JP2008206677A - Prosthetic object for living body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prosthetic object for a living body, which is easily installed and is excellent in initial fixation and long-term fixation. <P>SOLUTION: The prosthetic object 10 for the living body is provided with a stem part 12 to be inserted into the marrow cavity 6, the stem part 12 is provided with a straight part 20 whose distal end side is in a straight shape and a tapered part 22 whose root side is tapered toward the distal end side, and a rough surface part 24 is formed on the tapered part 22. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a bioprosthesis used for prosthesis of a bone defect or excision due to an accident or disease.

  Various types of prosthetics have been proposed as prosthetics for prosthetic bone defects or excised parts caused by accidents or diseases.

  For example, when inserting a generally straight stem into an insertion hole formed in the bone marrow cavity and fixing the bioprosthesis to the bone using cement, use a rewell, surge air tome, file, etc. However, it is necessary to provide a recess corresponding to the antirotation portion on the osteotomy surface, but in order to form a recess having a desired shape, a high degree of resection is required. Further, the prosthesis has a problem that it is easily damaged by stress concentration at the root of the stem portion because it has a complicated shape with a protruding rotation stop at the root of the stem portion.

  In addition, the straight stem portion is inserted into the bone marrow cavity so that the bone is sandwiched between the opposing stem portion and the auxiliary plate, and the fixing bolt is inserted through the through-hole of the auxiliary plate, and the bottomed bolt hole of the stem portion is inserted. And a method for firmly fixing the bioprosthetic body to the bone without using cement (see, for example, Patent Document 1).

  The screw fixing method using the auxiliary plate described above can resist the rotation of the auxiliary plate of the bioprosthetic body with respect to the bone, so that the bioprosthetic body is initially firmly fixed to the bone. It has the excellent feature of being able to However, the fixing method has a problem that it cannot be screwed and fixed unless accurate drilling is performed. Furthermore, during long-term use, there is a lack of irritation to the bone in low-load parts other than the bolted parts that are high-load parts to the bone, that is, typically near the osteotomy surface where the stem part is inserted. Therefore, bone resorption occurs. Then, the bone in the region near the osteotomy surface where bone resorption has occurred becomes brittle, and the prosthesis is displaced or rattled. As a result, since the support region for supporting the stem portion is limited to the bolt screwing portion, the load on the bioprosthesis is concentrated on the bolt screwing portion. There is a problem that the stem part is broken.

  In any of the fixing methods, in addition to the need to well form the concavity for the rotation preventing portion and the hole for screwing, the diameter of the stem portion of the bioprosthesis has a hole diameter approximately equal to or larger than that. Since the insertion hole is formed in the bone marrow cavity and the stem portion with a substantially straight shape is simply inserted into the bone marrow cavity insertion hole, in the long term, near the osteotomy surface of the bone marrow cavity insertion hole There is a problem in the region that the prosthesis is displaced or loosened due to bone resorption caused by the lack of bone stimulation described above.

JP-A-11-47170

  Therefore, a technical problem to be solved by the present invention is to provide a bioprosthesis that is easy to install and excellent in initial fixation and long-term fixation.

Means and actions / effects for solving the problem

  In order to solve the above technical problem, according to the present invention, the following bioprosthesis is provided.

That is, the bioprosthesis according to the present invention is
A bioprosthesis having a stem portion inserted into the bone space,
The stem portion is
A straight portion having a straight shape on the tip side, and
A taper portion whose base side is tapered toward the tip side, and
A rough surface portion is formed on the tapered portion.

  According to the above configuration, the living body prosthesis according to the present invention only needs to form a taper hole in the bone space, and a highly skilled technique such as a concavity for convolution and a screw hole is required. In addition to being unnecessary, the initial fixing is ensured by the minute unevenness of the rough surface portion formed in the tapered portion and the press-fitting fixing by the tapered shape, and the rough surface portion formed in the tapered portion is also guaranteed. Long-term fixation is assured by promoting bone growth with minute irregularities. Therefore, the bioprosthesis can be fixed in the bone space in an initial and long term.

