ASTM_F_1820_-_13.pdf

Designation:F182013Standard 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 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 modularacetabular 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 included 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 use.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 linerportion 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 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 the 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 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 inserted 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 acetabular 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 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 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 a measure of the resistance to impingementcausing loosening of the acetabular liner.1This test method is under the jurisdiction ofASTM Committee F04 on Medicaland Surgical Materials and Devicesand is the direct responsibility of SubcommitteeF04.22 on Arthroplasty.Current edition approved Feb.1,2013.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 information,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 States1 4.3.2 Following proper assembly of the acetabular liner inan acetabular shell,the assembled device is attached to afixture such that the cup opening is facing 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 poi