Artificial joint stems and artificial hip joints

Abstract

To provide an artificial joint stem.SOLUTION: An artificial joint stem 100 comprises a base 10 extending in a vertical direction when a proximal side in a human body is directed in an upward direction during use, and a coating 20 formed on a portion of the base, and including a calcium phosphate-based material and an antibacterial material. Boundary lines on the base defined by the presence or absence of the coating include a first boundary line 1 located on a lower side of the base with respect to the coating. The first boundary line is located so as to intersect with the vertical direction. A component of the first boundary line along the vertical direction is smaller than a component of the base along a width direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a stem for a prosthetic joint. [Background technology]

[0002] The use of bioimplants for the treatment of both bone injuries and diseases is constantly expanding with the increase in the active and elderly population. Among these, bioimplants that are coated with antibacterial agents and have good bone adhesion properties are known.

[0003] For example, Patent Document 1 describes a coating for medical implants that contains a bone bonding agent as a part thereof and also contains an antibacterial metal agent containing silver. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2011-512959 Summary of the Invention

[0005] The artificial joint stem according to the present disclosure comprises a base body extending in the vertical direction when the proximal side in the human body when in use is defined as the upper direction, and a coating containing a calcium phosphate material and an antibacterial material disposed on a portion of the base body. The boundary line on the base body defined by the presence or absence of the coating includes a first boundary line located on the lower side of the base body relative to the coating. The first boundary line is located so as to intersect with the vertical direction. The component of the first boundary line along the vertical direction is smaller than the component along the width direction of the base body. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG. [Figure 2] 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG. [Figure 3] 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG. [Figure 4] 1 is a schematic diagram showing a cross section of an artificial joint stem according to one embodiment. FIG. [Figure 5] 1 is a schematic diagram showing a cross section of an artificial joint stem according to one embodiment. FIG. [Figure 6] 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG. [Figure 7] 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG. [Figure 8] 1A to 1C are process diagrams showing a method for manufacturing an artificial joint stem according to one embodiment. [Figure 9] FIG. 1 is a schematic diagram showing an artificial hip joint according to one embodiment. [Figure 10] 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG. [Figure 11] 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG. [Figure 12] 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG. [Figure 13] 1 is a schematic diagram showing a cross section of an artificial joint stem according to one embodiment. FIG. [Figure 14] 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG. [Figure 15] 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG. [Figure 16] 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0007] An embodiment will be described in detail below. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less."

[0008] [1. Stems for artificial joints] First, referring to FIG. 1, the configuration of an artificial joint stem 100 according to one embodiment will be described. The artificial joint stem 100 includes a base 10 extending vertically, with the proximal side in the human body being considered as the upper side when in use, and a coating 20 disposed on a portion of the surface of the base 10. The upper side of the base 10 corresponds to the proximal side in the human body, and the lower side corresponds to the distal side. The coating 20 contains a calcium phosphate-based material and an antibacterial material. The artificial joint stem 100 also has an embedded portion 40 that is embedded in bone and an exposed portion 50 that is exposed from the bone. In FIG. 1, the embedded portion 40 has the coating 20 formed on a region close to the exposed portion 50, while the region far from the exposed portion 50 is exposed from the coating 20. The calcium phosphate-based material improves adhesion to bone. The antibacterial material reduces bacterial adhesion and proliferation.

[0009] Here, the coating 20 is disposed on a portion of the surface of the base 10. That is, another portion of the surface of the base 10 is exposed from the coating 20. For example, if the entire surface of the artificial joint stem 100 is covered with a coating containing a bone-bonding agent and an antibacterial metal agent, it is difficult to control the adhesion of the artificial joint stem 100 to the bone. In this case, when the artificial joint stem needs to be removed after surgery, removal may be difficult. For example, there is a risk that the embedded portion 40 may excessively adhere to the bone via the coating. If the base 10 has an area covered with the coating 20 and an area exposed from the coating 20, excessive adhesion to the bone can be reduced. In other words, it is possible to achieve both adhesion to the bone and antibacterial properties.

[0010] The boundary on the substrate 10 defined by the presence or absence of the coating 20 includes a first boundary line 1 located below the substrate 10 with respect to the coating 20. The first boundary line 1 is located so as to intersect with the vertical direction. In other words, not all of the first boundary line 1 is parallel to the vertical direction. The component of the first boundary line 1 along the vertical direction is smaller than the component along the width direction of the substrate 10.

[0011] The components of the first boundary line 1 will be further described with reference to FIG. 2. In FIG. 2, the vertical direction of the base 10 is represented as the Y-axis direction, and the width direction of the base 10 is represented as the X-axis direction. The width direction of the base 10 can also be considered to be a direction perpendicular to the vertical direction. FIG. 2 can also be considered to be a planar view from a direction perpendicular to the XY plane, i.e., the Z-axis direction. Consider the line α connecting both ends of the first boundary line 1 in FIG. 2. When the line α is parallel to the X-axis, it can be said that the first boundary line 1 has only a component along the width direction of the base 10. When the line α is represented as a line with a slope on the XY coordinate system, it can be said that the first boundary line 1 has both a component along the vertical direction of the base 10 and a component along the width direction of the base 10. In this specification, the phrase "the component along the vertical direction of the first boundary line 1 is smaller than the component along the width direction of the base 10" means that the absolute value of the slope of the line α is less than 1. In this case, it is possible to reduce friction in the shear direction that occurs at the first boundary line 1, thereby reducing peeling of the coating 20. Furthermore, the phrase "the component of the first boundary line 1 along the vertical direction is smaller than the component along the width direction of the base 10" also includes the case where the first boundary line 1 has only a component along the width direction of the base 10.

