ASTM F543-23

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.
Designation: F543 − 23
Standard Specification and Test Methods for
Metallic Medical Bone Screws
This standard is issued under the fixed designation F543; 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 particular device design. This may only be a subset of the
herein described test methods.
1.1 This specification provides requirements for materials,
1.6 This standard may involve the use of hazardous
finish and marking, care and handling, and the acceptable
materials, operations, and equipment. This standard does not
dimensions and tolerances for metallic bone screws that are
purport to address all of the safety concerns, if any, associated
implanted into bone. The dimensions and tolerances in this
with its use. It is the responsibility of the user of this standard
specification are applicable only to metallic bone screws
to establish appropriate safety, health, and environmental
described in this specification.
practices and determine the applicability of regulatory limita-
1.2 This specification provides performance considerations
tions prior to use.
and standard test methods for measuring mechanical properties
1.7 This international standard was developed in accor-
in torsion of metallic bone screws that are implanted into bone.
dance with internationally recognized principles on standard-
These test methods may also be applicable to other screws
ization established in the Decision on Principles for the
besides those whose dimensions and tolerances are specified
Development of International Standards, Guides and Recom-
here. The following annexes are included:
mendations issued by the World Trade Organization Technical
1.2.1 Annex A1—Test Method for Determining the Tor-
Barriers to Trade (TBT) Committee.
sional Properties of Metallic Bone Screws.
1.2.2 Annex A2—Test Method for Driving Torque of Medi-
2. Referenced Documents
cal Bone Screws.
2.1 ASTM Standards:
1.2.3 Annex A3—Test Method for Determining the Axial
E4 Practices for Force Calibration and Verification of Test-
Pullout Load of Medical Bone Screws.
ing Machines
1.2.4 Annex A4—Test Method for Determining the Self-
E6 Terminology Relating to Methods of Mechanical Testing
Tapping Performance of Self-Tapping Medical Bone Screws.
E8/E8M Test Methods for Tension Testing of Metallic Ma-
1.2.5 Annex A5—Specifications for Type HA and Type HB
Metallic Bone Screws. terials
E122 Practice for Calculating Sample Size to Estimate, With
1.2.6 Annex A6—Specifications for Type HC and Type HD
Metallic Bone Screws. Specified Precision, the Average for a Characteristic of a
Lot or Process
1.2.7 Annex A7—Specifications for Metallic Bone Screw
Drive Connections. F67 Specification for Unalloyed Titanium, for Surgical Im-
plant Applications (UNS R50250, UNS R50400, UNS
1.3 This specification is based, in part, upon ISO 5835, ISO
R50550, UNS R50700)
6475, and ISO 9268.
F86 Practice for Surface Preparation and Marking of Metal-
1.4 The values stated in SI units are to be regarded as
lic Surgical Implants
standard. No other units of measurement are included in this
F116 Specification for Medical Screwdriver Bits
standard.
F136 Specification for Wrought Titanium-6Aluminum-
4Vanadium ELI (Extra Low Interstitial) Alloy for Surgical
1.5 Multiple test methods are included in this standard.
Implant Applications (UNS R56401)
However, the user is not necessarily obligated to test using all
F138 Specification for Wrought 18Chromium-14Nickel-
of the described methods. Instead, the user should only select,
2.5Molybdenum Stainless Steel Bar and Wire for Surgical
with justification, test methods that are appropriate for a
Implants (UNS S31673)
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. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved June 1, 2023. Published July 2023. Originally approved contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
in 1977. Last previous edition approved in 2017 as F543 – 17. DOI: 10.1520/F0543- Standards volume information, refer to the standard’s Document Summary page on
23. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F543 − 23
F565 Practice for Care and Handling of Orthopedic Implants 10664 Hexalobular Internal Driving Feature for Bolts and
and Instruments Screws
F620 Specification for Titanium Alloy Forgings for Surgical
3. Terminology
Implants in the Alpha Plus Beta Condition
F799 Specification for Cobalt-28 Chromium-6 Molybdenum
3.1 Definitions—Some of the terms defined in this section
Alloy Forgings for Surgical Implants (UNS R31537,
are shown in Fig. 1.
R31538, R31539)
F983 Practice for Permanent Marking of Orthopaedic Im-
plant Components
F1295 Specification for Wrought Titanium-6Aluminum-
7Niobium Alloy for Surgical Implant Applications (UNS
R56700)
F1314 Specification for Wrought Nitrogen Strengthened 22
Chromium–13 Nickel–5 Manganese–2.5 Molybdenum
Stainless Steel Alloy Bar and Wire for Surgical Implants
(UNS S20910)
F1472 Specification for Wrought Titanium-6Aluminum-
4Vanadium Alloy for Surgical Implant Applications (UNS
R56400)
F1537 Specification for Wrought Cobalt-28Chromium-
6Molybdenum Alloys for Surgical Implants (UNS
FIG. 1 Schematic of Screw Terms
R31537, UNS R31538, and UNS R31539)
F1586 Specification for Wrought Nitrogen Strengthened
21Chromium—10Nickel—3Manganese—
3.1.1 axial pullout load—the tensile force required to fail or
2.5Molybdenum Stainless Steel Alloy Bar for Surgical
remove a bone screw from a material into which the screw has
Implants (UNS S31675)
been inserted.
