Artificial joint stems and artificial hip joints

Abstract

To provide an artificial joint stem.SOLUTION: An artificial joint stem 100 comprises a base 10 comprising one or more grooves formed in a surface, and a coating 20 formed on a portion of the surface of the base, and including a calcium phosphate-based material and an antibacterial material. When the grooves located in a region where the coating is formed, out of the one or more grooves, are called first grooves 1, and the grooves located in a region where the surface of the base is exposed are called second grooves 2, the sum of the lengths of the first grooves is smaller than the sum of the lengths of the second grooves.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 well 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 present disclosure provides an artificial joint stem comprising a substrate having one or more grooves disposed on a surface thereof, and a coating containing a calcium phosphate-based material and an antibacterial material disposed on a portion of the surface of the substrate, wherein the grooves located in the region where the coating is disposed are designated as first grooves, and the grooves located in the region where the surface of the substrate is exposed are designated as second grooves, and the total length of the first grooves is smaller than the total length of the second grooves.

[0006] Alternatively, the present disclosure provides an artificial joint stem comprising a substrate having one or more recesses disposed on its surface, and a coating containing a calcium phosphate material and an antibacterial material disposed on a portion of the surface of the substrate, wherein the recesses located in the region where the coating is disposed are defined as first recesses, and the grooves located in the region where the surface of the substrate is exposed are defined as second recesses, and the total opening area of ​​the first recesses is smaller than the total opening area of ​​the second recesses. [Brief explanation of the drawings]

[0007] [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 a cross section of 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 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] 1 is a schematic diagram showing a cross section of an artificial joint stem according to one embodiment. FIG. [Figure 9] 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG. [Figure 10] 1A to 1C are process diagrams showing a method for manufacturing an artificial joint stem according to one embodiment. [Figure 11] 1 is a schematic diagram showing an artificial hip joint 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 an artificial joint stem according to one embodiment. FIG. [Figure 14] 1 is a schematic diagram showing a cross section of 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. [Figure 17] 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] 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."

[0009] [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 and a coating 20 disposed on a portion of the surface of the base 10. 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 the bone and an exposed portion 50 that is exposed from the bone. In FIG. 1, the coating 20 is formed on a region of the embedded portion 40 that is close to the exposed portion 50, while a region farther from the exposed portion 50 is exposed from the coating 20. The calcium phosphate-based material has the effect of improving adhesion to the bone. The antibacterial material has the effect of reducing bacterial adhesion and proliferation.

[0010] 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.

[0011] The base body 10 also has one or more grooves arranged on its surface. These grooves contribute to facilitating insertion of the artificial joint stem 100 into the bone. Here, of the one or more grooves, the grooves located in the area where the coating 20 is arranged are designated as first grooves 1, and the grooves located in the area where the surface of the base body 10 is exposed from the coating 20 are designated as second grooves 2. The total length of the first grooves 1 is smaller than the total length of the second grooves 2.

[0012] In this specification, "the total length of the first grooves 1" does not necessarily mean that there are multiple first grooves 1. The groove may include one or more first grooves 1. If the first groove 1 is a curved groove, the length along the curve is measured. If the first groove 1 is branched, the lengths of the branched grooves are also totaled. The same applies to "the total length of the second grooves 2." Furthermore, "the total length of the first grooves 1 is smaller than the total length of the second grooves 2" also includes the case where the total length of the first grooves 1 is zero. In other words, the groove may or may not include the first groove 1. The groove only needs to include at least the second groove 2, and may include only the second groove 2. As a result, the fixation of the artificial joint stem 100 to the bone, etc., can be adjusted.

[0013] In the artificial joint stem 100 shown in FIG. 1, the base body 10 has both a first groove 1 and a second groove 2. Also, in FIG. 1, the base body 10 has a plurality of first grooves 1. Also, in FIG. 1, the base body 10 has one second groove 2. As a result, it is possible to facilitate insertion of the artificial joint stem 100 into bone. FIG. 2 shows an example different from FIG. 1. In the artificial joint stem 100 shown in FIG. 2, the base body 10 does not have a first groove 1, but only has a second groove 2. When the base body 10 does not have a first groove 1, it is possible to further reduce the invasion of bacteria from the area where the coating 20 is disposed.

