ISO 18192-3:2017
(Main)Implants for surgery — Wear of total intervertebral spinal disc prostheses — Part 3: Impingement-wear testing and corresponding environmental conditions for test of lumbar prostheses under adverse kinematic conditions
Implants for surgery — Wear of total intervertebral spinal disc prostheses — Part 3: Impingement-wear testing and corresponding environmental conditions for test of lumbar prostheses under adverse kinematic conditions
ISO 18192-3:2017 defines a test procedure to simulate and evaluate lumbar spinal disc prostheses wear under adverse impingement conditions.
Implants chirurgicaux — Usure des prothèses totales de remplacement des disques intervertébraux lombaires — Partie 3: Essai d'incidence d'usure et conditions environnementales correspondantes pour l'essai de prothèses lombaires sous conditions cinématiques défavorables
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INTERNATIONAL STANDARD
Deleted: TC /SC N ¶
¶
ISO/FDIS 18192‐3¶
ISO
Voting begins on:¶
2017‐02‐14¶
18192-3
Voting terminates on:¶
2017‐04‐11¶
First edition TC /SC /WG 2¶
Secretariat: ¶
¶
2017-06
Implants for surgery — Wear of total intervertebral spinal disc prostheses —
Part 3:
Impingement-wear testing and corresponding environmental conditions for test of
lumbar prostheses under adverse kinematic conditions
Implants chirurgicaux — Usure des prothèses totales de remplacement des disques
intervertébraux lombaires —
Partie 3: Essai d’incidence d’usure et conditions environnementales correspondantes
pour l’essai de prothèses lombaires sous conditions cinématiques défavorables
Document type:
Document subtype:
Document stage:
Document language:
D:\temp\macroserver\DOCX2PDFRGB\DOCX2PDFRGB.hamaoka@RHAMAOKA_97\C067605e_trackch
anges.docx
---------------------- Page: 1 ----------------------
ISO/TC 150/SC 5 N
Contents Page
Foreword . 3
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents and materials . 2
6 Apparatus . 3
7 Impingement wear testing methods . 5
7.1 General . 5
7.2 Example of development of a load and displacement profiles for extension
impingement protocol . 6
7.3 Procedure . 7
8 Test report . 8
9 Disposal of test specimen . 9
Annex A (normative) Wear of spinal disc prostheses — Gravimetric measurement method . 10
A.1 General . 10
A.2 Procedure . 10
A.2.1 Principle . 10
A.2.2 Reagents and materials . 10
A.2.3 Apparatus . 10
A.2.4 Preparation of test specimen for gravimetric measurements . 10
A.2.5 Procedure for gravimetric measurement . 11
Annex B (informative) Justification of the test method . 13
B.1 Background . 13
B.2 Clinical motivation . 13
Bibliography . 15
ii
---------------------- Page: 2 ----------------------
ISO/TC 150/SC 5 N
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national
standards bodies (ISO member bodies). The work of preparing International Standards is normally
carried out through ISO technical committees. Each member body interested in a subject for which a
technical committee has been established has the right to be represented on that committee.
International organizations, governmental and non‐governmental, in liaison with ISO, also take part in
the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all
matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 150, Implants for surgery, Subcommittee
SC 5, Osteosynthesis and spinal devices.
A list of all parts in the ISO 18192 series can be found on the ISO website.
iii
---------------------- Page: 3 ----------------------
Implants for surgery — Wear of total intervertebral spinal disc
prostheses — Part 3: Impingement-wear testing and
corresponding environmental conditions for test of lumbar
prostheses under adverse kinematic conditions
1 Scope
This document defines a test procedure to simulate and evaluate lumbar spinal disc prostheses wear
under adverse impingement conditions.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
ISO 4965‐1, Metallic materials — Dynamic force calibration for uniaxial fatigue testing — Part 1:
Testing systems
ISO 18192‐1, Implants for surgery — Wear of total intervertebral spinal disc prostheses — Part 1:
Loading and displacement parameters for wear testing and corresponding environmental conditions
for test
ISO 23788, Metallic materials — Verification of the alignment of fatigue testing machines
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18192‐1 and the following
apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
impingement
point at which two opposing components collide or restrict motion usually indicated by a sharp
change in force or moment
3.2
range of motion
ROM
amount of angular displacement that a total disk replacement prosthesis can undergo from the
device neutral position to the point at which impingement occurs around a defined global axis
1
---------------------- Page: 4 ----------------------
ISO/TC 150/SC 5 N
Note 1 to entry: If an implant impinges at 15° from the implant neutral position in flexion and 20° from the
implant neutral position in extension, the implant range of motion can be defined as +15°/‐20° in
flexion/extension.