F1713 Specification for Wrought Titanium-13Niobium-
3.1.2 breaking angle—angle of rotation when the screw fails
13Zirconium Alloy for Surgical Implant Applications
in torsion as demonstrated by a rapid decrease in the indicated
(UNS R58130) (Withdrawn 0)
torque.
F1813 Specification for Wrought Titanium-12Molybdenum-
3.1.3 buttress thread—an asymmetrical thread profile char-
6Zirconium-2Iron Alloy for Surgical Implant (UNS
acterized by a pressure flank which is nearly perpendicular to
R58120)
the screw axis.
F1839 Specification for Rigid Polyurethane Foam for Use as
a Standard Material for Testing Orthopaedic Devices and 3.1.4 cancellous screw—a screw designed primarily to gain
Instruments
purchase into cancellous bone. Cancellous screws typically
F2066 Specification for Wrought Titanium-15 Molybdenum have an HB (see 4.1.2) thread and may or may not be fully
Alloy for Surgical Implant Applications (UNS R58150)
threaded.
F2503 Practice for Marking Medical Devices and Other
3.1.5 cortical screw—a screw designed primarily to gain
Items for Safety in the Magnetic Resonance Environment
biocortical purchase into cortical bone. Cortical screws typi-
2.2 ISO Standards: cally have a HA (see 4.1.1) thread and are fully threaded.
5835 Implants for Surgery—Metal Bone Screws with Hex-
3.1.6 core diameter—the smallest diameter of the threaded
agonal Driver Connection, Spherical Under Surface of
portion of the screw measured at the thread root. This is also
Head, Asymmetrical Thread—Dimensions
known as the minor diameter or root diameter.
6475 Implants for Surgery—Metal Bone Screws with Asym-
3.1.7 gage length—the distance between the holding device
metrical Thread and Spherical Under-Surface—
(for example, a split collet) and the underside of the screw
Mechanical Requirements and Test Methods
head.
8319-1 Orthopaedic Instruments—Drive connections—Part
3.1.8 grip length—the length of threads held fast in the split
1: Keys for use with hexagon socket heads
collet or other holding mechanism.
8319-2 Orthopaedic Instruments—Drive connections—Part
2: Screwdrivers for single slot head screws, screws with 3.1.9 insertion depth—the threaded length as inserted into
cruciate and cross-ecessed head screws
the test block.
9268 Implants for Surgery—Metal Bone Screws with Coni-
3.1.10 insertion torque—the amount of torque required to
cal Under-Surface of Head—Dimensions
overcome the frictional force between the screw and the
material used for testing while driving the screw into the
material.
The last approved version of this historical standard is referenced on
3.1.11 maximum torque (N-m)—the largest value of torque
www.astm.org.
recorded during the period of rotation before screw failure in
Available from American National Standards Institute, 25 W. 43rd St., 4th
Floor, New York, NY 10036. torsional shear when tested in accordance with Annex A1.
F543 − 23
3.1.12 nontapping screw—a screw that has a tip that does 4.1.1 Type HA—Spherical undersurface of head, shallow,
not contain a flute. Nontapping screws usually require a tap to asymmetrical buttress thread, and deep screw head.
be inserted into the pilot hole before the insertion of the screw, 4.1.2 Type HB—Spherical undersurface of head, deep,
when used in moderate or hard bone. asymmetrical buttress thread, and shallow screw head.
4.1.3 Type HC—Conical undersurface of head, symmetrical
3.1.13 partially threaded screw—a screw whose threaded
thread.
portion does not extend fully from the screw point to the screw
4.1.4 Type HD—Conical undersurface of head, asymmetri-
head but instead has a smooth shaft running between the head
cal thread.
and threads.
3.1.14 pilot hole—the hole drilled into the bone into which
5. Material
the screw tip is inserted. The pilot hole is normally slightly
5.1 Screws shall be fabricated from a metallic material
larger than the screw’s core diameter. However, if the screw is
intended for surgical implant applications, and meeting the
to be used to provide compression across a fracture, a portion
requirements for an ASTM medical material. In addition, the
of the pilot hole may be larger to allow for a clearance fit.
materials shall be biocompatible for the intended application.
3.1.15 pitch—the length between the thread crests.
3.1.16 removal torque—the amount of torque required to
6. Dimensions and Tolerances
overcome the frictional force between the screw and the
6.1 There are many types of metallic bone screw designs
material used for testing while removing the screw from the
available, so a complete list of dimensions and tolerances for
material (for example, counterclockwise rotation for right-hand
all screws covered by this specification is unfeasible. However,
thread).
this specification does provide required dimensions and toler-
3.1.17 screw head—the end of the screw which is opposite
ances for four types of screws as classified in 4.1. Screws
of the tip and to which the means of inserting the screw is
conforming to this specification, and designated HA, HB, HC,
coupled.
or HD screws, shall be fabricated in accordance with the
3.1.18 screw length—the overall length of the screw mea-
dimensions and tolerances described in Annex A5 and Annex
sured from the screw head to the screw tip.
