Acetabular cup and method for manufacturing the same

Abstract

The present invention provides an acetabular cup that can orient the bone matrix in the bone invasion layer in the direction normal to the outer surface of the cup body. [Solution] An acetabular cup according to one embodiment includes a cup body having a hemispherical outer surface 21 and a bone penetration layer 3 covering the outer surface 21 of the cup body. The bone penetration layer 3 includes a plurality of units 4, each having at least one wall 5 rising from the outer surface 21 of the cup body. A plurality of openings 7 for osteoblast invasion are formed between the units 4, and gaps 8 are formed to connect the openings 7. A plurality of grooves 51 extending in the direction normal to the outer surface 21 of the cup body are formed on both main surfaces 5, 5b of the wall 5.

Description

Technical Field

[0001] The present application relates to an acetabular cup for a total hip arthroplasty and a method for manufacturing the same.

Background Art

[0002] A total hip arthroplasty device is a medical device intended to reconstruct the function of a hip joint affected by diseases such as osteoarthritis of the hip and rheumatoid arthritis, and includes an acetabular cup that is fixed to the acetabular bone. After the total hip arthroplasty device is implanted in the body, there are cases where loosening occurs due to insufficient fixation between the acetabular cup and the acetabular bone, and such cases are cited as one of the main factors for revision surgery to replace the total hip arthroplasty device. Accordingly, it is desirable that the acetabular cup be fixed to the acetabular bone with a high fixation force.

[0003] For example, FIG. 15 of Patent Document 1 discloses an acetabular cup including a base material and a porous portion. The porous portion is formed by laminating two triangular lattice layers.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0005] In the acetabular cup of Patent Document 1, osteoblasts invade the triangular lattice layer from the acetabular bone to produce bone matrix, and the bone matrix interlocks the acetabular bone and the porous portion, so that a high fixation force to the acetabular bone is obtained.

[0006] Meanwhile, in the bone invasion layer of the acetabular cup (the porous portion in Patent Document 1), there is a demand for orienting the bone matrix produced in the bone invasion layer in the normal direction of the outer surface of the cup main body.

[0007] Therefore, the present application aims to provide an acetabular cup capable of orienting the bone matrix in the bone penetration layer in the direction normal to the outer surface of the cup body, and a method for manufacturing the same. [Means for solving the problem]

[0008] This application provides an acetabular cup comprising, from one side, a cup body having a hemispherical outer surface, and a bone penetration layer covering the outer surface of the cup body, wherein the bone penetration layer includes a plurality of units, each having at least one wall rising from the outer surface of the cup body, a plurality of openings for the invasion of osteoblasts formed between the plurality of units and gaps that connect the plurality of openings, and a plurality of grooves extending in the direction normal to the outer surface of the cup body formed on both main surfaces of the at least one wall.

[0009] This application also provides, from another perspective, a method for manufacturing an acetabular cup using additive manufacturing. [Effects of the Invention]

[0010] This application provides an acetabular cup capable of orienting the bone matrix in the bone penetration layer in the direction normal to the outer surface of the cup body, and a method for manufacturing the same. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view of an acetabular cup according to one embodiment. [Figure 2] This is a magnified view of the surface of the bone invasion layer. [Figure 3] This is a cross-sectional view along line III-III in Figure 2. [Figure 4] This is a magnified view of the surface of the bone invasion layer in the first modified example. [Figure 5] This is a cross-sectional view along the VV line in Figure 4. [Figure 6] This is a perspective view of the acetabular cup with a changed arrangement of units. [Figure 7]This is a magnified view of the surface of the bone invasion layer in the second modified example. [Figure 8] This is a magnified view of the surface of the bone invasion layer in the third modified example. [Figure 9] This is a magnified view of the surface of the bone invasion layer in the fourth modified example. [Modes for carrying out the invention]

[0012] Figure 1 shows an acetabular cup 1 according to one embodiment. This acetabular cup 1, together with a femoral stem inserted into the femur and a liner fitted inside the acetabular cup 1 and sliding against the femoral head of the femoral stem, constitutes an artificial hip joint.

[0013] The acetabular cup 1 has a central hole 11 at its top for fitting with a portion of the liner. The acetabular cup 1 also has multiple insertion holes 12 (only one is shown in Figure 1) for screws to fix the acetabular cup 1 to the acetabular bone.

