ASTM F1541-02(2015)

Standard Specification and Test Methods for External Skeletal Fixation Devices

SIGNIFICANCE AND USE
A1.4 Significance and Use
A1.4.1 The purpose of this classification is to establish a consistent terminology system by means of which these ESFD configurations can be classified. It is anticipated that a companion testing standard using this classification system will subsequently be developed.
SCOPE
1.1 This specification provides a characterization of the design and mechanical function of external skeletal fixation devices (ESFDs), test methods for characterization of ESFD mechanical properties, and identifies needs for further development of test methods and performance criteria. The ultimate goal is to develop a specification, which defines performance criteria and methods for measurement of performance-related mechanical characteristics of ESFDs and their fixation to bone. It is not the intention of this specification to define levels of performance or case-specific clinical performance of the devices, as insufficient knowledge is available to predict the consequences of the use of any of these devices in individual patients for specific activities of daily living. Furthermore, it is not the intention of this specification to describe or specify specific designs for ESFDs.  
1.2 This specification describes ESFDs for surgical fixation of the skeletal system. It provides basic ESFD geometrical definitions, dimensions, classification, and terminology; material specifications; performance definitions; test methods; and characteristics determined to be important to the in-vivo performance of the device.  
1.3 This specification includes a terminology and classification annex and five standard test method annexes as follows:  
1.3.1 Classification of External Fixators—Annex A1.  
1.3.2 Test Method for External Skeletal Fixator Connectors—Annex A2.  
1.3.3 Test Method for Determining In-Plane Compressive Properties of Circular Ring or Ring Segment Bridge Elements—Annex A3.  
1.3.4 Test Method for External Skeletal Fixator Joints—Annex A4.  
1.3.5 Test Method for External Skeletal Fixator Pin Anchorage Elements—Annex A5.  
1.3.6 Test Method for External Skeletal Fixator Subassemblies—Annex A6.  
1.3.7 Test Method for External Skeletal Fixator/Constructs Subassemblies—Annex A7.  
1.4 A rationale is given in Appendix X1.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 The following safety hazards caveat pertains only to the test method portions (Annex A2 – Annex A6):  
1.7 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Aug-2015
• ICS: 11.040.40 - Implants for surgery, prosthetics and orthotics
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.21 - Osteosynthesis

Relations

• Replaces: ASTM F1541-02(2011)e1 - Standard Specification and Test Methods for External Skeletal Fixation Devices
• Effective Date: 01-Sep-2015
• Replaced By: ASTM F1541-17 - Standard Specification and Test Methods for External Skeletal Fixation Devices
• Effective Date: 01-Sep-2017

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:F1541 −02 (Reapproved 2015)
Standard Specification and Test Methods for
External Skeletal Fixation Devices
This standard is issued under the fixed designation F1541; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.3.7 Test Method for External Skeletal Fixator/Constructs
Subassemblies—Annex A7.
1.1 This specification provides a characterization of the
design and mechanical function of external skeletal fixation 1.4 A rationale is given in Appendix X1.
devices (ESFDs), test methods for characterization of ESFD
1.5 The values stated in SI units are to be regarded as
mechanical properties, and identifies needs for further devel-
standard. No other units of measurement are included in this
opment of test methods and performance criteria.The ultimate
standard.
goal is to develop a specification, which defines performance
1.6 The following safety hazards caveat pertains only to the
criteria and methods for measurement of performance-related
test method portions (Annex A2 – Annex A6):
mechanicalcharacteristicsofESFDsandtheirfixationtobone.
