1、Designation: F1820 13Standard Test Method forDetermining the Forces for Disassembly of ModularAcetabular Devices1This standard is issued under the fixed designation F1820; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a standard methodology bywhich to measure the attachment strength between the modularacetabul
3、ar shell and liner.Although the methodology describeddoes not replicate physiological loading conditions, it has beendescribed as a means of comparing the integrity of variouslocking mechanisms.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are include
4、d in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to u
5、se.2. Referenced Documents2.1 ASTM Standards:2E4 Practices for Force Verification of Testing MachinesF2345 Test Methods for Determination of Static and CyclicFatigue Strength of Ceramic Modular Femoral Heads3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 acetabular linerportio
6、n of the modular acetabulardevice with an internal hemispherical socket intended toarticulate with the head of a femoral prosthesis. The externalgeometry of this component interfaces with the acetabular shellthrough a locking mechanism which may be integral to thedesign of the liner and shell or may
7、 rely upon additionalcomponents (for example, metal ring, screws, and so forth).3.1.2 acetabular shellthe external, hollow (usually metal)structure that provides additional mechanical support or rein-forcement for an acetabular liner and whose external featuresinterface directly with the bones of th
8、e pelvic socket (forexample, through bone cement, intimate press-fit, porousingrowth, integral screw threads, anchoring screws, pegs, andso forth). The acetabular shell may be either solid or containholes for fixation, or contain a hole for instrumentation, or allof these.3.1.3 locking mechanismany
9、structure, design feature orcombination thereof, that provides mechanical resistance tomovement between the liner and shell.3.1.4 polar axisthe axis of revolution of the rotationallysymmetric portions of the acetabular liner or shell.4. Summary of Test Method4.1 All acetabular liners shall be insert
10、ed into the acetabularshells for testing by applying a force of 2 kN. This value issimilar to the force required to set the head in Test MethodsF2345.4.2 Axial Disassembly:4.2.1 The axial disassembly of an acetabular device testmethod provides a means to measure the axial locking strengthof the acet
11、abular liner for modular acetabular devices.4.2.2 Following proper assembly of the acetabular liner inan acetabular shell, the assembled device is attached to afixture such that the cup opening is facing downward. Theacetabular shell is supported and an axial force is applied to theacetabular liner
12、until it disengages. The force required todisengage the acetabular liner from the acetabular shell isrecorded.4.3 Offset Pullout or Lever Out Disassembly:4.3.1 The offset pullout or the lever out disassembly methodis intended to assess the resistance of the locking mechanism toedge forces that could
13、 occur when the neck of a hip prosthesisimpinges on the edge of the acetabular liner. An impingingforce could cause the edge of the acetabular liner opposite thearea of impinging contact to be pushed out of the shell. Theresistance of the acetabular liner edge to being pulled loosefrom the shell is
14、a measure of the resistance to impingementcausing loosening of the acetabular liner.1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devicesand is the direct responsibility of SubcommitteeF04.22 on Arthroplasty.Current edition approved Feb. 1, 20
15、13. Published March 2013. Originallyapproved in 1997. Last previous edition approved in 2009 as F1820 97(2009).DOI: 10.1520/F1820-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume infor
16、mation, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.3.2 Following proper assembly of the acetabular liner inan acetabular shell, the assembled device is attached to
17、 afixture such that the cup opening is facing upward. Theacetabular shell is constrained from moving at a minimum offour locations spaced uniformly around the top circumferenceof the acetabular shell. For an offset pullout a force is appliedto a liner contact point, a location near the top surface o
18、f theliner. The line of action of the force is constrained to a directionthat is parallel to polar axis of the liner. The force required todisengage the acetabular liner from the acetabular shell isrecorded.4.3.3 For a lever out test, the force is applied through a levermechanism with a liner contac
19、t point near the top surface of theliner and a fulcrum that is outside the liner and directlyopposite the contact point. The centerline of the lever shallintersect the polar axis of the liner. The force required todisengage the acetabular liner from the acetabular shell shall berecorded. The distanc