A6.
3.1.19 screw thread—a helical groove on a cylindrical or
7. Finish and Marking
conical surface. The projecting helical ridge thus formed is
called a screw thread, consisting of peaks (crests) and valleys
7.1 The screw shall be free from nicks, dents, burrs, and
(roots).
scratches when examined in accordance with Practice F86.
3.1.20 self-tapping force (N)—the amount of axial force
7.2 When size permits, the following information should be
required to engage the self-tapping features of self-tapping
legibly marked on the head of the screw (in order of prefer-
style screws when tested in accordance with Annex A4.
ence):
3.1.21 self-tapping screw—a screw that has any number of
7.2.1 Manufacturer’s name or logo,
flutes at its tip which are intended to cut the screw’s thread
7.2.2 Screw Size—If a screw is manufactured in accordance
form into the bone upon insertion.
with ASTM or ISO specifications, the ASTM or ISO designa-
tion should be provided,
3.1.22 size—an identification of a screw based on its nomi-
7.2.3 Material,
nal thread diameter, as defined in Section 6.
7.2.4 Catalog number, and
3.1.23 solid core—a screw that does not contain a cannula-
7.2.5 Manufacturing lot number.
tion along its longitudinal axis.
7.3 Screws shall be marked in accordance with Practice
3.1.24 thread diameter—the largest diameter of the threaded
F983, unless otherwise specified in 7.2, in a manner such that
portion of the screw measured over the thread crests. This is
the mechanical integrity of the screw is not compromised.
also known as the major diameter.
3.1.25 thread length—the length of the threaded portion of
8. Care and Handling
the screw, measured from the thread runout to the screw tip.
8.1 Screws should be cared for and handled in accordance
3.1.26 thread runout—the intersection of the screw thread
with Practice F565, as appropriate.
with either the screw shaft or screw head.
8.2 Consider Practice F2503 to identify potential hazards
3.1.27 torsional yield strength (N-m)—the point at which
produced by interactions between the device and the MR
the screw reaches its proportional limit when tested in accor-
environment and for terms that may be used to label the device
dance with Annex A1. This will be determined by the offset
for safety in the MR environment.
method. A 2° offset value shall be used.
4. Classification 9. Driving Instruments
4.1 There are a large variety of medical bone screws 9.1 A variety of screwdrivers for the insertion and removal
currently in use. They may be classified by the definitions of bone screws exist. The classification and dimensions for
provided in Section 3. This specification currently includes various screw-drive recesses currently used in the medical
information that defines the following types of screws: industry are documented in Annex A7. Specification F116
F543 − 23
provides related dimensional information for several types of bone. The pullout load may be determined using the test
medical screwdrivers. methods described in Annex A3.
10.1.4 Insertion Torque—This test method may be an im-
9.2 Screws conforming to this specification, and designated
portant parameter to avoid failure of the screw during insertion
HA, HB, HC, or HD screws, shall be manufactured with drive
and to ensure that the screw may be easily inserted by the
recesses that conform to the requirements specified in Annex
surgeon. The insertion torque should be much less than
A5 and Annex A6.
torsional yield strength of the screw and of the appropriate
screwdriver bit. The insertion torque may be determined using
10. Performance Considerations and Test Methods
the test methods described in Annex A2.
10.1.5 Removal Torque—This test method may be an im-
10.1 The following properties may be important when
portant parameter to avoid failure of the screw during removal
determining the suitability of a screw for a particular applica-
and to ensure that the screw may be easily removed by the
tion. However, the test methods referenced as follows may not
surgeon. The removal torque should be much less than tor-
be appropriate for all types of implant applications. The user is
sional yield strength of the screw and of the appropriate
cautioned to consider the appropriateness of the test methods in
screwdriver bit. The removal torque may be determined using
view of the devices being tested and their potential application.
the test methods described in Annex A2.
10.1.1 Torsional Strength—This test method is an important
10.1.6 Self-Tapping Force—This test method may be an
parameter to prevent screw breakage during insertion or
important parameter to ensure that the screw may be easily
removal. The torsional strength shall be determined using the
inserted by the surgeon, particularly if the screw is fixed in
test methods described in Annex A1.
poor quality or osteoporotic bone. The self-tapping force may
10.1.2 Breaking Angle—This test method provides a mea-
be determined using the test method described in Annex A4.
sure of the ductility of the screw when undergoing a torsional
moment. A screw with a greater breaking angle may provide an 11. Performance Requirements
earlier tactile warning to the surgeon that the screw is reaching
11.1 Screws shall meet the mechanical performance require-
its maximum torsional strength. The breaking angle shall be
ments specified in its associated specification annex.
determined using the test methods described in Annex A1.
