JP2011169852A - Device and method for testing wear of artificial joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a device with which wear test of an artificial joint can be performed in operation conditions specific to each portion of a human body using an NC lathe or a machining center; and to propose a method for testing wear of the artificial joint using the device. <P>SOLUTION: The device includes a work shaft side holder attached to the work shaft of a machine tool and a tool shaft side holder attached to a tool shaft. The work shaft holder includes: a table for fixing a sample or a test tray; a guide for guiding the table in the direction along the axis of the work shaft or in the direction perpendicular to the axis when a fixing part is fixed to the work shaft; a height adjuster and a position adjuster which adjusts the position in the direction perpendicular to both the direction and the axis of the work shaft, in order to maintain the spherical center of the sample fixed to the table on the axis of the work shaft; and a sensor which detects force in the straight line direction acting on the table. The tool shaft side holder includes a shaft for attachment to the tool shaft and a receiving stand for fixing the sample or the test tray. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wear test apparatus used for an artificial joint wear resistance test and a wear test method for an artificial joint using the apparatus.

  The artificial joint is attached to the human body by surgery. If the attached artificial joint is worn away and cannot be used, it must be replaced, and re-operation is necessary for replacement. In order to be able to use the artificial joint as long as possible without performing another operation, the artificial joint is required to have high wear resistance. As a wear test apparatus for biomaterials such as artificial joint materials, an apparatus described in Patent Document 1 has been proposed. A wear test device dedicated to artificial joints is also provided.

JP-A-11-51838

  In order to improve the wear resistance of the artificial joint, it is important to improve the wear resistance of the material. However, the artificial joint has a sliding range of the artificial joint and a direction of a force acting on the artificial joint depending on a part of the human body to which the artificial joint is attached (for example, a hip joint or a knee joint) and a motion mode of the human body. Therefore, it is considered that the artificial joint attached to the human body is subject to partial wear in a different manner depending on the part, movement habit, and the like.

  If you know how the wear occurs, apply a surface treatment that partially increases the wear resistance of the artificial bone surface, adopt a shape that promotes the flow of joint fluid to the worn part, or reduce the wear allowance. The durability of the artificial joint can be further improved by including the shape or improving the material. That is, in order to test the wear of the artificial joint in more detail, a test apparatus that can simulate the movement and force specific to the joint part is required. As such a test apparatus, a wear test apparatus dedicated to an artificial joint is provided. However, this dedicated wear test device is very expensive.

  The present invention provides a device that can perform a wear resistance test of an artificial joint under operating conditions peculiar to each part of a human body using a machine that is relatively widespread, and uses the device to We propose a method for performing an abrasion resistance test.

  The artificial joint wear test apparatus according to the present invention includes a work shaft side holder 1 mounted on a work shaft A of a machine tool and a tool shaft side holder 3 mounted on a tool axis B of the machine tool. The workpiece axis A is a member such as a spindle or a table on which a workpiece to be processed is mounted, and a rotation angle and a rotation speed around the axis are controlled by an NC apparatus. The tool axis B is a member such as a tool spindle or a tool post on which a tool to be processed is mounted, and its position and necessary direction are controlled by an NC device. The rotary tool axis is further an NC device. Therefore, the rotation angle and rotation speed around the axis are controlled. The workpiece shaft side holder 1 includes a mounting portion 11 that is fixed to the workpiece shaft A and a table 15 that fixes the sample 6.

  The workpiece shaft side holder of the artificial joint wear test apparatus according to claim 1 of the present application is such that the table 15 is linearly orthogonal to the axis of the workpiece axis A, that is, the rotation center axis when the mounting portion 11 is fixed to the workpiece axis A. Height adjustment for adjusting the position of the table 15 in the linear direction so that the center of the sphere 61 of the sample 6 fixed to the table 15 and the sphere 61 of the sample 6 fixed to the table 15 can be held on the axis of the workpiece axis A. A tool 17 and a position adjusting tool 22 that adjusts the position in a direction perpendicular to both the linear direction and the axis of the workpiece axis A; and a sensor 16 that detects the linear force acting on the table 15. Yes. Further, the tool shaft side holder 3 of the wear test apparatus according to claim 1 includes a shaft 31 to be mounted on the tool shaft B and a cradle 32 for fixing the test dish 8. In the wear test, both the sample 6 and the test dish 8 are usually made of an artificial joint material, and both are tested for wear.

