1、Designation: F2102 13Standard Guide forEvaluating the Extent of Oxidation in PolyethyleneFabricated Forms Intended for Surgical Implants1This standard is issued under the fixed designation F2102; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、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 covers a method for the measurement of therelative extent of oxidation present in
3、HDPE homopolymersand ultra-high-molecular-weight polyethylene (UHMWPE) in-tended for use in medical implants. The material is analyzed byinfrared spectroscopy. The intensity (area) of the carbonylabsorptions (C=O) centered near 1720 cm-1is related to theamount of chemically bound oxygen present in t
4、he material.Other forms of chemically bound oxygen (C-O-C, C-O-O-C,C-O-H, and so forth) are not captured by this guide.1.2 Although this guide may give the investigator a meansto compare the relative extent of carbonyl oxidation present invarious UHMWPE samples, it is recognized that other forms ofc
5、hemically bound oxygen may be important contributors tothese materials characteristics.1.3 The applicability of the infrared method has beendemonstrated by many literature reports. This particularmethod, using the intensity (area) of the C-H absorptioncentered near 1370 cm-1to normalize for the samp
6、lesthickness, has been validated by an Interlaboratory Study (ILS)conducted according to Practice E691.1.4 The following precautionary caveat pertains only to thetest method portion, Section 5, of this specification: Thisstandard may involve hazardous materials, operations, andequipment. This standa
7、rd 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 requirements prior to use.2. Referenced Documents2.1 AS
8、TM Standards:2E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 bulk oxidation index (BOI)a samples bulk oxida-tion index (BOI) is the average of the oxidation indicescollected over a 500-m section at the center of the
9、 sample.3.1.1.1 DiscussionTypically, this is a plateau region withthe smallest oxidation indices.3.1.1.2 DiscussionFor samples less than about 8 to 10 mmthick, this central region may display the samples highestoxidation indices, depending on its state of oxidation.3.1.2 depth locator (DL)a measurem
10、ent of the distancefrom the articular surface, or surface of interest, that a spectrumwas collected and a corresponding OI calculated.3.1.3 oxidation index (OI)an oxidation index (OI) isdefined as the ratio of the area of the carbonyl absorptionpeak(s) centered near 1720 cm-1to the area of the absor
11、ptionpeak(s) centered near 1370 cm-1, as shown in Fig. 1. Note thatthe peak areas are computed after subtracting out the appro-priate baseline, as further discussed in Section 6.3.1.4 oxidation index profilean oxidation index profile isthe graphical representation of variation of the samplesoxidatio
12、n index with distance from its articular surface or thesurface of interest. This is a plot of an OI versus DL. Typically,the graph will show the profile through the entire thickness ofthe sample.3.1.5 surface oxidation index (SOI)a samples surfaceoxidation index (SOI) is the average of the oxidation
13、 indicesfrom the samples articular surface, or the surface of interest, toa depth of 3-mm subsurface.4. Apparatus4.1 Infrared Spectrometer:4.1.1 A calibrated infrared spectrometer capable of record-ing a transmission absorption spectrum over the range of about1200 to about 2000 cm-1using about 200-s
14、m-thick films at aresolution of 4 cm-1and an aperture of about 200 by 200 m.4.1.1.1 Other modes of collection (that is, percent reflection,attenuated total reflection (ATR), and so forth) and apertureand increment sizes may be used to generate the samples1This guide is under the jurisdiction of ASTM
15、 Committee F04 on Medical andSurgical Materials and Devicesand is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved Nov. 1, 2013. Published December 2013. Originallyapproved in 2001. Last previous edition approved in 2006 as F2102 061. DOI:10.1520/F210
16、2-13.2For 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
17、Box C700, West Conshohocken, PA 19428-2959. United States1absorption spectrum provided they can be demonstrated toproduce equivalent results. Too large an aperture can result ina loss of profile accuracy.4.1.1.2 When a Fourier Transform Infrared (FTIR) spec-trometer is used, a minimum of 32 scans sh
18、all be collected perspectrum.4.1.1.3 The FTIR instrument and sample compartment maybe purged with a moisture-free inert gas (for example, nitrogen,helium, or argon) to minimize spectral interference from thesecomponents.4.2 Specimen HolderEquipment capable of accuratelypositioning the sample under t