20、es between the applied force and thefulcrum and the resultant force and the fulcrum are recorded.These values are used to calculate the lever-out force.4.4 Torque Out Disassembly:4.4.1 The torque out disassembly method is intended toassess the resistance of the locking mechanism to high frictioneven
21、ts that would attempt to rotate the acetabular liner withinthe acetabular shell.4.4.2 Following proper assembly of the acetabular liner inan acetabular shell, the assembled device is attached to afixture such that the shell opening is unimpeded, allowing theacetabular liner to be pushed free of the
22、shell. The acetabularshell is constrained from moving at a minimum of fourlocations spaced uniformly around the top circumference of theacetabular shell. A head of a diameter appropriate to the lineris attached to the liner at a minimum of four equally spacedlocations or adhesively bonded. A torque
23、is applied through thehead along the polar axis of the liner. The torque required todisengage the acetabular liner from the acetabular shell orbreak the adhesive bond between the articulating surfaces ofthe acetabular liner and the head is recorded.5. Significance and Use5.1 This test method is inte
24、nded to help assess the lockingstrength of the acetabular liner in a modular shell whensubjected to three different force application conditions.5.2 This test method may not be appropriate for all implantapplications. The user is cautioned to consider the appropriate-ness of the method in view of th
25、e materials and design beingtested and their potential application.5.3 While these test methods may be used to measure theforce required to disengage modular acetabular devices, com-parison of such data for various device designs must take intoconsideration the size of the implant and the type of lo
26、ckingmechanism evaluated. The location of the locking mechanismrelative to the load application may be dependent upon the sizeand design of the acetabular device. In addition, the lockingmechanism itself may vary with size, particularly if the designis circumferential in nature (for example, a large
27、r diameterimplants would have a greater area of acetabular shell/acetabular liner interface than a small diameter implant).5.4 Material failure is possible before locking mechanismfailure during either push-out or offset pullout/lever-out con-ditions. This is due to the possibility that the shear st
28、rength ofthe material may be exceeded before the locking mechanism isfully tested. If this occurs, those results shall be reported andsteps taken to minimize this effect. Some possibilities forminimizing shear might include utilizing the smallest sizecomponents, using a flat rod end rather than a ro
29、und rod end orplacing a small metal plate between the liner and shell (duringpush-out). For well-designed polyethylene inserts, it may notbe possible to push out or offset pullout/lever out the linerwithout fracture. In some cases, reporting the maximum forceand acknowledging that the true disassemb
30、ly force will behigher may be justified.6. Apparatus6.1 An apparatus capable of supporting only the acetabularshell while allowing the acetabular liner to be freely disas-sembled from the shell is required.6.2 The testing machine shall conform to the requirementsof Practices E4. The loads used to de
31、termine the attachmentstrength shall be within the range of the testing machine asdefined in Practices E4.6.3 The test machine shall be capable of delivering acompressive or tensile force at a constant displacement rate.The test machine shall have a load monitoring and recordingsystem.7. Sampling7.1
32、 All acetabular liners shall be representative of implantquality products. This shall include any sterilization or thermalprocesses which may alter the material properties or geometry.7.2 Apartially finished acetabular shell or permanent fixtureblock may be substituted for a completed acetabular she
33、llprovided that the internal materials, finish, locking mechanism,and geometry are identical to the actual acetabular shell.7.3 A minimum of five shell and liner assemblies shall betested in each of the three tests (axial, offset pullout orlever-out, and torque-out disassembly) to determine the disa
34、s-sembly values. Pairing of the acetabular shells and liners shallbe at random unless otherwise reported. For tests with poly-ethylene liners, the same five acetabular shells may be used foreach of the three tests provided that none of the shells aredamaged by any of the preceding tests.8. Procedure