12. Keywords
10.1.3 Axial Pullout Load—This test method may be an
important parameter if the screw is subjected to axial tensile 12.1 bone screw; dimensions; insertion; performance re-
forces, or if the screw is fixed into poor quality or osteoporotic quirements; pullout; static; test methods; torsion
ANNEXES
(Mandatory Information)
A1. TEST METHOD FOR DETERMINING THE TORSIONAL PROPERTIES OF METALLIC BONE SCREWS
A1.1 Significance and Use
A1.1.1 This test method is used to measure the torsional fixture for the torsional yield strength maximum torque-
yield strength, maximum torque, and breaking angle of the breaking angle test is illustrated in Fig. A1.1.
bone screw under standard conditions. The results obtained in
A1.2.1.1 Test Speed—The torsional force shall be applied at
this test method are not intended to predict the torque encoun- a constant rate of 1 to 5 r/min.
tered while inserting or removing a bone screw in human or
A1.2.1.2 Torque Transducer—A transducer to translate the
animal bone. This test method is intended only to measure the applied torque into an electrical signal amenable to continuous
uniformity of the product tested or to compare the mechanical
recording, calibrated over the range of torques, both in the
properties of different, yet similarly sized, products. clockwise and counterclockwise rotation, to be encountered in
the test method, shall be provided.
A1.2 Apparatus
A1.2.1.3 Torsional Displacement Transducer—A transducer
to translate the angle of twist into an electrical signal amenable
A1.2.1 Testing Fixture—The torsion testing apparatus that is
to continuous recording, calibrated over the range of angles to
to be used for applying the required torque to the specimen
be encountered in the test and an accuracy of 60.3°, both in the
shall be calibrated for the range of torques and rotational
clockwise and counterclockwise rotation, shall be provided.
displacements used in the determination. A suitable testing
A1.2.1.4 Specimen Holder—A mechanical device to clamp
onto the bone screw to prevent its rotation while being stressed
without significantly damaging its mechanical integrity shall be
At the time that this specification was approved, no standard test method for the
provided. One such method is to insert a threaded stopper into
verification of torsion machines or transducers has been accepted. The user is urged
to review Terminology E6 and Test Methods E8/E8M for general guidance. the opposite side of a test block. The test block for this holding
F543 − 23
appropriate. Place the split collet in the collet holder. Clamp the
split collet and holder in the vise. The clamping force of the
vise should be sufficient to prevent rotation of the screw or the
split collet. Drive the specimen in the direction of insertion,
using an appropriate size and configured screwdriver bit, by
applying a torsional force. If an axial load is required to
maintain the screwdriver bit in the screw head, its value should
be noted. The torque wrench shall be driven at a rate of 1 to 5
revolutions/min (r/min).
NOTE A1.1—The simultaneous use of two chart recorders may simplify
the ability to measure torsional yield strength accurately by the offset
method. One chart recorder with an angular displacement scale or
sensitivity of 50°/cm is convenient for measuring maximum torque and
breaking angle. A second chart recorder with an angular displacement
scale or sensitivity of 10°/cm or less is suggested to provide accurate offset
measurement capability for measuring a 2° angular displacement.
Alternatively, one chart recorder and a digital storage oscilloscope may be
used.
FIG. A1.1 Test Apparatus for Determination of Torsional Breaking
Force and Breaking Angle
A1.3.3 The torsional yield strength will be determined by
the offset method (Fig. A1.2), using the torque versus angle of
rotation curve produced in A1.3.1 and A1.3.2.
mechanism will accommodate the insertion of a threaded
A1.3.3.1 On the torque versus angle of rotation curve, locate
stopper on the other side of the test block. The threaded stopper
Point m equal to a rotation of 2°. Draw mn parallel to OA, and
will prevent the screw from being completely inserted into the
locate b, the intersection of mn with the torque versus angle of
test block and will allow the torsional strength of the screw to
rotation curve. Torque B is defined as the torsional yield
be measured. This holder will be modified according to the size
strength.
of the testing specimen so that the gage length of the specimen
A1.3.3.2 The maximum torque is determined by the largest
will be as outlined in A1.3.1.
value of torque on the torque versus angle of rotation curve.
A1.2.1.5 Recorder—The data recorder shall be suitable to
A1.3.3.3 The breaking angle is determined from the torque
continuously record torque versus angle of rotation, calibrated
versus angle plot shown in Fig. A1.3. The breaking angle is
in units of newton-meters for torque and degrees for angle of
defined as the point at which the torque portion of the curve
rotation. The value of torque shall have a resolution of 5 % of
demonstrates its most rapid descent (negative slope) to total
torsional yield strength. The angular displacement scale shall
failure. The breaking angle (B.A.) is determined as the inter-
have a minimum sensitivity so as to enable an accurate offset
section of the two tangents (D and E) shown in Fig. A1.3. Line
measurement capability for a 2° angular displacement (see
E is a tangent to the horizontal portion of the curve which
A1.3.3).
represents maximum torque. Line D is drawn at the curve’s
most rapid descent. The intersection of these two lines is the
A1.2.2 Test Specimen—The test specimen shall be a com-
breaking angle (B.A.) and is recorded to the nearest 10°.
pletely fabricated and finished bone screw.