[0012] The boundary line may include a second boundary line 2 located above the substrate 10 relative to the coating 20. The second boundary line 2 may also be positioned so as to intersect with the vertical direction. Like the first boundary line 1, the second boundary line 2 may have a smaller vertical component than its component along the width direction of the substrate 10. Alternatively, unlike the first boundary line 1, the second boundary line 2 may have a larger vertical component than its component along the width direction of the substrate 10. In FIG. 2 , the line connecting both ends of the second boundary line 2 is designated as line β. The phrase "the vertical component of the second boundary line 2 is smaller than its component along the width direction of the substrate 10" means that the absolute value of the slope of line β is less than 1. On the other hand, the phrase "the vertical component of the second boundary line 2 is larger than its component along the width direction of the substrate 10" means that the absolute value of the slope of line β is greater than 1. The vertical component of the second boundary line 2 may also be larger than the vertical component of the first boundary line 1.

[0013] The lengths of the first boundary line 1 and the second boundary line 2 may be the same, or one may be larger than the other. In this specification, "length of the first boundary line 1" means the total length of the first boundary line 1 that encircles the base 10. The same applies to "length of the second boundary line 2". For example, as shown in Figure 1, the length of the first boundary line 1 may be greater than the length of the second boundary line 2. On the other hand, the length of the first boundary line 1 may be less than the length of the second boundary line 2.

[0014] The boundary line may be a straight line or a curve when the base body 10 is viewed from above in a direction perpendicular to the vertical direction. For example, the boundary line may consist of a single straight line or may include multiple straight lines when the base body 10 is viewed from above in a direction perpendicular to the vertical direction. "The boundary line includes multiple straight lines" means, for example, as shown in Figure 12, a state in which two straight lines (1a) extending in the width direction and one straight line (1b) extending in the vertical direction are connected. Here, the boundary line may be a curve in three dimensions even though it includes straight lines when viewed from above. For example, the first boundary line 1 may consist of a single straight line or may include multiple straight lines. Similarly, the second boundary line 2 may consist of a single straight line or may include multiple straight lines.

[0015] As shown in Figure 1, the base body 10 may have a uniformly wide section 40'a located below the base body 10, which has a constant width. The base body 10 may also have a contraction section 40'b whose width decreases towards the bottom. The uniformly wide section 40'a may extend continuously downward from the contraction section 40'b. The boundary line may be located in the uniformly wide section 40'a or in the contraction section 40'b. For example, the first boundary line 1 may be located in the contraction section 40'b as shown in Figure 1, or in the uniformly wide section 40'a as shown in Figure 3. The same applies to the second boundary line 2.

[0016] 11, the base 10 may have a node. A node refers to a portion of the base 10 where the perimeter is greater than the perimeter of parts of the base 10 located above and below it. In other words, the base 10 may be raised in a node-like shape. The boundary line may also be located at the node.

[0017] The substrate 10 can be made of metal, ceramic, or plastic. Examples of metals include stainless steel alloys, cobalt-chromium alloys, titanium, and titanium alloys. Examples of titanium alloys include alloys in which at least one of aluminum, tin, zirconium, molybdenum, nickel, palladium, tantalum, niobium, vanadium, and platinum is added to titanium. Examples of ceramics include alumina, zirconia, and alumina-zirconia composite ceramics. Examples of plastics include polyethylene, fluorine-based resins, epoxy resins, polyether ether ketone (PEEK) resins, and bakelite. In this embodiment, the substrate 10 is made of a titanium alloy.

[0018] The shape of the base body 10 may be, for example, a substantially rod-like shape, but can be changed appropriately depending on the shape of the artificial joint to which it is applied.

[0019] The coating 20 includes a calcium phosphate-based material and an antibacterial material. As the calcium phosphate-based material, one or more types selected from the group consisting of hydroxyapatite, α-tricalcium phosphate, β-tricalcium phosphate, tetracalcium phosphate, octacalcium phosphate, and calcium phosphate-based glass can be used. As the antibacterial material, natural antibacterial agents, organic antibacterial agents, and inorganic antibacterial agents can be used. For example, hinokitiol can be used as a natural antibacterial agent, benzalkonium chloride as an organic antibacterial agent, and metals can be used as inorganic antibacterial agents, such as silver, copper, and zinc. In addition to the calcium phosphate-based material and the antibacterial material, the coating 20 may also contain glass ceramics and antibacterial agents such as penicillin and vancomycin.

[0020] The concentration of the antibacterial material in the coating 20 may be, for example, 0.05% to 3.00% by weight, 0.05% to 2.50% by weight, 0.05% to 1.00% by weight, or 0.1% to 1.00% by weight. A concentration of 0.05% by weight or higher of the antibacterial material provides sufficient antibacterial properties. Furthermore, a concentration of 3.00% by weight or lower reduces the burden on biological tissue.

[0021] A concentration gradient of the antibacterial material may exist within the coating 20. For example, the concentration of the antibacterial material contained in the upper end of the coating 20 may be greater than the concentration of the antibacterial material contained in the lower end of the coating. This can more effectively reduce the invasion of bacteria from the upper end side of the coating 20. The antibacterial material may be contained only in the upper end of the coating 20.