3.3
distance between centre of rotation and point of impingement
DCI
distance between the point of impingement and the nominal centre of rotation for the flexion,
extension or lateral bending motions
3.4
axial load during impingement
ALI
axial load applied to the device in newtons while the device is in an impinged condition
3.5
point of impingement
point of contact between two opposing components that results in impingement
4 Principle
Based on current clinical evidence, lumbar spinal disc prostheses have experienced impingement in
extension/flexion, lateral bending, axial rotation and combinations thereof with extension being the
most commonly reported mode for the lumbar spine.
Adverse impingement testing conditions are determined based on available clinical data, engineering
analysis and other relevant information in the literature.
An axial load and a time‐varying angular displacement are applied to the test specimens to simulate
repeated contact between design features of the specimens.
Four possible individual impingement scenarios have been identified in the literature:
a) flexion;
b) extension;
c) lateral bending;
d) combined flexion and lateral bending.
In addition, combined axial rotation with any of the aforementioned motion modes should be
considered, if necessary to achieve a clinically relevant impingement wear scar and/or worst case
impingement scenario.
A load soak control specimen, if polymers are the object of investigation, is subjected to the same
time‐varying force to determine the creep of the test specimen and/or the amount of mass change
due to fluid transfer. The test takes place in a controlled environment simulating physiological
conditions.
5 Reagents and materials
5.1 Fluid test medium.
The fluid test medium consisting of calf serum diluted with de‐ionized water (balance) to a
concentration of 20 g ± 2 g protein/l shall be prepared according to ISO 18192‐1. If routine
2
---------------------- Page: 5 ----------------------
ISO/TC 150/SC 5 N
monitoring of the pH of the fluid test medium is undertaken, the values shall be included in the test
[1]
report [see Clause 8, m) 6)] as an increase in pH could indicate an increase in microbial activity .
5.2 Test and control specimen.
Between the inferior and superior components shall be the articulating surface of the inferior and
superior components, attached by its normal immediate backing (for example, bone cement or a
machined replica of the inner surface of the backing), unless this is impractical due to physical
features of the implant system. If the component forming the articulating surface is fixed to the
backing by a rim/snap‐fit system, the machined replica shall provide the same fixation conditions.
If it is not practical to use the normal backing or cement fixation due to physical features of the
implant system, the support system for the inferior and/or superior component should represent
normal design features and conditions of use but should allow removal of the component for
measurement of wear without destruction.
It is recommended that six specimens be tested for the impingement‐wear test. If less than six
specimens are tested, appropriate justification shall be given.
NOTE The number of specimens tested can be the subject of national legislation.
If polymers are the object of investigation, a load soak control specimen is to be subjected to the
same axial load to determine the creep of the test specimen and/or the amount of mass change due
to fluid transfer. The test should take place in a controlled environment of test medium to simulate
physiological conditions (see 5.1).
In the test cases where surrounding fluid is not absorbed by the specimens, test specimens shall be
weighed prior to testing with an instrument having a precision of 0,1 mg.
The tested implant size should be selected by an engineering analysis including theoretical,
computational, or experimental methods. If computational methods are used, experimental
verification that considers the point of impingement, the materials in contact and the range of motion
Deleted: is recommended,
of the specimens is recommended. The point of impingement and the centre of rotation of the
Deleted: .
bearing are detected in all testing directions. The combination of implant components with the
highest contact stress in the tested direction is selected for the test. If the materials in contact during
impingement change with size, then tests with different implant sizes should be considered. The
Deleted: the
number of test specimens of each size should not be less than three with no less than six test
specimens in total.