A1.3 Procedure
A1.3.1 Torsional Yield Strength, Maximum Torque, and
Breaking Angle—Place the specimen in the holding device so
that five threads below the head of the screw are exposed
outside the holding device (for example, split collet, and so
forth). If the test specimen cannot accommodate this setup
because the screw is too small or is partially threaded, alternate
procedures may be used. For fully threaded screws that are too
small, the gage length of the specimen should represent 20 %
of the threaded portion of the test specimen. For partially
threaded screws, a large enough portion of the screw thread
should be gripped to firmly secure the screw so that it does not
rotate when under torsional load. There are no specific require-
ments on the gage length or the grip length in this case;
however, at least one full thread shall be exposed, if possible.
Since the gage length and grip length can vary for these screws,
the only requirement is that both be reported.
A1.3.2 The gage length or grip length should be kept the
same length for test screws of similar design. If a split collet
and collet holder are used, the following test method is FIG. A1.2 Typical Torque versus Angle of Rotation Curve
F543 − 23
head and shank (unthreaded portion of the screw excluding the
head) length, and type of screw point.
A1.4.1.2 Screw chemical composition.
A1.4.1.3 Surface finish.
A1.4.1.4 Gage length.
A1.4.1.5 Torsional yield strength.
A1.4.1.6 Maximum torque.
A1.4.1.7 Breaking angle.
A1.4.1.8 Torque versus angle of rotation plot.
A1.4.1.9 The size of the exposed portion of the screwdriver
(that is, the length and diameter relative to the tested screw) or
the angular deformation of the screwdriver assembly at maxi-
mum torque.
A1.4.1.10 Grip Length—Does not have to be reported for a
fully threaded screw of ASTM or ISO specification whose
FIG. A1.3 Typical Plot of Torque versus Torsion Angle
overall length is given.
A1.4.1.11 Fracture Location—The location can be specified
A1.4 Report
by listing the number of threads below the head at which the
screw fails or by measuring the distance below the head to the
A1.4.1 Report the following information for each specimen
approximate fracture point.
tested:
A1.4.1.1 Screw Identification—Reference any applicable
A1.5 Precision and Bias
ASTM or ISO specification that may apply to the specimen. If
specifications do not exist, provide head form, thread form, A1.5.1 Data establishing the precision and bias to be ex-
pected from this test method have not yet been obtained.
major and minor diameter, thread pitch, overall screw length,
A2. TEST METHOD FOR DRIVING TORQUE OF MEDICAL BONE SCREWS
A2.1 Significance and Use
A2.1.1 This test method is used to measure the torque Practices E4 over the range of angles to be encountered in the
required to drive a bone screw into a standard material. The test to an accuracy of 60.3°, in both the clockwise and
results obtained in this test method bear no direct correlation to counterclockwise rotation, shall be provided.
the insertion torque required to insert the subject bone screw in A2.2.1.3 Data Recorder—The data recorder shall be suit-
human or animal bone. This test method should be used only able to record torque versus angle of rotation continuously,
for the purpose of maintaining the uniformity of the product calibrated in units of newton-meters for torque and degrees for
tested. angle of rotation. The value of torque shall have a resolution of
10 % of the maximum measured torque. The angular displace-
A2.2 Apparatus
ment scale shall have sensitivity such that at least four
revolutions can be recorded and displayed.
A2.2.1 Testing Fixture—A suitable test fixture as shown in
Fig. A2.1 may be used for the insertion-removal torque tests. A2.2.1.4 Test Block Clamp—A clamp or holding device
shall be incorporated into the testing fixture. This clamp shall
This fixture shall incorporate the test block material that
conforms to Specification F1839, test block clamp, drill maintain the drilled pilot hole in the test block in line with the
bushing (if necessary to maintain alignment), and bushing test specimen.
support (if drill bushing is used). A2.2.1.5 Test Specimen—The test specimen shall be a
A2.2.1.1 Torque Transducer—A transducer to convert the completely fabricated, finished bone screw of sufficient length
applied torque into an electrical signal amenable to continuous to traverse the test block.
recording, calibrated over the range of torques, in both the A2.2.1.6 Test Block—The test block shall be fabricated from
clockwise and counterclockwise rotation, to be encountered in a uniform material that conforms to Specification F1839. The
the test shall be provided. choice of appropriate foam density for this test is at the
A2.2.1.2 Torsional Displacement Transducer—A transducer discretion of the user. See Section 8.6.2 of Specification F1839
to translate the angle of twist into an electrical signal amenable for additional information. To accommodate the requirements
to continuous recording, calibrated in a manner similar to of the pilot hole as described in A2.2.1.7, the smallest
F543 − 23
FIG. A2.1 Schematic of Test Apparatus for Driving Force
dimension of the test block’s surface shall be greater than 5× using the appropriate screwdriver bit, by applying a torsional
the diameter of the screw under test. The top and bottom force at a rate of 1 to 5 r/min (3 rpm is recommended) to the
surfaces shall be flat, smooth, and parallel as required to ensure
head of the specimen with the machine actuator. Values should
that the test block will be supported in the fixture with the top be reported in newton-meters. The exposed length of the
surface at an angle of 90° to the centerline of the test specimen.
