ASTM_F_2996_-_13.pdf

Designation:F299613Standard Practice forFinite Element Analysis(FEA)of Non-Modular MetallicOrthopaedic Hip Femoral Stems1This standard is issued under the fixed designation F2996;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 practice establishes requirements and consider-ations for the numerical simulation of non-modular(that is,limited to monolithic stems with only a femoral head/trunniontaper interface)metallic orthopaedic hip stems using FiniteElement Analysis(FEA)techniques for the estimation ofstresses and strains.This standard is only applicable to stressesbelow the yield strength,as provided in the material certifica-tion.1.2 PurposeThis practice establishes requirements andconsiderations for the development of finite element models tobe used in the evaluation of non-modular metallic orthopaedichip stem designs for the purpose of prediction of the staticimplant stresses and strains.This procedure can be used forworst case assessment within a family of implant sizes toprovide efficiencies in the amount of physical testing to beconducted.Recommended procedures for performing modelchecks and verification are provided to help determine if theanalysis follows recommended guidelines.Finally,the recom-mended content of an engineering report covering the mechani-cal simulation is presented.1.3 LimitsThis practice is limited in discussion to thestatic structural analysis of non-modular metallic orthopaedichip stems(which excludes the prediction of fatigue strength).1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 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 ISO Standards:2ISO 7206-4(2010)Implants for SurgeryPartial and TotalHip Joint ProsthesesPart 4:Determination of EnduranceProperties and Performance of Stemmed Femoral Com-ponents3.Significance and Use3.1 This practice is applicable to the calculation of stressesseen on a femoral hip stem when loaded in a manner describedin ISO 7206-4(2010).This method can be used to establish theworst case size for a particular implant.When stresses calcu-lated using this practice were compared to the stresses mea-sured from physical strain gauging techniques performed attwo laboratories using two different methods,the resultscorrelated to within 8%.4.Geometric Data4.1 Finite element models are based on a geometric repre-sentation of the device being studied.The source of thegeometric details can be obtained from drawings,solid models,preliminary sketches,or any other source consistent withdefining the model geometry.In building the finite elementmodel,certain geometric details may be omitted from theorthopaedic implant geometry shown in the CAD model if it isdetermined that they are not relevant to the intended analysis.Engineering judgment shall be exercised to establish the extentof model simplification and shall be justified.4.2 It is most appropriate to consider the“worst case”stresscondition for the orthopaedic implant being simulated.The“worst case”shall be determined from all relevant engineeringconsiderations,such as stem geometry,dimensions,and headoffset.If finite element analysis is being used for determiningthe worst case,then the worst case head offset may not beknown.It may be necessary to run several variants of headoffset,in order to determine this.1This practice is under the jurisdiction ofASTM Committee F04 on Medical andSurgical Materials and Devices and is the direct responsibility of SubcommitteeF04.22 on Arthroplasty.Current edition approved July 15,2013.Published August 2013.DOI:10.1520/F2996-13.2Available from International Organization for Standardization(ISO),1,ch.dela Voie-Creuse,CP 56,CH-1211 Geneva 20,Switzerland,http:/www.iso.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.Material Properties5.1 The required material properties for input into an FEAmodel for the calculation of strains and displacement aremodulus of elasticity(E)and Poissons ratio().These valuescan be obtained from material certification data.It should benoted that as ISO 7206-4(2010)is run under load control,theFEA should also be run under load control.When the FEA isrun under load control,the modulus of elasticity will not affectthe stress calculations under small displacement theory but willaffect displacement and strain.The influence of Poissons ratioon the stress calculations is negligible.5.2 Ensure that material pr