Stem for artificial joint

Abstract

The present invention enables stable fixation to a bone. This stem for an artificial joint has a substrate having a surface, and a first coating film located in a first area on the surface of the substrate. The first area includes a second area having a part where the first coating film is not located. The second area includes a third area where the first coating film is located and around which the first coating film is not located.

Description

Artificial joint stems

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

[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 with coatings are known for their antibacterial properties and bone fixation properties.

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

[0004] Japan Special Table No. 2011-512959

[0005] There is a demand for a bioimplant that can be stably fixed to the above bone.

[0006] The artificial joint stem of the present disclosure comprises a substrate having a surface and a first coating located in a first region on the surface of the substrate, the first region including a second region having a portion where the first coating is not located, and the second region including a third region where the first coating is located and around which the first coating is not located.

[0007] According to the invention of the present disclosure, it is possible to provide a stem for an artificial joint that can be stably fixed to a bone.

[0008] 1 is a schematic diagram showing an artificial joint stem according to one embodiment; FIG. 1 is a diagram showing an outline of a second region of a base body of an artificial joint stem according to one embodiment; FIG. 1 is a diagram showing a cross section of an artificial joint stem according to one embodiment, taken along line IA-IA in FIG. 1; FIG. 1 is a diagram showing an outline of a second region of a base body in a manufacturing process of an artificial joint stem according to one embodiment; FIG. 1 is a diagram showing a cross section of an artificial joint stem according to one embodiment, taken along line IB-IB in FIG. 1; FIG. 1 is a diagram showing a cross section of an artificial joint stem according to one embodiment, taken along line IC-IC in FIG. 1; FIG. 1 is a schematic diagram showing an artificial joint stem according to one embodiment; FIG. 1 is a diagram showing an outline of a second region of a base body of an artificial joint stem according to one embodiment; FIG. 1 is a diagram showing a cross section of an artificial joint stem according to one embodiment, taken along line VIII-VIII in FIG. 7; FIG. 1 is a schematic diagram showing an artificial joint stem according to one embodiment; FIG. 1 is a diagram showing a cross section of an artificial joint stem according to one embodiment, taken along line IB-IB in FIG. FIG. 2 is a diagram showing a cross section of a stem for an artificial joint according to one embodiment, and is a cross section taken along the arrow IB-IB line in FIG. 1. FIG. 3 is a process chart showing a method for manufacturing a stem for an artificial joint according to one embodiment. FIG. 4 is a schematic diagram showing an artificial hip joint according to one embodiment. FIG. 5 is a schematic diagram showing a stem for an artificial joint according to one embodiment. FIG. 6 is a schematic diagram showing a stem for an artificial joint according to one embodiment. FIG. 7 is a schematic diagram showing a stem for an artificial joint according to one embodiment. FIG. 8 is a schematic diagram showing a stem for an artificial joint according to one embodiment. FIG. 9 is a schematic diagram showing a cross section of a stem for an artificial joint according to one embodiment. FIG. 10 is a schematic diagram showing a stem for an artificial joint according to one embodiment. FIG. 11 is a schematic diagram showing a stem for an artificial joint according to one embodiment. FIG. 12 is a schematic diagram showing a stem for an artificial joint according to one embodiment. FIG. 13 is a schematic diagram showing a stem for an artificial joint according to one embodiment. FIG. 14 is a schematic diagram showing a stem for an artificial joint according to one embodiment. FIG. 15 is a schematic diagram showing a stem for an artificial joint according to one embodiment. FIG. 16 is a schematic diagram showing a stem for an artificial joint according to one embodiment. 1 is a schematic diagram showing an artificial joint stem according to one embodiment. FIG.Fig. 1 is a schematic diagram showing a stem for an artificial joint according to one embodiment. Fig. 2 is a schematic diagram showing a stem for an artificial joint according to one embodiment. Fig. 3 is a schematic diagram showing a stem for an artificial joint according to one embodiment. Fig. 4 is a schematic diagram showing a stem for an artificial joint according to one embodiment.

[0009] 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."

[0010] 1. Artificial Joint Stem First, the configuration of an artificial joint stem 100 according to one embodiment will be described with reference to Figures 1 to 7. The artificial joint stem 100 comprises a base body 10 and a first coating 20 located in a first region on the surface of the base body 10. In this specification, the term "surface" refers to the outermost surface of each component. The term "surface" includes not only the surface that can be seen externally, but also the surface on which a coating such as the first coating 20 is provided.

[0011] The artificial joint stem 100 has an embedded portion 40 that is embedded in the bone and an exposed portion 50 that is exposed from the bone. Hereinafter, the side of the embedded portion 40 will be referred to as the distal side, and the side of the exposed portion 50 will be referred to as the proximal side. In other words, the side of the artificial joint stem 100 that is embedded in the bone when in use will be referred to as the distal side, and the opposite side will be referred to as the proximal side. The embedded portion 40 has a shape that extends in a tapered manner from the proximal side toward the distal side.

[0012] In Fig. 1, the first coating 20 is formed in a first region A1 of the embedded portion 40 that is close to the exposed portion 50, and a distal region AF that is far from the exposed portion 50 is exposed from the first coating 20. This distal region AF is mirror-finished. For example, only a portion of the distal region AF may be mirror-finished. For example, the distal region AF may be processed by chemical etching or blasting.

[0013] Furthermore, grooves 1 having an elongated shape are located on the surface of the base body 10. For example, the width of groove 1 may be 2 to 5 mm. For example, the depth of groove 1 may be 1 to 2.5 mm. This groove 1 contributes to facilitating insertion of the artificial joint stem 100 into bone. The number of grooves 1 may be one. The number of grooves 1 may be multiple. The grooves 1 include groove 1a located in the first region A1 where the first coating 20 is disposed, and groove 1b located in the distal region AF where the surface of the base body 10 is exposed from the first coating 20. In other words, the first region A1 where the first coating 20 is disposed includes at least a portion of groove 1.

[0014] The length of groove 1a is shorter than the length of groove 1b. Groove 1a does not have to be present. In other words, groove 1 only needs to include groove 1b. Groove 1 may include only groove 1b. As a result, it is possible to adjust the fixation of the artificial joint stem 100 to the bone, etc. The ratio of the length of groove 1a to the length of groove 1b may be changed as appropriate depending on the size of the artificial joint stem 100.