screwdriver bit shall be equal to 20 mm, or less if justified (see
The test block thickness shall be not less than 1.25× the
X1.10). For fully threaded screws, 20 mm of the thread length
intended insertion depth.
shall be inserted into the test block. For fully threaded screws
A2.2.1.7 Pilot Holes in Test Block—Pilot holes shall be
with threaded lengths equal or less than 20 mm, 100 % of the
drilled in the test block for insertion of the test specimen for
threaded length of the screw shall be inserted, except by one
test specimens that require pilot holes. The drill size used shall
thread below the screw’s head, which may be left exposed. For
be that specified by the screw manufacturer for the size screw
partially threaded screws, 20 mm or 100 % of the threaded
being tested. If specified by the screw manufacturer, the
length of the screw shall be inserted into the test block. For
specified sized tap could be used to tap the pilot hole before
comparison between partially threaded screws with different
testing. The holes shall be drilled perpendicular to the top
thread lengths, they should all be inserted to the same depth.
surface of the test block. The holes shall be drilled straight and
The insertion torque shall be the maximum reading recorded
true, free of taper, bell mouth, or barrel shape. If there are
during the insertion of the specimen.
multiple holes in one test block, the pilot holes shall be spaced
A2.4.2 Removal Torque—The removal torque measurement
sufficiently far away from test block edges so that testing does
is optional. If it is conducted, it shall be measured by reversing
not deform the test block edges. Spacing should have a
minimum distance of 5× the diameter of the screw. When the the direction of rotation and recording the torque during the
test block is inserted into the test fixture (Fig. A2.1), the pilot removal of the screw from the test block. The removal torque
hole, screw, and screwdriver shall be on the same axis. shall be the maximum reading recorded during the removal of
A2.2.1.8 Screwdriver Bit—A screwdriver bit shall be used the specimen.
to insert or remove bone screws on test blocks. An off-the-shelf
A2.4.3 Axial Load for Insertion and Removal Torque
screwdriver bit may be used in lieu of a screwdriver bit that is
Measurements—An axial load of 11.5 N or less should be used
representative of the instruments indicated to be used with the
to maintain the screwdriver bit in the screw head during both
screw, only if the screwdriver bit is not a source or cause of
the insertion and removal procedures. If a larger axial load is
failure during insertion or removal of the bone screw.
applied, this load shall be recorded on the report form. This
load may be measured by any appropriate method. Torque
A2.3 Sampling
values should be reported in newton-meters.
A2.3.1 Representative random samples may be taken from
each lot or processing quantity in accordance with Practice
A2.5 Report
E122. Minimum sample size is n = 5.
A2.5.1 The report shall include the following for each
A2.4 Procedure
specimen tested. (All standards units for reporting shall be in
SI units.)
A2.4.1 Insertion Torque—Place the specimen in the test
A2.5.1.1 Screw Identification—Reference any applicable
fixture as illustrated in Fig. A2.1. Zero the load where the tip of
the screw is not in contact with the test block. Zero the ASTM or ISO standard specification that may apply to the
specimen. If specifications do not exist, provide head form,
displacement where the tip of the screw is flush with the test
surface of the block. Drive the specimen into the test block, thread form, major and minor diameter, thread pitch, overall
F543 − 23
screw length, head and shank (unthreaded portion of the screw A2.5.1.6.1 Trade name.
excluding the head) length, and type of screw point.
A2.5.1.6.2 Composition.
A2.5.1.2 Screw material.
A2.5.1.6.3 Density.
A2.5.1.3 Screw surface finish.
A2.5.1.6.4 Tensile strength.
A2.5.1.4 Insertion torque.
A2.5.1.6.5 Compression strength.
A2.5.1.4.1 Axial load applied during insertion.
A2.5.1.6.6 Shear strength.
A2.5.1.4.2 Insertion depth (may be calculated or measured).
A2.5.1.4.3 Specification of whether the pilot holes were or
A2.5.1.7 Test Machine—List relevant information about the
were not pretapped, if pretapped, specifications of the tap size,
test machine and provide the calibrated range of the load cell
tap diameter, and tap depth shall be reported.
and torque wrench used.
A2.5.1.4.4 Insertion test speed if different from specified in
A2.5.1.8 Test Environment—For example, air, room
A2.4.1.
temperature, and other relevant environment information.
A2.5.1.5 Removal torque, if applicable.
