ASTM F564-17

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F564 − 10 (Reapproved 2015) F564 − 17
Standard Specification and Test Methods for
Metallic Bone Staples
This standard is issued under the fixed designation F564; 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 specification covers characterization of the design and mechanical function of metallic staples used in the internal
fixation of the muscular skeletal musculoskeletal system. It is not the intention of this specification to describe or specify specific
designs for metallic bone staples.
1.2 This specification includes the following four test methods for measuring mechanical properties of metallic bone staples:
1.2.1 Test Method for Constant Amplitude Bending Fatigue Tests of Metallic Bone Staples—Annex A1.
1.2.2 Test Method for Pull-Out Fixation Strength of Metallic Bone Staples—Annex A2.
1.2.3 Test Method for Soft Tissue Fixation Strength of Metallic Bone Staples—Annex A3.
1.2.4 Test Method for Elastic Static Bending of Metallic Bone Staples—Annex A4.
1.3 The values stated in SI units are to be regarded as standard. NoAny other units of measurement are included in this
standard.standard are shown for reference only.
1.4 Multiple test methods are included in this standard. However, the user is not necessarily obligated to test using all of the
described methods. Instead, the user should only select, with justification, test methods that are appropriate for a particular device
design. This may be only a subset of the herein described test methods.
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 safety, health and healthenvironmental 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:
E4 Practices for Force Verification of Testing Machines
E122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or
Process
E467 Practice for Verification of Constant Amplitude Dynamic Forces in an Axial Fatigue Testing System
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
F382 Specification and Test Method for Metallic Bone Plates
F565 Practice for Care and Handling of Orthopedic Implants and Instruments
F601 Practice for Fluorescent Penetrant Inspection of Metallic Surgical Implants
F629 Practice for Radiography of Cast Metallic Surgical Implants
F2503 Practice for Marking Medical Devices and Other Items for Safety in the Magnetic Resonance Environment
3. Finish
3.1 Staples conforming to this specification shall be finished and identified in accordance with Practice F86, as appropriate.
This specification is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.21 on Osteosynthesis.
Current edition approved March 1, 2015Sept. 1, 2017. Published April 2015October 2017. Originally approved in 1985. Last previous edition approved in 20102015 as
F564 – 10.F564 – 10 (2015). DOI: 10.1520/F0564-10R15.10.1520/F0564-17.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F564 − 17
4. Inspection Practices
4.1 Staples made in accordance with Specification F75 should be inspected in accordance with Practice F601 or X-rayed in
accordance with Practice F629.
5. Care and Handling
5.1 Staples should be cared for and handled in accordance with Practice F565, as appropriate.
5.2 Consider Practice F2503 to identify potential hazards produced by interactions between the device and the MR environment
and for terms that may be used to label the device for safety in the MR environment
6. Materials
6.1 Bone staples shall be fabricated from a metallic material intended for surgical implant applications. In addition, the materials
shall be biocompatible for the intended application. Materials should be chosen based on the design requirements of the particular
device. ASTM subcommittee F04.12 maintains a number of specifications for materials that are suitable for surgical implant
applications.
7. Keywords
7.1 bending test; bone fixation; fatigue test; fixation devices; metallic bone staples; orthopaedic medical devices; pullout test;
soft tissue fixation; surgical implants
ANNEXES
(Mandatory Information)
A1. TEST METHOD FOR CONSTANT AMPLITUDE BENDING FATIGUE TESTS OF METALLIC BONE STAPLES
A1.1. Scope
A1.1.1 This test method covers procedures for the performance of constant amplitude fatigue testing of metallic staples used in
internal fixation of the musculoskeletal system. This test method may be used when testing in air at ambient temperature or in an
aqueous or physiological solution.
A1.1.2 The values stated in SI units are to be regarded as standard. NoAny other units of measurement are included in this
standard.standard are shown for reference only.
A1.1.3 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 safety, health and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
A1.1.4 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.
A1.2. Summary of Test Method
A1.2.1 Metallic bone staples are tested under bending loads until the specimen fails or a predetermined number of cycles has been
applied to it. Bending tests may be performed in one of two modes: either pure, in-plane bending; or tension (or compression)
combined with in-plane bending. Tests using either of these methods may be conducted at ambient conditions or in aqueous or
physiological solutions (at either room temperature or 37°C).
