1、Designation: F2979 14Standard Guide forCharacterization of Wear from the Articulating Surfaces inRetrieved Metal-on-Metal and other Hard-on-Hard HipProstheses1This standard is issued under the fixed designation F2979; the number immediately following the designation indicates the year oforiginal ado
2、ption 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 guide specifies a method to measure the in-vivowear of explanted M
3、etal-on-Metal (MoM) and other “hard”(e.g., ceramic) hip components. The guide covers the measure-ment of acetabular cups and femoral heads using a dimensionalchange method and is applicable to all prosthetic hip types,including stemmed (modular) and resurfacing hip systems.1.2 The methods specified
4、in this guide are not applicablefor measuring the in-vivo wear from non-articulating surfaces,for example modular connections (at the stem/neck, neck/heador cup liner/shell interface) or at acetabular cup rim.1.3 The parameters (wear depth and volumetric wear)evaluated and reported in this guide are
5、 estimated from theassumed as-manufactured shape of the components. The wearvolume is calculated using a numerical integration method andthe wear depth is the difference between the assumed as-manufactured shape and the measured surface.1.4 This guide covers the measurement of the depth of wearand t
6、he volumetric wear using a Coordinate Measuring Ma-chine (CMM) and the depth of wear using an RoundnessMachine. Other metrology measurement equipment may beused to measure the wear depth or volume if the resolution andaccuracy of the measurements are comparable with the instru-ments detailed in this
7、 standard. The measurement and analysisprotocols should be based on those described in this standard.1.5 This guide is applicable to hip joints which are nomi-nally spherical at the time of manufacture. Form deviationsresulting from manufacturing or deformation may occur andmay necessitate the use o
8、f a non-spherical surface to representthe unworn surface of the component. Hip joints designed withasymmetry are considered beyond the scope of this guide,although the principles and techniques may be applicable to thecharacterization of wear from the articulating surfaces.1.6 This guide is intended
9、 as an extension toASTM F561 asa Stage II nondestructive test.1.7 This standard may involve hazardous materials, opera-tions and equipment. As a precautionary measure, explanteddevices should be sterilized or disinfected by an appropriatemeans that does not adversely affect the implant or theassocia
10、ted tissue that may be the subject of subsequentanalysis. A detailed discussion of precautions to be used inhandling human tissues can be found in ISO 12891-1. Thisstandard does not purport to address all of the safety concerns,if any, associated with its use. It is the responsibility of the userof
11、this standard to establish appropriate safety and healthpractices and determine the applicability of regulatory limita-tions prior to use.2. Referenced Documents2.1 ASTM Standards:2F561 Practice for Retrieval and Analysis of MedicalDevices, and Associated Tissues and FluidsF2033 Specification for To
12、tal Hip Joint Prosthesis and HipEndoprosthesis Bearing Surfaces Made of Metallic,Ceramic, and Polymeric Materials2.2 ISO Standard:3ISO 12181-1-2003 Part 1 Geometrical product specifica-tions roundness, vocabulary and parameters of roundness3. Terminology3.1 Definitions:3.1.1 For the purposes of this
13、 standard the following defi-nitions shall apply.3.1.2 cup rimthe circle formed by the intersection of thearticulating surface and the plane normal to the revolution axisthat lies coincident with the extreme point of the open cup face.1This test method is under the jurisdiction of ASTM Committee F04
14、 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.22 on Arthroplasty.Current edition approved Feb. 1, 2014. Published April 2014. DOI: 10.1520/F2979-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Servic
15、e at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.Copyright ASTM International, 100
16、Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.3 edge wearthe pattern of wear observed in acetabularcups in which the maximum wear depth occurs at the cup rimand progressively deceases along a path from the cup rim to thepole (1-3).43.1.4 equator of the articulat
17、ing surfacethe equator of thearticulating surface is the circle normal to the revolution axis ofthe component and to the spherical articulating surface.3.1.5 form deviationsdeviations from the nominal de-signed spherical shape of the hip implants that are not the resultof wear. Form deviations shall
18、 be separated from wear by theanalysis and measurement protocol to prevent errors in thecalculated wear. Form deviations may result from manufactur-ing tolerances or deformation during implantation or revisionprocedures. Typically, hip implants are symmetrical around therevolution axis.3.1.6 maximum