  The boundary line that defines the boundary between the straight portion and the tapered portion of the stem portion is a unique portion that is inferior in mechanical strength in order to form a bending variation line when viewed microscopically. There is a possibility that the strength is lowered by exposing such a unique portion to various treatments (high-temperature heat treatment, chemical treatment, etc.) in forming the rough surface portion. Therefore, it is preferable that the leading end side of the rough surface portion is separated from the boundary line that defines the boundary between the straight portion and the tapered portion.

  If the separation distance on the front end side of the rough surface portion is short, damage will occur during various processing. If the separation distance on the front end side of the rough surface portion is long, the rough surface area of the rough surface portion becomes small, so that the rough surface area contributing to fixation is reduced. Therefore, the separation distance on the front end side of the rough surface portion is preferably about 2 to about 6 mm, more preferably about 4 mm.

  The rough surface can be formed by coating with metal beads or metal fiber mesh, or by etching, milling, embossing, sandblasting, machining, or spraying. From the viewpoint of the difficulty of occurrence, it is preferable to form by spraying. Although plasma spraying or arc spraying is used for the spraying, arc spraying is more preferable because the sprayed material is difficult to fall off.

  From the viewpoint of adhesion to the base material, it is preferable that the spray material used as the rough surface portion is composed of a material substantially the same as the base material of the stem portion.

  From the viewpoint of biocompatibility, in-vivo stability, and bone growth, the spray material of the rough surface portion is pure titanium or a titanium alloy.

  From the viewpoint of stronger bone adhesion, a calcium phosphate compound is formed on the outermost surface of the rough surface portion.

  If the rough surface portion protrudes from the surface of the base material of the bioprosthesis in which the rough surface portion is formed, the thickness of the rough surface portion becomes a step when pressed into the bone marrow cavity, and a step catching effect is obtained. If the protruding amount of the rough surface portion is small, the step catching effect is reduced. If the protruding amount of the rough surface portion is large, the resistance at the time of press-fitting may be excessive and installation may be impossible. Therefore, the thickness of the rough surface portion by spraying is preferably about 0.3 to about 0.7 mm, and more preferably about 0.5 mm. Further, the average surface roughness (Ra) of the rough surface portion by spraying is 30 to 60 μm.

  When the taper angle of the taper portion is small, the wedge press-fit effect due to the taper becomes small. When the taper angle of the taper portion is large, the hole diameter at the osteotomy surface increases and the amount of bone cut increases, so that the surrounding bone that maintains the stem is easily broken in a thin bone patient. Therefore, the taper angle of the taper portion is preferably about 5 degrees to about 9 degrees, and more preferably about 7 degrees.

  In order to prevent the rotation of the stem, it is preferable that the cross section perpendicular to the axial direction of the tapered portion is a polygon.

  In particular, it is more preferable that the polygon of the cross section of the tapered portion is a hexagon.

  Hereinafter, an embodiment of a bioprosthesis 10 according to the present invention will be described in detail with reference to FIGS.

