Fatigue test method of degradable alloy interface screw in body fluid environment
By designing an auxiliary assembly device and a simulated body fluid fatigue testing method, the problem of long-term retention of traditional titanium alloy interface screws in the body was solved. This enabled the fatigue performance testing of biodegradable alloy interface screws in a body fluid environment, determining their fatigue limit and improving testing efficiency and accuracy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-20
- Publication Date
- 2026-03-27
AI Technical Summary
Traditional titanium alloy interface screws may cause stress shielding, loosening, or allergies if left in the body for a long time, requiring a second surgery to remove them. Furthermore, biodegradable alloys in the body fluid environment cause the screw-bone interface bonding strength and shear resistance to continuously decrease due to electrochemical effects. Existing testing methods cannot cover this coupling effect of dynamic degradation and mechanical decay.
An auxiliary assembly device and a simulated body fluid fatigue testing method were designed, including a fixed base, a fatigue base, a sleeve, a bone simulator, an implant, and a ligament loading auxiliary device. The fatigue performance of the biodegradable alloy interface screw was tested by cyclic tensile force under simulated body fluid environment.
This invention enables fatigue testing of biodegradable alloy interface screws in a body fluid environment, determines their fatigue limit, improves testing efficiency and accuracy, and ensures the reliability of test results.
Smart Images
Figure CN121740586A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of bone implant testing, in particular to a fatigue test method of degradable alloy interface screw in a body fluid environment. BACKGROUND
[0002] After traditional titanium alloy interface screw is used for ligament reconstruction, it may cause stress shielding, loosening or allergy and needs to be removed by secondary surgery, thereby increasing the pain of patients. In a body fluid environment, the degradable alloy continuously degrades due to electrochemical action, generates hydrogen gas and metal ions, and causes the continuous decline of the key mechanical properties such as the bonding strength and shear resistance of the screw-bone interface. The coupling effect of 'dynamic degradation-mechanical attenuation' cannot be covered by the traditional metal screw test method. Therefore, the present application provides a fatigue test method of degradable alloy interface screw in a body fluid environment. SUMMARY
[0003] The purpose of the present application is to provide a fatigue test method of degradable alloy interface screw in a body fluid environment.
[0004] To solve the above technical problems, the purpose of the present application is achieved as follows: A fatigue test method of degradable alloy interface screw in a body fluid environment, comprising the following steps: S1, auxiliary assembly device assembly; the auxiliary assembly device comprises a fixed base, a fatigue base, a sleeve and a bone simulation object, the auxiliary assembly device assembly comprises assembly of the fixed base and the fatigue base and assembly of the sleeve and the bone simulation object; the fixed base comprises a base and a top base arranged at intervals, and a circular hole is formed in each of the base and the top base, and the two circular holes are concentrically arranged; the fatigue base is connected to the base of the fixed base by magnetic attraction, and the fatigue base is provided with a circular through hole concentric with the circular hole, and the top of the circular through hole is provided with a stepped structure; the sleeve is in a cylindrical structure and is installed at the top of the fatigue base and is concentrically arranged with the circular through hole; the bone simulation object is arranged in the sleeve and abuts against the stepped structure at the bottom end; S2, drilling; the drill bit is drilled from the top of the fixed base to the bottom, passes through the circular hole and drills a through hole on the bone simulation object along the axis of the bone simulation object; S3, implant assembly; the implant includes an inner core, a shell and a ligament simulator, the implant assembly includes the assembly of the inner core and the shell and the assembly of the ligament simulator and the shell; the inner core axis is provided with a through hole, the outer wall is provided with a plurality of ring protrusions, and the top is provided with a plurality of fixing ears; the shell is made of degradable alloy, is hollow inside, is open at the top, is provided with a bottom hole, and is provided with a plurality of anti-skid teeth on the side wall; the anti-skid teeth are made of degradable alloy, the bottom edge is connected with the shell, and the thickness is greater than the wall thickness of the shell, so that the anti-skid teeth protrude from the side wall of the shell; the number of ligament simulators is several, which are attached to the outer wall of the shell, the upper part is connected with the fixing ear, the bottom end is provided with a hole and is fixed with a fixing line, and the fixing line extends from the through hole of the inner core to the top of the inner core and is fixedly connected with the fixing ear; S4, implant implantation; the assembled implant is inserted into the through hole of the bone simulator, and the ligament simulator is partially left outside the through hole of the bone simulator; after the implant implantation is completed, the connection between the ligament simulator and the fixing line and the fixing ear is loosened, the fixing line is pulled out, and then the inner core is pulled out of the shell; S5, anchor screwing; the anchor screw made of degradable alloy is screwed into the shell from the top of the shell, so that the anti-skid teeth protrude from the outer wall of the shell, and the ligament simulator is extruded to tightly fit the bone simulator; S6, assembly of ligament loading auxiliary device; the ligament loading auxiliary device includes a pulley block, the pulley block includes a plurality of pulleys arranged in a row, a loading connecting line is slidably connected to the pulleys, and the two ends of the loading connecting line are fixedly connected with the top ends of two oppositely arranged ligament simulators; S7, test assembly is installed into a simulated body fluid fatigue device; the fatigue base, the sleeve, the bone simulator and the implant implanted into the through hole of the bone simulator are installed into the simulated body fluid fatigue device, the top end of the pulley block is connected with a loading mechanism, and the loading mechanism applies periodic tensile force to the ligament simulator.