19、he orifice in increments at thescale of the aperture dimensions.4.3 MicrotomeEquipment capable of producing about200-m-thick slices (films) of a sample perpendicular to thearticular surface or the surface of interest.5. Procedure5.1 Preparation of the Infrared Spectrometer:5.1.1 Prepare the infrared
20、 spectrometer for collection of atransmission absorption spectrum from a thin film of theUHMWPE sample according to the manufacturers recommen-dations and the conditions described in Section 4 above.5.1.2 Collect the sequence of spectra per 5.2 and 5.3.5.2 Preparation of the Test Specimen:5.2.1 Usin
21、g a microtome, or other appropriate device, pre-pare a thin slice of the sample about 200 m thick.5.2.2 The slice shall be taken near the center of the samplesarticular surface or the surface of interest.5.2.3 The orientation of the slice shall typically be perpen-dicular to the articular surface or
22、 the surface of interest.5.2.4 For explanted components retrieved after in vivo useor in vitro samples that have been exposed to lipids (forexample, simulator specimens exposed to lubricants containingserum), the film should be submerged in a reagent (heptane orhexane) to extract lipids from the pol
23、ymer that interfere withthe carbonyl peak absorptions. The extraction technique shouldbe verified to confirm that the oxidation level has stabilized.5.3 Configuration of the Test Specimen in the Spectrometer:5.3.1 The test film (slice) shall be first configured in thespectrometer (after an appropria
24、te background spectrum hasbeen collected) such that the aperture is positioned over thefirst 200 m of the film starting at the surface of interest.5.3.2 Subsequent spectra shall be collected sequentially atincrements matching the aperture size (that is, about 200 m)from the articular surface, or sur
25、face of interest, across thewidth of the film to the opposite surface.5.3.2.1 Larger increments may be used; however, too largean increment size may result in a loss of profile accuracy.6. Calculations6.1 Oxidation Peak Area (OA):6.1.1 For each absorbance spectrum, calculate the total areaof the car
26、bonyl peak absorptions centered near 1720 cm-1(Fig.1).6.1.1.1 This is the area below the samples carbonyl absorp-tion curve and above the straight line baseline drawn betweenthe starting and ending points.6.2 Normalization Peak Area (ON):6.2.1 For each absorbance spectrum, calculate the total areaof
27、 the peak absorptions centered near 1370 cm-1(Fig. 1).6.2.1.1 This is the area below the samples absorption curveand above the straight line baseline drawn between the samestarting and ending points.6.3 Oxidation Index (OI):6.3.1 For each absorbance spectrum, calculate its OI bydividing the area of
28、its oxidation peak (6.1) by the area of itsnormalization peak (6.2), as shown in Fig. 1.6.4 Oxidation Index Depth Locator (DL):6.4.1 Calculate the distance from the articular surface, orsurface of interest (DL), for each spectrum and its correspond-ing OI from the following equation.DL 5 0.5A!1nS!FI
29、G. 1 Typical FTIR Spectra of Oxidized UHMWPE, Showing theDefinition of an Area-Based Oxidation Index Based on Normaliza-tion Using the 1370-cm-1PeakFIG. 2 FTIR Spectra Showing the Carbonyl Absorption BandsNOTE 1Note that both reagents effectively extracted the lipids (thelipid absorption peak is cen
30、tered at approximately 1740 cm-1). The tibialinsert was fabricated from highly crosslinked and remelted UHMWPEfollowed by terminal sterilization in EtO gas (Ref. 1).F2102 132where:A = the size of the aperture in micrometres in the stepdirection,n = the number of steps (increments) the aperture had b
31、eenmoved from its initial location at the articular surface orsurface of interest, andS = the step (increment) size in micrometres.6.5 Samples Oxidation Index ProfileConstruct a plot of asamples oxidation indices (OI) versus the corresponding depthlocators (DLs).6.6 Surface Oxidation Index (SOI)Calc
32、ulate a samplesSOI by calculating the average of the samples oxidationindices (OI) with depth locator (DL) values between 0 and3000.6.7 Bulk Oxidation Index (BOI)Calculate a samples BOIby calculating the average of the samples oxidation indices(OIs) corresponding to the center 500 mm of material.6.8
33、 Maximum Oxidation Index (MOI)Calculate the sam-ples MOI index observed between depth locator (DL) valuesof 0 and 3000.7. Report7.1 The report shall contain at least the following experi-mental details and results:7.1.1 Material Information:7.1.1.1 Resin type and resin lot number.7.1.1.2 Consolidati
34、on method and manufacturer and manu-facturer lot number.7.1.1.3 Any special post-consolidation treatments, forexample, shot isostatic pressing (HIPing), annealing,sterilization, cross-linking, stabilization, accelerated aging, andstorage conditions.7.1.2 Sample Information:7.1.2.1 Orthopedic implant