[0022] The ratio of the area of ​​the region on the surface of the base 10 where the coating 20 is disposed to the area of ​​the region on the surface of the base 10 where the surface is exposed from the coating 20 can be determined appropriately depending on the application, etc. The area of ​​the region on which the coating 20 is disposed and the area of ​​the region on the surface of the base 10 where the surface is exposed from the coating 20 may be the same, or one may be larger. For example, in FIG. 1 , the area of ​​the region on which the coating 20 is disposed is smaller than the area of ​​the region on the surface of the base 10 where the surface is exposed from the coating 20. In this case, it is easier to insert the artificial joint stem 100 into the bone. On the other hand, if the area of ​​the region on which the coating 20 is disposed is larger than the area of ​​the region on the surface of the base 10 where the surface is exposed from the coating 20, bacterial invasion can be further reduced.

[0023] The regions covered with the coating 20 and the regions exposed from the coating 20 can be distinguished by elemental analysis of the surface of each region. Elemental analysis can be performed, for example, by mapping surface elements using an energy dispersive X-ray analyzer (EDX), which is an accessory to a typical scanning electron microscope (SEM). Surface analysis methods such as X-ray photoelectron spectroscopy, Auger electron spectroscopy, and secondary ion mass spectrometry may also be used. Alternatively, the surface of each region may be mechanically scraped off, and the resulting sample may be chemically analyzed to confirm the elements. For example, phosphorus, calcium, antibacterial components, etc. are detected in the region covered with the coating 20. On the surface of the region exposed from the coating 20, elements constituting the substrate 10 are detected, but phosphorus, calcium, antibacterial components, etc. are not detected or are below the noise level.

[0024] The substrate 10 may have a rough surface located on its surface. The boundary on the substrate 10 defined by the presence or absence of the rough surface may include a third boundary line 3 located below the rough surface on the substrate 10. The boundary on the substrate 10 defined by the presence or absence of the rough surface may include a fourth boundary line 4 located above the rough surface on the substrate 10. The rough surface may be covered by the coating 20 or may be exposed from the coating 20. Alternatively, only a portion of the rough surface may be covered by the coating 20, and another portion of the rough surface may be exposed from the coating 20. For example, the third boundary line 3 may be located above or below the first boundary line 1 on the substrate 10. The fourth boundary line 4 may be located above or below the second boundary line 2 on the substrate 10.

[0025] An index of the surface roughness of the rough surface is, for example, the arithmetic mean roughness Sa (ISO 25178). The surface roughness (Sa) of the rough surface may be set to, for example, 10 to 80 μm, 20 to 80 μm, or 30 to 70 μm. The surface roughness (Sa) of the rough surface can be measured, for example, by cutting the artificial joint stem 100 and observing the cut surface using an SEM or the like.

[0026] The surface roughness (Sa) may be measured, for example, by a stylus or optical method. The surface roughness (Sa) may also be measured, for example, in accordance with ISO 25178. However, the method for measuring the surface roughness (Sa) is not limited to the above method.

[0027] The artificial joint stem 100 may further include a layered member 30. In this specification, the term "layered member" refers to a member that is layered on the substrate 10 and is different from the coating 20. For example, the surface of the layered member 30 may be roughened. This allows the area that primarily comes into contact with the bone to be roughened. The layered member 30 may be formed by a thermal spraying method, as described below. Alternatively, the layered member 30 may be formed as a porous structure.

[0028] FIG. 4 shows a cross section taken along the line A-A' in FIG. 1, including the first boundary line 1. In FIG. 4, a layer member 30 is arranged as a rough surface. This makes the area where the layer member 30 is provided higher than the area where the layer member 30 is not provided. Therefore, when the artificial joint stem 100 is embedded in the bone, it is possible for the layer member 30 to mainly come into contact with the bone. In FIG. 4, a coating 20 is formed on the layer member 30.

[0029] In FIG. 4, the boundary defined by the presence or absence of the layer member 30, which has a rough surface, includes a third boundary line 3 located below the layer member 30 on the base 10. The third boundary line 3 is located above the base 10 relative to the first boundary line 1. In other words, the coating 20 is formed so as to straddle the third boundary line 3. In this case, the edge of the layer member 30 is covered by the coating 20. In other words, it is possible to prevent the edge of the layer member 30 from being exposed from the coating 20. This can further reduce bacterial growth.

[0030] The third boundary line 3 may have a shape that follows the first boundary line 1, or may have a shape that is different from the first boundary line 1. The component of the third boundary line 3 along the vertical direction may be larger or smaller than the component along the width direction of the base 10. The component of the third boundary line 3 can be considered similar to the first boundary line 1 described above.

[0031] 5 shows a cross section taken along the line B-B' in FIG. 1, which includes the second boundary line 2. In FIG. 5, the boundary line defined by the presence or absence of the layer member 30, which has a rough surface, includes a fourth boundary line 4, which is located above the base 10 relative to the layer member 30. The fourth boundary line 4 is located below the base 10 relative to the second boundary line 2. In other words, the coating 20 is formed so as to straddle the fourth boundary line 4. In this case, as in FIG. 4, the edge of the layer member 30 is covered by the coating 20, further reducing bacterial growth.

[0032] The fourth boundary line 4 may have a shape that follows the second boundary line 2, or may have a shape that is different from the second boundary line 2. The component of the fourth boundary line 4 along the vertical direction may be larger or smaller than the component along the width direction of the base 10. The component of the fourth boundary line 4 can be considered similar to the first boundary line 1 described above.

[0033] The height of the layer member 30 may have a lower limit of 100 μm or more, or may be set to 300 μm or more, for example. The upper limit may be set to 1000 μm or less, or may be set to 700 μm or less, for example. The surface roughness of the layer member 30 may be set to 10 to 80 μm, 20 to 80 μm, or 30 to 70 μm, for example.