[0014] In other words, in the artificial joint stem 100, the grooves may include first grooves 1 located in the region where the coating 20 is disposed and second grooves 2 located in the region where the surface of the base body 10 is exposed from the coating 20, and the total length of the first grooves 1 may be smaller than the total length of the second grooves 2. Alternatively, the grooves may include only second grooves 2 located in the region where the surface of the base body 10 is exposed from the coating 20, and no grooves may be formed in the region where the coating 20 is disposed.

[0015] The first groove 1 may or may not be connected to the second groove 2. That is, the first groove 1 and the second groove 2 may be formed as a continuous groove. In other words, 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. Also, as shown in FIG. 1, only some of the multiple first grooves 1 may be connected to the second groove 2. The same applies when multiple second grooves 2 are present. If the first groove 1 is connected to the second groove 2, it is easier to insert the artificial joint stem 100 into the bone. On the other hand, if the first groove 1 is not connected to the second groove 2, it is possible to further reduce the invasion of bacteria from the first groove 1 side.

[0016] The depth D1 of the first groove 1 and the depth D2 of the second groove 2 may be the same, or one may be larger. The same applies to the relationship between the width W1 of the first groove 1 and the width W2 of the second groove 2. Here, the depth D1 of the first groove 1 can be calculated as the average depth of several arbitrary locations on the first groove 1. The width W1 of the first groove 1 can be calculated in a similar manner. The same applies to the depth D2 and width W2 of the second groove 2. Note that the depth D1 and width W2 of the first groove 1 represent the depth and width on the coating 20. FIG. 3 shows the A-A' cross section including the first groove 1 and the B-B' cross section including the second groove 2 of FIG. 1. In FIG. 3, the depth D1 of the first groove 1 is smaller than the depth D2 of the second groove 2. In FIG. 3, the width W1 of the first groove 1 is smaller than the width W2 of the second groove 2. When the depth D1 of the first groove 1 is smaller than the depth D2 of the second groove 2 and / or when the width W1 of the first groove 1 is smaller than the width W2 of the second groove 2, the invasion of bacteria from the first groove 1 side can be further reduced.

[0017] Furthermore, the groove may have the same depth at both ends in the width direction of the groove, or the depth at one end may be smaller than the depth at the other end. Figure 4 is a cross section taken along line A-A' including the first groove 1 in Figure 1, showing an example different from Figure 3. In Figure 4, the depth D1a at one end of the first groove 1 in the width direction of the groove is smaller than the depth D1b at the other end.

[0018] The grooves can also be broken down into a component along the width direction of the base 10 and a component along a direction perpendicular to the width direction. The components of the grooves will be described below with reference to FIG. 5. The base 10 shown in FIG. 5 has a shape that extends in the vertical direction. It can also be said that the top of the vertical direction of the base 10 corresponds to the proximal side of the human body, and the bottom corresponds to the distal side of the human body. The width direction of the base 10 can also be said to be a direction perpendicular to this vertical direction. In other words, the direction perpendicular to the width direction can also be the vertical direction of the base 10. In FIG. 5, the width direction of the base 10 is represented as the X-axis direction, and the direction perpendicular to the width direction is represented as the Y-axis direction.

[0019] Here, we consider the straight line α that connects the ends of the first groove 1 where the distance is greatest. When the straight line α is parallel to the X axis, it can be said that the first groove 1 has only a component along the width direction of the base 10. When the straight line α is parallel to the Y axis, it can be said that the first groove 1 has only a component along the direction perpendicular to the width direction of the base 10. When the straight line α is expressed as a straight line with a slope on the XY coordinate system, it can be said that the first groove 1 has both a component along the width direction of the base 10 and a component along the direction perpendicular to the width direction.

[0020] The first groove 1 shown in FIG. 5 has both a component along the width direction of the base 10 and a component along a direction perpendicular to the width direction, but it may have only one of these. It can also be said that the first groove 1 has at least one of a component along the width direction of the base 10 and a component along a direction perpendicular to the width direction. The fact that the first groove 1 has a component along the width direction of the base 10 means that the first groove 1 is not parallel to the vertical direction. In other words, the first groove 1 is not parallel to the insertion direction of the artificial joint stem 100 into the bone, but is inclined. Having a component along the width direction of the base 10 can resist sinking, which is the phenomenon in which the artificial joint stem sinks downward after insertion. The second groove 2 may also have both a component along the width direction of the base 10 and a component along a direction perpendicular to the width direction.