[0005] On the basis of the above scheme and as a preferred scheme of the above scheme, the implant further includes a guide, the guide includes a ring body and a guide sliding groove arranged on the ring body, the ring body is matched with the bottom end of the shell and can be attached to the bottom end of the shell; the number of the guide sliding grooves is the same as that of the ligament simulators, and the guide sliding grooves are used for guiding the fixing line.
[0006] On the basis of the above scheme and as a preferred scheme of the above scheme, the anchor screw is provided with a connecting through hole along the axis of the anchor screw, the connecting through hole can be matched with a rotating tool to realize torque transmission.
[0007] On the basis of the above scheme and as a preferred scheme of the above scheme, the simulated body fluid fatigue device comprises a device base, a barrel is arranged on the device base, a barrel cover is arranged at the top of the barrel, and an opening is arranged at the center of the barrel cover; the fatigue base is arranged inside the barrel and is detachably connected to the device base.
[0008] On the basis of the above scheme and as a preferred scheme of the above scheme, a drainage groove is arranged on the outside of the barrel of the device base, and a drainage pipe is connected to the drainage groove.
[0009] Compared with the prior art, the present application has the following advantages and beneficial effects: the present application provides a fatigue test method of an interface screw of a degradable alloy material in a simulated body fluid environment, so as to determine the fatigue limit of the interface screw of the degradable alloy material in the human body. The auxiliary assembly device can quickly implant the screw into the bone simulation object, thereby improving the test efficiency; meanwhile, the load borne by each ligament simulation object is guaranteed to be kept on the axis through the pulley block, so that the test result is more accurate. BRIEF DESCRIPTION OF DRAWINGS
[0010] Figure 1 It is an auxiliary assembly device structure schematic diagram of the present application.
[0011] Figure 2 It is an explosion structure schematic diagram of the interface screw and the auxiliary assembly device of the present application.
[0012] Figure 3 It is a simulated body fluid fatigue device structure schematic diagram of the present application.
[0013] Figure 4 It is a structure schematic diagram of the test assembly body inside the simulated body fluid fatigue device of the present application.
[0014] Figure 5 It is a test assembly body structure schematic diagram of the present application.
[0015] Figure 6 It is an assembly body explosion structure schematic diagram of the present application.
[0016] Figure 7 It is a guider structure schematic diagram of the present application.
[0017] In the figure: 1, fixed base; 2, fatigue base; 3, sleeve; 4, bone simulation object; 5, inner core; 6, shell; 7, ligament simulation object; 8, guider; 9, fixed lug; 10, anti-skid tooth; 11, pulley; 12, loading connecting line; 13, anchor; 14, device base; 15, barrel; 16, barrel cover; 17, drainage groove; 18, drainage pipe. DETAILED DESCRIPTION
[0018] In order for those skilled in the art to better understand the technical solutions of the present application, the preferred embodiments of the present application are described below in combination with specific examples, but it should be understood that the drawings are only used for illustrative description and cannot be understood as a limitation to the present patent; in order to better illustrate the present embodiment, some components in the drawings may be omitted, enlarged or reduced, and do not represent the actual size of the product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted. The positional relationship described in the drawings is only used for illustrative description and cannot be understood as a limitation to the present patent.