6 Apparatus
For the kinematical analysis the following testing configuration shall be applied. Deviation from this
testing configuration shall be justified.
6.1 Test machine, in accordance with ISO 4965‐1 and ISO 23788, as specified in ISO 18192‐1 for
lumbar prosthesis, and capable of associating and replacing the required corresponding angular
displacements and forces (see Clause 7) for each specific protocol of movement.
6.2 Means of mounting and enclosing the test specimen, as specified in ISO 18192‐1 for lumbar
prosthesis.
6.3 Means of aligning and positioning, as specified in ISO 18192‐1 for lumbar prosthesis.
6.4 Motion control system, capable of generating the required angular movements of the inferior
component with an accuracy of ±1° at the maxima and minima of the motion and ±5 % of cycle time
phasing. For multi‐station test systems, capabilities shall be assessed with all stations active.
3
---------------------- Page: 6 ----------------------
ISO/TC 150/SC 5 N
6.5 Force control system, capable of generating a force in the z‐direction (see Figure 1), which
varies for each specific protocol of movement, and capable of maintaining the magnitude of the
maxima and minima of this force cycle to a tolerance of ±5 % of the maximum force value for the
cycle and ±5 % of the full cycle time for phasing. For multi‐station test systems, capabilities shall be
assessed with all stations active.
6.6 Lubrication system, as specified in ISO 18192‐1 for lumbar prosthesis.
6.7 Temperature control system, as specified in ISO 18192‐1.
6.8 Control station(s), capable of applying the loading regime for specific protocol of movement
and incorporating the requirements given in 6.1, 6.2, 6.5, 6.6 and 6.7.
Deleted: 6
6.9 The origin of the fixed coordinate system of the test machine (which is consistent with the
centre of rotation of the implant) shall be the intersection of the axis for lateral bending, flexion
extension and axial rotation. The machine's former sequence shall be the Euler sequence used for
coordinate transformation. The coordinate system of the test machine shall coincide with the
Deleted: consist
coordinate system of the upper endplate. All other parts of the specimens shall move relative to this
coordinate system (see Figure 1).
The axial load vector shall be perpendicular to the flexion (Y) and lateral bending (X) axis and shall
coincide with axial rotation (Z) axis in a fixed coordinate system.
Deleted: consist
The superior endplate may translate along the Z axis and in the XY plane (to avoid shear forces). The
inferior endplate may rotate around all three axis.
The intended movement shall be applied via the inferior endplate. The load shall be applied via the
superior endplate.
4
---------------------- Page: 7 ----------------------
ISO/TC 150/SC 5 N
Key
1 flexion/extension
2 lateral/bending
3 axial rotation
Figure 1 — Coordinate system of the test machine
7 Impingement wear testing methods
7.1 General
Extension, flexion, and lateral bending impingement boundary conditions shall be analysed to
determine the worst case clinically relevant conditions to be tested. In addition, the manufacturer
should consider combining axial rotation with any of the aforementioned motion modes, if necessary
to achieve a clinically relevant impingement wear scar and worst case impingement wear or damage.
The nominal device centre of rotation in flexion, extension, lateral bending and axial rotation shall be
determined.
5
---------------------- Page: 8 ----------------------
ISO/TC 150/SC 5 N
The points of impingement in all testing directions shall to be detected and the respective
perpendicular distance between each point of impingement and the nominal centre of rotation (DCI)
determined.
The load and displacement profile shall be developed prior to running the test.
During impingement testing, the device range of motion shall be exceeded by at least 2° in the
impingement direction. In addition, the impingement region shall be offloaded completely each cycle.
The angular displacements applying flexion/extension, lateral bending and/or rotation should be
sinusoidal.
Establish the pattern of load and movement for each selected movement protocol. An example of
development of load and displacement profiles for extension impingement protocol is presented in
7.2.
7.2 Example of development of a load and displacement profiles for extension
impingement protocol
Figure 2 shows an example of an impingement load and displacement profile in extension that is
based on applying a moment of 7,5 Nm to the device during impingement. In this example, the test
starts with the device in the 0‐point position and progresses 3° in flexion. Subsequently, the motion
progresses back through the neutral position to 2° beyond the device range of motion in extension.