[0014] Specifically, the acetabular cup 1 includes a cup body 2 having a hemispherical outer surface 21 (see Figure 3) and a bone penetration layer 3 that completely covers the outer surface 21. In Figure 1, for the sake of simplicity, the bone penetration layer 3 is represented by a mesh corresponding to the shape of the opening 7, which will be described later. In this embodiment, as shown in Figure 1, a projection 22 is provided on the periphery of the cup body 2, protruding from the outer surface 21 to a height approximately the same as the thickness of the bone penetration layer 3.

[0015] The bone invasion layer 3, as shown in Figure 2, includes a plurality of units 4 arranged along the entire outer surface 21 of the cup body 2. All units 4 are the same shape. Between the units 4, a plurality of openings 7 for osteoblast invasion are formed, and gaps 8 are formed that connect the openings 7.

[0016] As shown in Figure 3, each unit 4 has at least one wall 5 rising from the outer surface 21 of the cup body 2. In the present embodiment, each unit 4 has a support post 6 rising from the outer surface 21 of the cup body 2, and three walls 5 extending radially outward from the support post 6 at equal angular intervals.

[0017] The opening 7 is a space with a triangular cross-section surrounded by one wall 5 of three units 4 among all the units 4, and the gap 8 is formed between the support post 6 of one unit 4 among all the units 4 and the end face 5c of the wall 5 of another unit 4.

[0018] With such a configuration, the hemispherical layer along the outer surface 21 of the cup body 2 can be divided into triangular regions corresponding to a icositetrahedron, and each of these triangular regions can be divided into a plurality of openings 7.

[0019] More specifically, in each of the aforementioned triangular regions, the units 4 are arranged in such a pattern that unit rows, in which the units 4 are arranged at a predetermined pitch in the longitudinal direction (the circumferential direction of the cup body 2, which is the left-right direction in Figure 2), are arranged in the latitudinal direction while being offset by half of the predetermined pitch. The longitudinal direction is a direction parallel to the latitude lines connecting equal latitudes, and the latitudinal direction is a direction parallel to the longitude lines connecting equal longitudes. In each unit row, one of the three walls 5 of the unit 4 is positioned on the same straight line extending in the longitudinal direction. Therefore, the units 4 can be arranged in the same orientation in each of the aforementioned triangular regions.

[0020] When each opening 7 is viewed from the normal direction of the outer surface of the cup body 2, the diameter of the inscribed circle 9 inscribed in the walls 5 of the three units 4 located around the opening 7 is preferably greater than 500 μm and 2000 μm or less. If the diameter of the inscribed circle 9 is greater than 500 μm and 2000 μm or less, osteoblasts can effectively invade into the opening 7. More preferably, the diameter of the inscribed circle 9 is 600 μm or more and 1500 μm or less.

[0021] In each unit 4, multiple grooves 51 are formed on both main surfaces 5a and 5b of each wall 5, extending in the direction normal to the outer surface 21 of the cup body 2. In this embodiment, there are two grooves 51 on each of the main surfaces 5a and 5b, but there may be three or more grooves 51.

[0022] Furthermore, in this embodiment, the grooves 51 on the main surface 5a and the grooves 51 on the main surface 5b are in the same position on each wall 5, but the position of the grooves 51 is not limited to this. For example, the grooves 51 on the main surface 5a and the grooves 51 on the main surface 5b may be arranged alternately.

[0023] Furthermore, in this embodiment, in each unit 4, multiple grooves 61 are formed in the support column 6 between the three walls 5, extending in the direction normal to the outer surface 21 of the cup body 2. There are a total of three grooves 61, one between each adjacent wall 5.

[0024] For example, the depth of grooves 51 and 61 is between 1 μm and 500 μm, and the width of grooves 51 and 61 is between 2 μm and 500 μm.

[0025] Such an acetabular cup 1 can be manufactured using additive manufacturing methods such as 3D printing. Examples of powder materials used in 3D printing include metals, ceramics, bioglass, and polymers.

[0026] In the acetabular cup 1 with the configuration described above, when the bone invasion layer 3 is fixed in contact with the acetabular bone, osteoblasts invade each opening 7 from the acetabular bone. Moreover, since the openings 7 are connected to each other through the gaps 8 between the units 4, the bodily fluids present in each opening 7 flow through the gaps 8 between the units 4 simultaneously with the invasion of osteoblasts into each opening 7. As a result, osteoblasts can invade deep into the openings 7, that is, up to the outer surface 21 of the cup body 2.