[0034] The layer member 30 can be made of the same materials as those exemplified for the base 10. For example, the layer member 30 may be made of a metal. This ensures sufficient strength. The material of the layer member 30 and the material of the base 10 may be the same or different. In this embodiment, the layer member 30 is made of a titanium alloy.

[0035] The height of the layer member 30 may be greater than the thickness of the coating 20. This makes the region where the layer member 30 is formed higher than the region where only the coating 20 is formed, allowing the region where the layer member 30 is formed to mainly come into contact with the bone. The thickness of the coating 20 may be set to less than 100 μm, for example, or may be set to less than 50 μm. The thickness of the coating 20 may also be set to 5 μm or more, for example.

[0036] As described above, the substrate 10 may have an embedded portion 40 that is embedded in a bone and an exposed portion 50 that is exposed from the bone. An example of the bone is the femur. The coating 20 may be formed on a portion of the peripheral wall of the embedded portion 40. This allows the embedded portion 40, which may actually come into contact with the bone, to exhibit desired adhesiveness and antibacterial properties.

[0037] 6, at least a portion of coating 20 may be disposed in boundary region 60 that includes the boundary between buried portion 40 and exposed portion 50. In other words, coating 20 may be disposed in a region of buried portion 40 that is closer to exposed portion 50. This makes it possible to more effectively reduce the invasion of bacteria from the exposed portion 50 side.

[0038] The coating 20 placed in the boundary region 60 may be placed only in the embedded portion 40. In other words, the coating 20 does not have to be placed in the exposed portion 50. This reduces irritation to soft tissues that the exposed portion 50 may come into contact with.

[0039] The base 10 may include a main body portion 40' including the constant width portion 40'a and the contracted portion 40'b, and a neck portion 50' connected to the upper end of the main body portion 40'. The main body portion 40' may be embedded in the femur. The neck portion 50' may be exposed from the femur. A femoral head may be provided on the neck portion 50'. The femoral head may be fitted into an acetabular cup that is mated with a stem for an artificial joint.

[0040] As shown in FIG. 6, the constant-width portion 40'a may have a central axis C extending in the vertical direction. The contracted portion 40'b may extend continuously from the constant-width portion 40'a in the vertical direction and have a curved shape such that its center moves away from the central axis C as it extends upward. The contracted portion 40'b may have an upper end surface that is offset from the central axis C, and a neck portion 50' may be connected to the upper end surface. The neck portion 50' has a smaller width than the upper end surface of the main body portion 40'. In other words, the neck portion 50' can be said to be a protrusion 50' that protrudes at an angle relative to the vertical direction of the base 10.

[0041] The base 10 may further include a collar 60' provided at the connection between the main body 40' and the neck 50'. The collar 60' is a protrusion that protrudes from the connection toward the surface of the upper end surface. The collar 60' can prevent the main body 40' from penetrating too far into the bone during surgery to insert the artificial joint stem into the bone.

[0042] The coating 20 may satisfy the following formula (1) or the following formula (2). L1≦L2 (1) L1≧L2 (2) In equations (1) and (2), L1 represents the length of the coating 20 on the side where the neck portion 50' protrudes, along the vertical direction, and L2 represents the length of the coating 20 on the side opposite to the side where the neck portion 50' protrudes, along the vertical direction.

[0043] The coating 20 shown in FIG. 6 satisfies formula (2). L1 can also be considered to be the maximum length along the Y-axis direction on the side where the neck portion 50' protrudes in the region where the coating 20 is disposed. In other words, L1 represents the difference in Y-coordinate between the point where the Y-coordinate is maximum and the point where the Y-coordinate is minimum on the side where the neck portion 50' protrudes in the region where the coating 20 is disposed. L2 can also be considered to be the maximum length along the Y-axis direction on the side opposite the side where the neck portion 50' protrudes in the region where the coating 20 is disposed. In other words, L2 represents the difference in Y-coordinate between the point where the Y-coordinate is maximum and the point where the Y-coordinate is minimum on the side where the neck portion 50' protrudes in the region where the coating 20 is disposed. The coating 20 shown in FIG. 7 satisfies formula (1).

[0044] The artificial joint stem 101 shown in Figure 10 is also included in the artificial joint stem according to the present disclosure. For example, a recess 25 having an opening on the surface of the coating 20 may be provided. The opening area of ​​the recess 25 located on the upper end side of the coating 20 may be larger than the opening area of ​​the recess 25 located on the lower end side of the coating 20. The recess 25 may be provided only on the upper end of the coating 20.

[0045] An artificial joint stem 102 shown in FIG. 11 is also included in the artificial joint stem according to the present disclosure. For example, the base body 10 may have a groove, and the groove may be arranged across the area where the coating 20 is arranged and the area exposed from the coating 20. The groove may extend to the upper end of the coating 20. The surface roughness within the groove may be smaller than the surface roughness of the base body 10. One end of the groove may be exposed from the coating 20, and the other end may be located in the contracted portion 40'b of the base body 10.

[0046] The base 10 may have a concavely curved inner portion 13 and a convexly curved outer portion 14. Here, the groove may be bent toward either the inner portion 13 or the outer portion 14 at the contracted portion 40'b. For example, the groove may be bent toward the inner portion 13 at the contracted portion 40'b.