[0019] A fatigue test method of a degradable alloy interface screw in a body fluid environment, comprising the following steps: S1, auxiliary assembly device assembly, so that the bone simulation 4 is fixed on the auxiliary assembly device, facilitating the implementation of subsequent steps.
[0020] S2, drilling, drilling a through hole on the bone simulation 4.
[0021] S3, implant assembly, assembling the shell 6 of the screw, the inner core 5 for guiding and the ligament simulation 7 together, so as to implant into the bone simulation 4.
[0022] S4, implant implantation, implanting the implant assembled in step S3 into the hole of the bone simulation 4.
[0023] S5, anchor screwing, screwing the anchor 13 of the screw into the shell 6, expanding the anti-skid teeth 10 on the shell 6, and realizing the close fit of the ligament simulation 7 and the bone simulation 4.
[0024] S6, ligament loading auxiliary device assembly, connecting the top end of each ligament simulation 7 with the ligament loading auxiliary device together, facilitating the simultaneous loading of each ligament simulation 7.
[0025] S7, test assembly installation to the simulated body fluid fatigue device, after fixation, adding simulated body fluid to start fatigue test.
[0026] Among them, step S1 includes: the auxiliary assembly device includes a fixed base 1, a fatigue base 2, a sleeve 3 and a bone simulation 4. The auxiliary assembly device assembly includes the assembly of the fixed base 1 and the fatigue base 2 and the assembly of the sleeve 3 and the bone simulation 4.
[0027] As Figure 1 and Figure 2As shown, the fixed base 1 includes a spacer arranged base and top seat, and the base and top seat are provided with a circular hole, and the two circular holes are concentrically arranged. The fatigue base 2 is connected to the base of the fixed base 1 by magnetic attraction, and the fatigue base 2 is provided with a circular through hole concentric with the circular hole, and the top of the circular through hole is provided with a stepped structure. The sleeve 3 is in a cylindrical structure, which is detachably and fixedly connected to the top of the fatigue base 2, and is concentrically arranged with the circular through hole. The bone simulator 4 is arranged in the sleeve 3, and the bottom end abuts against the stepped structure and is limited by the stepped structure and cannot move downward any more.
[0028] Step S2 includes: the drill bit is downward from the fixed base 1, passes through the circular hole, and drills a through hole on the bone simulator 4 along the axis of the bone simulator 4. The through hole penetrates the bone simulator 4.
[0029] Step S3 includes: the implant includes an inner core 5, a shell 6 and a ligament simulator 7, and the implant assembly includes the assembly of the inner core 5 and the shell 6 and the assembly of the ligament simulator 7 and the shell 6.
[0030] As shown in Figure 6 , the inner core 5 is provided with a through hole in the center along its axis, and the outer wall is provided with a plurality of ring protrusions, and the top is provided with a plurality of fixed ears 9. The ring protrusion is annularly protruded from the side surface of the inner core 5. The fixed ears 9 are uniformly distributed along the circumference of the inner core 5.
[0031] The shell 6 is made of degradable alloy, hollow inside, open at the top, and has a hole at the bottom. A plurality of anti-skid teeth 10 are arranged on the side wall of the shell 6. The material of the anti-skid teeth 10 is the same degradable alloy as the shell 6, and the bottom edge is connected with the shell 6, which is integrally formed. The thickness of the anti-skid teeth 10 is greater than the wall thickness of the shell 6, so as to protrude from the side wall of the shell 6, and the outer wall of the anti-skid teeth 10 has teeth. The anti-skid teeth 10 are integrally formed with the shell 6, and are elastically connected with each other, so that the anti-skid teeth 10 can move relative to the shell 6. Preferably, the plurality of anti-skid teeth 10 are divided into a plurality of groups, each group including a plurality of anti-skid teeth 10 uniformly distributed along the circumference of the shell 6, and each group of anti-skid teeth 10 corresponds to the ring protrusion of the inner core 5. When the inner core 5 is inserted into the shell 6, the anti-skid teeth 10 are spread.
[0032] As shown in Figure 4 and Figure 5 , the ligament simulator 7 is a plurality of ligament simulators, which are attached to the outer wall of the shell 6, and the upper part is connected with the fixed ear 9, and the bottom end is provided with a hole and is fixed with a fixed line. The fixed line extends from the through hole of the inner core 5 to the top of the inner core 5 and is fixedly connected with the fixed ear 9. By fixing the ligament simulator 7, it is convenient to insert the ligament simulator 7 into the through hole of the bone simulator 4 together with the shell 6 and the inner core 5.