In this example, lateral bending and axial rotation are held at neutral.
For some bearing combination, force overshoot can be observed at the point of impingement. Force
overshoot should be minimized.
To apply a 7,5 Nm extension moment, the horizontal distance between the centre of the device and
DCI should be measured. The ALI necessary to apply the 7,5 Nm impingement motion mode moment
during impingement shall be determined by dividing 7,5 Nm by the DCI, expressed in metres (m).
NOTE 1 The extension moment value is justified in Reference [2].
Figure 2 — Example of load and displacement profile for a lumbar spine extension
impingement wear test
6
---------------------- Page: 9 ----------------------
ISO/TC 150/SC 5 N
The loading conditions for this example are as follows:
a) sinusoidal axial loading is used except for the impingement loading interval;
b) a minimum axial load of 300 N is used to engage the sample at the neutral position;
...
INTERNATIONAL ISO
STANDARD 18192-3
First edition
2017-06
Implants for surgery — Wear of
total intervertebral spinal disc
prostheses —
Part 3:
Impingement-wear testing and
corresponding environmental
conditions for test of lumbar
prostheses under adverse kinematic
conditions
Implants chirurgicaux — Usure des prothèses totales de
remplacement des disques intervertébraux lombaires —
Partie 3: Essai d’incidence d’usure et conditions environnementales
correspondantes pour l’essai de prothèses lombaires sous conditions
cinématiques défavorables
Reference number
ISO 18192-3:2017(E)
©
ISO 2017
---------------------- Page: 1 ----------------------
ISO 18192-3:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
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Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 18192-3:2017(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents and materials . 2
6 Apparatus . 3
7 Impingement wear testing methods . 5
7.1 General . 5
7.2 Example of development of load and displacement profiles for extension
impingement protocol . 6
7.3 Procedure . 7
8 Test report . 8
9 Disposal of test specimen . 9
Annex A (normative) Wear of spinal disc prostheses — Gravimetric measurement method .10
Annex B (informative) Justification of the test method .13
Bibliography .15
© ISO 2017 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 18192-3:2017(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 150, Implants for surgery, Subcommittee
SC 5, Osteosynthesis and spinal devices.
A list of all parts in the ISO 18192 series can be found on the ISO website.
iv © ISO 2017 – All rights reserved
---------------------- Page: 4 ----------------------
INTERNATIONAL STANDARD ISO 18192-3:2017(E)
Implants for surgery — Wear of total intervertebral spinal
disc prostheses —
Part 3:
Impingement-wear testing and corresponding
environmental conditions for test of lumbar prostheses
under adverse kinematic conditions
1 Scope
This document defines a test procedure to simulate and evaluate lumbar spinal disc prostheses wear
under adverse impingement conditions.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 4965-1, Metallic materials — Dynamic force calibration for uniaxial fatigue testing — Part 1:
Testing systems
ISO 18192-1, Implants for surgery — Wear of total intervertebral spinal disc prostheses — Part 1: Loading
and displacement parameters for wear testing and corresponding environmental conditions for test
ISO 23788, Metallic materials — Verification of the alignment of fatigue testing machines
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18192-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1
impingement
point at which two opposing components collide or restrict motion usually indicated by a sharp change
in force or moment
3.2
range of motion
ROM
amount of angular displacement that a total disk replacement prosthesis can undergo from the device
neutral position to the point at which impingement occurs around a defined global axis
Note 1 to entry: If an implant impinges at 15° from the implant neutral position in flexion and 20° from the implant
neutral position in extension, the implant range of motion can be defined as +15°/-20° in flexion/extension.
© ISO 2017 – All rights reserved 1
---------------------- Page: 5 ----------------------
ISO 18192-3:2017(E)
3.3
distance between centre of rotation and point of impingement
DCI
distance between the point of impingement and the nominal centre of rotation for the flexion, extension
or lateral bending motions
3.4
axial load during impingement
ALI
axial load applied to the device in newtons while the device is in an impinged condition
3.5
point of impingement
point of contact between two opposing components that results in impingement
4 Principle
Based on current clinical evidence, lumbar spinal disc prostheses have experienced impingement in
extension/flexion, lateral bending, axial rotation and combinations thereof with extension being the
most commonly reported mode for the lumbar spine.