[0047] The grooves located in the region where the coating 20 is disposed are referred to as first grooves 11, and the grooves located in the region where the surface of the substrate 10 is exposed from the coating 20 are referred to as second grooves 12. The first grooves 11 may or may not be connected to the second grooves 12. That is, the first grooves 11 and the second grooves 12 may be formed as a continuous groove. The upper end of the first groove 11 may be located in a curved portion on the inner side. The upper end of the first groove 11 may be bent toward the inner side. In other words, the first groove 11 may have a first portion 11a extending in the vertical direction of the substrate 10 and a second portion 11b connected to the first portion 11a and having a component along the width direction of the substrate 10. The depth of the second grooves 12 may be smaller than the depth of the first grooves 11. The second portion 11b of the first groove 11 having a component along the width direction of the base body 10 means, in other words, that the second portion 11b of the first groove 11 is not parallel to the up-down direction of the base body 10. In other words, the second portion 11b of the first groove 11 is not parallel to the insertion direction of the artificial joint stem 102 into the bone, but is inclined. If the second portion 11b of the first groove 11 has a component along the width direction of the base body 10, it can resist sinking.

[0048] The substrate 10 may have a plurality of grooves. The substrate 10 may also include a first groove set 15 in which the first grooves 11 and the second grooves 12 are connected, and a second groove set 16 in which the first grooves 11 and the second grooves 12 are connected and the first grooves 11 extend further toward the upper end of the coating 20 than the first groove set 15.

[0049] Furthermore, the base body 10 may have multiple first groove sets 15. The multiple first groove sets 15 may be arranged in the width direction of the base body 10. Of the multiple first groove sets 15, the first groove set 15 located on the outer portion 14 side may be located above the first groove set 15 located on the inner portion 13 side.

[0050] An artificial joint stem 103 shown in FIG. 12 is also included in the artificial joint stems according to the present disclosure. For example, the base body 10 may have a plurality of grooves, and the grooves located in the upper part of the base body 10 may be wider than the grooves located in the lower part of the base body 10. The grooves may have a component along the width direction of the base body 10. FIG. 13 shows a CC' cross section of FIG. 12. As shown in FIG. 13, the grooves along the width direction of the base body 10 (second portion 11b of first groove 11) may become shallower toward the top.

[0051] The first boundary line 1 may intersect the straight portion of the groove. Here, the first boundary line 1 may intersect the straight portion of the groove diagonally. In other words, the first boundary line 1 does not have to be perpendicular to the straight portion of the groove.

[0052] Furthermore, the first boundary line 1 may have a first portion 1a extending in a direction intersecting the groove and a second portion 1b extending in a direction along the groove. The second portion 1b of the first boundary line 1 may be positioned away from the groove. That is, the second portion 1b of the first boundary line 1 does not have to be in contact with the groove. The same applies to the second boundary line 2.

[0053] The first groove 11 and the second groove 12 are connected, and the first groove 11 may have a first portion 11a extending in the vertical direction of the base 10 and a second portion 11b connected to the first portion 11a and having a component along the width direction of the base 10. As shown in Figure 12, the second boundary line 2 may extend in a direction along the second portion 11b of the first groove 111.

[0054] 12, the second boundary line 2 may be disposed so as to tilt upward from the inner portion 13 toward the outer portion 14. Also, as shown in FIG. 12, the first boundary line 1 may be located below the apex 13a of the recess in the inner portion 13. The first boundary line 2 may be located below the apex 14a of the protrusion in the outer portion 14. Alternatively, the first boundary line 1 may be located above the apex 14a of the protrusion in the outer portion 14.

[0055] The artificial joint stem 104 shown in Figure 14 is also included in the artificial joint stems according to the present disclosure. For example, the boundary line defined by the presence or absence of the coating 20 and the groove may intersect at an acute angle. In Figure 14, of the angles formed by the first boundary line 1 and the second groove 12, the angle γ on the inner side of the medial portion 13 is an acute angle.

[0056] The artificial joint stem 105 shown in FIG. 15 is also included in the artificial joint stem according to the present disclosure. For example, the base body 10 includes, from top to bottom, a roughened surface region 70, a non-roughened surface region 80, and a grooved surface region 90. The roughened surface region 70 has a roughened surface. The non-roughened surface region 80 is a region without a roughened surface. The grooved surface region 90 has grooves. For example, the roughened surface region 70 may be a region with a roughened surface but no grooves, the non-roughened surface region 80 may be a region without a roughened surface or grooves, and the grooved surface region 90 may be a region without a roughened surface but with grooves. The coating 20 may cover at least one of the roughened surface region 70, the non-roughened surface region 80, and the grooved surface region 90. The area of ​​the roughened surface region 70 may be smaller than the area of ​​the non-roughened surface region 80. In the width direction of the base body 10, the length of the roughened surface region 70 may be greater than the length of the non-roughened surface region 80. The boundary line 23 between the roughened surface region 70 and the non-roughened surface region 80 may be inclined upward from the inner portion 13 toward the outer portion 14. The length L3 of the roughened surface region 70 on the inner portion 13 side may be smaller than the length L4 of the roughened surface region 70 on the outer portion 14 side. When viewed in a plan view perpendicular to the XY plane in FIG. 15 , the length L3 represents the difference in Y coordinate between the point where the Y coordinate is maximum and the point where the Y coordinate is minimum on the inner portion 13 side of the roughened surface region 70. The length L4 represents the difference in Y coordinate between the point where the Y coordinate is maximum and the point where the Y coordinate is minimum on the outer portion 14 side of the roughened surface region 70.

[0057] Artificial joint stems 106, 107, and 108 shown in Figure 16 are also included in the artificial joint stems according to the present disclosure. For example, as in the artificial joint stem 106, the second boundary line 2 may be a straight line. As in the artificial joint stem 107, the apex 14a of the convex portion on the lateral side 14 may be exposed from the coating 20. As in the artificial joint stem 108, the second boundary line 2 may follow the shape of the lateral side 14 of the base body 10.