[0033] Further, in order to improve the stability and prevent the ligament simulator 7 from slipping, a guide 8 is arranged at the bottom end of the shell 6. As shown in Figure 7As shown, the guide 8 includes a ring body and guide slots arranged on the ring body, the ring body is matched with the bottom end of the sleeve 6 and can be attached to the bottom end of the sleeve 6. The number of guide slots is the same as that of the ligament simulators 7, which are used to guide the fixing wires. The positions and numbers of the guide slots correspond to the fixing ears 9, so that the ligament simulators 4 remain vertical and do not tilt when fixed.
[0034] Step S4 includes inserting the assembled implant into the through hole of the bone simulator 4, and the top part of the ligament simulator 7 is left outside the through hole of the bone simulator 4. After the implant is implanted, the connection between the ligament simulator 7 and the fixing wire and the fixing ear 9 is loosened, the fixing wire is pulled out, and then the inner core 5 is pulled out of the sleeve 6. After the fixing wire is pulled out, the guide 8 is not bound and falls out of the through hole of the bone simulator 4 under gravity.
[0035] Step S5 includes rotating the anchor 13 made of a degradable alloy material into the sleeve 6 from the top end of the sleeve 6, extruding the anti-skid teeth 10 outward to ensure that the anti-skid teeth 10 protrude from the outer wall of the sleeve 6, and extruding the ligament simulator 7 to make it closely attached to the bone simulator 4. At this point, the interface screw is implanted into the bone simulator 4 and the ligament simulator 7 is fixed. The anchor 13 has a connecting through hole along its axis in the center, which can be matched with a rotating tool to realize torque transmission. The cross section of the connecting through hole is in the shape of a plum blossom. The surface of the anchor 13 has threads.
[0036] Step S6 includes that the ligament loading auxiliary device includes a pulley block, the pulley block includes a plurality of pulleys 11 arranged in a row, a loading connecting wire 12 is slidably connected to the pulleys 11, and the two ends of the loading connecting wire 12 are fixedly connected to the top ends of two oppositely arranged ligament simulators 7. In this embodiment, the ligament simulators 7 are four, and the number of pulleys 11 is two, one pulley 11 corresponds to two opposite ligament simulators 7, and the ligament simulators 7 are driven to stretch through the loading connecting wire 12.
[0037] Step S7 includes installing the fatigue base 2, the sleeve 3, the bone simulator 4, and the implant implanted into the through hole of the bone simulator 4 into the simulated body fluid fatigue device, connecting the top end of the pulley block to the loading mechanism, and applying a periodic tensile force to the ligament simulator 7 by the loading mechanism.
[0038] As shown in Figure 3 and Figure 4 , the simulated body fluid fatigue device includes a device base 14, the device base 14 is provided with a barrel 15, the top of the barrel 15 is provided with a barrel cover 16, and the center of the barrel cover 16 is provided with an opening. The fatigue base 2 is placed inside the barrel 15 and can be detachably connected to the device base 14. The sleeve 3, the bone simulator 4, the sleeve 6, the anchor 13, and the ligament simulator 7 on the fatigue base 2 are fixed inside the barrel 15. The pulley block is connected to the loading mechanism through the opening in the center of the barrel cover 16.
[0039] A water drainage groove 17 is arranged on the device base 14 outside the cylinder 15, and a water drainage pipe 18 is connected to the water drainage groove 17. The water drainage groove 17 and the water drainage pipe 18 are used for the drainage of the simulated body fluid in the cylinder.
[0040] The preferred embodiments of the present application are described in detail above. It should be understood that those of ordinary skill in the art can make modifications and variations without departing from the concept of the present application. Therefore, any technical solution obtained by logical analysis, reasoning or limited experiments based on the prior art according to the concept of the present application should be within the scope of protection defined by the claims.
