ASTM F1408-20a

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Designation: F1408 − 20 F1408 − 20a
Standard Practice for
Subcutaneous Screening Test for Implant Materials
This standard is issued under the fixed designation F1408; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers a short-term testing method to screen the subcutaneous tissue reaction to implant candidate materials in
small laboratory animals. The material may be dense or porous. This method may not work for absorbable materials, depending
on the absorption kinetics. The tissue reactions will be evaluated in comparison to those evoked by control materials that are
accepted as clinical implant materials.
1.2 This practice, along with other appropriate biological tests (including other ASTM test methods), may be used to assess the
biocompatibility of candidate materials for use in the fabrication of devices for clinical application. It may be also be applied to
evaluate the effect of special surface textures and preparations of known materials.
1.3 This practice does not provide a comprehensive assessment of the systemic toxicity, carcinogenicity, teratogenicity, or
mutagenicity of the material. Additional information may be needed on the material in its final finished form, such as implantation
assessment at the clinically relevant location.
1.4 The values stated in SI units, including units officially accepted for use with SI, are to be regarded as standard. No other
systems of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
F67 Specification for Unalloyed Titanium, for Surgical Implant Applications (UNS R50250, UNS R50400, UNS R50550, UNS
R50700)
F75 Specification for Cobalt-28 Chromium-6 Molybdenum Alloy Castings and Casting Alloy for Surgical Implants (UNS
R30075)
F86 Practice for Surface Preparation and Marking of Metallic Surgical Implants
This practice is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee F04.16
on Biocompatibility Test Methods.
Current edition approved June 1, 2020Aug. 1, 2020. Published August 2020. Originally approved in 1992. Last previous edition approved in 20132020 as F1408 – 97
(2013).F1408 – 20. DOI: 10.1520/F1408-20.10.1520/F1408-20A.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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F1408 − 20a
F136 Specification for Wrought Titanium-6Aluminum-4Vanadium ELI (Extra Low Interstitial) Alloy for Surgical Implant
Applications (UNS R56401)
F138 Specification for Wrought 18Chromium-14Nickel-2.5Molybdenum Stainless Steel Bar and Wire for Surgical Implants
(UNS S31673)
F648 Specification for Ultra-High-Molecular-Weight Polyethylene Powder and Fabricated Form for Surgical Implants
F763 Practice for Short-Term Screening of Implant Materials
F981 Practice for Assessment of Compatibility of Biomaterials for Surgical Implants with Respect to Effect of Materials on
Muscle and Insertion into Bone
2.2 ISO Standard:
ISO 10993-6:2016 Biological Evaluation of Medical Devices—Part 6: Tests for Local Effects After Implantation
3. Summary of Practice
3.1 Under strict aseptic conditions, test or control samples are implanted subcutaneously along as close as and, if possible, in
parallel to the dorsal midline at the level of the cervical or thoracic vertebravertebrae of an anesthetized animal. The size of the
implant should not impede the normal movement of the animal. After one, four, and nine to twelve weeks the animals are
euthanized, and a comprehensive necropsy is performed. The samples are excised with an intact tissue envelope for histological
evaluation. The tissue response to the test sample is compared to the response of the control material.
4. Significance and Use
4.1 This practice is a guideline for a short-term screening test for the evaluation of the tissue response to materials that may be
selected for implantation in the human body and should be done in accordance with good laboratory practices. This test may be
performed prior to long-term testing (for example, Practice F981) to eliminate unsuitable candidate materials early and to avoid
unnecessary animal testing.
4.2 This practice may be used to detect toxic effects of materials in general (see Appendix X1). However, it is particularly suitable
for the testing of materials that are intended to have contact with subcutaneous tissues or soft tissues in general. For materials
intended to be inserted specifically into muscle tissues, Practice F763 should be considered as a short-term test method.