It is not the intention of this specification to define levels of 1.7 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
performance or case-specific clinical performance of the
devices, as insufficient knowledge is available to predict the responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
consequences of the use of any of these devices in individual
patients for specific activities of daily living. Furthermore, it is bility of regulatory limitations prior to use.
not the intention of this specification to describe or specify
specific designs for ESFDs. 2. Referenced Documents
2.1 ASTM Standards:
1.2 This specification describes ESFDs for surgical fixation
of the skeletal system. It provides basic ESFD geometrical A938Test Method for Torsion Testing of Wire
D790Test Methods for Flexural Properties of Unreinforced
definitions, dimensions, classification, and terminology; mate-
rial specifications; performance definitions; test methods; and and Reinforced Plastics and Electrical Insulating Materi-
als
characteristics determined to be important to the in-vivo
performance of the device. E4Practices for Force Verification of Testing Machines
F67Specification for Unalloyed Titanium, for Surgical Im-
1.3 This specification includes a terminology and classifi-
plant Applications (UNS R50250, UNS R50400, UNS
cationannexandfivestandardtestmethodannexesasfollows:
R50550, UNS R50700)
1.3.1 Classification of External Fixators—Annex A1.
F90 Specification for Wrought Cobalt-20Chromium-
1.3.2 Test Method for External Skeletal Fixator
15Tungsten-10NickelAlloy for Surgical ImplantApplica-
Connectors—Annex A2.
tions (UNS R30605)
1.3.3 Test Method for Determining In-Plane Compressive
F136 Specification for Wrought Titanium-6Aluminum-
Properties of Circular Ring or Ring Segment Bridge
4VanadiumELI(ExtraLowInterstitial)AlloyforSurgical
Elements—Annex A3.
Implant Applications (UNS R56401)
1.3.4 Test Method for External Skeletal Fixator Joints—
F138 Specification for Wrought 18Chromium-14Nickel-
Annex A4.
2.5MolybdenumStainlessSteelBarandWireforSurgical
1.3.5 Test Method for External Skeletal Fixator Pin Anchor-
Implants (UNS S31673)
age Elements—Annex A5.
F366Specification for Fixation Pins and Wires
1.3.6 Test Method for External Skeletal Fixator
F543Specification and Test Methods for Metallic Medical
Subassemblies—Annex A6.
Bone Screws
F544Reference Chart for Pictorial Cortical Bone Screw
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 Sept. 1, 2015. Published October 2015. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
published as F1541–94. Last previous edition approved in 2011 as F1541–02 Standards volume information, refer to the standard’s Document Summary page on
ε1
(2011) . DOI: 10.1520/F1541-02R15. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1541−02 (2015)
Classification (Withdrawn 1998) 6.2.1 The sites of junction between ESFD anchorage ele-
F1058Specification for Wrought 40Cobalt-20Chromium- ments (for example, pins) and bridge elements (for example,
16Iron-15Nickel-7Molybdenum Alloy Wire and Strip for rods) normally require specialized clamping or gripping
Surgical Implant Applications (UNS R30003 and UNS members, known as connecting elements. Often, connecting
R30008) elements are subjected to high loads, especially moments, so
F1264Specification and Test Methods for Intramedullary adequacy of their intrinsic mechanical stiffness, or strength, or
Fixation Devices both, is critical to overall fixator performance. A test method
F1472 Specification for Wrought Titanium-6Aluminum- forevaluatingthemechanicalperformanceofESFDconnector
4VanadiumAlloyforSurgicalImplantApplications(UNS elements is described in Annex A2.
R56400) 6.2.2 ESFDs involving ring-type bridge elements are used
F1713 Specification for Wrought Titanium-13Niobium- widely both for fracture treatment and for distraction osteo-
13Zirconium Alloy for Surgical Implant Applications genesis. The anchorage elements in such fixators usually are
(UNS R58130) wires or thin pins, which pass transverse to the bone long axis
andwhicharetensioneddeliberatelytocontrolthelongitudinal
3. Terminology
stiffness of the fixator. Tensioning these wires or pins causes
appreciable compressive load in the plane of the ring element.
3.1 Definitions—Thedefinitionsoftermsrelatingtoexternal
A test method for evaluating the mechanical performance of
fixators are described in Annex A1.