[0058] 2. Manufacturing method of stem for artificial joint A manufacturing method for an artificial joint stem according to one embodiment includes, for example, a preparation step and a coating formation step. In the preparation step, a base 10 having a surface including a first region and a second region is prepared. In the coating formation step, a coating 20 including a calcium phosphate material and an antibacterial material is formed on a portion (first region) of the surface of the base 10. Here, the coating 20 is formed so that, of the boundaries on the base 10 defined by the presence or absence of the coating 20, a first boundary line 1 located below the base 10 relative to the coating 20 intersects with the vertical direction, and the component of the first boundary line 1 along the vertical direction is smaller than the component along the width direction of the base 10. This allows the artificial joint stem 100 described above to be obtained.

[0059] In the preparation step, the base 10 can be prepared by forming a metal material into a desired shape using a mold, an additive manufacturing method, or the like. In the base 10, the second region is positioned so as to sandwich the first region in the vertical direction, so that the first boundary line and the second boundary line can be formed after the coating 20 is formed. Furthermore, the shapes of the first boundary line and the second boundary line of the coating can be adjusted depending on the shape of the first region.

[0060] The coating 20 can be formed by, for example, a thermal spraying method such as flame spraying, high velocity flame spraying, or plasma spraying; a physical vapor deposition method or a chemical vapor deposition method such as sputtering, ion plating, ion beam deposition, or ion mixing; or a wet coating method such as a sol-gel method. The material that constitutes the coating is also referred to as the coating material.

[0061] A first protective material may be used to form a coating 20 only in the first region. In this case, before the coating formation step, there may be a further step of arranging the first protective material so as to protect the second region while exposing the first region, so that a coating is not formed in the second region. For example, masking tape or a screen may be used as the first protective material. Alternatively, a jig that covers the base body 10 may be used as the first protective material. Examples of materials for these first protective materials include metal, glass, resin, and composite materials thereof. The first protective material may or may not be in contact with the base body 10. If, for example, masking tape is used as the first protective material, the first protective material should be arranged in the shape of the second region. If a jig that covers the base body 10 is used, the shape of the jig is not particularly limited, but it may be cylindrical, for example. The cross-section of the cylindrical jig may be polygonal or circular.

[0062] When a screen is used, the coating 20 can be formed in a specific area by setting the screen in a predetermined position. When a jig is used, the coating 20 can be formed in a specific area by setting the jig in a predetermined position. In this case, for example, by adjusting the positional relationship between the discharge nozzle that discharges the thermal spray material, additive manufacturing material, chemical etching material, blast material, or coating material and the screen, the coating 20 can be selectively formed only in the desired area. In this case, the tip of the discharge nozzle should be positioned in a straight line with the surface of the desired area without the screen separating them. Furthermore, below, the thermal spray material, additive manufacturing material, chemical etching material, blast material, or coating material discharged from the discharge nozzle will also be referred to as the discharge material. However, the coating 20 may be formed with the base body 10, screen, and discharge nozzle fixed, or the coating 20 may be formed while at least one of them is moved. Also, the angle of the discharge nozzle may be fixed, or the coating 20 may be formed while the angle is changed.

[0063] It is also possible to form the coating 20 only in the desired region without using a protective material. For example, the coating 20 can be selectively formed only in the desired region by adjusting the shape, angle, or position of the discharge nozzle that discharges the discharge material. For example, the discharge material may be discharged while the discharge nozzle is positioned above the surface of the desired region. In this case, the substrate 10 may be fixed and the coating 20 may be formed while moving the position and angle of the discharge nozzle, or the discharge nozzle may be fixed and the coating 20 may be formed while moving the position and angle of the substrate 10. The discharge nozzle may be moved at a constant speed or at a variable speed. Furthermore, the discharge direction of the discharge material may form an angle of 90° or less with respect to a vector extending from the tip of the discharge nozzle toward the surface of the substrate 10 or rough surface that is closest to the tip of the discharge nozzle.

[0064] A roughening step can also be carried out before the coating step. The roughening step is a step of forming a rough surface on the substrate 10. Specifically, in the preparation step, the substrate 10 is prepared, which has a surface that further includes a roughened region in addition to the first region and the second region, and in the roughening step, a rough surface is formed in the roughened region of the substrate 10.

[0065] In the surface roughening process, the roughened surface can be formed by at least one of thermal spraying, additive manufacturing, chemical etching, and blasting. Compared to blasting, thermal spraying, additive manufacturing, and chemical etching can increase the surface roughness. The material ejected toward the substrate 10 in thermal spraying is referred to as the thermal spray material. Similarly, the material ejected toward the substrate 10 in additive manufacturing is referred to as the additive manufacturing material. Furthermore, the material ejected toward the substrate 10 when processing by chemical etching is referred to as the chemical etching material. Similarly, the material ejected toward the substrate 10 when processing by blasting is referred to as the blasting material. The materials exemplified as the material for the substrate 10 can be used as the thermal spray material and additive manufacturing material. The layered member described above may be formed by thermal spraying or additive manufacturing. Examples of chemical etching include alkali treatment. Examples of blasting include sandblasting.

[0066] A second protective material may be used to form a roughened surface only in a desired region. In this case, a step of arranging the second protective material to expose the roughened region and protect other regions may be further included prior to the roughening step, so that a roughened surface is not formed in regions other than the roughened region. The roughened region may be located inside the first region, or may be located across the first and second regions. That is, the second protective material may be located so as to protect a portion of the first region and the second region, or the second region. Furthermore, for example, the position of the roughened region can adjust the positional relationship between the third and fourth boundary lines defined by the presence or absence of a roughened surface and the first and second boundary lines defined by the presence or absence of a coating.