Adverse impingement testing conditions are determined based on available clinical data, engineering
analysis and other relevant information in the literature.
An axial load and a time-varying angular displacement are applied to the test specimens to simulate
repeated contact between design features of the specimens.
Four possible individual impingement scenarios have been identified in the literature:
a) flexion;
b) extension;
c) lateral bending;
d) combined flexion and lateral bending.
In addition, combined axial rotation with any of the aforementioned motion modes should be considered,
if necessary to achieve a clinically relevant impingement wear scar and/or worst case impingement
scenario.
A load soak control specimen, if polymers are the object of investigation, is subjected to the same time-
varying force to determine the creep of the test specimen and/or the amount of mass change due to
fluid transfer. The test takes place in a controlled environment simulating physiological conditions.
5 Reagents and materials
5.1 Fluid test medium.
The fluid test medium consisting of calf serum diluted with de-ionized water (balance) to a concentration
of 20 g ± 2 g protein/l shall be prepared according to ISO 18192-1. If routine monitoring of the pH of the
fluid test medium is undertaken, the values shall be included in the test report [see Clause 8, m) 6)] as
[1]
an increase in pH could indicate an increase in microbial activity .
5.2 Test and control specimen.
Between the inferior and superior components shall be the articulating surface of the inferior and
superior components, attached by its normal immediate backing (for example, bone cement or a
machined replica of the inner surface of the backing), unless this is impractical due to physical features
2 © ISO 2017 – All rights reserved
---------------------- Page: 6 ----------------------
ISO 18192-3:2017(E)
of the implant system. If the component forming the articulating surface is fixed to the backing by a
rim/snap-fit system, the machined replica shall provide the same fixation conditions.
If it is not practical to use the normal backing or cement fixation due to physical features of the implant
system, the support system for the inferior and/or superior component should represent normal design
features and conditions of use but should allow removal of the component for measurement of wear
without destruction.
It is recommended that six specimens be tested for the impingement-wear test. If less than six specimens
are tested, appropriate justification shall be given.
NOTE The number of specimens tested can be the subject of national legislation.
If polymers are the object of investigation, a load soak control specimen is to be subjected to the same
axial load to determine the creep of the test specimen and/or the amount of mass change due to fluid
transfer. The test should take place in a controlled environment of test medium to simulate physiological
conditions (see 5.1).
In the test cases where surrounding fluid is not absorbed by the specimens, test specimens shall be
weighed prior to testing with an instrument having a precision of 0,1 mg.
The tested implant size should be selected by an engineering analysis including theoretical,
computational, or experimental methods. If computational methods are used, experimental verification
that considers the point of impingement, the materials in contact and the range of motion of the
specimens is recommended. The point of impingement and the centre of rotation of the bearing are
detected in all testing directions. The combination of implant components with the highest contact
stress in the tested direction is selected for the test. If the materials in contact during impingement
change with size, then tests with different implant sizes should be considered. The number of test
specimens of each size should not be less than three with no less than six test specimens in total.
6 Apparatus
For the kinematical analysis the following testing configuration shall be applied. Deviation from this
testing configuration shall be justified.
6.1 Test machine, in accordance with ISO 4965-1 and ISO 23788, as specified in ISO 18192-1 for
lumbar prosthesis, and capable of associating and replacing the required corresponding angular
displacements and forces (see Clause 7) for each specific protocol of movement.
6.2 Means of mounting and enclosing the test specimen, as specified in ISO 18192-1 for lumbar
prosthesis.
6.3 Means of aligning and positioning, as specified in ISO 18192-1 for lumbar prosthesis.
6.4 Motion control system, capable of generating the required angular movements of the inferior
component with an accuracy of ±1° at the maxima and minima of the motion and ±5 % of cycle time
phasing. For multi-station test systems, capabilities shall be assessed with all stations active.