  FIG. 1 is a front view of a bioprosthesis 10 according to an embodiment of the present invention. FIG. 2 is an enlarged view of a main part of the bioprosthesis 10 shown in FIG. FIG. 3 is a view for explaining a state in which the bioprosthesis 10 shown in FIG. 1 is replaced with the proximal end of the tibia. (A) shows the determination of the excision position of the proximal end of the tibia. (B) shows resection of the proximal tibia. (C) shows straight reaming. FIG. 4 is a view for explaining a state in which the bioprosthesis 10 shown in FIG. 1 is replaced with the proximal end of the tibia. (D) shows taper reaming of the proximal tibia. (E) shows the insertion of the bioprosthesis 10 into the bone marrow cavity 6 of the tibia 2. (F) shows confirmation of the rotation alignment by the alignment bar 42. FIG. 5 is a view for explaining a state in which the bioprosthesis 10 shown in FIG. 1 is replaced with the proximal end of the tibia. (G) shows the placement of the bioprosthesis 10 in the bone marrow cavity 6 of the tibia 2 using the impactor 40 and the hammer 50. FIG. 6 is a diagram for explaining a state in which the bioprosthesis 10 shown in FIG. 1 is replaced with the proximal end of the tibia. (H) indicates mounting of the component 60. (I) shows screwing of the component 60. (J) shows completion of tibial replacement. FIG. 7 is a cross-sectional view illustrating the formation of the tapered portion 22 in the bone marrow cavity 6. FIG. 8 is a cross-sectional view for explaining how the bioprosthesis 10 is inserted into the bone marrow cavity 6.

  As shown in FIG. 1, the bioprosthesis 10 includes a stem portion 12 that is inserted into the bone marrow cavity 6, a diaphysis portion 18 that is integrally formed with the stem portion 12 and abuts against the osteotomy surface 4, and a bone And a fitting portion 14 that is integrally formed with the trunk portion 18 and has a connection screw hole 16. The base material of the bioprosthesis 10 is a Ti alloy (for example, Ti-6Al-4V, Ti-15Mo-5Zr-3Al, Ti-6Al-2Nb-1Ta as a biomedical Ti alloy) or a Co-Cr-Mo alloy. It is made of a material with high biological safety such as a metal such as stainless steel or a ceramic such as alumina.

  The stem portion 12 having a generally cylindrical shape has a straight portion 20 having a straight shape on the tip portion 12b side, and a tapered shape having a base portion 12a side toward the tip portion 12b side. The taper part 22 is provided. The straight part 20 is a smooth surface. As will be described later, the tapered portion 22 is composed of a rough surface that increases the bonding force with the bone and a smooth surface.

  When the taper angle of the taper portion 22 is small, the wedge press-fit effect due to the taper is reduced. When the taper angle of the taper portion 22 is large, the hole diameter at the osteotomy surface 4 is increased and the amount of bone cut increases, so that the surrounding bone that maintains the stem is easily broken in a thin bone patient. Therefore, the taper angle of the taper portion 22 is preferably about 5 degrees to about 9 degrees, and more preferably about 7 degrees.

  On the surface of the taper portion 22, a material substantially the same as the base material of the stem portion 12 is sprayed, so that the surface is roughened, and a sprayed portion 24 as a rough surface portion is formed. . For example, if the base material of the stem portion 12 is a Ti alloy, pure Ti or the same or similar Ti alloy as the base material of the stem portion 12 is arc-sprayed. Alternatively, even when the base material of the stem portion 12 is a Co—Cr—Mo alloy, pure Ti or a similar Ti alloy is arc-sprayed. That is, from the viewpoint of bone growth, pure Ti or Ti alloy is suitable as the sprayed portion 24 as the rough surface portion.

  Furthermore, in order to accelerate the generation of new bone, it is preferable that a calcium phosphate compound such as hydroxyapatite is formed on the outermost surface of the spray portion 24 as a rough surface portion by plasma spraying or the like. Note that the sprayed portion 24 as a rough surface portion is suitable from the viewpoint that micro scratches on the surface that cause a decrease in strength are less likely to occur, but the rough surface portion is a rough surface having fine irregularities on the surface. Therefore, it can be formed by etching, milling, sandblasting, embossing, machining, or the like.

