1、Designation: F2502 11Standard Specification and Test Methods forAbsorbable Plates and Screws for Internal FixationImplants1This standard is issued under the fixed designation F2502; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he 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 specification and test methods cover the mechani-cal characterization of plates and screws for orthope
3、dic internalfixation. Covered devices are fabricated from one or morehydrolytically degradable polymer (from this point on referredto as “absorbable”) resins or resin composites.1.2 This specification establishes a common terminology todescribe the size and other physical characteristics of absorb-a
4、ble implants and performance definitions related to theperformance of absorbable devices.1.3 This specification establishes standard test methods toconsistently measure performance-related mechanical charac-teristics of absorbable devices when tested under definedconditions of pretreatment, temperat
5、ure, humidity, and testingmachine speed.1.4 This specification may not be appropriate for all absorb-able devices, especially those that possess limited hydrolyticsusceptibility and degrade in vivo primarily through enzymaticaction. The user is cautioned to consider the appropriateness ofthe standar
6、d in view of the particular absorbable device and itspotential application.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its
7、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:2D790 Test Methods for Flexural Properties of Unreinforcedand Reinforced P
8、lastics and Electrical Insulating MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE122 Practice for Calculating Sample Size to Estimate,With Specified Precision, the Average for a Characteristicof a Lot or ProcessE1823 Terminolo
9、gy Relating to Fatigue and Fracture Test-ingF116 Specification for Medical Screwdriver BitsF382 Specification and Test Method for Metallic BonePlatesF543 Specification and Test Methods for Metallic MedicalBone ScrewsF565 Practice for Care and Handling of Orthopedic Im-plants and InstrumentsF1088 Spe
10、cification for Beta-Tricalcium Phosphate for Sur-gical ImplantationF1185 Specification for Composition of Hydroxylapatite forSurgical ImplantsF1635 Test Method for in vitro Degradation Testing ofHydrolytically Degradable Polymer Resins and FabricatedForms for Surgical ImplantsF1839 Specification for
11、 Rigid Polyurethane Foam for Useas a Standard Material for Testing Orthopaedic Devicesand InstrumentsF1925 Specification for Semi-Crystalline Poly(lactide)Polymer and Copolymer Resins for Surgical Implants2.2 ISO Standards:3ISO 13781 Poly (L-Lactide) Resins and Fabricated Formsfor Surgical ImplantsI
12、n Vitro Degradation TestingISO 14630 Non-Active Surgical ImplantsGeneral Re-quirementsISO 15814 Copolymers and Blends Based onPolylactideIn Vitro Degradation Testing3. Terminology3.1 Definitions:1This specification and test methods is under the jurisdiction of ASTMCommittee F04 on Medical and Surgic
13、al Materials and Devices and is the directresponsibility of Subcommittee F04.21 on Osteosynthesis.Current edition approved June 1, 2011. Published July 2011. Originally approvedin 2005. Last previous edition approved in 2009 as F2502 05 (2009)1. DOI:10.1520/F2502-11.2For referenced ASTM standards, v
14、isit 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.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New Yo
15、rk, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.1 Unless otherwise defined in this specification, theterminology related to mechanical testing that is used in thesetest methods will be in accordan
16、ce with the definitions ofTerminologies E6 and E1823, and Specifications F382 andF543.3.2 General Definitions:3.2.1 absorbable, adjin the body, referring to an initiallydistinct foreign material or substance that either directly orthrough intended degradation can pass through or be assimi-lated by c
17、ells and/or tissue.NOTE 1See Appendix X1.5 for a discussion regarding the usage of“absorbable” and other related terms.3.2.2 absorbable compositean absorbable polymer resinor construct incorporating a particulate and/or fibrous bioactiveand/or absorbable filler material.3.2.3 bone anchora device or
18、a component of a devicethat provides the attachment to the bone.3.2.4 bone platea device, when affixed with screws orcerclage wire, intended to provide alignment of two or morebone sections, primarily by spanning the fracture or defect. Abone plate has two or more holes. Its width and thicknessusual
19、ly are not the same in magnitude.3.2.5 deteriorationthe reduction or worsening of me-chanical or other functional performance properties of adevice.3.2.6 hydrolytically degradable polymerany polymericmaterial in which the primary mechanism of chemical degra-dation in the body is by hydrolysis (water
20、 reacting with thepolymer resulting in cleavage of the chain).3.2.7 suture anchora device that provides a means toattach soft tissue to bone with a suture.3.3 Definitions of Terms Specific to This Standard:3.3.1 insertion depth (mm)the linear advancement of adevice into the test block measured relat
21、ive to its seatedposition at the test blocks surface prior to testing.4. Significance and Use4.1 Absorbable devices are intended to degrade and absorbover time once they are implanted into the body. This makes aremoval operation unnecessary, which is especially advanta-geous for pediatric patients.4
22、.2 While the polymer degrades due to hydrolytic reactionwith the environment, the mechanical performance of thedevice also deteriorates. The key to developing mechanicallyeffective fracture fixation systems based on absorbable devicesis to provide an adequate level of fixation strength and stiffness
23、for a time frame that exceeds that expected for fracture healing.Once the fracture is healed, the device can be completelyabsorbed by the body. The biological performance of thedevice, particularly for application at a bony site, may beenhanced by incorporation of bioactive fillers in the polymer.4.
