin 1 may further include a screw portion located on the outer peripheral portion 5 on the tip portion 1a side.

  In the above embodiment, the case where the guide pin 1 is for IBG procedure was described as an example, but the guide pin 1 is not limited to the IBG procedure, and may be used as a guide pin for other applications. it can.

DESCRIPTION OF SYMBOLS 1 Guide pin 1a Tip part 1b Rear end part 2 Groove part 3 Surface part 4 Crossing part 5 Outer peripheral part S Central axis 100 Work material

Claims (8)

A plurality of grooves located at the tip and extending along the central axis;
And a surface portion positioned between adjacent groove portions among the plurality of groove portions,
The guide pin according to claim 1, wherein each of the plurality of groove portions is convex toward the central axis in a cross-sectional view perpendicular to the central axis.   The guide pin according to claim 1, wherein in the cross-sectional view, each of the plurality of groove portions has a curved shape convex toward the central axis side.   The guide pin according to claim 1, wherein in the cross-sectional view, each of the plurality of groove portions has an arc shape convex toward the central axis side.   The guide pin according to any one of claims 1 to 3, wherein the number of the plurality of groove portions is three.   The guide pin according to any one of claims 1 to 4, wherein in the cross-sectional view, the surface portion is flat or curved outward convex.   The guide pin according to any one of claims 1 to 4, wherein in the cross-sectional view, the surface portion is an outwardly convex arc shape having the center axis as a center.   The guide pin according to any one of claims 1 to 6, further comprising a screw portion located on an outer peripheral portion on the tip end side. The guide pin according to any one of claims 1 to 7, which is for IBG procedures.