35、 or laboratory test specimen.7.1.2.2 Time elapsed between sample preparation and test-ing in the FTIR.7.1.2.3 Articular surface or non-articulator surface.7.1.2.4 Test samples original dimensions.7.1.2.5 Any special post-treatments of the original testsample, for example, annealing, sterilization, c
36、ross-linking,stabilization, accelerated aging, and storage conditions.7.1.2.6 Test film thickness and total width.7.1.2.7 Any special post-treatments of the test films, forexample, annealing, sterilization, cross-linking, stabilization,accelerated aging, and storage condition.7.1.2.8 Describe sample
37、 fixturing (for example, pressedbetween KBr plates).7.1.3 Spectrometer Information:7.1.3.1 Manufacturer and model number.7.1.3.2 Analogue or Fourier Transform spectrometer.7.1.3.3 Aperture dimensions, profile step size, spectralresolution, and number of scans per spectrum.7.1.4 Data Analysis Informa
38、tion:7.1.4.1 Manual or by spectrometers software algorithms.7.1.4.2 Calculated SOI, BOI, and MOI.7.1.4.3 Calculated SOI, BOI, and MOI values of less than 0reflect noise or uncertainty in the baseline and shall be assigneda value of 0. The rationale for this interpretation of very lowoxidation values
39、 is discussed in X1.10.8. Precision and Bias8.1 PrecisionThe data in Table 1 is based on a series ofinternational interlaboratory studies using this method whichwere conducted in 1999 and 2000, in accordance with PracticeE691, involving up to twelve institutions across the UnitedStates and Europe. M
40、etrics of repeatability and reproducibilitybetween different institutions were calculated as outlined inPractice E691 and normalized with respect to the meanoxidation index to estimate relative uncertainty. The data forthe GUR 4150 HP rod stock were collected on as-irradiatedmicrotomed samples. For
41、the long-term shelf-aged tibialimplants, the data were collected below the surface at thelocation of maximum oxidation. All samples were 200-m-thick microtomed films gamma irradiated in air.8.2 BiasNo statement may be made about the bias of thistest method, as there is no standard reference material
42、 orreference test method that is applicable.9. Keywords9.1 FTIR; implant; oxidation; oxidation index; UHMWPEAPPENDIXTABLE 1 International Interlaboratory Study Test ResultsUHMWPE Resin,Component TypeShelf Age,Average OxidationIndex (OI),Absolute UncertaintyStandardRelative Uncertaintyyears x sxsrsRs
43、r,% sR,%GUR 4150 HP, rodstock0.0 0.232 0.077 0.017 0.078 7.2 33.8GUR 1120, tibialinsert5.3 1.28 0.138 0.040 0.142 3.1 11.1GUR 1120, tibialinsert7.5 4.51 0.823 0.168 0.834 3.7 18.5GUR 1120, tibialinsert11.5 4.53 0.823 0.483 0.912 10.7 20.2F2102 133(Nonmandatory Information)X1. RATIONALEX1.1 The exten
44、t of overall oxidation and specifically certainoxidation index profiles present in orthopaedic implant com-ponents made of UHMWPE have been shown to degrade theirmechanical properties and thus potentially adversely affecttheir in vivo performance. It is, therefore, important to havestandard methods
45、for assessing the oxidative characteristics ofsuch materials.X1.2 The method described herein is an adaptation ofseveral similar methods described in the literature. The par-ticular technique used to calculate an oxidation index used herehas been validated by interlaboratory studies per PracticeE691
46、.X1.3 For samples that are significantly oxidized, theircarbonyl absorption peak(s) is typically very intense and broad.For such samples, a starting and ending wavenumber for theabsorption peak(s) and its baseline may be as wide as 1650cm-1to 1850 cm-1. For samples displaying very small levels ofoxi
47、dation, their carbonyl absorption peak(s) is typically veryweak and narrow in comparison to highly oxidized samples.For such samples, a starting and ending wavenumber for theabsorption peak(s) and its baseline may be closer to 1680 cm-1to 1765 cm-1. In any case, one should set the starting andending
48、 points of an absorption peak, and its baseline, to allowthe accurate and precise measurement of its area.X1.4 Although the method described herein has been shownto be useful for comparing the oxidation states of differentUHMWPE samples, it is clear that this method does notaccount for all the diffe
49、rent types of oxidative products presentor potentially important in a sample.X1.5 This method is useful for comparing the oxidationstate of real-time shelf-aged UHMWPE components and UH-MWPE materials assumed to have undergone oxidation via thesame mechanisms.X1.6 This method is also useful for comparing the oxidationstate of retrieved components. It is, however, complicated bythe effects of biological residues potentially present in retrievedsamples. Common methods used to reduce such residuals (forexample, extraction with hexane)