[0027] Furthermore, since grooves 51 extending in the direction normal to the outer surface 21 of the cup body 2 are formed in the wall 5 included in unit 4, bone matrix oriented in the direction normal to the outer surface 21 of the cup body 2 is produced within each opening 7. Therefore, the bone matrix can be oriented in the direction normal to the outer surface 21 of the cup body 2 in the bone penetration layer 3.

[0028] <Variation> The present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0029] For example, grooves 61 do not need to be formed in the support columns 6 of each unit 4. However, if grooves 61 are formed in the support columns 6 of each unit 4 as in the embodiment described above, the grooves 61 formed in the support columns 6 can orient the bone matrix in the direction normal to the outer surface 21 of the cup body 2, even in the portion adjacent to the support column 6.

[0030] Furthermore, as shown in Figures 4 and 5, adjacent units 4 in the bone penetration layer 3 may be connected to each other by a bridge 31. The bridge 31 is a plate-like structure with a width similar to that of the wall 5, forming a continuous surface with the top surface of the wall 5, and covering the gap 8 described above. In other words, a gap 8 exists between the bridge 31 and the outer surface 21 of the cup body 2. Also, grooves 32 similar in size to the grooves 51 provided in the wall 5 may be formed on both sides of the bridge 31.

[0031] Furthermore, the arrangement pattern of unit 4 shown in Figure 6 can also be adopted. In Figure 6, the bone income layer 3 is divided into multiple regions aligned circumferentially by multiple longitude lines at equal angular intervals, and in each region, rows of units 4 are arranged in the latitudinal direction at a predetermined pitch, with each row being offset by half of the predetermined pitch in the latitudinal direction. In each row of units, one of the three walls 5 of unit 4 is located on the same straight line extending in the latitudinal direction.

[0032] Furthermore, the shape of the units included in the bone penetration layer 3 and the corresponding arrangement pattern can be changed as appropriate. For example, as shown in Figure 7, the bone penetration layer 3 may be composed of units 4A, each consisting of a single wall 5A, arranged in a matrix while rotating 90 degrees. In this case, the opening 7 is a square-shaped space in cross-section surrounded by the walls 5 of the four units 4 in the mth and m+1th columns of the nth row, and the mth and m+1th columns of the n+1th row.

[0033] In Figure 7, the diameter of the inscribed circle 91 that is inscribed in the walls 5 of the four units 4 located around each opening 7 is preferably greater than 500 μm and 2000 μm or less, and more preferably 600 μm or more and 1500 μm or less, as in the above embodiment. Furthermore, a gap 8 is formed between the end faces 5c, 5d of the wall 5 of one unit 4 and the main faces 5a, 5b of the walls 5 of the units 4 located on both sides in the extending direction of the unit 4.

[0034] Alternatively, configurations such as those shown in Figures 8 and 9 can also be adopted. In Figure 8, a group of units consisting of three units 4A arranged on the sides of an equilateral triangle are arranged in the latitudinal direction at a predetermined pitch, and these groups are arranged in the longitudinal direction with a shift of half the predetermined pitch. In this case, the opening 7 is a hexagonal space in cross-section surrounded by the wall 5 of the six units 4A, indicated by the inscribed circle 92, and a triangular space in cross-section surrounded by the wall 5 of the three units 4A, indicated by the inscribed surface 93.

[0035] In Figure 9, a group of units consisting of six spirally arranged units 4A is lined up in the latitudinal direction at a predetermined pitch, and then lined up in the longitudinal direction with a shift of half the predetermined pitch. The opening 7 in this case is a space with a star-shaped cross-section enclosed by the walls 5 of the six units 4A, indicated by the inscribed circle 94, and a space with a roughly trapezoidal cross-section enclosed by the walls 5 of the three units 4A, indicated by the inscribed surface 95.

[0036] <Summary> In a first aspect, the present application provides an acetabular cup comprising, from one side, a cup body having a hemispherical outer surface, and a bone penetration layer covering the outer surface of the cup body, wherein the bone penetration layer includes a plurality of units, each having at least one wall rising from the outer surface of the cup body, a plurality of openings for the invasion of osteoblasts formed between the plurality of units and gaps that connect the plurality of openings, and a plurality of grooves extending in the direction normal to the outer surface of the cup body formed on both main surfaces of the at least one wall.

