1、Designation: F2502 05 (Reapproved 2009)1Standard Specification and Test Methods forBioabsorbable 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 t
2、he 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.1NOTEEditorial changes were made throughout in December 2009.1. Scope1.1 This specification and t
3、est methods covers a mechanicalcharacterization reference for hydrolytically degradable poly-mer resin (from this point on referenced as “bioabsorbable”)plates and screws for orthopedic internal fixation.1.2 This specification establishes a common terminology todescribe the size and other physical c
4、haracteristics of bioab-sorbable implants and performance definitions related to theperformance of bioabsorbable devices.1.3 This specification establishes standard test methods toconsistently measure performance-related mechanical charac-teristics of bioabsorbable devices when tested under definedc
5、onditions of pretreatment, temperature, humidity, and testingmachine speed.1.4 This specification may not be appropriate for all bioab-sorbable devices. The user is cautioned to consider the appro-priateness of the standard in view of the particular bioabsorb-able device and its potential applicatio
6、n.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 use. It is theresponsibility of the user of this standard to establish ap
7、pro-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 Plastics and Electrical Insulating MaterialsE4 Practices for Force Verific
8、ation 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 Terminology Relating to Fatigue and Fracture Test-ingF116 Specification for Medica
9、l 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 InstrumentsF1635 Test Method for in vitro Degradation Testing ofHydrolytically Degradable Pol
10、ymer Resins and FabricatedForms for Surgical ImplantsF1839 Specification for 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:3
11、ISO 13781 Poly (L-Lactide) Resins and Fabricated Formsfor Surgical ImplantsIn Vitro Degradation TestingISO 14630 Non-Active Surgical ImplantsGeneral Re-quirementsISO 15814 Copolymers and Blends Based onPolylactideIn Vitro Degradation Testing3. Terminology3.1 Definitions:3.1.1 Unless otherwise define
12、d in this specification, theterminology related to mechanical testing that is used in thesetest methods will be in accordance with the definitions ofTerminologies E6 and E1823, and Specifications F382 andF543.1This specification and test methods is under the jurisdiction of ASTMCommittee F04 on Medi
13、cal and Surgical Materials and Devices and is the directresponsibility of Subcommittee F04.21 on Osteosynthesis.Current edition approved Aug. 1, 2009. Published December 2009. Originallyapproved in 2005. Last previous edition approved in 2005 as F2502 05. DOI:10.1520/F2502-05R09.2For referenced ASTM
14、 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.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th
15、Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2 General Definitions:3.2.1 bioabsorbable devicea class of implants that aredesigned to deteriorate by means of biological resorption onc
16、ethey are implanted into the body.3.2.2 biological resorptionprocess by which degradedbiomaterials (that is, products of degradation) are eliminated orincorporated, or both, by means of physiological metabolicroutes.3.2.3 deterioration (of a bioabsorbable device)the actionor process that results in
17、a reduction of mass or mechanicalperformance properties, or both.3.2.4 hydrolytically degradable polymer (HDP)any poly-meric material in which the primary mechanism of chemicaldegradation in the body is by hydrolysis (water reacting withthe polymer resulting in cleavage of the chain).3.3 Definitions
18、 for Apparatus:3.3.1 data acquisition devicethe data recorder shall besuitable to continuously record torque versus angle of rotation,as well as linear displacement, calibrated in units of Newton-metres for torque and degrees for angle of rotation. The valueof torque shall have a resolution of at le
19、ast 5 % of torsionalyield strength. The angular displacement scale shall have aminimum sensitivity so as to enable an accurate offset mea-surement capability for a 2 angular displacement (seeA1.5.3).3.3.2 pilot holes in test blockpilot holes shall be drilled inthe test block for insertion and remova
