ISO 7206-12:2025

Implants for surgery - Partial and total hip joint prostheses - Part 12: Deformation test method for press-fit acetabular components

This document specifies a test method for determining short-term deformation of a press-fit acetabular component for total hip joint replacement under specific laboratory conditions. This document also defines the conditions of testing so that the important parameters that affect the components are taken into account and it describes how the specimen is set up for testing. The described method is intended to be used to measure the amount of deformation under load and plastic deformation after unloading of various designs and materials used for acetabular components in total hip joint replacement. These measurements are then used in an evaluation of risks associated with acetabular cup deformation for the acetabular component under evaluation to determine if its performance can be adversely affected. In the evaluation of risks associated with acetabular component deformation, it can be useful to take into consideration various design, material and surgical implantation factors (e.g. those identified in REF Section_sec_8 \r \h Clause 8 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E000000530065006300740069006F006E005F007300650063005F0038000000 ), and, if necessary, a comparison of results to a reference implant tested under the same conditions. Depending on this evaluation, either additional testing or clinical data, or both, which is outside the scope of this document, can be necessary. The loading of the acetabular components in vivo differs, in general, from the loading defined in this test method. The results obtained here cannot be used to directly predict in vivo performance. This document does not cover methods that examine the test specimens.

Implants chirurgicaux — Prothèses partielles et totales de l'articulation de la hanche — Partie 12: Méthode d’essai de déformation des composants acétabulaires sans ciment

ISO 7206-12:2016 spécifie une méthode d'essai permettant de déterminer la déformation à court-terme d'un composant acétabulaire «pressfit» pour une prothèse totale de l'articulation de la hanche dans des conditions expérimentales spécifiques. Elle définit également les conditions d'essai de manière que les paramètres importants qui influent sur les composants soient pris en compte, et décrit en outre le montage d'essai de l'éprouvette. De plus, la présente partie de l'ISO 7206 spécifie les paramètres d'essai des composants acétabulaires «pressfit» soumis à l'essai conformément à la présente partie de l'ISO 7206. La méthode décrite est destinée à être utilisée pour évaluer la comparaison des différentes conceptions et des matériaux utilisés pour les composants acétabulaires d'une prothèse totale de l'articulation de la hanche en cas d'essai dans des conditions similaires. La mise en charge des composants acétabulaires in vivo diffèrera, en règle générale, de celle définie dans la présente méthode d'essai. Les résultats obtenus ici ne peuvent pas être utilisés directement pour prédire la performance in vivo. ISO 7206-12:2016 ne traite pas des méthodes d'examen de l'éprouvette.

General Information

• Status: Published
• Publication Date: 20-Nov-2025
• ICS: 11.040.40 - Implants for surgery, prosthetics and orthotics
• Technical Committee: ISO/TC 150/SC 4 - Bone and joint replacements
• Drafting Committee: ISO/TC 150/SC 4 - Bone and joint replacements
• Current Stage: 6060 - International Standard published
• Start Date: 21-Nov-2025
• Due Date: 21-Sep-2025
• Completion Date: 21-Nov-2025

Relations

• Revises: ISO 7206-12:2016 - Implants for surgery - Partial and total hip joint prostheses - Part 12: Deformation test method for acetabular shells
• Effective Date: 01-Oct-2022

Overview

ISO 7206-12:2025 - Implants for surgery - Partial and total hip joint prostheses - Part 12 specifies a laboratory deformation test method for press‑fit acetabular components used in total hip replacement. The standard defines how to measure short‑term articulating surface deformation (under load) and plastic deformation after unloading, describes specimen setup and testing conditions, and explains how measured deformations are used in an evaluation of risks that could adversely affect implant performance.