[0015] Fig. 2 is a diagram showing an outline of the second region A2. Fig. 3 is a cross-sectional view taken along line IA-IA in Fig. 1. The first coating 20 is located in the first region A1 on the surface of the base body 10. As a result, as shown in Fig. 3, the first region A1 is higher than the distal region AF where the first coating 20 is not provided. Therefore, when the artificial joint stem 100 is embedded in bone, the first region A1 can be mainly brought into contact with the bone.

[0016] Here, the surface roughness in the first region A1 of the base 10 is greater than the surface roughness in the distal region AF of the base 10. An example of an index of surface roughness is the arithmetic mean roughness Sa (ISO 25178). The surface roughness (Sa) of the first region A1 may be, for example, 10 to 80 μm. The surface roughness (Sa) of the first region A1 may be, for example, 20 to 80 μm. The surface roughness (Sa) of the first region A1 may be, for example, 30 to 70 μm. Furthermore, the surface roughness (Sa) of the base 10 in the distal region AF may be, for example, less than 1.0 μm.

[0017] The surface roughness (Sa) of the first region A1 can be determined from the measurement results of the entire first region A1. The surface roughness (Sa) of the distal region AF can be determined from the measurement results of the entire distal region AF. For example, the first region A1 may have a localized portion where the surface roughness is smaller than the surface roughness of the distal region AF. For example, the distal region AF may have a localized portion where the surface roughness is greater than the surface roughness of the first region A1.

[0018] 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. The surface roughness (Sa) may also be determined from the measurement results of a partial region of the target region. The measurement of the surface roughness is not limited to the above-described method. Alternatively, the surface roughness (Sa) may be calculated from an image captured by an optical microscope or an electron microscope.

[0019] The surface of the first coating 20 may be rough. In this case, the area that mainly comes into contact with the bone is rough, which can improve the bonding with the bone. In this embodiment, the first coating 20 is formed by a thermal spraying method as described below, but the present invention is not limited to this. The first coating 20 may also have a porous structure.

[0020] The upper limit of the height of the first coating 20 may be, for example, 1000 μm or less. The upper limit of the height of the first coating 20 may be, for example, 700 μm or less. Furthermore, the surface roughness (Sa) of the first coating 20 may be, for example, 10 to 80 μm. The surface roughness (Sa) of the first coating 20 may be, for example, 20 to 80 μm. The surface roughness (Sa) of the first coating 20 may be, for example, 30 to 70 μm.

[0021] The material of the first coating 20 can be any of the materials exemplified below as the material of the substrate 10. For example, the first coating 20 may be made of a metal. The material of the first coating 20 and the material of the substrate 10 may be the same. The material of the first coating 20 and the material of the substrate 10 may be different. The material of the first coating 20 may be, for example, a material containing pure titanium or a titanium alloy as a main component. In this embodiment, the first coating 20 is made of pure titanium.

[0022] The first region A1 includes a second region A2 having a portion where the first coating 20 is not located. The second region A2 is adjacent to a distal region AF exposed from the first coating 20. The second region A2 is a region at the distal end of the first region A1.

[0023] The second region A2 includes a third region A3, which is a region where the first coating 20 is located but is not surrounded by the first coating 20. As a result, the first coating 20 located in the third region A3 forms an island shape surrounded by the region where the first coating 20 is not located. When the artificial joint stem 100 configured as described above is inserted into a bone, the third region A3 is considered to be a region in the first region A1 that has a lower fixation to the bone, but a region that has a higher fixation to the bone than the distal region AF. Therefore, when force is applied to the artificial joint stem 100, the load on the bone that is applied to the boundary region between the first region A1 and the distal region AF can be dispersed. Therefore, the artificial joint stem 100 can be stably fixed to the bone.

[0024] The average height of the first coating 20 in the second region A2 may be lower than the average height of the first coating 20 in the entire first region A1. The second region A2 has a plurality of third regions A3. The shapes of the plurality of third regions A3 may be different from one another. For example, the shape of the first coating 20 in the third region A3 may be substantially hemispherical. For example, when the third region A3 is viewed from above, the shape of the first coating 20 in the third region A3 may be substantially circular or elliptical.

[0025] As shown in FIG. 2 , the second region A2 includes a fourth region A4, which is a region where the first coating 20 is not present and is surrounded by the first coating 20. The fourth region A4 has a basin shape. When the artificial joint stem 100 having the above configuration is inserted into a bone, the fourth region A4 is considered to be a region of the first region A1 that has a lower fixation to the bone, but is also a region that has a higher fixation to the bone than the distal region AF. Therefore, when a force is applied to the artificial joint stem 100, the load on the bone that is applied to the boundary region between the first region A1 and the distal region AF can be dispersed. As a result, the artificial joint stem 100 can be stably fixed to the bone.

[0026] The second region A2 has a plurality of fourth regions A4. The shapes of the plurality of fourth regions A4 may be different from one another. The areas of the plurality of fourth regions A4 may be different from one another. The area of ​​the fourth regions A4 in the entire second region A2 may be smaller than the area of ​​the third regions A3 in the entire second region A2. The area of ​​the fourth regions A4 in the entire second region A2 may be larger than the area of ​​the third regions A3 in the entire second region A2.

[0027] 3, in the region of the first region A1 adjacent to the second region A2, the thickness of the first coating 20 becomes thinner toward the second region A2, thereby reducing stress concentration at the edge of the first coating 20. In the region of the first region A1 adjacent to the second region A2, the surface roughness of the first coating 20 may become lower as the thickness of the first coating 20 becomes thinner toward the second region A2.

[0028] Here, a method for forming the first coating 20 will be described. As described above, the sprayed layer 21 is formed by spraying droplets of spray material or semi-molten spray material onto the first region A1 on the surface of the substrate 10. The thickness of the sprayed layer 21 is adjusted by changing conditions such as the time for spraying the spray material, the temperature at which the spray material is sprayed, or the pressure at which the spray material is sprayed. As a result, the sprayed layer 21 becomes thinner toward the edge.