  The work shaft side holder 1 of the artificial joint wear test apparatus according to claim 2 of the present application includes an attachment portion 11 fixed to the work shaft A, a table 15 for fixing the test dish 8, and an attachment portion 11. A guide 13 for guiding the table 15 along the axial direction of the workpiece axis A (the Z-axis direction in the lathe) when fixed to the workpiece axis A, and a sensor for detecting the axial force of the workpiece axis acting on the table 15 16, the tool shaft side holder 3 includes a shaft 31 to be mounted on the tool shaft B and a cradle 32 for fixing the sample 6.

  Since the wear test of the artificial joint is performed in a state where the sample 6 and the test dish 8 are immersed in the artificial joint fluid, the wear test apparatus according to the present invention generally has a liquid container 4 containing the artificial joint fluid. is necessary. The liquid container 4 is preferably provided by being mounted on the work shaft side holder 1. In a tool shaft side holder provided with a cradle 32 at the tip of a shaft to be mounted on the tool shaft, the shaft side surface 33 of the cradle 32 is provided. Is a partial spherical surface, the sealing lid 43 of the liquid container 4 is provided with a circular opening 45 and a liquid sealing packing 46 for liquid sealing the gap between the circular opening and the partial spherical surface, and the sample sphere 61 and the test dish 8 are sealed. The liquid container can be relatively swung within the liquid container.

  The wear test of the artificial joint according to the invention of claim 4 of this application is performed by mounting the wear test apparatus of claim 1 on an NC machine tool having a rotary work shaft and a rotary tool shaft capable of controlling the rotation angle. . That is, the workpiece axis holder 1 is attached to the workpiece axis A of the machine tool, and the tool axis side holder 3 is attached to the tool axis B. A ball-side sample 6 of an artificial joint is fixed to the work shaft side holder 1, and a test dish 8 is fixed to the tool shaft side holder B. Then, the NC device of the machine tool has an operation of reciprocatingly swinging in the first angle range in which the workpiece axis A is designated, an operation of reciprocatingly swinging in the second angle range in which the tool axis B is designated, and the tool axis B. A machining program that repeats the operation of reciprocating the lathe in the X-axis direction at the same cycle is registered, and the machine tool is operated according to the machining program, thereby performing an artificial joint wear test.

  The wear test of the artificial joint according to the invention of claim 5 of this application includes a rotating work shaft capable of controlling the rotation angle of the wear test apparatus of claim 2 and a swing angle about an axis corresponding to the B axis in the lathe. This is done by mounting it on an NC machine tool with a controllable, rotating or non-rotating tool axis B. That is, the workpiece axis holder 1 is attached to the workpiece axis A of the machine tool, and the tool axis side holder 3 is attached to the tool axis B. An artificial joint test dish 8 is fixed to the work shaft side holder 1, and a ball side sample 6 is fixed to the tool shaft side holder 3. Then, the NC device of the machine tool swings back and forth within a first angle range in which the workpiece axis A is designated, and an axis equivalent to the B axis in the lathe in the second angle range in which the tool axis B is designated. The tool axis B corresponds to the Z-axis direction and the X-axis direction of the lathe so that the center of the test dish 8 and the sample sphere 61 are held at the same position in synchronization with the reciprocal swing. Registering a machining program that repeats the operation of moving the tool axis B in both directions and reciprocating the tool axis B in the direction corresponding to the Z-axis direction of the lathe with the same period, and operating the machine tool with the machining program The wear test of the artificial joint is performed.

  For example, a lathe or a machining center can be used as the machine tool. The rotary work axis is a main axis in a lathe, and a work table in a machining center, and the axis of the work axis is a center axis of these rotations.