A1.3. Significance and Use
A1.3.1 This test method is used to determine the fatigue resistance of metallic bone staples when subjected to repetitive loading
for large numbers of cycles. This information may also be useful for comparing the effect of variations in staple material, geometry,
surface condition, or placement under certain circumstances.
A1.3.2 It is essential that uniform fatigue practices be established in order that such basic fatigue data be comparable and
reproducible and can be correlated among laboratories.
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A1.3.3 The results of fatigue tests are suitable for direct application to design only when the service conditions parallel the test
conditions exactly. This test method may not be appropriate for all types of bone staple applications. The user is cautioned to
consider the appropriateness of the test method in view of the materials being tested and their potential application.
A1.4. Apparatus
A1.4.1 Testing Machines, conforming to the requirements of Practices E4 and E467. The loads used for determining strengths shall
be within the loading range of the testing machine as defined in Practices E4 and E467.
A1.4.2 Gripping Devices:
A1.4.2.1 Staple Extensions—Pairs of specially designed metal blocks that permit the holding of individual staples for the
application of bending fatigue loads. The legs of each staple are fitted into fixation holes in each block with minimal clearance to
restrict bending of the staple within the hole. The staple is fixed securely in the block using a moldable filling or grouting agent.
The extension design should minimize the weight to reduce the influence on the staple while maintaining sufficient stiffness to
transfer the load to the staple without undesirable deflection. Holes for pin and clevis fixation are optional (see Figs. A1.1-A1.3).
NOTE A1.1—Variations in fixation hole configuration may be required for staple legs with noncircular cross sections. Also, it is necessary to provide a
gap between the underside of the staple bridge and edge of the staple extender in most cases. This is necessary to eliminate contact between the staple
bridge (or other bridge features such as tissue spikes) and the staple extender. However, this gap should be standardized within any test group as required.
A1.4.2.2 4-Point Bend Fixture—A standard or modified bending fixture that produces pure bending in the staple without
appreciable shear or torsion when used to apply load to the staple through the staple extensions.
A1.4.2.3 Pin and Clevice Fixture—A standard or modified fixture used to apply a distractive or compressive load to the staple
through the staple extensions to produce bending in the staple similar to that seen in vivo.
A1.4.3 Filling or Grouting Agent—A stiff, moldable filler, such as epoxy, acrylic cement, or a low-melting point alloy (for
example, Wood’s metal) used to secure the staple leg within the staple extension.
A1.4.4 Aqueous Solution—Tap water, distilled water, physiological saline, or similar aqueous solutions, used to immerse the test
specimens fully during the test.
FIG. A1.1 4-Point Bending of Staples in Extension
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FIG. A1.2 Combined Tension (or Compression) and Bending of Staples
FIG. A1.3 Diagram of Extender-Staple Forces Under Combined Bending and Tension
A1.4.5 Constant Temperature Bath—An aqueous bath capable of maintaining the samples and containers at physiologic
temperatures, 37 6 2°C, for the specified testing periods.
A1.5. Test Specimen
A1.5.1 Staple—A generally U-shaped metal loop, with at least two legs, that is driven into the surface of bone to either fix or
immobilize adjacent pieces of bone or to fasten soft tissue or other material to bone. All test samples shall be representative of the
material under evaluation. Samples for comparative tests shall be produced from the same material lot or batch and under the same
fabricating conditions, unless noted specifically.
F564 − 17
A1.5.2 Staple Leg—The parallel or nearly parallel extensions that are intended to penetrate the bone tissue; these may be round,
square, or polygonal in cross section, and they may possess serrations or barbs to increase the fixation or purchase strength in the
bone.
A1.5.3 Staple Bridge—The cross member of the staple connecting the legs; the bridge may be smooth or possess spikes or
projections on the underside for the retention of soft tissue or other material.
A1.6. Procedure
A1.6.1 Mounting the Specimen—Fix the staple leg in an extension block using the filling agent. A fixture should be used to ensure
proper in-plane alignment of the two extensions and the staple during this process. Also, each staple should be fixed such that the
bridge is the same distance from the top of each extension.