[0029] 4 is a diagram showing an overview of the second region A2, showing the state after the thermal spray layer 21 has been formed. As shown in Fig. 4, in the second region A2, which is the edge, the thermal spray layer 21 is thin, and there are portions where the surface of the substrate 10 is exposed. In the second region A2, there are multiple portions where the surface of the substrate 10 is exposed.

[0030] Next, the surface roughness of the thermal spray layer 21 is adjusted. As a result, a first coating 20 as shown in FIG. 2 is formed in the first region A1. The surface roughness can be adjusted by mechanical processing methods such as cutting, grinding, or sandblasting. The surface roughness can also be adjusted by chemical processing methods such as etching with acid. The surface roughness can also be adjusted by a method that appropriately combines mechanical and chemical processing methods.

[0031] 5 is a cross-sectional view taken along the arrow IB-IB line in FIG. 1. As described above, the groove 1a of the groove 1 is part of the first region A1, and the first coating 20 is formed on the groove 1a. As shown in FIG. 5, for the inside and outside of adjacent grooves 1a in the first region A1, the thickness of the first coating 20 inside the groove 1a is greater than the thickness of the first coating outside the groove 1a. This makes it possible to reduce the distance between the first coating 20 inside the groove 1a and the bone.

[0032] 5, the thickness of the first coating 20 inside the groove 1a increases as the groove 1a advances in the depth direction. Inside the groove 1a, the thickness of the first coating 20 at the deepest position of the groove 1a is thicker than the thickness of the first coating 20 at the shallowest position of the groove 1a. Inside the groove 1a, the thickness of the first coating 20 is thickest at the deepest position of the groove 1a.

[0033] Furthermore, with respect to the inside and outside of adjacent grooves 1a in the first region A1, the surface roughness of the first coating 20 inside the groove 1a is greater than the surface roughness of the first coating 20 outside the groove 1a, thereby increasing the friction generated between the inside of the groove 1a and the bone.

[0034] Figure 6 is a cross-sectional view taken along the arrow IC-IC line in Figure 1. As shown in Figure 6, even inside the groove 1a, the first region A1 includes a second region A2 where a portion where the first coating 20 is not formed exists. The second region A2 is adjacent to the distal region AF exposed from the first coating 20. The second region A2 inside the groove 1a is adjacent to the second region A2 outside the groove 1a. The second region A2 inside the groove 1a does not have to be adjacent to the second region A2 outside the groove 1a.

[0035] Even inside the groove 1a, the second region A2 includes a third region A3, which is a region where the first coating 20 is formed and a region where the first coating 20 is not formed around the second region A2. Inside the groove 1a, the second region A2 does not necessarily have to have the third region A3. The second region A2 may have the third region A3 only inside the groove 1a.

[0036] 6, within the groove 1a, in the region of the first region A1 adjacent to the second region A2, the thickness of the first coating 20 becomes thinner toward the second region A2. That is, the thickness of the first coating 20 within the groove 1a becomes thinner from the proximal side toward the distal side. This reduces stress concentration at the edge of the first coating 20 when the inner surface of the groove 1a comes into contact with bone.

[0037] 6, in the second region A2, the area of ​​the first coating 20 located inside the groove 1a is larger than the area of ​​the first coating 20 located outside the groove 1a. That is, in the second region A2, the ratio of the surface area of ​​the region where the first coating 20 is not located to the surface area inside the groove 1a is smaller than the ratio of the surface area of ​​the region where the first coating 20 is not located to the surface area outside the groove 1a.

[0038] As shown in FIG. 5 , in the first region A1, the surface roughness of the inside of groove 1a is greater than the surface roughness of the outside of groove 1a. In the distal region AF, the surface roughness of the inside of groove 1b is greater than the surface roughness of the outside of groove 1b. For example, the surface roughness (Sa) of the inside of groove 1a may be 0.4 μm or more, and the surface roughness (Sa) of the outside of groove 1a may be less than 0.05 μm. As shown in FIG. 5 , the surface roughness of the inside of groove 1 may become rougher as it progresses in the depth direction of groove 1. In the distal region AF, the surface roughness of the inside of groove 1 may be roughest at the deepest part of groove 1.

[0039] Figures 7 to 9 show an example different from Figures 1 to 3. In the artificial joint stem 100 shown in Figures 7 to 9, a second coating 30 is provided in a first region A1 on the surface of the base body 10 so as to cover the first coating 20. In the first region A1 on the surface of the base body 10, the second coating 30 is located on the first coating 20.

[0040] The second coating 30 is a different material from the first coating 20. The second coating 30 includes a calcium phosphate-based material and an antibacterial material. The second coating 30 may be configured without the antibacterial material. The calcium phosphate-based material is expected to improve adhesion to bone. The antibacterial material is expected to reduce bacterial adhesion and proliferation.

[0041] Here, the surface of the second coating 30 has a greater surface roughness than the surface of the substrate 10 in the distal region AF. An example of an index of surface roughness is the arithmetic mean roughness Sa (ISO 25178). The surface roughness (Sa) of the second coating 30 may be, for example, 10 to 80 μm. The surface roughness (Sa) of the second coating 30 may be, for example, 20 to 80 μm. The surface roughness (Sa) of the second coating 30 may be, for example, 30 to 70 μm.

[0042] The surface roughness (Sa) of the second coating 30 can be determined from the measurement results of the entire first region A1. For example, the first region A1 may have a portion where the surface roughness of the second coating 30 is locally smaller than the surface roughness of the substrate 10 in the distal region AF. For example, the distal region AF may have a portion where the surface roughness is locally greater than the surface roughness of the second coating 30 in the first region A1.

[0043] Here, the second coating 30 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 second coating 30. 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, if 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 a first region A1 covered with the second coating 30 and a distal region AF exposed from the second coating 30, excessive adhesion to the bone can be reduced. In other words, adhesion to the bone and antibacterial properties can be achieved at the same time.

[0044] The first region A1 is at least partially covered by the second coating 30. That is, the first region A1 may be entirely or partially covered by the second coating 30. The surface of the second coating 30 located in the first region A1 has a greater surface roughness than the surface of the base 10 in the distal region AF. By providing a region with a greater surface roughness, the adhesion to the bone can be improved. For example, by forming a rough surface on the first coating 20 in the first region A1 and covering the rough surface with the second coating 30, the surface roughness of the second coating 30 located in the first region A1 can be increased.