  The artificial joint wear test method of the present invention uses an existing NC machine tool as it is, or an existing machine tool in which a spindle motor or a tool motor is replaced with a motor capable of swinging within an angular range specified by a machining program. The wear test device of the present invention is mounted on the rotating work shaft and the rotating tool shaft, and the rocking motion according to the part of the human body on which the artificial joint to be tested is mounted according to the machining program of the NC device of the machine tool and A wear test is performed by applying force.

  According to the wear test method of the present invention, it is possible to perform a wear test by simulating a repetitive motion peculiar to the part of the human body to which the artificial joint is to be worn. Of course, the wear characteristics of the material itself can be applied to each joint part. It is possible to examine in detail how the inherent wear occurs.

  Therefore, the existing NC machine tools that have been widely spread are used as they are, or some modifications are made to existing NC machine tools, and the NC machine tools are equipped with the wear test apparatus of the present invention to prepare a desired machining program. Thus, there is an effect that a detailed wear resistance test of the artificial joint can be performed at a low cost.

The perspective view which shows 1st Example of the abrasion test apparatus of this invention Sectional view of the workpiece axis side holder with the sample mounted in the direction perpendicular to the Z axis Side view of workpiece axis holder Bottom view of workpiece axis holder Schematic diagram showing the wear test device mounted on a lathe with the spindle origin phase The side view which shows 2nd Example of the abrasion test apparatus of this invention

  Hereinafter, description will be made based on the drawings showing an example in which a lathe is used as a machine tool. 1 to 4 are diagrams showing an artificial joint wear test apparatus according to the present invention. In the figure, 1 is a workpiece shaft side holder, and 3 is a tool shaft side holder. The work shaft side holder 1 includes a holder base 12 having a mounting portion 11 fixed to a lathe spindle A, a table 15 supported by the holder base via a linear guide 13, a holder base 12 and a table 15; The load cell 16 and the height adjusting screw 17 interposed therebetween, and the position adjusting screws 22 and 23 attached to the table 15 are provided. A sample 6 to be subjected to the wear test is fixed on a table 15 via a sample holder 5 provided with a liquid container 4. The tool shaft side holder 3 includes a pedestal 32 that is integrally provided with a shaft 31 that is inserted into the rotary tool shaft B of the lathe.

  The holder base 12 of the workpiece shaft side holder has an L shape in a side view. Reference numeral 18 denotes a reinforcing plate. An attachment portion 11 for attaching the holder base 12 to the spindle A of the lathe is provided at the upper end of the wall plate 19 of the holder base 12. The mounting portion 11 is provided with a fitting portion (not shown) for aligning the axis of the main shaft and the shaft center of the mounting portion 11 and a bolt hole 20 for a fixing bolt. A load cell that measures a load in a direction perpendicular to the center line of the attachment portion 11 (a line that coincides with the spindle axis when attached to the spindle of the lathe) is provided on the floor plate 21 of the holder base 12 via the height adjusting screw 17. 16 is attached.

  Further, three linear guides 13 are mounted on the holder base floor plate 21 with the load cell 16 as the center and parallel to the load measuring direction of the load cell 16. A table 15 for fixing the sample 6 to be subjected to the wear test is fixed to the slide rods 14 of the three linear guides 13 and can be moved in parallel with the load measuring direction of the load cell 16. The height adjustment screw 17 is an adjustment tool that adjusts the distance between the table 15 and the center line of the attachment portion 11.

  The sample 6 for wear test is formed by integrally forming a sphere 61 serving as a bone head at the tip of the housing 62 and is fixed to the table 15 via the sample holder 5. The sample holder 5 includes a pedestal 51 fixed on the table 15 and a sample chuck (collet-type chuck) 52 attached to the upper surface thereof. The sample 6 is held by the sample chuck 52 with the casing 62 in a direction perpendicular to the surface of the table 15. The pedestal 51 is square, and has bolt insertion holes at four corners. On the upper surface of the table 15, position adjusting screws 22 and 23 for pressing the four sides of the pedestal 51 from four directions (from both the X-axis direction and the Z-axis direction of the lathe) are provided. The sample holder 5 placed on the table 15 is adjusted in position in the X-axis direction and the Y-axis direction by the position adjusting screws 22 and 23 and then fixed to the table 15 by the fixing screw 54. 55 is a wedge for removing the sample, and 56 is a screw for pushing the wedge when the sample is removed.