24、3 Absorbable devices will be tested using test methodsthat are similar to those used to evaluate conventional metallicdevices. The pre-test conditioning requirements, handling re-quirements, and time-dependent mechanical property evalua-tions for absorbable devices shall be considered.5. Materials a
25、nd Manufacture5.1 Absorbable devices may be fabricated from one of thefollowing materials:5.1.1 L-lactide, D-lactide, D, L-lactide, glycolide, or otherknown hydrolytically degradable polymer resins or copoly-mers. (See ISO 13781, ISO 15814, Test Method F1635, andSpecifications F1925, F1088, and F118
26、5.)5.2 The manufacturer shall ensure that materials used tomanufacture absorbable implants are suitable for implantinginto the body. Methods to evaluate a materials suitability aredescribed in ISO 14630.5.3 All absorbable devices made of materials that have anASTM committee F04 or D20 standard desig
27、nation or an ISOdesignation shall meet those requirements given in the ASTMstandards.6. General Requirements and PerformanceConsiderations6.1 Absorbable Bone ScrewsThe following propertiesmay be important when determining the suitability of a screwfor a particular application. However, the test meth
28、ods refer-enced as follows may not be appropriate for all types ofimplant applications. The user is cautioned to consider theappropriateness of the test methods in view of the devicesbeing tested and their potential application.6.1.1 Offset Yield Strength is the stress at which the stress-strain cur
29、ve departs from linearity by a specified percent ofdeformation (offset).6.1.2 Torsional Strength is an important parameter to pre-vent screw breakage during insertion. The torsional strengthshall be determined using the test methods described in AnnexA1.6.1.3 Driving Torque is an important parameter
30、 to avoidfailure of the screw during insertion and to ensure that thescrew may be easily inserted by the surgeon. The insertiontorque should be much less than the torsional yield strength ofthe screw as well as that of the appropriate screwdriver bit. Theinsertion torque may be determined using the
31、test methodsdescribed in Annex A2.6.1.4 Axial Pullout Strength is an important parameter if thescrew is subjected to axial tensile forces, or if the screw is fixedinto poor quality or osteoporotic bone. The pullout strengthmay be determined using the test methods described in AnnexA3.6.2 Absorbable
32、Bone Plates:6.2.1 Geometric ConsiderationsBone plates that are in-tended to be used with bone screws shall have design featuresFIG. 1 Screw ParametersF2502 112(screw holes or slots) that conform to or appropriately fit thecorresponding bone screw.6.2.2 Bending PropertiesThe bending properties are cr
33、iti-cal characteristics of bone plates for orthopedic applicationssince the bone plate provides the primary means of stabilizingthe bone fragments. In addition, the bending stiffness of thebone plate may affect the rate and quality of healing.6.2.2.1 The relevant bending properties (bending stiffnes
34、s,bending structural stiffness, and bending strength) shall bedetermined using the standard test method of Annex A4.7. General Sampling, Conditioning, and TestingConsiderations7.1 Apparatus, Equipment, and Materials:7.1.1 Sample ContainerA self-enclosed glass or plasticcontainer capable of holding t
35、he test sample and the condition-ing solution shall be used. The container shall be sealable toprevent solution loss due to evaporation. Multiple samples maybe stored in the same container provided that suitable sampleseparation is maintained to allow fluid access to each samplesurface and to preclu
36、de sample-to-sample contact.7.1.2 Conditioning/Soaking SolutionA phosphate buff-ered saline (PBS) or other adequately pH-controlled aqueoussolution shall be used. The pH of the solution shall bemaintained at 7.4 6 0.2 (see Test Method F1635, SectionX1.3). The pH should be monitored frequently and, i
37、f neces-sary, the solution shall be changed periodically in order tomaintain the pH within the acceptable limits. These materialsmay be hazardous and all persons using them should review thematerial safety data sheet (MSDS) before handling and use allrecommended safety precautions.7.1.2.1 Other phys
