ASTM F897-02(2013)
(Test Method)Standard Test Method for Measuring Fretting Corrosion of Osteosynthesis Plates and Screws
Standard Test Method for Measuring Fretting Corrosion of Osteosynthesis Plates and Screws
SIGNIFICANCE AND USE
4.1 It is well known from examination of implants after use that plates and screws used for osteosynthesis are subjected to metal loss due to corrosion at the plate-screw interfaces. One of the mechanisms of this corrosive attack is fretting corrosion due to relative motion (micromotion) between the screw heads and plate-hole countersinks.
4.2 It is also known that release of corrosion products into the tissues surrounding an implant may have adverse effects on local tissue or have systemic effects. Thus, it is important to minimize the amount of tissue exposure to corrosion products.
4.3 Screws and plates are available in different configurations in accordance with Specifications F543 and F382. This test method may be used to evaluate the effects of different combinations of screw and plate designs. As new materials and device designs are developed for use in the treatment of fractured bones, it is important to determine the effects these developments have on the amount of metal loss due to fretting corrosion.
4.4 This test method provides a standardized screening test for ranking metal plates and screws in terms of resistance to fretting corrosion and for determining the influence of different solutions on fretting corrosion rates.
4.5 This test method may also be used to generate corrosion products either for chemical analysis of the products or for testing for biological reactions to corrosion products using animal or cell culture methods.
4.6 It is well known that fretting corrosion rates depend on normal load or pressure, frequency, sliding amplitude, materials, surface treatments, and environmental factors. (4) Therefore, when determining the effect of changing one of these parameters (for example, material or environment), all others must be kept constant to facilitate interpretation of the results.
SCOPE
1.1 This test method provides a screening test for determining the amount of metal loss from plates and screws used for osteosynthesis (internal fixation of broken bones) due to fretting corrosion in the contact area between the screw head and the plate hole countersink area. The implants are used in the form they would be used clinically. The machine described generates a relative motion between plates and screws which simulates one type of motion pattern that can occur when these devices are used clinically.
1.2 Since the environmental and stress conditions used in this test method may not be identical to those experienced by bone plates in the human body, this test method may produce fretting corrosion rates that are lower or higher than those experienced in practice. The recommended axial load of 400 N was selected as being in a range where the amount of fretting corrosion is not sensitive to small changes in axial load (1).2 The combination of the recommended load and angular displacement are such that a measurable amount of fretting corrosion of surgical alloys occurs in a comparatively short period of time (7 to 14 days). (Refs 1-3)
1.3 The device is designed so as to facilitate sterilization of the test specimens and test chambers to permit testing with proteinaceous solutions that would become contaminated with microbial growth in nonsterile conditions.
1.4 The specimens used can be standard osteosynthesis implants or can be materials fabricated into the appropriate shapes.
1.5 This test method may be used for testing the fretting corrosion of metal plates and screws of similar or different alloy compositions, or it may be used for testing the fretting corrosion of metal-nonmetal combinations. This test method may also be used for wear or degradation studies of nonmetallic materials. This test method may be used as a screening test to rank the corrosivities of saline or proteinaceous solutions, or to rank metal-to-metal couples for resistance to fretting corrosion, or to study other material combinations.
1.6 The values stated in either SI un...
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F897 − 02 (Reapproved 2013)
Standard Test Method for
Measuring Fretting Corrosion of Osteosynthesis Plates and
Screws
ThisstandardisissuedunderthefixeddesignationF897;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope tallic materials. This test method may be used as a screening
test to rank the corrosivities of saline or proteinaceous
1.1 This test method provides a screening test for determin-
solutions, or to rank metal-to-metal couples for resistance to
ing the amount of metal loss from plates and screws used for
fretting corrosion, or to study other material combinations.
osteosynthesis (internal fixation of broken bones) due to
fretting corrosion in the contact area between the screw head 1.6 The values stated in either SI units or inch-pound units
and the plate hole countersink area. The implants are used in are to be regarded separately as standard. The values stated in
the form they would be used clinically. The machine described each system may not be exact equivalents; therefore, each
generates a relative motion between plates and screws which system shall be used independently of the other. Combining
simulates one type of motion pattern that can occur when these values from the two systems may result in non-conformance
devices are used clinically. with the standard.