  The tool shaft side holder 3 is attached to the rotary tool shaft B of the lathe via the extension shaft 7. The extension shaft 7 includes a shank inserted into the shaft end of the rotary tool shaft B of the lathe on the proximal end side, and a collet chuck that fixes the shaft 31 of the tool shaft side holder on the distal end side. The tool shaft side holder 3 includes a pedestal 32 having a back surface 33 on the shaft 31 side as a partial spherical surface and a non-shaft side as a receiving surface 34 orthogonal to the axis of the shaft 31 (therefore, the axis of the rotating tool axis of the lathe). ing. The test dish 8 to be subjected to the wear test is mounted with its pedestal 81 fixed to the receiving surface 34 with a screw 35. The back surface 33 of the cradle is a partial spherical surface centered on the center of the sphere 61 in a wear test state where the test plate 8 and the sphere 61 of the sample are in surface contact.

  The dish of the test dish 8 shown in the figure (the concave part in surface contact with the sphere 61) is that the bed surface (ZX plane) of the NC lathe used in the example is inclined 60 degrees with respect to the horizontal plane, and the femur In consideration of the shape of the concave portion of the pelvis that receives the bone head of the pedestal 81, the pedestal 81 is formed on a surface inclined with respect to the mounting plane.

  The joint moves within the synovial fluid. Therefore, it is necessary to perform the wear test of the artificial joint in a state where the artificial joint is immersed in a liquid (artificial joint fluid) having properties equivalent to the joint fluid. The liquid container which encloses this liquid is shown by FIGS.

  The liquid container 4 is attached with the bottom surface of the container body 41 fixed to the sample holder 5, and is liquid-sealed by an O-ring 42 interposed between the cylindrical part of the sample holder 5. A sealing lid 43 is attached to the upper surface of the container main body 41. The sealing lid 43 includes an inclined surface 44, and the upper surface of the container main body 41 includes a receiving base 32 for inserting the tool base holder 32. A small-diameter circular opening 45 is provided. A liquid seal packing 46 is attached to the peripheral edge of the circular opening 45. Nipples 47 and 48 for connecting pipes for circulating artificial joint fluid in the liquid container 4 are attached to the container main body 41 at the upper side and the lower side.

  The tool shaft side holder 3 is fitted on the shaft end of the extension shaft 7 mounted on the rotary tool shaft of the lathe after the shaft 31 is inserted into the circular opening 45 of the sealing lid. After that, the sealing lid 43 is fixed to the container body 41 in a state where the test plate 8 is brought into contact with the sphere 61 of the sample by the movement of the tool rest on which the rotary tool shaft is mounted in the Z direction and the X direction. In this state, a gap between the circular opening 45 of the sealing lid and the back surface 33 of the receiving base of the tool shaft side holder is sealed by the liquid seal packing 46. Since the back surface 33 of the cradle is a partial spherical surface centered on the center of the sphere 61, the sample sphere 61 and the test dish 8 perform relative swinging motion in the liquid container 4 about the center of the sphere 61. And the sealed state of the liquid container 4 is also maintained.

  Next, a test method for an artificial joint using the friction test apparatus having the above structure will be described. The lathe used for the test is a lathe capable of swinging the main axis A and the rotary tool axis B within the angle range set by the machining program by NC (numerical control). Lathes that can oscillate the main shaft in the specified angle range are common, but lathes that can oscillate the rotary tool axis in the specified angle range are not common, so in some cases a tool axis motor Needs to be replaced with a motor having such a function.