[0067] As the second protective material, for example, masking tape or a screen may be used. Alternatively, a jig that covers the base 10 may be used as the second protective material. Examples of materials for these second protective materials include metal, glass, resin, and composite materials thereof. The second protective material may or may not be in contact with the base 10. When a jig that covers the base 10 is used as the second protective material, the shape of the jig is not particularly limited, but it may be cylindrical, for example. The cross-section of the cylindrical jig may be polygonal or circular.

[0068] When a screen is used, a rough surface can be formed in a specific area by setting the screen in a predetermined position. When a jig is used, a rough surface can be formed in a specific area by setting the jig in a predetermined position. In this case, for example, by adjusting the positional relationship between the discharge nozzle that discharges the thermal spray material, additive manufacturing material, chemical etching material, blast material, or coating material and the screen, a rough surface can be selectively formed only in the desired area. In this case, the tip of the discharge nozzle should be positioned in a straight line with the surface of the desired area, for example, without the screen separating them. Furthermore, below, the thermal spray material, additive manufacturing material, chemical etching material, blast material, or coating material discharged from the discharge nozzle will also be referred to as the discharge material. However, the rough surface may be formed with the base body 10, screen, and discharge nozzle fixed, or with at least one of them moved. Also, the angle of the discharge nozzle may be fixed or varied while forming the rough surface. In addition, similar to the coating 20, a rough surface may be formed only in the desired area without using a protective material.

[0069] Based on the above, when forming a rough surface on an artificial joint stem, for example, in the roughening step, a second protective material may be placed on the base body 10 such that a portion of the surface of the base body 10 is exposed while protecting another portion of the base body 10, and a rough surface may be formed on the exposed portion. Furthermore, the manufacturing method according to this disclosure may further include a step of removing the second protective material after the roughening step and before the coating formation step.

[0070] Furthermore, after removing the second protective material, a step of scraping the edges of the rough surface, for example, the edges of the layer member 30, may be performed. This makes it possible to avoid stress concentration at the edges of the layer member 30 and reduce irritation to biological tissue.

[0071] A second masking tape may be used as the second protective material. In this case, the manufacturing method according to the present disclosure may further include, before the roughening step, a step of exposing a portion of the surface of the substrate 10 and attaching the second masking tape to another portion of the surface of the substrate 10.

[0072] Furthermore, in the coating formation step, the first protective material may be placed on the substrate 10 such that a portion of the substrate 10's surface is exposed while protecting another portion of the substrate 10, and the coating 20 may be formed on the exposed portion of the substrate 10's surface. The first protective material can be removed after the coating formation step. Here, a first masking tape may be used as the first protective material. In this case, the manufacturing method according to this disclosure may further include a step of applying a second masking tape to another portion of the substrate 10 while exposing a portion of the substrate 10's surface before the coating formation step.

[0073] A second protective material with higher heat resistance than the first protective material can be used. For example, a material that does not melt or decompose for 1 minute under thermal spraying conditions of 8000°C may be used as the second protective material, and a material that does not melt or decompose for 1 minute under thermal spraying conditions of 3000°C may be used as the first protective material. Specific examples of such materials include composite materials of glass and resin.

[0074] When the surface roughening step is performed by blasting, the second protective material may be a material that does not melt or thermally decompose at room temperature. Specific examples of such materials include resins.

[0075] Furthermore, in the step of forming the roughened surface or coating 20 in the manufacturing method according to the present disclosure, a protective material may be disposed in addition to the first protective material and second protective material described above. For example, in the step of forming the roughened surface or coating 20, a protective material may be disposed on part or all of the exposed portion 50. This allows appropriate control over whether or not the roughened surface or coating 20 is formed on the exposed portion 50. For example, by disposing a protective material in the region of the exposed portion 50 farther from the buried portion 40 and forming the coating 20 on the exposed region, the coating 20 can be formed on the region of the exposed portion 50 closer to the buried portion 40.

[0076] To summarize the above, the steps can be performed in the order shown in Figure 8, for example. Figure 8 is a process diagram showing a method for manufacturing an artificial joint stem 100 according to one embodiment. First, a second protective material is placed, followed by a surface roughening step, after which the second protective material can be removed. Thereafter, a first protective material is placed, followed by a coating formation step.

[0077] Furthermore, the manufacturing method according to the present disclosure may or may not include a cleaning step between each step. For example, the manufacturing method according to the present disclosure may include a step of cleaning the substrate 10, or the substrate 10 and the layer member 30, after the surface roughening step. The cleaning method is not particularly limited, but may include, for example, immersion in a liquid such as water or an organic solvent such as alcohol, or showering using such a liquid. Alternatively, a method of spraying a gas such as air, nitrogen, or argon may be used. This allows for the removal of excess sprayed material and / or shavings generated by the surface roughening step.

[0078] In the manufacturing method according to the present disclosure, a roughening step for roughening the surface of the substrate 10 may be followed by a groove forming step for forming grooves, followed by a coating forming step for forming a coating. Alternatively, the groove forming step may be followed by a roughening step, followed by a coating forming step. In the groove forming step, the grooves can be formed by at least one of cutting, rolling, and pressing. For example, the grooves may be formed by milling, which is a type of cutting method. Furthermore, when recesses are to be formed, the recess forming step may be performed instead of the groove forming step using a method similar to that used in the groove forming step.