[0045] The surface roughness of the rough surface located in the first region A1 is greater than the surface roughness of the distal region AF. Therefore, the surface roughness of the second coating 30 located in the first region A1 is greater than the surface roughness of the distal region AF. The surface roughness (Sa) of the rough surface located in the first region A1 may be, for example, 10 to 80 μm. The surface roughness (Sa) of the rough surface located in the first region A1 may be, for example, 20 to 80 μm. The surface roughness (Sa) of the rough surface located in the first region A1 may be, for example, 30 to 70 μm. The surface roughness of the rough surface can be measured, for example, by cutting the artificial joint stem 100 and observing the cut surface using a scanning electron microscope or the like.

[0046] Figure 10 shows another example different from those shown in Figures 1 to 3. In the artificial joint stem 100 shown in Figure 10, the second region A2 is the region at the proximal end of the first region A1. Therefore, the third region A3 and the fourth region A4 included in the second region A2 are also regions at the proximal end of the first region A1. This allows the proximal end of the first region A1 to be stably fixed to the bone.

[0047] Figure 11 shows another example different from those shown in Figures 1 to 3. In the artificial joint stem 100 shown in Figure 11, the second region A2 is the entire first region A1. This allows the proximal portion of the embedded portion 40 to be stably fixed to the bone.

[0048] FIG. 12 is a cross-sectional view taken along line IB-IB in FIG. 1, showing an example different from that of FIG. 5. In FIG. 12, the depth D1a of the first end of groove 1 in the width direction of groove 1 is smaller than the depth D1b of the second end. The cross-sectional shape of groove 1 may be rectangular. In this case, the depth D1a of the first end of groove 1 is equal to the depth D1b of the second end. The cross-sectional shape of groove 1 may be a right triangle. In this case, the depth D1a of the first end of groove 1 is zero.

[0049] As such, the shape of the groove 1 is not particularly limited. For example, the groove 1 may be a circular, polygonal, or irregularly shaped recess. The present disclosure also encompasses an artificial joint stem 100 having such a recess formed therein. The opening area of ​​the recess can be calculated using image analysis software or the like.

[0050] Fig. 13 is a cross-sectional view taken along line IB-IB in Fig. 1, showing an example different from that of Fig. 5. In Fig. 13, in the first region A1, the surface roughness of the inside of groove 1a is smaller than the surface roughness of the outside of groove 1a. As shown in Figs. 5 and 13, the surface roughness of the inside of groove 1 may be different from the surface roughness of the outside of groove 1 for the inside and outside of adjacent grooves 1.

[0051] The material of the substrate 10 can be, for example, metal, ceramic, or plastic. When a metal is used as the material of the substrate 10, the material can be, for example, a stainless steel alloy, a cobalt-chromium alloy, titanium, or a titanium alloy. When a titanium alloy is used as the material of the substrate 10, the material can be, for example, an alloy in which at least one of aluminum, tin, zirconium, molybdenum, nickel, palladium, tantalum, niobium, vanadium, platinum, or the like is added to titanium.

[0052] When ceramics is used as the material of the base 10, the material may be, for example, alumina, zirconia, or alumina-zirconia composite ceramics. When plastic is used as the material of the base 10, the material may be, for example, polyethylene, fluorine-based resin, epoxy resin, polyether ether ketone (PEEK) resin, or Bakelite. In this embodiment, the base 10 is made of a titanium alloy.

[0053] The shape of the base body 10 may be, for example, substantially rod-like, but can be changed as appropriate depending on the shape of the artificial joint to which it is applied.

[0054] 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. At least a portion of the first region A1 may be included in the embedded portion 40. In other words, the second coating 30 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 the desired adhesiveness and antibacterial properties.

[0055] The base 10 as described above may also include a main body 41 having a surface including the first region A1 and the distal region AF, and a neck 51 connected to the proximal end of the main body 41. The main body 41 may be embedded in the femur. The neck 51 is exposed from the femur, and may be provided with a femoral head and installed in an acetabular cup that will be paired with an artificial joint stem.

[0056] The main body 41 has a central axis C extending along the groove 1. The main body 41 also has a proximal end face that is offset from the central axis C, and a neck portion 51 is connected to the proximal end face. The neck portion 51 is narrower than the main body 41 (proximal end face). In other words, the neck portion 51 is a protrusion 51 that protrudes from the main body 41 in an oblique direction inclined from the central axis C.

[0057] The second coating 30 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 of hydroxyapatite, α-tricalcium phosphate, β-tricalcium phosphate, quaternary calcium phosphate, octacalcium phosphate, and calcium phosphate glass. The antibacterial material may be, for example, a natural antibacterial agent, an organic antibacterial agent, or an inorganic antibacterial agent. An example of the natural antibacterial agent is hinokitiol. An example of the organic antibacterial agent is benzalkonium chloride. An example of the inorganic antibacterial agent may be a metal. When a metal is used as the inorganic antibacterial agent, for example, silver, copper, zinc, or the like may be used as the inorganic antibacterial agent.

[0058] In addition to the calcium phosphate-based material and the antibacterial material, the second coating 30 may contain glass ceramics, and may also contain an antibacterial drug such as penicillin or vancomycin.

[0059] The concentration of the antibacterial material in the second coating 30 may be, for example, 0.05% to 3.00% by weight. The concentration of the antibacterial material in the second coating 30 may be, for example, 0.05% to 2.50% by weight. The concentration of the antibacterial material in the second coating 30 may be, for example, 0.05% to 1.00% by weight. The concentration of the antibacterial material in the second coating 30 may be, for example, 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 biological tissue can be reduced.

[0060] A concentration gradient of the antibacterial material may exist in the second coating 30. For example, the concentration of the antibacterial material contained in the proximal end of the second coating 30 may be greater than the concentration of the antibacterial material contained in the distal end of the second coating 30. This can reduce bacterial invasion from the proximal side of the second coating 30. Alternatively, the antibacterial material may be contained only in the proximal end of the second coating 30.