NOTE A1.2—This distance is at the discretion of the operator, but it determines the portion of the staple subjected to the bending loads.
A1.6.2 4-Point Bend Testing:
A1.6.2.1 Place the staple and attached staple extensions in the 4-point bending fixture such that the loading point and support
rollers contact the staple extensions on either side of the staple; direct contact of the rollers with the staple shall not be permitted
during the test. Alignment of the loading point rollers shall be symmetric on the centerline between the support rollers (see Fig.
A1.1).
A1.6.2.2 Apply cyclic loads (sinusoidal, sawtooth, and so forth), generating bending moments in the staple without permanent
deformation. Appropriate starting loads should be 50 to 75 % of the static bending strength, unless indicated otherwise.
NOTE A1.3—It may be necessary to provide a low-friction means of maintaining the position of the staple and attached extensions. Also, the fixtures
should be designed so that loads are applied equally at the loading points during each deflection throughout the test.
A1.6.2.3 Compute the bending moment, M, by the following formula, where F = force applied at each loading point and A =
distance between the loading point and support roller,roller:
M 5 FA (A1.1)
bending
M = FA.
bending
A1.6.2.4 Continue the test until failure of the staple, the fixation, or a predetermined number of load cycles hashave been applied.
A1.6.3 Combined Tension or (Compression) and Bending:
A1.6.3.1 Place the staple and attached staple extensions in the axial bending fixture. The pins and clevices should permit free
rotation of the staple extensions, with minimal friction, while maintaining alignment of the staple legs (and extensions) in the same
plane (see Fig. A1.2).
A1.6.3.2 Apply cyclic loads (sinusoidal, sawtooth, and so forth), generating bending moments in the staple without permanent
deformation. Appropriate starting loads should be 50 to 75 % of the static yield strength, unless indicated otherwise.
NOTE A1.4—It may be necessary to maintain a minimum tensile or compressive load on the specimen throughout the test, since operating at or near zero
load may result in either loss of machine control due to discontinuity in the load feedback loop or undesirable transient loading of the staple.
A1.6.3.3 Compute the bending moment in the staple bridge, M, by the following formula, where F = force applied at each center
of each pin and L = distance between the load application axis, thataxis (that is, the pin center,center) and the neutral axis of the
staple bridge, bridge:
M 5 FL ~see Fig. A1.3! (A1.2)
bending
M = FL (see Fig. A1.3).
bending
NOTE A1.5—The application of this test method produces bending, tensile (or compressive), and shear stresses in the staple. The direction and magnitudes
of these stresses should be analyzed using superposition theory or other suitable methods.
F564 − 17
A1.6.3.4 Continue the test until failure of the staple or the fixation or a predetermined number of load cycles hashave been applied.
A1.6.4 Stress Verification—It is recommended that strain gages (or extensometry) be used to measure the bending strains induced
in the specimen. This is accomplished most easily on the staple bridge, but it may be possible to perform on a portion of the staple
leg or at the leg-bridge junction under certain circumstances and with certain staple designs. The recommended technique is to
strain gage the actual fatigue test specimens, if possible, provided that the installation of the strain gage will not influence the test
results.
A1.7 Test Termination
A1.7.1 Continue the tests until the specimen fails or a predetermined number of cycles hashave been applied to the specimen.
Failure should be defined as complete separation, a crack visible at a specified magnification, a crack of certain dimensions, or by
some other criterion. State the criterion selected for defining failure when reporting the results.
A1.7.2 A test shall be considered invalid if loosening of the staple occurs in the embedding medium, if noticeable yielding occurs,
or permanent deformation occurs in the specimen.
A1.8. Report
A1.8.1 Report the following information:
A1.8.1.1 Staple Description—Type, size, special features (barbs, spikes, and so forth), manufacturer, material, batch or lot number,
and dimensions (including leg length, bridge width, and length), as appropriate.
A1.8.1.2 Test Type—4-point or combined tension (or compression) and bending.
A1.8.1.3 Fixation Geometry—Load point separation distances (4-point bending), load offset distance (combined tension and
bending), staple bridge-extension distance, and so forth.