[0021] The component along the width direction of the base body 10 and the component along the direction perpendicular to the width direction may be the same in size, or one of them may be larger. For example, as shown in FIG. 5, the component along the width direction of the first groove 1 of the base body 10 may be smaller than the component along the direction perpendicular to the width direction. Here, "the component along the width direction of the base body 10 is smaller than the component along the direction perpendicular to the width direction" means that the absolute value of the slope of the line α is greater than 1. In this case, it is possible to more easily insert the artificial joint stem 100 into the bone. Similarly, the component along the width direction of the base body 10 of the second groove 2 may be smaller than the component along the direction perpendicular to the width direction.

[0022] The groove may have a straight portion or a curved portion. For example, the first groove 1 may have a plurality of straight portions. The plurality of straight portions may be parallel to one another, may intersect at right angles, or may be randomly arranged. Figure 6 shows an artificial joint stem 100 in which the first groove 1 has a plurality of straight portions that intersect at right angles.

[0023] 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 coating 20 is exposed 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 coating 20 is exposed 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 coating 20 is exposed. In this case, it is possible to more easily insert the artificial joint stem 100 into the bone. On the other hand, FIG. 7 shows an artificial joint stem 100 in which 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 coating 20 is exposed. In this case, it is possible to improve antibacterial properties.

[0024] The ratio between the length L1 of the surface of the substrate 10 along the orthogonal direction perpendicular to the width direction of the substrate 10 in the region where the coating 20 is disposed and the length L2 of the region where the surface of the substrate 10 is exposed from the coating 20 along the orthogonal direction can also be determined appropriately depending on the application, etc. Lengths L1 and L2 may be the same, or one may be larger. For example, in FIG. 5, length L1 is smaller than length L2. This makes it easier to insert the artificial joint stem 100 into the bone. Here, length L1 represents the maximum length along the Y-axis direction in the region where the coating 20 is disposed. In other words, length 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 in the region where the coating 20 is disposed. Length L2 also represents the maximum length along the Y-axis direction in the region where the surface of the substrate 10 is exposed from the coating 20. That is, the length 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 in the region where the surface of the substrate 10 is exposed from the coating 20.

[0025] 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.

[0026] 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.

[0027] The coating 20 includes a calcium phosphate-based material and an antibacterial material. The calcium phosphate-based material may be, for example, one or a mixture of two or more selected from the group consisting of hydroxyapatite, α-tricalcium phosphate, β-tricalcium phosphate, tetracalcium phosphate, octacalcium phosphate, and calcium phosphate glass. The antibacterial material may be a natural antibacterial agent, an organic antibacterial agent, or an inorganic antibacterial agent. Examples of natural antibacterial agents include hinokitiol, organic antibacterial agents include benzalkonium chloride, and inorganic antibacterial agents include metals such as silver, copper, and zinc. In addition to the calcium phosphate-based material and the antibacterial material, the coating 20 may also include glass ceramics or an antibacterial drug such as penicillin or vancomycin.

[0028] 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. If the concentration of the antibacterial material is 0.05% by weight or more, sufficient antibacterial properties can be obtained. Furthermore, if the concentration of the antibacterial material is 3.00% by weight or less, the burden on living tissue can be reduced.

[0029] There may be a concentration gradient of the antibacterial material in 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 makes it possible to more effectively reduce the intrusion 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.

[0030] A boundary line defined by the presence or absence of coating 20 may exist on substrate 10. The length of the boundary line around substrate 10 may be greater than the length of the perimeter of a portion of substrate 10 located above or below the boundary line. For example, the portion of substrate 10 where the boundary line exists may be raised like a knot.

[0031] 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.