  The artificial bone sample 6 to be used for the test is fixed to the work shaft side holder 1 through the sample holder 5, and the test dish 8 is fixed to the tool shaft side holder 3. The work shaft side holder 1 has its mounting portion 11 fixed to the spindle end of the lathe, and the center of the sample sphere 61 coincides with the spindle axis of the lathe by the position adjusting screw 22 and the height adjusting screw 17 in the X-axis direction. Let The tool shaft side holder 3 is attached to the rotating tool shaft of the lathe via the extension shaft 7, adjusts the position of the tool post to which the rotating tool shaft is attached in the Z-axis direction, and sets the center of the rotating tool shaft as a sample. To the center of the sphere 61 of

  Next, the tool post is moved in the X-axis direction to set the sample 6 and the test dish 8 in a predetermined positional relationship. At this time, the sphere 61 of the sample 6 and the test dish 8 are in surface contact with each other leaving a gap in which a synovial fluid film is formed. In this state, the sealing lid 43 of the liquid container is fixed to the container body 41. Then, the artificial joint fluid is circulated through the nipples 47 and 48 into the fluid container 4 by a joint fluid circulation device (not shown).

  In this state, the lathe spindle and the rotary tool axis are swung synchronously within the angle range specified by the program of the NC device that controls the lathe, and in synchronism with this swing, the X-axis feed motor of the tool post is synchronized with the joint plate. A wear test is performed by giving a minute feed command corresponding to a periodic load change acting between the sphere and the spherical surface.

  An example of the case of an artificial hip joint will be described. The main shaft is reciprocally swung in an angle range divided by 25 degrees and 18 degrees on both sides of the origin phase where the casing 62 of the sample is in the vertical direction. A load in which the load detected by the load cell 16 acts on the hip joint during walking in synchronism with the reciprocating oscillation of the rotary tool axis in an angular range of 10 degrees and 2 degrees with respect to the Z axis. The X-axis position of the tool post on which the rotary tool axis is mounted is slightly moved so as to change with a fluctuation pattern that imitates the fluctuation pattern. This angle range and load change simulate the hip joint operation angle range and load change during walking. The sample 6 and the test dish 8 are both made of a material used as an artificial bone.

  In the first embodiment described above, the sample 6 having a sphere serving as a bone head is attached to the main shaft side, and the test dish 8 is attached to the rotary tool shaft. However, it can be reversed. In this case, as illustrated in FIG. 6, the test plate 8 is fixed to the table 15 of the work shaft side holder 1 attached to the main spindle of the lathe by the attaching portion 11, and the sample is placed in the tool shaft side holder 3 attached to the tool shaft. 6 is fixed. The tool shaft side holder 3 has a structure similar to that of the extension shaft 7 of the first embodiment, that is, a shank fitted to the rotating tool shaft at the base end, and a collet chuck for gripping the sample housing 62 at the tip end. Structure. The work shaft side holder table 15 is guided by the linear guide 13 in the direction of the main shaft axis, and is fixed to the holder base 12 via the load cell 16. A member corresponding to the height adjusting screw 17 of the first embodiment is not provided.

  In the wear test apparatus of the second embodiment, the rotary tool shaft is mounted on a lathe capable of swinging around the B axis in addition to the X and Y axes of the lathe. Since the test is performed in a state where the rotary tool axis is stopped, swinging around the axis of the rotary tool axis is unnecessary. In the case of the above-described artificial hip joint, in the second embodiment, the rotary tool shaft is reciprocally swung around the B axis in an angle range of 43 degrees, and the rotary tool shaft is moved in synchronism with this reciprocating swing. The positional relationship in which the center of the sphere 61 of the sample 6 and the center of the test dish 8 coincide with each other by the Z and X axis movements of the mounted tool post is maintained, and the spindle is rotated in synchronism with the reciprocating oscillation of the rotary tool axis. Rotating so that the load detected by the load cell 16 changes in a variation pattern simulating the variation pattern of the load acting on the hip joint during walking in synchronism with the reciprocal oscillation in an angle range of 12 degrees. The X-axis position of the tool post on which the tool axis is mounted is slightly moved.

  As described above, according to the test method of the present invention, the wear test can be performed by changing the movement of the human body and the load acting during the movement in a state in accordance with the most frequently performed daily movement. It is possible to test the wear of the artificial joint when it is actually attached to the human body with high accuracy.