ESFDringelementsinthisloadingmodeisdescribedinAnnex
4. Classification A3.
6.2.3 ThehighloadsoftendevelopedatESFDjunctionsites
4.1 Externalskeletalfixatorsaremodulardevicesassembled
are of concern both because of potentially excessive elastic
from component elements.
deformation and because of potential irrecoverable deforma-
4.2 Test methods can address individual elements (for
tion. In addition to the connecting element itself (Annex A2),
example,anchorageelements,bridgeelements);subassemblies
overall performance of the junction also depends on the
ofelements(forexample,connectors,joints,ringelements);or
interface between the connecting element and the anchorage,
the entire fixator.
or bridge elements, or both, which it grips. A test method for
4.3 Tests of an entire assembled fixator may include the evaluating the overall strength, or stiffness, or both, at an
externalfixatorjoint,asdefinedinAnnexA1astheconnecting
fixator alone, or alternatively, the fixator as anchored to a
representation of the bone(s) upon which it typically would be element itself plus its interface with the anchorage, or bridge,
or both, elements, which it grips, is described in Annex A4.
mounted in clinical usage.
6.2.4 The modular nature of many ESFD systems affords
5. Materials
thesurgeonparticularlygreatlatitudeastoconfigurationofthe
frame subassembly, as defined in Annex A1 as the bridge
5.1 All ESFDs made of materials that have an ASTM
elements plus the connecting elements used to join bridge
standard shall meet those requirements given in ASTM Stan-
elements, but specifically excluding the anchorage elements.
dards listed in 2.1.
Since the configuration of the frame subassembly is a major
determinant of overall ESFD mechanical behavior, it is impor-
6. Performance Considerations and Test Methods
tant to have procedures for unambiguously characterizing
6.1 Individual Components—The anchorage pins by which
frame subassemblies, both geometrically and mechanically.
anESFDisattachedtoaskeletalmemberormemberstypically
Test methodology suitable for that purpose is described in
experience high flexural, or torsional loads, or both. Often, the
Annex A6.
majority of the overall compliance of an ESFD is in its
6.3 Entire Assembled Fixator—No test methods are yet
anchorageelements.Atestmethodforevaluatingthemechani-
approved for entire assembled fixators.
cal performance of an ESFD anchorage element in either of
these loading modes is described in Annex A5.
7. Keywords
6.2 Subassemblies of Elements:
7.1 anchorageelement;bending;bridgeelement;connector;
external skeletal fixation device; fracture fixation; joints;
modularity; orthopedic medical device; osteosynthesis; ring
The last approved version of this historical standard is referenced on
www.astm.org. element; subassembly (frame); terminology; torsion
F1541−02 (2015)
ANNEXES
(Mandatory Information)
A1. CLASSIFICATION OF EXTERNAL SKELETAL FIXATORS
A1.1. Scope A1.5.1.2 The individual parts (or modules of individual
parts)fromwhichtheenduserassemblesthefixatoraretermed
A1.1.1 This classification covers the definitions of basic
its elements.
terms and considerations for external skeletal fixation devices
(ESFDs) and the mechanical analyses thereof. A1.5.2 AnESFDnormallyisconfiguredtospanamechani-
cal discontinuity in the host bone that otherwise would be
A1.1.2 It is not the intent of this classification to define
unable to transmit one or more components of the applied
levels of acceptable performance or to make recommendations
functional load successfully.This bony discontinuity is termed
concerning the appropriate or preferred clinical usage of these
the mechanical defect.
devices.
A1.5.3 Examples of mechanical defects are fracture
A1.1.3 This standard does not purport to address all of the
surfaces, interfragmentary callus, segmental bone gaps, articu-
safety concerns, if any, associated with its use. It is the
lar surfaces, neoplasms, and osteotomies.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
A1.5.4 Coordinate System(s)—The relative positions of the
bility of regulatory limitations prior to use.
bones or bone segments bordering the mechanical defect
should be described in terms of an orthogonal axis coordinate
A1.2. Referenced Documents system (Fig. A1.1).