[0032] The substrate 10 may have a rough surface located on its surface. The rough surface may be covered with the coating 20, or may be exposed from the coating 20. Alternatively, only a portion of the rough surface may be covered with the coating 20, with another portion of the rough surface being exposed from the coating 20. The grooves may or may not be located on the rough surface. For example, only the first grooves 1 may be located on the rough surface. The surface roughness of the inner surface of the groove located on the rough surface may be smaller than the surface roughness of the rough surface of the substrate 10.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] FIG. 8 is an A-A' cross section including the first groove 1, showing an example different from those in FIGS. 3 and 4. In FIG. 8, 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. 8, a coating 20 is formed on the layer member 30, and only the first groove 1 is located as the groove.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] Although the above describes an artificial joint stem 100 having the groove, the shape of the groove is not particularly limited. For example, circular, polygonal, or irregularly shaped recesses may be formed instead of grooves. An artificial joint stem 100 having such recesses is also encompassed by the present disclosure. For example, the artificial joint stem 100 according to the present disclosure includes a base 10 having one or more recesses disposed on its surface, and a coating 20 containing a calcium phosphate material and an antibacterial material disposed on a portion of the surface of the base 10. The recesses located in the area where the coating 20 is disposed are defined as first recesses, and the recesses located in the area where the surface of the base 10 is exposed through the coating 20 are defined as second recesses. The total opening area of ​​the first recesses may be smaller than the total opening area of ​​the second recesses. The relationship between the first recesses and the second recesses may be similar to that between the first groove 1 and the second groove 2 described above. The opening areas of the first recesses and the second recesses can be calculated using image analysis software or the like.

[0041] 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.

[0042] 9, 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.

[0043] The coating 20 disposed in the boundary region 60 may be disposed only on the buried portion 40. In other words, the coating 20 does not have to be disposed on the exposed portion 50. This can reduce irritation to soft tissue that the exposed portion 50 may come into contact with.

[0044] The first groove 1 does not have to reach the boundary between the buried portion 40 and the exposed portion 50. In other words, the end of the first groove 1 may be located in the buried portion 40. In this case, the invasion of bacteria can be further reduced.

[0045] 9, the base 10 may include a main body portion 40' 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 paired with the stem for the artificial joint.

[0046] The main body 40' has a lower portion 40'a having a central axis C extending in the vertical direction, and an upper portion 40'b that extends vertically continuously from the lower portion 40'a and has a curved shape such that its center moves away from the central axis C as it extends upward. The upper portion 40'b has an upper end surface that is offset from the central axis C, and a neck portion 50' is connected to the upper end surface. The neck portion 50' has a width smaller than that of the upper end surface of the main body 40'. In other words, the neck portion 50' can be said to be a protrusion 50' that protrudes in an oblique direction inclined from the central axis C of the main body 40'.

[0047] 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.

[0048] An artificial joint stem 101 shown in FIG. 12 is also included in the artificial joint stem according to the present disclosure. For example, the base body 10 may have a concavely curved medial portion 13 and a convexly curved lateral portion 14. The upper end of the first groove 1 may be located in the curved portion on the medial side. Here, the upper end of the first groove 1 may be bent toward the medial portion 13. In other words, the first groove 1 may have a first portion 1a extending in the vertical direction of the base body 10 and a second portion 1b connected to the first portion 1a and having a component along the width direction of the base body 10. The depth of the second groove 2 may be smaller than the depth of the first groove 1.

[0049] The substrate 10 may also have a first groove set 15 in which the first groove 1 and the second groove 2 are connected, and a second groove set 16 in which the first groove 1 and the second groove 2 are connected and the first groove 1 extends further toward the upper end of the coating 20 than the first groove set 15.

[0050] Furthermore, the base 10 may have a plurality of first groove sets 15. The plurality of first groove sets 15 may be aligned in the width direction of the base 10. Of the plurality of first groove sets 15, the first groove set 15 located on the outer portion 14 side may be located higher than the first groove set 15 located on the inner portion 13 side.

[0051] An artificial joint stem 102 shown in FIG. 13 is also included in the artificial joint stems of the present disclosure. For example, the base 10 may have multiple grooves, and the grooves located in the upper part of the base 10 may be wider than the grooves located in the lower part of the base 10. The grooves may have a component along the width direction of the base 10. FIG. 14 shows the CC' cross section of FIG. 13. As shown in FIG. 14, the grooves along the width direction of the base 10 (second part 1b of the first groove 1) may become shallower toward the top.

[0052] The boundary line defined by the presence or absence of the coating 20 may include a first boundary line 21 located below the substrate 10 with respect to the coating 20. The boundary line may also include a second boundary line 22 located above the substrate 10 with respect to the coating 20. The first boundary line 21 may intersect with the linear portion of the groove. Here, the first boundary line 21 may intersect with the linear portion of the groove obliquely. In other words, the first boundary line 21 does not have to be perpendicular to the linear portion of the groove.

