ISO 7206-12:2025

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
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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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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 r
...