A2.5.1.9 Deviations from this test method, including de-
A2.5.1.5.1 Axial load applied during removal.
scription and rationale/justification.
A2.5.1.5.2 Removal test speed if different from specified for
insertion torque in A2.4.1.
A2.6 Precision and Bias
A2.5.1.6 Test Block Material Description—Specification
F1839 grade. For test block material that does not conform to A2.6.1 Data establishing the precision and accuracy to be
Specification F1839, provide the following information: expected from this test method have not yet been obtained.
A3. TEST METHOD FOR DETERMINING THE AXIAL PULLOUT LOAD OF MEDICAL BONE SCREWS
A3.1 Significance and Use
A3.1.1 This test method is used to measure the axial tensile
force required to fail or remove a bone screw from a defined
material. The results obtained in this test method are not
intended to predict the force required to remove the subject
bone screw from human or animal bone. This test method is
intended only to measure the uniformity of the products tested
or to compare the pullout load of different products.
A3.1.2 This test method may not be appropriate for all types
of implant applications. The user is cautioned to consider the
appropriateness of the method in view of the materials being
tested and their potential application.
A3.2 Apparatus
A3.2.1 Test Fixture—Machines used for testing the axial
pullout load of screws shall conform to the requirements of
Practices E4. A suitable test fixture as shown in Fig. A3.1 may
be used. This fixture shall incorporate the test block material
which conforms to Specification F1839. Drill bushing and
bushing support are optional. The test block clamp should have
a minimum grip span of 20 mm or five times the major FIG. A3.1 Schematic of Test Apparatus for Pullout Load
(when drill bushing is used)
diameter of the bone screw with the screw centered between
the grips, whichever length is higher.
A3.2.2 Test Block—The test block shall be fabricated from a
uniform material that conforms to Specification F1839. The
diameter of the screw from adjacent screws or the edges of the
choice of appropriate foam density for this test is at the
foam. The depth of the test block shall not be less than 1.25×
discretion of the user. See Section 8.6.2 of Specification F1839
the intended insertion depth.
for additional information. The top and bottom surfaces shall
A3.2.3 Data Recorder—The data recorder shall be suitable
be flat, smooth, and parallel as required to ensure that the test
to continuously record load versus displacement.
block will be supported in the fixture with the top surface
perpendicular to the centerline of the test specimen. Screws A3.2.4 Load Frame—Machines used for testing shall con-
inserted during testing shall be at minimum distance of 5× the form to the requirements of Practices E4. The loads used for
F543 − 23
the test method shall be within the loading range of the test A3.5 Calculation or Interpretation of Results
machine as defined in Practices E4.
A3.5.1 Axial Pullout Load—Determine the axial pullout
load (in newtons) of the test specimen from the load-
A3.2.5 Load Fixture—A suitable fixture shall be used to
displacement curve. The axial pullout load shall be the maxi-
place a tensile load on the bone screw. The load shall maintain
mum load reading recorded during the pullout of the specimen.
hold of the screw head and pull the screw perpendicular to the
block surface throughout the test, allowing the screw to
A3.6 Report
“self-align” during testing. An example of how this can be
A3.6.1 Report the following information:
achieved is to design a slot either by mimicking the plate hole
A3.6.1.1 Screw Identification—Reference any applicable
design or with a spherical recess into which the screw head can
ASTM or ISO standard specification that may apply to the
be seated directly under the applied load.
specimen. If a specification does not exist, provide head form,
thread form, helix angle, major and minor diameter, thread
A3.3 Sampling, Test Specimens, and Test Units
pitch, overall screw length, head and shank length, length of
the threaded portion of the shank for partially threaded screws,
A3.3.1 All test components shall be representative of im-
and type of screw point.
plant quality products. Minimum sample size is n = 5.
A3.6.1.2 Screw material.
A3.6.1.3 Screw surface finish.
A3.4 Procedure
A3.6.1.4 Axial pullout load (as defined in 3.1.1).
A3.4.1 Insertion of the Test Specimen—Drive the specimen
A3.6.1.5 Minimum grip span applied in the test.
into the test block, using the appropriate screwdriver bit, by
A3.6.1.6 Insertion depth.
applying a torsional force at a rate of 3 r/min to the head of the
A3.6.1.7 Minimum test block thickness applied in the test.
specimen with the machine actuator. For fully threaded screws,
A3.6.1.8 Mode of failure.
20 mm of the thread length shall be inserted into the test block.