2 A1.5.4.1 Where possible, coordinate axis directions should
A1.2.1 ASTM Standards:
be aligned perpendicular to standard anatomical planes (for
F366Specification for Fixation Pins and Wires
example,transverse(horizontaloraxial),coronal(frontal),and
F543Specification and Test Methods for Metallic Medical
sagittal (median)).
Bone Screws
A1.5.4.2 Where possible, translation directions should be
F544Reference Chart for Pictorial Cortical Bone Screw
consistent with standard clinical conventions (for example,
Classification (Withdrawn 1998)
ventral (anterior), dorsal (posterior), cranial (cephalad or
superior), caudal (inferior), lateral, or medial).
A1.3 Background
A1.5.4.3 Rotation measurement conventions must follow
A1.3.1 ESFDs are in widespread use in orthopedic surgery,
the right-hand rule and, where possible, should be consistent
primarily for applications involving fracture fixation or limb
with standard clinical terminology (for example, right or left
lengthening,orboth.Themechanicaldemandsplacedonthese
lateral bending, flexion, extension, and torsion).
devices often are severe. Clinical success usually depends on
A1.5.5 Abase coordinate system (X, Y, Z) should be affixed
suitablemechanicalintegrationoftheESFDwiththehostbone
to one of the bones or major bone segments bordering the
or limb.
mechanical defect. This bone or bone segment is termed the
A1.3.2 It is important, therefore, to have broadly accepted
base segment, S , and serves as a datum with respect to which
b
terminology and testing standards by which these devices can
pertinent motion(s) of bone segments or fixator elements, or
be described and their mechanical behaviors measured.
both, can be referenced. Depending on context, S may be
b
A1.3.3 Useful terminology and testing standards must take defined as being on either the proximal or the distal side of a
into account that the modular nature of most ESFDs deliber- mechanical defect.
ately affords a great deal of clinical latitude in configuring the
A1.5.6 The other bone(s) or bone segment(s) bordering the
assembled fixator.
mechanical defect, whose potential motion(s) with respect to
S is of interest, is termed the mobile segment(s), S.If
b m
A1.4. Significance and Use
necessary, a local right-handed orthogonal coordinate system
A1.4.1 The purpose of this classification is to establish a (x, y, z) may be embedded within the S (s).
m
consistent terminology system by means of which these ESFD
A1.5.7 Degrees of Freedom: Describing the position, or
configurations can be classified. It is anticipated that a com-
change in position, of S relative to S requires specifying one
m b
panion testing standard using this classification system will
ormoreindependentvariables.Thesevariablesshallbetermed
subsequently be developed.
positional degrees of freedom (P-DOF).
A1.5.7.1 Depending on context, this may involve as many
A1.5 Basis of Classification
as six variables (three translation and three orientation).
A1.5.1 An assembled ESFD and the bone(s) or bone ana-
A1.5.7.2 Also depending on context, P-DOFs may be used
log(s) to which it is affixed constitute a fixator-bone construct.
to describe motions of interest in various magnitude ranges.
A1.5.1.1 The assembled ESFD itself, apart from the host For example, P-DOFs may be used to describe one or more
bone, is termed the fixator assembly. components of visually imperceptible motion (for example,
F1541−02 (2015)
a spring or a cushion. Such an unlocked degree of freedom is
termed a resisted unlocked degree of freedom.
A1.5.9.2 Unlocked degrees of freedom in which motion is
induced actively by external energy input from devices asso-
ciatedwiththefixatoraretermed actuateddegreesoffreedom.
A1.5.9.3 Anunlockeddegreeoffreedominwhichmotionis
unopposed by a specific design mechanism is termed an
unresisted unlocked degree of freedom. Incidental friction in a
dynamizing element shall not be construed as representing
deliberately resisted motion; however, conditions involving
untoward resistance to motion, for example, substantial bind-
ing friction, in a supposedly unresisted degree of freedom
should be identified.