Key topics and technical requirements

• Scope and purpose: Measures short‑term deformation of press‑fit acetabular cups and modular liners to support risk evaluation (does not set an absolute pass/fail deformation limit).
• Test principle: Apply defined laboratory loading to a seated press‑fit component and measure geometric deviations (diameter/circularity) in a specified measurement plane.
• Critical geometrical planes defined:
  • Frontal face reference plane (perpendicular to polar axis)
  • Loading plane (area contacting cortical bone)
  • Measurement plane (parallel to frontal face; sensitivity depends on distance)
• Apparatus & specimen:
  • Loading device and fixtures specified; clamping jaw material now required to have minimum hardness of 60 HRC.
  • Guidance on selecting test specimens, sample counts and testing conditions (Clause 5.2–5.3).
• Procedure highlights:
  • Defined starting rotational orientations for symmetric/asymmetric cups.
  • Minimum loading rate and a 0.2% deformation stopping criterion are included (procedure clarifications in Clause 6).
  • Separate steps for monobloc and modular components; recommendation to justify any liner materials not tested.
• Reporting & interpretation:
  • Test report requirements and examples of factors to consider when evaluating whether deformation could impact seating, locking or tribology.
  • Results are for risk evaluation and comparison (including to a reference implant tested under identical conditions); they do not directly predict in‑vivo performance.

Applications and who uses it

• Primary users: orthopedic implant manufacturers, biomechanical test laboratories, design and R&D engineers, regulatory bodies and conformity assessors.
• Practical uses:
  • Assess risk of cup deformation affecting liner seating or locking in modular systems.
  • Evaluate potential articulating surface distortion that could alter lubrication, friction and wear.
  • Support pre‑market mechanical verification, design optimization and comparison to reference implants.
  • Inform need for additional testing or clinical data during product development and regulatory submission.

Related standards

• ISO 7206‑1, ISO 7206‑2 (hip implant classification and materials)
• ISO 21534, ISO 21535 (joint replacement implant requirements)
• ISO 7500‑1 (calibration of testing machines)
• ASTM F1820 (modular acetabular device disassembly forces)

Keywords: ISO 7206-12:2025, deformation test, press-fit acetabular component, acetabular cup deformation, hip prosthesis testing, total hip joint replacement, implant manufacturers.

Standards Content (Sample)

International
Standard
ISO 7206-12
Second edition
Implants for surgery — Partial and
2025-11
total hip joint prostheses —
Part 12:
Deformation test method for press-
fit acetabular components
Implants chirurgicaux — Prothèses partielles et totales de
l'articulation de la hanche —
Partie 12: Méthode d’essai de déformation des composants
acétabulaires sans ciment
Reference number
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 3
5 Apparatus . 3
5.1 Loading device .3
5.2 Test specimen selection .6
5.3 Number of samples and testing conditions .6
6 Procedure . 6
7 Test report . 7
8 Interpretation of results . 8
Bibliography . 9

iii
Foreword
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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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 150, Implants for surgery, Subcommittee SC 4,
Bone and joint replacements.
This second edition cancels and replaces the first edition (ISO 7206-12:2016), which has been technically
revised.
The main changes are as follows:
— the third element of the title has been aligned with the scope which states that this test is for press-fit
acetabular components;
— the terminology has been aligned with ISO 21535:2023;
— the scope has been revised to clarify that the deformation measurements that are made in this test
and how these measurements are then used in an evaluation of risks associated with acetabular cup
deformation to determine if acetabular component performance can be adversely affected;
— the term “metal backing deformation” has been changed to “metal shell deformation” and the term
“spherical socket deformation” has been deleted in Clause 3;
— a requirement for the clamping jaw material to have a minimum hardness of 60 HRC has been added in 5.1;
— the requirement to test all liner articulating surface materials has been changed to a recommendation
and a requirement has been added to justify why each liner material was not tested in 5.2;
— a new subclause, “5.3 Number of samples and testing conditions”, has been added and corresponding
information has been moved to this subclause;
— in Clause 6, the starting rotational orientation for symmetric and asymmetric specimens have been
clarified and tolerances have been added to the rotational orientations where needed, a minimum
loading rate has been added, a clarification has been added regarding the 0,2 % deformation stopping
criterion, the steps for testing monobloc and modular acetabular components have been clarified and
corresponding procedure steps have been added;