  The boundary line 28 that defines the boundary between the straight part 20 and the taper part 22 of the stem part 12 forms a bending variation line when viewed microscopically, and is a unique part that is inferior in mechanical strength. It is. When such a unique portion is exposed to various treatments (high-temperature heat treatment, chemical treatment, etc.) in forming the sprayed portion 24, there is a possibility that the strength is lowered. Therefore, as shown in FIG. 2, the end portion 12b side of the above-described sprayed portion 24 is separated from the boundary line 28 that defines the boundary between the straight portion 20 and the tapered portion 22 and forms a singular portion. (The length of the taper portion 22> the range of the sprayed portion 24). Accordingly, in the tapered portion 22, the predetermined region is a rough surface, the other region is a smooth surface, and the non-spray surface 26 is provided between the tip portion 12 b side of the spray portion 24 and the boundary line 28. That is, a smooth surface exists.

  If the separation distance between the tip 12b side of the sprayed portion 24 and the boundary line 28 is short, damage will be caused by various processes during spraying. If the distance between the front end side 12b of the sprayed part 24 and the boundary line 28 is long, the roughened surface area of the sprayed part 24 becomes small, so that the roughened surface area contributing to fixing is reduced. Therefore, the separation distance between the distal end portion 12b side of the sprayed portion 24 and the boundary line 28 is preferably about 2 to about 6 mm, and more preferably about 4 mm.

  Moreover, when the spraying part 24 protrudes from the surface of the base material of the living body prosthesis 10 in which the spraying part 24 is formed, when the thickness of the spraying part 24 is press-fit into the bone marrow cavity 6 A step catching effect can be obtained. If the protrusion amount of the sprayed part 24 is small, the step catching effect is reduced. If the amount of protrusion of the sprayed part 24 is large, the resistance at the time of press-fitting may become excessive and installation may become impossible. Therefore, the thickness of the sprayed part 24 is preferably about 0.3 to about 0.7 mm, and more preferably about 0.5 mm. Further, the average surface roughness (Ra) of the rough surface portion 24 is 30 to 60 μm.

  Next, a usage mode of the living body prosthesis 10 will be described with reference to FIGS. In the following embodiment, the case where the bioprosthesis 10 is applied to the tibia 2 will be described. However, the bioprosthesis 10 according to the present invention can also be applied to the femur.

  As shown in FIG. 3A, the affected part on the proximal side of the tibia 2 that needs to be removed due to an accident, disease, or the like is removed by the oscillator 80. As shown in FIG. 3B, a bone space 6 appears on the osteotomy surface 4 of the tibia 2 from which the affected part has been excised. As shown in FIG. 3C, a straight reamer 82 having an outer diameter into which the straight portion 20 of the stem portion 12 can be inserted is inserted into the bone space 6 and the straight hole 8 is drilled. .

  As shown in FIG. 4D, a taper reamer 84 having a tapered portion with a tapered tip is inserted into the straight hole 8 of the bone space 6 and taper drilling is performed. As a result, the bone space 6 of the tibia 2 is formed with a taper hole 9 having a straight hole 8 on the distal side and an enlarged diameter on the proximal side, as shown in FIG. For example, the diameter of the straight hole 8 is 8 to 15 mm, the length of the tapered hole 9 is 25 mm, and the taper angle is about 7 degrees.

  The stem portion 12 of the living body prosthesis 10 is inserted into the holes 8 and 9 formed in the bone space 6 (FIG. 4E), and the impactor 40 is fitted to the living body prosthesis 10. 14 and the living body prosthesis 10 is positioned using the alignment bar 42 of the impactor 40 ((F) of FIG. 4). Then, with the alignment bar 42 attached, the impactor 40 is hit with the hammer 50 (FIG. 5G), and the stem portion 12 is press-fitted into the holes 8 and 9 of the bone space 6 (FIG. 8).

  After the impactor 40 is removed, the component 60 is mounted on the fitting portion 14 of the bioprosthesis 10 (FIG. 6H), and the through hole 62 of the component 60 and the connection screw hole 16 of the fitting portion 14 are connected. After confirming that the axes coincide with each other ((I) in FIG. 6), the component 60 and the bioprosthetic body 10 are integrally screwed with a fixing screw 66 ((J) in FIG. 6). Used as a tibial component.