1.7 This standard may involve hazardous materials,
1.2 Since the environmental and stress conditions used in
operations, and equipment. This standard does not purport to
this test method may not be identical to those experienced by
address all of the safety concerns associated with its use. It is
bone plates in the human body, this test method may produce
the responsibility of whoever uses this standard to consult and
fretting corrosion rates that are lower or higher than those
establish appropriate safety and health practices and deter-
experienced in practice.The recommended axial load of 400 N
mine the applicability of regulatory limitations prior to use.
was selected as being in a range where the amount of fretting
corrosion is not sensitive to small changes in axial load (1).
2. Referenced Documents
The combination of the recommended load and angular dis-
placement are such that a measurable amount of fretting 2.1 ASTM Standards:
corrosion of surgical alloys occurs in a comparatively short
D1886 Test Methods for Nickel in Water
period of time (7 to 14 days). (Refs 1-3)
F86 Practice for Surface Preparation and Marking of Metal-
lic Surgical Implants
1.3 The device is designed so as to facilitate sterilization of
F382 SpecificationandTestMethodforMetallicBonePlates
the test specimens and test chambers to permit testing with
F543 Specification and Test Methods for Metallic Medical
proteinaceous solutions that would become contaminated with
Bone Screws
microbial growth in nonsterile conditions.
G1 Practice for Preparing, Cleaning, and Evaluating Corro-
1.4 The specimens used can be standard osteosynthesis
sion Test Specimens
implants or can be materials fabricated into the appropriate
shapes.
3. Summary of Test Method
1.5 This test method may be used for testing the fretting
3.1 A two-hole plate is attached to two plastic rods with
corrosion of metal plates and screws of similar or different
bone screws, with flexible spacers between the plate and the
alloy compositions, or it may be used for testing the fretting
rods, placed in a glass beaker, and the beaker sealed with a
corrosion of metal-nonmetal combinations. This test method
flexible rubber cover. This assembly is steam sterilized, and
may also be used for wear or degradation studies of nonme-
then a sterile solution is injected through the rubber cover into
the beaker. This assembly is then mounted in the fretting
apparatus which, when set in motion, produces a rocking
This test method is under the jurisdiction ofASTM Committee F04 on Medical
motion and, therefore, a small cyclic displacement between the
and Surgical Materials and Devicesand is the direct responsibility of Subcommittee
F04.15 on Material Test Methods.
Current edition approved March 1, 2013. Published March 2013. Originally
approvedin1984.Lastpreviouseditionapprovedin2007asF897 – 02(2007).DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/F0897-02R13. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
The boldface numbers in parentheses refer to the list of references at the end of Standards volume information, refer to the standard’s Document Summary page on
this standard. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F897 − 02 (2013)
mating surfaces of the plate and screws.The amount of fretting testing for biological reactions to corrosion products using
corrosion is determined at the end of the test by measurement animal or cell culture methods.
of the weight loss of the plates and screws and by chemical
4.6 It is well known that fretting corrosion rates depend on
analysis of the solutions.
normal load or pressure, frequency, sliding amplitude,
materials, surface treatments, and environmental factors. (4)
4. Significance and Use
Therefore, when determining the effect of changing one of
4.1 It is well known from examination of implants after use
these parameters (for example, material or environment), all
that plates and screws used for osteosynthesis are subjected to
others must be kept constant to facilitate interpretation of the
metallossduetocorrosionattheplate-screwinterfaces.Oneof
results.
the mechanisms of this corrosive attack is fretting corrosion
5. Apparatus
due to relative motion (micromotion) between the screw heads
and plate-hole countersinks.
5.1 Steam Autoclave, capable of maintaining 121 6 2°C
[250 6 4°F], and equipped with a thermometer, pressure
4.2 It is also known that release of corrosion products into
gauge, vent cock, and a rack to hold the test assemblies above
the tissues surrounding an implant may have adverse effects on
the water level.
local tissue or have systemic effects. Thus, it is important to
minimize the amount of tissue exposure to corrosion products.