35、8.1 Assembly Procedure:8.1.1 The liner shall be assembled in the shell with a peakforce of 2 kN 6 50 N. The force shall be applied indisplacement control at a rate of 0.04 mm/s or force control ata rate of 1 kN/s or less. The line of force application shall becoincident with the polar axis of the li
36、ner. The force may beapplied with the appropriate surgical instrument for the specificdevice, or a sphere of the same diameter as the diameter of thearticulating surface on the liner.8.2 Axial Disassembly:F1820 1328.2.1 Once assembled, the liner shell construct shall beplaced in a solid metallic fix
37、ture with continuous support of theshell as illustrated in Fig. 1. The fixture that supports theacetabular shell shall do so without visual evidence of defor-mation during or after the test. An axial force shall be applied(coincident with the polar axes of the liner and shell) to theliner through a
38、center hole (polar axis of the acetabular shell)in the shell at a rate of 5.1 cm/min with a round rod. Thedirection of force application and rod longitudinal axis shall becollinear to the polar axes of the liner and shell to within 2;and the center of the rod contact with the liner shall be less tha
39、n2 mm from the polar axis of the liner. It may be necessary tocreate a hole in the shell at the apex in order to apply an axialforce to the liner. A small diameter drill blank or rod could beused as a force applicator. The rod diameter shall not be lessthan 5 mm in diameter. If the rod diameter is t
40、oo small, it maypunch a hole in the liner during the test. The drill blank or rodshall be stiff enough that it does not buckle under the test forcesand there shall be sufficient clearance between any hole in theshell and the drill blank or rod such that there would be nocontact between the hole and
41、the drill blank or rod during thetest. The maximum force required to completely disengage theliner from the shell should be measured and recorded.8.2.2 Record the maximum disassembly force.8.2.3 The testing of any individual sample shall be termi-nated when one of the following has occurred.8.2.3.1
42、The disengagement force becomes negligible.8.2.3.2 Prior to disassembly, the liner suffers excessivedamage (that is, complete fracture of a portion of the liner orsevere liner deformation). Such occurrences shall be consid-ered an invalid test.8.2.4 For tests with thin polyethylene liners, the rod a
43、pply-ing the force could actually puncture the liner. If this occurs itmay be advisable to increase the cross-sectional area of the rod.If puncture still occurs, it may be possible to justify thepunctured liners as valid tests, if the liner is thin and the linerlocking mechanism is strong.8.3 Offset
44、 Pullout or Lever Out Disassembly:8.3.1 Prior to assembly, the liner shall have a rectangularslot cut or hole drilled into one side of the interior surface ofthe liner to use as the force application point for the test. Theslot shall be at least 8 mm long and 4 mm wide. The slot shallhave the long a
45、xis aligned roughly perpendicular to the loadaxis. The hole should be 4 to 6 mm in diameter. The slot or holeshould be approximately perpendicular to the polar axis. Thedepth of the slot or hole shall not exceed 50 % of the linerthickness at the location of the slot. The top edge of the slot orhole,
46、 h1 in Fig. 2 shall be approximately 80 % of the depth ofthe liner (h) (that is, the distance along the polar axis of theliner from the pole of the liner to the plane of the top surfaceof the liner) and should not interfere with the locking mecha-nism.8.3.2 Alternatively, it may be possible to adhes
47、ively bond ametal washer to the interior surface of the liner to use as theforce application point for the test. The location of the hole inthe washer shall meet the same requirements for the holelocation in 8.3.1. With ceramic liners, it may be necessary toadhesively bond a metal head into the line
48、r to perform this test.8.3.2.1 The surfaces of the ceramic liner and the head mustbe roughened to improve the adhesive bond.FIG. 1 Schematic of Liner DisassemblyF1820 1338.3.2.2 The head shall have internal surfaces machined sothat the force application point is at the appropriate heightlocation on
49、the liner noted in 8.3.1 and the tip of the forceapplication point is within 1 mm of the liner articulatingsurface.8.3.3 Once assembled, the liner shell assembly shall beplaced in a fixture similar to that illustrated in Fig. 2 and Fig.3. The exterior bottom will be supported on a flat plate and theshell shall be constrained tightly against the plate at a minimumof four locations spaced evenly around the edge of the shell.The top surface of the shell shall be parallel to the plate. Theforce of the constraint shall not be high enough to deform theshell.8.3.4 For the Offset Pul