A1.5.10 For adjustment or unlocked
...

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.
´1
Designation: F1541 − 02 (Reapproved 2011) F1541 − 02 (Reapproved 2015)
Standard Specification and Test Methods for
External Skeletal Fixation Devices
This standard is issued under the fixed designation F1541; 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.
ε NOTE—Editorial changes were made throughout in July 2012.
1. Scope
1.1 This specification provides a characterization of the design and mechanical function of external skeletal fixation devices
(ESFDs), test methods for characterization of ESFD mechanical properties, and identifies needs for further development of test
methods and performance criteria. The ultimate goal is to develop a specification, which defines performance criteria and methods
for measurement of performance-related mechanical characteristics of ESFDs and their fixation to bone. It is not the intention of
this specification to define levels of performance or case-specific clinical performance of the devices, as insufficient knowledge is
available to predict the consequences of the use of any of these devices in individual patients for specific activities of daily living.
Furthermore, it is not the intention of this specification to describe or specify specific designs for ESFDs.
1.2 This specification describes ESFDs for surgical fixation of the skeletal system. It provides basic ESFD geometrical
definitions, dimensions, classification, and terminology; material specifications; performance definitions; test methods; and
characteristics determined to be important to the in-vivo performance of the device.
1.3 This specification includes a terminology and classification annex and five standard test method annexes as follows:
1.3.1 Classification of External Fixators—Annex A1.
1.3.2 Test Method for External Skeletal Fixator Connectors—Annex A2.
1.3.3 Test Method for Determining In-Plane Compressive Properties of Circular Ring or Ring Segment Bridge Elements—
Annex A3.
1.3.4 Test Method for External Skeletal Fixator Joints—Annex A4.
1.3.5 Test Method for External Skeletal Fixator Pin Anchorage Elements—Annex A5.
1.3.6 Test Method for External Skeletal Fixator Subassemblies—Annex A6.
1.3.7 Test Method for External Skeletal Fixator/Constructs Subassemblies—Annex A7.
1.4 A rationale is given in Appendix X1.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 The following safety hazards caveat pertains only to the test method portions (Annex A2 – Annex A6):
1.7 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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
A938 Test Method for Torsion Testing of Wire
D790 Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials
E4 Practices for Force Verification of Testing Machines
F67 Specification for Unalloyed Titanium, for Surgical Implant Applications (UNS R50250, UNS R50400, UNS R50550, UNS
R50700)
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 Oct. 1, 2011Sept. 1, 2015. Published October 2011October 2015. Originally published as F1541 – 94. Last previous edition approved in 20072011
ε1
as F1541 – 02 (2007)(2011) . DOI: 10.1520/F1541-02R11E01.10.1520/F1541-02R15.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. 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
F1541 − 02 (2015)
F90 Specification for Wrought Cobalt-20Chromium-15Tungsten-10Nickel Alloy for Surgical Implant Applications (UNS
R30605)
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)
F366 Specification for Fixation Pins and Wires
F543 Specification and Test Methods for Metallic Medical Bone Screws
F544 Reference Chart for Pictorial Cortical Bone Screw Classification (Withdrawn 1998)
F1058 Specification for Wrought 40Cobalt-20Chromium-16Iron-15Nickel-7Molybdenum Alloy Wire and Strip for Surgical
Implant Applications (UNS R30003 and UNS R30008)
F1264 Specification and Test Methods for Intramedullary Fixation Devices
F1472 Specification for Wrought Titanium-6Aluminum-4Vanadium Alloy for Surgical Implant Applications (UNS R56400)
F1713 Specification for Wrought Titanium-13Niobium-13Zirconium Alloy for Surgical Implant Applications (UNS R58130)
3. Terminology
3.1 Definitions—The definitions of terms relating to external fixators are described in Annex A1.
4. Classification
4.1 External skeletal fixators are modular devices assembled from component elements.
4.2 Test methods can address individual elements (for example, anchorage elements, bridge elements); subassemblies of
elements (for example, connectors, joints, ring elements); or the entire fixator.