5.2 Microbalance, with a 0.01-mg scale.
4.3 Screws and plates are available in different configura-
5.3 Fretting Apparatus, as described in 5.3.1 – 5.3.4 and
tions in accordance with Specifications F543 and F382. This
illustrated in Fig. 1 and Fig. 2.
test method may be used to evaluate the effects of different
5.3.1 The fretting apparatus is driven by a slow speed gear
combinations of screw and plate designs.As new materials and
motor connected to a horizontal rotating shaft. Round disks
device designs are developed for use in the treatment of
with machined flats (cams) are mounted on the shaft as shown
fractured bones, it is important to determine the effects these
in Fig. 1. For multiple specimen testing, there may be more
developments have on the amount of metal loss due to fretting
than one cam on the drive shaft.
corrosion.
5.3.2 Theflatsonthecamsaremachinedsoastoproduce2°
of relative motion between the posts of the test assemblies.
4.4 This test method provides a standardized screening test
for ranking metal plates and screws in terms of resistance to
NOTE 1—A suggested combination of short post length and plunger
fretting corrosion and for determining the influence of different
displacement is a 5-cm post with a 1.9-mm displacement.
solutions on fretting corrosion rates.
5.3.3 The shaft rotation rate and the number of machined
4.5 This test method may also be used to generate corrosion flats shall be such that the flats produce one oscillation of the
products either for chemical analysis of the products or for plunger per second.
NOTE 1—Figure shows assembly drawings of one pair of test positions on each side of a cam, and of the relationships between the screws, plate,
spacers, and polyacetal rods.
FIG. 1 Two-Hole Plate Fretting (THPF) Testing System
F897 − 02 (2013)
protein solutions. If proteins are used, the solutions shall be
sterileinaccordancewith8.1.5.Proteinsolutionsmayeitherbe
purchased sterile, or sterilized by filtration. These shall be
reported in accordance with 10.1.
7. Test Specimens
7.1 Plates:
7.1.1 The plates used for these tests may be cut from
commercially available plates for osteosynthesis.
7.1.2 Platesmaybefabricatedfrom3.5-mmorthickermetal
sheet or strip. Holes may be prepared in accordance with
Specification F382. Holes may be round, or slotted, or “self-
compressing” type.
FIG. 2 Assembled Test Chamber with Rubber Seal
7.2 Screws:
7.2.1 Screws used for this test may be commercially avail-
5.3.4 Testassemblyholdinganddrivingframesaremounted able bone screws. Heads should be spherical, although other
symmetrically on each side of the rotating cams. The oscillat-
shapes may be used.
ing plunger is springloaded and held in the guide sleeve. The
7.2.2 Screws may be fabricated from rod stock in accor-
hole in the top plate is slotted to permit adjustment of the
dance with Specification F543.
position of the test assemblies.
7.3 Test specimens may be used in the condition as received
5.4 Test Assemblies, consisting of two plastic rods, and two
from the implant manufacturer; custom fabricated specimens
flexible spacers, the two-hole plate, two bone screws, one
should be prepared in accordance with Practice F86.
beaker, and the rubber cover.
5.4.1 The longer rod is threaded at one end to mate with a
8. Procedure
mounting screw, while the other end is threaded to mate with
8.1 Test Assembly Preparation (see Fig. 1):
the bone screw.
8.1.1 Clean the plates and screws ultrasonically with deter-
5.4.2 The shorter rod has a reduced diameter at one end to
gent or other degreasing agent to ensure that they are free from
mate with the oscillating horizontal plunger, while the other
grease and dirt. Rinse them with distilled water, and immedi-
end is threaded to mate with a bone screw.
ately dry them in warm air.
5.4.3 The flexible spacers made of, for example, polydim-
8.1.2 Weigh the plate and each screw separately. Then
ethylsiloxane or buna-n, are used to maintain axial loads on the
weigh the three together on a microbalance to an accuracy of
screws and to permit the necessary axial displacements asso-
0.01 mg.
ciated with the rocki
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.