A3.6.1.9 Test Block Material Description—Specification
For fully threaded screws with threaded lengths equal to or less
F1839 grade or density. For materials that do not conform to
than 20 mm, insert full thread length, but one thread below the Specification F1839, provide the following information and the
screw’s head may be exposed in order to allow clearance for
appropriate test methods used to determine the properties of the
the test fixture. Partially threaded bone screws shall have all test block material:
threads inserted into the standard material. The test specimen A3.6.1.9.1 Trade name,
used for insertion torque measurement (Annex A2) can also be A3.6.1.9.2 Composition,
used for pullout load measurement (Annex A3). A3.6.1.9.3 Density,
A3.6.1.9.4 Tensile strength,
A3.4.2 Axial Pullout Load of the Test Specimen—The test
A3.6.1.9.5 Compression strength, and
block and test block clamp depicted in Annex A2 shall be fixed
A3.6.1.9.6 Shear strength.
to the base of the load frame so that the longitudinal axis of the
A3.6.1.10 Test Machine—List relevant information about
screw is aligned with the direction of the applied load. The
the test machine and provide the calibrated range of the load
screw’s head shall be placed in the slot of the load fixture and
cell used.
seated in the spherical recess. The load fixture shall then be
A3.6.1.11 Test Environment—For example, air, room
attached to the load frame. A tensile load shall be applied to the
temperature, and other relevant environment information.
test specimen at a rate of 5 mm/min until the screw fails or
A3.6.1.12 Deviations from this test method, including de-
releases from the test block. Load (newtons) versus load fixture
scription and rationale/justification.
displacement (millimeters) shall be recorded on a data
A3.7 Precision and Bias
recorder, noting the maximum load applied and the mode of
failure (screw shaft, screw threads, or test block material A3.7.1 Data establishing the precision and accuracy to be
failure). expected from this test method have not yet been obtained.
F543 − 23
A4. TEST METHOD FOR DETERMINING THE SELF-TAPPING PERFORMANCE OF SELF-TAPPING MEDICAL BONE
SCREWS
A4.1 Significance and Use
A4.1.1 This test method is used to determine the axial cell should have an accuracy of 0.5 % of full-scale output and
compression load (force) required to engage the self-tapping
allow measurement resolution of 61.0 N.
feature of self-tapping medical bone screws into a standard
A4.2.3 Torque Transducer—A transducer to translate the
material. The results obtained in this test method bear no direct
applied torque into an electrical signal suitable for continuous
correlation to the axial force required to insert the subject bone
recording and calibrated over the range of torques, both in
screw into human or animal bone. This test method is used only
clockwise and counterclockwise rotation, to be encountered in
to measure the uniformity of the product tested or to compare
the test method, shall be provided. The torque transducer
the performance of different, yet similarly sized, products. This
should have an accuracy of 0.5 % of full-scale output and allow
test method is not applicable to “self-drilling” or “self-drilling/
measurement resolution of 60.10 N-m.
self-tapping” styles of medical bone screws.
NOTE A4.1—A combination compressive load and torque transducer is
A4.2 Apparatus
suitable for this application provided the transducer meets the specifica-
tions detailed in A4.2.2 and A4.2.3.
A4.2.1 Testing Apparatus—A schematic for the axial self-
tapping force test apparatus is illustrated in Fig. A4.1. The
A4.2.4 Linear Displacement Transducer—A transducer to
apparatus shall provide a variable speed motor capable of
translate the axial displacement of the test apparatus’s spindle
continuously driving a spindle. The spindle shall be capable of
into an electrical signal suitable for continuous recording and
a continuous rotation as well as axial translation to allow
calibrated over the range of displacements to be encountered in
variable force on the test specimen. The apparatus and spindle
the test method, shall be provided. The displacement trans-
shall be sufficiently rigid to neither deflect nor deform under
ducer should have an accuracy of 1 % of full scale and allow
the conditions of loading encountered during the test. The
a measurement resolution of 60.5 mm.
apparatus shall incorporate a test block clamp for the purpose
A4.2.5 Test Block Clamp—A clamp or holding device shall
of rigidly fixing a test block. The apparatus shall be capable of
be incorporated into the testing fixture. This holding device
continuously monitoring and recording the force, torque, and
shall maintain the drilled pilot hole in the test block in line with
axial displacement of the specimen. The apparatus shall be
the test specimen. The holding device shall be sufficiently rigid
calibrated for the range of forces, torques, and linear displace-
to neither deflect nor deform under the conditions of loading
ments used in the determination.
encountered during the test and yet not deform the test block
A4.2.2 Compression Load Cell—A transducer to translate
during clamping of the test block or performance of the test.
the applied axial force into an electrical signal suitable for
continuous recording and calibrated over the range of forces to A4.2.6 Test Block—The test block shall be fabricated from a
be encountered in the test method, shall be provided. The load uniform material that conforms to Specification F1839. The top
and bottom surfaces shall be flat, smooth, and parallel (within
0.4 mm) as required to ensure that the test block will be
supported in the fixture with the top surface at an angle of 90°
to the centerline of the test specimen. The edges of the test
block shall be of such contour or squareness as required to
ensure that the test block clamp shall hold the test block free of
relative motion without deformation of the test block during
clamping or testing. The test block thickness shall be not less
than 25 mm.
A4.2.7 Pilot Holes in Test Block—Pilot holes shall be drilled
in the test block for insertion and removal of the test specimen.
The drill size used shall be that specified by the screw
manufacturer for the size screw being tested. The holes shall be
drilled at 90° to the top surface of the test block. The holes
shall be
...