[0053] The boundary line may have a component along the vertical direction that is larger than a component along the width direction of the base 10. In other words, when viewed in a plan view from a direction perpendicular to the XY plane in Fig. 13, the slope of the line connecting both ends of the boundary line on the XY coordinate system may exceed 1. In Fig. 13, the slope of the line β connecting both ends of the first boundary line 1 on the XY coordinate system exceeds 1.

[0054] Furthermore, first boundary line 21 may have a first portion 21a extending in a direction intersecting the groove and a second portion 21b extending in a direction along the groove. Second portion 21b of first boundary line 21 may be disposed away from the groove. In other words, second portion 21b of first boundary line 21 may not be in contact with the groove. The same applies to second boundary line 22.

[0055] The first groove 1 and the second groove 2 may be connected, and the first groove 1 may have a first portion 1a extending in the vertical direction of the base 10, and a second portion 1b connected to the first portion 1a and having a component along the width direction of the base 10. As shown in FIG. 13 , the second boundary line 22 may extend in a direction along the second portion 1b of the first groove 1.

[0056] 13, the second boundary line 22 may be disposed so as to tilt upward from the inner portion 13 toward the outer portion 14. Also, as shown in FIG. 13, the first boundary line 21 may be located below the apex 13a of the recess in the inner portion 13. The first boundary line 21 may be located below the apex 14a of the protrusion in the outer portion 14. Alternatively, the first boundary line 21 may be located above the apex 14a of the protrusion in the outer portion 14.

[0057] The artificial joint stem 103 shown in Figure 15 is also included in the artificial joint stems of the present disclosure. For example, the boundary line and the groove may intersect at an acute angle. In Figure 15, of the angles formed by the first boundary line 21 and the second groove 2, the angle γ on the inner side of the medial portion 13 is an acute angle.

[0058] The artificial joint stem 104 shown in FIG. 16 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 region 70, a non-roughened region 80, and a grooved region 90. The roughened region 70 has a roughened surface. The non-roughened region 80 is a region without a roughened surface. The grooved region 90 has grooves. For example, the roughened region 70 may be a region with a roughened surface but no grooves, the non-roughened region 80 may be a region with neither a roughened surface nor grooves, and the grooved region 90 may be a region with no roughened surface but grooves. The coating 20 may cover at least one of the roughened region 70, the non-roughened region 80, and the grooved region 90. The area of ​​the roughened region 70 may be smaller than the area of ​​the non-roughened region 80. In the width direction of the base body 10, the length of the roughened region 70 may be greater than the length of the non-roughened 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. 16 , 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.

[0059] Artificial joint stems 105, 106, and 107 shown in FIG. 17 are also included in the artificial joint stems according to the present disclosure. For example, as in the artificial joint stem 105, only the second groove 2 may extend along a portion of the first boundary line 21. As in the artificial joint stem 106, multiple second grooves 2 may be arranged circumferentially at the distal end of the base body 10. Furthermore, the coating 20 and the second groove 2 may not be in contact with each other. As in the artificial joint stem 107, the grooves may be closer to either the medial portion 13 or the lateral portion 14. In FIG. 17, the first groove 1 and second groove 2 of the artificial joint stem 107 are closer to the lateral portion 14.

[0060] 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, a groove forming step, and a coating forming step. The preparation step involves preparing a substrate 10 having a surface including a first region and a second region. The groove forming step involves forming one or more grooves on the surface of the substrate 10. The coating forming step involves forming a coating 20 containing a calcium phosphate material and an antibacterial material on a portion (first region) of the surface of the substrate 10.

[0061] In the artificial joint stem of the present disclosure, the groove located in the region where the coating 20 is disposed becomes the first groove 1, and the groove located in the region where the surface of the base 10 is exposed from the coating 20 becomes the second groove 2. That is, in the groove forming step, the groove formed in the first region becomes the first groove 1, and the groove formed in the second region becomes the second groove. In the groove forming step, the grooves are formed so that the total length of the first grooves 1 is smaller than the total length of the second grooves 2. In the coating forming step, the coating 20 is formed in the first region of the surface of the base 10 where the first grooves 1 are formed. In this way, the artificial joint stem 100 as described above can be obtained.