DESCRIPTION OF SYMBOLS 1 Work axis side holder 3 Tool axis side holder 4 Liquid container 6 Sample 8 Test dish 11 Mounting part 13 Guide 15 Table 16 Sensor 17 Height adjuster 22 Position adjuster 31 Shaft 32 Receiving base 43 Sealing lid 45 Circular opening 46 Liquid seal Packing 61 Sphere A Workpiece axis B Tool axis

Claims (5)

A workpiece axis side holder (1) mounted on the rotating workpiece axis of the machine tool and a tool axis side holder (3) mounted on the rotating tool axis of the machine tool,
The work shaft side holder includes an attachment portion (11) fixed to the work shaft, a table (15) for fixing the sample (6), and the table when the attachment portion is fixed to the work shaft. The guide (13) for guiding along a linear direction orthogonal to the axis of the workpiece axis, and the linear direction of the table for allowing the center of the sphere of the sample fixed to the table to be held on the axis of the workpiece axis A height adjuster (17) for adjusting the position of the position, a position adjuster (22) for adjusting a position in a direction perpendicular to both the linear direction and the axis of the work axis, and the linear direction acting on the table Sensor (16) for detecting the force of
The tool shaft side holder is a prosthesis wear test device comprising a shaft (31) to be mounted on the tool shaft and a cradle (32) for fixing the test dish (8). A workpiece axis side holder (1) mounted on the rotating workpiece axis of the machine tool and a tool axis side holder (3) mounted on the rotating tool axis of the machine tool,
The workpiece shaft side holder includes an attachment portion (11) fixed to the workpiece shaft, a table (15) for fixing the test dish (8), and the table when the attachment portion is fixed to the workpiece shaft. A guide (13) for guiding along the axial direction of the workpiece axis, and a sensor (16) for detecting a force in the axial direction of the workpiece axis acting on the table,
The tool shaft side holder is a prosthesis wear test device comprising a shaft (31) mounted on the tool shaft and a cradle (32) for fixing the sample (6).   A liquid container (4) mounted on the work shaft side holder (1) is provided, and the shaft side surface (33) of the receiving base (32) of the tool shaft side holder is a partial spherical surface, and the liquid container is hermetically sealed. The lid (43) includes a circular opening (45) and a liquid seal packing (46) for liquid sealing the gap between the circular opening and the partial spherical surface, and the sample sphere and the test dish are sealed in a liquid container. The wear test apparatus according to claim 1, wherein the wear test apparatus is capable of relative oscillation. Using an NC machine tool equipped with a rotating workpiece axis and a rotating tool axis capable of controlling the rotation angle,
The work shaft side holder of the wear test device according to claim 1 is mounted on the work shaft of the machine tool, the tool shaft side holder of the device is mounted on the tool shaft, and the artificial joint ball is mounted on the work shaft side holder. The side sample is fixed, the test plate of the artificial joint is fixed to the tool axis side holder, and the NC axis of the machine tool is moved back and forth within the specified first angle range and the tool axis. A machining program that repeats an operation of reciprocatingly swinging in a specified second angle range and an operation of reciprocating the tool axis in the X-axis direction at the same cycle is registered, and the machining program is operated. , Artificial joint wear test method. Using an NC machine tool equipped with a rotary work axis capable of controlling the rotation angle and a tool axis capable of controlling a swing angle around an axis corresponding to the B axis in a lathe,
The work axis side holder of the wear test apparatus according to claim 2 is mounted on the work axis of the machine tool, the tool axis side holder of the apparatus is mounted on the tool axis, and the artificial joint test is performed on the work axis side holder. Fixing the pan, fixing the ball side sample of the artificial joint to the tool axis side holder, and reciprocatingly swinging the workpiece axis in the first angle range designated by the NC of the machine tool; and the tool axis And the center of the specimen sphere is held at the same position in synchronism with the reciprocal oscillation. In this way, the operation of moving the tool axis in both directions corresponding to the Z-axis direction and the X-axis direction of the lathe and the operation of reciprocating the tool axis in the direction corresponding to the Z-axis direction of the lathe are repeated at the same cycle. Register the program And wherein the operating the machining program, abrasion test method of the prosthesis.

Images