4.3 Tests of an entire assembled fixator may include the fixator alone, or alternatively, the fixator as anchored to a representation
of the bone(s) upon which it typically would be mounted in clinical usage.
5. Materials
5.1 All ESFDs made of materials that have an ASTM standard shall meet those requirements given in ASTM Standards listed
in 2.1.
6. Performance Considerations and Test Methods
6.1 Individual Components—The anchorage pins by which an ESFD is attached to a skeletal member or members typically
experience high flexural, or torsional loads, or both. Often, the majority of the overall compliance of an ESFD is in its anchorage
elements. A test method for evaluating the mechanical performance of an ESFD anchorage element in either of these loading modes
is described in Annex A5.
6.2 Subassemblies of Elements:
6.2.1 The sites of junction between ESFD anchorage elements (for example, pins) and bridge elements (for example, rods)
normally require specialized clamping or gripping members, known as connecting elements. Often, connecting elements are
subjected to high loads, especially moments, so adequacy of their intrinsic mechanical stiffness, or strength, or both, is critical to
overall fixator performance. A test method for evaluating the mechanical performance of ESFD connector elements is described
in Annex A2.
6.2.2 ESFDs involving ring-type bridge elements are used widely both for fracture treatment and for distraction osteogenesis.
The anchorage elements in such fixators usually are wires or thin pins, which pass transverse to the bone long axis and which are
tensioned deliberately to control the longitudinal stiffness of the fixator. Tensioning these wires or pins causes appreciable
compressive load in the plane of the ring element. A test method for evaluating the mechanical performance of ESFD ring elements
in this loading mode is described in Annex A3.
6.2.3 The high loads often developed at ESFD junction sites are of concern both because of potentially excessive elastic
deformation and because of potential irrecoverable deformation. In addition to the connecting element itself (Annex A2), overall
performance of the junction also depends on the interface between the connecting element and the anchorage, or bridge elements,
or both, which it grips. A test method for evaluating the overall strength, or stiffness, or both, at an external fixator joint, as defined
in Annex A1 as the connecting element itself plus its interface with the anchorage, or bridge, or both, elements, which it grips,
is described in Annex A4.
6.2.4 The modular nature of many ESFD systems affords the surgeon particularly great latitude as to configuration of the frame
subassembly, as defined in Annex A1 as the bridge elements plus the connecting elements used to join bridge elements, but
specifically excluding the anchorage elements. Since the configuration of the frame subassembly is a major determinant of overall
The last approved version of this historical standard is referenced on www.astm.org.
F1541 − 02 (2015)
ESFD mechanical behavior, it is important to have procedures for unambiguously characterizing frame subassemblies, both
geometrically and mechanically. Test methodology suitable for that purpose is described in Annex A6.
6.3 Entire Assembled Fixator—No test methods are yet approved for entire assembled fixators.
7. Keywords
7.1 anchorage element; bending; bridge element; connector; external skeletal fixation device; fracture fixation; joints;
modularity; orthopedic medical device; osteosynthesis; ring element; subassembly (frame); terminology; torsion
ANNEXES
(Mandatory Information)
A1. CLASSIFICATION OF EXTERNAL SKELETAL FIXATORS
A1.1. Scope
A1.1.1 This classification covers the definitions of basic terms and considerations for external skeletal fixation devices (ESFDs)
and the mechanical analyses thereof.
A1.1.2 It is not the intent of this classification to define levels of acceptable performance or to make recommendations concerning
the appropriate or preferred clinical usage of these devices.
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 and health practices and determine the applicability of regulatory
limitations prior to use.