iv
— in Clause 7, reporting requirements including requirements to justify the worst-case acetabular
components used during testing and the worst-case directions of loading have been added, reporting
requirements for the year of publication, any unusual observations during testing, and the date of the
test have been added, and the requirement to report stiffness of the testing setup has been removed;
— a new Clause, “8 Interpretation of results”, has been added to include examples of factors to consider
in an evaluation of risks associated with acetabular component deformation under load and plastic
deformation after unloading, and, based on the measured deformation test results, a requirement has
been added to perform an evaluation to determine whether or not implant performance can be adversely
affected.
A list of all parts in the ISO 7206 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
Introduction
Press-fit fixation is currently a common method for implanting a non-cemented acetabular component
for total hip joint replacement. In such a press-fit acetabular component, primary fixation is achieved by
[1]
an interference fit between the acetabular cup and the reamed acetabulum. The interference, diameter
difference, leads to a certain amount of pressure between bone and acetabular component that contributes
to the amount of fixation, but also causes deformation of both the bone of the acetabulum and the acetabular
component. The amount of interference is based on the design of the reamer and acetabular cup, is known
by the manufacturer and can be included in the surgical technique manual.
The anisotropic mechanical properties of the acetabular bone, with increased stiffness mainly in the regions
[2]
of ilium and ischium, and variable geometry of the acetabulum, can create the potential for inhomogeneous
deformation of the acetabular component. The local deformation of the acetabular component can be
increased in areas where the acetabular component is in contact with bone regions of increased stiffness.
Therefore, the deformed acetabular component can be oval in shape when looking onto its frontal face.
There are design features beside the cup-bone-interference and the bone stiffness that affect the
deformation of the acetabular component. These design features include, among others, the cup diameter,
wall thickness, material and anti-rotation elements on the acetabular component’s outer surface such as
[2][3][4][5]
fins and grooves. Screw holes and any kind of asymmetrically positioned cut-outs could also affect
the cup’s deformation behaviour leading to differences in the amount of deformation depending on the cup’s
rotational orientation around its polar axis under loading.
Deformation of a modular acetabular component can affect the proper seating and locking of the articulating
[3]
liner. Additionally, articulating surface deformation can affect the lubrication and friction properties.
[4][5][6]
Deformation of a monobloc acetabular cup definitely results in articulating surface deformation
[7]
potentially affecting lubrication and friction properties, potentially resulting in higher wear rates and
[ ][ ][ ]
premature failure of the prosthesis. 3 8 9 Therefore, acetabular component deformation has the potential
to affect the hip replacement’s performance.
Therefore, it is important to ensure that the deformation of an acetabular component does not significantly
affect the hip replacement’s functional properties as intraoperative assembly of components, tribology, etc.
This method addresses the short-term deformation performed under laboratory conditions. It does not give
a quantitative deformation limit as an acceptance criterion because there is no reliable data in the scientific
literature to support such a threshold today. It must be considered that the test conditions described in this
document do not exactly reproduce all the factors of the clinical situation.

vi
International Standard ISO 7206-12:2025(en)
Implants for surgery — Partial and total hip joint
prostheses —
Part 12:
Deformation test method for press-fit acetabular components
1 Scope
This document specifies a test method for determining short-term deformation of a press-fit acetabular
component for total hip joint replacement under specific laboratory conditions. This document also defines
the conditions of testing so that the important parameters that affect the components are taken into account
and it describes how the specimen is set up for testing.
The described method is intended to be used to measure the amount of deformation under load and plastic
deformation after unloading of various designs and materials used for acetabular components in total hip
joint replacement. These measurements are then used in an evaluation of risks associated with acetabular
cup deformation for the acetabular component under evaluation to determine if its performance can be
adversely affected. In the evaluation of risks associated with acetabular component deformation, it can
be useful to take into consideration various design, material and surgical implantation factors (e.g. those
identified in Clause 8), and, if necessary, a comparison of results to a reference implant tested under the
same conditions. Depending on this evaluation, either additional testing or clinical data, or both, which is
outside the scope of this document, can be necessary.
The loading of the acetabular components in vivo differs, in general, from the loading defined in this test
method. The results obtained here cannot be used to directly predict in vivo performance.
This document does not cover methods that examine the test specimens.
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 7206-1, Implants for surgery — Partial and total hip joint prostheses — Part 1: Classification and designation
of dimensions
ISO 7206-2, Implants for surgery — Partial and total hip joint prostheses — Part 2: Articulating surfaces made
of metallic, ceramic and plastics materials
ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Calibration and verification of the force-measuring system
ISO 22081, Geometrical product specifications (GPS) — Geometrical tolerancing — General geometrical
specifications and general size specifications
ISO 21534, Non-active surgical implants — Joint replacement implants — Particular requirements
ISO 21535:2023, Non-active surgical implants — Joint replacement implants — Specific requirements for hip-
joint replacement implants
ASTM F1820-22, Standard Test Method for Determining the Forces for Disassembly of Modular Acetabular Devices