38、iologic relevant solutions may be substi-tuted provided the solution is properly buffered. An anti-microbial additive should be used to inhibit the growth ofmicroorganisms in the solution during the test period. Theinvestigator shall demonstrate that the chosen antimicrobialdoes not affect the absor
39、ption rate (see X1.3).7.1.3 Constant Temperature Bath or OvenAn aqueousbath or heated air oven capable of maintaining the samples andcontainers at a physiologic temperature (37 6 2C) for thespecified testing periods shall be used. It shall be well stirredduring the test and shall be provided with a
40、means of raisingthe temperature at a uniform rate.7.1.4 pH MeterA pH metering device sensitive in thephysiological range (pH 6 to pH 8) with a precision of 0.02 orbetter shall be used.7.1.5 BalanceA calibrated weighing device capable ofmeasuring the weight of a sample to a precision of 0.1 % of itsi
41、nitial weight shall be used.7.1.6 Driving InstrumentsSpecification F116 provides re-lated dimensional information for several types of medicalscrewdrivers7.2 Sample Acquisition and Evaluation Frequency:7.2.1 SamplingIf appropriate, representative randomsamples shall be taken from each lot or process
42、ing quantity inaccordance with Practice E122. The test specimen shall be acompletely fabricated and finished absorbable bone screwsterilized as intended by the manufacturer.7.2.2 Conditioning Intervals For a complete history of thebehavior of a sample during absorption, there should be at leastseven
43、 measuring points spanning the duration of mechanicallongevity. For example, 0 h, 1 day, 1 week, 4 weeks, 8 weeks,12 weeks, 16 weeks, and 24 weeks may be appropriate forL-PLA based devices. An initial (0 h) sample is to be testedwithout conditioning, while data acquired at 1 day post-immersion provi
44、des representation of an initial equilibration ofthe sample within the conditioning solution. The testingintervals shall be documented in the test report.7.3 Sample Conditioning:7.3.1 Test specimens shall be conditioned by immersion ina pH-controlled aqueous solution at physiologic temperatures(37 6
45、 2C) for time intervals appropriate for the device(s)being evaluated.7.3.1.1 Conditioning without LoadingThis approach,which omits mechanical loading, is the most common andexposes the sample only to hydrolysis. Such conditioningnecessitates a subsequent test to quantify the impact ofhydrolysis on t
46、he samples mechanical properties.7.3.1.2 Conditioning under Applied LoadIf the device isintended for use in a loaded physiological condition, it isimportant to consider characterization of the influence thatstatic and/or fatigue loading have on the deterioration of thetest specimen. Conditioning loa
47、d types and magnitudes that arerepresentative of anticipated physiological conditions shouldbe used.7.3.2 Conclusion of ConditioningOnce the appropriatethermal conditioning period is complete, the immersed sampleis then removed from the elevated temperature bath. Thethermally conditioned sample is t
48、o remain immersed in theconditioning fluid until mechanical testing is commenced.Testing shall commence within1hofsample retrieval from theelevated temperature bath.7.4 Sample Testing:7.4.1 Care and HandlingCare, handling, and positioningof the absorbable device sample should be conducted inaccordan
49、ce with Practice F565, as appropriate.7.4.2 TimingTesting shall commence within 1 h after thesample container is retrieved from elevated temperature bath.7.4.3 RetrievalTesting is to occur immediately after re-moval of the thermally conditioned sample from the condition-ing solution. Once retrieved, excess fluid shall be removed andthe sample shall be then promptly positioned in accordancewith the specific test method.7.4.4 Room Temperature TestingTesting is to be per-formed at room temperature (23 6 2C). Unless otherwisedeemed relevant, samples
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