1、Designation: F 2102 06e1Standard Guide forEvaluating the Extent of Oxidation in Ultra-High-Molecular-Weight Polyethylene Fabricated Forms Intended for SurgicalImplants1This standard is issued under the fixed designation F 2102; the number immediately following the designation indicates the year ofor
2、iginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEParagraphs 7.1.4.2 and 8.1 were editorially corrected in July 2006
3、.1. Scope1.1 This guide covers a method for the measurement of therelative extent of oxidation present in ultra-high-molecular-weight polyethylene (UHMWPE) intended for use in medicalimplants. The material is analyzed by infrared spectroscopy.The intensity (area) of the carbonyl absorptions (C=O)cen
4、tered near 1720 cm-1is related to the amount of chemicallybound oxygen present in the material. Other forms of chemi-cally 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 carbo
5、nyl oxidation present invarious UHMWPE samples, it is recognized that other forms ofchemically 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 i
6、ntensity (area) of the C-H absorptioncentered near 1370 cm-1to normalize for the samples thick-ness, has been validated by an Interlaboratory Study (ILS)conducted according to Practice E 691.1.4 The following precautionary caveat pertains only to thetest method portion, Section 5, of this specificat
7、ion: Thisstandard may involve hazardous materials, operations, andequipment. 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
8、the applica-bility of regulatory requirements prior to use.2. Referenced Documents2.1 ASTM Standards:2E 691 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) i
9、s the average of the oxidation indicescollected over a 500-m section at the center of the 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 10mm thick, this central region may display the samples highest
10、oxidation indices, depending on its state of oxidation.3.1.2 depth locator (DL)a measurement 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 t
11、he area of the carbonyl absorptionpeak(s) centered near 1720 cm-1to the area of the absorptionpeak(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 o
12、xidation index profile isthe graphical representation of variation of the samplesoxidation 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 ox
13、idation index (SOI)a samples surfaceoxidation index (SOI) is the average of the oxidation indicesfrom the samples articular surface, or the surface of interest, toa depth of 3-mm subsurface.1This guide is under the jurisdiction of ASTM Committee F04 on Medical andSurgical Materials and Devices and i
14、s the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved May 1, 2006. Published May 2006. Originallyapproved in 2001. Last previous edition approved in 2001 as F 2102 01e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM
15、Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Apparatus4.1 Infrared Spectr
16、ometer: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-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 refle
17、ction,attenuated total reflection (ATR), and so forth) and apertureand increment sizes may be used to generate the samplesabsorption 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
18、 Infrared (FTIR) spec-trometer is used, a minimum of 32 scans shall be collected perspectrum.4.1.1.3 The FTIR instrument and sample compartmentshould be purged with a moisture- and carbon-dioxide-freeinert gas (for example, nitrogen, helium, or argon) to minimizespectral interference from these comp
19、onents.4.2 Specimen HolderEquipment capable of accuratelypositioning the sample under the 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 inter
20、est.5. Procedure5.1 Preparation of the Infrared Spectrometer:5.1.1 Prepare the infrared 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
21、the sequence of spectra per 5.2 and 5.3.5.2 Preparation of Test Specimen:5.2.1 Using a microtome, or other appropriate device, pre-pare a thin slice of the sample about 200 m thick.5.2.2 The slice shall typically be taken near the center of thesamples articular surface or the surface of interest.5.2
22、.3 The orientation of the slice shall typically be perpen-dicular to the articular surface or the surface of interest.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 appropriate background spectrum hasbeen
23、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 surface of interest, across thewid
24、th 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 carbonyl peak absorptions centered
25、 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 same starting and ending points.6.2 Normalization Peak Area (ON):6.2.1 For each absorbance spectrum, calculate the total areaof the peak absorptions cent
26、ered 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 its oxidation peak (6.1) b
27、y 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! 1 nS!where:A = the size of the
28、aperture in micrometres in the stepdirection,n = the number of steps (increments) the aperture had beenmoved from its initial location at the articular surfaceor surface of interest, andS = the step (increment) size in micrometres.6.5 Samples Oxidation Index ProfileConstruct a plot of asamples oxida