[0061] The second coating 30 may be disposed on the first coating 20. As described above, the first coating 20 may be primarily in contact with the bone. The presence of the second coating 30 on the first coating 20 can further improve adhesion to the bone and antibacterial properties.

[0062] The height of the first coating 20 may be greater than the thickness of the second coating 30. This makes the area where the first coating 20 is formed higher than the area where only the second coating 30 is formed, allowing the area where the first coating 20 is formed to mainly come into contact with the bone. The thickness of the second coating 30 may be, for example, less than 200 μm. The thickness of the second coating 30 may be, for example, less than 100 μm. The thickness of the second coating 30 may be, for example, less than 50 μm. Furthermore, the thickness of the second coating 30 may be, for example, 5 μm or more.

[0063] The second region A2 may be at least partially covered by the second coating 30. That is, the second region A2 may be entirely covered by the second coating 30, or only partially covered by the second coating 30.

[0064] The second coating 30 may be formed to cover the first coating 20. This prevents the first coating 20 from being exposed from the second coating 30. As a result, bacterial growth can be further reduced.

[0065] The distal region AF is exposed from the second coating 30. The portions covered with the second coating 30 and the portions exposed from the second coating 30 can be distinguished by elemental analysis of the surfaces of each region. The elemental analysis can be performed, for example, by mapping surface elements using an energy dispersive X-ray analyzer, which is an accessory to a typical scanning electron microscope. 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 subjected to chemical analysis to identify the elements. For example, phosphorus, calcium, antibacterial components, etc. are detected on at least a portion of the surface of the first region A1 where the second coating 30 is disposed. On the surface of the distal region AF, elements constituting the substrate 10 are detected, while phosphorus, calcium, antibacterial components, etc. are not detected or are below the noise level.

[0066] The surface of the second coating 30 located in the second region A2 may have a smaller surface roughness than the surface of the second coating 30 located in the first region A1 other than the second region A2. This allows sufficient adhesion to the bone and antibacterial properties to be ensured in the first region A1 other than the second region A2. Furthermore, excessive adhesion to the bone can be reduced in the second region A2.

[0067] The surface roughness (Sa) of the second coating 30 located in the first region A1 other than the second region A2 may be, for example, 10 to 80 μm. The surface roughness (Sa) of the second coating 30 located in the first region A1 other than the second region A2 may be, for example, 20 to 80 μm. The surface roughness (Sa) of the second coating 30 located in the first region A1 other than the second region A2 may be, for example, 30 to 70 μm. The surface roughness (Sa) of the second coating 30 located in the second region A2 may be, for example, 0.1 to 10 μm.

[0068] The surface of the second coating 30 located in the second region A2 may have a rougher surface than the surface of the base 10 in the distal region AF. This improves the adhesion between the second coating 30 and the base 10 in the second region A2, thereby ensuring sufficient adhesion to the bone and antibacterial properties. Furthermore, excessive adhesion to the bone in the distal region AF can be reduced.

[0069] Furthermore, the surface roughness of the substrate 10 in the second region A2 may be greater than the surface roughness of the substrate 10 in the distal region AF. This improves adhesion between the second coating 30 and the substrate 10 in the second region A2, thereby reducing peeling of the second coating 30. The surface roughness (Sa) of the substrate 10 in the second region A2 may be, for example, 0.1 μm or more and less than 10 μm. The surface roughness (Sa) of the substrate 10 in the second region A2 may be, for example, less than 2.0 μm.

[0070] At least a portion of the second coating 30 may be disposed in a boundary region 60 that includes the boundary between the buried portion 40 and the exposed portion 50. In other words, the second coating 30 may be disposed in a region of the buried portion 40 that is closer to the exposed portion 50. This can reduce the invasion of bacteria from the exposed portion 50 side.

[0071] The second coating 30 disposed in the boundary region 60 may be disposed only on the buried portion 40. In other words, the second coating 30 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.

[0072] For example, the artificial joint stem 100 may have iodine or a compound containing iodine carried on the entire surface. For example, the artificial joint stem 100 may have iodine or a compound containing iodine carried on a portion thereof. For example, the artificial joint stem 100 may have iodine or a compound containing iodine carried on at least the first region A1. For example, the artificial joint stem 100 may have iodine or a compound containing iodine carried on at least the distal region AF. For example, the artificial joint stem 100 may have iodine or a compound containing iodine carried on only the distal region AF. A known method may be used to carry iodine or a compound containing iodine on the artificial joint stem 100. For example, iodine or a compound containing iodine may be carried on the surface of the artificial joint stem 100 by anodizing treatment.

[0073] 16 is also included in the artificial joint stems according to the present disclosure. For example, the main body 41 may have a distal portion 41a having a central axis C extending along the groove 1, and a proximal portion 41b extending proximally from the distal portion 41a and having a curved shape such that the center moves away from the central axis C as it extends proximally. The proximal portion 41b may have a proximal end face that is offset from the central axis C, and a neck portion 51 may be connected to the proximal end face.

[0074] The artificial joint stem 102 shown in Figure 17 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 side of the coating 20.

[0075] An artificial joint stem 103 shown in Fig. 18 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 in the groove located on the rough surface may be smaller than the surface roughness of the base body 10 located on the rough surface.

[0076] The substrate 10 may have a concavely curved inner portion 13 and a convexly curved outer portion 14. Here, the groove may extend in the vertical direction, and the upper end of the groove may be located in the curved portion. Furthermore, the groove may be bent toward either the inner portion 13 or the outer portion 14 in the contracted portion 40'b. For example, the groove may be bent toward the inner portion 13 in the contracted portion 40'b. Furthermore, the depth of the lower end of the groove may be smaller than the depth of the upper end of the groove. Furthermore, the width of the lower end of the groove may be smaller than the width of the upper end of the groove. Furthermore, a first end of the groove may be exposed from the coating 20, and a second end may be located in the contracted portion 40'b.

[0077] 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 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 first grooves 11 may not be connected to the second grooves 12. That is, the first grooves 11 and the second grooves 12 may be formed as different grooves. The upper end of the first groove 11 may be bent toward the inner portion 13. In other words, the first grooves 11 may have a first portion 11a extending in the vertical direction of the substrate 10 and a second portion 1b 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.