6.5 Force control system, capable of generating a force in the z-direction (see Figure 1), which varies for
each specific protocol of movement, and capable of maintaining the magnitude of the maxima and minima
of this force cycle to a tolerance of ±5 % of the maximum force value for the cycle and ±5 % of the full cycle
time for phasing. For multi-station test systems, capabilities shall be assessed with all stations active.
6.6 Lubrication system, as specified in ISO 18192-1 for lumbar prosthesis.
6.7 Temperature control system, as specified in ISO 18192-1.
© ISO 2017 – All rights reserved 3
---------------------- Page: 7 ----------------------
ISO 18192-3:2017(E)
6.8 Control station(s), capable of applying the loading regime for specific protocol of movement and
incorporating the requirements given in 6.1, 6.2, 6.5, 6.6 and 6.7.
6.9 The origin of the fixed coordinate system of the test machine (which is consistent with the
centre of rotation of the implant) shall be the intersection of the axis for lateral bending, flexion extension
and axial rotation. The machine’s former sequence shall be the Euler sequence used for coordinate
transformation. The coordinate system of the test machine shall coincide with the coordinate system of
the upper endplate. All other parts of the specimens shall move relative to this coordinate system (see
Figure 1).
The axial load vector shall be perpendicular to the flexion (Y) and lateral bending (X) axis and shall
coincide with axial rotation (Z) axis in a fixed coordinate system.
The superior endplate may translate along the Z axis and in the XY plane (to avoid shear forces). The
inferior endplate may rotate around all three axis.
The intended movement shall be applied via the inferior endplate. The load shall be applied via the
superior endplate.
4 © ISO 2017 – All rights reserved
---------------------- Page: 8 ----------------------
ISO 18192-3:2017(E)
Key
1 flexion/extension
2 lateral/bending
3 axial rotation
Figure 1 — Coordinate system of the test machine
7 Impingement wear testing methods
7.1 General
Extension, flexion, and lateral bending impingement boundary conditions shall be analysed to
determine the worst case clinically relevant conditions to be tested. In addition, the manufacturer
should consider combining axial rotation with any of the aforementioned motion modes, if necessary to
achieve a clinically relevant impingement wear scar and worst case impingement wear or damage.
The nominal device centre of rotation in flexion, extension, lateral bending and axial rotation shall be
determined.
© ISO 2017 – All rights reserved 5
---------------------- Page: 9 ----------------------
ISO 18192-3:2017(E)
The points of impingement in all testing directions shall be detected and the respective perpendicular
distance between each point of impingement and the nominal centre of rotation (DCI) determined.
The load and displacement profile shall be developed prior to running the test.
During impingement testing, the device range of motion shall be exceeded by at least 2° in the
impingement direction. In addition, the impingement region shall be offloaded completely each cycle.
The angular displacements applying flexion/extension, lateral bending and/or rotation should be
sinusoidal.
Establish the pattern of load and movement for each selected movement protocol. An example of
development of load and displacement profiles for extension impingement protocol is presented in 7.2.
7.2 Example of development of load and displacement profiles for extension
impingement protocol
Figure 2 shows an example of an impingement load and displacement profile in extension that is based
on applying a moment of 7,5 Nm to the device during impingement. In this example, the test starts with
the device in the 0-point position and progresses 3° in flexion. Subsequently, the motion progresses
back through the neutral position to 2° beyond the device range of motion in extension. In this example,
lateral bending and axial rotation are held at neutral.
For some bearing combination, force overshoot can be observed at the point of impingement. Force
overshoot should be minimized.
To apply a 7,5 Nm extension moment, the horizontal distance between the centre of the device and DCI
should be measured. The ALI necessary to apply the 7,5 Nm impingement motion mode moment during
impingement shall be determined by dividing 7,5 Nm by the DCI, expressed in metres (m).
NOTE 1 The extension moment value is justified in Reference [2].
Figure 2 — Example of load and displacement profile for a lumbar spine extension impingement
wear test
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ISO 18192-3:2017(E)
The loading conditions for this example are as follows:
a) sinusoidal axial loading is used except for the impingement loading interval;
b) a mini
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