ASTM_F_1854_-_15.pdf

Designation:F185415Standard Test Method forStereological Evaluation of Porous Coatings on MedicalImplants1This standard is issued under the fixed designation F1854;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 stereological test methods forcharacterizing the coating thickness,void content,and meanintercept length of various porous coatings adhering to nonpo-rous substrates.1.2 A method to measure void content and intercept lengthat distinct levels(“Tissue Interface Gradients”)through theporous coating thickness is outlined in 9.4.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 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:2E3 Guide for Preparation of Metallographic SpecimensE883 Guide for ReflectedLight Photomicrography3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 fieldthe image of a portion of the working surfaceupon which measurements are performed.3.1.2 interceptthe point on a measurement grid line pro-jected on a field where the line crosses from solid to void orvice versa.3.1.3 measurement grid linesan evenly spaced grid ofparallel lines all of the same length.3.1.4 porous coatingcoating on an implant deliberatelyapplied to contain void regions with the intent of enhancing thefixation of the implant.3.1.5 substratethe solid material to which the porouscoating is attached.3.1.6 substrate interfacethe region where the porous coat-ing is attached to the substrate.3.1.7 tissue interfacethe surface of the coating that shallhave first contact with biological tissue(i.e.,the top of thecoating).3.1.8 working surfacethe ground and polished face of themetallographic mount where the images of the fields arecaptured.4.Summary of Test Method4.1 Mean Coating ThicknessEvenly spaced parallel gridlines are oriented perpendicular to the coating-substrate inter-face on a field.For each gridline,the distance from thecoating-substrate interface to the last contact with the porouscoating material is measured as the coating thickness.Theaverage of all of the coating thickness measurements obtainedfrom all the measured fields is the mean coating thickness forthat coating.4.2 Volume Percent VoidA regular grid of points is super-imposed on a field from the working surface.The percentage ofpoints that are in contact with void areas in the coating is thevolume percent of void present in that field.4.3 Mean Void Intercept LengthMeasurement grid linesare oriented parallel to the substrate interface in a field.Theaverage length of the line segments overlaying the void spaceis the mean void intercept length for that field.This is arepresentative measure of the scale,or size,of the pores in aporous structure.4.4 Tissue Interface GradientsThe Volume Percent Voidand the Mean Void Intercept Length are characterized in three200-m-thick zones below the Tissue Interface in each field.5.Significance and Use5.1 All these test methods are recommended for elementaryquantification of the morphological properties of porous coat-ings bonded to solid substrates.1This test method is under the jurisdiction ofASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved March 15,2015.Published May 2015.Originallyapproved in 1998.Last previous edition approved in 2009 as F1854 09.DOI:10.1520/F1854-15.2For 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 5.2 These test methods may be useful for comparativeevaluations of different coatings or different lots of the samecoating.5.3 All the methods should be performed on the same set ofimages of fields.5.4 A statistical estimate can be made of the distributions ofthe mean coating thickness and the volume percent void.Noestimate can be made of the distribution of intercept lengths.5.5 There are limits to the accurate characterization ofporosity,depending on spacing between the lines in the linegrid(or points in the point grid)and the individual andcumulative fields used for the measurements.Increasing thesize of the fields,increasing the number of fields,or decreasingthe gr