[0078] 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.

[0079] Furthermore, the base 10 may include 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.

[0080] An artificial joint stem 104 shown in Figure 19 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. Figure 20 shows a CC' cross section of Figure 19. As shown in Figure 20, the grooves along the width direction of the base body 10 may become shallower toward the top.

[0081] The edge of the lower end of the coating 20 (first boundary line B1) may intersect with the linear portion of the groove. Here, the first boundary line B1 may intersect with the linear portion of the groove obliquely. In other words, the first boundary line B1 does not have to be perpendicular to the linear portion of the groove.

[0082] Furthermore, the first boundary line B1 may have a first portion B1a extending in a direction intersecting the groove and a second portion B1b extending in a direction along the groove. The second portion B1b may be disposed apart from the groove. That is, the second portion B1b may not be in contact with the groove. The upper edge of the coating 20 (second boundary line B2) may also have a portion extending in a direction intersecting the groove and a portion extending in a direction along the groove.

[0083] The first groove 11 and the second groove 12 may be 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 19, the second boundary line B2 may extend in a direction along the second portion 11b of the first groove 111.

[0084] 19, the second boundary line B2 may be disposed so as to tilt upward from the inner portion 13 toward the outer portion 14. Also, as shown in FIG. 19, the first boundary line B1 may be located below the apex 13a of the recess in the inner portion 13. The second boundary line B2 may be located below the apex 14a of the protrusion in the outer portion 14. Alternatively, the first boundary line B1 may be located above the apex 14a of the protrusion in the outer portion 14.

[0085] The artificial joint stem 105 shown in Figure 21 is also included in the artificial joint stem 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 21, of the angles formed by the first boundary line B1 and the second groove 12, the angle γ on the inner side of the medial portion 13 is an acute angle.

[0086] An artificial joint stem 106 shown in Figure 22 is also included in the artificial joint stem according to the present disclosure. For example, the base body 10 has, from top to bottom, a roughened surface region 70, a non-roughened surface region 80, and a grooved 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 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 with neither a roughened surface nor grooves, and the grooved region 90 may be a region with no roughened surface but with grooves.

[0087] The coating 20 may cover at least one of the roughened surface region 70, the non-roughened surface region 80, and the groove 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 substrate 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. Here, 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.

[0088] The artificial joint stems 100A to 100F shown in Figures 23 to 28 are also included in the artificial joint stems according to the present disclosure. For example, a groove 220A may be provided as in the artificial joint stem 100A. For example, a hole 200B may be provided as in the artificial joint stem 100B. For example, a groove 220C may be provided as in the artificial joint stem 100C. For example, a groove 220D may be provided as in the artificial joint stem 100D. For example, a groove 220E may be provided as in the artificial joint stem 100E. For example, a hole 200F may be provided as in the artificial joint stem 100F. In the above example, an example was described in which exposed regions were provided at the upper and lower ends of the coating 20, but as shown in Figure 19, the exposed region may be located only on the upper side of the coating 20.

[0089] Figure 29 shows another example different from that shown in Figure 16. In the artificial joint stem 101 shown in Figure 16, the second region A2 is a region extending perpendicular to the central axis C extending along the groove 1. In the artificial joint stem 101 shown in Figure 29, the second region A2 is a region extending obliquely to the central axis C extending along the groove 1. In Figure 29 and subsequent figures, the boundary between the second region A2 and the distal region AF is indicated by a dashed line.

[0090] Figure 30 shows another example different from that shown in Figure 16. In the artificial joint stem 101 shown in Figure 30, the second region A2 is a region extending in a direction oblique to the central axis C extending along the groove 1. In addition, the proximal end of the second region A2 is closer to the proximal side than the groove 1a.

[0091] Figure 31 shows another example different from that shown in Figure 16. In the artificial joint stem 101 shown in Figure 31, the distal end of the second region A2 is a region that extends in a diagonal direction with respect to the central axis C that extends along the groove 1.

[0092] 32 is also included in the artificial joint stems according to the present disclosure. For example, the main body 41 may have a distal portion 41a having a central axis C extending along the groove 1, and a proximal portion 41b extending proximally from the distal portion 41a and having a curved shape such that the center moves away from the central axis C as it extends proximally. The proximal portion 41b may have a proximal end face that is offset from the central axis C, and a neck portion 51 may be connected to the proximal end face.

[0093] The proximal portion 41b may have a shape that, on the side opposite to the side where the neck portion 51 is connected, moves away from the central axis C from the distal side to the proximal side and then approaches the central axis C. That is, the proximal portion 41b may have a convex portion 42 on the side opposite to the side where the neck portion 51 is connected. The second region A2 may be distal to the convex portion 42.

[0094] Fig. 33 shows another example different from that shown in Fig. 32. In the artificial joint stem 107 shown in Fig. 33, the proximal end of the second region A2 is located proximally of the convex portion 42.

[0095] Figure 34 shows another example different from that shown in Figure 32. In the artificial joint stem 107 shown in Figure 34, the proximal end of the second region A2 is proximal to the convex portion 42. The distal end of the second region A2 is proximal to the distal end of the second region A2 shown in Figure 32 and distal to the proximal end of the groove 1.

[0096] Figure 35 shows another example different from that shown in Figure 32. In the artificial joint stem 107 shown in Figure 35, the second region A2 is located distally of the protrusion 42. The distal end of the second region A2 is stepped, and the side where the neck portion 51 is connected is more distal than the opposite side.

[0097] Figure 36 shows another example different from that shown in Figure 32. In the artificial joint stem 107 shown in Figure 36, the second region A2 is a region extending in a direction oblique to the central axis C extending along the groove 1. Also, a protrusion 42 exists in the second region A2.

[0098] 2. Method for Manufacturing an Artificial Joint Stem A method for manufacturing an artificial joint stem according to one embodiment includes, for example, a preparation step, a groove forming step, a mirror-finishing step, and a coating forming step. The preparation step involves preparing a base 10 having a surface including a first region and a distal region. The groove forming step involves forming one or more grooves in the surface of the base 10. The mirror-finishing step involves processing the surface of the base 10 to resemble a mirror surface. The coating forming step involves forming a first coating 20 on a portion (first region) of the surface of the base 10. The coating forming step may also be a step of forming a second coating 30 containing a calcium phosphate-based material and an antibacterial material so as to cover the first coating 20.