A1.8.1.4 Minimum and maximum cycle loads, test frequency (for example, cycles/s), and forcing function type (sine, ramp, saw
tooth, and so forth).
A1.8.1.5 Bending moment, M (N-m).
A1.8.1.6 Load ratio, R, where R = minimum load/maximum load.
A1.8.1.7 Test Environment—Ambient air or physiological solution.
A1.8.1.8 Number of cycles at failure or test termination (runout).
A1.8.1.9 Location of fatigue fracture (if applicable).
A1.8.1.10 Reason for test termination, thattermination (that is, staple failure, fixation failure, runout to specified cycle limit, and
so forth.forth).
A1.9. Precision
A1.9.1 Intralaboratory and interlaboratory reproducibility have not been determined systematically.
A1.10 Rationale (Nonmandatory Information)
A1.10.1 This test method is intended to aid in characterizing the fatigue behavior of metallic bone staples used for the fixation
of bone to bone or soft tissue to bone. The data obtained using this test method may be used to compare staple materials, designs,
or placements under certain circumstances.
F564 − 17
A1.10.2 This test method is intended to simulate potential in vivo staple loading conditions. However, in vitro testing of these
devices may not duplicate their in vivo behavior adequately.
A2. TEST METHOD FOR PULL-OUT FIXATION STRENGTH OF METALLIC BONE STAPLES
A2.1. Scope
A2.1.1 This test method covers testing of the hard tissue pull-out fixation strength of metallic staples used in the internal fixation
of the musculoskeletal system. This test method may be used with physiologic bone or a synthetic substitute. It may also be used
when testing in an aqueous or physiological solution.
A2.1.2 The values stated in SI units are to be regarded as standard. NoAny other units of measurement are included in this
standard.standard are shown for reference only.
A2.1.3 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 safety, health and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
A2.1.4 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.
A2.2. Summary of Test Method
A2.2.1 A thin, flat, flexible metal or fabric strap is fixed to bone (or a substitute) using a single staple. Tension is applied equally
to both ends of the strap in a direction parallel to the staple legs until loss of staple fixation occurs. Tests using this test method
may be conducted at ambient conditions or in aqueous or physiological solutions at either room temperature or 37°C.
A2.3. Significance and Use
A2.3.1 This test method is intended to help assess the axial holding strength of various metallic bone staples used to fix either soft
or hard tissue to bone. This information may be useful for comparisons of staple materials, designs, or placement under certain
circumstances.
A2.3.2 This test method may not be appropriate for all types of bone staple applications. The user is cautioned to consider the
appropriateness of the test method in view of the materials being tested and their potential application.
A2.4. Apparatus
A2.4.1 Testing Machines, conforming to the requirements of Practices E4. The loads used for determining strengths shall be within
the loading range of the testing machine as defined in Practices E4.
A2.4.2 Gripping Devices:
A2.4.2.1 Hard Tissue Grips—Grips designed specifically for secure grasping of bones, bone segments, or bone substitutes with
minimal material effects at the staple fixation site during the application of tension to the metal or fabric strap. These grips
mustshall allow for variation in bone geometry and permit proper orientation and alignment of the bone (or substitute) during the
test.
A2.4.2.2 Metal or Fabric Strap Grips—Grips designed for secure grasping of the metal or fabric strap with minimal damage
during the application of tension. Typical grips may be actuated mechanically, pneumatically, or hydraulically to compress the strap
between two flat grip faces parallel to the line of load application. The grip faces may be smooth or serrated.
A2.4.2.3 Constant Temperature Bath—An aqueous bath capable of maintaining the samples and containers at physiologic
temperatures, 37 6 2°C, for the specified testing periods.
F564 − 17
A2.5. Test Specimen
A2.5.1 Staple—A generally U-shaped metal loop, with at least two legs, that is driven into the surface of bone to either fix or
immobilize adjacent pieces of bone or to fasten soft tissue or other material to bone. All test samples shall be representative of the
material under evaluation. Samples for comparative tests shall be produced from the same material lot or batch and under the same
fabricating conditions, unless noted specifically.
A2.5.2 Staple Leg—The parallel or nearly parallel extensions that are intended to penetrate the bone tissue; these may be round,
square, or polygonal in cross section, and they may possess serrations or barbs to increase the fixation or purchase strength in the
bone.