Claims
1. A fatigue testing method for a biodegradable alloy interface screw in a body fluid environment, characterized in that, Includes the following steps: S1. Assembly of auxiliary assembly device; The auxiliary assembly device includes a fixed base (1), a fatigue base (2), a sleeve (3) and a skeleton simulator (4). The assembly of the auxiliary assembly device includes the assembly of the fixed base (1) and the fatigue base (2) and the assembly of the sleeve (3) and the skeleton simulator (4). The fixed base (1) includes a base and a top seat arranged at intervals, and both the base and the top seat are provided with circular holes, and the two circular holes are arranged concentrically. The fatigue base (2) is magnetically connected to the base of the fixed base (1), and the fatigue base (2) is provided with a circular through hole concentric with the circular hole, and the top of the circular through hole is provided with a stepped structure. The sleeve (3) is cylindrical and is installed on the top of the fatigue base (2), and is arranged concentrically with the circular through hole. The skeleton simulator (4) is disposed inside the sleeve (3), and its bottom end abuts against the stepped structure. S2. Drilling: The drill bit moves downward from above the fixed base (1), passes through the circular hole, and drills a through hole on the bone simulator (4) along the axis of the bone simulator (4); S3. Implant assembly; the implant includes an inner core (5), a shell (6), and a ligament simulator (7). The implant assembly includes the assembly of the inner core (5) and the shell (6) and the assembly of the ligament simulator (7) and the shell (6). The inner core (5) has a through hole along its axis, several annular protrusions on its outer wall, and several fixing ears (9) on its top. The shell (6) is made of a biodegradable alloy, is hollow inside, has an opening at the top, an opening at the bottom, and several fixing ears (9) on its side wall. Anti-slip teeth (10), the anti-slip teeth (10) are made of biodegradable alloy, the bottom edge is connected to the shell (6), and the thickness is greater than the wall thickness of the shell (6) so as to protrude from the side wall of the shell (6); the number of ligament simulation materials (7) is several, which are attached to the outer wall of the shell (6), the upper part is connected to the fixing ear (9), the bottom end is opened and a fixing line is passed through it, the fixing line extends from the through hole of the inner core (5) to the top of the inner core (5) and is fixedly connected to the fixing ear (9); S4. Implantation: Insert the assembled implant into the through hole of the bone simulator (4), with part of the ligament simulator (7) remaining outside the through hole of the bone simulator (4); after implantation, loosen the connection between the ligament simulator (7) and the fixation line and the fixation ear (9), remove the fixation line, and then remove the inner core (5) from the shell (6). S5. Anchor screw in; The biodegradable alloy anchor (13) is screwed into the shell (6) from the top of the shell (6) downwards to ensure that the anti-slip teeth (10) protrude from the outer wall of the shell (6) and squeeze the ligament simulator (7) so that it fits tightly with the bone simulator (4); S6. Ligament loading auxiliary device assembly; The ligament loading auxiliary device includes a pulley group, the pulley group includes several pulleys (11) arranged in a row, and a loading connecting line (12) is slidably fitted on the pulley (11). The two ends of the loading connecting line (12) are respectively fixedly connected to the top ends of two oppositely arranged ligament simulation objects (7). S7. The test assembly is installed into the simulated body fluid fatigue device. The fatigue base (2), the sleeve (3), the bone simulator (4) and the implant implanted in the through hole of the bone simulator (4) are installed into the simulated body fluid fatigue device. The top of the pulley group is connected to the loading mechanism, and the loading mechanism applies a periodic tensile force to the ligament simulator (7).
2. The fatigue testing method for a biodegradable alloy interface screw in a body fluid environment according to claim 1, characterized in that, The implant also includes a guide (8), which includes an annular body and a guide groove disposed on the annular body. The annular body is adapted to the bottom end of the shell (6) and can fit against the bottom end of the shell (6). The number of guide grooves is the same as the number of ligament simulators (7) and is used to guide the fixation line.
3. The fatigue testing method for a biodegradable alloy interface screw in a body fluid environment according to claim 1, characterized in that, The anchor (13) has a connecting through hole along its axis at its center. The connecting through hole can be used with a rotating tool to transmit torque.
4. The fatigue testing method for a biodegradable alloy interface screw in a body fluid environment according to claim 1, characterized in that, The simulated body fluid fatigue device includes a device base (14), a cylinder (15) is provided on the device base (14), a cylinder cover (16) is provided on the top of the cylinder (15), and an opening is provided in the center of the cylinder cover (16); the fatigue base (2) is placed inside the cylinder (15) and is detachably connected to the device base (14).
5. The fatigue testing method for a biodegradable alloy interface screw in a body fluid environment according to claim 4, characterized in that, A drainage groove (17) is provided on the base (14) of the device on the outside of the cylinder (15), and the drainage groove (17) is connected to a drainage pipe (18).