20、l of the test specimen.See Specification F543, Annex 2.3.3.3 test blockthe test block shall be fabricated from auniform material that conforms to Specification F1839. SeeSpecification F543, Annex 2.3.3.4 testing fixturethe torsion testing apparatus that is tobe used for applying the required torque
21、to the specimen shallbe calibrated for the range of torques and rotational displace-ments used in the determination. A suitable testing fixture forthe torsional yield strength-maximum torque-breaking angletest is illustrated in Fig. A1.1.3.3.5 test specimenthe test specimen shall be a com-pletely fa
22、bricated and finished bioabsorbable bone screw.3.3.6 torque transducera transducer to translate the ap-plied torque into an electrical signal amenable to continuousrecording, calibrated over the range of torques, both in theclockwise and counterclockwise rotation, to be encountered inthe test method
23、, shall be provided.3.3.7 torsional displacement transducera transducer totranslate the angle of twist into an electrical signal amenable tocontinuous recording, calibrated over the range of angles to beencountered in the test and an accuracy of 61 % of reading,both in the clockwise and counterclock
24、wise rotation, shall beused.3.4 Definitions for Screw Testing:3.4.1 anchora bioabsorbable device or a component of abioabsorbable device that provides the attachment to the bone.3.4.2 bone anchora bioabsorbable device that provides ameans to attach soft tissue to bone with a suture.3.4.3 insertion d
25、epth (mm)the linear advancement of thebioabsorbable device into the test block measured relative to itsseated position at the test blocks surface prior to testing.3.5 Definitions for Plate Testing:3.5.1 bone platea device with two or more holes or slots,or both, and a cross section that consists of
26、at least twodimensions (width and thickness), which generally are not thesame in magnitude. The device is intended to provide align-ment and fixation of two or more bone sections, primarily byspanning the fracture or defect.3.5.2 bone plate length, L (mm)the linear dimension ofthe bone plate measure
27、d along the longitudinal axis as illus-trated in Fig. A4.2.3.5.3 bone plate thickness, b (mm)the linear dimension ofthe bone plate measured parallel to the screw hole axis asshown in Fig. A4.2. For a bone plate with a crescent section,the thickness is measured at the thickest point along thesection.
28、3.5.4 bone plate width, w (mm)the linear dimension of thebone plate measured perpendicular to both the length andthickness axes as shown in Fig. A4.2.4. Significance and Use4.1 Biodegradable devices are expected by intention todeteriorate over time once they are implanted into the body.This makes a
29、removal operation unnecessary, which is espe-cially advantageous especially for pediatric patients.4.2 While the polymer degrades due to hydrolytic reactionwith the environment, the mechanical performance of thedevice also deteriorates. The key to developing effectivefracture fixation systems based
30、on biodegradable devices is toprovide an adequate level of fixation strength for a time framethat exceeds that expected for fracture healing. Once thefracture is healed, the device can be completely resorbed by thebody.4.3 Generally, biodegradable devices will be tested with testmethods that are sim
31、ilar to those used to evaluate conventionalmetallic devices. In addition, one has to take into considerationthe pre-test conditioning requirements, handling requirements,and time-dependent mechanical property evaluations for bio-degradable devices.5. Materials and Manufacture5.1 Bioabsorbable device
32、s may be fabricated from one ofthe following 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, andSpecification F1925.)5.2 The manufacturer is responsible to ensure that
33、materialsused to manufacture bioabsorbable implants are suitable forFIG. 1 Screw ParametersF2502 05 (2009)12implanting into the body. Methods to evaluate a materialssuitability are described in ISO 14630.5.3 All bioabsorbable devices made of materials that havean ASTM committee F04 or D20 standard d
34、esignation or anISO designation shall meet those requirements given in theASTM standards.5.4 Soaking SolutionA phosphate buffered saline (PBS)solution 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
35、, if need be,the solution should be changed periodically in order to main-tain the pH within the acceptable limits.5.4.1 Other physiologic solutions may be substituted pro-vided the solution is properly buffered. An anti-microbialadditive should be used to inhibit the growth of microorgan-isms in th