[0062] In the preparation step, the base 10 can be prepared by forming a metal material into a desired shape using a mold or an additive manufacturing method.

[0063] In the groove forming step, the grooves can be formed by at least one of cutting, rolling, and pressing. In this embodiment, the grooves are formed by, for example, milling, which is a type of cutting method. In addition, if the artificial joint stem has the above-mentioned recess, it is sufficient to have a recess forming step instead of the groove forming step, using a method similar to the groove forming step.

[0064] The groove forming process can be followed by a coating forming process. 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 process. The material that constitutes the coating is also referred to as the coating material.

[0065] A first protective material may be used to form the coating 20 only in the first region. In this case, a step of arranging the first protective material so as to expose the first region and protect the second region, so as not to form a coating in the second region, may be further included prior to the coating formation step. The first protective material may be, for example, masking tape or a partition. Alternatively, a jig covering the substrate 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 substrate 10. When masking tape is used as the first protective material, for example, the first protective material may be arranged in the shape of the second region. When a jig covering the substrate 10 is used, the shape of the jig is not particularly limited, but may be, for example, cylindrical. The cross section of the cylindrical jig may be polygonal or circular.

[0066] When a partition is used, the coating 20 can be formed in a specific region by placing the partition in a predetermined position. When a jig is used, the coating 20 can be formed in a specific region by placing the jig in a predetermined position. In this case, for example, the coating 20 can be selectively formed only in a desired region by adjusting the positional relationship between the discharge nozzle discharging the thermal spray material, additive manufacturing material, chemical etching material, blasting material, or coating material and the partition. In this case, the tip of the discharge nozzle may be positioned in a straight line with the surface of the desired region without the partition separating them. In addition, hereinafter, the thermal spray material, additive manufacturing material, chemical etching material, blasting material, or coating material discharged from the discharge nozzle will also be referred to as the discharged material. Without being limited thereto, the coating 20 may be formed while the substrate 10, the partition, and the discharge nozzle are fixed, or the coating 20 may be formed while at least one of them is moved. The angle of the discharge nozzle may be fixed or changed while the coating 20 is formed.

[0067] 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.

[0068] A roughening step can also be carried out before the groove forming 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.

[0069] 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.

[0070] A second protective material may be used to form a roughened surface only in the desired region. In this case, a step of arranging the second protective material to expose the roughened region while protecting the other regions may be further included before the roughening step, so that the roughened surface is not formed in any region 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. In other words, the second protective material may be arranged to protect a part of the first region and the second region, or the second region.

[0071] The second protective material may be, for example, masking tape or a partition. Alternatively, a jig covering 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 protective material may or may not be in contact with the base 10. When a jig covering the base 10 is used as the second protective material, the shape of the jig is not particularly limited, and may be, for example, cylindrical. The cross section of the cylindrical jig may be polygonal or circular.

[0072] When a partition is used, a roughened surface can be formed in a specific area by placing the partition in a predetermined position. When a jig is used, a roughened surface can be formed in a specific area by placing the jig in a predetermined position. In this case, for example, by adjusting the positional relationship between the discharge nozzle discharging the thermal spray material, additive manufacturing material, chemical etching material, blasting material, or coating material and the partition, a roughened surface can be selectively formed only in the desired area. In this case, the tip of the discharge nozzle may be positioned in a straight line with the surface of the desired area without the partition separating them. In addition, hereinafter, the thermal spray material, additive manufacturing material, chemical etching material, blasting material, or coating material discharged from the discharge nozzle will also be referred to as the discharged material. Without being limited to these, the roughened surface may be formed while the substrate 10, the partition, and the discharge nozzle are fixed, or while at least one of them is moved. The angle of the discharge nozzle may be fixed or changed to form the roughened surface. As with the coating 20, a roughened surface may be formed only in the desired area without using a protective material.

[0073] In view of the above, when the artificial joint stem of the present disclosure has a roughened surface, for example, in the surface roughening step, a second protective material may be placed on the base 10 so as to expose a portion of the surface of the base 10 while protecting another portion of the base 10, and a roughened surface may be formed on the exposed surface. Furthermore, the manufacturing method according to the present disclosure may further include a step of removing the second protective material after the surface roughening step and before the groove forming step.

[0074] 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.