  Then, the femoral component (femoral condyle) on the femur side is connected to the tibial component via the hinge shaft, thereby forming an artificial knee joint.

  In the above embodiment, the cross section perpendicular to the axial direction of the tapered portion 22 of the stem portion 12 is circular, but in order to prevent the stem portion 12 from rotating, the cross section perpendicular to the axial direction of the tapered portion 22 is used. It is preferably a polygon. In particular, the polygon of the cross section of the taper portion 22 is more preferably a hexagon.

It is a front view of the prosthetic body for living bodies concerning one embodiment of the present invention. It is a principal part enlarged view of the prosthetic body for biological bodies shown in FIG. It is a figure explaining a mode that the bioprosthesis body shown in FIG. 1 is substituted to the proximal part of a tibia. (A) shows the determination of the excision position of the proximal end of the tibia. (B) shows resection of the proximal tibia. (C) shows straight reaming. It is a figure explaining a mode that the bioprosthesis body shown in FIG. 1 is substituted to the proximal part of a tibia. (D) shows taper reaming of the proximal tibia. (E) shows the insertion of the bioprosthesis into the tibial bone marrow cavity. (F) shows confirmation of the rotation alignment by the alignment bar. It is a figure explaining a mode that the bioprosthesis body shown in FIG. 1 is substituted to the proximal part of a tibia. (G) shows the placement of the bioprosthesis in the tibia bone marrow cavity using an impactor and a hammer. It is a figure explaining a mode that the bioprosthesis body shown in FIG. 1 is substituted to the proximal part of a tibia. (H) indicates component mounting. (I) shows screwing of the component. (J) shows completion of tibial replacement. It is sectional drawing explaining formation of the taper part in a bone marrow cavity. It is sectional drawing explaining a mode that the prosthetic body for biological bodies is inserted in a bone marrow cavity.

Explanation of symbols

2: Tibia 4: Osteotomy surface 6: Bone marrow cavity 8: Straight hole 9: Tapered hole 10: Prosthetic body 12: Stem portion 12a: Root portion 12b: Tip portion 14: Fitting portion 16: Connection screw hole 18: Skeletal part 20: Straight part (smooth surface)
22: Tapered portion 24: Sprayed portion (rough surface)
26: Non-sprayed part (smooth surface)
28: boundary 40: impactor 42: alignment bar 50: hammer 60: component 62: through hole 66: fixing screw 80: oscillator 82: straight reamer 84: taper reamer

Claims (11)

A bioprosthesis having a stem portion inserted into the bone space,
The stem portion is
A straight portion having a straight shape on the tip side, and
A taper portion whose base side is tapered toward the tip side, and
A prosthetic body for living body, wherein a rough surface portion is formed on the tapered portion.   The prosthetic body for living body according to claim 1, wherein a distal end side of the rough surface portion is separated from a boundary line defining a boundary between the straight portion and the tapered portion.   The living body prosthesis according to claim 2, wherein a separation distance on a front end side of the rough surface portion is about 4 mm.   The living body prosthesis according to claim 1, wherein the rough surface portion is formed by spraying.   The living body prosthesis according to claim 1, wherein the spraying of the rough surface portion is made of a material substantially the same as the base material of the stem portion.   The bioprosthesis according to claim 1, wherein the spray material of the rough surface portion is pure titanium or a titanium alloy.   The bioprosthesis according to claim 1, wherein a calcium phosphate compound is formed on the outermost surface of the rough surface portion.   The living body prosthesis according to claim 4, wherein a thickness of the rough surface portion by the spraying is about 0.5 mm.   2. The bioprosthesis according to claim 1, wherein the taper portion has a taper angle of about 7 degrees.   The bioprosthesis according to claim 1, wherein a cross section perpendicular to the axial direction of the tapered portion is a polygon.   The bioprosthesis according to claim 10, wherein a polygon of a cross section of the tapered portion is a hexagon.

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