[0079] The roughening step may include, in order, a first roughening step of forming a first rough surface by thermal spraying and a second roughening step of forming a second rough surface by chemical etching or blasting. Here, the region where the first rough surface is formed by thermal spraying is referred to as the first roughened region, the region where the second rough surface is formed by chemical etching or blasting is referred to as the second roughened region, and the region where no rough surface is formed is referred to as the non-roughened region.

[0080] In the first roughening step, a third protective material (the second protective material described above) may be disposed on the substrate 10 so as to protect the second roughened region and the non-roughened region while exposing the first roughened region, and a first roughened surface may be formed in the exposed first roughened region. The manufacturing method according to the present disclosure may further include a step of removing the third protective material after the first roughening step and before the second roughening step. In the second roughening step, a fourth protective material may be disposed on the substrate 10 so as to protect the non-roughened region while exposing the second roughened region, and a second roughened surface may be formed in the exposed second roughened region. The second roughening step may be performed so that the surface of the second roughened surface formed in the second roughening step has a smaller surface roughness than the surface of the first roughened surface in the first roughened region. The manufacturing method according to the present disclosure may also include a step of removing the fourth protective material after the second roughening step and before the coating formation step. A fourth masking tape may be used as the fourth protective material. The manufacturing method according to the present disclosure may further include, before the second roughening step, a step of attaching a fourth masking tape to the non-roughened region 3 while exposing the first roughened region 1 and the second roughened region 2. The fourth protective material may have lower heat resistance than the third protective material described above. For example, a material that does not melt or thermally decompose at room temperature may be used as the fourth protective material. Specifically, a resin may be used as the fourth protective material.

[0081] In the second roughening step, the non-roughened region may or may not be covered with a protective material. The first roughened region and the non-roughened region may be protected, and at least one of chemical etching and blasting may be performed on only the second roughened region. Alternatively, a fourth protective material may be placed to expose the first roughened region, and the exposed roughened surface of the first roughened region and the second roughened region may be subjected to at least one of chemical etching and blasting. This allows excess sprayed material remaining on the roughened surface of the first roughened region to be removed, while also forming a roughened surface in the second roughened region.

[0082] The method for manufacturing the artificial joint stem 100 may also include first a step of preparing the base body 10 having a first roughened region, a second roughened region, and a non-roughened region arranged in this order.

[0083] [3. Use of stems for artificial joints] 1 has a shape intended primarily for use as a stem for an artificial hip joint, but the artificial joint to which the artificial joint stem according to the present disclosure is applicable is not limited to an artificial hip joint. Examples of artificial joints include an artificial hip joint, an artificial knee joint, an artificial ankle joint, an artificial shoulder joint, an artificial elbow joint, and an artificial finger joint.

[0084] An example of using the artificial joint stem 100 as part of an artificial hip joint 1000 will be described below with reference to Figure 9. The artificial hip joint 1000 may include, in addition to the artificial joint stem 100, a femoral head 110 and an acetabular cup 120. The femoral head 110 and the acetabular cup 120 may be formed of the same material as the base 10 of the artificial joint stem 100, or may be formed of a different material. The artificial joint stem 100 is embedded in the femur 91. The femoral head 110 is placed in the exposed portion 50 of the artificial joint stem 100. The acetabular cup 120 is fixed to the acetabulum 94 of the hipbone 93. The femoral head 110 is fitted and slid into the recess of the acetabular cup 120, thereby functioning as a hip joint.

[0085] The invention according to the present disclosure has been described above based on the drawings and examples. However, the invention according to the present disclosure is not limited to the above-described embodiments. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art can easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure. [Explanation of symbols]

[0086] 1. First boundary line 2 Second boundary line 3 Third Boundary 4 Fourth Boundary 10 Base 20 Coating 40´a Equal width part 40´b contraction 50´ neck 100 Artificial joint stem

Claims

1. a substrate having a convexly curved outer portion; a coating on a portion of the substrate, the coating comprising a calcium phosphate-based material and an antimicrobial material; a boundary line on the substrate defined by the presence or absence of the coating includes a second boundary line located below the apex of the convex shape in the outer portion and a first boundary line located below the second boundary line; The base body has a groove positioned across the first boundary line.

2. 2. The artificial joint stem according to claim 1, wherein the base extends in the vertical direction when the proximal side of the human body when the artificial joint stem is used is considered to be the upward direction, and the second boundary line is the upper boundary line of the coating.

3. The prosthetic stem of claim 2 , wherein the first boundary line is located below the capsule.

4. The artificial joint stem according to claim 3 , wherein the first boundary line intersects the vertical direction.

5. 5. An artificial joint stem as described in claim 3 or 4, which has a layer member located on the surface of the base body, and the boundary line defined by the presence or absence of the layer member has a third boundary line located below the base body relative to the layer member.

6. The artificial joint stem according to claim 5 , wherein the third boundary line is located above the base body relative to the first boundary line.

7. The artificial joint stem according to claim 5 or 6, wherein the third boundary line has a shape that follows the first boundary line.

8. 8. The stem for an artificial joint according to claim 2, further comprising a layer member located on the surface of the base body, and wherein the boundary defined by the presence or absence of the layer member includes a fourth boundary line located above the base body relative to the layer member.

9. The artificial joint stem according to claim 8 , wherein the fourth boundary line is located below the second boundary line of the base body.

10. 8. The artificial joint stem according to claim 3, wherein the length of the first border line is smaller than the length of the second border line.

11. The stem for an artificial joint according to any one of claims 2 to 10, wherein the base body has a neck portion that protrudes at an angle relative to the vertical direction.

12. An artificial hip joint comprising the artificial joint stem according to any one of claims 1 to 11.

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