[0099] In the preparation step, the base 10 can be prepared by forming a metal material into a desired shape using a mold or by additive manufacturing.

[0100] In the groove forming step, the grooves can be formed by at least one of a cutting method, a rolling method, and a press method. 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, for example, a recess forming step may be performed instead of the groove forming step by using the same method as the groove forming step.

[0101] In the mirror-finishing process, the surface of the base 10 can be mirror-finished by at least one of a precision cutting method, a precision grinding method, and a precision polishing method. In this embodiment, the surface of the base 10 is mirror-finished by barrel polishing, which is a type of precision polishing method.

[0102] In the mirror-finishing process, the entire surface of the base 10 may be mirror-finished. In the mirror-finishing process, a region of the surface of the base 10 other than the first region A1 may be mirror-finished. In the mirror-finishing process, only the distal region AF of the surface of the base 10 may be mirror-finished. By mirror-finishing a region of the surface of the base 10 other than the first region A1, the surface roughness of the first region A1 can be made rougher than the surface roughness of the region other than the first region A1. A mirror-finished surface is expected to reduce biofilm formation compared to a surface that is not mirror-finished.

[0103] Alternatively, in the mirror-finishing process, the entire surface of the base 10 does not have to be mirror-finished. In the mirror-finishing process, the distal region AF does not have to be mirror-finished. Also, in the mirror-finishing process, the groove 1 may be mirror-finished. In the mirror-finishing process, only the groove 1 may be mirror-finished without mirror-finishing the entire surface of the base 10. In the mirror-finishing process, an area of ​​the surface of the base 10 other than the groove 1 may be mirror-finished.

[0104] A coating formation process can be performed after the groove formation process and the mirror finish processing process. For example, the first coating 20 can be formed by a thermal spraying method such as flame spraying, arc spraying, shielded arc spraying, high-velocity flame spraying, and plasma spraying. For example, the first coating 20 can be formed by a physical vapor deposition method or a chemical vapor deposition method such as sputtering, ion plating, ion beam deposition, and ion mixing. For example, the first coating 20 can be formed by a wet coating method such as a sol-gel method. In this embodiment, the first coating 20 is formed by flame spraying, which is a type of thermal spraying method. The material constituting the coating is also referred to as a coating material.

[0105] A first protective material may be used to form the first coating 20 only in the first region A1. In this case, the method may further include, before the coating formation step, a step of arranging the first protective material in a position that exposes the first region while protecting the region other than the first region, so that the coating is not formed in the region other than the first region.

[0106] The first protective material may be, for example, masking tape or a partition. Alternatively, the first protective material may be, for example, a jig that covers the base 10. Examples of materials for these first protective materials include metal, glass, resin, and composite materials thereof. The first protective material may be in contact with the base 10, or may not be in contact with the base 10. When, for example, masking tape is used as the first protective material, the first protective material may be placed on an area other than the first area. When, for example, a jig that covers the base 10 is used as the first 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. The cross section of the cylindrical jig may be circular.

[0107] When a partition is provided, the first coating 20 can be formed in a specific region by placing the partition in a predetermined position. When a jig is used, the first coating 20 can be formed in a specific region by placing the jig in a predetermined position.

[0108] In this case, for example, the first coating 20 can be selectively formed only in the desired area by adjusting the positional relationship between the discharge nozzle discharging the thermal spray material, the additive manufacturing material, the chemical etching material, the blasting material, or the 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 area without the partition separating them. Hereinafter, the thermal spray material, the additive manufacturing material, the chemical etching material, the blasting material, or the coating material discharged from the discharge nozzle will also be referred to as the discharged material. Without being limited thereto, the first coating 20 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 varied while the first coating 20 is formed.

[0109] The first coating 20 can also be formed only in a desired area without using a protective material. For example, the coating 20 can be selectively formed only in a desired area by adjusting the shape, angle, position, etc. of the discharge nozzle that discharges the discharge material.

[0110] For example, the discharge material may be discharged with the discharge nozzle 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. By varying the speed, the first coating 20 can be formed with a desired thickness in the desired region. 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.

[0111] A roughening step can also be performed before the coating step. The roughening step is a step of forming a rough surface in the roughened region of the first region A1 of the substrate 10. In the roughening step, the rough surface can be formed by at least one of a thermal spraying method, an additive manufacturing method, a chemical etching method, and a blasting method. Compared to the blasting method, the thermal spraying method, the additive manufacturing method, or the chemical etching method can increase the surface roughness.

[0112] In the thermal spraying method, the material ejected toward the substrate 10 is called the thermal spray material. In the additive manufacturing method, the material ejected toward the substrate 10 is called the additive manufacturing material. Furthermore, when processing is performed by chemical etching, the material ejected toward the substrate 10 is called the chemical etching material. When processing is performed by blasting, the material ejected toward the substrate 10 is called the blasting material. The thermal spraying material can be any of the materials exemplified for the substrate 10. The additive manufacturing material can be any of the materials exemplified for the substrate 10. The first coating 20 described above may be formed by at least one of the thermal spraying method and the additive manufacturing method. Examples of chemical etching methods include alkali treatment, etc. Examples of blasting methods include sandblasting, etc.

[0113] 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 while protecting other regions may be further included before 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 A1 or may be located in the first region A1. In other words, the second protective material may be arranged to protect a portion of the first region A1 or regions other than the first region A1.

[0114] The second protective material may be, for example, masking tape or a partition. Alternatively, the second protective material may be, for example, a jig that covers the base 10. Examples of materials for these second protective materials include metal, glass, resin, and composite materials thereof. The second protective material may be in contact with the base 10 or may not be in contact with the base 10. When, for example, a jig that covers the base 10 is used for 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. The cross section of the cylindrical jig may be circular.

[0115] When a partition is used, a rough surface can be formed in a specific area by placing the partition in a predetermined position.When a jig is used, a rough surface can be formed in a specific area by placing the jig in a predetermined position.