A1.2. Referenced Documents
A1.2.1 ASTM Standards:
F366 Specification for Fixation Pins and Wires
F543 Specification and Test Methods for Metallic Medical Bone Screws
F544 Reference Chart for Pictorial Cortical Bone Screw Classification (Withdrawn 1998)
A1.3 Background
A1.3.1 ESFDs are in widespread use in orthopedic surgery, primarily for applications involving fracture fixation or limb
lengthening, or both. The mechanical demands placed on these devices often are severe. Clinical success usually depends on
suitable mechanical integration of the ESFD with the host bone or limb.
A1.3.2 It is important, therefore, to have broadly accepted terminology and testing standards by which these devices can be
described and their mechanical behaviors measured.
A1.3.3 Useful terminology and testing standards must take into account that the modular nature of most ESFDs deliberately
affords a great deal of clinical latitude in configuring the assembled fixator.
A1.4. Significance and Use
A1.4.1 The purpose of this classification is to establish a consistent terminology system by means of which these ESFD
configurations can be classified. It is anticipated that a companion testing standard using this classification system will
subsequently be developed.
A1.5 Basis of Classification
A1.5.1 An assembled ESFD and the bone(s) or bone analog(s) to which it is affixed constitute a fixator-bone construct.
F1541 − 02 (2015)
A1.5.1.1 The assembled ESFD itself, apart from the host bone, is termed the fixator assembly.
A1.5.1.2 The individual parts (or modules of individual parts) from which the end user assembles the fixator are termed its
elements.
A1.5.2 An ESFD normally is configured to span a mechanical discontinuity in the host bone that otherwise would be unable to
transmit one or more components of the applied functional load successfully. This bony discontinuity is termed the mechanical
defect.
A1.5.3 Examples of mechanical defects are fracture surfaces, interfragmentary callus, segmental bone gaps, articular surfaces,
neoplasms, and osteotomies.
A1.5.4 Coordinate System(s)—The relative positions of the bones or bone segments bordering the mechanical defect should be
described in terms of an orthogonal axis coordinate system (Fig. A1.1).
A1.5.4.1 Where possible, coordinate axis directions should be aligned perpendicular to standard anatomical planes (for example,
transverse (horizontal or axial), coronal (frontal), and sagittal (median)).
S = base segment
b
S = mobile segment
m
D = mechanical defect
O = origin of base reference frame
X, Y, and Z = base reference frame axes
o = origin of mobile reference frame
x, y, and z = mobile reference frame axes
R = transverse rod
t
R = longitudinal rod
L
P = pin
C = rod-rod connector
rr
C = pin-rod connector
pr
FIG. A1.1 External Fixator Definition Schematic
F1541 − 02 (2015)
A1.5.4.2 Where possible, translation directions should be consistent with standard clinical conventions (for example, ventral
(anterior), dorsal (posterior), cranial (cephalad or superior), caudal (inferior), lateral, or medial).
A1.5.4.3 Rotation measurement conventions must follow the right-hand rule and, where possible, should be consistent with
standard clinical terminology (for example, right or left lateral bending, flexion, extension, and torsion).
A1.5.5 A base coordinate system (X,Y,Z) should be affixed to one of the bones or major bone segments bordering the mechanical
defect. This bone or bone segment is termed the base segment, S , and serves as a datum with respect to which pertinent motion(s)
b
of bone segments or fixator elements, or both, can be referenced. Depending on context, S may be defined as being on either the
b
proximal or the distal side of a mechanical defect.
A1.5.6 The other bone(s) or bone segment(s) bordering the mechanical defect, whose potential motion(s) with respect to S is of
b
interest, is termed the mobile segment(s), S . If necessary, a local right-handed orthogonal coordinate system (x,y,z) may be
m
embedded within the S (s).
m
A1.5.7 Degrees of Freedom: Describing the position, or change in position, of S relative to S requires specifying one or more
m b
independent variables. These variables shall be termed positional degrees of freedom (P-DOF).
A1.5.7.1 Depending on context, this may involv
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