3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7206-1, ISO 7206-2, ISO 21534,
ISO 21535 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
articulating surface deformation
amount of geometrical deviation (diameter and circularity of the component (cup or, if modular, liner) in a
defined measurement plane (3.4)) under loaded and unloaded conditions
3.2
frontal face reference plane
plane, perpendicular to the component polar axis, nominally at the frontal face level [see Figure 1 a)]
Note 1 to entry: In case of doubt, the polar axis can be defined as perpendicular to the plane spanning around the
contact zone of the acetabular component to the cortical bone, and as containing the centre point of the ball sphere
approximating the acetabular component’s outer sphere.
Note 2 to entry: In case of an asymmetrically shaped frontal face, e.g. anatomically shaped acetabular components,
the frontal face reference plane can be located at a level, which contains the largest part of the frontal face that is
perpendicular to the component polar axis [see Figure 1 b) and c)].
Note 3 to entry: In case that the frontal face does not contain any part perpendicular to the component axis, the frontal
face reference plane can be located at that level at the approximated middle between the highest and the lowest point
of the frontal face in distal direction [see Figure 1 d)].
a) b)
c) d)
NOTE Marked (shaded) areas of the frontal face are located in the reference plane.
Figure 1 — Frontal face reference plane of acetabular components

3.3
loading plane
plane, parallel to the frontal face reference plane (3.2) and located in an area where the acetabular cup is in
contact with the cortical bone after being properly and fully seated intraoperatively
EXAMPLE For symmetrically shaped acetabular components, Figure 1 a), the loading plane is usually located
close to the frontal face reference plane (3.2).
3.4
measurement plane
plane, parallel to the frontal face reference plane (3.2), located within a certain distance to the frontal face
reference plane (3.2) but as close as possible to the frontal face reference plane (3.2), or directly at the frontal
face when performing optical measurements on acetabular components depicted in Figure 1 a)
Note 1 to entry: The sensitivity of the deformation measurement decreases with increasing distance of the
measurement plane from the frontal face reference plane (3.2) and with decreasing distance of the measurement plane
to the spherical pole of the acetabular component.
Note 2 to entry: Within the measurement plane, the measurement points for determining the inner diameter of the
test specimen can be captured. Therefore, the measurement plane can be defined so that capturing the measurement
points is not disturbed by any design features of the test specimen as holes or cut-outs. The measurement points shall
be captured at the test specimen directly; they cannot be captured at the load frame.
Note 3 to entry: It is not always possible to take measurements on the frontal face reference plane (3.2) (e.g. because
of fixation design features). When comparing deformation of different acetabular component designs, for example as
shown in Figure 1 a) to d), the distance between the frontal face reference plane (3.2) and the measurement plane for
each acetabular component shall be identical.
3.5
metal shell deformation
amount of geometrical deviation [inner diameter and circularity of modular metal shell in a defined
measurement plane (3.4)] under loaded and unloaded conditions
4 Principle
The test specimen is subjected to diametrically opposite two-point loading. For the determination of short-
term deformation, measurements of diameter in the first of at least three loading directions in a defined
measurement plane are carried out prior to and under loading, as well as after unloading. This deformation
measurement procedure is then re
...