36、e solution during the test period. The investigatormust demonstrate that the chosen antimicrobial does not affectthe degradation rate (see X1.3).5.5 Sample ContainerA self-enclosed container capableof holding the test sample and the solution (see X1.4). Multiplesamples may be stored in the same cont
37、ainer provided thatsuitable sample separation is maintained to allow fluid accessto each sample surface and to preclude sample-to-samplecontact. Each container shall be sealable against solution lossdue to evaporation.5.6 Constant Temperature Bath or OvenAn aqueous bathor heated air oven capable of
38、maintaining the samples andcontainers at physiologic temperatures (37 6 2C) for thespecified testing periods.5.7 pH MeterA pH metering device sensitive in thephysiological range (pH 6 to pH 8) with a precision of 0.02 orbetter.5.8 BalanceAcalibrated weighing device capable of mea-suring the weight o
39、f a sample to a precision of 0.1 % of itsinitial weight.6. Conditioning6.1 ConditioningCondition the test specimens in a suit-able solution (for example, PBS solution) and temperature untilit is time to be tested. Remove them from the solution and wipeoff excess solution. The specimens shall be test
40、ed within1hofrinsing (see Test Method F1635). In addition to conditioningthe test specimen in suitable solutions, if the test specimen isintended for use in a loaded physiological condition, it may beimportant to address the additional influence of conditioningstatic or fatigue loads, or both, on th
41、e deterioration of the testspecimen. Conditioning loads that are representative of antici-pated physiological conditions should be chosen.6.1.1 Test ConditionsConduct tests at 23 6 2C and 50 65 % relative humidity, unless otherwise specified. (Removefrom solution, wipe excess fluid, and test within1
42、hofremoval.)7. Care and Handling7.1 Bioabsorbable devices should be cared for and handledin accordance with Practice F565, as appropriate.8. Performance Requirements8.1 Factors considered being important, but for whichvalues and test methods have not been established, are shearstrength of the head o
43、f a screw, shear strength of the threadedregion of a screw, and enzymatically degradable polymerresins.9. Driving Instruments9.1 Specification F116 provides related dimensional infor-mation for several types of medical screwdrivers.10. General Requirements and PerformanceConsiderations10.1 The follo
44、wing properties may be important whendetermining the suitability of a screw for a particular applica-tion. However, the test methods referenced as follows may notbe appropriate for all types of implant applications. The user iscautioned to consider the appropriateness of the test methods inview of t
45、he devices being tested and their potential application.10.1.1 Offset Yield Strength is the stress at which thestress-strain curve departs from linearity by a specified percentof deformation (offset).10.1.2 Torsional Strength is an important parameter toprevent screw breakage during insertion. The t
46、orsional strengthshall be determined using the test methods described in AnnexA1.10.1.3 Axial Pullout Strength is an important parameter ifthe screw is subjected to axial tensile forces, or if the screw isfixed into poor quality or osteoporotic bone. The pulloutstrength may be determined using the t
47、est methods described inAnnex A3.10.1.4 Insertion Torque is an important parameter 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
48、 the appropriate screwdriver bit. Theinsertion torque may be determined using the test methodsdescribed in Annex A2.10.1.5 Geometric ConsiderationsBone plates that are in-tended to be used with bone screws shall have design features(screw holes or slots) that conform to or appropriately fit thecorre
49、sponding bone screw.10.1.6 Bending PropertiesThe bending properties arecritical characteristics of bone plates for orthopedic applica-tions since the bone plate provides the primary means ofstabilizing the bone fragments. Additionally, the bendingstiffness of the bone plate may directly affect the rate andability of healing.10.1.6.1 The relevant bending properties (bending stiffness,bending structural stiffness, and bending strength) shall bedetermined using the standard test method of Annex A4.11. Keywords11.1 bend testing; bone plates; bone