4.3 The suggested implant specimens are cylindrical. A special grooved type of cylinder may be used (see Fig. X2.1 of Appendix
X2) to allow tissue interlocking that could keep the implant in place and minimize tissue irritation through motion at the interface
that otherwise could contribute to increased variance of the results. In case ungrooved cylinders are used (see Fig. X1.2 of
Appendix X2), probable motion at the implant/tissue interface must be taken into account. Control cylinders should be shaped like
the test cylinders.
4.4 The type of surface preparation of the specimens can affect the tissue reaction; therefore the preparation procedure should be
noted in the report. The test may be used to compare the effect of different surface structures or conditions of the same material
or to assess the effect of various treatments of modifications of a material.
NOTE 1—If this method is used for material research, testing for endotoxin prior to implantation should be considered.
5. Test Animals and Sites
5.1 Laboratory mice (for example, C57BL/6, BALB/c) are used. The test may be adapted to other suitable test animals (for
example, rats). Both sexes should be represented unless otherwise justified (for example, with evidence that one sex is more
sensitive). Institutional and government animal use and care policies and regulations shall be followed.
5.2 The implant specimens are inserted subcutaneously in the neck of the host.
5.2 In mice, the implant specimens are inserted subcutaneously in the neck. One implant (either test or control) is inserted per
mouse. Therefore, the number of animals is identical with the number of implants.
Available from International Organization for Standardization (ISO), ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Switzerland, http://www.iso.org.
F1408 − 20a
5.3 If rats or other larger suitable animals are used, more than one implant may be inserted per animal, but the implants should
never be allowed to come in contact with each other. If this is the case, cylinders of the test and control material may be implanted
separately on the right and the left side of the neck as close as and, if possible, in parallel to the dorsal midline at the level of the
cervical or thoracic vertebrae in a single animal. However, insertion of test and control implants in the same animal may prevent
analysis of systemic toxicity.
6. Implant Specimens
6.1 Specimen Design—Cylinders of 7 mm length and 4 mm diameter are prepared for implantation in mice. Special specimens
with two grooves are designed corresponding to the figures in Appendix X2. If larger animal hosts are used, the implant dimensions
may be increased proportionally. If it is impossible to prepare specimens of this kind, the specimen configuration used must be
described fully in the report. Implant specimens from the candidate and control material should always have the same dimensions.
Control articles with a clinically established acceptable biocompatibility response should be matched as closely as reasonably
possible for significant physical characteristics such as surface features (for example, smooth solid sheet versus highly porous
mesh, presence of surface finish, etc.).
6.2 Selection of Control Materials—Recommended metals for use as control materials include those given in Specifications F67,
F75, F136, and F138. However, for specific applications, any metal of known compatibility and standardized as implant material
may be employed as a control material for comparison. To study adverse tissue reactions, a non-compatible material like copper
may be used as a positive control material. A suitable polymeric control material like the polyethylene USP negative control plastic,
Referenced Standard (RS), or ultrahigh molecular weight polyethylene (see Specification F648) may be used.
6.3 Specimen Surface—The surface of specimens from prospective implant materials should be treated in the same manner as the
implant intended for clinical application in the human patient. Depending on the objective of the test, the control specimens should
have either a surface condition as it is normally used for clinical applications or a surface condition most similar to that of the test
material. For preparation of metallic materials, Practice F86 should be considered.
6.4 Numbers of Test and Control Implants—Per each time period, at least six implant specimens of each candidate and control
material should be evaluated in mice (one per mouse). If more than one specimen is implanted in larger (non-mouse) test hosts,
at least four animals should be used per material and time period.
6.5 Conditioning—The cleaning, sterilization, and packaging should be the same as used for implantation in the human patient.
After surface preparation and sterilization, the implant specimens should be protected from surface alterations and contamination
and should be handled with non-metallic forceps when appropriate. When plastic forceps are used, be sure that no plastic material
is transferred to the implant surface.
7. Procedure
7.1 Implantation:
7.1.1 Implant the specimens under sterile conditions in anesthetized animals. The incision site is shall be remote from the
implantation site to prevent infection around the implant. In mice, make a 1 cm long incision on the dorsal midline
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