[0116] In this case, for example, by adjusting the positional relationship between the discharge nozzle discharging the thermal spray material, the additive manufacturing material, the chemical etching material, the blasting material, or the 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. Hereinafter, the thermal spray material, the additive manufacturing material, the chemical etching material, the blasting material, or the 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 base 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. The roughened surface may also be formed only in the desired area without using a protective material.

[0117] 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 disposed 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 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 coating formation step.

[0118] Furthermore, after removing the second protective material, a step of scraping the edge of the rough surface, for example, the edge of the first coating 20, may be performed. This makes it possible to avoid stress concentration at the edge of the first coating 20 and reduce irritation to biological tissue.

[0119] The second protective material may be a second masking tape. 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.

[0120] Furthermore, in the coating formation step, a first protective material may be disposed 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 first 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 a first masking tape to the other portion of the substrate 10 while exposing the surface of the substrate 10.

[0121] The second protective material may be made of a material that is more heat-resistant than the first protective material. For example, the second protective material may be made of a material that does not melt or thermally decompose for one minute under thermal spray conditions at 8000°C, and the first protective material may be made of a material that does not melt or thermally decompose for one minute under thermal spray conditions at 3000°C. Specific examples of such materials include composite materials of glass and resin.

[0122] When the surface roughening step is performed by blasting, the second protective material may be made of a material that does not melt or thermally decompose at room temperature. Specific examples of such materials include resins.

[0123] Furthermore, in the step of forming the roughened surface or first 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 first 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 embedded portion 40 and forming the first coating 20 on the exposed region, the first coating 20 can be formed on the region of the exposed portion 50 closer to the embedded portion 40.

[0124] To summarize the above, for example, each step can be performed in the order shown in Figure 14. Figure 14 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, followed by a mirror finishing step. Then, a first protective material can be placed, followed by a coating forming step.

[0125] 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 first coating 20, after the roughening step. The cleaning method is not particularly limited. For example, the cleaning method may be a method of immersing in a liquid such as water or an organic solvent such as alcohol, or showering using such a liquid. Alternatively, the cleaning method may be a method of spraying a gas such as air, nitrogen, or argon. The cleaning step can remove excess spray material and / or shavings generated by the roughening step.

[0126] 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. However, the groove forming step may be followed by a roughening step, and then a coating forming step may be performed.

[0127] 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.

[0128] 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.

[0129] 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 material of the fourth protective material may be a material having lower heat resistance than the third protective material described above. For example, the material of the fourth protective material may be a material that does not melt or thermally decompose at room temperature. Specifically, the material of the fourth protective material may be a resin.

[0130] 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.

[0131] Furthermore, the method for manufacturing the artificial joint stem 100 may first include a step of preparing the base body 10 having the first roughened region, the second roughened region, and the non-roughened region arranged in this order.

[0132] 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.

[0133] 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 15. 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 body 10 of the artificial joint stem 100. The femoral head 110 and the acetabular cup 120 may be formed of a material different from that of the base body 10 of the artificial joint stem 100. 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 ilium 93. The femoral head 110 is fitted and slidably inserted into the recess of the acetabular cup 120, thereby functioning as a hip joint.

[0134] 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.

[0135] REFERENCE SIGNS LIST 1 Groove 10 Base body 20 First coating 21 Thermal spray layer 30 Second coating 40 Embedded portion 41 Main body portion 50 Exposed portion 51 Neck portion 100 Stem for artificial joint 1000 Artificial hip joint

Claims

1. a substrate having a surface; a first coating located in a first region on the surface of the substrate; the first region includes a second region having a portion where the first coating is not located; An artificial joint stem, wherein the second region includes a third region, which is a region in which the first coating is located and a region around which the first coating is not located.

2. 2. The artificial joint stem according to claim 1, wherein in the first region, a thickness of the first coating in a region adjacent to the second region decreases toward the second region.

3. 2. The artificial joint stem according to claim 1, wherein the side of the artificial joint stem that is embedded in the bone when used is defined as the distal side, and the opposite side is defined as the proximal side, and the second region is the region at the proximal end or distal end of the first region.

4. The artificial joint stem according to claim 3 , wherein the second region is a region at a distal end of the first region.

5. 2. The artificial joint stem according to claim 1, wherein the second region includes a fourth region, which is a region where the first coating is not located and is surrounded by the first coating.

6. the substrate has a groove; The artificial joint stem according to claim 1 , wherein the first region where the first coating is disposed includes at least a portion of the groove.

7. 7. The artificial joint stem of claim 6, wherein the thickness of the first coating inside the groove is thicker than the thickness of the first coating outside the groove, for the inside and outside of the groove adjacent to each other in the first region.

8. 7. The artificial joint stem according to claim 6, wherein the thickness of the first coating inside the groove increases with increasing depth of the groove.

9. 7. The artificial joint stem of claim 6, wherein the surface roughness of the first coating inside the groove is greater than the surface roughness of the first coating outside the groove for the inside and outside of the groove adjacent to each other in the first region.

10. 7. The artificial joint stem according to claim 6, wherein the thickness of the first coating inside the groove becomes thinner from the proximal side to the distal side, when the side that is embedded in the bone when the artificial joint stem is used is defined as the distal side and the opposite side is defined as the proximal side.

11. 7. The artificial joint stem of claim 6, wherein in the second region, the ratio of the surface area of ​​the region where the first coating is not located to the surface area inside the groove is smaller than the ratio of the surface area of ​​the region where the first coating is not located to the surface area outside the groove.

12. the substrate has a groove; The artificial joint stem according to claim 1 , wherein the surface roughness of the interior of the groove is different from the surface roughness of the exterior of the groove for the interior and exterior of the groove that are adjacent to each other.

13. 13. The prosthetic stem of claim 12, wherein the surface roughness of the interior of the groove is greater than the surface roughness of the exterior of the groove.

14. 13. The prosthetic stem of claim 12, wherein the surface roughness of the interior of the groove is less than the surface roughness of the exterior of the groove.

15. 13. The artificial joint stem according to claim 12, wherein the surface roughness inside the groove increases in the depth direction of the groove.

16. a second coating located on the first region where the first coating is located; The artificial joint stem of claim 1 , wherein the second coating comprises a calcium phosphate-based material.