[0075] 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 surface roughening step, a step of attaching the second masking tape to a portion of the surface of the substrate 10 while exposing the other portion of the surface of the substrate 10.

[0076] Furthermore, in the coating formation step, a first protective material may be placed on the substrate 10 so as to expose a portion of the surface of the substrate 10 while protecting another portion of the substrate 10, and the coating 20 may be formed on the exposed portion of the surface. The first protective material may 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 the present disclosure may further include, before the coating formation step, a step of attaching the first masking tape to the other portion of the substrate 10 while exposing the surface of the substrate 10.

[0077] The second protective material can be made of a material with higher heat resistance than the first protective material. For example, a material that does not melt or thermally decompose for one minute under thermal spray conditions at 8000°C can be used as the second protective material, and a material that does not melt or thermally decompose for one minute under thermal spray conditions at 3000°C can be used as the first protective material. Specific examples of such materials include composite materials of glass and resin.

[0078] 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.

[0079] 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.

[0080] To summarize the above, the steps can be performed in the order shown in Figure 10, for example. Figure 10 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 groove forming step can be performed. Then, a first protective material is placed, followed by a coating forming step.

[0081] 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.

[0082] The method for manufacturing the grooved artificial joint stem 100 has been described above, but the manufacturing method according to the present disclosure is not particularly limited to the above steps. For example, in the above manufacturing method, an example has been described in which a roughening step for roughening the surface of the base body 10 is followed by a groove forming step for forming grooves, and then a coating forming step for forming a coating, but the groove forming step may be followed by a roughening step, and then a coating forming step.

[0083] 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.

[0084] 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. The fourth protective material may be, for example, a fourth masking tape. In this case, 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 while exposing the first roughened region and the second roughened region. 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.

[0085] 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.

[0086] 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.

[0087] [3. Use of artificial joint stems] 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.

[0088] 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 11. 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.

[0089] 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]

[0090] 1 1st groove 2 2nd groove 10 Base 20 Coating 100 Artificial joint stem 1000 Artificial Hip Joint

Claims

1. a substrate having a groove located on a surface thereof; a layer member positioned on a portion of the substrate; a coating located on the layered member, the coating including a calcium phosphate-based material and an antibacterial material; An artificial joint stem, wherein, among the grooves, a groove formed on the layered member and covered with the coating is defined as a first groove, and a groove located in an area where the surface of the base body is exposed from the coating is defined as a second groove, and the width of the first groove is smaller than the width of the second groove.

2. The prosthetic stem of claim 1 , wherein the sum of the lengths of the first grooves is less than the sum of the lengths of the second grooves.

3. The artificial joint stem according to claim 1 or 2, wherein the first groove is connected to the second groove.

4. 4. The artificial joint stem according to claim 1, wherein only the first groove is located in the region of the base body where the layer member is located.

5. The artificial joint stem according to any one of claims 1 to 4, wherein the surface of the layered member is rough.

6. The artificial joint stem according to any one of claims 1 to 5, wherein the layered member is made of a titanium alloy.

7. 7. The artificial joint stem according to claim 1, wherein the thickness of said layer member is greater than the thickness of said coating.

8. An artificial joint stem according to any one of claims 1 to 7, wherein the base body has a rough surface located on its surface, and the surface roughness of the inner surface of the groove located on the rough surface is smaller than the surface roughness of the rough surface other than the groove.

9. The artificial joint stem according to any one of claims 1 to 8, wherein a concentration gradient of the antibacterial material exists in the coating.

10. An artificial joint stem according to any one of claims 1 to 9, wherein the boundary line defined by the presence or absence of a coating on the surface of the base body has a first part extending in a direction intersecting the groove and a second part extending in a direction along the groove.

11. a substrate having depressions located on a surface thereof; a layer member positioned on a portion of the substrate; a coating located on the layered member, the coating including a calcium phosphate-based material and an antibacterial material; An artificial joint stem, wherein, among the recesses, a recess formed on the layered member and covered with the coating is defined as a first recess, and a recess located in an area where the surface of the base body is exposed from the coating is defined as a second recess, and the width of the first recess is smaller than the width of the second recess.

12. An artificial hip joint comprising the artificial joint stem according to any one of claims 1 to 11, a femoral head, and an acetabular cup, wherein the artificial joint stem is an artificial hip joint stem.

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