29、tion indices (OI) versus their correspondingdepth locators (DL).6.6 Surface Oxidation Index (SOI)Calculate 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
30、 the average of the samples oxidation indices(OI) corresponding to the center 500 mm of material.6.8 Maximum Oxidation Index (MOI)Calculate the sam-ples MOI index observed between depth locator (DL) values0 and 3000.FIG. 1 Typical FTIR Spectra of Oxidized UHMWPE, Showing theDefinition of an Area-Bas
31、ed Oxidation Index Based onNormalization Using the 1370-cm-1PeakF210206e127. 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 Consolidation method and manufacturer and manu-facturer
32、lot number.7.1.1.3 Any special postconsolidation treatments, for ex-ample, HIPing, annealing, sterilization, cross-linking, stabili-zation, accelerated aging, and storage conditions.7.1.2 Sample Information:7.1.2.1 Orthopedic implant or laboratory test specimen.7.1.2.2 Articular surface or nonarticu
33、lator surface.7.1.2.3 Test samples original dimensions.7.1.2.4 Any special posttreatments of the original testsample, for example, annealing, sterilization, cross-linking,stabilization, accelerated aging, and storage conditions.7.1.2.5 Test film thickness and total width.7.1.2.6 Any special posttrea
34、tments of the test films, forexample, annealing, sterilization, cross-linking, stabilization,accelerated aging, and storage condition.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
35、, spectral reso-lution, and number of scans per spectrum.7.1.4 Data Analysis Information:7.1.4.1 Manual or by spectrometers software algorithms.7.1.4.2 Calculated SOI, BOI, and MOI.8. Precision and Bias8.1 PrecisionThe data in Table 1 is based on a series ofinternational interlaboratory studies usin
36、g this method whichwere conducted in 1999 and 2000, in accordance with PracticeE 691, involving up to twelve institutions across the UnitedStates and Europe. Metrics of repeatability and reproducibilitybetween different institutions were calculated as outlined inPractice E 691 and normalized with re
37、spect to the meanoxidation index to estimate relative uncertainty. The data forthe GUR 4150 HP rod stock were collected on as-irradiatedmicrotomed samples. For the long-term shelf-aged tibial im-plants, the data were collected below the surface at the locationof maximum oxidation. All samples were 2
38、00-m-thick micro-tomed 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 orreference test method that is applicable.9. Keywords9.1 FTIR; implant; oxidation; oxidation index; UHMWPEAPPENDIX(Nonmandatory Informa
39、tion)X1. RATIONALEX1.1 The extent of overall oxidation and specificallycertain oxidation index profiles present in orthopaedic implantcomponents made of UHMWPE have been shown to degradetheir mechanical properties and thus potentially adverselyaffect their in vivo performance. It is, therefore, impo
40、rtant tohave standard methods for assessing the oxidative characteris-tics of such 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 interlab
41、oratory studies per PracticeE 691.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 d
42、isplaying very small levels ofoxidation, 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
43、should set the starting andending 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 beenTABLE 1 International Interlaboratory Study Test ResultsUHMWPE Resin,Component TypeShelf Age,Average OxidationI
44、ndex (OI),Absolute UncertaintyStandardRelative UncertaintyyearsxsxsrsRsr,% 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
45、10.7 20.2F210206e13shown to be useful for comparing the oxidation states ofdifferent UHMWPE samples, it is clear that this method doesnot account for all the different types of oxidative productspresent or potentially important in a sample.X1.5 This method is useful for comparing the oxidationstate
46、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 oxida-tion state of retrieved components. It is, however, complicatedby the effects of biological residues potentially present
47、inretrieved samples. Common methods used to reduce suchresiduals (for example, extraction with hexane) may improvethe comparative power of this technique.X1.7 Use of this method to make comparisons betweenreal-time shelf-aged components, accelerated aged compo-nents, and retrieved components is less
48、 useful because of thepotential for different, and other, modes of oxidizing theUHMWPE in vivo compared to shelf or accelerating aging.X1.8 At the present time, there is no clear correlationbetween the extent of oxidation or the oxidation profile presentin a sample of UHMWPE and its functional chara
49、cteristics.3For this reason, no maximum SOI, MOI, or BOI has beenspecified in this document.BIBLIOGRAPHY(1) Collier, J. P., Sperling, D. K., Currier, J. H., Sutula, L. C., Saum, K.A., et al, “Impact of Gamma Sterilization on Clinical Performanceof Polyethylene in the Knee,” J Arthroplasty, 11, 377-89, 1996.(2) Collier, J. P., Sutula, L. C, Currier, B. H., Currier, J. H., Wooding,R. E., et al, “Overview of Polyethylene as a Bearing Material:Comparison of Sterilization Methods,” Clin Orthop, 333, 76-86,1996.(3) Costa, L. and Brach Del Pre