A2.5.3 Staple Bridge—The cross member of the staple connecting the legs; the bridge may be smooth or possess spikes or
projections on the underside for the retention of soft tissue or other material.
A2.5.4 Bone—Fresh, fresh frozen, or preserved bone with material properties representative of the staple placement site; either
cadaveric or animal bone may be suitable.
A2.5.5 Bone Substitute—A material with known, consistent properties, similar in strength, density, or rigidity to fresh, fresh
frozen, or preserved bone. Substitutes such as natural wood, solid plastics, composites, or rigid foams may be suitable, depending
on type, material properties, and configuration.
A2.5.6 Metal or Fabric Tension Strap—A thin, flat, flexible, highly conformable metal strip or fabric (woven or braided) that is
used to apply a balanced lifting or pull-out force under the staple bridge. The strap should have a width sufficient to support 90 %
of the staple bridge and have sufficient tensile properties so that it does not deform plastically or rupture under the applied loads.
A2.5.7 Aqueous Solution—Tap water, distilled water, physiological saline, or similar aqueous solutions, used to either maintain
hydration of the soft tissue and bone used in the test or bathe or immerse the test specimens fully during the test.
A2.6. Procedure
A2.6.1 Prepare the staple fixation site(s) on the bone (or substitute); this may require predrilling to accommodate the staple legs
without damagedamaging or fracture of fracturing the bone (or substitute).
A2.6.2 Insert and seat the staple in the bone (or substitute) in a standardized, repeatable manner using all appropriate surgical
instrumentation specified by the manufacturer. The staple should be positioned over the tension strap, interposing the metal or
fabric between the staple bridge and bone surface, leaving equal lengths of the strap on either side of the staple bridge. The strap
should also be centered under the staple bridge, and the strap bulk should permit the staple to be seated against the bone fully. The
staple bridge should be perpendicular to the long axis of the strap.
NOTE A2.1—In order to either reduce the inherent variability of manual staple insertion techniques or investigate the effects of deliberate variation of
insertion parameters, it is permissible to devise special instrumentation in addition to that provided by the manufacturer. These additional instruments may
be used to limit staple angulation, control insertion depth, or standardize insertion forces. However, any use of nonstandard surgical instrumentation for
staple insertion mustshall be described and reported fully.
A2.6.3 Record the insertion method (manual or mechanical), staple orientation, and position from known landmarks (if
applicable).
A2.6.4 Fix the bone (or substitute) in the machine grips and align so that tension can be applied to the strap ends parallel to the
staple legs. The bone should be gripped at a sufficient distance from the staple fixation site so that the fixation site is left undamaged
and undisturbed (see the schematic of staple pull-out testing in Fig. A2.1).
A2.6.5 Grasp the ends of the strap, place them together, and secure them between the flat grip faces under equal tension (see Fig.
A2.1).
NOTE A2.2—It is recommended that self-alignment devices such as universal joints, pin pivots, and so forth be placed in the load train in order to minimize
F564 − 17
FIG. A2.1 Schematic of Staple Pull-Out Testing
the eccentric loading of either the tension strap or the staple.
A2.6.6 Apply the load to the strap at a constant displacement, load, or strain rate.
A2.6.7 Monitor the load-displacement continuously until one of the test termination criteria is reached.
NOTE A2.3—Elastic deformation in the strap may require a separate method of monitoring staple movement during the test.
A2.7 Test Termination
A2.7.1 Testing of the samples shall be terminated when one or more of the following has occurred:
A2.7.1.1 A significant drop in tensile load after peak,
A2.7.1.2 Visible tearing or rupture of the strap (or substitute),
A2.7.1.3 Fracture of the bone (or bone substitute), or
A2.7.1.4 Loosening of the staple(s) or disruption of the staple-bone interface.
A2.8. Report
A2.8.1 Report the following information:
A2.8.1.1 Staple Description—Type, size, special features (barbs, spikes, and so forth), manufacturer, material, batch or lot number,
and dimensions (including leg length, bridge width, and length), as appropriate.
F564 − 17
A2.8.1.2 Fixation site and orientation (if applicable).
A2.8.1.3 Staple
...