19、 inscribed circlethe reference circle ofmaximum radius that is totally enclosed by the measuredprofile. ISO 12181-1-20033.1.7 minimum circumscribed arcthe reference arc of theminimum radius that totally encloses the measured profile. ISO12181-1-20033.1.8 pole of articulating surfacethe pole of an ar
20、ticulat-ing surface is defined by a point at the intercept of therevolution axis of the component and the spherical articulationsurface.3.1.9 root mean square errorthe statistical measure of themagnitude of the variation between the assumed manufacturedcomponent shape fitted to the unworn regions an
21、d the mea-sured data points in the unworn regions.RMS Error 5 1n xn2!12 (1)where:x = the deviation between the assumed shape and eachmeasured data point for n data points.3.1.10 volumetric wearthe volume of material removedfrom the articulating surface as a result of in-vivo wear.3.1.11 weardeviatio
22、ns from the as-manufactured shapedue to loss of material from the articulating surfaces of thecomponents through abrasive, adhesive, or fatigue wearmechanisms, or by corrosion, or any combination of thesemechanisms.3.1.12 wear depththe maximum penetration normal to thearticulating surface due to in-
23、vivo wear.3.1.13 wear ratethe volumetric wear rate (mm3/year) orthe penetration wear rate (mm/year) is calculated by dividingthe wear volume or maximum wear depth by the timeimplanted in years. The wear rate is an average of the wearover the life of the component. The wear rate of hip joints maychan
24、ge over the life of component with an initial “running in”or “bedding-in” wear rate and the subsequent lower “steadystate” wear rate (4).4. Measurement Preparation4.1 All components shall be cleaned in accordance with theprocedure detailed in ASTM F561. Ensure that there are nodeposits on the articu
25、lating surface of the components thatmight interfere with or induce errors in the measurements.4.2 The temperature of the analysis laboratory shall bemaintained at 20C 6 2C. The components shall be main-tained at the temperature of the analysis laboratory for at least24 hours before the measurement
26、to ensure dimensionalstability.4.3 Apparatus3D Coordinate measuring machine with amaximum permissible error of 2 m over the largest dimensionof the component, or a computer numerical control (CNC)controlled Roundness Machine with automated centering andleveling. The maximum runout of the air-bearing
27、 spindle shallbe 6 20 nm, and the minimum gauge resolution shall be 6 30nm.NOTE 1When centering and leveling to align the component coordi-nate system with the machine coordinate system, care must be taken toreference from unworn regions of the component.5. Measurement of Components Using a Coordina
28、teMeasuring Machine5.1 Measurement of Acetabular Cup:5.1.1 Align the origin of CMM coordinate system with thecenter of the articulating surface of the component, and thehorizontal plane of the coordinate system parallel to the planeof the cup rim. Nondestructively mark the retrievedcomponent, or ide
29、ntify a landmark feature to provide an4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.FIG. 1 Schematic Diagram Terminology for Head and Cup GeometryF2979 142angular reference around the axis of rotational symmetry, sothat the measured wear location can
30、 be co-registered with theposition on the actual component.5.1.2 Measure data points from the bearing surface so thatthe maximum spacing between the data points along lines oflatitude or longitude is not greater than 0.5 mm (5) as shown inFig. 2. The mesh may be applied and profiles measured in alat
31、itudinal or longitudinal pattern, or a combination to give theoptimum point spacing over the component. The distancebetween the measured data points and the cup rim shall not begreater than 1 mm.NOTE 2The 0.5 mm mesh spacing is based on minimizing the errorsof calculating the wear volume when using
32、a simple linear “triangulation”integration method to calculate the wear volume (5). A larger pointspacing may be used if a sensitivity analysis is carried out to investigatethe effect of mesh spacing on the wear depth and volume, and the valuescan be shown to converge.5.2 Measurement of Femoral Head
33、:5.2.1 Align the origin of the CMM coordinate system withthe center of the unworn regions of the articulating surface ofthe component, with the revolution axis of the head perpen-dicular to the coordinate system horizontal plane. Nondestruc-tively mark the retrieved component, or identify a landmark
34、feature to provide an angular reference around the axis ofrotational symmetry.5.2.2 Measure data points from the bearing surface so thatthe maximum spacing between the data points along the linesof latitude or longitude is not greater than 0.5 mm as shown inFig. 3(5). The mesh may be applied in a la