[0037] With the above configuration, when the bone invasion layer is fixed in contact with the acetabulum, osteoblasts invade each opening from the acetabulum. Moreover, since the openings are connected through the gaps between the units, the body fluid present in each opening flows through the gaps between the units simultaneously with the invasion of osteoblasts into each opening. As a result, osteoblasts can invade deep into the openings, that is, to the outer surface of the cup body.

[0038] Furthermore, since grooves extending in the direction normal to the outer surface of the cup body are formed in the walls of the unit, bone matrix oriented in the direction normal to the outer surface of the cup body is produced within each opening. Therefore, the bone matrix can be oriented in the direction normal to the outer surface of the cup body in the bone penetration layer.

[0039] In a second embodiment, in the first embodiment, when each of the plurality of openings is viewed from the direction normal to the outer surface of the cup body, the diameter of the inscribed circle that is inscribed in the wall of the unit located around the opening may be greater than 500 μm and less than or equal to 2000 μm. With this configuration, osteoblasts can be effectively invaded into the openings.

[0040] In a third embodiment, in the first or second embodiment, each of the plurality of units has a support column rising from the outer surface of the cup body and three walls, which constitute at least one wall, extending radially outward from the support column at equal angular intervals, and each of the plurality of openings is a space with a triangular cross-section enclosed by one wall of three of the plurality of units, and the gap may be formed between the support column of one of the plurality of units and the end face of the wall of another unit. With this configuration, the hemispherical layer along the outer surface of the cup body can be divided into triangular regions corresponding to an icosquatahedron, and each of these triangular regions can be divided into a plurality of openings.

[0041] In a fourth embodiment, in the third embodiment, the plurality of units may be arranged in a pattern in which rows of units are arranged at a predetermined pitch such that one of the three walls is located on the same straight line, with each row of units offset by half the predetermined pitch. With this configuration, the units can be arranged in the same orientation in each of the aforementioned triangular regions.

[0042] In a fifth embodiment, in the third or fourth embodiment, the support column may have a plurality of grooves formed between the three walls, extending in the direction normal to the outer surface of the cup body. With this configuration, even in portions adjacent to the support column, the grooves formed in the support column can orient the bone matrix in the direction normal to the outer surface of the cup body.

[0043] In a sixth aspect, the present application provides a method for manufacturing acetabular cups according to the first to fifth aspects, which is produced by additive manufacturing. [Explanation of symbols]

[0044] 1. Acetabular cup 2 cups 21 External surface 3 Bone invasion layer 4.4A Unit 5 walls 5a,5b Main surface 5c,5d end face 51 Groove 6 pillars 61 Groove 7 aperture 8 gaps 9, 91, 92, 93, 94, 95 Inscribed circle

Claims

1. A cup body having a hemispherical outer surface, The cup body comprises a bone penetration layer covering the outer surface, The bone penetration layer comprises a plurality of units, each having at least one wall rising from the outer surface of the cup body, and a plurality of openings for the invasion of osteoblasts are formed between the plurality of units, and gaps are formed that connect the plurality of openings. Acetabular cup, wherein a plurality of grooves extending in the direction normal to the outer surface of the cup body are formed on both main surfaces of at least one wall.

2. The acetabular cup according to claim 1, wherein when each of the plurality of openings is viewed from the direction normal to the outer surface of the cup body, the diameter of the inscribed circle that is inscribed in the wall of the unit located around the opening is greater than 500 μm and less than or equal to 2000 μm.

3. Each of the aforementioned plurality of units has a support column rising from the outer surface of the cup body, and three walls, which constitute the at least one wall, extending radially outward from the support column at equal angular intervals. Each of the aforementioned multiple openings is a space with a triangular cross-section enclosed by one wall of three of the aforementioned multiple units. The acetabular cup according to claim 1 or 2, wherein the gap is formed between the support column of one of the plurality of units and the end face of the wall of another unit.

4. The acetabular cup according to claim 3, wherein the plurality of units are arranged in a pattern in which rows of units are arranged at a predetermined pitch such that one of the three walls is located on the same straight line, and these rows are offset by half the predetermined pitch.

5. The acetabular cup according to claim 3, wherein the support column has a plurality of grooves formed between the three walls, extending in the direction normal to the outer surface of the cup body.

6. A method for manufacturing an acetabular cup, wherein the acetabular cup described in claim 1 or 2 is manufactured by additive manufacturing.

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