35、titudinal orlongitudinal mesh pattern, or a combination to give theoptimum point spacing over the component. The measureddata points may be extended below the equator to ensure thatthe whole wear scar is captured in the measurement.NOTE 3The 0.5 mm mesh spacing is based on minimizing the errorsof ca
36、lculating the wear volume when using a simple linear “triangulation”integration method to calculate the wear volume (5). A larger pointspacing may be used if a sensitivity analysis is carried out to investigatethe effect of mesh spacing on the wear depth and volume, and the valuescan be shown to con
37、verge.6. Analysis of CMM Measurements6.1 Fit the assumed unworn shape of the component.Published studies have used ellipsoids, spheres or nurbsprofiles (6-13) to represent the unworn (but possible deformed)shape of the hip component. The assumed unworn shapeshould be fitted to the measured data poin
38、ts in the unwornregions, excluding the data points that are within the wornregion. Several of the published methods use a two stage or aniterative process to fit the surface and exclude worn regionsfrom the surface fit (6-13).NOTE 4ASTM F2033 specifies that the maximum departure fromroundness for me
39、tallic components shall not be greater than 5 m for theacetabular component and 5 m for the femoral component using a leastsquares or Minimum Zone Centre Method. Due to these deviations, andpossible deformation during implantation or revision procedures, fitting asphere to the unworn data points mig
40、ht result in significant errors in thecalculated wear values. In some cases, ellipsoids and other shapes havebeen shown to better represent the unworn shape of MoM hip componentsthan a simple sphere (10).6.2 Check the fit of the assumed unworn shape by calculat-ing the Root Mean Square (RMS) error b
41、etween the assumedunworn shape and the measured data points in the unwornregion of the hip component (9). If the calculated RMS errorexceeds 2 m, the fit and the assumed shape shall be modifiedto reduce the error.6.3 Visually check the fit of the assumed unworn shape bylooking at a graphical illustr
42、ation of the deviations from theassumed unworn shape in the unworn regions of the compo-nent. The color scale should be set to optimize these deviations,not the appearance of the worn regions.6.4 If the wear area is not wholly captured within themeasurement region and extends below the equator of th
43、e headthen the measurement shall be repeated to include the wholearea of the wear area.6.5 The maximum depth of wear shall be taken as themaximum deviation between a point on the measured wornsurface and a point on the assumed unworn articular surfacealong a line normal to the assumed unworn articul
44、ar surface.6.6 Use a numerical method to calculate the wear volumeover the worn regions of the component by calculating thevolume between the assumed unworn shape of the componentand the worn region.NOTE 5Differences in algorithms used to calculate the wear volumemay result in variations in the wear
45、 volumes. Scratching, indentations anddeformation attributed to the explantation process and/or handling afterFIG. 2 Schematic Diagram Showing Pattern of Data Points for CMM Measurement of the Acetabular CupF2979 143explantation should not be included in the wear depth and volumeestimates.6.7 The me
46、asurement method and analysis algorithm usedshould be described in detail in the report and suitablyvalidated. Suitable validation methods may include the mea-surement of a reference sphere (14), calculation of the wearfrom “ideal” datasets with mathematically generated wearscars, comparison of grav
47、imetric and calculated dimensionalwear for simulator (components tested in a hip simulator) andartificially (components with material removed to represent awear scar) worn components (10, 11, 14).6.8 If the time implanted is known (whole years anddecimal fraction), the calculate the wear rate by div
48、iding thewear depth or wear volume by the time implanted to give thewear rate (m/year) and the volumetric wear rate (mm3/year)for the head and cup.7. Measurement and Analysis of Components Using aRoundness Machine7.1 Measurement of Acetabular Cup7.1.1 Cup Circumferential Measurement:7.1.1.1 Calibrat
49、e the radial position of the roundness ma-chine radial arm so that the machine gives absolute measure-ment values.7.1.1.2 Align the cup revolution axis with the spindle axis ofrotation of the roundness machine and the cup rim planeperpendicular to the spindle axis of rotation using automaticcentering and leveling routines. Set the vertical height datum atthe cup rim. Nondestructively mark the retrieved component,or identify a landmark feature to provide an angular referencearound the axis of rotational symmetry.7.1.1.3 Measure a series of circumferent
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